INVESTORS

Feb 16, 2012

Virology Profile Following Treatment With ACH-1625 Discussed in Oral Presentation at 2012 Asian Pacific Liver Conference

NEW HAVEN, Conn., Feb. 16, 2012 (GLOBE NEWSWIRE) -- Achillion Pharmaceuticals, Inc. (Nasdaq:ACHN), a leader in the discovery and development of small molecule drugs to combat the most challenging infectious diseases, today announced that novel preclinical and clinical virology data on ACH-1625, a Phase 2 pan-genotypic protease inhibitor, was presented in an oral presentation at the 2012 Annual Conference of the Asian Pacific Association for the Study of the Liver (APASL 2012), February 16-19, 2012, in Taipei, Taiwan.

The oral presentation, "Characterization of Hepatitis C Virus Variants Detected in vitro and in vivo After Treatment with ACH-1625, a Potent HCV NS3 Protease Inhibitor," (Abstract PS01-05) was made by Mingjun Huang, Ph.D., Vice President of Virology at Achillion, during APASL 2012 on Friday, February 17. The presentation discussed the viral resistant mutations identified in preclinical and Phase 1 clinical studies. The analyses showed that not only did wild type hepatitis C virus (HCV) profoundly decline following exposure to ACH-1625, but also that no rebound of the virus carrying the most common resistant mutations, specifically those at loci 155, 156, 168, was observed in genotype 1 HCV patients. Furthermore, the majority of resistant mutants displayed reduced replication fitness in vitro and remained sensitive to other classes of direct-acting antiviral agents.

"These data reveal a very interesting phenomenon in which following 5-day ACH-1625 monotherapy there was persistent suppression of HCV viral load observed even in the presence of pre-existing resistant variants," commented Dr. Huang. "These ad hoc study data, along with previously announced Phase 2 clinical results demonstrating significant suppression of HCV viral RNA with 100% cEVR, and an emerging virology profile that suggests a potential to suppress resistant variants, lead us to believe that ACH-1625 is well positioned to become an integral part of the future treatment of HCV in combination with other oral direct acting antiviral agents including our own NS5A inhibitors."

"As ACH-1625 continues to deliver what we believe to be a best-in-class profile for the treatment of HCV, these data further highlight the attributes of this potent, combinable, and to date very well-tolerated compound for the treatment of potentially all types of chronic hepatitis C infection," commented Michael D. Kishbauch, President and Chief Executive Officer of Achillion. "We look forward to completing the current Phase 2 clinical trial of ACH-1625 and initiating all-oral, interferon-free combination studies with ACH-1625 later this year."

About Achillion Pharmaceuticals

Achillion is an innovative pharmaceutical company dedicated to bringing important new treatments to patients with infectious disease. Achillion's proven discovery and development teams have advanced multiple product candidates with novel mechanisms of action. Achillion is focused on solutions for the most challenging problems in infectious disease including hepatitis C 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 potency, safety, tolerability, effectiveness, combinability and other characteristics of ACH-1625; Achillion's expectations regarding timing for the commencement and completion of clinical trials of ACH-1625; the potential for ACH-1625 to play an important role in the future treatment of HCV in combination with other oral direct acting antiviral agents; and the potential for ACH-1625 to be a best-in-class HCV treatment. 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 ACH-1625 and its other product candidates; advance the development of ACH-1625 and its other 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; 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, 2010 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) 752-5510

         gschulman@achillion.com

         

         Investors:

         Mary Kay Fenton

         Achillion Pharmaceuticals, Inc.

         Tel. (203) 624-7000

         mfenton@achillion.com

         

         Media:

         Christin Culotta Miller

         Ogilvy PR

         Tel. (212) 880-5264

         christin.miller@ogilvy.com