Achillion Names Milind Deshpande, Ph.D., as President, Chief Executive Officer, Following Announced Retirement of Michael

Achillion Names Milind Deshpande, Ph.D., as President, Chief Executive
Officer, Following Announced Retirement of Michael Kishbauch

NEW HAVEN, Conn., May 28, 2013 (GLOBE NEWSWIRE) -- Achillion Pharmaceuticals,
Inc. (Nasdaq:ACHN) today announced that President and Chief Executive Officer
Michael D. Kishbauch has decided to retire. In conjunction with this decision,
the Board has appointed President of Research and Development and Chief
Scientific Officer, Milind Deshpande, Ph.D., to the role of President and
Chief Executive Officer and to the Board of Directors. Mr. Kishbauch, who will
continue working with management over a three month transition period, will
remain a Director on the Achillion Board and is being appointed Chair of a
newly-formed Strategy and Corporate Development Committee of the Board.

Mr. Kishbauch commented, "Following nearly nine eventful and productive years
at Achillion, where I have been privileged to see the advancement of seven
novel compounds to clinical development, the Company's initial public offering
and the evolution to a scientifically and financially stable organization, I
have decided that the moment is right to transition leadership, and I am very
pleased that the Board has enthusiastically supported Dr. Deshpande to succeed
me as Chief Executive Officer. I remain fully confident in the portfolio of
HCV assets we have advanced, including sovaprevir and ACH-3102, and believe
they have the potential to produce clinical results that will enable Achillion
to compete effectivelyin the substantial HCV market."

David Scheer, Chairman of Achillion, commented, "During his tenure at
Achillion, Mike has done a remarkable job advancing Achillion's discoveries
through development and toward commercialization. The strength and
cohesiveness of the management team that he has cultivated ensures a seamless
transition, and we are very fortunate and honored to have Dr. Deshpande take
over the reins at this most important time for the Company."

"I wish to thank Mike for his leadership and mentorship over the past nine
years," commented Dr. Deshpande. "I am humbled by the Board's decision and
excited for the opportunity to bring Achillion into late stage clinical
development, working closely with the very talented senior management team and
workforce that we have assembled who have a history of bringing promising
compounds through clinical development and to the market."

Achillion also announced today that David Wright has decided to step down from
the Board of Directors following the Annual Stockholder's Meeting held on May
28, 2013.

Mr. Scheer further commented, "On behalf of the entire Board of Directors, I
would like to sincerely thank David for his nearly six years of service,
during which time he provided invaluable guidance to Achillion."

Michael Kishbauch was appointed to his current role in July 2004.

Milind Desphande, Ph.D., joined Achillion in September 2001 as Vice President
of Chemistry and was named Head of Drug Discovery in April 2002. Dr. Deshpande
was promoted to Senior Vice President of Drug Discovery in December 2002,
Senior Vice President and Chief Scientific Officer in December 2004, and as
Executive Vice President of Research and Development and Chief Scientific
Officer since June 2007. He was named President of Research and Development in
2011.

About Achillion Pharmaceuticals

Achillion is an innovative pharmaceutical company dedicated to bringing
important new treatments to patients with infectious disease. Achillion's
discovery, clinical development, and commercial teams have advanced multiple
novel product candidates with proven mechanisms of action into studies and
toward the market. Achillion is focused on solutions for the most challenging
problems in infectious disease including HCV and resistant bacterial
infections. For more information on Achillion Pharmaceuticals, please visit
www.achillion.com or call 1-203-624-7000.

Forward-Looking Statements

This press release includes forward-looking statements within the meaning of
the Private Securities Litigation Reform Act of 1995 that are subject to
risks, uncertainties and other important factors that could cause actual
results to differ materially from those indicated by such forward-looking
statements, including statements with respect to: the potential for
Achillion's platform of HCV assets to produce clinical results and advance
into later stages; Achillion's ability to compete in the HCV market; and
expectations regarding the CEO transition. Among the factors that could cause
actual results to differ materially from those indicated by such
forward-looking statements are risks relating to, among other things
Achillion's ability to: replicate in later clinical trials positive results
found in earlier stage clinical trials of sovaprevir, ACH-3102 and its other
product candidates; advance the development of its drug candidates under the
timelines it anticipates in current and future clinical trials; obtain
necessary regulatory approvals; obtain patent protection for its drug
candidates and the freedom to operate under third party intellectual property;
establish commercial manufacturing arrangements; identify, enter into and
maintain collaboration agreements with appropriate third-parties; compete
successfully with other companies that are seeking to develop improved
therapies for the treatment of HCV; manage expenses; retain key employees,
including Dr. Deshpande; successfully execute on its business plans and
strategies; and raise the substantial additional capital needed to achieve its
business objectives. These and other risks are described in the reports filed
by Achillion with the U.S. Securities and Exchange Commission, including its
Annual Report on Form 10-K for the fiscal year ended December 31, 2012 and its
subsequent SEC filings.

In addition, any forward-looking statement in this press release represents
Achillion's views only as of the date of this press release and should not be
relied upon as representing its views as of any subsequent date. Achillion
disclaims any obligation to update any forward-looking statement, except as
required by applicable law.

CONTACT: Company Contact:
         Glenn Schulman
         Achillion Pharmaceuticals, Inc.
         Tel. (203) 624-7000
         gschulman@achillion.com
        
         Media:
         Sally Barton
         Ogilvy PR
         Tel. (212) 880-5240
         sally.barton@ogilvy.com
        
         Investors:
         Mary Kay Fenton
         Achillion Pharmaceuticals, Inc.
         Tel. (203) 624-7000
         mfenton@achillion.com
        
         Investors:
         Seth Lewis
         The Trout Group, LLC
         Tel. (646) 378-2952
         slewis@troutgroup.com
 
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