Amgen Inc.'s proposed acquisition of Onyx Pharmaceuticals Inc. will more than double the bellwether's portfolio of marketed targeted cancer therapeutics, putting it in a tie with GlaxoSmithKline plc for second place behind Roche and its Genentech Inc. unit. The question is what Amgen's next act will be.

After two months of negotiations, Amgen agreed in August to purchase Onyx for $10.4 billion (see BioCentury, Sept. 2).