Bristol-Myers Squibb Company and Kosan Biosciences have signed a merger agreement providing for the acquisition of Kosan, a cancer therapeutics company. The transaction is valued at $190 million. The acquisition of Kosan will enhance Bristol-Myers Squibb’s pipeline with compounds in two important classes of anticancer agents: novel Hsp90 (heat shock protein 90) inhibitors and epothilones, the companies said.