Merck Serono Receives Complete Response Letter From FDA on Cladribine Tablets New Drug Application

GENEVA, March 2, 2011 - 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

About Cladribine Tablets

Merck Serono's oral formulation of cladribine (Cladribine
Tablets) is an investigational treatment for patients with relapsing forms of
multiple sclerosis (MS). Cladribine is a small molecule that may interfere
with the behavior and the proliferation of certain white blood cells,
particularly lymphocytes, which are thought to be involved in the
pathological process of MS. Cladribine Tablets were approved in Russia in
July 2010 and in Australia in September 2010 as a treatment of
relapsing-remitting MS and are under regulatory review in other countries.

The clinical development program for Cladribine Tablets
includes:

- The CLARITY (CLAdRIbine Tablets treating MS orallY) study
and its extension: a two-year Phase III placebo-controlled trial designed to
evaluate the efficacy and safety of Cladribine Tablets as a monotherapy in
patients with relapsing-remitting MS and the CLARITY EXTENSION two-year Phase
III study designed to provide data on the long-term safety and efficacy of
extended administration of Cladribine Tablets for up to four years.

- The ORACLE MS (ORAl CLadribine in Early MS) study: a
two-year Phase III placebo-controlled trial designed to evaluate the efficacy
and safety of Cladribine Tablets as a monotherapy in patients at risk of
developing MS (patients who have experienced a first clinical event
suggestive of MS). This trial was announced in September 2008.

- The ONWARD (Oral Cladribine added oN to interferon beta-1a
in patients With Active Relapsing Disease) study: a Phase II
placebo-controlled trial designed primarily to evaluate the safety and
tolerability of adding Cladribine Tablets treatment to patients with
relapsing forms of MS, who have experienced breakthrough disease while on
established interferon-beta therapy. This trial was announced in January
2007.

- The PREMIERE (PRospective observational long-term safEty
registry of Multiple sclerosis patIEnts who have participated in CladRibinE
clinical trials) registry: an eight-year observational safety registry of
patients who have participated in Cladribine Tablets clinical trials,
designed to support the evaluation of the long-term safety of Cladribine
Tablets in MS.

About multiple sclerosis

Multiple sclerosis (MS) is a chronic, inflammatory condition
of the central nervous system and is the most common, non-traumatic,
disabling neurological disease in young adults. It is estimated that
approximately two million people have MS worldwide. While symptoms can vary,
the most common symptoms of MS include blurred vision, numbness or tingling
in the limbs and problems with strength and coordination. The relapsing forms
of MS are the most common.

About Merck Serono

Merck Serono is the biopharmaceutical division of Merck KGaA,
Darmstadt, Germany, a global pharmaceutical and chemical company.
Headquartered in Geneva, Switzerland, Merck Serono discovers, develops,
manufactures and markets prescription medicines of both chemical and
biological origin in specialist indications. In the United States and Canada,
EMD Serono operates as a separately incorporated affiliate of Merck Serono.

Merck Serono has leading brands serving patients with cancer
(Erbitux(R), cetuximab), multiple sclerosis (Rebif(R), interferon beta-1a),
infertility (Gonal-f(R), follitropin alfa), endocrine and metabolic disorders
(Saizen(R) and Serostim(R), somatropin), (Kuvan(R), sapropterin
dihydrochloride), (Egrifta(TM), tesamorelin), as well as cardiometabolic
diseases (Glucophage(R), metformin), (Concor(R), bisoprolol), (Euthyrox(R),
levothyroxine). Not all products are available in all markets.

With an annual R&D expenditure of over EUR 1bn, Merck Serono
is committed to growing its business in specialist-focused therapeutic areas
including neurodegenerative diseases, oncology, fertility and endocrinology,
as well as new areas potentially arising out of research and development in
rheumatology.

About Merck

Merck is a global pharmaceutical and chemical company with
total revenues of EUR 9.3 billion in 2010, a history that began in 1668, and
a future shaped by more than 40,000 employees in 67 countries. Its success is
characterized by innovations from entrepreneurial employees. Merck's
operating activities come under the umbrella of Merck KGaA, in which the
Merck family holds an approximately 70% interest and free shareholders own
the remaining approximately 30%. In 1917 the U.S. subsidiary Merck & Co. was
expropriated and has been an independent company ever since.

For more information, please visit www.merckserono.com
or www.merck.de

Merck Serono S.A. - Geneva, 9 Chemin des Mines, 1202 Genève, Suisse; Media relations: Tel: +41-22-414-36-00