By Charles Craig

Sumitomo Pharmaceuticals Co. Ltd. licensed a monoclonal antibody to prevent blood clots from Cytel Corp., bringing to three the number of drug candidates in their collaboration, which has paid Cytel more than $22 million over five years.

Officials of San Diego-based Cytel said Sumitomo, of Osaka, Japan, exercised an option for development rights in Japan to CY-1748, a P-selectin antibody whose potential uses include the treatment of deep vein thrombosis.

P-selectin is an adhesion molecule on platelets. When it interacts with neutrophils, which are white blood cells, it can trigger blood clots. CY-1748 is a humanized monoclonal antibody designed to block P-selectin from contact with neutrophils. The drug is in preclinical development.

Sumitomo also has development rights in Japan to Cytel's Cylexin, the company's most advanced product, and a second generation form of the carbohydrate selectin blocking drug.

Cytel has been working with Sumitomo since 1991 on development of drugs based on cell adhesion molecules. Cytel has received a $5 million equity investment and $17.5 million in research support from the Japanese pharmaceutical firm.

Karin Eastham, Cytel's chief financial officer, said her company did not receive any additional funding when Sumitomo exercised its option to develop CY-1748 along with the Cylexin products.

In January Pharmacia & Upjohn Inc., of Kalamazoo, Mich., ended its collaboration with Cytel for development of CY-1748 after paying $4 million for North American and European rights.

Eastham said Cytel is evaluating the possibility of proceeding with clinical development of the P-selectin antibody itself or of seeking other collaborators.

Cylexin, a small molecule cell adhesion blocker, was developed to prevent migration of neutrophils, which cause inflammatory damage to tissues.

The drug failed last year in a Phase II trial for prevention of cardiac reperfusion injury in heart attack patients treated with angioplasty. It now is being evaluated in a Phase II study involving infants undergoing surgery for congenital heart defects.

Cytel was collaborating with Schwarz Pharma AG, of Monheim, Germany, on development of Cylexin for heart attack patients. Eastham said the two companies are evaluating their partnership. No decision has been made on Schwarz's participation in the clinical development program for infants with heart problems.

Cytel's stock (NASDAQ:CYTL) closed Tuesday at $3.25, up $0.188. *