GENEVA, March 2, 2011 /PRNewswire/ -- Merck Serono, a division of Merck KGaA, Darmstadt, Germany, announced today that it received a complete response letter (CRL) from the U.S. Food and Drug Administration (FDA) on the new drug application (NDA) for Cladribine Tablets, Merck Serono's proprietary investigational oral formulation of cladribine, as a therapy for relapsing-remitting multiple sclerosis (MS).

A complete response letter is issued by the FDA when the Agency's review of a file is complete and the application cannot be approved in its present form. In the complete response letter, the FDA concluded that substantial evidence of Cladribine Tablets' effectiveness was provided by the CLARITY1 study. However, the FDA has requested the Company provide an improved understanding of safety risks and the overall benefit-risk profile either through additional analyses or by additional studies. Merck Serono intends to request an end-of-review meeting with the FDA to clarify next steps and to identify whether data from completed and ongoing clinical studies can address the Agency's questions.

"Our commitment to transform the way people living with MS approach their therapy options remains steadfast," said Fereydoun Firouz, President and CEO of EMD Serono, Inc. "We look forward to working with the FDA to address the safety issues in its letter and will continue to move toward identifying a path that provides patients and physicians the opportunity to have access to Cladribine Tablets in the treatment of MS."

Merck Serono remains committed to completing the ongoing clinical trials with Cladribine Tablets. These trials, which are fully enrolled, will provide additional information on the efficacy and safety of Cladribine Tablets in MS. Top-line results from the CLARITY EXTENSION and ORACLE MS2 studies are expected by the end of 2011. Top-line results from the ONWARD3 study are expected in the first half of 2012.

Cladribine Tablets are approved and available under the trade name Movectro(R) in Australia and Russia as a treatment of relapsing-remitting MS and are under regulatory review in other countries.

1 CLARITY: CLAdRIbine Tablets treating MS orallY

2 ORACLE MS: ORAl CLadribine in Early MS

3 ONWARD: Oral Cladribine added oN to interferon beta-1a in patients With Active Relapsing Disease