Exhibit 99.1

 ARIAD Reports Positive Early Phase 2 Results on AP23573, Novel mTOR
        Inhibitor, in Patients with Advanced Sarcomas at ASCO;
        Data Show Clinical Benefit and Symptomatic Improvement

    ORLANDO, Fla. and CAMBRIDGE, Mass.--(BUSINESS WIRE)--May 16,
2005--ARIAD Pharmaceuticals, Inc. (Nasdaq:ARIA) today announced, for
the first time, that its novel mTOR inhibitor, AP23573, administered
as a single agent, provides striking clinical benefit and symptomatic
improvement in advanced sarcoma patients across multiple sarcoma
subtypes in an ongoing Phase 2 multicenter clinical trial. Almost all
the patients had failed alternative anti-cancer treatments and had
progressive disease upon entering the trial. Generally, these patients
have a median life expectancy of about one year.

    Patient Enrollment

    The trial began patient enrollment seven months ago in October
2004. Eighty-two patients have been enrolled, followed by a pause in
enrollment specified in the protocol based on the trial design. As of
the date of analysis, 52 of these patients were evaluable through at
least four months on AP23573 treatment - the minimum duration for
assessing protocol-defined clinical-benefit response. Full enrollment
of 176 patients is expected within two to three months.

    Clinical-benefit Response and Symptomatic Improvement

    Thirty-seven percent (37%) of evaluable patients (19/52) in the
trial have clinical-benefit responses - sustained anti-tumor activity
as defined by strict RECIST guidelines - including three patients with
partial responses (confirmed tumor regression >30%) and sixteen
patients with stable disease for at least four months. Responding
patients continue on trial receiving drug. Five of these patients have
demonstrated stable disease for at least six months.
    Six-month progression-free survival or sustained disease
stabilization is becoming a well-recognized surrogate endpoint for
long-term survival benefit in patients with advanced sarcomas.
Estimates of progression-free survival rates reported by the EORTC
Soft Tissue and Bone Sarcoma Group (van Glabbeke et al, 2002) derived
from their clinical-trials database provide a benchmark for evaluating
the initial AP23573 Phase 2 clinical data. The EORTC six-month
progression-free survival rate for patients who received inactive
chemotherapies was estimated to be only 8%, which can serve as a
comparative control for assessing new treatments for sarcoma such as
AP23573.
    In addition, in an analysis from one major center, 72% (23/32) of
patients that entered the AP23573 Phase 2 trial with tumor-related
clinical symptoms (e.g., pain, shortness of breath and cough)
demonstrated clinically beneficial improvement in these symptoms
during AP23573 treatment.
    "Given the absence of any effective treatments for advanced
soft-tissue sarcomas or refractory bone sarcomas that have spread, the
initial Phase 2 results being reported today are particularly
meaningful for patients with this devastating disease and will form
the basis for designing our initial registration trial of AP23573,
which we expect to begin by early 2006," said Camille L. Bedrosian,
M.D., chief medical officer of ARIAD.

    Functional Imaging as In Vivo Biomarker

    Fifty-three patients also underwent glucose-radiotracer positron
emission tomographic (PET) imaging as an in vivo biomarker to
determine whether functional imaging early in the course of treatment
could predict the clinical response to AP23573. The relationship
between the mTOR cell-signaling and glucose metabolic pathways
provides a strong mechanistic rationale for the use of PET imaging in
conjunction with this glucose radiotracer as a non-invasive indicator
of in vivo mTOR activity.
    The decrease in glucose metabolism visualized with PET imaging in
the first week of AP23573 treatment was substantially greater in
patients with AP23573 anti-tumor responses than in those patients that
progressed. This trial provides the first promising indication of the
utility of functional imaging to prospectively identify those patients
likely to benefit clinically from mTOR inhibition with AP23573
treatment.

    Trial Objective and Design

    The primary objective of this multicenter clinical trial is to
assess the efficacy of AP23573 in four groups of sarcomas: (1) bone
sarcoma, (2) leiomyosarcoma, (3) liposarcoma, and (4) other soft
tissue sarcomas. Patients receive a fixed dose of 12.5 mg of AP23573
intravenously, using a daily dosing regimen of drug (five days on,
nine days off, drug).
    The trial uses Simon's two-stage design within each of these
sarcoma groups. Four of the initial 19 patients within each group must
exhibit a predefined four-month clinical-benefit response based on
strict RECIST guidelines before the group can be expanded and
enrollment to 44 patients continued. While the full set of patients
enrolled in stage 1 of the trial are being followed, further
enrollment in the group is paused. Since the strict criteria for
continued enrollment have already been met in three of the four
cohorts (all except liposarcoma), enrollment into stage 2 of the
two-stage design is currently proceeding. Expansion of the liposarcoma
group is expected shortly pending review of additional initial
response data.
    These clinical results are being presented at the 2005 American
Society of Clinical Oncology (ASCO) annual meeting in Orlando, Florida
by clinical investigators, Sant P. Chawla, M.D. (abstract 9068) and
Kamalesh K. Sankhala, M.D. (abstract 9028).

    Reference

    Van Glabbeke, M., Verweij, J., Judson, I., et al. Progression-free
rate as the principal end-point for phase II trials in soft-tissue
sarcomas. European Journal of Cancer 38:543-549, 2002.

    About Sarcoma

    Sarcomas are cancers of the connective tissue, including bones,
muscles, fat, cartilage, and joints and do not discriminate by age,
gender or race. Sarcomas can arise anywhere in the body and are
divided into two main groups - bone tumors and soft tissue sarcomas.
They are further sub-classified based on the type of cell or tissue
from which the tumor developed. There are approximately 12,000 new
cases of sarcoma diagnosed each year in the United States and
approximately 100,000 sarcoma patients overall in the United States.
More information about sarcomas is available at
http://www.curesarcoma.org and at http://www.sarcoma.net/facts.htm.

    About AP23573

    The small-molecule drug, AP23573, starves cancer cells and shrinks
tumors by inhibiting the critical cell-signaling protein, mTOR, which
regulates the response of tumor cells to nutrients and growth factors,
and controls tumor blood supply and angiogenesis through effects on
Vascular Endothelial Growth Factor (VEGF) in tumor and endothelial
cells. AP23573 also blocks the proliferation and migration of vascular
smooth muscle cells, the primary cause of narrowing and reblockage of
injured arteries, and is an analog of sirolimus, another mTOR
inhibitor that has been approved for use in drug-eluting stents.
AP23573 is currently in Phase 1 and 2 clinical trials in patients with
solid tumors and hematologic cancers. AP23573 has been designated a
fast-track product by the U.S. Food and Drug Administration for the
treatment of soft tissue and bone sarcomas.

    About ARIAD

    ARIAD is engaged in the discovery and development of breakthrough
medicines to treat disease by regulating cell signaling with small
molecules. The Company is developing a comprehensive approach to
patients with cancer that addresses the greatest medical need -
aggressive and advanced-stage cancers for which current treatments are
inadequate. Medinol Ltd. also is developing stents and other medical
devices that deliver ARIAD's lead cancer product candidate to prevent
reblockage at sites of vascular injury following stent-assisted
angioplasty. ARIAD has an exclusive license to pioneering technology
and patents related to certain NF-(kappa)B treatment methods, and the
discovery and development of drugs to regulate NF-(kappa)B
cell-signaling activity, which may be useful in treating certain
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
accurately estimate the timing and actual research and development
expenses and other costs associated with the preclinical and clinical
development and manufacture of our product candidates, the adequacy of
our capital resources and the availability of additional funding,
risks and uncertainties regarding our ability to manufacture our
product candidates on a commercial scale or to supply our product
candidates to our collaborator for use in its product candidates,
risks and uncertainties regarding our and our collaborator's ability
to successfully enroll and conduct preclinical and clinical studies of
product candidates, including our product candidate to treat cancer
described in this release and our collaborator's medical device
product candidates to treat vascular disease, risks and uncertainties
that clinical trial results at any phase of development including
those described in this release may be adverse or may not be
predictive of future results or lead to regulatory approval of any of
our or our collaborator's product candidates, risks and uncertainties
of third-party intellectual property claims relating to our and our
collaborator's product candidates, and risks and uncertainties
relating to regulatory oversight, the timing, scope, cost and outcome
of legal proceedings, including litigation concerning our NF-(kappa)B
patent portfolio, future capital needs, key employees, dependence on
our 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, as
amended, for the fiscal year ended December 31, 2004. 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 (Investors), 617-621-2345
             or
             Pure Communications
             Sheryl Seapy (Media), 949-608-0841