By Kim Coghill

Washington Editor

MedImmune Inc. started dosing psoriasis patients with siplizumab (MEDI-507) in a 400-patient Phase II clinical trial.

By the end of the year, the company expects to have enrolled about 750 patients in seven different Phase II clinical studies of siplizumab, a humanized monoclonal antibody licensed from BioTransplant Inc., of Charlestown, Mass., in 1995. Phase III testing likely will begin in early 2002, Lori Weiman, senior director of corporate communications for Gaithersburg, Md.-based MedImmune, told BioWorld Today.

The 400-patient Phase II study is a randomized, double-blind, placebo-controlled trial in which patients with plaque psoriasis on at least 10 percent of their body surface area and a minimum PASI (Psoriasis Area and Severity Index) score of 8 will receive subcutaneous injections of siplizumab. The study will compare the efficacy of different dosing regimens of MEDI-507, as measured by PASI score, as well as assess the drug¿s safety. The trial is being conducted at 50 sites in the U.S. and Canada.

Weiman said siplizumab is being tested to see whether it can reduce the incidence of moderate to severe psoriasis. Siplizumab likely will be tested for other indications at some point, Weiman said.

Psoriasis is a chronic skin disease that usually appears as patches of raised red skin covered by a flaky white buildup. The condition affects up to 6 million Americans annually and its outpatient costs total about $1 billion a year, a statement from the company said.

Siplizumab binds to the CD2 receptor found on the surface of T cells and natural killer (NK) cells. By binding to CD2, siplizumab selectively suppresses the function of T cells and NK cells. T cells are an essential part of the pathophysiology of psoriasis, and it is believed that modulation of T-cell activities may be therapeutically advantageous in the treatment of psoriasis.

Siplizumab is a form of BioTransplant¿s murine monoclonal antibody, BTI-322. In the licensing agreement with MedImmune, BioTransplant retained the right to use BTI-322 in its proprietary systems: ImmunoCognance, AlloMune and ZenoMune.

MedImmune paid BioTransplant $2 million up front for worldwide rights to siplizumab. Estimates in 1995 indicated that the deal eventually could be worth up to $14 million. (See BioWorld Today, Oct. 13, 1995.)

Weiman would not discuss specifics of the 1995 agreement except to say that when siplizumab reaches market, BioTransplant will receive royalties.

MedImmune also said it completed two important steps in other Phase II studies. In an intravenously dosed study initiated in March and conducted at about 25 sites in North America, the company said that dosing in all 124 patients was complete. Enrollment of 121 patients has been completed in a subcutaneously dosed study initiated in June at about 20 sites in Europe.

MedImmune will present safety and efficacy data later this week from three additional Phase I and Phase I/II studies, in Stockholm, Sweden, at the European Society of Dermatological Research Meeting.

MedImmune¿s other products are Synagis (palivizumab), a monoclonal antibody used to combat infectious disease and indicated for the prevention of serious lower respiratory tract disease caused by respiratory syncytial virus in pediatric patients; Ethyol (amifostine), a selective cytoprotective agent used to reduce some toxicities associated with cancer chemotherapy and radiotherapy; CytoGam, an intravenous immune globulin indicated for prophylaxis against cytomegalovirus disease associated with transplantation of kidney, lung, liver, pancreas and heart; NeuTrexin, an intravenous treatment for pneumonia in immunocompromised patients; and RespiGam, a polyclonal antibody used to prevent lower respiratory tract infection caused by RSV.

The company also is conducting Phase II studies of a urinary tract infection vaccine and a vaccine against cervical cancer.

MedImmune¿s stock (NASDAQ:MEDI) closed Monday at $35.21, down $2.63, while BioTransplant¿s stock (NASDAQ:BTRN) closed at $4.49, down 21 cents.