Catalyst Biosciences has announced that Pfizer has initiated a Phase 1 clinical trial for PF-05280602, an investigational engineered variant of recombinant human Factor VIIa developed by Catalyst Biosciences. PF-05280602 has been engineered to provide improved acute and prophylactic treatment for hemophilia A & B patients with inhibitors. The IND filing and initiation of the Phase 1 clinical trial triggered additional milestone payments of $7 million payable to Catalyst by Pfizer under the terms of their research and license agreement. In June 2009 Catalyst and Wyeth formed an exclusive, worldwide collaboration for the discovery, development and commercialization of improved, second-generation Factor VIIa products. Wyeth was subsequently acquired by Pfizer. Total payments under the collaboration, including an upfront payment of $21 million, ongoing research funding and milestone payments, could exceed $500 million, exclusive of double-digit royalty payments.