Exhibit 99.1

ARIAD Begins Patient Enrollment in Two Clinical Studies of Its Lead
Cancer Product Candidate

    CAMBRIDGE, Mass.--(BUSINESS WIRE)--May 7, 2003--ARIAD
Pharmaceuticals, Inc. (Nasdaq: ARIA) today announced that it has begun
enrollment of cancer patients at major cancer centers in two Phase 1
clinical studies of AP23573, the Company's lead cancer product
candidate. The AP23573 class of cancer drugs inhibits the protein mTOR
and shrinks tumors by a novel mode of action - cancer-cell starvation
(metabolic arrest) through inhibition of nutrient uptake to tumor
cells, as well as inhibition of growth factor stimulation.
    This broadly applicable approach to cancer treatment is
anticipated to make ARIAD's product candidate particularly useful for
the treatment of advanced solid tumors, such as breast, kidney,
prostate, ovarian, and brain cancers - all clinical indications where
there is a great need for new small-molecule drugs.
    Using different dosing regimens, the clinical studies are designed
to understand the product candidate's safety and tolerability, its
pharmacokinetics (what the body does to the drug) and its
pharmacodynamics (what the drug does to the body). Since all
participants in these studies will be well-characterized cancer
patients, initial information describing the product candidate's
anti-tumor activity also will be obtained. Both clinical studies are
designed to enable rapid escalation of dose to therapeutic levels.
    Gene markers will be used to explore the relationship between the
anti-tumor activity and genetic mutations of the patients' tumors,
with the goal of streamlining future clinical development by being
able to optimally select patients for treatment with AP23573. It is
estimated that 35-50 patients will be enrolled in each of these two
simultaneous studies.
    "Expediting the clinical development of AP23573 is our top R&D
priority this year, and we anticipate initiating phase 2 clinical
development of AP23573 in targeted cancer indications as early as
possible next year," said Harvey J. Berger, M.D., chairman and chief
executive officer of ARIAD.
    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 and AP23573 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
             Tom Pearson, 610/407-9260
             or
             ARIAD Pharmaceuticals
             Kathy Lawton, 617/621-2345


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