Achillion Pharmaceuticals Announces Pricing of Public Offering of Common Stock

Thu Feb 21, 2013 8:00pm EST

* Reuters is not responsible for the content in this press release.

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
. 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 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

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
         Christin Culotta Miller
         Ogilvy PR
         Tel. (212) 880-5264
         Mary Kay Fenton
         Achillion Pharmaceuticals, Inc.
         Tel. (203) 624-7000
         Seth Lewis
         The Trout Group, LLC
         Tel. (646) 378-2952


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