NEW YORK (Reuters Health) - The experimental weight-loss drug lorcaserin may spur modest weight loss without the heart risks of some older drugs, a new clinical trial confirms -- though whether the medication will ever reach the market remains up in the air.

Last October, the U.S. Food and Drug Administration (FDA) declined to approve lorcaserin as an obesity treatment, citing research in rats that suggested there could be a cancer risk.

This latest study, reported in the Journal of Clinical Endocrinology and Metabolism, backs up earlier research showing that lorcaserin can shave off some extra pounds.

Of 4,000 obese adults who used the drug for a year, more than 40 percent lost at least five percent of their initial weight -- versus a quarter of those given placebo pills who lost that much.

And the drug facilitated weight loss without raising the risk of heart-valve damage, according to the findings.

Reports of fatal heart-valve problems are what caused the infamous diet drug known as "fen-phen" to be pulled from the market in 1997.

Still, it's unclear whether lorcaserin will ultimately play any role in the battle against obesity, which now affects about one-third of U.S. adults.

The drug's maker, Arena Pharmaceuticals Inc, has said it will conduct further research into the potential cancer risk. Arena's new drug application to the FDA is still considered "open" while the company gathers data to answer the agency's remaining questions about lorcaserin.

Drugmakers have struggled for years to develop weight-loss drugs that are both effective and safe.

Like fen-phen before it, another diet drug -- Meridia -- was pulled from the U.S. market last year after being linked to heart problems in some users.

And lorcaserin is one of three experimental obesity drugs rejected by the FDA in the past year over safety concerns. The other two are Orexigen Therapeutics' Contrave, which combines the antidepressant bupropion with naltrexone, a drug used to fight alcohol and drug addiction; and Vivus Inc's Qnexa, a combination of the appetite suppressant phentermine and the anti-seizure drug topiramate.

The FDA wanted more data on the two drugs' potential heart risks.

Lorcaserin is believed to work by targeting a brain receptor for the chemical serotonin that is associated with hunger.

In a study published last year in the New England Journal of Medicine, researchers at Arena found that of 1,600 obese adults given lorcaserin for a year, 47.5 percent lost at least five percent of their body weight. Of that group, 68 percent kept the weight off for a second year.

That beat the placebo group, in which 20 percent shed that much weight after a year. (Both groups made lifestyle changes along with taking pills.)

In this latest study, the researchers tested two different doses of lorcaserin -- a once-daily 10-milligram dose, in addition to the twice-daily dose used in the earlier studies.

Both were effective, the researchers found. Of patients on the lower daily dose, 40 percent lost at least five percent of their body weight. In the higher-dose group, 47 percent dropped that much weight.

A five-percent weight loss is modest -- equivalent to taking 10 pounds off a 200-pound frame, for instance. But studies show that shedding even that amount can have "beneficial effects" on obesity-related health problems like diabetes, high blood pressure and high cholesterol, noted Arena's vice-president for lorcaserin development Dr. Christen M. Anderson, who worked on the study.

The current findings also strengthen evidence that lorcaserin does not carry the heart-valve risks of some older weight-loss drugs, Anderson told Reuters Health in an email.

Two percent of patients on twice-daily lorcaserin developed heart-valve problems. The percentage was the same in the placebo group.

The most common side effects of the drug were headache, nausea and dizziness.

For now, the drug options are few for obese people who fail to lose weight through diet changes and exercise alone.

The only one approved for long-term use is orlistat (Xenical), which is also available as a lower-dose, over-the-counter version called Alli. But Xenical has its issues as well, including side effects of gas, uncontrolled bowel movements and cases of serious liver problems.

SOURCE: http://bit.ly/rhEft8 Journal of Clinical Endocrinology and Metabolism, online July 27, 2011.