Regulators in the USA have given the green light to a second weight loss drug in less than a month, namely Vivus' Qsymia.

The US Food and Drug Administration has approved Qsymia (phentermine and topiramate extended-release) for chronic weight management in adults with a body mass index of 30 or greater (obese) or adults with a BMI of 27 or greater (overweight) who have at least one weight-related condition such as hypertension, type 2 diabetes, or high cholesterol. The thumbs-up was expected given that in February, the agency's Endocrinologic and Metabolic Drugs Advisory Committee voted 20-2 that the benefits of the treatment, which was previously known as Qnexa, outweigh the risks.

The recommended daily dose of Qsymia contains 7.5mg of phentermine and 46mg of topiramate extended-release is also available at a higher dose (15mg/92 mg) for select patients. Patients on the former should be evaluated by 12 weeks to determine, based on the amount of weight loss, whether to discontinue Qsymia or increase to the higher dose and if after another 12 weeks a patient does not lose at least 5% of body weight, treatment should be discontinued, the FDA said.

The agency also noted that Qsymia must not be used during pregnancy nor in patients with glaucoma or hyperthyroidism. Its use in patients with recent  or unstable heart disease or stroke is not recommended and regular monitoring of heart rate for all patients is suggested.

Cardiovascular outcomes study needed

The combo has been approved with a risk evaluation and mitigation strategy and Vivus will be required to conduct 10 postmarketing requirements, including a long-term cardiovascular outcomes trial. Janet Woodcock, director of the FDA’s Center for Drug Evaluation and Research, said Qsymia, "used responsibly in combination with a healthy lifestyle, provides another treatment option for chronic weight management".

The thumbs-up for Qsymia comes three weeks after the FDA approved Arena Pharmaceuticals and Eisai's Belviq (lorcaserin), making it the first obesity drug to be approved in 13 years. However, Cowen & Co analyst Simos Simeonidis believes the Vivus drug could be the first to market as Belviq is waiting for final scheduling designation from the US Drug Enforcement Administration.

In an investor note, he went on to say that Qsymia has a significant advantage over Belviq, "given its considerably better efficacy", even though "safety will be an issue for some physicians (notably, the fear of birth defects among women who become pregnant". However, Belviq's "carcinogenicity and valvulopathy signals, no matter how faint, may cast a bigger shadow over this compound and lead more prescribers and patients towards Qsymia, at least as their initial choice", Mr Simeomidis argues.

Difficult launch?

He went on to say that the US launch of Qsymia by Vivus is "a difficult one to pull off successfully, or at least much more difficult than if a large pharma were doing it. The analyst adds that this could change if "a big pharma with the stomach/risk appetite (no pun intended) to dive into the obesity space comes in and acquires Vivus, an acquisition which could come at a non-trivial premium to current levels".

News of the approval went down well with a number of groups, including the American Society of Bariatric Physicians, whose executive director Laurie Traetow said that "clearly, the tide is turning in our efforts to address the rising obesity epidemic in our country". She added that specialists are excited about the FDA "adding another tool to the obesity treatment toolbox, which for so many years had been virtually barren in the pharmacotherapy area".