Washington Editor

Poor preliminary Phase II results of Raptiva in psoriatic arthritis patients caused slight dips in Genentech Inc. and XOMA Ltd.'s value.

Genentech, still flying high on the success of its colorectal cancer drug, Avastin, didn't take the news too badly. Its stock (NYSE:DNA) lost only $2.71 to close at $102.14. But XOMA (NASDAQ:XOMA), a smaller firm located in Berkeley, Calif., lost 13.2 percent of its value, or 68 cents, to close at $4.47.

Monday morning Laura Zobkiw, XOMA's spokeswoman, told BioWorld Today the company is disappointed in the preliminary results, but continues to have faith in Raptiva, an FDA-approved treatment for chronic moderate to severe plaque psoriasis in adults age 18 or older who are candidates for systemic therapy or phototherapy. (See BioWorld Today, Oct. 29, 2003.)

The 107-patient Phase II study did not reach statistical significance at 12 weeks regarding the primary endpoint, an American College of Rheumatology (ACR) 20 response. An ACR 20 response indicates at least a 20 percent improvement in an individual's signs and symptoms of arthritis.

Raptiva (efalizumab), an immunosuppressive agent, was approved in late October and launched just before Thanksgiving. During the last six weeks of 2003, the partners reported Raptiva U.S. sales of $1.4 million.

It is unclear whether the partners will go forward with research in psoriatic arthritis, representatives for both companies said.

With only preliminary data in hand, Tara Cooper, spokeswoman for South San Francisco-based Genentech, told BioWorld Today the trial likely failed because there are factors involved in psoriatic arthritis that are not necessarily involved in psoriasis.

Raptiva is designed to reversibly block the activity of T cells without destroying them. T cells play a key role in the development of psoriasis. Although psoriatic arthritis is associated with and occurs in a subset of patients with psoriasis, the diseases are different and might have different pathophysiologies, the companies said.

Final trial results will be presented at a future, but undetermined, medical conference, Cooper said.

The trial in question demonstrated that Raptiva was safe, well tolerated and didn't cause signs or symptoms of psoriatic arthritis to worsen. After 12 weeks of therapy, 28 percent of patients receiving the candidate achieved an ACR 20 response, compared to 19 percent of patients receiving placebo.

There are no other ongoing Phase II trials of Raptiva in psoriatic arthritis. Studies in other indications are expected, but Zobkiw and Cooper said the partners had not released any specific information on possible future trials.

Under the agreement to develop Raptiva, XOMA will receive 25 percent of U.S. sales and a mid-single-digit royalty on sales outside the U.S. Serono SA, of Geneva, has rights outside the U.S., except in Japan, where Genentech has rights. Serono filed for European regulatory approval in late February for psoriasis, and about two weeks ago the firm said it won approval in Switzerland. (See BioWorld Today, Feb. 7, 2003.)