Pain Therapeutics Provides Oxytrex(TM) Update

SOUTH SAN FRANCISCO, Calif., Oct. 28 /PRNewswire-FirstCall/ -- Pain Therapeutics, Inc. , a biopharmaceutical company, today provided an update on its progress with its Phase III clinical program for Oxytrex. Oxytrex (oral oxycodone + ultra-low-dose naltrexone) is an investigational drug in late-stage clinical development for the treatment of moderate-to-severe chronic pain.

"We remain on-track to announce Phase III study results with Oxytrex by early December," said Remi Barbier, Pain Therapeutics' president and chief executive officer. "The Phase III data remains blinded and we are clearly excited to begin clinical and statistical analysis of this data. We also believe it's important to articulate a clear set of expectations about the pending results."

What Is Our Phase III Clinical Strategy For Oxytrex?

Pain Therapeutics is developing Oxytrex to treat patients with moderate-to-severe chronic pain. The FDA has indicated that Oxytrex is eligible for broad-label approval if its safety and efficacy are demonstrated in two pivotal studies in chronic pain populations.

What Was The Design Of The First Phase III Study For Oxytrex?

The first Phase III study enrolled over 700 patients with severe low-back pain. This randomized, double-blind, multi-center U.S. study was designed to compare the safety and efficacy of a variable dose of Oxytrex versus oxycodone or placebo. Patient enrollment was completed in September 2004 and Phase III results were announced in March 2005.

What Were Clinical Results Of The First Phase III Study?

Among other benefits, Oxytrex patients reported a significant reduction in physical dependence and withdrawal effects (p<0.01) in the first 24 hours following cessation of prolonged, high-dose therapy compared to patients on oxycodone, as measured on the Short Opioid Withdrawal Scale.

What Is The Design Of The Second Phase III Study For Oxytrex?

The second Phase III study was initiated in the U.S. in March 2004 and is fully enrolled. Approximately 750 patients with moderate-to-severe osteoarthritic pain were enrolled in this randomized, double-blind, multi-center study. This second Phase III study is designed to compare the safety and efficacy of a fixed dose of Oxytrex versus oxycodone or placebo.

What Is The Dose For The Second Phase III Study?

Patients receive a fixed daily dose of drug (20 mg or 40mg) or matching placebo for 12 weeks. Following a washout period, patients are randomized to one of six arms, each arm enrolling 150 patients except as noted: Oxytrex 10mg BID; Oxytrex 20mg BID; Oxytrex 10mg QID; oxycodone 10mg QID; ultra-low-dose naltrexone alone (N=75); or placebo (N=75).

What Is The Primary Endpoint For The Second Phase III Study?

The final analysis plan for this study was submitted to the FDA in early October. In this study, the prospectively defined primary endpoint is reduction of physical dependence and withdrawal effects in the first 24 hours following cessation therapy, as measured on the Short Opioid Withdrawal Scale, between patients receiving Oxytrex 20mg BID and oxycodone 10mg QID (i.e., patients in both of these arms received a total dose of 40mg of drug per day).

Why Is Physical Dependence The Primary Endpoint?

Physical dependence is an expected effect of prolonged opioid therapy. Physicians and patients often associate physical dependence with addiction and avoid opioid painkillers altogether. Patients who appropriately use opioid painkillers may find it inescapable to discontinue drug use. Based on highly encouraging Phase III study results and a unique mechanism of action, we believe Oxytrex may be developed as a novel painkiller with minimal physical dependence, among other benefits.

What Is The Secondary Endpoint For The Second Phase III Study?

One of the principle secondary endpoints in this study is non-inferior analgesic efficacy of Oxytrex 20mg BID versus oxycodone 10mg QID. That is, patients in both of these arms received a total dose of 40mg of drug per day and must report at least equal analgesia.

Are Study Results Still Blinded?

This study remains blinded. All clinical data will remain blinded until the last patient's data is entered into the database and the database is locked. Study results will be announced after the data is unblinded and results are analyzed according to the pre-defined statistical analysis plan.

What Are Next Steps Assuming Positive Phase III Results?

Following the release of data, we plan to discuss NDA requirements for Oxytrex with the FDA. We believe this meeting may occur in Q1 2006. In 2006, we would also continue to enroll patients in an on-going open-label safety study, commence pre-commercialization activities and conduct other needed activities.

What About Other Clinical Announcements?

In addition to announcing Phase III results with Oxytrex this quarter, Pain Therapeutics remains on-track to announce in December results of a Phase III study with PTI-901 in 600 women with Irritable Bowel Syndrome.

About Oxytrex

Oxytrex is a unique oral painkiller that preferentially inhibits an excitatory effect of opioid receptors. This excitatory effect is believed to counteract analgesia (pain relief) and cause tolerance. Its inhibition enhances pain relief and minimizes opioid tolerance. We believe Oxytrex represents the first new mechanism of action by an opiate drug since morphine was discovered over 100 years ago.

We are developing Oxytrex to treat moderate-to-severe chronic pain, such as osteoarthritic pain or low-back pain. We believe Oxytrex could be an effective substitute for oxycodone, a leading opioid painkiller, with U.S. sales of nearly $2 billion for the 12-months ending August 2005, according to IMS Health data. We own all commercial rights to Oxytrex.

About Pain Therapeutics, Inc.

Pain Therapeutics is an emerging biopharmaceutical company that develops novel drugs. Our investigational drug candidates target different types of chronic pain, such as low-back pain, pain due to osteoarthritis or irritable bowel syndrome. Pain Therapeutics has three unique drugs in Phase III clinical development: Remoxy(TM), Oxytrex and PTI-901.

For more information please visit our 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, any statements relating to the timing and scope of the Company's clinical development of Oxytrex, the Company's anticipated discussions with the FDA, the potential benefits of Oxytrex and the Company's drug candidates and the size of the potential market of the Company's products, including Oxytrex. 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 Oxytrex and the Company's drug candidates, unexpected adverse side effects or inadequate therapeutic efficacy of the Company's drug candidates, including Oxytrex, 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.

Pain Therapeutics, Inc.

CONTACT: Christi Waarich, Senior Manager of Investor Relations of PainTherapeutics, Inc., +1-650-825-3324, or; or media,Carney Duntsch of Burns McClellan, +1-212-213-0006, for Pain Therapeutics,Inc.

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