By Deena Beasley and Bill Berkrot

(Reuters) – Celgene Corp’s experimental drug apremilast proved to be more effective than a dummy pill for psoriasis patients in a late-stage study, clearing the way for the company to file for U.S. regulatory approval in the second half of 2013.

Celgene said 59 percent of patients in the 844-patient trial achieved a 50 percent improvement in symptoms at 16 weeks, using a standard score of the severity and extent of psoriasis, compared with 17 percent of placebo patients. A 75 percent improvement in symptoms was seen in 33 percent of the treatment group and 5 percent of the placebo group.

Apremilast is a pill that inhibits an enzyme known as phosphodiesterase 4, or PDE4, and acts to damp down inflammation.

Celgene said previously it planned to file for Food and Drug Administration approval of the drug as a treatment for psoriatic arthritis in the first quarter of this year.

Side effects were consistent with those seen in earlier trials of the drug, with the most common being diarrhea and nausea.

Celgene said no cases of tuberculosis or lymphoma were observed through Week 16, and there was no increase in risk of cardiovascular events or serious opportunistic infection.

“From a physician’s perspective, this can definitely be a first-line therapy because of the excellent risk/benefit profile,” said Dr. Richard Langley, director of dermatology research at Dalhousie University in Halifax, and one of the study’s lead investigators. “I think the patient acceptance of this drug and the physician acceptance is going to be extremely high.”

He noted that most psoriasis patients are currently treated with methotrexate, which can cause serious side effects.

Newer biologic drugs used to treat psoriasis, which include Amgen Inc’s Enbrel and AbbVie Inc’s Humira, can make patients more susceptible to infection, Dr. Langley said.