Arena Pharmaceuticals Inc. said Friday that its fourth-quarter loss narrowed on a big cutback in research and development expenses after the biopharmaceutical company submitted a potential weight-loss drug to regulators for approval.

The San Diego company posted a loss of $29.8 million, or 32 cents per share, in the three months ended Dec. 31. That compares with a loss of $62.5 million, or 84 cents per share, in the final quarter of 2008.

Revenue was flat at $2.7 million.

Analysts polled by Thomson Reuters expected a loss of 31 cents per share on about $3.5 million in revenue.

Arena said research and development expenses sank 60 percent to $21.2 million as the company completed a few late-stage clinical trials that measured the safety and effectiveness of lorcaserin for weight management.

The drugmaker said it studied more than 7,000 patients who were treated for up to two years, and subjects showed significant weight loss in both trials.

Arena applied to the Food and Drug Administration for the drug's approval in December. The FDA has set a target date of Oct. 22 to complete its application review.

Lorcaserin is part of a group of weight-loss drugs that could reach the market around the same time. Vivius Inc. and Orexigen Therapeutics Inc. also are developing potential treatments.

For the full year, Arena lost $153.2 million, or $1.82 per share, on $10.4 million in revenue. In the previous year, the company recorded a loss of $239.5 million, or $3.24 per share, on revenue of $9.8 million.