EXHIBIT 99.1
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            ARIAD Announces Proposed Public Offering of Common Stock

    CAMBRIDGE, Mass.--(BUSINESS WIRE)--Aug. 1, 2005--ARIAD
Pharmaceuticals, Inc. (Nasdaq: ARIA) today announced that it is filing
a prospectus supplement with the Securities and Exchange Commission
related to an underwritten public offering of 6,000,000 shares of
common stock under an existing shelf registration statement. The
underwriters have been granted the option to purchase up to an
additional 900,000 shares if they sell more than 6,000,000 shares in
the offering. All of the shares are being sold by ARIAD.
    Lehman Brothers Inc. is acting as sole book-running manager in
this offering. Lazard Capital Markets LLC and SG Cowen & Co., LLC are
acting as co-managers.

    This press release does not constitute an offer to sell or the
solicitation of an offer to buy any of the securities, nor shall there
be any sale of the securities in any state in which such offer,
solicitation or sale would be unlawful prior to registration or
qualification under the securities laws of any such state. A
prospectus supplement relating to these securities is being filed with
the Securities and Exchange Commission. This offering of the shares of
common stock may be made only by means of the prospectus supplement
and related prospectus, a copy of which is available from Lehman
Brothers, Inc., Prospectus Department, c/o ADP Financial Services,
Integrated Distribution Services, 1155 Long Island Avenue, Edgewood,
New York 11717, monica_castillo@adp.com or at the Securities and
Exchange Commission's website at www.sec.gov.

    ARIAD is engaged in the discovery and development of breakthrough
medicines to treat cancer by regulating cell signaling with small
molecules.

    CONTACT: ARIAD Pharmaceuticals, Inc.
             Edward Fitzgerald (Investors)
             617-621-2345
             or
             Pure Communications
             Andrea Johnston (Media)
             910-616-5858