Almost one-third of the participants in a 12-week clinical trial who took 20 mg a day of Arena Pharmaceuticals' experimental diet drug lorcaserin hydrochloride (formerly ADP356) achieved a 5 percent or greater weight loss, researchers reported June 12th at the annual scientific meeting of the American Diabetes Association.

Dr. Steven Smith, lead researcher in the Phase 2b study that enrolled 469 obese patients at 40 locations across the United States, told the meeting "lorcaserin demonstrated excellent weight loss in this study" and also produced improvements in fasting glucose and most lipid measures.

Lorcaserin is a selective agonist of the 5-HT2C serotonin receptors, concentrated in the hypothalamus, an area of the brain known to play an important role in regulating food intake and metabolism. Arena believes lorcaserin may have potential to regulate satiety -- the feeling of fullness.

"Based on the strength of these data, we are currently in discussions with the FDA about initiating a Phase 3 trial of lorcaserin in obese patients later this year," said Jack Lief, Arena Pharmaceuticals President and CEO.

In the trial, patients with body mass indexes ranging from 29 to 46 were randomized into four groups to evaluate the safety and efficacy of daily 10 mg, 15 mg and 20 mg (10 mg dosed twice daily) doses of lorcaserin compared to placebo for 12 weeks.

Results were significantly better for the patients taking the 20 mg dose of lorcaserin.

Patients completing the 12-week treatment period with lorcaserin achieved a highly statistically significant mean weight loss of 7.9 pounds at the 20mg dose (almost double the weight loss of those taking the daily dose of 10 mg) compared to 0.7 pounds for the placebo group.

Some 31 percent of the patients on the 20 mg dose completing the twelve week treatment period achieved a 5% or greater weight loss from baseline compared to 2% in the placebo group.

Treatment with lorcaserin was also associated with dose-dependent and statistically significant improvements in BMI, waist circumference, hip circumference, cholesterol and fasting blood sugar, the researchers reported. Positive, dose-dependent trends on LDL-cholesterol and triglycerides were also observed.

Lorcaserin was generally well tolerated at all doses investigated in the trial, the researchers reported. Adverse events occurring in greater than 5 percent of participants in any of the dosed groups were headache, nausea, dizziness, vomiting, dry mouth, nasopharyngitis, fatigue and urinary tract infection.

An assessment of baseline and Day 85 echocardiograms indicated no apparent lorcaserin effect on heart valves or pulmonary artery pressure.