Two-Year Results From CLARITY Study With Cladribine Tablets in Multiple Sclerosis Published in The New England Journal of Medicine

GENEVA, Switzerland, January 21 - Merck Serono, a division of Merck KGaA, Darmstadt, Germany,
announced today the online publication of the results from the CLARITY(1)
Phase III trial using Cladribine Tablets (Merck Serono's proprietary
investigational oral formulation of cladribine) in The New England Journal of
Medicine(2). The CLARITY study was a two-year (96-week), randomized,
double-blind, placebo-controlled Phase III trial of Cladribine Tablets in
1,326 people with relapsing-remitting multiple sclerosis (MS).

"The CLARITY trial represents an important step forward in
multiple sclerosis research, and we are pleased that the results have been
published in The New England Journal of Medicine," says Dr. Gavin Giovannoni,
principal investigator of the CLARITY study and lead author on the
publication, from Queen Mary University London, Blizard Institute of Cell and
Molecular Science, Barts and the London School of Medicine and Dentistry,
London, United Kingdom.

The authors report in the publication that the primary end
point and key secondary end points of the CLARITY trial were met. The CLARITY
data were presented at the 61st Annual Meeting of the American Academy of
Neurology (AAN) in April 2009 and at other international scientific meetings.

CLARITY study design

The CLARITY study was a two-year (96-week), randomized,
double-blind, placebo-controlled, international trial. It randomized 1,326
patients with relapsing-remitting MS according to the revised McDonald
criteria. Study participants were randomized to one of three different
treatment groups consisting of two different dose regimens of Cladribine
Tablets or matching placebo tablets (1:1:1 ratio). Cladribine Tablets were
given in two (3.5 mg/kg total dose) or four (5.25 mg/kg total dose) treatment
courses in the first year, with each course consisting of once daily
administration for four to five consecutive days (depending on patient
weight), which means study patients took Cladribine Tablets for 8 to 20 days
during the year. In the second year, two treatment courses were administered
to all patient groups, meaning that patients took Cladribine Tablets for 8 to
10 days during the year.

The primary endpoint of the CLARITY study was the relapse rate
over 96 weeks. Secondary endpoints included MRI endpoints, proportion of
subjects relapse-free and disability progression at 96 weeks.

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.

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 its two-year
      extension 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.

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 more
than 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 division for innovative prescription
pharmaceuticals of Merck KGaA, Darmstadt, Germany, a global pharmaceutical
and chemical company. Headquartered in Geneva, Switzerland, Merck Serono
discovers, develops, manufactures and markets innovative small molecules and
biopharmaceuticals to help patients with unmet medical needs. In the United
States and Canada, EMD Serono operates through separately incorporated
affiliates.

Merck Serono has leading brands serving patients with cancer (Erbitux(R),
cetuximab), multiple sclerosis (Rebif(R), interferon beta-1a), infertility
(Gonal-f(R), follitropin alpha), endocrine and metabolic disorders (Saizen(R)
and Serostim(R), somatropin), (Kuvan(R), sapropterin dihydrochloride) 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 around 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
autoimmune and inflammatory diseases.

About Merck

Merck is a global pharmaceutical and chemical company with
total revenues of EUR 7.6 billion in 2008, a history that began in 1668, and
a future shaped by approximately 33,000 employees in 60 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.

(1) CLARITY: CLAdRIbine Tablets Treating MS OrallY

(2) Giovannoni G et al. A placebo-Controlled Trial of Oral Cladribine for
Relapsing Multiple Sclerosis; available on www.nejm.org; will also be
published in the February 4, 2010 printed issue of The New England Journal of
Medicine

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

Merck Serono, 9 Chemin des Mines, 1202 Geneva, Switzerland. Media Relations: Tel.: +41-22-414-36-00