Qnexa, hailed as the most promising weight-loss drug by experts for more than a decade has been rejected by the Food and Drug Administration (FDA).

Maker of the experimental diet pill, Vivus Inc. said in a statement on Thursday that the FDA has asked for more study results and information on its possible health risks such as cardiovascular ailments and infertility among women.

Vivus CEO Leland Wilson said that the company is confident about the efficacy and safety profile of the drug demonstrated during the clinical development program and respond to FDA within six weeks.

The California based company is one of the three small drug-makers vying for FDA approval for weight loss pills. Qnexa has a higher chance of getting an approval because of the high level of weight loss cases reported during the study. Patients lost more than 10 percent of their total body mass on an average which is 5 per cent higher than Roche's Xenical, a drug already in the market.

However, Qnexa’s progress hit a rough patch when panelists said the drug was associated with a number of harmful side effects, including depression, heart palpitations, memory losses and even birth defects.

It may be noted that Vivus is the second weight-loss drug rejected by the FDA in the past week. Arena Pharmaceuticals’ Lorcaserin didn’t get FDA approval as tumors were found in rats during tests. The San Diego-based company hasn’t lost hope and working at getting a FDA approval too.

The other competitor Contrave by Orexigen Therapeutics showed 5 to 10 percent weight-loss with modest side effects. The FDA has set strict safety standard this week against weight-loss drugs.

Dr. Tim Garvey of the University of Alabama who conducted two clinical trials of Qnexa said that the drug if gets FDA approval could end the road for many weight-loss drugs in the market for at least a decade.

With U.S. obesity rates reaching alarming heights, doctors and public health officials say new weight-loss therapies are much essential. Nearly35 per cent of American adults are suffering obesity. So far a safe weight-loss drug is yet to be launched in the market.