Cephalon, Inc. Announces Agreement to Acquire Mepha AG

Expands Range of Products and Reach in Europe, Africa, and the Middle East

FRAZER, Philadelphia, AESCH, Switzerland and MAISONS ALFORT, France, February 1 - Cephalon, Inc. (Nasdaq: CEPH) announced today that it has
signed an agreement to acquire Mepha AG and its subsidiaries, a profitable,
privately-held, Swiss-based pharmaceutical company. Mepha has specific
expertise in innovative dosage formulations and markets both generic and
branded generic products. The acquisition diversifies the company's business
mix, doubles the size of its international business, and provides an
attractive platform to launch current and future products in new, developed
and emerging markets.

Mepha manufactures and markets over 120 products in 50
countries and recognized sales of approximately CHF 400 million in 2009. With
its exposure to high-growth international markets, and a track record of
innovation, Mepha has achieved compound annual growth rates (CAGR) in sales
of more than 13 percent over the last five years. In addition to its existing
products, Mepha has a broad pipeline of approximately 50 chemical entities
planned for launch over the next five years.

Under the terms of the agreement, Cephalon will purchase
Mepha AG for CHF 622.5 million, or an estimated $590 million USD, from the
Merckle family-owned Mepha Holding AG, subject to adjustments upon closing.
The transaction is expected to close in the next 10-12 weeks upon completion
of certain closing conditions, including receipt of applicable antitrust
approvals. Cephalon expects that the acquisition will be accretive to
adjusted earnings per share in 2010 and will update its 2010 guidance when it
reports full year 2009 financial results on February 11, 2010. In the
interim, the company withdraws its full year 2010 guidance issued on October
27, 2009.

"The addition of Mepha will transform our international
business overnight, expanding our ability to serve global markets and reach
patients in new territories for the first time," said Frank Baldino, Jr.,
Ph.D., Chairman and CEO of Cephalon. "With this deal, we now serve all three
types of pharmaceutical markets, proprietary branded, generic and branded
generic. We believe this balance will increase the growth and stability of
our business," added Baldino.

Alain Aragues, Executive Vice President and President of
Cephalon Europe, said, "The acquisition of Mepha will help us to
significantly grow our current business and positions us as a more attractive
partner for further business development opportunities in the European,
Middle East and African regions."

Dr. Thomas Villiger, CEO of Mepha Group, added, "Mepha and
Cephalon complement each other as far as markets and products are concerned.
Mepha's leading position on the Swiss market will be immediately enhanced by
the addition of innovative therapies from Cephalon."

Deutsche Bank Securities Inc. served as exclusive financial
advisor to Cephalon.

Cephalon will host a conference call for investors and
analysts on February 1, 2010, at 9:00 a.m. Eastern Time to discuss the
transaction. A slide presentation will be available on the company website at
investors.cephalon.com/phoenix.zhtml?c=81709&p=irol-irhome

                         February 1, 2010, Schedule
    8:10 a.m. EST  Company presentation will be made available.
    8:50 a.m. EST  Conference line opens. To participate in the conference
                   call, dial 913-312-0408 and refer to Conference Code
                   Number 1894492.
    9:00 a.m. EST  Conference call begins promptly.

                            Simultaneous Webcast

Investors can listen to the call live by logging on to the
company's website at www.cephalon.com and clicking on "Investor
Information," then "Webcast." Please click on the link and follow the prompts
for registration and access.

If you are unable to listen to the live broadcast, an audio or
webcast replay of the call will be available approximately two hours after
the event until Midnight EST, February 8, 2010. To listen to the audio
replay, dial +1-719-457-0820 and use the Conference Code Number 1894492.

Additional information presented on the conference call may be
made available on the Investor Information page of the company's website.

About Mepha AG

Founded in 1949, Mepha is a Swiss-based pharmaceutical
company marketing branded and non-branded generics as well as specialty
products in more than 50 countries. Mepha develops and manufactures its
products in Aesch/Basel - Switzerland with a strong focus on Swiss-quality
standards. Mepha's R & D focuses on the development of improved and
innovative generics providing additional benefits for patients. Furthermore,
Mepha is active in malaria research offering innovative life-saving therapies
for adults and children.

Mepha is the leading company on the Swiss generic market,
with more than 120 products in over 500 packaging forms and also providing
unique services to healthcare professionals and patients. Mepha has
operational subsidiaries in Portugal and the Baltics. Through partnerships,
Mepha markets its products in other European countries, in the Middle East,
Africa, South and Central America as well as in Asia. Mepha employs
approximately 1,000 people worldwide, 500 of them in Switzerland. For more
information on Mepha, visit their website at www.mepha.com.

About Cephalon, Inc.

Cephalon is an international biopharmaceutical company
dedicated to discovering, developing and bringing to market medications for
difficult to treat and rare conditions. Since its inception in 1987, Cephalon
has brought first-in-class and best-in-class medicines to patients around the
world in several therapeutic areas. Cephalon has the distinction of being one
of the world's fastest-growing biopharmaceutical companies, now among the
Fortune 1000 and a member of the S&P 500 Index, employing approximately 3,000
people worldwide.

Cephalon has a growing presence in Europe, the Middle East and
Africa. The Cephalon European headquarters and pre-clinical development
center are located in Maisons-Alfort, France, just outside of Paris.
Operational subsidiaries are located in the United Kingdom, France, Germany,
Italy, Spain, the Netherlands (which covers the entire Benelux region), and
Poland (which covers Eastern Europe and Scandinavia). Cephalon Europe markets
more than 30 products in 50 countries in four therapeutic areas: central
nervous system, pain, primary care and oncology.

The company's proprietary products in the United States
include: NUVIGIL(R) (armodafinil) Tablets [C-IV], TREANDA(R) (bendamustine
hydrochloride) for Injection, AMRIX(R) (cyclobenzaprine hydrochloride
extended-release capsules), FENTORA(R) (fentanyl buccal tablet) [C-II],
TRISENOX(R) (arsenic trioxide) injection, GABITRIL(R) (tiagabine
hydrochloride), PROVIGIL(R) (modafinil) Tablets [C-IV] and ACTIQ(R) (oral
transmucosal fentanyl citrate) [C-II]. The company also markets numerous
products internationally. Full prescribing information on its U.S. products
is available at www.cephalon.com or by calling +1-800-896-5855.

In addition to historical facts or statements of current condition, this
press release may contain forward-looking statements. Forward-looking
statements provide Cephalon's current expectations or forecasts of future
events. These may include statements regarding the accretive nature of the
acquisition of the Mepha Group with respect to Cephalon's adjusted earnings
per share in 2010, anticipated scientific progress on its research programs,
development of potential pharmaceutical products, interpretation of clinical
results, prospects for regulatory approval, manufacturing development and
capabilities, market prospects for its products, sales and earnings guidance,
and other statements regarding matters that are not historical facts. You may
identify some of these forward-looking statements by the use of words in the
statements such as "anticipate," "estimate," "expect," "project," "intend,"
"plan," "believe" or other words and terms of similar meaning. Cephalon's
performance and financial results could differ materially from those
reflected in these forward-looking statements due to general financial,
economic, regulatory and political conditions affecting the biotechnology and
pharmaceutical industries as well as more specific risks and uncertainties
facing Cephalon such as those set forth in its reports on Form 8-K, 10-Q and
10-K filed with the U.S. Securities and Exchange Commission. Given these
risks and uncertainties, any or all of these forward-looking statements may
prove to be incorrect. Therefore, you should not rely on any such factors or
forward-looking statements. Furthermore, Cephalon does not intend to update
publicly any forward-looking statement, except as required by law. The
Private Securities Litigation Reform Act of 1995 permits this discussion.

    Contacts:

    US Media
    Sheryl Williams
    +1-610-738-6493
    swilliams@cephalon.com 

    European Media
    Marie-Dominique de La Salle
    +33(1)49-81-82-48
    mddelasalle@cephalon.fr 

    Investors
    Robert (Chip) Merritt
    +1-610-738-6376
    cmerritt@cephalon.com 

    Linda Pavy
    Burson Marsteller
    +33(6)07-59-43-95
    Linda@Pavy@bm.com

US Media: Sheryl Williams, +1-610-738-6493, swilliams at cephalon.com; European Media: Marie-Dominique de La Salle, +33(1)49-81-82-48, mddelasalle at cephalon.fr; Investors:
Robert (Chip) Merritt, +1-610-738-6376, cmerritt at cephalon.com; Linda Pavy: Burson Marsteller, +33(6)07-59-43-95, Linda at Pavy at bm.com