Exhibit 99.1


Progenics Initiates Human Testing of Novel HIV Entry Inhibitor, PRO 140;
Phase 1 Trials Begin on First Monoclonal Antibody
to Block HIV Infection of Cells via CCR5

   LONDON--(BUSINESS WIRE)--May 4, 2004--Progenics Pharmaceuticals,
Inc. (Nasdaq: PGNX) today announced that it has begun phase 1 clinical
trials of a new HIV therapy - a humanized monoclonal antibody that
blocks infection by inhibiting the ability of the virus to enter
healthy cells. PRO 140 belongs to a new class of drugs, viral-entry
inhibitors, which are designed to prevent HIV (human immunodeficiency
virus, the causative agent of AIDS) from gaining access to cells of
the immune system. Unlike currently approved therapies, PRO 140 blocks
the CCR5 coreceptor, one of the principal portals HIV uses to enter
cells, that was discovered in 1996 by Progenics' scientists and their
collaborators. Because of its novel mechanism of action, PRO 140 has
the potential to be broadly active against viruses that have acquired
resistance to existing classes of antiretroviral therapies. The
announcement was made at the 4th Annual Fortis Bank Biotechnology
Conference in London.

   Unique product profile

   "There is an urgent and growing need for new HIV therapies," said
Jeffrey M. Jacobson, M.D., Assistant Chief and Program Director,
Division of Infectious Diseases, Beth Israel Medical Center and
Professor of Medicine, Albert Einstein College of Medicine in New York
City. "New therapies are needed to combat the rise in drug-resistant
strains of HIV, to lessen the significant treatment-related
toxicities, and to simplify the complex multidrug treatment regimens.
As a humanized monoclonal antibody against a novel target, PRO 140 has
the potential to address each of these important needs. Pending
successful completion of the current study, I look forward to seeing
this innovative product advanced into treatment studies in
HIV-infected individuals."
   Progenics has begun dosing healthy volunteers with PRO 140 in a
double-blind, randomized, placebo-controlled, dose-escalation phase 1
study. The primary goal of the trial is to evaluate the tolerability
and pharmacologic profile of PRO 140. This study is expected to
complete later this year, and phase 1b studies in HIV-infected
patients are planned thereafter.
   "PRO 140 belongs to a promising new class of anti-HIV agents known
as CCR5 coreceptor inhibitors. Preliminary proof-of-principle for this
class has recently been obtained by small-molecule inhibitors that are
in early clinical development," said William C. Olson, Ph.D., Vice
President, Research & Development at Progenics. "Whereas the
small-molecule inhibitors are antagonists that also block the natural
activity of CCR5, PRO 140 inhibited HIV infection without CCR5
receptor antagonism in laboratory studies. In addition, PRO 140
recognized a different region of CCR5 and thus may be active against
viruses that are resistant to small-molecule CCR5 antagonists. Lastly,
as a class, monoclonal antibody products often have favorable safety
profiles and serum half-lives that enable infrequent dosing."

   Background

   PRO 140 is a humanized monoclonal antibody designed to bind CCR5
on immune-system cells and thereby shield the cells from infection
with HIV. PRO 140 is highly specific in targeting a site on CCR5 that
is utilized by HIV without interfering with the normal function of
CCR5.
   CCR5 is a chemokine receptor expressed on the surface of certain
immune system cells that plays a key role in the inflammatory
response. In 1996, Progenics scientists and their collaborators
discovered that HIV uses CCR5 as a principal portal to gain entry into
and infect the host cell. In order to reproduce, HIV must enter a cell
and incorporate its genetic material into the cell's DNA, thereby
commandeering the host into producing numerous copies of the virus.
These new viruses are then released into the bloodstream to infect
other cells. Viral-entry inhibitors like PRO 140 are designed to stem
this cycle of infection and reproduction by blocking virus before it
enters a healthy cell, whereas conventional HIV medications work by
inhibiting viral reproduction only after the virus has infected the
host cell.
   The goal of the phase 1 study is to assess the tolerability,
pharmacology, and immunogenicity of PRO 140 in healthy volunteers.
Unlike its mouse-based predecessor, humanized PRO 140 is designed to
be suitable for repeat dosing in humans. Humanization of the PRO 140
monoclonal antibody was accomplished under a collaborative agreement
with Protein Design Labs, Inc. (Nasdaq: PDLI).
   In laboratory studies, PRO 140 has demonstrated potent,
broad-spectrum antiviral activity against more than 40 genetically
diverse HIV strains isolated directly from infected individuals.
Additional studies have demonstrated that HIV failed to develop
resistance to PRO 140 despite 40 weeks of continued exposure to the
drug in vitro. This period is considerably longer than that required
for HIV to develop resistance to other classes of antiviral agents in
similar laboratory studies. In other preclinical experiments, multiple
doses of PRO 140 reduced, and then maintained, viral loads at
undetectable levels for the duration of therapy in a well-recognized
animal model of HIV infection, without the emergence of viral
resistance. Sustaining undetectably low levels of virus in the blood
is a primary goal of HIV therapy.
   In these preclinical models, PRO 140 was shown to be effective at
protecting both primary T-cells and macrophages, immune system cells
that provide the major targets for HIV infection in vivo. In the
laboratory, PRO 140 was also combined with other viral-entry
inhibitors. A "triple cocktail" of PRO 542, PRO 140 and Fuzeon(TM),
each of which inhibits a different step in the sequence of events
leading to the entry of HIV into target cells, acted synergistically
to block infection of healthy cells. The multi-step nature of HIV
entry into cells--attachment, co-receptor binding and fusion--may
leave the virus susceptible to inhibition by combinations of drugs
that act at different stages of the process. Progenics'
investigational drugs PRO 542 and PRO 140 block viral attachment and
subsequent co-receptor binding, respectively. Fuzeon, a drug developed
by Trimeris and Roche, blocks the third step in the entry process,
virus-to-cell fusion.
   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 has five product candidates in
clinical development and several others in preclinical development. In
symptom management and supportive care, the Company is developing
methylnaltrexone (MNTX) to treat the debilitating side effects of
opioid-based pain relievers without interfering with pain relief. MNTX
is in pivotal phase 3 clinical testing for treatment of opioid-induced
constipation in patients with advanced medical illness and may be the
Company's first product candidate to be approved for marketing. In the
area of HIV infection, the Company is developing viral-entry
inhibitors, including PRO 542, a genetically engineered molecule
designed to selectively target and neutralize HIV (in phase 2
studies), and PRO 140, a monoclonal antibody designed to target the
HIV coreceptor CCR5 (in phase 1 studies). In addition, the Company is
conducting research on a novel prophylactic HIV vaccine. The Company
is developing immunotherapies for prostate cancer, including
monoclonal antibodies directed against prostate-specific membrane
antigen (PSMA), a protein found on the surface of prostate cancer
cells. The Company is also developing vaccines designed to stimulate
an immune response to PSMA. A recombinant PSMA vaccine is in phase 1
clinical testing. The Company is also studying a cancer vaccine, GMK,
in phase 3 clinical trials for the treatment of malignant melanoma.

   DISCLOSURE NOTICE: The information contained in this document is
current as of May 4, 2004. 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, it is 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 or proceed as planned, the risks and
uncertainties associated with dependence upon the actions of our
corporate, academic and other collaborators and of government
regulatory agencies, the risk that our licenses to intellectual
property may be terminated because of our failure to have satisfied
performance milestones, the risk that products that appear promising
in early clinical trials do not demonstrate efficacy in larger-scale
clinical trials, the risk that we may not be able to manufacture
commercial quantities of our products, 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, 2003
and other reports filed with the Securities and Exchange Commission,
to which investors are referred for further information. In
particular, the Company cannot assure you that any of its 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
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 available at
http://www.progenics.com.

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