UPDATE 1-US FDA extends review of J&J psoriasis drug

(Adds details, company statement, background)

LOS ANGELES, May 26 (Reuters) - U.S. regulators have extended for a second time their review of Johnson & Johnson's (JNJ.N) experimental psoriasis drug, named Stelara, the company said on Tuesday.

J&J said the deadline for a decision by the Food and Drug Administration was extended by three months and the agency has requested no additional clinical trials.

An FDA advisory committee last June recommended that the drug, also known as ustekinumab, be approved, but the agency said in December that would hold off on making a decision on the marketing application until it received certain risk-mitigation information.

J&J said it responded to that request in January.

"We remain focused on collaboration with the FDA and providing the necessary information to support the review and approval of Stelara for the treatment of adults with moderate to severe plaque psoriasis," Jay Siegel, J&J's chief biotechnology officer, said in a statement.

Psoriasis, a condition in which itchy red plaques accumulate on the surface of the skin, is caused by an overproduction of skin cells. It affects an estimated 7.5 million patients in the United States, J&J said.

Ustekinumab, a monoclonal antibody which was highly effective in treating psoriasis in clinical trials, is given by infrequent injections and works by taming two immune system proteins called interleukin-12 (IL-12) and interleukin-23 (IL-23) that are linked to inflammation.

It was well tolerated in two large trials, with generally mild side effects that did not require adjustments in the medicine.

By contrast, current treatments -- including Wyeth's WYE.N leading injectable Enbrel, Abbott Laboratories' (ABT.N) injectable Humira and J&J's older Remicade medicine that is given by intravenous infusion -- can increase risk of infection and reactivate tuberculosis. (Reporting by Deena Beasley; Editing by Tim Dobbyn)