Genzyme, a Sanofi company (EURONEXT:SAN and NYSE:SNY), announced today that it has received a Complete Response Letter from the U.S. Food and Drug Administration (FDA) for its supplemental Biologics License Application seeking approval of Lemtrada (alemtuzumab) for the treatment of relapsing forms of multiple sclerosis. A Complete Response Letter informs companies that an application is not ready for approval. FDA has taken the position that Genzyme has not submitted evidence from adequate and well-controlled studies that demonstrate the benefits of Lemtrada outweigh its serious adverse effects. Genzyme understands that the conclusion is related to the design of the completed Phase 3 active comparator studies of Lemtrada in relapsing-remitting MS patients. FDA has also taken the position that one or more additional active comparator clinical trials of different design and execution are needed prior to the approval of Lemtrada. Genzyme strongly disagrees with the FDA’s conclusions and plans to appeal the agency’s decision. “We are extremely disappointed with the outcome of the review and the implications for patients in the U.S. suffering with multiple sclerosis who remain in need of alternative therapies to manage a devastating disease,” said Genzyme President and CEO, David Meeker, M.D. “We strongly believe that the clinical development program, which was designed to demonstrate how Lemtrada compares against an active comparator as opposed to placebo, provides robust evidence of efficacy and a favorable benefit-risk profile. This evidence was also the basis for the approvals of Lemtrada by other regulatory agencies around the world.” Lemtrada is approved in the European Union, Canada, and Australia, and additional marketing applications for Lemtrada are under review by regulatory agencies around the world. Sanofi does not anticipate that the CVR milestone of U.S. approval of Lemtrada by March 31, 2014 will be met. About Lemtrada™ (alemtuzumab) The Lemtrada clinical development program included two pivotal randomized Phase III studies comparing treatment with Lemtrada to Rebif ® (high-dose subcutaneous interferon beta-1a) in patients with RRMS who had active disease and were either new to treatment (CARE-MS I) or who had relapsed while on prior therapy (CARE-MS II), as well as an ongoing extension study. In CARE-MS I, Lemtrada was significantly more effective than Rebif at reducing annualized relapse rates; the difference observed in slowing disability progression did not reach statistical significance. In CARE-MS II, Lemtrada was significantly more effective than interferon beta-1a at reducing annualized relapse rates, and accumulation of disability was significantly slowed in patients given Lemtrada vs. interferon beta-1a. The most common side effects of Lemtrada are infusion associated reactions, infections (upper respiratory tract and urinary tract), lymphopenia and leukopenia. Serious autoimmune conditions can occur in patients receiving Lemtrada. A comprehensive risk management program will support early detection and management of these autoimmune events.