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Pain Therapeutics Completes Patient Enrollment of Women's Phase III Study in Irritable Bowel Syndrome

- Results On-Track to be Announced by Year-end -

SOUTH SAN FRANCISCO, Calif., June 21 /PRNewswire-FirstCall/ -- Pain Therapeutics, Inc. (Nasdaq: PTIE), a biopharmaceutical company, today announced that it has completed patient enrollment for a Phase III study with PTI-901. PTI-901 represents a new mechanism of action to treat women or men with chronic Irritable Bowel Syndrome (IBS).

This randomized, double-blind, multi-center study enrolled over 600 women diagnosed with IBS by a gastroenterologist according to the Rome II Criteria. This U.S. study is designed to compare the safety and efficacy of PTI-901 against placebo during a three-month treatment period. Women with constipation, diarrhea or alternating symptoms of IBS were enrolled in this study. The Company expects to announce top-line results of this study by year-end.

"The medical community uses the term 'irritable bowel syndrome' to describe a group of chronic, painful symptoms," said Nadav Friedmann, Ph.D., MD, chief operating and medical officer at Pain Therapeutics. "These symptoms often include abdominal pain, bloating, distension of the abdomen, constipation or diarrhea. This chronic condition is believed to cause serious discomfort for over 25 million Americans."

Pain Therapeutics is also conducting a Phase III study in 600 men with IBS. This study is similarly designed to the Phase III study with PTI-901 in women. The men's study continues to enroll patients at a slower rate than the women's study. We believe the difference in enrollment rates occurs because IBS affects more women than men.

About PTI-901

PTI-901 (a single, daily, 0.5 mg oral dose of naltrexone HCl) is the first in a new class of drugs designed to restore the balance of opioid activity in the gut. It is believed that an imbalance of opioid activity in the gut contributes to the symptoms that comprise IBS. Such an imbalance may be triggered by emotional stress, metabolic disorders or intrinsic release of opioids from neurons in the gut. By restoring this balance, PTI-901 may relieve abdominal pain and other symptoms frequently observed in patients with IBS. Pain Therapeutics holds exclusive, worldwide commercial rights to a family of issued patents and patent applications directed to the long-term treatment of IBS patients with proprietary opioid antagonists, such as PTI-901.

In a previously reported 50 patient pilot study with PTI-901, patients with IBS reported a 76% response rate to PTI-901. This response rate was observed in men and women and occurred without drug-related safety issues.

About IBS

IBS is a chronic, painful abdominal disorder that leads to major changes in bowel habits. IBS causes some patients to have constipation, diarrhea or in some cases both. The cause of IBS is not known, and as yet there is no cure. People with chronic IBS may be unable to attend social events, hold a job, or travel away from home. Over 10 percent of the U.S. population suffers from IBS.

Upcoming Clinical Announcements

We continue to expect to make the following clinical announcements in the second half of 2005:

    Drug Candidate Patient Population               Expected Announcement
    Oxytrex(TM)    Osteoarthritic Pain - Phase III  Report top-line results
    PTI-901        Irritable Bowel Syndrome - P.III Report top-line results
                                                     in women
    Remoxy         Severe Chronic Pain - P.III      Report top-line results
    Remoxy         Severe Chronic Pain - P.III      Initiate second Phase III

About Pain Therapeutics, Inc.

We are a biopharmaceutical company that develops novel drugs. Our drug candidates target severe chronic pain, such as pain associated with low-back pain, osteoarthritis or Irritable Bowel Syndrome. We have three unique drug candidates in clinical development: Oxytrex, Remoxy(TM) and PTI-901, all of which are in Phase III clinical trials. We believe the target market for our three drug candidates exceeds $3 billion per year. We own commercial rights to our drug candidates.

For more information please visit our website at www.paintrials.com.

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, any statements relating to the timing, scope or expected outcome of the Company's clinical development of PTI-901, the potential benefits of PTI-901 and the Company's drug candidates and the size of the potential market for the Company's products, including PTI-901. 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 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.

SOURCE Pain Therapeutics, Inc.
06/21/2005
CONTACT: Christi Waarich, Senior Manager of Investor Relations of Pain Therapeutics, Inc., +1-650-825-3324, or cwaarich@paintrials.com; or media,
Kathy Nugent, Ph.D., of Burns McClellan, +1-212-213-0006, for Pain Therapeutics
Web site: http://www.paintrials.com/

"Safe Harbor" Statement under the Private Securities Litigation Reform Act of 1995: Statements in this press release regarding Pain Therapeutics, Inc.'s business which are not historical facts are "forward-looking statements" that involve risks and uncertainties. For a discussion of such risks and uncertainties, which could cause actual results to differ from those contained in the forward-looking statements, see "Risk Factors" in the Company's Annual Report or Form 10-K for the most recently ended fiscal year.