First sales of DIFICLIR™ by Astellas Pharma Europe triggers 10 Million Euro Milestone Payment to Optimer Pharmaceuticals

Optimer Pharmaceuticals, Inc.

announced that Astellas Pharma Europe achieved the first sales of DIFICLIR (fidaxomicin) tablets, triggering a 10 million Euro milestone payment from Astellas to Optimer. Under the 2011 collaboration and license agreement, Optimer granted to Astellas development and commercialization rights in Europe and certain other countries in the Middle East, Africa and the Commonwealth of Independent States (CIS). The European Commission granted Marketing Authorization for DIFICLIR tablets for the treatment of adults with Clostridium difficile infections (CDI) in December, 2011. "We are truly excited about the potential of DIFICLIR™ to achieve better clinical outcomes for patients with CDI, as Astellas sequentially launches this important new medicine across Europe," said Pedro Lichtinger, President and Chief Executive Officer of Optimer. "We believe DIFICLIR will achieve rapid adoption in markets across Europe because of the high unmet medical need. Additionally, the Astellas strategic focus on anti-infectives combined with their significant commercial and medical programs in this therapy area will be truly impactful."