PRAECIS PHARMACEUTICALS INCORPORATED Presents Interim Clinical Data on PPI-2458 at the 18th EORTC-NCI-AACR Symposium

  
    
  
  
    
      PRAECIS PHARMACEUTICALS INCORPORATED (NASDAQ: PRCS) today announced that 
      it is presenting interim clinical data from an ongoing phase 1 trial of 
      its investigational compound, PPI-2458, at the 18th 
      EORTC-NCI-AACR Symposium on “Molecular Targets 
      and Cancer Therapeutics” being held from 
      Tuesday, November 7 to Friday, November 10, 2006 at the Prague Congress 
      Centre in Prague, Czech Republic. The data being presented is entitled “A 
      Phase 1 Dose Escalation Safety & Tolerance Study of PPI-2458 in Subjects 
      with Non-Hodgkin’s Lymphoma or Solid Tumors” 
      (Abstract #139). Additionally, PRAECIS is presenting research on the 
      potential role of PPI-2458 in melanoma in a poster entitled “Effects 
      of PPI-2458, an inhibitor of methionine aminopeptidase type-2 on growth 
      of melanoma and expression of MITF” (Abstract 
      #349). The posters may be viewed on the Company’s 
      website (http://www.praecis.com) in 
      the “Investors” 
      section, under “Presentations.”
    
    
      PPI-2458 - Interim Clinical Data:
    
    
      PPI-2458 is a novel, proprietary, orally available small molecule that 
      specifically targets methionine aminopeptidase-2 (MetAP-2). MetAP-2 has 
      previously been demonstrated to be overexpressed in certain human 
      cancers, including non-Hodgkin’s lymphoma 
      (NHL). Study 2458-04-01 is a multi-center, open-label, dose-escalation 
      study designed to determine the maximum tolerated dose (MTD) of PPI-2458 
      in patients with NHL or solid tumors. PPI-2458 is administered to 
      subjects orally every other day (QOD) for two 28 day cycles. Subjects 
      are allowed to continue treatment, in the absence of unacceptable 
      toxicity, until evidence of disease progression. The primary endpoint of 
      the study is safety, with disease response being evaluated as a 
      secondary endpoint. Additional secondary endpoints include 
      pharmacokinetic and pharmacodynamic data.
    
    
      Interim results presented include data for 32 subjects that have been 
      treated across 4 dose cohorts ranging from 2 mg to 8 mg. Data to date 
      suggests that PPI-2458 is well tolerated at doses up to 8 mg. The 
      maximum tolerated dose has not been determined and treatment is 
      currently ongoing in a fifth cohort of subjects receiving a 12 mg dose.
    
    
      Results reported for this trial also include investigation of 
      pharmacokinetics, pharmacodynamics and tumor assessments. The 
      pharmacodynamic endpoint is assessed using PRAECIS’ 
      proprietary MetAP-2 assay. Results reported show that MetAP-2 in white 
      blood cells is substantially inhibited by PPI-2458 in patients across 
      each cohort. In addition, 7 subjects across the first 4 cohorts have 
      been reported by the clinical investigators to have stable disease at 
      the end of the first 2 cycles of treatment.
    
    
      “Based on study results to date, PPI-2458 
      appears to be an agent with unique and exciting mechanisms (MetAP-2 and 
      microphthalmia-associated transcription factor (MITF) protein), and as 
      the Phase 1 study proceeds, there is growing data to support a focused 
      Phase 2 clinical development plan,” stated 
      Dr. J. Paul Eder, Principal Investigator for the Phase 1 clinical trial 
      and Clinical Director of Translational Pharmacology at the Dana-Farber 
      Cancer Institute in Boston, Massachusetts. Dr. Eder continued, “There 
      is indication of substantial target inhibition in a surrogate tissue and 
      we plan to determine the effects of PPI-2458 in patient tumor samples in 
      future cohorts. As the dose has escalated, we have been encouraged by 
      the increased duration of treatment without clinically significant 
      toxicity that has been observed for these otherwise treatment refractory 
      patients."
    
    
      “We are pleased to see the encouraging safety 
      and tolerability data in this Phase 1 trial and we continue to believe 
      that PPI-2458 holds promise for the treatment of a wide range of cancer 
      types,” stated Kevin F. McLaughlin, President 
      and Chief Executive Officer of PRAECIS.
    
    
      Additional information about the Company’s 
      ongoing clinical trial for PPI-2458 can be accessed on the Internet at www.clinicaltrials.gov. 
      The Company is currently planning Phase 2 clinical development protocols 
      in oncology.
    
    
      PPI-2458 - Preclinical Research in 
      Melanoma:
    
    
      One tumor type of particular interest for PPI-2458 treatment is 
      melanoma. In a poster presented by Gerhard Hannig, Ph.D., Director of 
      Cellular and Molecular Pharmacology, PRAECIS describes data on research 
      of the growth inhibitory effects of PPI-2458 on human melanoma cell 
      lines. These data demonstrate the selective growth inhibition of 
      melanoma cell lines both in cell-based studies and in animal models and 
      illustrate a novel mechanism of action for PPI-2458 in melanoma. This 
      inhibition of melanoma growth appears to be directly linked to MetAP-2 
      inhibition in these studies.
    
    
      In addition, PRAECIS reports that PPI-2458 decreases the cellular level 
      of microphthalmia-associated transcription factor (MITF) protein, a 
      master regulator of the melanocyte lineage, in melanoma cell lines. 
      Recently, MITF has been shown to be a novel melanoma survival oncogene 
      and this protein may play a potentially important role in the 
      development and progression of melanoma in humans. Melanoma patients 
      with metastatic disease and high MITF expression in tumor tissue tend to 
      have worse overall outcomes than patients with lower levels of this 
      protein in tumor tissue as described in a recent publication in the 
      journal Nature. (Nature 436, 2005, 117)
    
    
      As part of its current planning for further clinical development of 
      PPI-2458 in oncology, PRAECIS will consider this preclinical data on 
      melanoma as well as preclinical and clinical data with respect to 
      several other cancer types.
    
    
      About PRAECIS
    
    
      PRAECIS PHARMACEUTICALS INCORPORATED is a biopharmaceutical company 
      focused on utilizing its proprietary technologies for the discovery and 
      development of novel compounds that have the potential to address unmet 
      medical needs or improve existing therapies. PRAECIS has a novel MetAP-2 
      inhibitor, PPI-2458, in clinical development for cancer indications, 
      including non-Hodgkin’s lymphoma and solid 
      tumors, an innovative drug discovery technology, DirectSelect™, 
      which enables the generation and practical use of ultra-large libraries 
      for the discovery of orally active compounds for drug development, and a 
      research and development program aimed at identifying one or more 
      selective S1P-1 agonist compounds to take forward into clinical testing.
    
    
      This news release contains forward-looking statements regarding the 
      Company’s continued development of PPI-2458 
      for cancer and autoimmune disorders. These statements are based on the 
      Company’s current beliefs and expectations as 
      to future outcomes and are not guarantees of such outcomes or of future 
      performance. These statements are subject to numerous risks, 
      uncertainties and assumptions that could cause actual events and results 
      to differ from those expected or anticipated, including, but not limited 
      to, the Company’s ability to continue 
      development of and successfully partner or otherwise obtain funding for 
      its PPI-2458 program, the Company’s ability 
      to continue to manage operating expenses and to retain key employees, 
      unexpected expenditures, the timing and content of decisions made by the 
      FDA, unexpected results in ongoing and future clinical or preclinical 
      trials, and the need for additional research and testing, including as a 
      result of unanticipated determinations by regulatory authorities, as 
      well as the risks set forth from time to time in the Company’s 
      filings with the Securities and Exchange Commission, including but not 
      limited to the various risks discussed in the Company’s 
      Quarterly Report on Form 10-Q for the quarter ended June 30, 2006. 
      The Company undertakes no obligation to update any forward-looking 
      statement made in this press release to reflect new information, events 
      or circumstances after the date of this release.
    
  
PRAECIS PHARMACEUTICALS INCORPORATED (NASDAQ: PRCS) today
announced that it is presenting interim clinical data from an ongoing
phase 1 trial of its investigational compound, PPI-2458, at the 18th
EORTC-NCI-AACR Symposium on "Molecular Targets and Cancer
Therapeutics" being held from Tuesday, November 7 to Friday, November
10, 2006 at the Prague Congress Centre in Prague, Czech Republic. The
data being presented is entitled "A Phase 1 Dose Escalation Safety &
Tolerance Study of PPI-2458 in Subjects with Non-Hodgkin's Lymphoma or
Solid Tumors" (Abstract #139). Additionally, PRAECIS is presenting
research on the potential role of PPI-2458 in melanoma in a poster
entitled "Effects of PPI-2458, an inhibitor of methionine
aminopeptidase type-2 on growth of melanoma and expression of MITF"
(Abstract #349). The posters may be viewed on the Company's website
(http://www.praecis.com) in the "Investors" section, under
"Presentations."

   PPI-2458 - Interim Clinical Data:

   PPI-2458 is a novel, proprietary, orally available small molecule
that specifically targets methionine aminopeptidase-2 (MetAP-2).
MetAP-2 has previously been demonstrated to be overexpressed in
certain human cancers, including non-Hodgkin's lymphoma (NHL). Study
2458-04-01 is a multi-center, open-label, dose-escalation study
designed to determine the maximum tolerated dose (MTD) of PPI-2458 in
patients with NHL or solid tumors. PPI-2458 is administered to
subjects orally every other day (QOD) for two 28 day cycles. Subjects
are allowed to continue treatment, in the absence of unacceptable
toxicity, until evidence of disease progression. The primary endpoint
of the study is safety, with disease response being evaluated as a
secondary endpoint. Additional secondary endpoints include
pharmacokinetic and pharmacodynamic data.

   Interim results presented include data for 32 subjects that have
been treated across 4 dose cohorts ranging from 2 mg to 8 mg. Data to
date suggests that PPI-2458 is well tolerated at doses up to 8 mg. The
maximum tolerated dose has not been determined and treatment is
currently ongoing in a fifth cohort of subjects receiving a 12 mg
dose.

   Results reported for this trial also include investigation of
pharmacokinetics, pharmacodynamics and tumor assessments. The
pharmacodynamic endpoint is assessed using PRAECIS' proprietary
MetAP-2 assay. Results reported show that MetAP-2 in white blood cells
is substantially inhibited by PPI-2458 in patients across each cohort.
In addition, 7 subjects across the first 4 cohorts have been reported
by the clinical investigators to have stable disease at the end of the
first 2 cycles of treatment.

   "Based on study results to date, PPI-2458 appears to be an agent
with unique and exciting mechanisms (MetAP-2 and
microphthalmia-associated transcription factor (MITF) protein), and as
the Phase 1 study proceeds, there is growing data to support a focused
Phase 2 clinical development plan," stated Dr. J. Paul Eder, Principal
Investigator for the Phase 1 clinical trial and Clinical Director of
Translational Pharmacology at the Dana-Farber Cancer Institute in
Boston, Massachusetts. Dr. Eder continued, "There is indication of
substantial target inhibition in a surrogate tissue and we plan to
determine the effects of PPI-2458 in patient tumor samples in future
cohorts. As the dose has escalated, we have been encouraged by the
increased duration of treatment without clinically significant
toxicity that has been observed for these otherwise treatment
refractory patients."

   "We are pleased to see the encouraging safety and tolerability
data in this Phase 1 trial and we continue to believe that PPI-2458
holds promise for the treatment of a wide range of cancer types,"
stated Kevin F. McLaughlin, President and Chief Executive Officer of
PRAECIS.

   Additional information about the Company's ongoing clinical trial
for PPI-2458 can be accessed on the Internet at
www.clinicaltrials.gov. The Company is currently planning Phase 2
clinical development protocols in oncology.

   PPI-2458 - Preclinical Research in Melanoma:

   One tumor type of particular interest for PPI-2458 treatment is
melanoma. In a poster presented by Gerhard Hannig, Ph.D., Director of
Cellular and Molecular Pharmacology, PRAECIS describes data on
research of the growth inhibitory effects of PPI-2458 on human
melanoma cell lines. These data demonstrate the selective growth
inhibition of melanoma cell lines both in cell-based studies and in
animal models and illustrate a novel mechanism of action for PPI-2458
in melanoma. This inhibition of melanoma growth appears to be directly
linked to MetAP-2 inhibition in these studies.

   In addition, PRAECIS reports that PPI-2458 decreases the cellular
level of microphthalmia-associated transcription factor (MITF)
protein, a master regulator of the melanocyte lineage, in melanoma
cell lines. Recently, MITF has been shown to be a novel melanoma
survival oncogene and this protein may play a potentially important
role in the development and progression of melanoma in humans.
Melanoma patients with metastatic disease and high MITF expression in
tumor tissue tend to have worse overall outcomes than patients with
lower levels of this protein in tumor tissue as described in a recent
publication in the journal Nature. (Nature 436, 2005, 117)

   As part of its current planning for further clinical development
of PPI-2458 in oncology, PRAECIS will consider this preclinical data
on melanoma as well as preclinical and clinical data with respect to
several other cancer types.

   About PRAECIS

   PRAECIS PHARMACEUTICALS INCORPORATED is a biopharmaceutical
company focused on utilizing its proprietary technologies for the
discovery and development of novel compounds that have the potential
to address unmet medical needs or improve existing therapies. PRAECIS
has a novel MetAP-2 inhibitor, PPI-2458, in clinical development for
cancer indications, including non-Hodgkin's lymphoma and solid tumors,
an innovative drug discovery technology, DirectSelect(TM), which
enables the generation and practical use of ultra-large libraries for
the discovery of orally active compounds for drug development, and a
research and development program aimed at identifying one or more
selective S1P-1 agonist compounds to take forward into clinical
testing.

   This news release contains forward-looking statements regarding
the Company's continued development of PPI-2458 for cancer and
autoimmune disorders. These statements are based on the Company's
current beliefs and expectations as to future outcomes and are not
guarantees of such outcomes or of future performance. These statements
are subject to numerous risks, uncertainties and assumptions that
could cause actual events and results to differ from those expected or
anticipated, including, but not limited to, the Company's ability to
continue development of and successfully partner or otherwise obtain
funding for its PPI-2458 program, the Company's ability to continue to
manage operating expenses and to retain key employees, unexpected
expenditures, the timing and content of decisions made by the FDA,
unexpected results in ongoing and future clinical or preclinical
trials, and the need for additional research and testing, including as
a result of unanticipated determinations by regulatory authorities, as
well as the risks set forth from time to time in the Company's filings
with the Securities and Exchange Commission, including but not limited
to the various risks discussed in the Company's Quarterly Report on
Form 10-Q for the quarter ended June 30, 2006. The Company undertakes
no obligation to update any forward-looking statement made in this
press release to reflect new information, events or circumstances
after the date of this release.