Achillion Pharmaceuticals Announces Pricing of Public Offering of Common Stock

Achillion Pharmaceuticals Announces Pricing of Public Offering of Common Stock

NEW HAVEN, Conn., Feb. 21, 2013 (GLOBE NEWSWIRE) -- Achillion Pharmaceuticals,
Inc. (Nasdaq:ACHN) announced today the pricing of an underwritten public
offering of 15,000,000 shares of its common stock at a price to the public of
$8.40 per share. The net proceeds to Achillion from the sale of the shares,
after deducting underwriting discounts and commissions and estimated offering
expenses, are expected to be approximately $118.5 million. The offering is
expected to close on February 27, 2013, subject to customary closing
conditions. Citigroup and Leerink Swann LLC are acting as joint book-running
managers, and JMP Securities LLC, Piper Jaffray & Co. and Wells Fargo
Securities, LLC are acting as co-managers for the offering.

Achillion has granted the underwriters a 30-day option to purchase up to an
additional 2,250,000 shares of its common stock. The expected net proceeds to
Achillion referenced above do not include any net proceeds that Achillion
would receive if the underwriters exercise such option.

The offering is being made by Achillion pursuant to a shelf registration
statement previously filed with and declared effective by the Securities and
Exchange Commission (SEC).A prospectus supplement related to the offering
will be filed with the SEC and will be available on the SEC's website at
http://www.sec.gov.Copies of the prospectus supplement and accompanying
prospectus relating to this offering may be obtained from Citigroup, c/o
Broadridge Financial Solutions, 1155 Long Island Avenue, Edgewood, NY 11717,
via telephone at 1-800-831-9146 or email at batprospectusdept@citi.com or from
Leerink Swann LLC, Attention: Syndicate Department, One Federal Street, 37th
Floor, Boston, MA 02110, via telephone number (800) 808-7525, Ext. 4814, or
email at syndicate@leerink.com.

This press release shall not constitute an offer to sell, or the solicitation
of an offer to buy, nor will there be any sale of, these securities in any
state or other jurisdiction in which such offer, solicitation or sale would be
unlawful prior to the registration or qualification under the securities laws
of such state or other jurisdiction.

About Achillion Pharmaceuticals, Inc.

Achillion is an innovative pharmaceutical company dedicated to bringing
important new treatments to patients with infectious disease.

Forward-Looking Statements

This press release includes "forward-looking statements" made under the
provisions of the Private Securities Litigation Reform Act of
1995.Forward-looking statements include statements, other than statements of
historical fact, regarding, without limitation, the completion, timing and
size of Achillion's proposed public offering and the use of proceeds
therefrom.In some cases, words such as "will," "expect" or other comparable
words identify forward-looking statements.Actual results, performance or
experience may differ materially from those expressed or implied by any
forward-looking statement as a result of various important factors, including
without limitation risks and uncertainties relating to Achillion's business
and financial condition, general market conditions and the satisfaction of
customary closing conditions associated with the proposed public
offering.Factors that may cause such a difference include, without
limitation, risks and uncertainties related to whether or not Achillion will
be able to raise capital through the sale of shares of common stock, the final
terms of the proposed offering, market and other conditions, the satisfaction
of customary closing conditions related to the proposed public offering and
the impact of general economic, industry or political conditions in the United
States or internationally. Risks and uncertainties that Achillion faces are
described in greater detail under the heading "Risk Factors" in its 2012
Annual Report on Form 10-K and its subsequent SEC filings, as well as other
filings that it makes with the SEC. As a result of the risks and
uncertainties, the results or events indicated by any forward-looking
statement may not occur. Achillion cautions you not to place undue reliance on
any forward-looking statement.

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:
         Christin Culotta Miller
         Ogilvy PR
         Tel. (212) 880-5264
         christin.miller@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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