By Lisa Seachrist

Washington Editor

WASHINGTON — Immunex Corp. and majority shareholder American Home Products Corp. terminated their cancer research collaboration and restructured the agreement to share rights on certain products.

Under terms of the agreement, which becomes effective immediately, Seattle-based Immunex will no longer be obligated to fund certain cancer product research and development at American Home Products' wholly owned subsidiary, American Cyanamid. Those payments have amounted to approximately $17 million per year.

In addition, Immunex will receive the worldwide rights to market the cancer drug Leukine, as well as three drugs still in clinical development: Mobist (FLT-3 ligand), Interleukin-15 (Il-15) and CD-40 ligand. Previously American Home Products, of Madison, N.J., held rights to those products outside North America.

"From our perspective, this is an opportunity for profit as well as a significant cash savings," said Tim Warner, spokesman for Immunex. "The deal also allows us to operate independently on our oncology development program."

The deal doesn't affect the marketing agreement for Enbrel — a rheumatoid arthritis drug comprised of tumor necrosis factor receptor. Immunex signed a potential $100 million Enbrel marketing pact with American Home Products last September. (See BioWorld Today, Sept. 29, 1997, p.1.)

In May, Enbrel was granted expedited review status by the FDA, meaning the agency will make a decision on the drug by the end of this year or early next.

American Home Products will have the option to acquire worldwide rights to four future Immunex products which are currently in preclinical development. Upon obtaining rights to a drug, American Home Products will pay an initial fee, milestones and royalties to Immunex.

American Home Products can exercise its option to obtain a product anytime up to 90 days following data from a Phase II trial. The cost of the product increases the further developed it becomes.

In addition, Immunex has the right to veto two of American Home Products' requests in exchange for paying milestones and royalties. American Home Products then could select a replacement product in exchange for waiving milestone and royalty payments.

"This deal really allows us to pump up our pipeline significantly," Warner said. Savings from the deal will be used for internal R&D efforts and for bolstering the company's bottom line.

Immunex's stock (NASDAQ:IMNX) closed Thursday at $64 per share, down $2.25 on the news. American Home Products owns 54 percent of Immunex. *