Portola Pharmaceuticals to Regain Global Rights for Investigational Medicine Betrixaban from Merck

SOUTH SAN FRANCISCO, Calif. and WHITEHOUSE STATION, N.J. - Portola Pharmaceuticals and Merck (NYSE: MRK), known as MSD outside the United States and Canada, today announced that Merck plans to return to Portola all rights for betrixaban, an investigational oral Factor Xa inhibitor anticoagulant being evaluated for the prevention of stroke in patients with atrial fibrillation (SPAF). This decision was made following a review of Merck’s investigational portfolio.

"Regaining full rights to betrixaban represents a transformational opportunity for Portola" said William Lis, chief executive officer of Portola. "We will work with our academic partners on options for an independent development plan to bring betrixaban to the market and intend to discuss these options with the FDA in the near future"

In July 2009, Merck and Portola announced an exclusive global collaboration and license agreement for the development and commercialization of betrixaban. Betrixaban most recently completed Phase II testing in the EXPLORE-Xa trial in which it showed dose dependent clinical activity with similar or lower rates of bleeding compared to warfarin in the study population. These results were presented during a late-breaking clinical trials session at the American College of Cardiology’s 59th Annual Scientific Session in March 2010.

"Working closely with our Portola collaborators we have advanced betrixaban to this Phase III-ready stage" said Luciano Rossetti, M.D., senior vice president, Global Scientific Strategy at Merck. "As part of an ongoing prioritization of our late-stage pipeline, we have decided to return rights for betrixaban to Portola. Merck continues to advance its broad late-stage pipeline and remains committed to delivering medicines for cardiovascular disease"

About Portola Pharmaceuticals, Inc.
Portola Pharmaceuticals discovers and develops innovative therapeutics based on targets with established proof of concept that are designed to provide significant advances over current treatments for cardiovascular and autoimmune/inflammatory diseases. Portola scientists have successfully collaborated for over 15 years on the discovery and development of novel small molecule agents targeting platelets, coagulation pathways and protein kinases.

In thrombosis, Portola is developing elinogrel, a Phase III-ready, direct-acting, competitive and reversible i.v. and oral P2Y12 ADP receptor antagonist licensed to Novartis Pharma AG; betrixaban, a Phase III-ready, long-acting, oral direct Factor Xa inhibitor; and PRT064445 Factor Xa inhibitor antidote. In inflammation, Portola’s broad chemistry capability has led to the discovery of potent, oral specific inhibitors of Spleen Tyrosine Kinase (Syk) and Janus Kinase (JAK), as well as dual inhibitors of Syk and JAK. Portola is developing multiple molecules across multiple targets, including PRT062607, the most advanced oral Syk-specific inhibitor in development; PRT062070, a dual Syk-JAK inhibitor; and novel JAK3-specific and JAK3/1 inhibitors for chronic autoimmune indications. For additional information, visit www.portola.com.

About Merck
Today’s Merck is a global healthcare leader working to help the world be well. Merck is known as MSD outside the United States and Canada. Through our prescription medicines, vaccines, biologic therapies, and consumer care and animal health products, we work with customers and operate in more than 140 countries to deliver innovative health solutions. We also demonstrate our commitment to increasing access to healthcare through far-reaching policies, programs and partnerships that donate and deliver our products to the people who need them. For more information, visit www.merck.com.

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