Exhibit 99.1

Progenics Announces Results from Methylnaltrexone Phase 2 Clinical
Trial in Opioid-Induced Constipation

    TARRYTOWN, N.Y.--(BUSINESS WIRE)--April 30, 2003--

    -- Findings Confirm Open-Label Results, Support Ongoing Phase 3
                Clinical Program in Hospice Patients --

    Progenics Pharmaceuticals, Inc. (Nasdaq: PGNX) today announced
top-line results from a phase 2 clinical trial of its investigational
drug, methylnaltrexone (MNTX), for the treatment of opioid-induced
constipation.
    Bowel dysfunction is a debilitating problem for patients with
advanced medical illness who are being treated with narcotics for
pain. In December 2002, the Company reported preliminary results from
the open-label portion of this clinical study. Now, analysis of the
randomized double-blind results show that the study met its
objectives, and that the drug continued to show evidence that it was
well tolerated. The results confirm and extend the findings from the
previously reported open-label portion of the study and support the
dosing regimen selected for the ongoing phase 3 clinical trial that
began late last year. A presentation of the data is scheduled for the
40th Annual Meeting of the American Society of Clinical Oncology
(ASCO), in Chicago, in early June.
    "Terminally ill patients suffer from opioid-induced constipation
that is exacerbated by inadequate fluid and fiber intake, as well as
immobility caused by disease progression," said Robert J. Israel,
M.D., Progenics' Senior Vice President of Medical Affairs. "Therefore,
we were particularly pleased to see that patients in this study
laxated promptly after MNTX administration, typically within one hour.
We believe that with further study MNTX has the potential to be an
important new therapy for the supportive care of more than one-million
patients in the U.S. who die from advanced medical disease each year."
    The study enrolled 33 patients with advanced medical illness who
were experiencing opioid-induced constipation. Subjects were randomly
allocated to receive one of four fixed doses of subcutaneous MNTX (1.0
mg, 5 mg, 12.5 mg, or 20 mg). Patients were treated every-other-day
(days 1, 3 and 5) in a blinded fashion for one week, and laxation
times were recorded. On day seven, they were eligible to enter into
the open-label study for an additional three weeks.
    On average, 60% of patients who received doses greater than or
equal to 5 mg laxated within four hours as compared to less than 8% at
lower doses (p = less than 0.0001, Fisher's exact test, two tailed).
The median frequency of pre-dose laxations increased from two per week
to four-to-six bowel movements per week at the higher doses of MNTX.
Median time to laxation was approximately one hour after receiving
greater than or equal to 5 mg of MNTX.
    The results from the blinded portion of the study support the
weight-based dosing of the ongoing phase 3 clinical trial. At doses
equivalent to less than 0.05 mg/kg, the laxation rate was 7%, at 0.05
to 0.25 mg/kg it was 61%, and at greater than 0.25 mg/ kg it increased
to 69%, (p = less than 0.0001, Chi-square test, two tailed). The doses
chosen for phase 3 are 0.15 mg/kg, 0.30 mg/kg and placebo.-- MNTX was
well tolerated at clinically relevant doses, there were no serious
adverse events related to study medication, and there was no evidence
of breakthrough pain or opioid withdrawal. The most common side
effects were flatulence and transient abdominal cramping. These
symptoms were interpreted as activation of the gastrointestinal tract,
a necessary physiological prerequisite to bowel movement in patients
with significant constipation.
    Progenics is developing MNTX in three parallel clinical programs
to address unmet medical needs in broad markets. Subcutaneous dosing
of MNTX for opioid-induced bowel dysfunction in advanced medical
illness is being evaluated in a phase 3 clinical trial, intravenous
dosing for post-operative ileus is scheduled to begin phase 2 shortly,
and a phase 1 clinical trial of an oral formulation of MNTX for use in
individuals taking opioids chronically is planned for this year.
    Progenics Pharmaceuticals, Inc. of Tarrytown, NY, is a
biopharmaceutical company focusing on the development and
commercialization of innovative therapeutic products to treat the
unmet medical needs of patients with debilitating conditions and
life-threatening diseases. The Company applies its expertise in
immunology and molecular biology to develop biopharmaceuticals to
fight viral diseases, such as human immunodeficiency virus (HIV)
infection, and cancers, including malignant melanoma and prostate
cancer. In symptom management and supportive care, therapies are being
developed to provide patients with an improved quality of life.
Progenics' most clinically advanced product is methylnaltrexone, a
compound in phase 3 clinical testing that is designed to block the
debilitating side effects of opioid analgesics without interfering
with pain palliation. The Company is conducting multi-dose phase 2
clinical trials with its lead HIV product, PRO 542, a viral-entry
inhibitor and is in preclinical development with PRO 140 and other
follow-on product candidates in HIV infection. The Company is
developing cancer immunotherapies based on PSMA (prostate-specific
membrane antigen) technology and currently is conducting phase-1
clinical studies of a therapeutic prostate cancer vaccine. GMK is a
cancer vaccine in phase-3 clinical trials for the treatment of
malignant melanoma.
    DISCLOSURE NOTICE: The information contained in this document is
as of April 30, 2003. This press release contains forward-looking
statements. Any statements contained herein that are not statements of
historical fact may be forward-looking statements. When the Company
uses the words 'anticipates,' 'plans,' 'expects' and similar
expressions they are identifying forward-looking statements. Such
forward-looking statements involve risks and uncertainties which may
cause the Company's actual results, performance or achievements to be
materially different from those expressed or implied by
forward-looking statements. Such factors include, among others, the
uncertainties associated with product development, the risk that
clinical trials will not commence when or proceed as planned, the
risks and uncertainties associated with dependence upon the actions of
the Company's corporate, academic and other collaborators and of
government regulatory agencies, the risk that products that appear
promising in early clinical trials do not demonstrate efficacy in
larger-scale clinical trials, the uncertainty of future profitability
and other factors set forth more fully in the Company's Annual Report
on Form 10-K for the fiscal year ended December 31, 2002 and other
periodic filings with the Securities and Exchange Commission to which
investors are referred for further information. In particular, the
Company cannot assure you that any of the their programs will result
in a commercial product.
    Progenics does not have a policy of updating or revising
forward-looking statements and assumes no obligation to update any
forward-looking statements contained in this document as a result of
the new information or future events or developments. Thus it should
not be assumed that the Company's silence over time means that actual
events are bearing out as expressed or implied in such forward-looking
statements.

    Editor's Note: Additional information on Progenics is available at
http://www.progenics.com

    CONTACT: Progenics Pharmaceuticals, Inc., Tarrytown
             Richard W. Krawiec, Ph.D., 914/789-2800
             rkrawiec@progenics.com