The Novartis headquarters in Basel, Switzerland.

ZURICH--Swiss pharmaceutical company Novartis AG said Friday that it won approval in Japan for a new psoriasis drug, the first country to give the treatment a green light for commercialization.

Novartis NOVN, -1.28% said secukinumab, marketed as Cosentyx, is approved in the country to treat psoriasis vulgaris and psoriatic arthritis in patients who dont respond to other medication.

The drug is seen by some analysts as a potential blockbuster, industry jargon for medicines that generate more than $1 billion in sales annually. Demand for new treatments for psoriasis and related diseases is high.

Psoriasis is a chronic disease that is characterized by thick and extensive skin lesions. It causes itching, scaling and pain. Psoriatic arthritis causes joint pain, stiffness and irreversible joint damage.

Cosentyx inhibits the action of a protein found in high concentrations in skin affected by psoriasis, Novartis said.

An expanded version of this report appears at WSJ.com.

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The Wall Street Journal: Novartis psoriasis drug approved in Japan