Exhibit 99.1

        ARIAD's Oncology Product, AP23464, Effective in Gleevec-Resistant
   Leukemia Cells; Study Led By Gleevec Pioneer Presented At American Society
                             of Hematology Meeting

    CAMBRIDGE, Mass.--(BUSINESS WIRE)--Dec. 5, 2003--ARIAD
Pharmaceuticals, Inc. (Nasdaq: ARIA) today announced, for the first
time, that AP23464, its lead product candidate to treat certain forms
of leukemia, is highly effective in blocking the growth of leukemia
cells harboring clinically relevant mutations commonly observed in
patients who have become resistant to Gleevec(TM) (imatinib) - today's
mainstay of leukemia treatment. The research was conducted by a team
headed by Brian Druker, M.D., Jeld-Wen Chair of Leukemia Research and
Professor of Medicine, Oregon Health & Science University Cancer
Center, who played a key role in the discovery and development of
Gleevec.
    Although Gleevec is an effective treatment of chronic myelogenous
leukemia (CML), relapse is occurring in a growing number of patients,
especially those with advanced-stage disease. Most patients who
develop resistance to Gleevec have leukemias with readily identifiable
mutant Abl proteins not inhibited by Gleevec, leading to reactivation
of excessive Abl activity.
    AP23464 is a promising product candidate for the treatment of such
patients because of its potency against a broader array of therapeutic
targets, including the native and mutated forms of Abl. The latest
study also confirmed that AP23464 is substantially more potent than
Gleevec in blocking Abl.
    "Dr. Druker's groundbreaking work in treating patients with
leukemia has been widely recognized by the hematology community. His
group's research provides persuasive evidence that AP23464 may be a
compelling alternative or complement to Gleevec - both for
Gleevec-resistant patients and as primary therapy for certain forms of
leukemia. These data should facilitate filing of an IND for AP23464 by
the end of next year," said Harvey J. Berger, M.D., chairman and chief
executive officer of ARIAD.
    ARIAD's small molecule, AP23464, is designed not only to treat
certain forms of leukemia but also to treat and prevent the spread of
cancer by inhibiting the activity of another cancer-related protein
Src, which regulates the process by which cancer cells spread from
primary to distant sites in the body.
    The abstract by Thomas O'Hare, et al, "Potent inhibition of
imatinib-resistant variants of Bcr-Abl by a novel dual selective
Src/Abl kinase inhibitor AP23464: Implications for CML therapy," will
be presented on December 7, 2003 at the forty-fifth annual meeting of
the American Society of Hematology (ASH) and is available on the ASH
website (http://www.hematology.org/meeting/). Further information
about Dr. Druker's ongoing research program can be found on the web
(http://www.ohsu.edu/pmcb/facultyresearch/druker.shtml).

    Gleevec is a trademark of Novartis AG.

    ARIAD is engaged in the discovery and development of breakthrough
medicines that regulate cell signaling with small molecules. The
Company is developing a comprehensive approach to the treatment of
cancer and is primarily focused on a series of product candidates for
targeted oncology indications. ARIAD also has an exclusive license to
pioneering technology and patents related to the discovery,
development and use of drugs that regulate NF-(kappa)B cell-signaling
activity, which has been implicated in many major diseases.
    Additional information about ARIAD can be found on the web at
http://www.ariad.com.

    Some of the matters discussed herein are "forward-looking
statements" within the meaning of the Private Securities Litigation
Reform Act of 1995. Such statements are identified by the use of words
such as "anticipate," "estimate," "expect," "project," "intend,"
"plan," "believe," and other words and terms of similar meaning in
connection with any discussion of future operating or financial
performance. Such statements are based on management's current
expectations and are subject to certain factors, risks and
uncertainties that may cause actual results, outcome of events, timing
and performance to differ materially from those expressed or implied
by such forward-looking statements. These risks include, but are not
limited to, risks and uncertainties regarding the Company's ability to
conduct preclinical and clinical studies of its product candidates and
the results of such studies, regulatory oversight, intellectual
property claims, the timing, scope, cost and outcome of legal
proceedings, future capital needs, key employees, dependence on the
Company's collaborators and manufacturers, markets, economic
conditions, products, services, prices, reimbursement rates,
competition and other risks detailed in the Company's public filings
with the Securities and Exchange Commission, including ARIAD's Annual
Report on Form 10-K for the fiscal year ended December 31, 2002. The
information contained in this document is believed to be current as of
the date of original issue. The Company does not intend to update any
of the forward-looking statements after the date of this document to
conform these statements to actual results or to changes in the
Company's expectations, except as required by law.


    CONTACT: ARIAD Pharmaceuticals, Inc.
             Tom Pearson, 610-407-9260
             OR
             Kathy Lawton, 617-621-2345