San Diego-based Optimer Pharmaceuticals and Tokyo-based Astellas Pharma have formed an exclusive collaboration and license agreement to develop and commercialize fidaxomicin tablets in Japan for the treatment of Clostridium difficile infection (CDI) affecting the colon.

In return for the exclusive license to fidaxomicin in Japan, Optimer is entitled to receive a one-time, up-front cash payment of $20 million from Astellas. Optimer is also eligible to receive up to an additional $70 million in milestone payments. Furthermore, Optimer is entitled to receive payments from Astellas that provide a return resulting in a double digit percent of Astellas net sales in the territory. Astellas is responsible for all future costs associated with the development and commercialization of fidaxomicin in Japan.

Yoshihiko Hatanaka, president and CEO of Astellas Pharma, said, "We believe that fidaxomicin's highly differentiated clinical profile, which has been confirmed by clinical studies conducted in the U.S. and E.U., has the potential to provide a new and unique treatment option for patients in Japan.”

"Astellas is a leader in the anti-infective market in Japan,” explained Optimer’s president and CEO, Pedro Lichtinger. “Leveraging their expertise efficiently helps realize the potential of fidaxomicin to meet the serious unmet needs of CDI patients in Japan, helping to address the risk of recurrence inherent in the disease, while optimizing the market opportunity for our shareholders.”

In 2011, Optimer entered into a commercial partnership with Astellas Pharma Europe to develop and market fidaxomicin under the trade name Dificlir in Europe and other countries in the Middle East, Africa and the Commonwealth of Independent States. The EMA granted marketing authorization to Dificlir in December 2011 and Astellas Pharma Europe expects to begin selling Dificlir in the first of its territories starting in 2012.