Shares in Orexigen Therapeutics have shot up after the company said it has identified "a clear and feasible path to approval" with US regulators for its previously-rejected obesity drug Contrave.

In February, the US Food and Drug Administration issued a complete response letter for Contrave (naltrexone/bupropion) and requested that Orexigen conduct a trial of "sufficient size and duration" to demonstrate that the risk of major adverse cardiovascular events in overweight and obese people treated with Contrave, which is partnered with Takeda, does not adversely affect the drug's benefit-risk profile. Then, in June, Orexigen suspended development of the drug over what it regarded as excessively high barriers to approval put in place by the agency.

However the firm now says following a recent meeting with senior officials in the FDA's Office of New Drugs, it has received written correspondence detailing design requirements for a cardiovascular outcomes trial. Orexigen believes these requirements are now "reasonable and feasible and provide the certainty required to reinitiate development of Contrave".

Importantly, Orexigen adds, the FDA stated that "if the interim analysis meets the specified criteria to exclude an unacceptable increased cardiovascular risk, the drug could be approved". It estimates that the entire study would require less than 10,000 patients and less than two years from study start to the interim analysis.

The company and Takeda plan to initiate the trial in the first half of 2012, with potential approval in 2014. The news has gone down well with analysts and Corey Davis at Jefferies & Co  was quoted by Reuters as saying that "we're still three years and a hundred million dollars away from approval, but we've just gone from a company on the brink of disintegration to something that should yield outsize returns for those willing to be patient".

However, Contrave may have to make up considerable ground on Vivus' Qnexa (phentermine/topiramate) which was also rejected by the FDA a year ago but could be resubmitted as soon as next month. Another rival obesity drug turned down by the agency, Arena Pharmaceuticals/Eisai's lorcaserin, is also likely to be refiled relatively soon.