Orexigen Therapeutics (OREX) announces continued rapid enrollment into the Light Study

SAN DIEGO, Sept. 5, 2012 /PRNewswire/ — Orexigen® Therapeutics, Inc. (Nasdaq: OREX) today announced an update to the projected timeframe for enrollment of patients in the Light Study, the cardiovascular outcomes clinical trial evaluating Contrave® (naltrexone SR/ bupropion SR). Enrollment into the study has continued without abatement at a rate faster than originally expected, with more than 4,500 patients enrolled as of August 31. Orexigen now expects to close enrollment to new patients in the fourth quarter of 2012.

The primary endpoint of the Light Study is the time to occurrence of major adverse cardiovascular events (MACE) during randomized treatment for Contrave compared to placebo. After at least 87 MACE have been adjudicated, the study’s independent Data Monitoring Committee will conduct an interim analysis. If the interim analysis excludes a doubling of risk of MACE in patients receiving Contrave compared to placebo, Orexigen plans to resubmit the Contrave New Drug Application (NDA) to the United States Food and Drug Administration (FDA) for approval. The exclusion of a doubling of risk of MACE was established as the threshold for approvability of Contrave during discussions with the FDA prior to the start of the Light Study.

“By successfully expediting patient enrollment into the Light Study, we are executing on our promise to shareholders to do what we can to pull forward the time to the interim analysis,” said Michael Narachi, CEO of Orexigen.

“The other key information needed to determine the timing of the interim analysis is the rate of MACE in the study, which is still too early to know,” Narachi continued. “Importantly, because the demographics of the patient population entering the study are in line with our targets for age, gender, race, smoking status, prevalence of cardiovascular disease and other co-morbidities, we remain confident that we will have the requisite number of events needed to conduct the interim analysis in 2013. We would expect to update investors with a more precise estimate of the timing of the interim analysis after we have received sufficient information about the rate of events from the Data Monitoring Committee.”

As a result of the successful acceleration of enrollment, some expenses associated with the Light Study will shift from 2013 into 2012. Accelerating enrollment does not result in a change to the Company’s guidance that current cash, cash equivalents and marketable securities will last through the anticipated timing of the resubmission of the Contrave NDA.

About Orexigen Therapeutics

Orexigen Therapeutics, Inc. is a biopharmaceutical company focused on the treatment of obesity. The Company’s lead product candidate is Contrave, which has completed Phase III clinical trials and for which a New Drug Application has been submitted and reviewed by the FDA. The Company has also reached agreement with the FDA on a Special Protocol Assessment (SPA) for the Light Study, the Contrave cardiovascular outcomes trial. The Company’s other product candidate, Empatic™, has completed Phase II clinical trials. Further information about the Company can be found at 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. Words such as “believes,” “anticipates,” “plans,” “expects,” “indicates,” “will,” “intends,” “potential,” “suggests,” “assuming,” “designed” and similar expressions are intended to identify forward-looking statements. These statements are based on the Company’s current beliefs and expectations. These forward-looking statements include statements regarding the timing of patient enrollment and MACE events in the Light Study; the ability to enroll the targeted patient population; the ability to activate sites and conduct the Light Study; the potential for, and timing of, the accrual and adjudication of MACE events and the potential resubmission of the Contrave NDA; the safety and effectiveness of Contrave; the potential for, and timing of, approval for Contrave and that the Company’s cash, cash equivalents and marketable securities will last through the anticipated timing of the resubmission of the Contrave NDA. The inclusion of forward-looking statements should not be regarded as a representation by Orexigen that any of its plans will be achieved. Actual results may differ from those set forth in this release due to the risk and uncertainties inherent in the Orexigen business, including, without limitation: the Special Protocol Assessment (SPA) is not binding on the FDA if public health concerns unrecognized at the time the SPA agreement was entered into become evident, other new scientific concerns regarding product safety or efficacy arise, or if Orexigen fails to comply with the agreed upon trial protocol; Orexigen’s ability to conduct the Light Study and the progress and timing thereof, including risks associated with recruiting and enrolling patients in the Light Study; Orexigen’s ability to demonstrate in the Light Study that the risk of MACE in overweight and obese subjects treated with Contrave does not adversely affect the product candidate’s benefit-risk profile; the potential that earlier clinical trials may not be predictive of future results in the Light Study; the potential for the FDA to not approve Contrave even after the resubmission with the MACE event data; the potential for the Light Study to cost more than what is projected; the potential for early termination of the collaboration agreement between Orexigen and Takeda; the costs and time required to complete additional clinical, non-clinical or other requirements prior to any resubmission of an NDA; the therapeutic and commercial value of Contrave; Orexigen’s ability to maintain sufficient capital; and other risks described in the Company’s 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, and Orexigen undertakes no obligation to revise or update this news release to reflect events or circumstances after the date hereof. Further information regarding these and other risks is included under the heading “Risk Factors” in Orexigen’s Quarterly Report on Form 10-Q filed with the Securities and Exchange Commission August 9, 2012 and which is available from the SEC’s website (www.sec.gov) and on Orexigen’s website (www.orexigen.com) under the heading “Investor Relations.” All forward-looking statements are qualified in their entirety by this cautionary statement. This caution is made under the safe harbor provisions of Section 21E of the Private Securities Litigation Reform Act of 1995.

Orexigen Contact:

Media Contact:

McDavid Stilwell

Denise Powell

VP, Corporate Communications and Business Development

WCG

(858) 875-8629

(510) 703-9491