Arena Pharmaceuticals has decided to withdrew its marketing application for the anti-obesity drug Belviq in the European Union, a move which has spooked investors.

The decision is not very surprising given that in January, Arena received a day 180 "list of outstanding issues" from the European Medicines Agency's Committee on Human Medicinal Products stating there were "major objections" needed to be addressed prior to getting a recommendation for approval. These concerns were similar to those expressed by the US Food and Drug Administration in its review of Belviq (lorcaserin) including cardiovascular risks and worries about tumours found in animal studies.

However, while the FDA did give give the green light to Belviq last June, making it the first obesity drug to be approved in 13 years (though it has yet to be launched by partner Eisai), Europe's regulator is less convinced by the data set.

Craig Audet, Arena's head of global regulatory affairs, said that "we do not believe we can resolve the major objections related to the results of non-clinical studies prior to the CHMP's issuance of its final opinion". As such, "we have therefore decided to withdraw the marketing authorisation application and are evaluating the best approach for submitting at a later date".

The only other obesity drug recently approved by the FDA, Vivus' Qsymia (phentermine/topiramate extended-release), has fared no better in Europe. The CHMP issued a negative opinion on the drug last year.

Arena says it has already responded to the Swiss regulators initial assessment regarding Belviq and expects to hear back from Swissmedic in a few months. Eisai has filed the drug in Mexico and will make submissions in Canada and Brazil later this year.

Investors are concerned and Arena shares fell some 15% in after-hours trading.