The US Food and Drug Administration has granted Abbott permission to market its blockbuster rheumatoid arthritis drug Humira as a treatment for the skin condition psoriasis.

Specifically, US regulators have approved the use of the anti-inflammatory injectable in adult patients with moderate-to-severe chronic plaque psoriasis, when other systemic therapies are medically not appropriate, the company said on Friday.

Humira (adalimumab), which already pulls in sales of over $3 billion a year, was first approved in 2003 for RA but has since been cleared for treating psoriatic arthritis and ankylosing spondylitis. It is already available in Europe for psoriasis and the company is expecting additional peak sales of around $500 million for the indication, a spokesperson told Reuters.

The approval of Humira is based on data from more than 1,400 adult patients in two pivotal trials - REVEAL and CHAMPION – which showed that, in three out of four patients, the agent was able to achieve 75% clearance or better at week 16 of treatment versus placebo. Furthermore, the safety profile of the drug was similar to that seen in trials of patients in its other approved indications.

Psoriasis affects an estimated 125 million people worldwide, and around 25% of these suffer from moderate-to-severe disease, and the drug’s approval offers dermatologists an “important new therapeutic option that has been shown to help alleviate a range of psoriasis signs and symptoms, including redness, scaling and itching, in many psoriasis patients”, remarked Alan Menter, chairman of the division of dermatology at the Baylor University Medical Center in Dallas.