Vivus has been given the go-ahead in the US to market its weight-loss treatment Qsymia (formerly known as Qnexa) and says it plans to launch the product in the fourth quarter.
Qsymia (phentermine/topiramate) is the second weight-loss drug to be approved by the FDA in a month. Towards the end of June the agency gave a green light to Arena Pharmaceutical/Eisai's Belviq (lorcaserin), ending a drought of 13 years in the US.
Like Belviq, Qsymia has been approved for use in patients who are overweight or obese, and have at least one other weight-related condition such as hypertension, diabetes or high cholesterol.
The two drugs have an almost clear run at the pharmacological weight-loss category as most other drug treatments have been withdrawn from the market in recent years, with notable examples including Sanofi's Acomplia (rimonabant) and Abbott Laboratories' Meridia (sibutramine).
There is currently only one approved prescription drug for obesity on the market - Roche's lipase inhibitor Xenical (orlistat) - and use of this drug has been limited by gastrointestinal side effects. Analysts have suggested that an effective, safe weight-loss medicine could achieve blockbuster sales.
In trials, patients who took Vivus' drug alongside dietary changes and exercise were able to lose 6.7 to 8.9 per cent of their body weight, with around two thirds of patients successfully losing 5 per cent over the course of a year's treatment.
In Belviq's trials, 38 to 47 per cent of patients achieved a 5 per cent reduction, although no direct comparison between the drugs has been carried out and observers have suggested that success in the marketplace will depend as much on marketing muscle as it will on efficacy and safety.
Vivus' president Peter Tam said the company may be able to bring Qsymia to market ahead of Belviq, as its active ingredients have already been classified by the Drug Enforcement Administration (DEA), while a decision has yet to be made on lorcaserin.
Both drugs also have safety issues to consider. The review of Qsymia was extended by three months to allow the FDA time to evaluate a Risk Evaluation and Mitigation Strategy (REMS), as the drug should not be used in pregnancy or by patients with heart disease, glaucoma or hyperthyroidism.
Meanwhile, both Qsymia and Belviq's developers are committed to carrying out post-marketing studies to gauge long-term cardiovascular safety.
According to the Centers for Disease Control and Prevention (CDC), more than one-third of adults in the US are obese, with medical costs associated with obesity estimated at nearly $15bn in 2008.