The US Food and Drug Administration (FDA) has approved Arena Pharmaceuticals and Eisai's Belviq, the first new drug approved to treat obesity in the US in 13 years.
Belviq (lorcaserin HCl), formerly known as Lorqess, activates the 5-HT2C receptor in the brain and is thought to work by increasing feelings of satiety when consuming food, leading patients to feel fuller after a smaller amount of food.
In trials the effects of the drug were relatively modest, helping a significantly greater number of overweight patients achieve a reduction in body weight of around 5 per cent after a year's treatment compared to placebo.
The drug is not to be used on its own, however, with the FDA approving Belviq as an add-on to a reduced calorie diet and increased exercise for chronic weight management.
This indication is for adults with a body mass index of 30 or greater, or those with a BMI of at least 27 and weight-related complications such as high cholesterol, high blood pressure or diabetes.
Switzerland-based Arena will manufacture Belviq at its facility in Zofingen, while Eisai will distribute the drug in the US with a launch expected next year. Belviq is also under review by the European Medicines Agency (EMA).
Pharmacotherapy for obesity has had a contentious history, and the FDA has set the bar high for new treatments. A major scandal erupted in the late 1990s, for example, when two drugs were withdrawn from the market on evidence they may have caused heart valve problems in patients.
The two withdrawn drugs - fenfluramine and dexfenfluramine - were thought to cause the side effect because they activated the 5-HT2B receptor, so the FDA has paid close attention to the potential for this in its appraisal of Belviq.
"Heart valve function was assessed by echocardiography in nearly 8,000 patients in the Belviq development programme," said the agency.
"There was no statistically significant difference in the development of FDA-defined valve abnormalities between Belviq and placebo-treated patients," it added, although Arena has committed to comprehensive post-marketing surveillance commitments to study Belviq's long-term safety.
Winning through to market is a major achievement for Arena and Eisai, given the number of obesity therapies which have failed at the last hurdle. There is currently only one approved prescription drug for obesity on the market - Roche's Xenical (orlistat) - and this has enjoyed limited take-up because of gastrointestinal side effects.
In addition to fenfluramine and dexfenfluramine, Sanofi's Acomplia (rimonabant) and Abbott Laboratories' Meridia (sibutramine) were both removed from the market in 2009 and 2010, respectively, after being link to neuropsychiatric side effects.
And Belviq itself was rejected in 2010 after animal studies suggested a possible link to tumour formation, although subsequent studies showed no such effect in humans.
The drug's approval could herald the start of a new era for pharmacotherapy however, with Vivus awaiting the FDA's verdict on its Qnexa (phentermine and topiramate) candidate after a positive recommendation from an agency advisory committee in February. The FDA later extended its review date following a request for more data.
Also in the offing is Orexigen's Contrave (bupropion/naltrexone), although this was turned down last year by the FDA. The agency has asked the company to carry out an additional clinical trial.
What is clear is that additional options for treating obesity are desperately required. More than one-third of US adults are obese, with medical costs associated with obesity estimated at nearly $15bn in 2008.
Faced with this escalating bill, the US federal government implemented a programme in 2010 which set a target of reducing this to 15 per cent on average across the country.
"Obesity threatens the overall wellbeing of patients and is a major public health concern," commented Janet Woodcock, director of the FDA's Center for Drug Evaluation and Research (CDER).
"The approval of [Belviq], used responsibly in combination with a healthy diet and lifestyle, provides a treatment option for Americans who are obese or are overweight and have at least one weight-related comorbid condition," she added.