Press Release December 12, 2006

GlaxoSmithKline and EPIX Pharmaceuticals Enter Drug Discovery and Development Alliance

BOSTON, Dec. 12, 2006 — GlaxoSmithKline and EPIX Pharmaceuticals have announced a worldwide multi-target collaboration to discover, develop and market novel medicines targeting four G-protein coupled receptors for the treatment of a variety of diseases, including EPIX's novel 5-HT4 partial agonist program, PRX-03140, in early-stage clinical development for the treatment of Alzheimer's disease. EPIX will receive total initial payments of $35 million, including $17.5 million through the purchase of 3,009,027 shares of common stock. In addition, EPIX will be eligible to earn potential milestones of up to $1.2 billion based on the achievement of certain discovery, development, regulatory and commercial milestones and tiered, double-digit royalties on sales of products developed in the collaboration.

Goodwin Procter partner Christopher Denn represented EPIX in this transaction.