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Pain Therapeutics to Present Neuropathic Pain Data at Scientific Meeting

April 27, 2004
Source: Pain Therapeutics, Inc.

Pain Therapeutics, Inc. (Nasdaq: PTIE), a biopharmaceutical company, today announced positive pre-clinical data on a novel treatment for neuropathic pain.  The Company will present its pre-clinical data at the Scientific Meeting of the American and Canadian Pain Societies on Friday, May 7, 2004 in Vancouver, Canada.

Pain Therapeutics' new data opens up the possibility of using its technology to treat neuropathic pain, a chronic condition that affects 2 to 3 million Americans and a new area of focus for the Company.

"We are excited about the possibility of using our novel technology in the area of neuropathic pain," said Remi Barbier, Pain Therapeutics' president and chief executive officer.  "Moderate-to-severe neuropathic pain is typically poorly managed by existing drugs, is often under-diagnosed and affects a large patient population.  We believe a novel drug that provides effective pain relief would bring significant advantages for patients who endure this chronic condition."

"Neuropathic pain represents a substantial unmet medical need," said Nadav Friedmann, Ph.D., MD, chief operating officer of Pain Therapeutics.  "Opioid drugs, such as morphine or oxycodone, are generally viewed as ineffective in relieving chronic pain caused by nerve damage. Our own pre-clinical data confirms this view. However, new data show that ultra-low-dose naltrexone co-administered with an opioid drug greatly attenuates neuropathic pain sensitivity.  These pre-clinical data are encouraging, as they may allow us to develop a novel and effective opioid drug to treat neuropathic pain."

Spending for neuropathic pain is included in the Company's prior financial guidance for 2004.

Technical Poster Synopsis

"Ultra-low-dose Naltrexone Plus Morphine Blocks Thermal Hyperalgesia and Attenuates Mechanical Hypersensitivity In A Neuropathic Pain Model" by Todd W. Vanderah, Ph.D., Assistant Professor of Anesthesiology and Pharmacology, University of Arizona and Lindsay H. Burns, Ph.D., Director of Pre-clinical Research at Pain Therapeutics, Inc.

This poster presents the methods and results of a first investigation of an opium-based drug (morphine) combined with a low-dose opioid antagonist (naltrexone) in a pre-clinical model of neuropathic pain.  In this experiment, a total of 42 rats underwent surgical ligation of spinal nerves (L5 and L6) and were tested for thermal and tactile hyperalgesia (enhanced sensitivity to pain) for 7 days following surgery.  The 42 rats were divided into 6 treatment groups:  placebo, morphine alone, naltrexone alone and three groups receiving various morphine/ultra-low-dose naltrexone combinations.  Placebo or naltrexone alone had no effect on hyperalgesia.  Morphine alone had a partial and transient effect on hyperalgesia.  All groups receiving morphine/ultra- low-dose naltrexone combinations, however, showed significant anti- hyperalgesia compared to morphine alone or placebo for the entire week of testing (p<0.001).  Morphine/ultra-low-dose naltrexone also provided significant anti-hypersensitivity to tactile stimuli (p<0.001).  These pre-clinical data suggest that neuropathic pain and morphine-induced hyperalgesia share a common mechanism of action, i.e., excitatory signaling of opioid receptors.  The prolonged anti-hyperalgesic effects demonstrated here compared to morphine alone suggests an opioid agonist/ultra-low-dose antagonist combination could be an effective treatment for neuropathic pain.

About Neuropathic Pain

Neuropathic pain is a chronic condition caused by nerve injury.  Patients with neuropathic pain typically develop a painful super-sensitivity (hyperalgesia) to touch, heat or other stimuli.  A number of medical conditions can lead to neuropathic pain, including diabetic neuropathy, HIV/AIDS neuropathy, phantom limb pain, spinal cord injury or multiple sclerosis.     At least 1% of the United States population (2-3 million people) suffers from neuropathic pain.  There are few truly effective, well-tolerated drug therapies to treat neuropathic pain.  A variety of classes of drugs, such as opioids, tricyclic antidepressants or anti-epileptic agents (e.g. gabapentin), typically offer partial or transient relief from neuropathic pain.

About Pain Therapeutics, Inc.

We are a biopharmaceutical company that develops novel drugs.  Our drugs target severe chronic pain, such as pain associated with osteoarthritis, low-back pain or irritable bowel syndrome. We have three unique drug candidates in clinical development:  Oxytrex(TM), Remoxy(TM) and PTI-901.  Our two most advanced drugs, Oxytrex and PTI-901, are in Phase III clinical trials.  Remoxy is in Phase I clinical trials in the United Kingdom.  We believe the target market for our three drug candidates exceeds $3 billion per year.  We currently retain commercial rights to our drug candidates.

Pain Therapeutics is presenting two other technical posters at the American Pain Society meeting:

"Oxytrex(TM), A Novel Drug, Effectively Treats Chronic Pain Due to Osteoarthritis," presents the previously announced clinical results of a 360 patient Phase II study;

"Pharmacokinetic Study Supports BID Oral Administration of Oxytrex(TM) in a Chronic Model of Pain," profiles the bioavailability/pharmacokinetics of Oxytrex.

All posters will be made available to the general public on April 27, 2004 on Pain Therapeutics' website,

Note Regarding Forward-Looking Statements:

This press release contains forward-looking statements for purposes of the Private Securities Litigation Reform Act of 1995 (the "Act"). PTI disclaims any intent or obligation to update these forward-looking statements, and claims the protection of the Safe Harbor for forward-looking statements contained in the Act. Examples of such statements include, but are not limited to, the potential use of the Company's technology to develop treatments for neuropathic pain and the size of the potential market for treatments for such pain, and the likelihood that the Company's pre-clinical data will support the development of novel and effective opioid drugs to treat neuropathic pain.  Such statements are based on management's current expectations, but actual results may differ materially due to various factors. Such statements involve risks and uncertainties, including, but not limited to, those risks and uncertainties relating to difficulties or delays in development, testing, regulatory approval, production and marketing of the Company's drug candidates, unexpected adverse side effects or inadequate therapeutic efficacy of the Company's drug candidates that could slow or prevent clinical development, product approval or market acceptance (including the risk that current and past results of clinical trials are not necessarily indicative of future results of clinical trials), the uncertainty of patent protection for the Company's intellectual property or trade secrets, the Company's ability to obtain additional financing if necessary and unanticipated research and development and other costs.  For further information regarding these and other risks related to the Company's business, investors should consult the Company's filings with the Securities and Exchange Commission, including its Form 10-K for the year ended December 31, 2003 and its subsequent periodic filings.

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