Penwest Pharmaceutical Begins Dosing Phase IIa Clinical Study of Nalbuphine ER

DANBURY, Conn., June 12 /PRNewswire-FirstCall/ -- Penwest Pharmaceuticals Co. announced today that it has begun dosing patients in its Phase IIa study to evaluate the analgesic efficacy of nalbuphine hydrochloride extended release tablet formulation (nalbuphine ER), a product the Company is developing for the treatment of chronic pain.

Nalbuphine ER, designed to be taken as a twice-daily tablet, uses Penwest's TIMERx(R) drug delivery technology. The Company previously conducted multiple Phase I studies on this formulation of nalbuphine ER to establish the pharmacokinetic profile and generate safety data. The Company has also conducted a Phase IIa study of this formulation in which a single dose of nalbuphine ER positively reduced mean pain intensity in a dose- dependent manner over a 12-hour study period when compared to placebo. Nalbuphine is currently available only as an injection medication.

The main objective of this Phase IIa study is to evaluate the analgesic efficacy of Nalbuphine ER in patients with chronic pain secondary to osteoarthritis of the knee or hip. The study will employ a randomized, double-blind, placebo controlled design, with a forced weekly dose escalation and a total dosing period of 21 days. The Company plans to conduct the study at 24 sites in the United States and has a planned enrollment of 216 patients.

The Company expects topline results from this Phase IIa clinical study to be available in the first quarter of 2008.

Jennifer L. Good, Penwest's President and CEO said, "We are very pleased to initiate this Phase IIa trial and are hopeful that this study will generate the information necessary for us to advance nalbuphine ER into the next study which we are targeting to begin in mid-2008. This is an important step in establishing the proof of concept in chronic pain for this product."

Penwest Pharmaceuticals

Penwest is a specialty pharmaceutical company dedicated to bringing to the marketplace innovative products that help improve the lives of patients. The Company's goal is to identify, develop and commercialize prescription products that address unmet medical needs, primarily for diseases of the nervous system. At the core of this strategy, Penwest applies drug delivery technologies, including its own proprietary technologies, to new and existing compounds to enhance their therapeutic profiles. The launch by Endo Pharmaceuticals in mid-2006 of Opana(R) ER (oxymorphone hydrochloride extended-release tablets) formulated with the Company's TIMERx(R) extended release delivery technology demonstrates the execution of this strategy and the value of the Company's TIMERx(R) technology. The Company is currently applying its expertise to a pipeline of potential products that are in various stages of development. The Company intends to commercialize these products independently or through third party alliances.

Forward-Looking Statement

The matters discussed herein contain forward-looking statements that involve risks and uncertainties, which may cause Penwest's actual results in future periods to be materially different from any future performance suggested herein. For this purpose, any statements contained herein that are not statements of historical fact may be deemed to be forward-looking statements. Without limiting the foregoing, the words, "believes," "anticipates," "plans," "expects," "intends," "potential," and similar expressions are intended to identify forward-looking statements. Important factors that could cause results to differ materially include: risks relating to the commercial success of Opana ER and our reliance on Endo for the commercial success of Opana ER; regulatory risks relating to drugs in development, including the timing and outcome of regulatory action; uncertainty of success of collaborations; the timing of clinical trials, including the impact of enrollment rates; whether the results of clinical trials such as the trial referred to above will warrant further clinical trials or warrant submission of an application for regulatory approval of, or the regulatory approval of, the product that is the subject of the trial; actual and potential competition; the need for capital; and other risks as set forth under the caption Risk Factors in Penwest's Quarterly Report on Form 10Q filed with the Securities and Exchange Commission on May 10, 2007, which risk factors are incorporated herein by reference.

The forward-looking statements contained in this press release speak only as of the date of the statement made. Penwest disclaims any intention or obligation to update any forward-looking statements.

TIMERx is a registered trademark of Penwest. All other trademarks referenced herein are the property of their respective owners.

Contacts: Investors: Media: Ben Palleiko/Diane D'Alessandro Laura Walters/Jim Fingeroth Penwest Kekst and Company (203) 796-3700 (212) 521-4800 (877) 736-9378

Penwest Pharmaceuticals Co.

CONTACT: Investors, Ben Palleiko or Diane D'Alessandro, of Penwest,+1-203-796-3700, +1-877-736-9378; or Media, Laura Walters or Jim Fingeroth,of Kekst and Company, +1-212-521-4800