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Gene Therapy Net – News, Conferences, Vectors, Literature …

Posted on: 22 March 2018, source: GizmodoOn Tuesday, a 13-year-old boy from New Jersey was at the center of medical history as he became the first person in the US to receive an FDA-approved gene therapy for an inherited disease. The event marks the beginning of a new era of medicine, one in which devastating genetic conditions that we are born with can be simply edited out of our DNA with the help of modern biomedical technologies. The therapy, Luxturna, from Spark Therepeutics, was approved by the FDA in December to treat a rare, inherited form of blindness. Its price tag, set at $850,000or $425,000 per eyemade it the most expensive drug in the US and sparked mass sticker-shock. But the therapy, which in high-profile clinical trials has allowed patients to see the stars for the first times, also offered the almost miraculous possibility of giving sight to the blind.

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Gene Therapy Net – News, Conferences, Vectors, Literature …

Gene Therapy – Sumanas, Inc.

Gene Therapy

A few years ago, a clinical trial began in France in the hope of curing children with a type of genetic immune deficiency called SCID-X1. Children with this disease have a defective gene, called gamma-c, which prevents a subset of the cells of the immune system from forming, and predisposes the children to life-threatening infections. In an attempt to cure the childrenwho would otherwise die at a young agephysicians used gene therapy to provide them with normal gamma-c genes.

This particular trial has had striking success as well as tragedy. Eight of the eleven children are currently thriving. However, in two cases the therapy successfully introduced gamma-c genes, but these children have since developed leukemia. In both children, a gamma-c gene inserted next to another gene, called LMO2. The LMO2 gene has previously been linked to leukemia, and scientists speculate that the insertion of the gamma-c gene next to LMO2 may have overstimulated the gene, causing T cells to proliferate in excess. An LMO2 effect, in combination with the proliferation-inducing effects of the gamma-c gene itself, may be the cause of the leukemia in these two patients. Scientists are still investigating other possible causes.

From this single trial, it is clear that gene therapy holds significant promise, yet it is also clear that it poses significant risks. To learn more about the application of gene therapy in SCID, view the accompanying animation.

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Gene Therapy – Sumanas, Inc.

Gene Therapy Net – News, Conferences, Vectors, Literature …

Posted on: 22 March 2018, source: GizmodoOn Tuesday, a 13-year-old boy from New Jersey was at the center of medical history as he became the first person in the US to receive an FDA-approved gene therapy for an inherited disease. The event marks the beginning of a new era of medicine, one in which devastating genetic conditions that we are born with can be simply edited out of our DNA with the help of modern biomedical technologies. The therapy, Luxturna, from Spark Therepeutics, was approved by the FDA in December to treat a rare, inherited form of blindness. Its price tag, set at $850,000or $425,000 per eyemade it the most expensive drug in the US and sparked mass sticker-shock. But the therapy, which in high-profile clinical trials has allowed patients to see the stars for the first times, also offered the almost miraculous possibility of giving sight to the blind.

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Gene Therapy Net – News, Conferences, Vectors, Literature …

Gene therapy – Wikipedia

In the medicine field, gene therapy (also called human gene transfer) is the therapeutic delivery of nucleic acid into a patient’s cells as a drug to treat disease.[1][2] The first attempt at modifying human DNA was performed in 1980 by Martin Cline, but the first successful nuclear gene transfer in humans, approved by the National Institutes of Health, was performed in May 1989.[3] The first therapeutic use of gene transfer as well as the first direct insertion of human DNA into the nuclear genome was performed by French Anderson in a trial starting in September 1990.

Between 1989 and February 2016, over 2,300 clinical trials had been conducted, more than half of them in phase I.[4]

Not all medical procedures that introduce alterations to a patient’s genetic makeup can be considered gene therapy. Bone marrow transplantation and organ transplants in general have been found to introduce foreign DNA into patients.[5] Gene therapy is defined by the precision of the procedure and the intention of direct therapeutic effects.

Gene therapy was conceptualized in 1972, by authors who urged caution before commencing human gene therapy studies.

The first attempt, an unsuccessful one, at gene therapy (as well as the first case of medical transfer of foreign genes into humans not counting organ transplantation) was performed by Martin Cline on 10 July 1980.[6][7] Cline claimed that one of the genes in his patients was active six months later, though he never published this data or had it verified[8] and even if he is correct, it’s unlikely it produced any significant beneficial effects treating beta-thalassemia.

After extensive research on animals throughout the 1980s and a 1989 bacterial gene tagging trial on humans, the first gene therapy widely accepted as a success was demonstrated in a trial that started on 14 September 1990, when Ashi DeSilva was treated for ADA-SCID.[9]

The first somatic treatment that produced a permanent genetic change was performed in 1993.[citation needed]

Gene therapy is a way to fix a genetic problem at its source. The polymers are either translated into proteins, interfere with target gene expression, or possibly correct genetic mutations.

The most common form uses DNA that encodes a functional, therapeutic gene to replace a mutated gene. The polymer molecule is packaged within a “vector”, which carries the molecule inside cells.

Early clinical failures led to dismissals of gene therapy. Clinical successes since 2006 regained researchers’ attention, although as of 2014, it was still largely an experimental technique.[10] These include treatment of retinal diseases Leber’s congenital amaurosis[11][12][13][14] and choroideremia,[15] X-linked SCID,[16] ADA-SCID,[17][18] adrenoleukodystrophy,[19] chronic lymphocytic leukemia (CLL),[20] acute lymphocytic leukemia (ALL),[21] multiple myeloma,[22] haemophilia,[18] and Parkinson’s disease.[23] Between 2013 and April 2014, US companies invested over $600 million in the field.[24]

The first commercial gene therapy, Gendicine, was approved in China in 2003 for the treatment of certain cancers.[25] In 2011 Neovasculgen was registered in Russia as the first-in-class gene-therapy drug for treatment of peripheral artery disease, including critical limb ischemia.[26] In 2012 Glybera, a treatment for a rare inherited disorder, became the first treatment to be approved for clinical use in either Europe or the United States after its endorsement by the European Commission.[10][27]

Following early advances in genetic engineering of bacteria, cells, and small animals, scientists started considering how to apply it to medicine. Two main approaches were considered replacing or disrupting defective genes.[28] Scientists focused on diseases caused by single-gene defects, such as cystic fibrosis, haemophilia, muscular dystrophy, thalassemia, and sickle cell anemia. Glybera treats one such disease, caused by a defect in lipoprotein lipase.[27]

DNA must be administered, reach the damaged cells, enter the cell and either express or disrupt a protein.[29] Multiple delivery techniques have been explored. The initial approach incorporated DNA into an engineered virus to deliver the DNA into a chromosome.[30][31] Naked DNA approaches have also been explored, especially in the context of vaccine development.[32]

Generally, efforts focused on administering a gene that causes a needed protein to be expressed. More recently, increased understanding of nuclease function has led to more direct DNA editing, using techniques such as zinc finger nucleases and CRISPR. The vector incorporates genes into chromosomes. The expressed nucleases then knock out and replace genes in the chromosome. As of 2014 these approaches involve removing cells from patients, editing a chromosome and returning the transformed cells to patients.[33]

Gene editing is a potential approach to alter the human genome to treat genetic diseases,[34] viral diseases,[35] and cancer.[36] As of 2016 these approaches were still years from being medicine.[37][38]

Gene therapy may be classified into two types:

In somatic cell gene therapy (SCGT), the therapeutic genes are transferred into any cell other than a gamete, germ cell, gametocyte, or undifferentiated stem cell. Any such modifications affect the individual patient only, and are not inherited by offspring. Somatic gene therapy represents mainstream basic and clinical research, in which therapeutic DNA (either integrated in the genome or as an external episome or plasmid) is used to treat disease.

Over 600 clinical trials utilizing SCGT are underway in the US. Most focus on severe genetic disorders, including immunodeficiencies, haemophilia, thalassaemia, and cystic fibrosis. Such single gene disorders are good candidates for somatic cell therapy. The complete correction of a genetic disorder or the replacement of multiple genes is not yet possible. Only a few of the trials are in the advanced stages.[39]

In germline gene therapy (GGT), germ cells (sperm or egg cells) are modified by the introduction of functional genes into their genomes. Modifying a germ cell causes all the organism’s cells to contain the modified gene. The change is therefore heritable and passed on to later generations. Australia, Canada, Germany, Israel, Switzerland, and the Netherlands[40] prohibit GGT for application in human beings, for technical and ethical reasons, including insufficient knowledge about possible risks to future generations[40] and higher risks versus SCGT.[41] The US has no federal controls specifically addressing human genetic modification (beyond FDA regulations for therapies in general).[40][42][43][44]

The delivery of DNA into cells can be accomplished by multiple methods. The two major classes are recombinant viruses (sometimes called biological nanoparticles or viral vectors) and naked DNA or DNA complexes (non-viral methods).

In order to replicate, viruses introduce their genetic material into the host cell, tricking the host’s cellular machinery into using it as blueprints for viral proteins. Retroviruses go a stage further by having their genetic material copied into the genome of the host cell. Scientists exploit this by substituting a virus’s genetic material with therapeutic DNA. (The term ‘DNA’ may be an oversimplification, as some viruses contain RNA, and gene therapy could take this form as well.) A number of viruses have been used for human gene therapy, including retroviruses, adenoviruses, herpes simplex, vaccinia, and adeno-associated virus.[4] Like the genetic material (DNA or RNA) in viruses, therapeutic DNA can be designed to simply serve as a temporary blueprint that is degraded naturally or (at least theoretically) to enter the host’s genome, becoming a permanent part of the host’s DNA in infected cells.

Non-viral methods present certain advantages over viral methods, such as large scale production and low host immunogenicity. However, non-viral methods initially produced lower levels of transfection and gene expression, and thus lower therapeutic efficacy. Later technology remedied this deficiency[citation needed].

Methods for non-viral gene therapy include the injection of naked DNA, electroporation, the gene gun, sonoporation, magnetofection, the use of oligonucleotides, lipoplexes, dendrimers, and inorganic nanoparticles.

Some of the unsolved problems include:

Three patients’ deaths have been reported in gene therapy trials, putting the field under close scrutiny. The first was that of Jesse Gelsinger in 1999. Jesse Gelsinger died because of immune rejection response.[51] One X-SCID patient died of leukemia in 2003.[9] In 2007, a rheumatoid arthritis patient died from an infection; the subsequent investigation concluded that the death was not related to gene therapy.[52]

In 1972 Friedmann and Roblin authored a paper in Science titled “Gene therapy for human genetic disease?”[53] Rogers (1970) was cited for proposing that exogenous good DNA be used to replace the defective DNA in those who suffer from genetic defects.[54]

In 1984 a retrovirus vector system was designed that could efficiently insert foreign genes into mammalian chromosomes.[55]

The first approved gene therapy clinical research in the US took place on 14 September 1990, at the National Institutes of Health (NIH), under the direction of William French Anderson.[56] Four-year-old Ashanti DeSilva received treatment for a genetic defect that left her with ADA-SCID, a severe immune system deficiency. The defective gene of the patient’s blood cells was replaced by the functional variant. Ashantis immune system was partially restored by the therapy. Production of the missing enzyme was temporarily stimulated, but the new cells with functional genes were not generated. She led a normal life only with the regular injections performed every two months. The effects were successful, but temporary.[57]

Cancer gene therapy was introduced in 1992/93 (Trojan et al. 1993).[58] The treatment of glioblastoma multiforme, the malignant brain tumor whose outcome is always fatal, was done using a vector expressing antisense IGF-I RNA (clinical trial approved by NIH protocolno.1602 November 24, 1993,[59] and by the FDA in 1994). This therapy also represents the beginning of cancer immunogene therapy, a treatment which proves to be effective due to the anti-tumor mechanism of IGF-I antisense, which is related to strong immune and apoptotic phenomena.

In 1992 Claudio Bordignon, working at the Vita-Salute San Raffaele University, performed the first gene therapy procedure using hematopoietic stem cells as vectors to deliver genes intended to correct hereditary diseases.[60] In 2002 this work led to the publication of the first successful gene therapy treatment for adenosine deaminase deficiency (ADA-SCID). The success of a multi-center trial for treating children with SCID (severe combined immune deficiency or “bubble boy” disease) from 2000 and 2002, was questioned when two of the ten children treated at the trial’s Paris center developed a leukemia-like condition. Clinical trials were halted temporarily in 2002, but resumed after regulatory review of the protocol in the US, the United Kingdom, France, Italy, and Germany.[61]

In 1993 Andrew Gobea was born with SCID following prenatal genetic screening. Blood was removed from his mother’s placenta and umbilical cord immediately after birth, to acquire stem cells. The allele that codes for adenosine deaminase (ADA) was obtained and inserted into a retrovirus. Retroviruses and stem cells were mixed, after which the viruses inserted the gene into the stem cell chromosomes. Stem cells containing the working ADA gene were injected into Andrew’s blood. Injections of the ADA enzyme were also given weekly. For four years T cells (white blood cells), produced by stem cells, made ADA enzymes using the ADA gene. After four years more treatment was needed.[62]

Jesse Gelsinger’s death in 1999 impeded gene therapy research in the US.[63][64] As a result, the FDA suspended several clinical trials pending the reevaluation of ethical and procedural practices.[65]

The modified cancer gene therapy strategy of antisense IGF-I RNA (NIH n 1602)[59] using antisense / triple helix anti-IGF-I approach was registered in 2002 by Wiley gene therapy clinical trial – n 635 and 636. The approach has shown promising results in the treatment of six different malignant tumors: glioblastoma, cancers of liver, colon, prostate, uterus, and ovary (Collaborative NATO Science Programme on Gene Therapy USA, France, Poland n LST 980517 conducted by J. Trojan) (Trojan et al., 2012). This anti-gene antisense/triple helix therapy has proven to be efficient, due to the mechanism stopping simultaneously IGF-I expression on translation and transcription levels, strengthening anti-tumor immune and apoptotic phenomena.

Sickle-cell disease can be treated in mice.[66] The mice which have essentially the same defect that causes human cases used a viral vector to induce production of fetal hemoglobin (HbF), which normally ceases to be produced shortly after birth. In humans, the use of hydroxyurea to stimulate the production of HbF temporarily alleviates sickle cell symptoms. The researchers demonstrated this treatment to be a more permanent means to increase therapeutic HbF production.[67]

A new gene therapy approach repaired errors in messenger RNA derived from defective genes. This technique has the potential to treat thalassaemia, cystic fibrosis and some cancers.[68]

Researchers created liposomes 25 nanometers across that can carry therapeutic DNA through pores in the nuclear membrane.[69]

In 2003 a research team inserted genes into the brain for the first time. They used liposomes coated in a polymer called polyethylene glycol, which, unlike viral vectors, are small enough to cross the bloodbrain barrier.[70]

Short pieces of double-stranded RNA (short, interfering RNAs or siRNAs) are used by cells to degrade RNA of a particular sequence. If a siRNA is designed to match the RNA copied from a faulty gene, then the abnormal protein product of that gene will not be produced.[71]

Gendicine is a cancer gene therapy that delivers the tumor suppressor gene p53 using an engineered adenovirus. In 2003, it was approved in China for the treatment of head and neck squamous cell carcinoma.[25]

In March researchers announced the successful use of gene therapy to treat two adult patients for X-linked chronic granulomatous disease, a disease which affects myeloid cells and damages the immune system. The study is the first to show that gene therapy can treat the myeloid system.[72]

In May a team reported a way to prevent the immune system from rejecting a newly delivered gene.[73] Similar to organ transplantation, gene therapy has been plagued by this problem. The immune system normally recognizes the new gene as foreign and rejects the cells carrying it. The research utilized a newly uncovered network of genes regulated by molecules known as microRNAs. This natural function selectively obscured their therapeutic gene in immune system cells and protected it from discovery. Mice infected with the gene containing an immune-cell microRNA target sequence did not reject the gene.

In August scientists successfully treated metastatic melanoma in two patients using killer T cells genetically retargeted to attack the cancer cells.[74]

In November researchers reported on the use of VRX496, a gene-based immunotherapy for the treatment of HIV that uses a lentiviral vector to deliver an antisense gene against the HIV envelope. In a phase I clinical trial, five subjects with chronic HIV infection who had failed to respond to at least two antiretroviral regimens were treated. A single intravenous infusion of autologous CD4 T cells genetically modified with VRX496 was well tolerated. All patients had stable or decreased viral load; four of the five patients had stable or increased CD4 T cell counts. All five patients had stable or increased immune response to HIV antigens and other pathogens. This was the first evaluation of a lentiviral vector administered in a US human clinical trial.[75][76]

In May researchers announced the first gene therapy trial for inherited retinal disease. The first operation was carried out on a 23-year-old British male, Robert Johnson, in early 2007.[77]

Leber’s congenital amaurosis is an inherited blinding disease caused by mutations in the RPE65 gene. The results of a small clinical trial in children were published in April.[11] Delivery of recombinant adeno-associated virus (AAV) carrying RPE65 yielded positive results. In May two more groups reported positive results in independent clinical trials using gene therapy to treat the condition. In all three clinical trials, patients recovered functional vision without apparent side-effects.[11][12][13][14]

In September researchers were able to give trichromatic vision to squirrel monkeys.[78] In November 2009, researchers halted a fatal genetic disorder called adrenoleukodystrophy in two children using a lentivirus vector to deliver a functioning version of ABCD1, the gene that is mutated in the disorder.[79]

An April paper reported that gene therapy addressed achromatopsia (color blindness) in dogs by targeting cone photoreceptors. Cone function and day vision were restored for at least 33 months in two young specimens. The therapy was less efficient for older dogs.[80]

In September it was announced that an 18-year-old male patient in France with beta-thalassemia major had been successfully treated.[81] Beta-thalassemia major is an inherited blood disease in which beta haemoglobin is missing and patients are dependent on regular lifelong blood transfusions.[82] The technique used a lentiviral vector to transduce the human -globin gene into purified blood and marrow cells obtained from the patient in June 2007.[83] The patient’s haemoglobin levels were stable at 9 to 10 g/dL. About a third of the hemoglobin contained the form introduced by the viral vector and blood transfusions were not needed.[83][84] Further clinical trials were planned.[85] Bone marrow transplants are the only cure for thalassemia, but 75% of patients do not find a matching donor.[84]

Cancer immunogene therapy using modified antigene, antisense/triple helix approach was introduced in South America in 2010/11 in La Sabana University, Bogota (Ethical Committee 14 December 2010, no P-004-10). Considering the ethical aspect of gene diagnostic and gene therapy targeting IGF-I, the IGF-I expressing tumors i.e. lung and epidermis cancers were treated (Trojan et al. 2016).[86][87]

In 2007 and 2008, a man (Timothy Ray Brown) was cured of HIV by repeated hematopoietic stem cell transplantation (see also allogeneic stem cell transplantation, allogeneic bone marrow transplantation, allotransplantation) with double-delta-32 mutation which disables the CCR5 receptor. This cure was accepted by the medical community in 2011.[88] It required complete ablation of existing bone marrow, which is very debilitating.

In August two of three subjects of a pilot study were confirmed to have been cured from chronic lymphocytic leukemia (CLL). The therapy used genetically modified T cells to attack cells that expressed the CD19 protein to fight the disease.[20] In 2013, the researchers announced that 26 of 59 patients had achieved complete remission and the original patient had remained tumor-free.[89]

Human HGF plasmid DNA therapy of cardiomyocytes is being examined as a potential treatment for coronary artery disease as well as treatment for the damage that occurs to the heart after myocardial infarction.[90][91]

In 2011 Neovasculgen was registered in Russia as the first-in-class gene-therapy drug for treatment of peripheral artery disease, including critical limb ischemia; it delivers the gene encoding for VEGF.[92][26] Neovasculogen is a plasmid encoding the CMV promoter and the 165 amino acid form of VEGF.[93][94]

The FDA approved Phase 1 clinical trials on thalassemia major patients in the US for 10 participants in July.[95] The study was expected to continue until 2015.[85]

In July 2012, the European Medicines Agency recommended approval of a gene therapy treatment for the first time in either Europe or the United States. The treatment used Alipogene tiparvovec (Glybera) to compensate for lipoprotein lipase deficiency, which can cause severe pancreatitis.[96] The recommendation was endorsed by the European Commission in November 2012[10][27][97][98] and commercial rollout began in late 2014.[99] Alipogene tiparvovec was expected to cost around $1.6 million per treatment in 2012,[100] revised to $1 million in 2015,[101] making it the most expensive medicine in the world at the time.[102] As of 2016, only one person had been treated with drug.[103]

In December 2012, it was reported that 10 of 13 patients with multiple myeloma were in remission “or very close to it” three months after being injected with a treatment involving genetically engineered T cells to target proteins NY-ESO-1 and LAGE-1, which exist only on cancerous myeloma cells.[22]

In March researchers reported that three of five adult subjects who had acute lymphocytic leukemia (ALL) had been in remission for five months to two years after being treated with genetically modified T cells which attacked cells with CD19 genes on their surface, i.e. all B-cells, cancerous or not. The researchers believed that the patients’ immune systems would make normal T-cells and B-cells after a couple of months. They were also given bone marrow. One patient relapsed and died and one died of a blood clot unrelated to the disease.[21]

Following encouraging Phase 1 trials, in April, researchers announced they were starting Phase 2 clinical trials (called CUPID2 and SERCA-LVAD) on 250 patients[104] at several hospitals to combat heart disease. The therapy was designed to increase the levels of SERCA2, a protein in heart muscles, improving muscle function.[105] The FDA granted this a Breakthrough Therapy Designation to accelerate the trial and approval process.[106] In 2016 it was reported that no improvement was found from the CUPID 2 trial.[107]

In July researchers reported promising results for six children with two severe hereditary diseases had been treated with a partially deactivated lentivirus to replace a faulty gene and after 732 months. Three of the children had metachromatic leukodystrophy, which causes children to lose cognitive and motor skills.[108] The other children had Wiskott-Aldrich syndrome, which leaves them to open to infection, autoimmune diseases, and cancer.[109] Follow up trials with gene therapy on another six children with Wiskott-Aldrich syndrome were also reported as promising.[110][111]

In October researchers reported that two children born with adenosine deaminase severe combined immunodeficiency disease (ADA-SCID) had been treated with genetically engineered stem cells 18 months previously and that their immune systems were showing signs of full recovery. Another three children were making progress.[18] In 2014 a further 18 children with ADA-SCID were cured by gene therapy.[112] ADA-SCID children have no functioning immune system and are sometimes known as “bubble children.”[18]

Also in October researchers reported that they had treated six hemophilia sufferers in early 2011 using an adeno-associated virus. Over two years later all six were producing clotting factor.[18][113]

In January researchers reported that six choroideremia patients had been treated with adeno-associated virus with a copy of REP1. Over a six-month to two-year period all had improved their sight.[114][115] By 2016, 32 patients had been treated with positive results and researchers were hopeful the treatment would be long-lasting.[15] Choroideremia is an inherited genetic eye disease with no approved treatment, leading to loss of sight.

In March researchers reported that 12 HIV patients had been treated since 2009 in a trial with a genetically engineered virus with a rare mutation (CCR5 deficiency) known to protect against HIV with promising results.[116][117]

Clinical trials of gene therapy for sickle cell disease were started in 2014.[118][119] There is a need for high quality randomised controlled trials assessing the risks and benefits involved with gene therapy for people with sickle cell disease.[120]

In February LentiGlobin BB305, a gene therapy treatment undergoing clinical trials for treatment of beta thalassemia gained FDA “breakthrough” status after several patients were able to forgo the frequent blood transfusions usually required to treat the disease.[121]

In March researchers delivered a recombinant gene encoding a broadly neutralizing antibody into monkeys infected with simian HIV; the monkeys’ cells produced the antibody, which cleared them of HIV. The technique is named immunoprophylaxis by gene transfer (IGT). Animal tests for antibodies to ebola, malaria, influenza, and hepatitis were underway.[122][123]

In March, scientists, including an inventor of CRISPR, Jennifer Doudna, urged a worldwide moratorium on germline gene therapy, writing “scientists should avoid even attempting, in lax jurisdictions, germline genome modification for clinical application in humans” until the full implications “are discussed among scientific and governmental organizations”.[124][125][126][127]

In October, researchers announced that they had treated a baby girl, Layla Richards, with an experimental treatment using donor T-cells genetically engineered using TALEN to attack cancer cells. One year after the treatment she was still free of her cancer (a highly aggressive form of acute lymphoblastic leukaemia [ALL]).[128] Children with highly aggressive ALL normally have a very poor prognosis and Layla’s disease had been regarded as terminal before the treatment.[129]

In December, scientists of major world academies called for a moratorium on inheritable human genome edits, including those related to CRISPR-Cas9 technologies[130] but that basic research including embryo gene editing should continue.[131]

In April the Committee for Medicinal Products for Human Use of the European Medicines Agency endorsed a gene therapy treatment called Strimvelis[132][133] and the European Commission approved it in June.[134] This treats children born with adenosine deaminase deficiency and who have no functioning immune system. This was the second gene therapy treatment to be approved in Europe.[135]

In October, Chinese scientists reported they had started a trial to genetically modify T-cells from 10 adult patients with lung cancer and reinject the modified T-cells back into their bodies to attack the cancer cells. The T-cells had the PD-1 protein (which stops or slows the immune response) removed using CRISPR-Cas9.[136][137]

A 2016 Cochrane systematic review looking at data from four trials on topical cystic fibrosis transmembrane conductance regulator (CFTR) gene therapy does not support its clinical use as a mist inhaled into the lungs to treat cystic fibrosis patients with lung infections. One of the four trials did find weak evidence that liposome-based CFTR gene transfer therapy may lead to a small respiratory improvement for people with CF. This weak evidence is not enough to make a clinical recommendation for routine CFTR gene therapy.[138]

In February Kite Pharma announced results from a clinical trial of CAR-T cells in around a hundred people with advanced Non-Hodgkin lymphoma.[139]

In March, French scientists reported on clinical research of gene therapy to treat sickle-cell disease.[140]

In August, the FDA approved tisagenlecleucel for acute lymphoblastic leukemia.[141] Tisagenlecleucel is an adoptive cell transfer therapy for B-cell acute lymphoblastic leukemia; T cells from a person with cancer are removed, genetically engineered to make a specific T-cell receptor (a chimeric T cell receptor, or “CAR-T”) that reacts to the cancer, and are administered back to the person. The T cells are engineered to target a protein called CD19 that is common on B cells. This is the first form of gene therapy to be approved in the United States. In October, a similar therapy called axicabtagene ciloleucel was approved for non-Hodgkin lymphoma.[142]

In December the results of using an adeno-associated virus with blood clotting factor VIII to treat nine haemophilia A patients were published. Six of the seven patients on the high dose regime increased the level of the blood clotting VIII to normal levels. The low and medium dose regimes had no effect on the patient’s blood clotting levels.[143][144]

In December, the FDA approved Luxturna, the first in vivo gene therapy, for the treatment of blindness due to Leber’s congenital amaurosis.[145] The price of this treatment was 850,000 US dollars for both eyes.[146][147] CRISPR gene editing technology has also been used on mice to treat deafness due to the DFNA36 mutation, which also affects humans.[148]

Speculated uses for gene therapy include:

Gene Therapy techniques have the potential to provide alternative treatments for those with infertility. Recently, successful experimentation on mice has proven that fertility can be restored by using the gene therapy method, CRISPR.[149] Spermatogenical stem cells from another organism were transplanted into the testes of an infertile male mouse. The stem cells re-established spermatogenesis and fertility.[150]

Athletes might adopt gene therapy technologies to improve their performance.[151] Gene doping is not known to occur, but multiple gene therapies may have such effects. Kayser et al. argue that gene doping could level the playing field if all athletes receive equal access. Critics claim that any therapeutic intervention for non-therapeutic/enhancement purposes compromises the ethical foundations of medicine and sports.[152]

Genetic engineering could be used to cure diseases, but also to change physical appearance, metabolism, and even improve physical capabilities and mental faculties such as memory and intelligence. Ethical claims about germline engineering include beliefs that every fetus has a right to remain genetically unmodified, that parents hold the right to genetically modify their offspring, and that every child has the right to be born free of preventable diseases.[153][154][155] For parents, genetic engineering could be seen as another child enhancement technique to add to diet, exercise, education, training, cosmetics, and plastic surgery.[156][157] Another theorist claims that moral concerns limit but do not prohibit germline engineering.[158]

Possible regulatory schemes include a complete ban, provision to everyone, or professional self-regulation. The American Medical Associations Council on Ethical and Judicial Affairs stated that “genetic interventions to enhance traits should be considered permissible only in severely restricted situations: (1) clear and meaningful benefits to the fetus or child; (2) no trade-off with other characteristics or traits; and (3) equal access to the genetic technology, irrespective of income or other socioeconomic characteristics.”[159]

As early in the history of biotechnology as 1990, there have been scientists opposed to attempts to modify the human germline using these new tools,[160] and such concerns have continued as technology progressed.[161][162] With the advent of new techniques like CRISPR, in March 2015 a group of scientists urged a worldwide moratorium on clinical use of gene editing technologies to edit the human genome in a way that can be inherited.[124][125][126][127] In April 2015, researchers sparked controversy when they reported results of basic research to edit the DNA of non-viable human embryos using CRISPR.[149][163] A committee of the American National Academy of Sciences and National Academy of Medicine gave qualified support to human genome editing in 2017[164][165] once answers have been found to safety and efficiency problems “but only for serious conditions under stringent oversight.”[166]

Regulations covering genetic modification are part of general guidelines about human-involved biomedical research. There are no international treaties which are legally binding in this area, but there are recommendations for national laws from various bodies.

The Helsinki Declaration (Ethical Principles for Medical Research Involving Human Subjects) was amended by the World Medical Association’s General Assembly in 2008. This document provides principles physicians and researchers must consider when involving humans as research subjects. The Statement on Gene Therapy Research initiated by the Human Genome Organization (HUGO) in 2001 provides a legal baseline for all countries. HUGOs document emphasizes human freedom and adherence to human rights, and offers recommendations for somatic gene therapy, including the importance of recognizing public concerns about such research.[167]

No federal legislation lays out protocols or restrictions about human genetic engineering. This subject is governed by overlapping regulations from local and federal agencies, including the Department of Health and Human Services, the FDA and NIH’s Recombinant DNA Advisory Committee. Researchers seeking federal funds for an investigational new drug application, (commonly the case for somatic human genetic engineering,) must obey international and federal guidelines for the protection of human subjects.[168]

NIH serves as the main gene therapy regulator for federally funded research. Privately funded research is advised to follow these regulations. NIH provides funding for research that develops or enhances genetic engineering techniques and to evaluate the ethics and quality in current research. The NIH maintains a mandatory registry of human genetic engineering research protocols that includes all federally funded projects.

An NIH advisory committee published a set of guidelines on gene manipulation.[169] The guidelines discuss lab safety as well as human test subjects and various experimental types that involve genetic changes. Several sections specifically pertain to human genetic engineering, including Section III-C-1. This section describes required review processes and other aspects when seeking approval to begin clinical research involving genetic transfer into a human patient.[170] The protocol for a gene therapy clinical trial must be approved by the NIH’s Recombinant DNA Advisory Committee prior to any clinical trial beginning; this is different from any other kind of clinical trial.[169]

As with other kinds of drugs, the FDA regulates the quality and safety of gene therapy products and supervises how these products are used clinically. Therapeutic alteration of the human genome falls under the same regulatory requirements as any other medical treatment. Research involving human subjects, such as clinical trials, must be reviewed and approved by the FDA and an Institutional Review Board.[171][172]

Gene therapy is the basis for the plotline of the film I Am Legend[173] and the TV show Will Gene Therapy Change the Human Race?.[174] In 1994, gene therapy was a plot element in The Erlenmeyer Flask, The X-Files’ first season finale. It is also used in Stargate as a means of allowing humans to use Ancient technology.[175]

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Gene therapy – Wikipedia

Gene Therapy Retrovirus Vectors Explained

A retrovirus is any virus belonging to the viral family Retroviridae. All The genetic material in retroviruses is in the form of RNA molecules, while the genetic material of their hosts is in the form of DNA. When a retrovirus infects a host cell, it will introduce its RNA together with some enzymes into the cell. This RNA molecule from the retrovirus must produce a DNA copy from its RNA molecule before it can be considered part of the genetic material of the host cell. Retrovirus genomes commonly contain these three open reading frames that encode for proteins that can be found in the mature virus. Group-specific antigen (gag) codes for core and structural proteins of the virus, polymerase (pol) codes for reverse transcriptase, protease and integrase, and envelope (env) codes for the retroviral coat proteins (see figure 1). Figure 1. Genome organisation of retroviruses.

The process of producing a DNA copy from an RNA molecule is termed reverse transcription. It is carried out by one of the enzymes carried in the virus, called reverse transcriptase. After this DNA copy is produced and is free in the nucleus of the host cell, it must be incorporated into the genome of the host cell. That is, it must be inserted into the large DNA molecules in the cell (the chromosomes). This process is done by another enzyme carried in the virus called integrase (see figure 2).

Now that the genetic material of the virus is incorporated and has become part of the genetic material of the host cell, we can say that the host cell is now modified to contain a new gene. If this host cell divides later, its descendants will all contain the new genes. Sometimes the genes of the retrovirus do not express their information immediately.

Retroviral vectors are created by removal op the retroviral gag, pol, and env genes. These are replaced by the therapeutic gene. In order to produce vector particles a packaging cell is essential. Packaging cell lines provide all the viral proteins required for capsid production and the virion maturation of the vector. These packaging cell lines have been made so that they contain the gag, pol and env genes. Early packaging cell lines contained replication competent retroviral genomes and a single recombination event between this genome and the retroviral DNA vector could result in the production of a wild type virus. Following insertion of the desired gene into in the retroviral DNA vector, and maintainance of the proper packaging cell line, it is now a simple matter to prepare retroviral vectors (see figure 3).

One of the problems of gene therapy using retroviruses is that the integrase enzyme can insert the genetic material of the virus in any arbitrary position in the genome of the host. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted (insertional mutagenesis). If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur. This problem has recently begun to be addressed by utilizing zinc finger nucleases or by including certain sequences such as the beta-globin locus control region to direct the site of integration to specific chromosomal sites.

Gene therapy trials to treat severe combined immunodeficiency (SCID) were halted or restricted in the USA when leukemia was reported in three of eleven patients treated in the French X-linked SCID (X-SCID) gene therapy trial. Ten X-SCID patients treated in England have not presented leukemia to date and have had similar success in immune reconstitution. Gene therapy trials to treat SCID due to deficiency of the Adenosine Deaminase (ADA) enzyme continue with relative success in the USA, Italy and Japan.

As a reaction to the adverse events in the French X-SCID gene therapy trial, the Recombinant DNA Advisory Committee (RAC) sent a letter to Principal Investigators Conveying RAC Recommendations in 2003. In addition, the RAC published conclusions and recommendations of the RAC Gene Transfer Safety Symposium in 2005. A joint working party of the Gene Therapy Advisory Committee and the Committee on Safety of Medicines (CSM) in the UK lead to the publication of an updated recommendations of the GTAC/CSM working party on retroviruses in 2005.

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Gene Therapy Retrovirus Vectors Explained

Gene therapy – Mayo Clinic

Overview

Gene therapy involves altering the genes inside your body’s cells in an effort to treat or stop disease.

Genes contain your DNA the code that controls much of your body’s form and function, from making you grow taller to regulating your body systems. Genes that don’t work properly can cause disease.

Gene therapy replaces a faulty gene or adds a new gene in an attempt to cure disease or improve your body’s ability to fight disease. Gene therapy holds promise for treating a wide range of diseases, such as cancer, cystic fibrosis, heart disease, diabetes, hemophilia and AIDS.

Researchers are still studying how and when to use gene therapy. Currently, in the United States, gene therapy is available only as part of a clinical trial.

Gene therapy is used to correct defective genes in order to cure a disease or help your body better fight disease.

Researchers are investigating several ways to do this, including:

Gene therapy has some potential risks. A gene can’t easily be inserted directly into your cells. Rather, it usually has to be delivered using a carrier, called a vector.

The most common gene therapy vectors are viruses because they can recognize certain cells and carry genetic material into the cells’ genes. Researchers remove the original disease-causing genes from the viruses, replacing them with the genes needed to stop disease.

This technique presents the following risks:

The gene therapy clinical trials underway in the U.S. are closely monitored by the Food and Drug Administration and the National Institutes of Health to ensure that patient safety issues are a top priority during research.

Currently, the only way for you to receive gene therapy is to participate in a clinical trial. Clinical trials are research studies that help doctors determine whether a gene therapy approach is safe for people. They also help doctors understand the effects of gene therapy on the body.

Your specific procedure will depend on the disease you have and the type of gene therapy being used.

For example, in one type of gene therapy:

Viruses aren’t the only vectors that can be used to carry altered genes into your body’s cells. Other vectors being studied in clinical trials include:

The possibilities of gene therapy hold much promise. Clinical trials of gene therapy in people have shown some success in treating certain diseases, such as:

But several significant barriers stand in the way of gene therapy becoming a reliable form of treatment, including:

Gene therapy continues to be a very important and active area of research aimed at developing new, effective treatments for a variety of diseases.

Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this disease.

Dec. 29, 2017

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Gene therapy – Mayo Clinic

Gene Therapy | Pfizer: One of the world’s premier …

Gene therapy is a technology aimed at correcting or fixing a gene that may be defective. This exciting and potentially transformative area of research is focused on the development of potential treatments for monogenic diseases, or diseases that are caused by a defect in one gene.

The technology involves the introduction of genetic material (DNA or RNA) into the body, often through delivering a corrected copy of a gene to a patients cells to compensate for a defective one, using a viral vector.

The technology involves the introduction of genetic material (DNA or RNA) into the body, often through delivering a corrected copy of a gene to a patients cells to compensate for a defective one, using a viral vector.

Viral vectors can be developed using adeno-associated virus (AAV), a naturally occurring virus which has been adapted for gene therapy use. Its ability to deliver genetic material to a wide range of tissues makes AAV vectors useful for transferring therapeutic genes into target cells. Gene therapy research holds tremendous promise in leading to the possible development of highly-specialized, potentially one-time delivery treatments for patients suffering from rare, monogenic diseases.

Pfizer aims to build an industry-leading gene therapy platform with a strategy focused on establishing a transformational portfolio through in-house capabilities, and enhancing those capabilities through strategic collaborations, as well as potential licensing and M&A activities.

We’re working to access the most effective vector designs available to build a robust clinical stage portfolio, and employing a scalable manufacturing approach, proprietary cell lines and sophisticated analytics to support clinical development.

In addition, we’re collaborating with some of the foremost experts in this field, through collaborations with Spark Therapeutics, Inc., on a potentially transformative gene therapy treatment for hemophilia B, which received Breakthrough Therapy designation from the US Food and Drug Administration, and 4D Molecular Therapeutics to discover and develop targeted next-generation AAV vectors for cardiac disease.

Gene therapy holds the promise of bringing true disease modification for patients suffering from devastating diseases, a promise were working to seeing become a reality in the years to come.

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Gene Therapy | Pfizer: One of the world’s premier …

Gene Therapy – Sumanas, Inc.

Gene Therapy

A few years ago, a clinical trial began in France in the hope of curing children with a type of genetic immune deficiency called SCID-X1. Children with this disease have a defective gene, called gamma-c, which prevents a subset of the cells of the immune system from forming, and predisposes the children to life-threatening infections. In an attempt to cure the childrenwho would otherwise die at a young agephysicians used gene therapy to provide them with normal gamma-c genes.

This particular trial has had striking success as well as tragedy. Eight of the eleven children are currently thriving. However, in two cases the therapy successfully introduced gamma-c genes, but these children have since developed leukemia. In both children, a gamma-c gene inserted next to another gene, called LMO2. The LMO2 gene has previously been linked to leukemia, and scientists speculate that the insertion of the gamma-c gene next to LMO2 may have overstimulated the gene, causing T cells to proliferate in excess. An LMO2 effect, in combination with the proliferation-inducing effects of the gamma-c gene itself, may be the cause of the leukemia in these two patients. Scientists are still investigating other possible causes.

From this single trial, it is clear that gene therapy holds significant promise, yet it is also clear that it poses significant risks. To learn more about the application of gene therapy in SCID, view the accompanying animation.

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Gene Therapy – Sumanas, Inc.

Gene therapy – Wikipedia

In the medicine field, gene therapy (also called human gene transfer) is the therapeutic delivery of nucleic acid into a patient’s cells as a drug to treat disease.[1][2] The first attempt at modifying human DNA was performed in 1980 by Martin Cline, but the first successful nuclear gene transfer in humans, approved by the National Institutes of Health, was performed in May 1989.[3] The first therapeutic use of gene transfer as well as the first direct insertion of human DNA into the nuclear genome was performed by French Anderson in a trial starting in September 1990.

Between 1989 and February 2016, over 2,300 clinical trials had been conducted, more than half of them in phase I.[4]

Not all medical procedures that introduce alterations to a patient’s genetic makeup can be considered gene therapy. Bone marrow transplantation and organ transplants in general have been found to introduce foreign DNA into patients.[5] Gene therapy is defined by the precision of the procedure and the intention of direct therapeutic effects.

Gene therapy was conceptualized in 1972, by authors who urged caution before commencing human gene therapy studies.

The first attempt, an unsuccessful one, at gene therapy (as well as the first case of medical transfer of foreign genes into humans not counting organ transplantation) was performed by Martin Cline on 10 July 1980.[6][7] Cline claimed that one of the genes in his patients was active six months later, though he never published this data or had it verified[8] and even if he is correct, it’s unlikely it produced any significant beneficial effects treating beta-thalassemia.

After extensive research on animals throughout the 1980s and a 1989 bacterial gene tagging trial on humans, the first gene therapy widely accepted as a success was demonstrated in a trial that started on 14 September 1990, when Ashi DeSilva was treated for ADA-SCID.[9]

The first somatic treatment that produced a permanent genetic change was performed in 1993.[citation needed]

Gene therapy is a way to fix a genetic problem at its source. The polymers are either translated into proteins, interfere with target gene expression, or possibly correct genetic mutations.

The most common form uses DNA that encodes a functional, therapeutic gene to replace a mutated gene. The polymer molecule is packaged within a “vector”, which carries the molecule inside cells.

Early clinical failures led to dismissals of gene therapy. Clinical successes since 2006 regained researchers’ attention, although as of 2014, it was still largely an experimental technique.[10] These include treatment of retinal diseases Leber’s congenital amaurosis[11][12][13][14] and choroideremia,[15] X-linked SCID,[16] ADA-SCID,[17][18] adrenoleukodystrophy,[19] chronic lymphocytic leukemia (CLL),[20] acute lymphocytic leukemia (ALL),[21] multiple myeloma,[22] haemophilia,[18] and Parkinson’s disease.[23] Between 2013 and April 2014, US companies invested over $600 million in the field.[24]

The first commercial gene therapy, Gendicine, was approved in China in 2003 for the treatment of certain cancers.[25] In 2011 Neovasculgen was registered in Russia as the first-in-class gene-therapy drug for treatment of peripheral artery disease, including critical limb ischemia.[26] In 2012 Glybera, a treatment for a rare inherited disorder, became the first treatment to be approved for clinical use in either Europe or the United States after its endorsement by the European Commission.[10][27]

Following early advances in genetic engineering of bacteria, cells, and small animals, scientists started considering how to apply it to medicine. Two main approaches were considered replacing or disrupting defective genes.[28] Scientists focused on diseases caused by single-gene defects, such as cystic fibrosis, haemophilia, muscular dystrophy, thalassemia, and sickle cell anemia. Glybera treats one such disease, caused by a defect in lipoprotein lipase.[27]

DNA must be administered, reach the damaged cells, enter the cell and either express or disrupt a protein.[29] Multiple delivery techniques have been explored. The initial approach incorporated DNA into an engineered virus to deliver the DNA into a chromosome.[30][31] Naked DNA approaches have also been explored, especially in the context of vaccine development.[32]

Generally, efforts focused on administering a gene that causes a needed protein to be expressed. More recently, increased understanding of nuclease function has led to more direct DNA editing, using techniques such as zinc finger nucleases and CRISPR. The vector incorporates genes into chromosomes. The expressed nucleases then knock out and replace genes in the chromosome. As of 2014 these approaches involve removing cells from patients, editing a chromosome and returning the transformed cells to patients.[33]

Gene editing is a potential approach to alter the human genome to treat genetic diseases,[34] viral diseases,[35] and cancer.[36] As of 2016 these approaches were still years from being medicine.[37][38]

Gene therapy may be classified into two types:

In somatic cell gene therapy (SCGT), the therapeutic genes are transferred into any cell other than a gamete, germ cell, gametocyte, or undifferentiated stem cell. Any such modifications affect the individual patient only, and are not inherited by offspring. Somatic gene therapy represents mainstream basic and clinical research, in which therapeutic DNA (either integrated in the genome or as an external episome or plasmid) is used to treat disease.

Over 600 clinical trials utilizing SCGT are underway in the US. Most focus on severe genetic disorders, including immunodeficiencies, haemophilia, thalassaemia, and cystic fibrosis. Such single gene disorders are good candidates for somatic cell therapy. The complete correction of a genetic disorder or the replacement of multiple genes is not yet possible. Only a few of the trials are in the advanced stages.[39]

In germline gene therapy (GGT), germ cells (sperm or egg cells) are modified by the introduction of functional genes into their genomes. Modifying a germ cell causes all the organism’s cells to contain the modified gene. The change is therefore heritable and passed on to later generations. Australia, Canada, Germany, Israel, Switzerland, and the Netherlands[40] prohibit GGT for application in human beings, for technical and ethical reasons, including insufficient knowledge about possible risks to future generations[40] and higher risks versus SCGT.[41] The US has no federal controls specifically addressing human genetic modification (beyond FDA regulations for therapies in general).[40][42][43][44]

The delivery of DNA into cells can be accomplished by multiple methods. The two major classes are recombinant viruses (sometimes called biological nanoparticles or viral vectors) and naked DNA or DNA complexes (non-viral methods).

In order to replicate, viruses introduce their genetic material into the host cell, tricking the host’s cellular machinery into using it as blueprints for viral proteins. Retroviruses go a stage further by having their genetic material copied into the genome of the host cell. Scientists exploit this by substituting a virus’s genetic material with therapeutic DNA. (The term ‘DNA’ may be an oversimplification, as some viruses contain RNA, and gene therapy could take this form as well.) A number of viruses have been used for human gene therapy, including retroviruses, adenoviruses, herpes simplex, vaccinia, and adeno-associated virus.[4] Like the genetic material (DNA or RNA) in viruses, therapeutic DNA can be designed to simply serve as a temporary blueprint that is degraded naturally or (at least theoretically) to enter the host’s genome, becoming a permanent part of the host’s DNA in infected cells.

Non-viral methods present certain advantages over viral methods, such as large scale production and low host immunogenicity. However, non-viral methods initially produced lower levels of transfection and gene expression, and thus lower therapeutic efficacy. Later technology remedied this deficiency[citation needed].

Methods for non-viral gene therapy include the injection of naked DNA, electroporation, the gene gun, sonoporation, magnetofection, the use of oligonucleotides, lipoplexes, dendrimers, and inorganic nanoparticles.

Some of the unsolved problems include:

Three patients’ deaths have been reported in gene therapy trials, putting the field under close scrutiny. The first was that of Jesse Gelsinger in 1999. Jesse Gelsinger died because of immune rejection response.[51] One X-SCID patient died of leukemia in 2003.[9] In 2007, a rheumatoid arthritis patient died from an infection; the subsequent investigation concluded that the death was not related to gene therapy.[52]

In 1972 Friedmann and Roblin authored a paper in Science titled “Gene therapy for human genetic disease?”[53] Rogers (1970) was cited for proposing that exogenous good DNA be used to replace the defective DNA in those who suffer from genetic defects.[54]

In 1984 a retrovirus vector system was designed that could efficiently insert foreign genes into mammalian chromosomes.[55]

The first approved gene therapy clinical research in the US took place on 14 September 1990, at the National Institutes of Health (NIH), under the direction of William French Anderson.[56] Four-year-old Ashanti DeSilva received treatment for a genetic defect that left her with ADA-SCID, a severe immune system deficiency. The defective gene of the patient’s blood cells was replaced by the functional variant. Ashantis immune system was partially restored by the therapy. Production of the missing enzyme was temporarily stimulated, but the new cells with functional genes were not generated. She led a normal life only with the regular injections performed every two months. The effects were successful, but temporary.[57]

Cancer gene therapy was introduced in 1992/93 (Trojan et al. 1993).[58] The treatment of glioblastoma multiforme, the malignant brain tumor whose outcome is always fatal, was done using a vector expressing antisense IGF-I RNA (clinical trial approved by NIH protocolno.1602 November 24, 1993,[59] and by the FDA in 1994). This therapy also represents the beginning of cancer immunogene therapy, a treatment which proves to be effective due to the anti-tumor mechanism of IGF-I antisense, which is related to strong immune and apoptotic phenomena.

In 1992 Claudio Bordignon, working at the Vita-Salute San Raffaele University, performed the first gene therapy procedure using hematopoietic stem cells as vectors to deliver genes intended to correct hereditary diseases.[60] In 2002 this work led to the publication of the first successful gene therapy treatment for adenosine deaminase deficiency (ADA-SCID). The success of a multi-center trial for treating children with SCID (severe combined immune deficiency or “bubble boy” disease) from 2000 and 2002, was questioned when two of the ten children treated at the trial’s Paris center developed a leukemia-like condition. Clinical trials were halted temporarily in 2002, but resumed after regulatory review of the protocol in the US, the United Kingdom, France, Italy, and Germany.[61]

In 1993 Andrew Gobea was born with SCID following prenatal genetic screening. Blood was removed from his mother’s placenta and umbilical cord immediately after birth, to acquire stem cells. The allele that codes for adenosine deaminase (ADA) was obtained and inserted into a retrovirus. Retroviruses and stem cells were mixed, after which the viruses inserted the gene into the stem cell chromosomes. Stem cells containing the working ADA gene were injected into Andrew’s blood. Injections of the ADA enzyme were also given weekly. For four years T cells (white blood cells), produced by stem cells, made ADA enzymes using the ADA gene. After four years more treatment was needed.[62]

Jesse Gelsinger’s death in 1999 impeded gene therapy research in the US.[63][64] As a result, the FDA suspended several clinical trials pending the reevaluation of ethical and procedural practices.[65]

The modified cancer gene therapy strategy of antisense IGF-I RNA (NIH n 1602)[59] using antisense / triple helix anti-IGF-I approach was registered in 2002 by Wiley gene therapy clinical trial – n 635 and 636. The approach has shown promising results in the treatment of six different malignant tumors: glioblastoma, cancers of liver, colon, prostate, uterus, and ovary (Collaborative NATO Science Programme on Gene Therapy USA, France, Poland n LST 980517 conducted by J. Trojan) (Trojan et al., 2012). This anti-gene antisense/triple helix therapy has proven to be efficient, due to the mechanism stopping simultaneously IGF-I expression on translation and transcription levels, strengthening anti-tumor immune and apoptotic phenomena.

Sickle-cell disease can be treated in mice.[66] The mice which have essentially the same defect that causes human cases used a viral vector to induce production of fetal hemoglobin (HbF), which normally ceases to be produced shortly after birth. In humans, the use of hydroxyurea to stimulate the production of HbF temporarily alleviates sickle cell symptoms. The researchers demonstrated this treatment to be a more permanent means to increase therapeutic HbF production.[67]

A new gene therapy approach repaired errors in messenger RNA derived from defective genes. This technique has the potential to treat thalassaemia, cystic fibrosis and some cancers.[68]

Researchers created liposomes 25 nanometers across that can carry therapeutic DNA through pores in the nuclear membrane.[69]

In 2003 a research team inserted genes into the brain for the first time. They used liposomes coated in a polymer called polyethylene glycol, which, unlike viral vectors, are small enough to cross the bloodbrain barrier.[70]

Short pieces of double-stranded RNA (short, interfering RNAs or siRNAs) are used by cells to degrade RNA of a particular sequence. If a siRNA is designed to match the RNA copied from a faulty gene, then the abnormal protein product of that gene will not be produced.[71]

Gendicine is a cancer gene therapy that delivers the tumor suppressor gene p53 using an engineered adenovirus. In 2003, it was approved in China for the treatment of head and neck squamous cell carcinoma.[25]

In March researchers announced the successful use of gene therapy to treat two adult patients for X-linked chronic granulomatous disease, a disease which affects myeloid cells and damages the immune system. The study is the first to show that gene therapy can treat the myeloid system.[72]

In May a team reported a way to prevent the immune system from rejecting a newly delivered gene.[73] Similar to organ transplantation, gene therapy has been plagued by this problem. The immune system normally recognizes the new gene as foreign and rejects the cells carrying it. The research utilized a newly uncovered network of genes regulated by molecules known as microRNAs. This natural function selectively obscured their therapeutic gene in immune system cells and protected it from discovery. Mice infected with the gene containing an immune-cell microRNA target sequence did not reject the gene.

In August scientists successfully treated metastatic melanoma in two patients using killer T cells genetically retargeted to attack the cancer cells.[74]

In November researchers reported on the use of VRX496, a gene-based immunotherapy for the treatment of HIV that uses a lentiviral vector to deliver an antisense gene against the HIV envelope. In a phase I clinical trial, five subjects with chronic HIV infection who had failed to respond to at least two antiretroviral regimens were treated. A single intravenous infusion of autologous CD4 T cells genetically modified with VRX496 was well tolerated. All patients had stable or decreased viral load; four of the five patients had stable or increased CD4 T cell counts. All five patients had stable or increased immune response to HIV antigens and other pathogens. This was the first evaluation of a lentiviral vector administered in a US human clinical trial.[75][76]

In May researchers announced the first gene therapy trial for inherited retinal disease. The first operation was carried out on a 23-year-old British male, Robert Johnson, in early 2007.[77]

Leber’s congenital amaurosis is an inherited blinding disease caused by mutations in the RPE65 gene. The results of a small clinical trial in children were published in April.[11] Delivery of recombinant adeno-associated virus (AAV) carrying RPE65 yielded positive results. In May two more groups reported positive results in independent clinical trials using gene therapy to treat the condition. In all three clinical trials, patients recovered functional vision without apparent side-effects.[11][12][13][14]

In September researchers were able to give trichromatic vision to squirrel monkeys.[78] In November 2009, researchers halted a fatal genetic disorder called adrenoleukodystrophy in two children using a lentivirus vector to deliver a functioning version of ABCD1, the gene that is mutated in the disorder.[79]

An April paper reported that gene therapy addressed achromatopsia (color blindness) in dogs by targeting cone photoreceptors. Cone function and day vision were restored for at least 33 months in two young specimens. The therapy was less efficient for older dogs.[80]

In September it was announced that an 18-year-old male patient in France with beta-thalassemia major had been successfully treated.[81] Beta-thalassemia major is an inherited blood disease in which beta haemoglobin is missing and patients are dependent on regular lifelong blood transfusions.[82] The technique used a lentiviral vector to transduce the human -globin gene into purified blood and marrow cells obtained from the patient in June 2007.[83] The patient’s haemoglobin levels were stable at 9 to 10 g/dL. About a third of the hemoglobin contained the form introduced by the viral vector and blood transfusions were not needed.[83][84] Further clinical trials were planned.[85] Bone marrow transplants are the only cure for thalassemia, but 75% of patients do not find a matching donor.[84]

Cancer immunogene therapy using modified antigene, antisense/triple helix approach was introduced in South America in 2010/11 in La Sabana University, Bogota (Ethical Committee 14 December 2010, no P-004-10). Considering the ethical aspect of gene diagnostic and gene therapy targeting IGF-I, the IGF-I expressing tumors i.e. lung and epidermis cancers were treated (Trojan et al. 2016).[86][87]

In 2007 and 2008, a man (Timothy Ray Brown) was cured of HIV by repeated hematopoietic stem cell transplantation (see also allogeneic stem cell transplantation, allogeneic bone marrow transplantation, allotransplantation) with double-delta-32 mutation which disables the CCR5 receptor. This cure was accepted by the medical community in 2011.[88] It required complete ablation of existing bone marrow, which is very debilitating.

In August two of three subjects of a pilot study were confirmed to have been cured from chronic lymphocytic leukemia (CLL). The therapy used genetically modified T cells to attack cells that expressed the CD19 protein to fight the disease.[20] In 2013, the researchers announced that 26 of 59 patients had achieved complete remission and the original patient had remained tumor-free.[89]

Human HGF plasmid DNA therapy of cardiomyocytes is being examined as a potential treatment for coronary artery disease as well as treatment for the damage that occurs to the heart after myocardial infarction.[90][91]

In 2011 Neovasculgen was registered in Russia as the first-in-class gene-therapy drug for treatment of peripheral artery disease, including critical limb ischemia; it delivers the gene encoding for VEGF.[92][26] Neovasculogen is a plasmid encoding the CMV promoter and the 165 amino acid form of VEGF.[93][94]

The FDA approved Phase 1 clinical trials on thalassemia major patients in the US for 10 participants in July.[95] The study was expected to continue until 2015.[85]

In July 2012, the European Medicines Agency recommended approval of a gene therapy treatment for the first time in either Europe or the United States. The treatment used Alipogene tiparvovec (Glybera) to compensate for lipoprotein lipase deficiency, which can cause severe pancreatitis.[96] The recommendation was endorsed by the European Commission in November 2012[10][27][97][98] and commercial rollout began in late 2014.[99] Alipogene tiparvovec was expected to cost around $1.6 million per treatment in 2012,[100] revised to $1 million in 2015,[101] making it the most expensive medicine in the world at the time.[102] As of 2016, only one person had been treated with drug.[103]

In December 2012, it was reported that 10 of 13 patients with multiple myeloma were in remission “or very close to it” three months after being injected with a treatment involving genetically engineered T cells to target proteins NY-ESO-1 and LAGE-1, which exist only on cancerous myeloma cells.[22]

In March researchers reported that three of five adult subjects who had acute lymphocytic leukemia (ALL) had been in remission for five months to two years after being treated with genetically modified T cells which attacked cells with CD19 genes on their surface, i.e. all B-cells, cancerous or not. The researchers believed that the patients’ immune systems would make normal T-cells and B-cells after a couple of months. They were also given bone marrow. One patient relapsed and died and one died of a blood clot unrelated to the disease.[21]

Following encouraging Phase 1 trials, in April, researchers announced they were starting Phase 2 clinical trials (called CUPID2 and SERCA-LVAD) on 250 patients[104] at several hospitals to combat heart disease. The therapy was designed to increase the levels of SERCA2, a protein in heart muscles, improving muscle function.[105] The FDA granted this a Breakthrough Therapy Designation to accelerate the trial and approval process.[106] In 2016 it was reported that no improvement was found from the CUPID 2 trial.[107]

In July researchers reported promising results for six children with two severe hereditary diseases had been treated with a partially deactivated lentivirus to replace a faulty gene and after 732 months. Three of the children had metachromatic leukodystrophy, which causes children to lose cognitive and motor skills.[108] The other children had Wiskott-Aldrich syndrome, which leaves them to open to infection, autoimmune diseases, and cancer.[109] Follow up trials with gene therapy on another six children with Wiskott-Aldrich syndrome were also reported as promising.[110][111]

In October researchers reported that two children born with adenosine deaminase severe combined immunodeficiency disease (ADA-SCID) had been treated with genetically engineered stem cells 18 months previously and that their immune systems were showing signs of full recovery. Another three children were making progress.[18] In 2014 a further 18 children with ADA-SCID were cured by gene therapy.[112] ADA-SCID children have no functioning immune system and are sometimes known as “bubble children.”[18]

Also in October researchers reported that they had treated six hemophilia sufferers in early 2011 using an adeno-associated virus. Over two years later all six were producing clotting factor.[18][113]

In January researchers reported that six choroideremia patients had been treated with adeno-associated virus with a copy of REP1. Over a six-month to two-year period all had improved their sight.[114][115] By 2016, 32 patients had been treated with positive results and researchers were hopeful the treatment would be long-lasting.[15] Choroideremia is an inherited genetic eye disease with no approved treatment, leading to loss of sight.

In March researchers reported that 12 HIV patients had been treated since 2009 in a trial with a genetically engineered virus with a rare mutation (CCR5 deficiency) known to protect against HIV with promising results.[116][117]

Clinical trials of gene therapy for sickle cell disease were started in 2014.[118][119] There is a need for high quality randomised controlled trials assessing the risks and benefits involved with gene therapy for people with sickle cell disease.[120]

In February LentiGlobin BB305, a gene therapy treatment undergoing clinical trials for treatment of beta thalassemia gained FDA “breakthrough” status after several patients were able to forgo the frequent blood transfusions usually required to treat the disease.[121]

In March researchers delivered a recombinant gene encoding a broadly neutralizing antibody into monkeys infected with simian HIV; the monkeys’ cells produced the antibody, which cleared them of HIV. The technique is named immunoprophylaxis by gene transfer (IGT). Animal tests for antibodies to ebola, malaria, influenza, and hepatitis were underway.[122][123]

In March, scientists, including an inventor of CRISPR, Jennifer Doudna, urged a worldwide moratorium on germline gene therapy, writing “scientists should avoid even attempting, in lax jurisdictions, germline genome modification for clinical application in humans” until the full implications “are discussed among scientific and governmental organizations”.[124][125][126][127]

In October, researchers announced that they had treated a baby girl, Layla Richards, with an experimental treatment using donor T-cells genetically engineered using TALEN to attack cancer cells. One year after the treatment she was still free of her cancer (a highly aggressive form of acute lymphoblastic leukaemia [ALL]).[128] Children with highly aggressive ALL normally have a very poor prognosis and Layla’s disease had been regarded as terminal before the treatment.[129]

In December, scientists of major world academies called for a moratorium on inheritable human genome edits, including those related to CRISPR-Cas9 technologies[130] but that basic research including embryo gene editing should continue.[131]

In April the Committee for Medicinal Products for Human Use of the European Medicines Agency endorsed a gene therapy treatment called Strimvelis[132][133] and the European Commission approved it in June.[134] This treats children born with adenosine deaminase deficiency and who have no functioning immune system. This was the second gene therapy treatment to be approved in Europe.[135]

In October, Chinese scientists reported they had started a trial to genetically modify T-cells from 10 adult patients with lung cancer and reinject the modified T-cells back into their bodies to attack the cancer cells. The T-cells had the PD-1 protein (which stops or slows the immune response) removed using CRISPR-Cas9.[136][137]

A 2016 Cochrane systematic review looking at data from four trials on topical cystic fibrosis transmembrane conductance regulator (CFTR) gene therapy does not support its clinical use as a mist inhaled into the lungs to treat cystic fibrosis patients with lung infections. One of the four trials did find weak evidence that liposome-based CFTR gene transfer therapy may lead to a small respiratory improvement for people with CF. This weak evidence is not enough to make a clinical recommendation for routine CFTR gene therapy.[138]

In February Kite Pharma announced results from a clinical trial of CAR-T cells in around a hundred people with advanced Non-Hodgkin lymphoma.[139]

In March, French scientists reported on clinical research of gene therapy to treat sickle-cell disease.[140]

In August, the FDA approved tisagenlecleucel for acute lymphoblastic leukemia.[141] Tisagenlecleucel is an adoptive cell transfer therapy for B-cell acute lymphoblastic leukemia; T cells from a person with cancer are removed, genetically engineered to make a specific T-cell receptor (a chimeric T cell receptor, or “CAR-T”) that reacts to the cancer, and are administered back to the person. The T cells are engineered to target a protein called CD19 that is common on B cells. This is the first form of gene therapy to be approved in the United States. In October, a similar therapy called axicabtagene ciloleucel was approved for non-Hodgkin lymphoma.[142]

In December the results of using an adeno-associated virus with blood clotting factor VIII to treat nine haemophilia A patients were published. Six of the seven patients on the high dose regime increased the level of the blood clotting VIII to normal levels. The low and medium dose regimes had no effect on the patient’s blood clotting levels.[143][144]

In December, the FDA approved Luxturna, the first in vivo gene therapy, for the treatment of blindness due to Leber’s congenital amaurosis.[145] The price of this treatment was 850,000 US dollars for both eyes.[146][147] CRISPR gene editing technology has also been used on mice to treat deafness due to the DFNA36 mutation, which also affects humans.[148]

Speculated uses for gene therapy include:

Gene Therapy techniques have the potential to provide alternative treatments for those with infertility. Recently, successful experimentation on mice has proven that fertility can be restored by using the gene therapy method, CRISPR.[149] Spermatogenical stem cells from another organism were transplanted into the testes of an infertile male mouse. The stem cells re-established spermatogenesis and fertility.[150]

Athletes might adopt gene therapy technologies to improve their performance.[151] Gene doping is not known to occur, but multiple gene therapies may have such effects. Kayser et al. argue that gene doping could level the playing field if all athletes receive equal access. Critics claim that any therapeutic intervention for non-therapeutic/enhancement purposes compromises the ethical foundations of medicine and sports.[152]

Genetic engineering could be used to cure diseases, but also to change physical appearance, metabolism, and even improve physical capabilities and mental faculties such as memory and intelligence. Ethical claims about germline engineering include beliefs that every fetus has a right to remain genetically unmodified, that parents hold the right to genetically modify their offspring, and that every child has the right to be born free of preventable diseases.[153][154][155] For parents, genetic engineering could be seen as another child enhancement technique to add to diet, exercise, education, training, cosmetics, and plastic surgery.[156][157] Another theorist claims that moral concerns limit but do not prohibit germline engineering.[158]

Possible regulatory schemes include a complete ban, provision to everyone, or professional self-regulation. The American Medical Associations Council on Ethical and Judicial Affairs stated that “genetic interventions to enhance traits should be considered permissible only in severely restricted situations: (1) clear and meaningful benefits to the fetus or child; (2) no trade-off with other characteristics or traits; and (3) equal access to the genetic technology, irrespective of income or other socioeconomic characteristics.”[159]

As early in the history of biotechnology as 1990, there have been scientists opposed to attempts to modify the human germline using these new tools,[160] and such concerns have continued as technology progressed.[161][162] With the advent of new techniques like CRISPR, in March 2015 a group of scientists urged a worldwide moratorium on clinical use of gene editing technologies to edit the human genome in a way that can be inherited.[124][125][126][127] In April 2015, researchers sparked controversy when they reported results of basic research to edit the DNA of non-viable human embryos using CRISPR.[149][163] A committee of the American National Academy of Sciences and National Academy of Medicine gave qualified support to human genome editing in 2017[164][165] once answers have been found to safety and efficiency problems “but only for serious conditions under stringent oversight.”[166]

Regulations covering genetic modification are part of general guidelines about human-involved biomedical research. There are no international treaties which are legally binding in this area, but there are recommendations for national laws from various bodies.

The Helsinki Declaration (Ethical Principles for Medical Research Involving Human Subjects) was amended by the World Medical Association’s General Assembly in 2008. This document provides principles physicians and researchers must consider when involving humans as research subjects. The Statement on Gene Therapy Research initiated by the Human Genome Organization (HUGO) in 2001 provides a legal baseline for all countries. HUGOs document emphasizes human freedom and adherence to human rights, and offers recommendations for somatic gene therapy, including the importance of recognizing public concerns about such research.[167]

No federal legislation lays out protocols or restrictions about human genetic engineering. This subject is governed by overlapping regulations from local and federal agencies, including the Department of Health and Human Services, the FDA and NIH’s Recombinant DNA Advisory Committee. Researchers seeking federal funds for an investigational new drug application, (commonly the case for somatic human genetic engineering,) must obey international and federal guidelines for the protection of human subjects.[168]

NIH serves as the main gene therapy regulator for federally funded research. Privately funded research is advised to follow these regulations. NIH provides funding for research that develops or enhances genetic engineering techniques and to evaluate the ethics and quality in current research. The NIH maintains a mandatory registry of human genetic engineering research protocols that includes all federally funded projects.

An NIH advisory committee published a set of guidelines on gene manipulation.[169] The guidelines discuss lab safety as well as human test subjects and various experimental types that involve genetic changes. Several sections specifically pertain to human genetic engineering, including Section III-C-1. This section describes required review processes and other aspects when seeking approval to begin clinical research involving genetic transfer into a human patient.[170] The protocol for a gene therapy clinical trial must be approved by the NIH’s Recombinant DNA Advisory Committee prior to any clinical trial beginning; this is different from any other kind of clinical trial.[169]

As with other kinds of drugs, the FDA regulates the quality and safety of gene therapy products and supervises how these products are used clinically. Therapeutic alteration of the human genome falls under the same regulatory requirements as any other medical treatment. Research involving human subjects, such as clinical trials, must be reviewed and approved by the FDA and an Institutional Review Board.[171][172]

Gene therapy is the basis for the plotline of the film I Am Legend[173] and the TV show Will Gene Therapy Change the Human Race?.[174] In 1994, gene therapy was a plot element in The Erlenmeyer Flask, The X-Files’ first season finale. It is also used in Stargate as a means of allowing humans to use Ancient technology.[175]

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Gene therapy – Wikipedia

Gene Therapy Net – News, Conferences, Vectors, Literature …

Posted on: 22 March 2018, source: GizmodoOn Tuesday, a 13-year-old boy from New Jersey was at the center of medical history as he became the first person in the US to receive an FDA-approved gene therapy for an inherited disease. The event marks the beginning of a new era of medicine, one in which devastating genetic conditions that we are born with can be simply edited out of our DNA with the help of modern biomedical technologies. The therapy, Luxturna, from Spark Therepeutics, was approved by the FDA in December to treat a rare, inherited form of blindness. Its price tag, set at $850,000or $425,000 per eyemade it the most expensive drug in the US and sparked mass sticker-shock. But the therapy, which in high-profile clinical trials has allowed patients to see the stars for the first times, also offered the almost miraculous possibility of giving sight to the blind.

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Gene Therapy Retrovirus Vectors Explained

A retrovirus is any virus belonging to the viral family Retroviridae. All The genetic material in retroviruses is in the form of RNA molecules, while the genetic material of their hosts is in the form of DNA. When a retrovirus infects a host cell, it will introduce its RNA together with some enzymes into the cell. This RNA molecule from the retrovirus must produce a DNA copy from its RNA molecule before it can be considered part of the genetic material of the host cell. Retrovirus genomes commonly contain these three open reading frames that encode for proteins that can be found in the mature virus. Group-specific antigen (gag) codes for core and structural proteins of the virus, polymerase (pol) codes for reverse transcriptase, protease and integrase, and envelope (env) codes for the retroviral coat proteins (see figure 1). Figure 1. Genome organisation of retroviruses.

The process of producing a DNA copy from an RNA molecule is termed reverse transcription. It is carried out by one of the enzymes carried in the virus, called reverse transcriptase. After this DNA copy is produced and is free in the nucleus of the host cell, it must be incorporated into the genome of the host cell. That is, it must be inserted into the large DNA molecules in the cell (the chromosomes). This process is done by another enzyme carried in the virus called integrase (see figure 2).

Now that the genetic material of the virus is incorporated and has become part of the genetic material of the host cell, we can say that the host cell is now modified to contain a new gene. If this host cell divides later, its descendants will all contain the new genes. Sometimes the genes of the retrovirus do not express their information immediately.

Retroviral vectors are created by removal op the retroviral gag, pol, and env genes. These are replaced by the therapeutic gene. In order to produce vector particles a packaging cell is essential. Packaging cell lines provide all the viral proteins required for capsid production and the virion maturation of the vector. These packaging cell lines have been made so that they contain the gag, pol and env genes. Early packaging cell lines contained replication competent retroviral genomes and a single recombination event between this genome and the retroviral DNA vector could result in the production of a wild type virus. Following insertion of the desired gene into in the retroviral DNA vector, and maintainance of the proper packaging cell line, it is now a simple matter to prepare retroviral vectors (see figure 3).

One of the problems of gene therapy using retroviruses is that the integrase enzyme can insert the genetic material of the virus in any arbitrary position in the genome of the host. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted (insertional mutagenesis). If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur. This problem has recently begun to be addressed by utilizing zinc finger nucleases or by including certain sequences such as the beta-globin locus control region to direct the site of integration to specific chromosomal sites.

Gene therapy trials to treat severe combined immunodeficiency (SCID) were halted or restricted in the USA when leukemia was reported in three of eleven patients treated in the French X-linked SCID (X-SCID) gene therapy trial. Ten X-SCID patients treated in England have not presented leukemia to date and have had similar success in immune reconstitution. Gene therapy trials to treat SCID due to deficiency of the Adenosine Deaminase (ADA) enzyme continue with relative success in the USA, Italy and Japan.

As a reaction to the adverse events in the French X-SCID gene therapy trial, the Recombinant DNA Advisory Committee (RAC) sent a letter to Principal Investigators Conveying RAC Recommendations in 2003. In addition, the RAC published conclusions and recommendations of the RAC Gene Transfer Safety Symposium in 2005. A joint working party of the Gene Therapy Advisory Committee and the Committee on Safety of Medicines (CSM) in the UK lead to the publication of an updated recommendations of the GTAC/CSM working party on retroviruses in 2005.

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Gene Therapy Retrovirus Vectors Explained

Vectors in gene therapy – Wikipedia

Gene therapy utilizes the delivery of DNA into cells, which can be accomplished by several methods, summarized below. The two major classes of methods are those that use recombinant viruses (sometimes called biological nanoparticles or viral vectors) and those that use naked DNA or DNA complexes (non-viral methods).

All viruses bind to their hosts and introduce their genetic material into the host cell as part of their replication cycle. This genetic material contains basic ‘instructions’ of how to produce more copies of these viruses, hacking the body’s normal production machinery to serve the needs of the virus. The host cell will carry out these instructions and produce additional copies of the virus, leading to more and more cells becoming infected. Some types of viruses insert their genome into the host’s cytoplasm, but do not actually enter the cell. Others penetrate the cell membrane disguised as protein molecules and enter the cell.

There are two main types of virus infection: lytic and lysogenic. Shortly after inserting its DNA, viruses of the lytic cycle quickly produce more viruses, burst from the cell and infect more cells. Lysogenic viruses integrate their DNA into the DNA of the host cell and may live in the body for many years before responding to a trigger. The virus reproduces as the cell does and does not inflict bodily harm until it is triggered. The trigger releases the DNA from that of the host and employs it to create new viruses.

The genetic material in retroviruses is in the form of RNA molecules, while the genetic material of their hosts is in the form of DNA. When a retrovirus infects a host cell, it will introduce its RNA together with some enzymes, namely reverse transcriptase and integrase, into the cell. This RNA molecule from the retrovirus must produce a DNA copy from its RNA molecule before it can be integrated into the genetic material of the host cell. The process of producing a DNA copy from an RNA molecule is termed reverse transcription. It is carried out by one of the enzymes carried in the virus, called reverse transcriptase. After this DNA copy is produced and is free in the nucleus of the host cell, it must be incorporated into the genome of the host cell. That is, it must be inserted into the large DNA molecules in the cell (the chromosomes). This process is done by another enzyme carried in the virus called integrase.

Now that the genetic material of the virus has been inserted, it can be said that the host cell has been modified to contain new genes. If this host cell divides later, its descendants will all contain the new genes. Sometimes the genes of the retrovirus do not express their information immediately.

One of the problems of gene therapy using retroviruses is that the integrase enzyme can insert the genetic material of the virus into any arbitrary position in the genome of the host; it randomly inserts the genetic material into a chromosome. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted (insertional mutagenesis). If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur. This problem has recently begun to be addressed by utilizing zinc finger nucleases[1] or by including certain sequences such as the beta-globin locus control region to direct the site of integration to specific chromosomal sites.

Gene therapy trials using retroviral vectors to treat X-linked severe combined immunodeficiency (X-SCID) represent the most successful application of gene therapy to date. More than twenty patients have been treated in France and Britain, with a high rate of immune system reconstitution observed. Similar trials were restricted or halted in the USA when leukemia was reported in patients treated in the French X-SCID gene therapy trial.[citation needed] To date, four children in the French trial and one in the British trial have developed leukemia as a result of insertional mutagenesis by the retroviral vector. All but one of these children responded well to conventional anti-leukemia treatment. Gene therapy trials to treat SCID due to deficiency of the Adenosine Deaminase (ADA) enzyme (one form of SCID)[2] continue with relative success in the USA, Britain, Ireland, Italy and Japan.

Adenoviruses are viruses that carry their genetic material in the form of double-stranded DNA. They cause respiratory, intestinal, and eye infections in humans (especially the common cold). When these viruses infect a host cell, they introduce their DNA molecule into the host. The genetic material of the adenoviruses is not incorporated (transient) into the host cell’s genetic material. The DNA molecule is left free in the nucleus of the host cell, and the instructions in this extra DNA molecule are transcribed just like any other gene. The only difference is that these extra genes are not replicated when the cell is about to undergo cell division so the descendants of that cell will not have the extra gene. As a result, treatment with the adenovirus will require readministration in a growing cell population although the absence of integration into the host cell’s genome should prevent the type of cancer seen in the SCID trials. This vector system has been promoted for treating cancer and indeed the first gene therapy product to be licensed to treat cancer, Gendicine, is an adenovirus. Gendicine, an adenoviral p53-based gene therapy was approved by the Chinese food and drug regulators in 2003 for treatment of head and neck cancer. Advexin, a similar gene therapy approach from Introgen, was turned down by the US Food and Drug Administration (FDA) in 2008.

Concerns about the safety of adenovirus vectors were raised after the 1999 death of Jesse Gelsinger while participating in a gene therapy trial. Since then, work using adenovirus vectors has focused on genetically crippled versions of the virus.

The viral vectors described above have natural host cell populations that they infect most efficiently. Retroviruses have limited natural host cell ranges, and although adenovirus and adeno-associated virus are able to infect a relatively broader range of cells efficiently, some cell types are refractory to infection by these viruses as well. Attachment to and entry into a susceptible cell is mediated by the protein envelope on the surface of a virus. Retroviruses and adeno-associated viruses have a single protein coating their membrane, while adenoviruses are coated with both an envelope protein and fibers that extend away from the surface of the virus. The envelope proteins on each of these viruses bind to cell-surface molecules such as heparin sulfate, which localizes them upon the surface of the potential host, as well as with the specific protein receptor that either induces entry-promoting structural changes in the viral protein, or localizes the virus in endosomes wherein acidification of the lumen induces this refolding of the viral coat. In either case, entry into potential host cells requires a favorable interaction between a protein on the surface of the virus and a protein on the surface of the cell. For the purposes of gene therapy, one might either want to limit or expand the range of cells susceptible to transduction by a gene therapy vector. To this end, many vectors have been developed in which the endogenous viral envelope proteins have been replaced by either envelope proteins from other viruses, or by chimeric proteins. Such chimera would consist of those parts of the viral protein necessary for incorporation into the virion as well as sequences meant to interact with specific host cell proteins. Viruses in which the envelope proteins have been replaced as described are referred to as pseudotyped viruses. For example, the most popular retroviral vector for use in gene therapy trials has been the lentivirus Simian immunodeficiency virus coated with the envelope proteins, G-protein, from Vesicular stomatitis virus. This vector is referred to as VSV G-pseudotyped lentivirus, and infects an almost universal set of cells. This tropism is characteristic of the VSV G-protein with which this vector is coated. Many attempts have been made to limit the tropism of viral vectors to one or a few host cell populations. This advance would allow for the systemic administration of a relatively small amount of vector. The potential for off-target cell modification would be limited, and many concerns from the medical community would be alleviated. Most attempts to limit tropism have used chimeric envelope proteins bearing antibody fragments. These vectors show great promise for the development of “magic bullet” gene therapies.

A replication-competent vector called ONYX-015 is used in replicating tumor cells. It was found that in the absence of the E1B-55Kd viral protein, adenovirus caused very rapid apoptosis of infected, p53(+) cells, and this results in dramatically reduced virus progeny and no subsequent spread. Apoptosis was mainly the result of the ability of EIA to inactivate p300. In p53(-) cells, deletion of E1B 55kd has no consequence in terms of apoptosis, and viral replication is similar to that of wild-type virus, resulting in massive killing of cells.

A replication-defective vector deletes some essential genes. These deleted genes are still necessary in the body so they are replaced with either a helper virus or a DNA molecule.

[3]

Replication-defective vectors always contain a transfer construct. The transfer construct carries the gene to be transduced or transgene. The transfer construct also carries the sequences which are necessary for the general functioning of the viral genome: packaging sequence, repeats for replication and, when needed, priming of reverse transcription. These are denominated cis-acting elements, because they need to be on the same piece of DNA as the viral genome and the gene of interest. Trans-acting elements are viral elements, which can be encoded on a different DNA molecule. For example, the viral structural proteins can be expressed from a different genetic element than the viral genome.

[3]

The Herpes simplex virus is a human neurotropic virus. This is mostly examined for gene transfer in the nervous system. The wild type HSV-1 virus is able to infect neurons and evade the host immune response, but may still become reactivated and produce a lytic cycle of viral replication. Therefore, it is typical to use mutant strains of HSV-1 that are deficient in their ability to replicate. Though the latent virus is not transcriptionally apparent, it does possess neuron specific promoters that can continue to function normally[further explanation needed]. Antibodies to HSV-1 are common in humans, however complications due to herpes infection are somewhat rare.[4] Caution for rare cases of encephalitis must be taken and this provides some rationale to using HSV-2 as a viral vector as it generally has tropism for neuronal cells innervating the urogenital area of the body and could then spare the host of severe pathology in the brain.

Non-viral methods present certain advantages over viral methods, with simple large scale production and low host immunogenicity being just two. Previously, low levels of transfection and expression of the gene held non-viral methods at a disadvantage; however, recent advances in vector technology have yielded molecules and techniques with transfection efficiencies similar to those of viruses.[5]

This is the simplest method of non-viral transfection. Clinical trials carried out of intramuscular injection of a naked DNA plasmid have occurred with some success; however, the expression has been very low in comparison to other methods of transfection. In addition to trials with plasmids, there have been trials with naked PCR product, which have had similar or greater success. Cellular uptake of naked DNA is generally inefficient. Research efforts focusing on improving the efficiency of naked DNA uptake have yielded several novel methods, such as electroporation, sonoporation, and the use of a “gene gun”, which shoots DNA coated gold particles into the cell using high pressure gas.[6]

Electroporation is a method that uses short pulses of high voltage to carry DNA across the cell membrane. This shock is thought to cause temporary formation of pores in the cell membrane, allowing DNA molecules to pass through. Electroporation is generally efficient and works across a broad range of cell types. However, a high rate of cell death following electroporation has limited its use, including clinical applications.

More recently a newer method of electroporation, termed electron-avalanche transfection, has been used in gene therapy experiments. By using a high-voltage plasma discharge, DNA was efficiently delivered following very short (microsecond) pulses. Compared to electroporation, the technique resulted in greatly increased efficiency and less cellular damage.

The use of particle bombardment, or the gene gun, is another physical method of DNA transfection. In this technique, DNA is coated onto gold particles and loaded into a device which generates a force to achieve penetration of the DNA into the cells, leaving the gold behind on a “stopping” disk.

Sonoporation uses ultrasonic frequencies to deliver DNA into cells. The process of acoustic cavitation is thought to disrupt the cell membrane and allow DNA to move into cells.

In a method termed magnetofection, DNA is complexed to magnetic particles, and a magnet is placed underneath the tissue culture dish to bring DNA complexes into contact with a cell monolayer.

Hydrodynamic delivery involves rapid injection of a high volume of a solution into vasculature (such as into the inferior vena cava, bile duct, or tail vein). The solution contains molecules that are to be inserted into cells, such as DNA plasmids or siRNA, and transfer of these molecules into cells is assisted by the elevated hydrostatic pressure caused by the high volume of injected solution.[7][8][9]

The use of synthetic oligonucleotides in gene therapy is to deactivate the genes involved in the disease process. There are several methods by which this is achieved. One strategy uses antisense specific to the target gene to disrupt the transcription of the faulty gene. Another uses small molecules of RNA called siRNA to signal the cell to cleave specific unique sequences in the mRNA transcript of the faulty gene, disrupting translation of the faulty mRNA, and therefore expression of the gene. A further strategy uses double stranded oligodeoxynucleotides as a decoy for the transcription factors that are required to activate the transcription of the target gene. The transcription factors bind to the decoys instead of the promoter of the faulty gene, which reduces the transcription of the target gene, lowering expression. Additionally, single stranded DNA oligonucleotides have been used to direct a single base change within a mutant gene. The oligonucleotide is designed to anneal with complementarity to the target gene with the exception of a central base, the target base, which serves as the template base for repair. This technique is referred to as oligonucleotide mediated gene repair, targeted gene repair, or targeted nucleotide alteration.

To improve the delivery of the new DNA into the cell, the DNA must be protected from damage and positively charged. Initially, anionic and neutral lipids were used for the construction of lipoplexes for synthetic vectors. However, in spite of the facts that there is little toxicity associated with them, that they are compatible with body fluids and that there was a possibility of adapting them to be tissue specific; they are complicated and time consuming to produce so attention was turned to the cationic versions.

Cationic lipids, due to their positive charge, were first used to condense negatively charged DNA molecules so as to facilitate the encapsulation of DNA into liposomes. Later it was found that the use of cationic lipids significantly enhanced the stability of lipoplexes. Also as a result of their charge, cationic liposomes interact with the cell membrane, endocytosis was widely believed as the major route by which cells uptake lipoplexes. Endosomes are formed as the results of endocytosis, however, if genes can not be released into cytoplasm by breaking the membrane of endosome, they will be sent to lysosomes where all DNA will be destroyed before they could achieve their functions. It was also found that although cationic lipids themselves could condense and encapsulate DNA into liposomes, the transfection efficiency is very low due to the lack of ability in terms of endosomal escaping. However, when helper lipids (usually electroneutral lipids, such as DOPE) were added to form lipoplexes, much higher transfection efficiency was observed. Later on, it was figured out that certain lipids have the ability to destabilize endosomal membranes so as to facilitate the escape of DNA from endosome, therefore those lipids are called fusogenic lipids. Although cationic liposomes have been widely used as an alternative for gene delivery vectors, a dose dependent toxicity of cationic lipids were also observed which could limit their therapeutic usages.

The most common use of lipoplexes has been in gene transfer into cancer cells, where the supplied genes have activated tumor suppressor control genes in the cell and decrease the activity of oncogenes. Recent studies have shown lipoplexes to be useful in transfecting respiratory epithelial cells.

Polymersomes are synthetic versions of liposomes (vesicles with a lipid bilayer), made of amphiphilic block copolymers. They can encapsulate either hydrophilic or hydrophobic contents and can be used to deliver cargo such as DNA, proteins, or drugs to cells. Advantages of polymersomes over liposomes include greater stability, mechanical strength, blood circulation time, and storage capacity.[10][11][12]

Complexes of polymers with DNA are called polyplexes. Most polyplexes consist of cationic polymers and their fabrication is based on self-assembly by ionic interactions. One important difference between the methods of action of polyplexes and lipoplexes is that polyplexes cannot directly release their DNA load into the cytoplasm. As a result, co-transfection with endosome-lytic agents such as inactivated adenovirus was required to facilitate nanoparticle escape from the endocytic vesicle made during particle uptake. However, a better understanding of the mechanisms by which DNA can escape from endolysosomal pathway, i.e. proton sponge effect,[13] has triggered new polymer synthesis strategies such as incorporation of protonable residues in polymer backbone and has revitalized research on polycation-based systems.[14]

Due to their low toxicity, high loading capacity, and ease of fabrication, polycationic nanocarriers demonstrate great promise compared to their rivals such as viral vectors which show high immunogenicity and potential carcinogenicity, and lipid-based vectors which cause dose dependence toxicity. Polyethyleneimine[15] and chitosan are among the polymeric carriers that have been extensively studies for development of gene delivery therapeutics. Other polycationic carriers such as poly(beta-amino esters)[16] and polyphosphoramidate[17] are being added to the library of potential gene carriers. In addition to the variety of polymers and copolymers, the ease of controlling the size, shape, surface chemistry of these polymeric nano-carriers gives them an edge in targeting capability and taking advantage of enhanced permeability and retention effect.[18]

A dendrimer is a highly branched macromolecule with a spherical shape. The surface of the particle may be functionalized in many ways and many of the properties of the resulting construct are determined by its surface.

In particular it is possible to construct a cationic dendrimer, i.e. one with a positive surface charge. When in the presence of genetic material such as DNA or RNA, charge complimentarity leads to a temporary association of the nucleic acid with the cationic dendrimer. On reaching its destination the dendrimer-nucleic acid complex is then taken into the cell via endocytosis.

In recent years the benchmark for transfection agents has been cationic lipids. Limitations of these competing reagents have been reported to include: the lack of ability to transfect some cell types, the lack of robust active targeting capabilities, incompatibility with animal models, and toxicity. Dendrimers offer robust covalent construction and extreme control over molecule structure, and therefore size. Together these give compelling advantages compared to existing approaches.

Producing dendrimers has historically been a slow and expensive process consisting of numerous slow reactions, an obstacle that severely curtailed their commercial development. The Michigan-based company Dendritic Nanotechnologies discovered a method to produce dendrimers using kinetically driven chemistry, a process that not only reduced cost by a magnitude of three, but also cut reaction time from over a month to several days. These new “Priostar” dendrimers can be specifically constructed to carry a DNA or RNA payload that transfects cells at a high efficiency with little or no toxicity.[citation needed]

Inorganic nanoparticles, such as gold, silica, iron oxide (ex. magnetofection) and calcium phosphates have been shown to be capable of gene delivery.[19] Some of the benefits of inorganic vectors is in their storage stability, low manufacturing cost and often time, low immunogenicity, and resistance to microbial attack. Nanosized materials less than 100nm have been shown to efficiently trap the DNA or RNA and allows its escape from the endosome without degradation. Inorganics have also been shown to exhibit improved in vitro transfection for attached cell lines due to their increased density and preferential location on the base of the culture dish. Quantum dots have also been used successfully and permits the coupling of gene therapy with a stable fluorescence marker. Engineered organic nanoparticles are also under development, which could be used for co-delivery of genes and therapeutic agents.[20]

Cell-penetrating peptides (CPPs), also known as peptide transduction domains (PTDs), are short peptides (

CPP cargo can be directed into specific cell organelles by incorporating localization sequences into CPP sequences. For example, nuclear localization sequences are commonly used to guide CPP cargo into the nucleus.[23] For guidance into mitochondria, a mitochondrial targeting sequence can be used; this method is used in protofection (a technique that allows for foreign mitochondrial DNA to be inserted into cells’ mitochondria).[24][25]

Due to every method of gene transfer having shortcomings, there have been some hybrid methods developed that combine two or more techniques. Virosomes are one example; they combine liposomes with an inactivated HIV or influenza virus. This has been shown to have more efficient gene transfer in respiratory epithelial cells than either viral or liposomal methods alone. Other methods involve mixing other viral vectors with cationic lipids or hybridising viruses.

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Vectors in gene therapy – Wikipedia

Gene Therapy | Pfizer: One of the world’s premier …

Gene therapy is a technology aimed at correcting or fixing a gene that may be defective. This exciting and potentially transformative area of research is focused on the development of potential treatments for monogenic diseases, or diseases that are caused by a defect in one gene.

The technology involves the introduction of genetic material (DNA or RNA) into the body, often through delivering a corrected copy of a gene to a patients cells to compensate for a defective one, using a viral vector.

The technology involves the introduction of genetic material (DNA or RNA) into the body, often through delivering a corrected copy of a gene to a patients cells to compensate for a defective one, using a viral vector.

Viral vectors can be developed using adeno-associated virus (AAV), a naturally occurring virus which has been adapted for gene therapy use. Its ability to deliver genetic material to a wide range of tissues makes AAV vectors useful for transferring therapeutic genes into target cells. Gene therapy research holds tremendous promise in leading to the possible development of highly-specialized, potentially one-time delivery treatments for patients suffering from rare, monogenic diseases.

Pfizer aims to build an industry-leading gene therapy platform with a strategy focused on establishing a transformational portfolio through in-house capabilities, and enhancing those capabilities through strategic collaborations, as well as potential licensing and M&A activities.

We’re working to access the most effective vector designs available to build a robust clinical stage portfolio, and employing a scalable manufacturing approach, proprietary cell lines and sophisticated analytics to support clinical development.

In addition, we’re collaborating with some of the foremost experts in this field, through collaborations with Spark Therapeutics, Inc., on a potentially transformative gene therapy treatment for hemophilia B, which received Breakthrough Therapy designation from the US Food and Drug Administration, and 4D Molecular Therapeutics to discover and develop targeted next-generation AAV vectors for cardiac disease.

Gene therapy holds the promise of bringing true disease modification for patients suffering from devastating diseases, a promise were working to seeing become a reality in the years to come.

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Gene therapy – Wikipedia

In the medicine field, gene therapy (also called human gene transfer) is the therapeutic delivery of nucleic acid into a patient’s cells as a drug to treat disease.[1][2] The first attempt at modifying human DNA was performed in 1980 by Martin Cline, but the first successful nuclear gene transfer in humans, approved by the National Institutes of Health, was performed in May 1989.[3] The first therapeutic use of gene transfer as well as the first direct insertion of human DNA into the nuclear genome was performed by French Anderson in a trial starting in September 1990.

Between 1989 and February 2016, over 2,300 clinical trials had been conducted, more than half of them in phase I.[4]

Not all medical procedures that introduce alterations to a patient’s genetic makeup can be considered gene therapy. Bone marrow transplantation and organ transplants in general have been found to introduce foreign DNA into patients.[5] Gene therapy is defined by the precision of the procedure and the intention of direct therapeutic effects.

Gene therapy was conceptualized in 1972, by authors who urged caution before commencing human gene therapy studies.

The first attempt, an unsuccessful one, at gene therapy (as well as the first case of medical transfer of foreign genes into humans not counting organ transplantation) was performed by Martin Cline on 10 July 1980.[6][7] Cline claimed that one of the genes in his patients was active six months later, though he never published this data or had it verified[8] and even if he is correct, it’s unlikely it produced any significant beneficial effects treating beta-thalassemia.

After extensive research on animals throughout the 1980s and a 1989 bacterial gene tagging trial on humans, the first gene therapy widely accepted as a success was demonstrated in a trial that started on 14 September 1990, when Ashi DeSilva was treated for ADA-SCID.[9]

The first somatic treatment that produced a permanent genetic change was performed in 1993.[citation needed]

Gene therapy is a way to fix a genetic problem at its source. The polymers are either translated into proteins, interfere with target gene expression, or possibly correct genetic mutations.

The most common form uses DNA that encodes a functional, therapeutic gene to replace a mutated gene. The polymer molecule is packaged within a “vector”, which carries the molecule inside cells.

Early clinical failures led to dismissals of gene therapy. Clinical successes since 2006 regained researchers’ attention, although as of 2014, it was still largely an experimental technique.[10] These include treatment of retinal diseases Leber’s congenital amaurosis[11][12][13][14] and choroideremia,[15] X-linked SCID,[16] ADA-SCID,[17][18] adrenoleukodystrophy,[19] chronic lymphocytic leukemia (CLL),[20] acute lymphocytic leukemia (ALL),[21] multiple myeloma,[22] haemophilia,[18] and Parkinson’s disease.[23] Between 2013 and April 2014, US companies invested over $600 million in the field.[24]

The first commercial gene therapy, Gendicine, was approved in China in 2003 for the treatment of certain cancers.[25] In 2011 Neovasculgen was registered in Russia as the first-in-class gene-therapy drug for treatment of peripheral artery disease, including critical limb ischemia.[26] In 2012 Glybera, a treatment for a rare inherited disorder, became the first treatment to be approved for clinical use in either Europe or the United States after its endorsement by the European Commission.[10][27]

Following early advances in genetic engineering of bacteria, cells, and small animals, scientists started considering how to apply it to medicine. Two main approaches were considered replacing or disrupting defective genes.[28] Scientists focused on diseases caused by single-gene defects, such as cystic fibrosis, haemophilia, muscular dystrophy, thalassemia, and sickle cell anemia. Glybera treats one such disease, caused by a defect in lipoprotein lipase.[27]

DNA must be administered, reach the damaged cells, enter the cell and either express or disrupt a protein.[29] Multiple delivery techniques have been explored. The initial approach incorporated DNA into an engineered virus to deliver the DNA into a chromosome.[30][31] Naked DNA approaches have also been explored, especially in the context of vaccine development.[32]

Generally, efforts focused on administering a gene that causes a needed protein to be expressed. More recently, increased understanding of nuclease function has led to more direct DNA editing, using techniques such as zinc finger nucleases and CRISPR. The vector incorporates genes into chromosomes. The expressed nucleases then knock out and replace genes in the chromosome. As of 2014 these approaches involve removing cells from patients, editing a chromosome and returning the transformed cells to patients.[33]

Gene editing is a potential approach to alter the human genome to treat genetic diseases,[34] viral diseases,[35] and cancer.[36] As of 2016 these approaches were still years from being medicine.[37][38]

Gene therapy may be classified into two types:

In somatic cell gene therapy (SCGT), the therapeutic genes are transferred into any cell other than a gamete, germ cell, gametocyte, or undifferentiated stem cell. Any such modifications affect the individual patient only, and are not inherited by offspring. Somatic gene therapy represents mainstream basic and clinical research, in which therapeutic DNA (either integrated in the genome or as an external episome or plasmid) is used to treat disease.

Over 600 clinical trials utilizing SCGT are underway in the US. Most focus on severe genetic disorders, including immunodeficiencies, haemophilia, thalassaemia, and cystic fibrosis. Such single gene disorders are good candidates for somatic cell therapy. The complete correction of a genetic disorder or the replacement of multiple genes is not yet possible. Only a few of the trials are in the advanced stages.[39]

In germline gene therapy (GGT), germ cells (sperm or egg cells) are modified by the introduction of functional genes into their genomes. Modifying a germ cell causes all the organism’s cells to contain the modified gene. The change is therefore heritable and passed on to later generations. Australia, Canada, Germany, Israel, Switzerland, and the Netherlands[40] prohibit GGT for application in human beings, for technical and ethical reasons, including insufficient knowledge about possible risks to future generations[40] and higher risks versus SCGT.[41] The US has no federal controls specifically addressing human genetic modification (beyond FDA regulations for therapies in general).[40][42][43][44]

The delivery of DNA into cells can be accomplished by multiple methods. The two major classes are recombinant viruses (sometimes called biological nanoparticles or viral vectors) and naked DNA or DNA complexes (non-viral methods).

In order to replicate, viruses introduce their genetic material into the host cell, tricking the host’s cellular machinery into using it as blueprints for viral proteins. Retroviruses go a stage further by having their genetic material copied into the genome of the host cell. Scientists exploit this by substituting a virus’s genetic material with therapeutic DNA. (The term ‘DNA’ may be an oversimplification, as some viruses contain RNA, and gene therapy could take this form as well.) A number of viruses have been used for human gene therapy, including retroviruses, adenoviruses, herpes simplex, vaccinia, and adeno-associated virus.[4] Like the genetic material (DNA or RNA) in viruses, therapeutic DNA can be designed to simply serve as a temporary blueprint that is degraded naturally or (at least theoretically) to enter the host’s genome, becoming a permanent part of the host’s DNA in infected cells.

Non-viral methods present certain advantages over viral methods, such as large scale production and low host immunogenicity. However, non-viral methods initially produced lower levels of transfection and gene expression, and thus lower therapeutic efficacy. Later technology remedied this deficiency[citation needed].

Methods for non-viral gene therapy include the injection of naked DNA, electroporation, the gene gun, sonoporation, magnetofection, the use of oligonucleotides, lipoplexes, dendrimers, and inorganic nanoparticles.

Some of the unsolved problems include:

Three patients’ deaths have been reported in gene therapy trials, putting the field under close scrutiny. The first was that of Jesse Gelsinger in 1999. Jesse Gelsinger died because of immune rejection response.[51] One X-SCID patient died of leukemia in 2003.[9] In 2007, a rheumatoid arthritis patient died from an infection; the subsequent investigation concluded that the death was not related to gene therapy.[52]

In 1972 Friedmann and Roblin authored a paper in Science titled “Gene therapy for human genetic disease?”[53] Rogers (1970) was cited for proposing that exogenous good DNA be used to replace the defective DNA in those who suffer from genetic defects.[54]

In 1984 a retrovirus vector system was designed that could efficiently insert foreign genes into mammalian chromosomes.[55]

The first approved gene therapy clinical research in the US took place on 14 September 1990, at the National Institutes of Health (NIH), under the direction of William French Anderson.[56] Four-year-old Ashanti DeSilva received treatment for a genetic defect that left her with ADA-SCID, a severe immune system deficiency. The defective gene of the patient’s blood cells was replaced by the functional variant. Ashantis immune system was partially restored by the therapy. Production of the missing enzyme was temporarily stimulated, but the new cells with functional genes were not generated. She led a normal life only with the regular injections performed every two months. The effects were successful, but temporary.[57]

Cancer gene therapy was introduced in 1992/93 (Trojan et al. 1993).[58] The treatment of glioblastoma multiforme, the malignant brain tumor whose outcome is always fatal, was done using a vector expressing antisense IGF-I RNA (clinical trial approved by NIH protocolno.1602 November 24, 1993,[59] and by the FDA in 1994). This therapy also represents the beginning of cancer immunogene therapy, a treatment which proves to be effective due to the anti-tumor mechanism of IGF-I antisense, which is related to strong immune and apoptotic phenomena.

In 1992 Claudio Bordignon, working at the Vita-Salute San Raffaele University, performed the first gene therapy procedure using hematopoietic stem cells as vectors to deliver genes intended to correct hereditary diseases.[60] In 2002 this work led to the publication of the first successful gene therapy treatment for adenosine deaminase deficiency (ADA-SCID). The success of a multi-center trial for treating children with SCID (severe combined immune deficiency or “bubble boy” disease) from 2000 and 2002, was questioned when two of the ten children treated at the trial’s Paris center developed a leukemia-like condition. Clinical trials were halted temporarily in 2002, but resumed after regulatory review of the protocol in the US, the United Kingdom, France, Italy, and Germany.[61]

In 1993 Andrew Gobea was born with SCID following prenatal genetic screening. Blood was removed from his mother’s placenta and umbilical cord immediately after birth, to acquire stem cells. The allele that codes for adenosine deaminase (ADA) was obtained and inserted into a retrovirus. Retroviruses and stem cells were mixed, after which the viruses inserted the gene into the stem cell chromosomes. Stem cells containing the working ADA gene were injected into Andrew’s blood. Injections of the ADA enzyme were also given weekly. For four years T cells (white blood cells), produced by stem cells, made ADA enzymes using the ADA gene. After four years more treatment was needed.[62]

Jesse Gelsinger’s death in 1999 impeded gene therapy research in the US.[63][64] As a result, the FDA suspended several clinical trials pending the reevaluation of ethical and procedural practices.[65]

The modified cancer gene therapy strategy of antisense IGF-I RNA (NIH n 1602)[59] using antisense / triple helix anti-IGF-I approach was registered in 2002 by Wiley gene therapy clinical trial – n 635 and 636. The approach has shown promising results in the treatment of six different malignant tumors: glioblastoma, cancers of liver, colon, prostate, uterus, and ovary (Collaborative NATO Science Programme on Gene Therapy USA, France, Poland n LST 980517 conducted by J. Trojan) (Trojan et al., 2012). This anti-gene antisense/triple helix therapy has proven to be efficient, due to the mechanism stopping simultaneously IGF-I expression on translation and transcription levels, strengthening anti-tumor immune and apoptotic phenomena.

Sickle-cell disease can be treated in mice.[66] The mice which have essentially the same defect that causes human cases used a viral vector to induce production of fetal hemoglobin (HbF), which normally ceases to be produced shortly after birth. In humans, the use of hydroxyurea to stimulate the production of HbF temporarily alleviates sickle cell symptoms. The researchers demonstrated this treatment to be a more permanent means to increase therapeutic HbF production.[67]

A new gene therapy approach repaired errors in messenger RNA derived from defective genes. This technique has the potential to treat thalassaemia, cystic fibrosis and some cancers.[68]

Researchers created liposomes 25 nanometers across that can carry therapeutic DNA through pores in the nuclear membrane.[69]

In 2003 a research team inserted genes into the brain for the first time. They used liposomes coated in a polymer called polyethylene glycol, which, unlike viral vectors, are small enough to cross the bloodbrain barrier.[70]

Short pieces of double-stranded RNA (short, interfering RNAs or siRNAs) are used by cells to degrade RNA of a particular sequence. If a siRNA is designed to match the RNA copied from a faulty gene, then the abnormal protein product of that gene will not be produced.[71]

Gendicine is a cancer gene therapy that delivers the tumor suppressor gene p53 using an engineered adenovirus. In 2003, it was approved in China for the treatment of head and neck squamous cell carcinoma.[25]

In March researchers announced the successful use of gene therapy to treat two adult patients for X-linked chronic granulomatous disease, a disease which affects myeloid cells and damages the immune system. The study is the first to show that gene therapy can treat the myeloid system.[72]

In May a team reported a way to prevent the immune system from rejecting a newly delivered gene.[73] Similar to organ transplantation, gene therapy has been plagued by this problem. The immune system normally recognizes the new gene as foreign and rejects the cells carrying it. The research utilized a newly uncovered network of genes regulated by molecules known as microRNAs. This natural function selectively obscured their therapeutic gene in immune system cells and protected it from discovery. Mice infected with the gene containing an immune-cell microRNA target sequence did not reject the gene.

In August scientists successfully treated metastatic melanoma in two patients using killer T cells genetically retargeted to attack the cancer cells.[74]

In November researchers reported on the use of VRX496, a gene-based immunotherapy for the treatment of HIV that uses a lentiviral vector to deliver an antisense gene against the HIV envelope. In a phase I clinical trial, five subjects with chronic HIV infection who had failed to respond to at least two antiretroviral regimens were treated. A single intravenous infusion of autologous CD4 T cells genetically modified with VRX496 was well tolerated. All patients had stable or decreased viral load; four of the five patients had stable or increased CD4 T cell counts. All five patients had stable or increased immune response to HIV antigens and other pathogens. This was the first evaluation of a lentiviral vector administered in a US human clinical trial.[75][76]

In May researchers announced the first gene therapy trial for inherited retinal disease. The first operation was carried out on a 23-year-old British male, Robert Johnson, in early 2007.[77]

Leber’s congenital amaurosis is an inherited blinding disease caused by mutations in the RPE65 gene. The results of a small clinical trial in children were published in April.[11] Delivery of recombinant adeno-associated virus (AAV) carrying RPE65 yielded positive results. In May two more groups reported positive results in independent clinical trials using gene therapy to treat the condition. In all three clinical trials, patients recovered functional vision without apparent side-effects.[11][12][13][14]

In September researchers were able to give trichromatic vision to squirrel monkeys.[78] In November 2009, researchers halted a fatal genetic disorder called adrenoleukodystrophy in two children using a lentivirus vector to deliver a functioning version of ABCD1, the gene that is mutated in the disorder.[79]

An April paper reported that gene therapy addressed achromatopsia (color blindness) in dogs by targeting cone photoreceptors. Cone function and day vision were restored for at least 33 months in two young specimens. The therapy was less efficient for older dogs.[80]

In September it was announced that an 18-year-old male patient in France with beta-thalassemia major had been successfully treated.[81] Beta-thalassemia major is an inherited blood disease in which beta haemoglobin is missing and patients are dependent on regular lifelong blood transfusions.[82] The technique used a lentiviral vector to transduce the human -globin gene into purified blood and marrow cells obtained from the patient in June 2007.[83] The patient’s haemoglobin levels were stable at 9 to 10 g/dL. About a third of the hemoglobin contained the form introduced by the viral vector and blood transfusions were not needed.[83][84] Further clinical trials were planned.[85] Bone marrow transplants are the only cure for thalassemia, but 75% of patients do not find a matching donor.[84]

Cancer immunogene therapy using modified antigene, antisense/triple helix approach was introduced in South America in 2010/11 in La Sabana University, Bogota (Ethical Committee 14 December 2010, no P-004-10). Considering the ethical aspect of gene diagnostic and gene therapy targeting IGF-I, the IGF-I expressing tumors i.e. lung and epidermis cancers were treated (Trojan et al. 2016).[86][87]

In 2007 and 2008, a man (Timothy Ray Brown) was cured of HIV by repeated hematopoietic stem cell transplantation (see also allogeneic stem cell transplantation, allogeneic bone marrow transplantation, allotransplantation) with double-delta-32 mutation which disables the CCR5 receptor. This cure was accepted by the medical community in 2011.[88] It required complete ablation of existing bone marrow, which is very debilitating.

In August two of three subjects of a pilot study were confirmed to have been cured from chronic lymphocytic leukemia (CLL). The therapy used genetically modified T cells to attack cells that expressed the CD19 protein to fight the disease.[20] In 2013, the researchers announced that 26 of 59 patients had achieved complete remission and the original patient had remained tumor-free.[89]

Human HGF plasmid DNA therapy of cardiomyocytes is being examined as a potential treatment for coronary artery disease as well as treatment for the damage that occurs to the heart after myocardial infarction.[90][91]

In 2011 Neovasculgen was registered in Russia as the first-in-class gene-therapy drug for treatment of peripheral artery disease, including critical limb ischemia; it delivers the gene encoding for VEGF.[92][26] Neovasculogen is a plasmid encoding the CMV promoter and the 165 amino acid form of VEGF.[93][94]

The FDA approved Phase 1 clinical trials on thalassemia major patients in the US for 10 participants in July.[95] The study was expected to continue until 2015.[85]

In July 2012, the European Medicines Agency recommended approval of a gene therapy treatment for the first time in either Europe or the United States. The treatment used Alipogene tiparvovec (Glybera) to compensate for lipoprotein lipase deficiency, which can cause severe pancreatitis.[96] The recommendation was endorsed by the European Commission in November 2012[10][27][97][98] and commercial rollout began in late 2014.[99] Alipogene tiparvovec was expected to cost around $1.6 million per treatment in 2012,[100] revised to $1 million in 2015,[101] making it the most expensive medicine in the world at the time.[102] As of 2016, only one person had been treated with drug.[103]

In December 2012, it was reported that 10 of 13 patients with multiple myeloma were in remission “or very close to it” three months after being injected with a treatment involving genetically engineered T cells to target proteins NY-ESO-1 and LAGE-1, which exist only on cancerous myeloma cells.[22]

In March researchers reported that three of five adult subjects who had acute lymphocytic leukemia (ALL) had been in remission for five months to two years after being treated with genetically modified T cells which attacked cells with CD19 genes on their surface, i.e. all B-cells, cancerous or not. The researchers believed that the patients’ immune systems would make normal T-cells and B-cells after a couple of months. They were also given bone marrow. One patient relapsed and died and one died of a blood clot unrelated to the disease.[21]

Following encouraging Phase 1 trials, in April, researchers announced they were starting Phase 2 clinical trials (called CUPID2 and SERCA-LVAD) on 250 patients[104] at several hospitals to combat heart disease. The therapy was designed to increase the levels of SERCA2, a protein in heart muscles, improving muscle function.[105] The FDA granted this a Breakthrough Therapy Designation to accelerate the trial and approval process.[106] In 2016 it was reported that no improvement was found from the CUPID 2 trial.[107]

In July researchers reported promising results for six children with two severe hereditary diseases had been treated with a partially deactivated lentivirus to replace a faulty gene and after 732 months. Three of the children had metachromatic leukodystrophy, which causes children to lose cognitive and motor skills.[108] The other children had Wiskott-Aldrich syndrome, which leaves them to open to infection, autoimmune diseases, and cancer.[109] Follow up trials with gene therapy on another six children with Wiskott-Aldrich syndrome were also reported as promising.[110][111]

In October researchers reported that two children born with adenosine deaminase severe combined immunodeficiency disease (ADA-SCID) had been treated with genetically engineered stem cells 18 months previously and that their immune systems were showing signs of full recovery. Another three children were making progress.[18] In 2014 a further 18 children with ADA-SCID were cured by gene therapy.[112] ADA-SCID children have no functioning immune system and are sometimes known as “bubble children.”[18]

Also in October researchers reported that they had treated six hemophilia sufferers in early 2011 using an adeno-associated virus. Over two years later all six were producing clotting factor.[18][113]

In January researchers reported that six choroideremia patients had been treated with adeno-associated virus with a copy of REP1. Over a six-month to two-year period all had improved their sight.[114][115] By 2016, 32 patients had been treated with positive results and researchers were hopeful the treatment would be long-lasting.[15] Choroideremia is an inherited genetic eye disease with no approved treatment, leading to loss of sight.

In March researchers reported that 12 HIV patients had been treated since 2009 in a trial with a genetically engineered virus with a rare mutation (CCR5 deficiency) known to protect against HIV with promising results.[116][117]

Clinical trials of gene therapy for sickle cell disease were started in 2014.[118][119] There is a need for high quality randomised controlled trials assessing the risks and benefits involved with gene therapy for people with sickle cell disease.[120]

In February LentiGlobin BB305, a gene therapy treatment undergoing clinical trials for treatment of beta thalassemia gained FDA “breakthrough” status after several patients were able to forgo the frequent blood transfusions usually required to treat the disease.[121]

In March researchers delivered a recombinant gene encoding a broadly neutralizing antibody into monkeys infected with simian HIV; the monkeys’ cells produced the antibody, which cleared them of HIV. The technique is named immunoprophylaxis by gene transfer (IGT). Animal tests for antibodies to ebola, malaria, influenza, and hepatitis were underway.[122][123]

In March, scientists, including an inventor of CRISPR, Jennifer Doudna, urged a worldwide moratorium on germline gene therapy, writing “scientists should avoid even attempting, in lax jurisdictions, germline genome modification for clinical application in humans” until the full implications “are discussed among scientific and governmental organizations”.[124][125][126][127]

In October, researchers announced that they had treated a baby girl, Layla Richards, with an experimental treatment using donor T-cells genetically engineered using TALEN to attack cancer cells. One year after the treatment she was still free of her cancer (a highly aggressive form of acute lymphoblastic leukaemia [ALL]).[128] Children with highly aggressive ALL normally have a very poor prognosis and Layla’s disease had been regarded as terminal before the treatment.[129]

In December, scientists of major world academies called for a moratorium on inheritable human genome edits, including those related to CRISPR-Cas9 technologies[130] but that basic research including embryo gene editing should continue.[131]

In April the Committee for Medicinal Products for Human Use of the European Medicines Agency endorsed a gene therapy treatment called Strimvelis[132][133] and the European Commission approved it in June.[134] This treats children born with adenosine deaminase deficiency and who have no functioning immune system. This was the second gene therapy treatment to be approved in Europe.[135]

In October, Chinese scientists reported they had started a trial to genetically modify T-cells from 10 adult patients with lung cancer and reinject the modified T-cells back into their bodies to attack the cancer cells. The T-cells had the PD-1 protein (which stops or slows the immune response) removed using CRISPR-Cas9.[136][137]

A 2016 Cochrane systematic review looking at data from four trials on topical cystic fibrosis transmembrane conductance regulator (CFTR) gene therapy does not support its clinical use as a mist inhaled into the lungs to treat cystic fibrosis patients with lung infections. One of the four trials did find weak evidence that liposome-based CFTR gene transfer therapy may lead to a small respiratory improvement for people with CF. This weak evidence is not enough to make a clinical recommendation for routine CFTR gene therapy.[138]

In February Kite Pharma announced results from a clinical trial of CAR-T cells in around a hundred people with advanced Non-Hodgkin lymphoma.[139]

In March, French scientists reported on clinical research of gene therapy to treat sickle-cell disease.[140]

In August, the FDA approved tisagenlecleucel for acute lymphoblastic leukemia.[141] Tisagenlecleucel is an adoptive cell transfer therapy for B-cell acute lymphoblastic leukemia; T cells from a person with cancer are removed, genetically engineered to make a specific T-cell receptor (a chimeric T cell receptor, or “CAR-T”) that reacts to the cancer, and are administered back to the person. The T cells are engineered to target a protein called CD19 that is common on B cells. This is the first form of gene therapy to be approved in the United States. In October, a similar therapy called axicabtagene ciloleucel was approved for non-Hodgkin lymphoma.[142]

In December the results of using an adeno-associated virus with blood clotting factor VIII to treat nine haemophilia A patients were published. Six of the seven patients on the high dose regime increased the level of the blood clotting VIII to normal levels. The low and medium dose regimes had no effect on the patient’s blood clotting levels.[143][144]

In December, the FDA approved Luxturna, the first in vivo gene therapy, for the treatment of blindness due to Leber’s congenital amaurosis.[145] The price of this treatment was 850,000 US dollars for both eyes.[146][147] CRISPR gene editing technology has also been used on mice to treat deafness due to the DFNA36 mutation, which also affects humans.[148]

Speculated uses for gene therapy include:

Gene Therapy techniques have the potential to provide alternative treatments for those with infertility. Recently, successful experimentation on mice has proven that fertility can be restored by using the gene therapy method, CRISPR.[149] Spermatogenical stem cells from another organism were transplanted into the testes of an infertile male mouse. The stem cells re-established spermatogenesis and fertility.[150]

Athletes might adopt gene therapy technologies to improve their performance.[151] Gene doping is not known to occur, but multiple gene therapies may have such effects. Kayser et al. argue that gene doping could level the playing field if all athletes receive equal access. Critics claim that any therapeutic intervention for non-therapeutic/enhancement purposes compromises the ethical foundations of medicine and sports.[152]

Genetic engineering could be used to cure diseases, but also to change physical appearance, metabolism, and even improve physical capabilities and mental faculties such as memory and intelligence. Ethical claims about germline engineering include beliefs that every fetus has a right to remain genetically unmodified, that parents hold the right to genetically modify their offspring, and that every child has the right to be born free of preventable diseases.[153][154][155] For parents, genetic engineering could be seen as another child enhancement technique to add to diet, exercise, education, training, cosmetics, and plastic surgery.[156][157] Another theorist claims that moral concerns limit but do not prohibit germline engineering.[158]

Possible regulatory schemes include a complete ban, provision to everyone, or professional self-regulation. The American Medical Associations Council on Ethical and Judicial Affairs stated that “genetic interventions to enhance traits should be considered permissible only in severely restricted situations: (1) clear and meaningful benefits to the fetus or child; (2) no trade-off with other characteristics or traits; and (3) equal access to the genetic technology, irrespective of income or other socioeconomic characteristics.”[159]

As early in the history of biotechnology as 1990, there have been scientists opposed to attempts to modify the human germline using these new tools,[160] and such concerns have continued as technology progressed.[161][162] With the advent of new techniques like CRISPR, in March 2015 a group of scientists urged a worldwide moratorium on clinical use of gene editing technologies to edit the human genome in a way that can be inherited.[124][125][126][127] In April 2015, researchers sparked controversy when they reported results of basic research to edit the DNA of non-viable human embryos using CRISPR.[149][163] A committee of the American National Academy of Sciences and National Academy of Medicine gave qualified support to human genome editing in 2017[164][165] once answers have been found to safety and efficiency problems “but only for serious conditions under stringent oversight.”[166]

Regulations covering genetic modification are part of general guidelines about human-involved biomedical research. There are no international treaties which are legally binding in this area, but there are recommendations for national laws from various bodies.

The Helsinki Declaration (Ethical Principles for Medical Research Involving Human Subjects) was amended by the World Medical Association’s General Assembly in 2008. This document provides principles physicians and researchers must consider when involving humans as research subjects. The Statement on Gene Therapy Research initiated by the Human Genome Organization (HUGO) in 2001 provides a legal baseline for all countries. HUGOs document emphasizes human freedom and adherence to human rights, and offers recommendations for somatic gene therapy, including the importance of recognizing public concerns about such research.[167]

No federal legislation lays out protocols or restrictions about human genetic engineering. This subject is governed by overlapping regulations from local and federal agencies, including the Department of Health and Human Services, the FDA and NIH’s Recombinant DNA Advisory Committee. Researchers seeking federal funds for an investigational new drug application, (commonly the case for somatic human genetic engineering,) must obey international and federal guidelines for the protection of human subjects.[168]

NIH serves as the main gene therapy regulator for federally funded research. Privately funded research is advised to follow these regulations. NIH provides funding for research that develops or enhances genetic engineering techniques and to evaluate the ethics and quality in current research. The NIH maintains a mandatory registry of human genetic engineering research protocols that includes all federally funded projects.

An NIH advisory committee published a set of guidelines on gene manipulation.[169] The guidelines discuss lab safety as well as human test subjects and various experimental types that involve genetic changes. Several sections specifically pertain to human genetic engineering, including Section III-C-1. This section describes required review processes and other aspects when seeking approval to begin clinical research involving genetic transfer into a human patient.[170] The protocol for a gene therapy clinical trial must be approved by the NIH’s Recombinant DNA Advisory Committee prior to any clinical trial beginning; this is different from any other kind of clinical trial.[169]

As with other kinds of drugs, the FDA regulates the quality and safety of gene therapy products and supervises how these products are used clinically. Therapeutic alteration of the human genome falls under the same regulatory requirements as any other medical treatment. Research involving human subjects, such as clinical trials, must be reviewed and approved by the FDA and an Institutional Review Board.[171][172]

Gene therapy is the basis for the plotline of the film I Am Legend[173] and the TV show Will Gene Therapy Change the Human Race?.[174] In 1994, gene therapy was a plot element in The Erlenmeyer Flask, The X-Files’ first season finale. It is also used in Stargate as a means of allowing humans to use Ancient technology.[175]

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Gene therapy – Wikipedia

Gene Therapy – Sumanas, Inc.

Gene Therapy

A few years ago, a clinical trial began in France in the hope of curing children with a type of genetic immune deficiency called SCID-X1. Children with this disease have a defective gene, called gamma-c, which prevents a subset of the cells of the immune system from forming, and predisposes the children to life-threatening infections. In an attempt to cure the childrenwho would otherwise die at a young agephysicians used gene therapy to provide them with normal gamma-c genes.

This particular trial has had striking success as well as tragedy. Eight of the eleven children are currently thriving. However, in two cases the therapy successfully introduced gamma-c genes, but these children have since developed leukemia. In both children, a gamma-c gene inserted next to another gene, called LMO2. The LMO2 gene has previously been linked to leukemia, and scientists speculate that the insertion of the gamma-c gene next to LMO2 may have overstimulated the gene, causing T cells to proliferate in excess. An LMO2 effect, in combination with the proliferation-inducing effects of the gamma-c gene itself, may be the cause of the leukemia in these two patients. Scientists are still investigating other possible causes.

From this single trial, it is clear that gene therapy holds significant promise, yet it is also clear that it poses significant risks. To learn more about the application of gene therapy in SCID, view the accompanying animation.

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Gene Therapy – Sumanas, Inc.

Gene Therapy Net – News, Conferences, Vectors, Literature …

Posted on: 22 March 2018, source: GizmodoOn Tuesday, a 13-year-old boy from New Jersey was at the center of medical history as he became the first person in the US to receive an FDA-approved gene therapy for an inherited disease. The event marks the beginning of a new era of medicine, one in which devastating genetic conditions that we are born with can be simply edited out of our DNA with the help of modern biomedical technologies. The therapy, Luxturna, from Spark Therepeutics, was approved by the FDA in December to treat a rare, inherited form of blindness. Its price tag, set at $850,000or $425,000 per eyemade it the most expensive drug in the US and sparked mass sticker-shock. But the therapy, which in high-profile clinical trials has allowed patients to see the stars for the first times, also offered the almost miraculous possibility of giving sight to the blind.

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Gene Therapy Net – News, Conferences, Vectors, Literature …

Gene Therapy Retrovirus Vectors Explained

A retrovirus is any virus belonging to the viral family Retroviridae. All The genetic material in retroviruses is in the form of RNA molecules, while the genetic material of their hosts is in the form of DNA. When a retrovirus infects a host cell, it will introduce its RNA together with some enzymes into the cell. This RNA molecule from the retrovirus must produce a DNA copy from its RNA molecule before it can be considered part of the genetic material of the host cell. Retrovirus genomes commonly contain these three open reading frames that encode for proteins that can be found in the mature virus. Group-specific antigen (gag) codes for core and structural proteins of the virus, polymerase (pol) codes for reverse transcriptase, protease and integrase, and envelope (env) codes for the retroviral coat proteins (see figure 1). Figure 1. Genome organisation of retroviruses.

The process of producing a DNA copy from an RNA molecule is termed reverse transcription. It is carried out by one of the enzymes carried in the virus, called reverse transcriptase. After this DNA copy is produced and is free in the nucleus of the host cell, it must be incorporated into the genome of the host cell. That is, it must be inserted into the large DNA molecules in the cell (the chromosomes). This process is done by another enzyme carried in the virus called integrase (see figure 2).

Now that the genetic material of the virus is incorporated and has become part of the genetic material of the host cell, we can say that the host cell is now modified to contain a new gene. If this host cell divides later, its descendants will all contain the new genes. Sometimes the genes of the retrovirus do not express their information immediately.

Retroviral vectors are created by removal op the retroviral gag, pol, and env genes. These are replaced by the therapeutic gene. In order to produce vector particles a packaging cell is essential. Packaging cell lines provide all the viral proteins required for capsid production and the virion maturation of the vector. These packaging cell lines have been made so that they contain the gag, pol and env genes. Early packaging cell lines contained replication competent retroviral genomes and a single recombination event between this genome and the retroviral DNA vector could result in the production of a wild type virus. Following insertion of the desired gene into in the retroviral DNA vector, and maintainance of the proper packaging cell line, it is now a simple matter to prepare retroviral vectors (see figure 3).

One of the problems of gene therapy using retroviruses is that the integrase enzyme can insert the genetic material of the virus in any arbitrary position in the genome of the host. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted (insertional mutagenesis). If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur. This problem has recently begun to be addressed by utilizing zinc finger nucleases or by including certain sequences such as the beta-globin locus control region to direct the site of integration to specific chromosomal sites.

Gene therapy trials to treat severe combined immunodeficiency (SCID) were halted or restricted in the USA when leukemia was reported in three of eleven patients treated in the French X-linked SCID (X-SCID) gene therapy trial. Ten X-SCID patients treated in England have not presented leukemia to date and have had similar success in immune reconstitution. Gene therapy trials to treat SCID due to deficiency of the Adenosine Deaminase (ADA) enzyme continue with relative success in the USA, Italy and Japan.

As a reaction to the adverse events in the French X-SCID gene therapy trial, the Recombinant DNA Advisory Committee (RAC) sent a letter to Principal Investigators Conveying RAC Recommendations in 2003. In addition, the RAC published conclusions and recommendations of the RAC Gene Transfer Safety Symposium in 2005. A joint working party of the Gene Therapy Advisory Committee and the Committee on Safety of Medicines (CSM) in the UK lead to the publication of an updated recommendations of the GTAC/CSM working party on retroviruses in 2005.

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Gene Therapy Retrovirus Vectors Explained

Gene therapy – Mayo Clinic

Overview

Gene therapy involves altering the genes inside your body’s cells in an effort to treat or stop disease.

Genes contain your DNA the code that controls much of your body’s form and function, from making you grow taller to regulating your body systems. Genes that don’t work properly can cause disease.

Gene therapy replaces a faulty gene or adds a new gene in an attempt to cure disease or improve your body’s ability to fight disease. Gene therapy holds promise for treating a wide range of diseases, such as cancer, cystic fibrosis, heart disease, diabetes, hemophilia and AIDS.

Researchers are still studying how and when to use gene therapy. Currently, in the United States, gene therapy is available only as part of a clinical trial.

Gene therapy is used to correct defective genes in order to cure a disease or help your body better fight disease.

Researchers are investigating several ways to do this, including:

Gene therapy has some potential risks. A gene can’t easily be inserted directly into your cells. Rather, it usually has to be delivered using a carrier, called a vector.

The most common gene therapy vectors are viruses because they can recognize certain cells and carry genetic material into the cells’ genes. Researchers remove the original disease-causing genes from the viruses, replacing them with the genes needed to stop disease.

This technique presents the following risks:

The gene therapy clinical trials underway in the U.S. are closely monitored by the Food and Drug Administration and the National Institutes of Health to ensure that patient safety issues are a top priority during research.

Currently, the only way for you to receive gene therapy is to participate in a clinical trial. Clinical trials are research studies that help doctors determine whether a gene therapy approach is safe for people. They also help doctors understand the effects of gene therapy on the body.

Your specific procedure will depend on the disease you have and the type of gene therapy being used.

For example, in one type of gene therapy:

Viruses aren’t the only vectors that can be used to carry altered genes into your body’s cells. Other vectors being studied in clinical trials include:

The possibilities of gene therapy hold much promise. Clinical trials of gene therapy in people have shown some success in treating certain diseases, such as:

But several significant barriers stand in the way of gene therapy becoming a reliable form of treatment, including:

Gene therapy continues to be a very important and active area of research aimed at developing new, effective treatments for a variety of diseases.

Explore Mayo Clinic studies testing new treatments, interventions and tests as a means to prevent, detect, treat or manage this disease.

Dec. 29, 2017

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Gene therapy – Mayo Clinic

Vectors in gene therapy – Wikipedia

Gene therapy utilizes the delivery of DNA into cells, which can be accomplished by several methods, summarized below. The two major classes of methods are those that use recombinant viruses (sometimes called biological nanoparticles or viral vectors) and those that use naked DNA or DNA complexes (non-viral methods).

All viruses bind to their hosts and introduce their genetic material into the host cell as part of their replication cycle. This genetic material contains basic ‘instructions’ of how to produce more copies of these viruses, hacking the body’s normal production machinery to serve the needs of the virus. The host cell will carry out these instructions and produce additional copies of the virus, leading to more and more cells becoming infected. Some types of viruses insert their genome into the host’s cytoplasm, but do not actually enter the cell. Others penetrate the cell membrane disguised as protein molecules and enter the cell.

There are two main types of virus infection: lytic and lysogenic. Shortly after inserting its DNA, viruses of the lytic cycle quickly produce more viruses, burst from the cell and infect more cells. Lysogenic viruses integrate their DNA into the DNA of the host cell and may live in the body for many years before responding to a trigger. The virus reproduces as the cell does and does not inflict bodily harm until it is triggered. The trigger releases the DNA from that of the host and employs it to create new viruses.

The genetic material in retroviruses is in the form of RNA molecules, while the genetic material of their hosts is in the form of DNA. When a retrovirus infects a host cell, it will introduce its RNA together with some enzymes, namely reverse transcriptase and integrase, into the cell. This RNA molecule from the retrovirus must produce a DNA copy from its RNA molecule before it can be integrated into the genetic material of the host cell. The process of producing a DNA copy from an RNA molecule is termed reverse transcription. It is carried out by one of the enzymes carried in the virus, called reverse transcriptase. After this DNA copy is produced and is free in the nucleus of the host cell, it must be incorporated into the genome of the host cell. That is, it must be inserted into the large DNA molecules in the cell (the chromosomes). This process is done by another enzyme carried in the virus called integrase.

Now that the genetic material of the virus has been inserted, it can be said that the host cell has been modified to contain new genes. If this host cell divides later, its descendants will all contain the new genes. Sometimes the genes of the retrovirus do not express their information immediately.

One of the problems of gene therapy using retroviruses is that the integrase enzyme can insert the genetic material of the virus into any arbitrary position in the genome of the host; it randomly inserts the genetic material into a chromosome. If genetic material happens to be inserted in the middle of one of the original genes of the host cell, this gene will be disrupted (insertional mutagenesis). If the gene happens to be one regulating cell division, uncontrolled cell division (i.e., cancer) can occur. This problem has recently begun to be addressed by utilizing zinc finger nucleases[1] or by including certain sequences such as the beta-globin locus control region to direct the site of integration to specific chromosomal sites.

Gene therapy trials using retroviral vectors to treat X-linked severe combined immunodeficiency (X-SCID) represent the most successful application of gene therapy to date. More than twenty patients have been treated in France and Britain, with a high rate of immune system reconstitution observed. Similar trials were restricted or halted in the USA when leukemia was reported in patients treated in the French X-SCID gene therapy trial.[citation needed] To date, four children in the French trial and one in the British trial have developed leukemia as a result of insertional mutagenesis by the retroviral vector. All but one of these children responded well to conventional anti-leukemia treatment. Gene therapy trials to treat SCID due to deficiency of the Adenosine Deaminase (ADA) enzyme (one form of SCID)[2] continue with relative success in the USA, Britain, Ireland, Italy and Japan.

Adenoviruses are viruses that carry their genetic material in the form of double-stranded DNA. They cause respiratory, intestinal, and eye infections in humans (especially the common cold). When these viruses infect a host cell, they introduce their DNA molecule into the host. The genetic material of the adenoviruses is not incorporated (transient) into the host cell’s genetic material. The DNA molecule is left free in the nucleus of the host cell, and the instructions in this extra DNA molecule are transcribed just like any other gene. The only difference is that these extra genes are not replicated when the cell is about to undergo cell division so the descendants of that cell will not have the extra gene. As a result, treatment with the adenovirus will require readministration in a growing cell population although the absence of integration into the host cell’s genome should prevent the type of cancer seen in the SCID trials. This vector system has been promoted for treating cancer and indeed the first gene therapy product to be licensed to treat cancer, Gendicine, is an adenovirus. Gendicine, an adenoviral p53-based gene therapy was approved by the Chinese food and drug regulators in 2003 for treatment of head and neck cancer. Advexin, a similar gene therapy approach from Introgen, was turned down by the US Food and Drug Administration (FDA) in 2008.

Concerns about the safety of adenovirus vectors were raised after the 1999 death of Jesse Gelsinger while participating in a gene therapy trial. Since then, work using adenovirus vectors has focused on genetically crippled versions of the virus.

The viral vectors described above have natural host cell populations that they infect most efficiently. Retroviruses have limited natural host cell ranges, and although adenovirus and adeno-associated virus are able to infect a relatively broader range of cells efficiently, some cell types are refractory to infection by these viruses as well. Attachment to and entry into a susceptible cell is mediated by the protein envelope on the surface of a virus. Retroviruses and adeno-associated viruses have a single protein coating their membrane, while adenoviruses are coated with both an envelope protein and fibers that extend away from the surface of the virus. The envelope proteins on each of these viruses bind to cell-surface molecules such as heparin sulfate, which localizes them upon the surface of the potential host, as well as with the specific protein receptor that either induces entry-promoting structural changes in the viral protein, or localizes the virus in endosomes wherein acidification of the lumen induces this refolding of the viral coat. In either case, entry into potential host cells requires a favorable interaction between a protein on the surface of the virus and a protein on the surface of the cell. For the purposes of gene therapy, one might either want to limit or expand the range of cells susceptible to transduction by a gene therapy vector. To this end, many vectors have been developed in which the endogenous viral envelope proteins have been replaced by either envelope proteins from other viruses, or by chimeric proteins. Such chimera would consist of those parts of the viral protein necessary for incorporation into the virion as well as sequences meant to interact with specific host cell proteins. Viruses in which the envelope proteins have been replaced as described are referred to as pseudotyped viruses. For example, the most popular retroviral vector for use in gene therapy trials has been the lentivirus Simian immunodeficiency virus coated with the envelope proteins, G-protein, from Vesicular stomatitis virus. This vector is referred to as VSV G-pseudotyped lentivirus, and infects an almost universal set of cells. This tropism is characteristic of the VSV G-protein with which this vector is coated. Many attempts have been made to limit the tropism of viral vectors to one or a few host cell populations. This advance would allow for the systemic administration of a relatively small amount of vector. The potential for off-target cell modification would be limited, and many concerns from the medical community would be alleviated. Most attempts to limit tropism have used chimeric envelope proteins bearing antibody fragments. These vectors show great promise for the development of “magic bullet” gene therapies.

A replication-competent vector called ONYX-015 is used in replicating tumor cells. It was found that in the absence of the E1B-55Kd viral protein, adenovirus caused very rapid apoptosis of infected, p53(+) cells, and this results in dramatically reduced virus progeny and no subsequent spread. Apoptosis was mainly the result of the ability of EIA to inactivate p300. In p53(-) cells, deletion of E1B 55kd has no consequence in terms of apoptosis, and viral replication is similar to that of wild-type virus, resulting in massive killing of cells.

A replication-defective vector deletes some essential genes. These deleted genes are still necessary in the body so they are replaced with either a helper virus or a DNA molecule.

[3]

Replication-defective vectors always contain a transfer construct. The transfer construct carries the gene to be transduced or transgene. The transfer construct also carries the sequences which are necessary for the general functioning of the viral genome: packaging sequence, repeats for replication and, when needed, priming of reverse transcription. These are denominated cis-acting elements, because they need to be on the same piece of DNA as the viral genome and the gene of interest. Trans-acting elements are viral elements, which can be encoded on a different DNA molecule. For example, the viral structural proteins can be expressed from a different genetic element than the viral genome.

[3]

The Herpes simplex virus is a human neurotropic virus. This is mostly examined for gene transfer in the nervous system. The wild type HSV-1 virus is able to infect neurons and evade the host immune response, but may still become reactivated and produce a lytic cycle of viral replication. Therefore, it is typical to use mutant strains of HSV-1 that are deficient in their ability to replicate. Though the latent virus is not transcriptionally apparent, it does possess neuron specific promoters that can continue to function normally[further explanation needed]. Antibodies to HSV-1 are common in humans, however complications due to herpes infection are somewhat rare.[4] Caution for rare cases of encephalitis must be taken and this provides some rationale to using HSV-2 as a viral vector as it generally has tropism for neuronal cells innervating the urogenital area of the body and could then spare the host of severe pathology in the brain.

Non-viral methods present certain advantages over viral methods, with simple large scale production and low host immunogenicity being just two. Previously, low levels of transfection and expression of the gene held non-viral methods at a disadvantage; however, recent advances in vector technology have yielded molecules and techniques with transfection efficiencies similar to those of viruses.[5]

This is the simplest method of non-viral transfection. Clinical trials carried out of intramuscular injection of a naked DNA plasmid have occurred with some success; however, the expression has been very low in comparison to other methods of transfection. In addition to trials with plasmids, there have been trials with naked PCR product, which have had similar or greater success. Cellular uptake of naked DNA is generally inefficient. Research efforts focusing on improving the efficiency of naked DNA uptake have yielded several novel methods, such as electroporation, sonoporation, and the use of a “gene gun”, which shoots DNA coated gold particles into the cell using high pressure gas.[6]

Electroporation is a method that uses short pulses of high voltage to carry DNA across the cell membrane. This shock is thought to cause temporary formation of pores in the cell membrane, allowing DNA molecules to pass through. Electroporation is generally efficient and works across a broad range of cell types. However, a high rate of cell death following electroporation has limited its use, including clinical applications.

More recently a newer method of electroporation, termed electron-avalanche transfection, has been used in gene therapy experiments. By using a high-voltage plasma discharge, DNA was efficiently delivered following very short (microsecond) pulses. Compared to electroporation, the technique resulted in greatly increased efficiency and less cellular damage.

The use of particle bombardment, or the gene gun, is another physical method of DNA transfection. In this technique, DNA is coated onto gold particles and loaded into a device which generates a force to achieve penetration of the DNA into the cells, leaving the gold behind on a “stopping” disk.

Sonoporation uses ultrasonic frequencies to deliver DNA into cells. The process of acoustic cavitation is thought to disrupt the cell membrane and allow DNA to move into cells.

In a method termed magnetofection, DNA is complexed to magnetic particles, and a magnet is placed underneath the tissue culture dish to bring DNA complexes into contact with a cell monolayer.

Hydrodynamic delivery involves rapid injection of a high volume of a solution into vasculature (such as into the inferior vena cava, bile duct, or tail vein). The solution contains molecules that are to be inserted into cells, such as DNA plasmids or siRNA, and transfer of these molecules into cells is assisted by the elevated hydrostatic pressure caused by the high volume of injected solution.[7][8][9]

The use of synthetic oligonucleotides in gene therapy is to deactivate the genes involved in the disease process. There are several methods by which this is achieved. One strategy uses antisense specific to the target gene to disrupt the transcription of the faulty gene. Another uses small molecules of RNA called siRNA to signal the cell to cleave specific unique sequences in the mRNA transcript of the faulty gene, disrupting translation of the faulty mRNA, and therefore expression of the gene. A further strategy uses double stranded oligodeoxynucleotides as a decoy for the transcription factors that are required to activate the transcription of the target gene. The transcription factors bind to the decoys instead of the promoter of the faulty gene, which reduces the transcription of the target gene, lowering expression. Additionally, single stranded DNA oligonucleotides have been used to direct a single base change within a mutant gene. The oligonucleotide is designed to anneal with complementarity to the target gene with the exception of a central base, the target base, which serves as the template base for repair. This technique is referred to as oligonucleotide mediated gene repair, targeted gene repair, or targeted nucleotide alteration.

To improve the delivery of the new DNA into the cell, the DNA must be protected from damage and positively charged. Initially, anionic and neutral lipids were used for the construction of lipoplexes for synthetic vectors. However, in spite of the facts that there is little toxicity associated with them, that they are compatible with body fluids and that there was a possibility of adapting them to be tissue specific; they are complicated and time consuming to produce so attention was turned to the cationic versions.

Cationic lipids, due to their positive charge, were first used to condense negatively charged DNA molecules so as to facilitate the encapsulation of DNA into liposomes. Later it was found that the use of cationic lipids significantly enhanced the stability of lipoplexes. Also as a result of their charge, cationic liposomes interact with the cell membrane, endocytosis was widely believed as the major route by which cells uptake lipoplexes. Endosomes are formed as the results of endocytosis, however, if genes can not be released into cytoplasm by breaking the membrane of endosome, they will be sent to lysosomes where all DNA will be destroyed before they could achieve their functions. It was also found that although cationic lipids themselves could condense and encapsulate DNA into liposomes, the transfection efficiency is very low due to the lack of ability in terms of endosomal escaping. However, when helper lipids (usually electroneutral lipids, such as DOPE) were added to form lipoplexes, much higher transfection efficiency was observed. Later on, it was figured out that certain lipids have the ability to destabilize endosomal membranes so as to facilitate the escape of DNA from endosome, therefore those lipids are called fusogenic lipids. Although cationic liposomes have been widely used as an alternative for gene delivery vectors, a dose dependent toxicity of cationic lipids were also observed which could limit their therapeutic usages.

The most common use of lipoplexes has been in gene transfer into cancer cells, where the supplied genes have activated tumor suppressor control genes in the cell and decrease the activity of oncogenes. Recent studies have shown lipoplexes to be useful in transfecting respiratory epithelial cells.

Polymersomes are synthetic versions of liposomes (vesicles with a lipid bilayer), made of amphiphilic block copolymers. They can encapsulate either hydrophilic or hydrophobic contents and can be used to deliver cargo such as DNA, proteins, or drugs to cells. Advantages of polymersomes over liposomes include greater stability, mechanical strength, blood circulation time, and storage capacity.[10][11][12]

Complexes of polymers with DNA are called polyplexes. Most polyplexes consist of cationic polymers and their fabrication is based on self-assembly by ionic interactions. One important difference between the methods of action of polyplexes and lipoplexes is that polyplexes cannot directly release their DNA load into the cytoplasm. As a result, co-transfection with endosome-lytic agents such as inactivated adenovirus was required to facilitate nanoparticle escape from the endocytic vesicle made during particle uptake. However, a better understanding of the mechanisms by which DNA can escape from endolysosomal pathway, i.e. proton sponge effect,[13] has triggered new polymer synthesis strategies such as incorporation of protonable residues in polymer backbone and has revitalized research on polycation-based systems.[14]

Due to their low toxicity, high loading capacity, and ease of fabrication, polycationic nanocarriers demonstrate great promise compared to their rivals such as viral vectors which show high immunogenicity and potential carcinogenicity, and lipid-based vectors which cause dose dependence toxicity. Polyethyleneimine[15] and chitosan are among the polymeric carriers that have been extensively studies for development of gene delivery therapeutics. Other polycationic carriers such as poly(beta-amino esters)[16] and polyphosphoramidate[17] are being added to the library of potential gene carriers. In addition to the variety of polymers and copolymers, the ease of controlling the size, shape, surface chemistry of these polymeric nano-carriers gives them an edge in targeting capability and taking advantage of enhanced permeability and retention effect.[18]

A dendrimer is a highly branched macromolecule with a spherical shape. The surface of the particle may be functionalized in many ways and many of the properties of the resulting construct are determined by its surface.

In particular it is possible to construct a cationic dendrimer, i.e. one with a positive surface charge. When in the presence of genetic material such as DNA or RNA, charge complimentarity leads to a temporary association of the nucleic acid with the cationic dendrimer. On reaching its destination the dendrimer-nucleic acid complex is then taken into the cell via endocytosis.

In recent years the benchmark for transfection agents has been cationic lipids. Limitations of these competing reagents have been reported to include: the lack of ability to transfect some cell types, the lack of robust active targeting capabilities, incompatibility with animal models, and toxicity. Dendrimers offer robust covalent construction and extreme control over molecule structure, and therefore size. Together these give compelling advantages compared to existing approaches.

Producing dendrimers has historically been a slow and expensive process consisting of numerous slow reactions, an obstacle that severely curtailed their commercial development. The Michigan-based company Dendritic Nanotechnologies discovered a method to produce dendrimers using kinetically driven chemistry, a process that not only reduced cost by a magnitude of three, but also cut reaction time from over a month to several days. These new “Priostar” dendrimers can be specifically constructed to carry a DNA or RNA payload that transfects cells at a high efficiency with little or no toxicity.[citation needed]

Inorganic nanoparticles, such as gold, silica, iron oxide (ex. magnetofection) and calcium phosphates have been shown to be capable of gene delivery.[19] Some of the benefits of inorganic vectors is in their storage stability, low manufacturing cost and often time, low immunogenicity, and resistance to microbial attack. Nanosized materials less than 100nm have been shown to efficiently trap the DNA or RNA and allows its escape from the endosome without degradation. Inorganics have also been shown to exhibit improved in vitro transfection for attached cell lines due to their increased density and preferential location on the base of the culture dish. Quantum dots have also been used successfully and permits the coupling of gene therapy with a stable fluorescence marker. Engineered organic nanoparticles are also under development, which could be used for co-delivery of genes and therapeutic agents.[20]

Cell-penetrating peptides (CPPs), also known as peptide transduction domains (PTDs), are short peptides (

CPP cargo can be directed into specific cell organelles by incorporating localization sequences into CPP sequences. For example, nuclear localization sequences are commonly used to guide CPP cargo into the nucleus.[23] For guidance into mitochondria, a mitochondrial targeting sequence can be used; this method is used in protofection (a technique that allows for foreign mitochondrial DNA to be inserted into cells’ mitochondria).[24][25]

Due to every method of gene transfer having shortcomings, there have been some hybrid methods developed that combine two or more techniques. Virosomes are one example; they combine liposomes with an inactivated HIV or influenza virus. This has been shown to have more efficient gene transfer in respiratory epithelial cells than either viral or liposomal methods alone. Other methods involve mixing other viral vectors with cationic lipids or hybridising viruses.

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Vectors in gene therapy – Wikipedia

Gene Therapy | Pfizer: One of the world’s premier …

Gene therapy is a technology aimed at correcting or fixing a gene that may be defective. This exciting and potentially transformative area of research is focused on the development of potential treatments for monogenic diseases, or diseases that are caused by a defect in one gene.

The technology involves the introduction of genetic material (DNA or RNA) into the body, often through delivering a corrected copy of a gene to a patients cells to compensate for a defective one, using a viral vector.

The technology involves the introduction of genetic material (DNA or RNA) into the body, often through delivering a corrected copy of a gene to a patients cells to compensate for a defective one, using a viral vector.

Viral vectors can be developed using adeno-associated virus (AAV), a naturally occurring virus which has been adapted for gene therapy use. Its ability to deliver genetic material to a wide range of tissues makes AAV vectors useful for transferring therapeutic genes into target cells. Gene therapy research holds tremendous promise in leading to the possible development of highly-specialized, potentially one-time delivery treatments for patients suffering from rare, monogenic diseases.

Pfizer aims to build an industry-leading gene therapy platform with a strategy focused on establishing a transformational portfolio through in-house capabilities, and enhancing those capabilities through strategic collaborations, as well as potential licensing and M&A activities.

We’re working to access the most effective vector designs available to build a robust clinical stage portfolio, and employing a scalable manufacturing approach, proprietary cell lines and sophisticated analytics to support clinical development.

In addition, we’re collaborating with some of the foremost experts in this field, through collaborations with Spark Therapeutics, Inc., on a potentially transformative gene therapy treatment for hemophilia B, which received Breakthrough Therapy designation from the US Food and Drug Administration, and 4D Molecular Therapeutics to discover and develop targeted next-generation AAV vectors for cardiac disease.

Gene therapy holds the promise of bringing true disease modification for patients suffering from devastating diseases, a promise were working to seeing become a reality in the years to come.

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Gene Therapy | Pfizer: One of the world’s premier …


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