As expected, regulators in the USA have given the green light to Arena Pharmaceuticals and Eisai's Belviq, making it the first obesity drug to be approved in 13 years.

The US Food and Drug Administration has approved Belviq (lorcaserin) for chronic weight management in adults with a body mass index of 30 or greater, or adults with a BMI of 27 who have at least one weight-related condition such as hypertension, type 2 diabetes or high cholesterol. The thumbs-up was anticipated given that last month the agency's Endocrinologic and Metabolic Drugs Advisory Committee voted 18 to 4, with one abstention, in favour of approval.

Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, said "obesity threatens the overall well-being of patients and is a major public health concern”. She added that Belviq, which works by activating the serotonin 2C receptor in the brain, “provides a treatment option for Americans who are obese or are overweight and have at least one weight-related comorbid condition".

Six post-marketing studies

The approved labelling for Belviq recommends that the drug be discontinued in patients who fail to lose 5% of their body weight after 12 weeks of treatment, "as these patients are unlikely to achieve clinically meaningful weight loss with continued treatment", the FDA added. Arena and Eisai will also be required to conduct six postmarketing studies, including a long-term cardiovascular outcomes trial to assess the effect of Belviq on the risk for major adverse cardiac events such as heart attack and stroke.

The FDA has recommended that Belviq be classified by the US Drug Enforcement Administration as a scheduled drug, ie its potential for abuse needs to be evaluated. The DEA will determine the final scheduling designation and Eisai will then announce a launch date.

Unsurprisingly, Arena shares leapt over 50% following the approval and closed up 28.7% at $11.39. The news has triggered a $20 million payment from Eisai and Arena will bank another $65 million after the DEA designation and launch.

Vivus' Qnexa next?

The last weight loss drug to be approved by the FDA was Roche's Xenical (orlistat) 13 years ago and after the approval of Belviq, more are expected. The FDA will decide on Vivus' Qnexa (phentermine/topiramate) before July 17, while Orexigen Therapeutics is conducting a heart-safety study of its therapy Contrave (bupropion/naltrexone) before refiling.

Arena's good news also led to a rise in shares at Vivus and Orexigen. In an investor note, Cowen & Co analyst Simos Simeonidis  said the Belviq green light "clarifies the agency's willingness and desire to approve compounds for the treatment of obesity, even ones without substantial weight loss and despite the presence of (in many clinicians' views) non-trivial safety concerns".

He believes Qnexa is "clearly a more efficacious agent than Belviq" and claims the anti-obesity space "has the potential to be a large market, with multiple lines of therapy, since most patients will probably either not respond or not achieve the desired weight loss, and will thus end up trying more than one agent". Mr Simeonidis added that "this is a new market, that needs significant physician education and can benefit from more than one company pushing forward their own agent, while at the same time, increasing awareness about all new anti-obesity agents".