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PROGENICS REPORTS
POSITIVE INTERIM PHASE 2 RESULTS FOR TWO DOSAGE FORMS OF NOVEL HIV THERAPY
PRO 140





–
Both intravenous and subcutaneous forms of PRO 140 showed potent and prolonged
activity and were generally well tolerated –




Washington, DC and Tarrytown,
NY – October 26, 2008 – Progenics Pharmaceuticals, Inc. (Nasdaq: PGNX)
today announced positive interim results from two separate phase 2 clinical
trials of PRO 140 for the treatment of HIV infection. Both intravenous and
subcutaneous forms of PRO 140, a novel viral-entry inhibitor, exhibited potent
and prolonged activity as measured by reductions in plasma levels of virus in
individuals with HIV infection. Interim results (based on the first 15 of 31
patients treated) from the study of intravenous PRO 140 were presented in
Washington, D.C. today as a “late-breaker” poster (a link to which can be found
at http://www.progenics.com/sci_cal.cfm) at the joint meeting of the
Interscience Conference on Antimicrobial Agents and Chemotherapy (ICAAC) and the
Infectious Diseases Society of America (IDSA). In this study, a 2.17
log10 mean
maximum reduction in viral load was observed in patients treated intravenously
with a single 10 mg/kg dose, and the antiviral response persisted for three
weeks post-treatment. The Company separately announced positive interim
results (based on the first 20 of 44 patients treated) from the first clinical
trial of subcutaneous PRO 140. In this study, the mean maximum viral load
reduction was 1.77 log10 for
patients treated subcutaneously with three weekly doses of 324 mg PRO 140, and
the antiviral response persisted for two weeks after the last dose. Both
intravenous and subcutaneous forms of PRO 140 were generally well tolerated in
these studies.






“The
viral load reductions observed for intravenous PRO 140 are similar in magnitude
to those observed for our most potent HIV drugs at this stage of development,”
said Jeffrey M. Jacobson, M.D., Professor of Medicine, Microbiology and
Immunology, Chief, Division of Infectious Diseases and HIV Medicine, Drexel
University College of Medicine and lead author of the ICAAC presentation. “The
findings underscore the efficiency with which PRO 140 blocks HIV’s access to
CCR5 and healthy cells in vivo. In addition, the antiviral and safety data for
subcutaneous PRO 140 are highly encouraging. Many patients are excited by the
potential for a potent and well-tolerated therapy that could be
self-administered and yet not provide a daily reminder of their
disease.”















PRO 140
is a humanized monoclonal antibody that blocks viral infection of healthy cells
by binding to CCR5, a co-receptor that is the principal molecular portal used by
HIV to enter and infect immune system cells. Some strains of HIV use the CXCR4
co-receptor as a portal of entry either exclusively or in addition to CCR5. CCR5
viral-entry inhibitors, such as PRO 140, are active in blocking infection in the
majority of HIV patients whose virus uses the CCR5 portal, but do not block the
entry of virus that uses the CXCR4 portal.




“The
interim analyses were conducted to provide timely information on the potential
feasibility of two attractive treatment options for PRO 140: monthly intravenous
and weekly subcutaneous dosing,” said Paul J. Maddon, M.D., Ph.D., Progenics
Pharmaceuticals’ Founder, Chief Executive Officer and Chief Science Officer.
“These interim data support the potential feasibility of both
options. Importantly, in our first clinical study of the subcutaneous form
of PRO 140, we observed significant and prolonged reductions in viral
load. Based on our discussions with the HIV community, we believe that
weekly subcutaneous dosing of a drug with a favorable tolerability profile would
be a desirable new treatment paradigm. Our intravenous form of PRO 140 also
exhibited substantial and sustained reductions in viral loads with a favorable
tolerability profile. We expect to obtain results from all patients
enrolled in both of these studies by early 2009, and these data will be used to
select a dosage form (intravenous or subcutaneous) for further clinical
development.”





Intravenous
PRO 140: Summary of interim phase 2 results





In the
intravenous phase 2 trial, single infusions of PRO 140 were evaluated in
HIV-infected individuals with early-stage disease, who had received no
antiretroviral therapy for at least three months and who had HIV-1 RNA viral
loads of greater than 5,000 copies/mL. Prior to treatment, all patients were
screened for the presence of virus that uses CCR5, and the absence of virus that
uses CXCR4, as the entry co-receptor. Subjects were monitored for 58 days
following treatment for safety and antiviral effects. A total of 31 individuals
were enrolled and approximately evenly randomized to receive a single dose of
placebo, PRO 140 5 mg/kg or PRO 140 10 mg/kg on day one. An interim analysis was
performed on safety and efficacy data from the first 15 subjects treated. There
were five subjects in each of the three dose groups.





Interim
results from this study reconfirmed the substantial antiviral activity observed
at the 5 mg/kg dose level in the earlier phase 1b trial, and also showed that
doubling the dose to 10 mg/kg increased the duration and magnitude of antiviral
response. Each of the five subjects treated with the 10 mg/kg dose experienced a
greater than 2.0 log10
(100-fold) reduction in viral load.





Figure 1
depicts the mean viral load reductions over time for the three dose groups. A
greater than 1.0 log10 (10-fold)
mean reduction in viral load was sustained until three weeks post-treatment at
the 10 mg/kg dose level, compared with two to three weeks at the 5 mg/kg dose
level in the present study and in the previous phase 1b trial.























Figure
1. Mean change in viral load over time for HIV-infected individuals following
single intravenous infusions of placebo, PRO 140 5 mg/kg or PRO 140 10
mg/kg.





Additional
key findings from the phase 2 interim analysis and the prior phase 1b study of
intravenous PRO 140 are summarized below. P-values reflect two-sided t-tests
compared to placebo after an overall analysis of variance (ANOVA) F-test was
found to be statistically significant.




§
              At
      5 mg/kg (phase 1b study): 1.83 log10
      mean maximum decrease in viral load (p < 0.0001) (see Progenics press
      release issued July 25, 2007)
 §
              At
      5 mg/kg (phase 2 study): 1.90 log10
      mean maximum decrease in viral load (p ≤
0.0001)
 §
              At
      10 mg/kg (phase 2 study): 2.17 log10
      mean maximum decrease in viral load (p ≤
  0.0001)
 §
              All
      subjects treated with 5 mg/kg experienced a greater than 1.0 log10
      maximum reduction in viral load
(p=0.0079).
  §
              All
      subjects treated with 10 mg/kg experienced a greater than 2.0 log10
      maximum reduction in viral load
(p=0.0079).
  §
              Following
      treatment with a single 10 mg/kg dose, a greater than 1.0 log10
      mean decrease in viral load was maintained for three weeks; at three
      weeks, the mean reduction was 1.55 log10
      (p=0.0005).














Intravenous doses of PRO 140 were
generally well tolerated compared to placebo. There were no drug-related serious
adverse events. There was no dose-limiting toxicity, nor any pattern of
toxicity, nor apparent safety signals.





Subcutaneous
PRO 140: Summary of interim phase 2 results





In the
phase 2 trial of subcutaneous PRO 140, a total of 44 HIV-infected individuals
meeting the same entry criteria as those for the intravenous PRO 140 study were
randomized to receive three weekly doses of 162 mg PRO 140, two bi-weekly doses
of 324 mg PRO 140, three weekly doses of 324 mg PRO 140, or placebo. An interim
analysis was performed on data from the first 20 subjects treated. The number of
subjects in each group was as follows: placebo (n=5), 162 mg PRO 140 weekly
(n=4), 324 mg PRO 140 biweekly (n=6) and 324 mg PRO 140 weekly
(n=5).





The
interim results provide initial proof of concept for subcutaneous PRO 140 as a
potent antiretroviral agent with prolonged and dose-dependent activity. Each of
the five subjects treated with weekly 324 mg doses experienced a greater than
1.0 log10 reduction
in viral load, with individual reductions ranging to 2.50 log10.





Figure 2
depicts the mean change in viral load over time for the four dose groups. In
both the 324 mg weekly and bi-weekly dose groups, a greater than 1.0 log10 mean
reduction in viral load was maintained for two weeks following administration of
the last dose.










Figure
2. Mean change in viral load over time for HIV-infected individuals receiving
multiple doses of subcutaneous PRO 140.

















Additional
key findings from the interim analysis of the phase 2 trial of subcutaneous PRO
140 are summarized below. P-values were determined as described
above.





§
            Statistically
      significant antiviral effects were observed for 324 mg PRO 140 dose
      administered weekly and bi-weekly; for the 162 mg dose, viral load
      reductions did not achieve significance compared to
    placebo.


§
            At
      324 mg, bi-weekly dosing: 1.34 log10
      mean maximum decrease in viral load
(p=0.0059)


§
            At
      324 mg, weekly dosing: 1.77 log10
      mean maximum decrease in viral load
(p=0.0006)


§
            At
      324 mg: 100% of subjects achieved a maximum reduction in viral load
      greater than 1.0 log10
      with weekly dosing (p=0.0079), and 67% achieved this level of reduction
      with bi-weekly dosing (p=0.061).





Subcutaneous
doses of PRO 140 were generally well tolerated compared to placebo.
Administration site reactions were reported in a minority of subjects and were
mild. There were no drug-related serious adverse events; any reported adverse
events were comparable between the treatment and placebo arms. There was no
dose-limiting toxicity, nor any pattern of toxicity, nor apparent safety
signals.





About
PRO 140





Discovered
by Progenics’ scientists, PRO 140 is a humanized monoclonal antibody that
binds to CCR5, a co-receptor characterized by Progenics and its collaborators in
1996 as the principal molecular portal used by HIV to enter and infect immune
system cells. Some strains of HIV use the CXCR4 co-receptor as a portal of entry
either exclusively or alternatively to CCR5. PRO 140 is a viral-entry inhibitor
that is designed to protect healthy cells from HIV infection. Unlike
small-molecule CCR5 antagonists, PRO 140 inhibits HIV entry at
concentrations that in
vitro do not appear to block CCR5’s natural activity of directing the
migration of immune cells towards sites of inflammation in the body. As a
monoclonal antibody, PRO 140 is not metabolized by the liver, and therefore
may have the potential for a better tolerability profile than many of the
existing small-molecule therapies for HIV infection. In February 2006,
PRO 140 was designated a Fast Track product by FDA for the treatment of HIV
infection.





Progenics
gratefully acknowledges the development funding it has received for PRO 140
from the National Institute of Allergy and Infectious Diseases, part of the
National Institutes of Health (Public Health Service award: 1 U19
AI066329).





(PGNX-C)













About
the Company





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. Principal programs are directed toward
gastroenterology, virology—including human immunodeficiency virus (HIV) and
hepatitis C virus (HCV) infections—and oncology. Progenics, in collaboration
with Wyeth, is developing RELISTORTM (methylnaltrexone bromide) for the treatment
of opioid-induced side effects. In the U.S., RELISTOR (methylnaltrexone bromide)
subcutaneous injection is indicated for the treatment of opioid-induced
constipation (OIC) in patients with advanced illness who are receiving
palliative care, when response to laxative therapy has not been sufficient. In
Canada, RELISTOR (methylnaltrexone bromide injection) for subcutaneous use is
indicated for the treatment of OIC in patients with advanced illness receiving
palliative care. In European member states and Iceland, Norway and
Liechtenstein, RELISTOR (methylnaltrexone bromide) subcutaneous injection is
indicated for the treatment of OIC in patients with advanced illness who are
receiving palliative care, when response to the usual laxative therapy has not
been sufficient. Marketing applications are pending for RELISTOR in Australia
and other countries. In the area of virology, Progenics is developing the HIV
entry inhibitor PRO 140, a humanized monoclonal antibody targeting the entry
co-receptor CCR5, which is in phase 2 clinical testing. Pre-clinical programs
for the development of novel HCV entry inhibitors are also underway. In the area
of oncology, the Company is conducting a phase 1 clinical trial of a human
monoclonal antibody-drug conjugate (ADC) for the treatment of prostate cancer—a
selectively targeted cytotoxic antibody directed against prostate-specific
membrane antigen (PSMA). PSMA is a protein found on the surface of prostate
cancer cells as well as in blood vessels supplying other solid tumors. Progenics
is also developing vaccines designed to treat prostate cancer by stimulating an
immune response to PSMA.




DISCLOSURE NOTICE: This document contains statements
that do not relate strictly to historical fact, any of which may be
forward-looking statements within the meaning of the Private Securities
Litigation Reform Act of 1995. When we use the words "anticipates," "plans,"
"expects" and similar expressions, we are identifying forward-looking
statements.






Forward-looking
statements involve known and unknown risks and uncertainties which may cause our
actual results, performance or achievements to be materially different from
those expressed or implied by forward-looking statements. While it is impossible
to identify or predict all such matters, this may result from, among other
things, the inherent uncertainty of the timing and success of, and expense
associated with, research, development, regulatory approval and
commercialization of our products and product candidates, including the risks
that clinical trials will not commence or proceed as planned; products appearing
promising in early trials will not demonstrate efficacy or safety in
larger-scale trials; clinical trial data on our products and product candidates
will be unfavorable; our products will not receive marketing approval from
regulators or, if approved, do not gain sufficient market acceptance to justify
development and commercialization costs; we, our collaborators or others might
identify side effects after the product is on the market; or efficacy or safety
concerns regarding marketed products, whether or not originating from subsequent
testing or other activities by us, governmental regulators, other entities or
organizations or otherwise, and whether or not scientifically justified, may
lead to product recalls, withdrawals of marketing approval, reformulation of the
product, additional pre-clinical testing or clinical trials, changes in labeling
of the product, the need for additional marketing applications, declining sales
or other adverse events.















We
are also subject to risks and uncertainties associated with the actions of our
corporate, academic and other collaborators and government regulatory agencies;
potential product liability; intellectual property, litigation, environmental
and other risks; the risk that licenses to intellectual property may be
terminated for our failure to satisfy performance milestones; the risk of
difficulties in, and regulatory compliance relating to, manufacturing products;
and the uncertainty of our future profitability.




Risks
and uncertainties also include general economic conditions, including interest
and currency exchange rate fluctuations and the availability of capital; changes
in generally accepted accounting principles; the impact of legislation and
regulatory compliance; the highly regulated nature of our business, including
government cost-containment initiatives and restrictions on third-party payments
for our products; trade buying patterns; the competitive climate of our
industry; and other factors set forth in our Annual Report on Form 10-K and
other reports filed with the U.S. Securities and Exchange Commission. In
particular, we cannot assure you that our lead product, RELISTORTM , will be
commercially successful or be approved in the future in other formulations,
indications or jurisdictions, or that any of our other programs will result in a
commercial product.




We
do not have a policy of updating or revising forward-looking statements and
assume no obligation to update any statements as a result of new information or
future events or developments. Thus, it should not be assumed that our silence
over time means that actual events are bearing out as expressed or implied in
forward-looking statements.







Editors
Note:




For more
information about Progenics Pharmaceuticals, Inc., please visit www.progenics.com.