Arena Pharmaceuticals Inc. (ARNA) on Friday said its obesity drug candidate Lorcaserin met primary efficacy and safety endpoints in the second late-stage trial, dubbed BLOSSOM (Behavioral modification and LOrcaserin Second Study for Obesity Management).
The BLOSSOM trial evaluated 10 mg and 20 mg daily doses (10 mg dosed once or twice daily) of Lorcaserin versus placebo over a one-year treatment period in obese patients with or without co-morbid conditions and overweight patients with at least one co-morbid condition. About 4,000 patients were enrolled in the BLOSSOM trial with an average body mass index of 35.9 and baseline weight of 220 pounds.
According to the trial results, 63.2% of the patients treated with 10 mg of lorcaserin dosed twice daily, who completed the 52-week trial, lost at least 5% of their body weight, while 35.1% of patients lost at least 10% of their body weight. In the placebo arm, 34.9% and 16.1% of the patients who completed the trial achieved at least 5% and 10% weight loss, respectively.
Average weight loss in the Lorcaserin group (10 mg dosed twice daily) was 17.0 pounds or 7.9% of body weight, compared to 8.7 pounds, or 3.9% of body weight in the placebo arm.
Arena said that 53.1% of patients treated with 10 mg of Lorcaserin dosed once daily lost at least 5% of their body weight while 26.3% lost at least 10% of their body weight at the end of 52 weeks. The average weight loss in the lorcaserin 10 mg once daily group was 14.3 pounds, or 6.5%.
The top quartile of Lorcaserin patients lost 36% more body weight than the top quartile of placebo patients, the company said.
According to Intent-to-Treat Last Observation Carried Forward analysis, which includes all patients who were randomized and returned for at least one weight measurement, patients treated with 10 mg of lorcaserin once or twice daily achieved highly statistically significant categorical and average weight loss after 12 months.
As per the ITT-LOCF analysis, 47.2% of patients treated with 10 mg of Lorcaserin dosed twice daily lost at least 5% of their body weight compared to 25.0% for placebo. Also, 22.6% treated with 10 mg of lorcaserin dosed twice daily lost at least 10% of their body weight compared to 9.7% for placebo.
The ITT-LOCF analysis also revealed that in the lorcaserin 10 mg once daily treatment, 40.2% of patients lost at least 5% of their body weight and 17.4% of patients lost at least 10% of their body weight.
Patients who took lorcaserin 10 mg twice daily achieved an average weight loss of 5.9% of their body weight, compared to 2.8% for placebo. Thus, the placebo-adjusted weight loss works out to 3.1%. Similarly, patients who took Lorcaserin 10 mg once daily achieved an average weight loss of 4.8% of their body weight.
According to the FDA approval standards for diet drugs, the proportion of patients who lose greater than or equal to 5% of baseline body weight in the treatment group should be at least 35% or the difference in average weight loss between the investigational drug and placebo-treated groups should be at least 5%. It is not necessary that a drug should satisfy both the benchmarks.
Lorcaserin was well tolerated and was not associated with depression or suicidal ideation. Treatment with Lorcaserin also resulted in significant improvements as compared to placebo in multiple secondary endpoints associated with cardiovascular risk, Arena said.
In March, Arena stock got battered despite the company reporting positive top-line results from the BLOOM study. The trial results reported in March revealed that 47.5% of patients treated with Lorcaserin lost greater than or equal to 5% of their body weight from baseline compared to 20.3% in the placebo group.
Average weight loss in the Lorcaserin group was 5.8% of body weight, or 12.7 pounds, compared to 2.2% of body weight, or 4.7 pounds. Thus, the placebo-adjusted weight loss worked out to 3.6%.
Though it is not necessary that a drug should satisfy both the benchmarks, investors were disappointed with the inferior placebo-adjusted weight loss percentage and drove the company's stock price down by 28% to $3.23 on March 30.
According to the National Center for Health Statistics, 34% of American adults are obese and 32.7% are overweight. A person with a body mass index or BMI of 25-29.9 is said to be overweight, while an obese person will have a BMI of 30 or more. It is claimed that obesity is responsible for over 300,000 deaths a year in the U.S. In such a scenario, obesity drugs are poised to have a multi-billion dollar market. However, the likelihood of potential side-effects has made pharma giants cautious about developing such drugs.
Biopharmaceutical company Orexigen Therapeutics, Inc. (OREX) said in July that its obesity drug Contrave or bupropion SR/naltrexone SR met co-primary goals in all the three remaining Phase 3 trials, as well as exceeded the U.S. Food Drug Administration efficacy benchmark for clinically significant weight loss. The company intends to file an NDA in the first half of 2010.
Vivus Inc. (VVUS), which is developing a prescription diet drug, said earlier that in a phase III trial evaluating its investigational drug Qnexa in non-diabetic, obese patients, blood sugar levels were lower in the patients treated with Qnexa, while the patients in the placebo group had a significant increase in their HbA1c levels.
Since Lorcaserin works a lot like the banned Fen-phen, the drug's safety profile has been keenly watched. Fen-phen, a combination drug of Phentermine and Fenfluramine, and a related drug Redux marketed by Wyeth (WYE) were withdrawn from the U.S. market in September 1997 after the drugs were found to be associated with a serious heart condition known as valvular regurgitation, or leaky heart valves.
Arena said today that the BLOSSOM trial confirms the results previously reported for the BLOOM (Behavioral modification and Lorcaserin for Overweight and Obesity Management) trial. The integrated echocardiographic data set from BLOSSOM and BLOOM trials rules out a risk of valvulopathy in lorcaserin patients according to criteria requested by the FDA, the company added.
The company intends to present detailed data from both the Bloom and Blossom trials at the 27th Annual Scientific Meeting of The Obesity Society, scheduled for October 24-28 in Washington, D.C.
Arena plans to submit a New Drug Application, or NDA, for lorcaserin to the FDA in December.
ARNA closed Thursday's regular trade at $4.91, up $0.09 or 1.87%, on 6.19 million shares. In the extended trade, the stock surged $1.76 or 35.85%, and was trading at $6.67.
For comments and feedback contact: editorial@rttnews.com
April 24, 2026 15:15 ET Economics news flow was relatively light this week even as the conflict in the Middle East continued, raising concerns for policymakers. In the U.S., spending data, initial jobless claims and pending home sales were the highlights. Business confidence in the biggest euro area economy was in focus in Europe. Inflation data from Japan gained attention in Asia.