OREXIGEN Therapeutics Announces Sustained-Release Formulation of Zonisamide Shows Improved Tolerability When Compared to Immediate Release Formulation

Orexigen(TM) is evaluating zonisamide SR as a novel component in EMPATIC(TM) Phase IIb obesity trial

SAN DIEGO, June 07, 2007 /PRNewswire-FirstCall/ -- Orexigen(TM) Therapeutics, Inc. , a biopharmaceutical company focused on the treatment of central nervous system disorders with an initial focus on obesity, today announced results from a Phase I trial evaluating safety and pharmacokinetics of its novel, proprietary, sustained-release (SR) formulation of zonisamide. In the study, the SR formulation of zonisamide achieved a significant reduction in the incidence of spontaneous adverse events compared to an immediate release (IR), legacy formulation. Zonisamide SR is a key component in the Company's obesity product candidate Empatic(TM) and is presently being evaluated in a large, Phase IIb multi-center study.

The Phase I trial was a single-center, randomized, double-blind, single- dose, crossover study in 36 healthy, normal volunteers and compared legacy zonisamide IR to an equivalent dose of zonisamide SR. Adverse events were reported by 45.7% of subjects receiving the IR formulation versus only 8.5% receiving Orexigen's SR formulation. The most frequent overall adverse event was headache; six subjects receiving zonisamide IR reported headache, while none of those receiving zonisamide SR experienced headaches. As hypothesized by the Company when initiating the SR program, a relationship between adverse events and the peak free drug concentration (Cmax) of zonisamide was demonstrated. Across all subjects, zonisamide SR exhibited a lower Cmax than the legacy IR formulation, while retaining a similar overall exposure or area under the curve.

Results from a Phase II proof-of-concept trial evaluating Empatic formulated with zonisamide IR in combination with bupropion SR for the treatment of obesity were previously reported at the North American Association for the Study of Obesity (NAASO) in October 2006. Empatic was associated with significant weight reduction through 48 weeks of treatment but also early discontinuations due to adverse events in approximately 37% of study participants. Zonisamide appeared to be the principal contributing factor, as a similar rate of discontinuations was evident among subjects receiving zonisamide IR therapy alone. Orexigen, in partnership with PharmaDirections, Inc. developed the proprietary SR formulation of zonisamide with the objective of improving its overall tolerability.

"We are excited that our novel, sustained release formulation of zonisamide was significantly better tolerated than the existing generic IR formulation. This is an important consideration in conditions such as obesity that often require longer-term maintenance therapy. Based on these results, we are eagerly awaiting the outcome of our ongoing 24 week Phase IIb multi-center study of Empatic, which incorporates our proprietary formulation of zonisamide SR," said Gary Tollefson, M.D., Ph.D., Orexigen's President and CEO.

About Orexigen(TM) Therapeutics

Orexigen Therapeutics, Inc. is a biopharmaceutical company focused on the development of pharmaceutical product candidates for the treatment of central nervous system disorders, with an initial focus on obesity. Orexigen's lead combination product candidates targeted for obesity are Contrave(TM), which is in Phase III clinical trials, and Empatic(TM) (formerly Excalia(TM)), which is in a Phase IIb clinical trial. Both product candidates take advantage of the Company's understanding of how the brain appears to regulate appetite and energy expenditure, as well as the mechanisms that come into play to limit weight loss over time. Each product candidate is designed to act on a specific group of neurons in the central nervous system with the goal of achieving appetite suppression and sustained weight loss. Further information about the Company can be found at http://www.orexigen.com.

Forward-Looking Statements

Orexigen cautions you that statements included in this press release that are not a description of historical facts are forward-looking statements. The inclusion of forward-looking statements should not be regarded as a representation by Orexigen that any of its plans will be achieved. For example, statements regarding the potential progress and results of clinical trials and the use of funds to support such trials may be forward looking statements. Actual results may differ materially from those set forth in this release due to the risks and uncertainties inherent in Orexigen's business, including, without limitation: Orexigen's clinical trials may not proceed in the timeframes or in the manner Orexigen expects or at all; the results of earlier clinical trials may not be predictive of future results; the scientific theories relating to the central nervous system on which Orexigen has based its development programs may not result in product candidates with sufficient efficacy or safety to obtain regulatory approval or commercial success; Orexigen and its licensors may not be able to obtain, maintain and successfully enforce adequate patent and other intellectual property protection of its product candidates; and other risks detailed in Orexigen's public filings with the Securities and Exchange Commission. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement and Orexigen undertakes no obligation to revise or update this news release to reflect events or circumstances after the date hereof. This caution is made under the safe harbor provisions of Section 21E of the Private Securities Litigation Reform Act of 1995.

     CONTACTS:

     Graham Cooper         Media:                        Investors:

     Orexigen CFO          Stephen Gendel                Jason Spark

     (858) 436-8600        (212) 918-4650                (619) 849-6005

CONTACT: Graham Cooper, Orexigen CFO, +1-858-436-8600; or Media, StephenGendel, +1-212-918-4650, or Investors, Jason Spark, +1-619-849-6005, bothfor Orexigen Therapeutics, Inc.

Web site: http://www.orexigen.com/

Ticker Symbol: (NASDAQ-NMS:OREX)

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Posted: June 2007

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