¿ Immunex Corp., of Seattle, issued a seven-year, 3 percent coupon, convertible subordinated note to American Home Products Corp., of Madison, N.J., which already owns 54.1 percent of Immunex. The principal amount of the note is $450 million. The note is convertible into common stock at $173.68 per share, a 30 percent premium to recent prices. Immunex can call the note after three years if the stock¿s price is at least $208.42, and at any time after four years if the price exceeds the conversion price.

¿ Signal Pharmaceuticals Inc., of San Diego, and Ares-Serono, of Geneva, Switzerland, expanded their 1997 collaboration to identify small-molecule inhibitors of the NF-kB pathways. The expansion gives Ares-Serono exclusive rights to certain Asian countries, including Japan, which weren¿t covered in the original deal. Signal will receive a $2 million license fee and potential milestones and royalties.

¿ Trimedyne Inc., of Irvine, Calif., said its 90 percent-owned subsidiary, Cardiodyne Inc., entered into a collaboration with Endovasc Ltd. Inc., of Montgomery, Texas, to develop liposome-encapsulated agents to promote angiogenesis. The agents will be injected into channels in the heart wall created by Cardiodyne¿s Laser Transmyocardial Revascularization System, which is designed to treat severe angina. Terms were not disclosed.