A new weight-loss drug: lorcaserin

For many people, losing weight is a losing battle and can be very frustrating. On Tuesday 22 December, Arena Pharmaceuticals announced that it would apply to the US Food and Drug Administration (FDA) for approval of a new weight-loss drug, lorcaserin. It has shown promise in clinical trials involving more than 8,500 patients.

In March, the San Diego company said a study of 3,200 patients who took the drug for about a year showed that nearly two thirds lost at least 5% of their weight, an average of 17.9 pounds (8.1 kg), against 7.4 pounds (3.4 kg) in the placebo group.

A second, year-long trial in 4,000 people showed that those taking lorcaserin twice a day lost on average 5.9% of their body weight, against 2.8% on placebo.

These results meet the FDA's targets for obesity drugs: at least 35% of patients on the drug should lose 5% of their body weight, and the share losing weight should be twice that on placebo.

Arena is competing with Vivus and Orexigen to bring the first new prescription weight-loss drug in a decade to market.

Unlike other drugs that act on the brain's appetite centres, lorcaserin works on a receptor also involved in mood. Taken by mouth, it stimulates 5-HT2C receptors in an area of the brain called the hypothalamus, which helps suppress appetite.

In the trials, lorcaserin not only produced weight loss but was well tolerated. Arena said it would be the first safe weight-loss drug on the market, and the drug also showed side benefits for obese people, such as better heart health and lower blood pressure.

At the moment there are only two long-term weight-loss drugs, both on the market for more than ten years. If the FDA approves Arena's drug, it will be the first new weight-management drug to reach the market this decade.

According to the US National Institutes of Health in 2007, nearly 65% of American adults are overweight or obese, and the yearly medical cost of obesity in the US was estimated at about 147 billion dollars in 2008.

Update: lorcaserin was approved in the US in 2012 under the name Belviq, but it was withdrawn in 2020 after a large study found more cancers in people taking it.