Merck & Co, Inc, Medarex, Inc and Massachusetts Biologic Laboratories (MBL) of the University of Massachusetts Medical School (UMMS) announced that they have signed an exclusive worldwide license agreement for CDA-1 and CDB-1 (also known as MDX-066/MDX-1388 and MBL-CDA1/MBL-CDB1), an investigational fully human monoclonal antibody combination developed to target and neutralize Clostridium difficile toxins A and B, for the treatment of C. difficile infection (CDI). CDA-1 and CDB-1 were co-developed by Medarex and MBL.

Under the terms of the agreement, Merck gains worldwide rights to develop and commercialize CDA-1 and CDB-1. Medarex and MBL will receive an upfront payment of $60 million and are potentially eligible to receive additional cash payments up to $165 million upon achievement of certain milestones associated with the development and approval of a drug candidate covered by this agreement. Upon commercialization, Medarex and MBL will also be eligible to receive double-digit royalties on product sales and milestones if certain sales targets are met. In accordance with the co-development agreement between Medarex and MBL, all payments will be divided equally.

The incidence of C difficile infection (CDI) in the US is rapidly increasing, with rates doubling from 2000 to 2005. The Centers for Disease Control and Prevention has projected that there will be as many as 750,000 cases of CDI per year by 2010¹.

"C difficile infection is the primary cause of infectious diarrhoea in hospitalized elderly patients in developed countries," said Tony Ford-Hutchinson, senior vice president and franchise head, Infectious Diseases and Vaccines, Merck Research Laboratories. "This agreement underscores Merck's ongoing commitment to infectious disease and our strategy of licensing promising candidates with the potential to address serious unmet medical needs."

"Discovering and developing an effective new treatment for a significant public health threat is the mission of MBL," said Donna Ambrosino, executive director of MBL and professor of paediatrics at UMMS. "We are delighted that through this license agreement this candidate will advance towards final clinical studies and thus will potentially be available to patients in the shortest possible time."

"This agreement exemplifies our ability to execute our corporate strategy combining creative science with an industry-leading platform to successfully enter into partnerships that are financially attractive and value-enhancing," said Howard H Pien, chairman and chief executive officer of Medarex. "We will continue to invest in our growing pipeline of innovative product candidates to address significant unmet medical needs, advance them to proof-of-concept and explore strategic options, either through partnership or by advancing the candidate ourselves, that would create long-term value for Medarex shareholders."

Top-line results from a phase-II multicenter, randomized, double-blind, placebo-controlled trial evaluating CDA-1/CDB-1 provided evidence of a statistically significant reduction in the rate of recurrence of CDI compared with placebo. In the study, 200 patients symptomatic with an acute episode of CDI receiving standard of care antibiotics (metronidazole or vancomycin) were randomized to receive intravenous CDA-1/CDB-1 or intravenous placebo. An oral presentation of the phase-II data is scheduled at the upcoming Digestive Disease Week (DDW) in Chicago on June 2, 2009 at 2:15 pm local time.

CDA-1 and CDB-1 are novel, fully human antibodies that were developed by MBL and Medarex to target and neutralize the effects of toxin A and toxin B, respectively, the toxins produced by the bacterium C. difficile and which are associated with a serious and sometimes deadly form of diarrhoea called C. difficile associated diarrhoea.

C. difficile is a spore-forming bacterium that is common in the environment and can colonize the gastrointestinal (GI) tract.

The Massachusetts Biologic Laboratories is the only non-profit FDA- licensed manufacturer of vaccines and other biologic products in the United States. MBL produces 30 percent of the US tetanus/diphtheria vaccine supply.

Medarex is a biopharmaceutical company focused on the discovery, development and potential commercialization of fully human antibody-based therapeutics to treat life-threatening and debilitating diseases, including cancer, inflammation, autoimmune disorders and infectious diseases.