Achillion Announces Updated Phase 2 Results Including Early Sustained Virologic Response on ACH-3102 Plus Ribavirin in Genotype

Achillion Announces Updated Phase 2 Results Including Early Sustained
Virologic Response on ACH-3102 Plus Ribavirin in Genotype 1b Treatment-Naive
Hepatitis C Patients

  - ACH-3102 deemed safe and well-tolerated following 12 weeks of therapy -
   - High barrier to resistance demonstrated with no on-treatment virologic
                           breakthrough observed -
  - Novel NS5A inhibitor study supports differentiated profile of ACH-3102 -

NEW HAVEN, Conn., April 23, 2013 (GLOBE NEWSWIRE) -- Achillion
Pharmaceuticals, Inc. (Nasdaq:ACHN) today announced updated interim safety and
efficacy results, including early sustained virologic response (SVR4) data,
from the pilot Phase 2 trial evaluating once-daily ACH-3102 plus ribavirin
(RBV) in treatment-naïve patients with genotype 1b, IL28B CC subtype, chronic
hepatitis C virus (HCV) infection. All of the 8 patients enrolled in the trial
completed 12 weeks of treatment with no virologic breakthrough observed.
ACH-3102 also demonstrated continued declines in HCV RNA in the presence of up
to six baseline mutations that are known to confer a high level of resistance
to 1^st generations NS5A inhibitors. ACH-3102 was deemed safe and
well-tolerated with no significant adverse events reported. In all, 75% of
patients (6 of 8) had HCV RNA < 25 IU/ml at the end of treatment and 63% (5 of
8) achieved early sustained virologic response 4 weeks (SVR4) after the
completion of therapy.

Dr. Andrew Muir, Principal Investigator and Assistant Professor of Medicine
and Director of Gastroenterology/Hepatology Research at Duke Clinical Research
Institute commented, "The preliminary results from this novel study of a
single DAA, an NS5A inhibitor, plus ribavirin demonstrates the safety, high
barrier to resistance, and preliminary efficacy of ACH-3102. The profound
activity of ACH-3102 as a single DAA, along with its safety profile and lack
of virologic breakthrough to date makes this a very promising compound to
study further in combination with other oral agents, including sovaprevir, for
the treatment of HCV."

Overall, ACH-3102 was well-tolerated and demonstrated a safety profile
consistent with that seen during Phase 1 trials in both healthy subjects and
HCV-infected patients. No patients experienced virologic breakthrough while on
treatment and no patients discontinued treatment due to an adverse event.
Final study results are expected to be submitted for presentation at a medical
conference later this year.

                              Virologic End Points
Total 8 subjects enrolled      RVR             ETR            SVR4
                              n = 8           n = 8          n = 8
# of subjects                  6 / 8           6 / 8*         5 / 8 **
(%)                            (75%)           (75%)         (63%)
RVR = Rapid Virologic Response, HCV RNA < LLOQ (< 25 IU/mL) at week 4 of
treatment
ETR = End of Treatment Response, HCV RNA < LLOQ (< 25 IU/mL) at week 12 of
treatment
* The 2 patients who did not achieve ETR were started on pegylated
interferon, ribavirin and telaprevir at the end of the 12-week treatment
period, and demonstrated undetectable viral levels beginning at week 13.
** 1 patient with virologic relapse at week 15.

"We believe that these interim results further strengthen our position that
ACH-3102 is a differentiated NS5A inhibitor possessing attributes that make it
a true second-generation compound," commented Michael D. Kishbauch, President
and Chief Executive Officer of Achillion. "The safety and efficacy profile
support our recently initiated Phase 2 -007 trial evaluating 12 weeks of our
protease inhibitor, sovaprevir, in combination with ACH-3012 for the treatment
of genotype 1 HCV. With that study now underway, we look forward to reporting
interim results beginning in the third quarter of this year, and will continue
to explore and execute opportunities to combine our agents with other
compounds that could further shorten the treatment duration or provide
additional flexibility for treatment regimens to broadly cure HCV."

About ACH-3102

The NS5A protein is a clinically validated target that serves multiple
functions at various stages of the HCV life cycle including involvement in
virion production, interaction with host proteins and association with
interferon-resistance. ACH-3102, Achillion's second generation NS5A inhibitor,
has demonstrated potent activity against all HCV genotypes in vitro and in
preclinical studies achieved additive to synergistic activity when combined
with NS3 protease inhibitors, NS5B polymerase inhibitors, interferon and
ribavirin. In preclinical studies, ACH-3102 demonstrated excellent potency, in
the pico-molar range, against wild type HCV RNA replication, as well as
potency against resistant mutants that have been identified in clinical
studies. ACH-3102 was deemed to be safe and well-tolerated in Phase 1
development and achieved mean maximal reductions in HCV RNA of 3.78 log[10]
after a single dose. ACH-3102 has been granted fast track designation by the
FDA and is currently being evaluated in Phase 2 for the treatment of HCV.

About HCV

The hepatitis C virus is the most common cause of viral hepatitis, which is an
inflammation of the liver. It is currently estimated that more than 170
million people are infected with HCV worldwide including more than 5 million
people in the United States, making HCV more than twice as widespread as HIV.
Three-fourths of the global HCV patient population is undiagnosed; it is a
silent epidemic and a major global health threat. Chronic hepatitis, if left
untreated, can lead to permanent liver damage that can result in the
development of liver cancer, liver failure or death. Few therapeutic options
currently exist for the treatment of HCV infection. The current standard of
care is limited by its specificity for certain types of HCV, significant
side-effect profile, and injectable route of administration.

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 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 expected potency,
safety, tolerability, effectiveness and other characteristics of sovaprevir
and ACH-3102; and Achillion's expectations regarding timing for the
commencement, completion and reporting of results of its clinical trials of
both ACH-3102 in combination with ribavirin and sovaprevir in combination with
ACH-3102. We may use words such as "expect," "anticipate," "project,"
"intend," "plan," "believe," "seek," " estimate," and "may" and similar
expressions to identify such forward-looking statements.Among the important
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; 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 duty 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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