Arena Pharmaceuticals Holds Back Data

Arena Pharmaceuticals (ARNA) provided very little useful information Tuesday night about the Belviq-phentermine weight-loss combination. Key heart safety and efficacy data were not disclosed in the company’s press release announcing results from a short, proof-of-concept study.

Obese patients offered the “Bel-phen” combo for 12 weeks did not report higher rates of headache, dizziness, nausea, fatigue, dry mouth, diarrhea, vomiting, insomnia or anxiety compared to patients treated with Belviq alone, Arena said.

Arena said nothing about cardiovascular adverse events in the Bel-phen study. Belviq is a chemical cousin of fenfluramine, the old weight-loss drug pulled off the market because it caused damage to heart valves when combined with phentermine. Belviq was designed to avoid the heart-safety problems of fenfluramine, although not everyone is convinced. Doctors still cite the potential for safety risks as a reason not to prescribe Belviq to their patients, which has contributed to the drug’s dismal sales to date.

Theoretically, the combination of Belviq and phentermine may help patients lose more weight than Belviq alone, but the added risk of causing heart damage, if any, hasn’t been quantified. The c urrent combination study is too small and too short to answer the heart-safety question.

Weight-loss results from the Bel-phen combination study are also being kept under wraps, although additional details from the study are expected to be presented at the Obesity Society scientific meeting early next month. The study compares two different dosing regimens of Bel-phen against Belviq alone. The combination is not being compared to phentermine alone.

The experience of one weight-loss doctor using Bel-phen on his own was disclosed in September.

Belviq is marketed in the U.S. by the Japanese drug company Eisai. Financial results, including Belviq sales, for the September quarter will be announced Thursday. Belviq sales have totaled $18.3 million in the first half of the year, with Arena recording $6 million of that amount under its revenue-sharing plan with Eisai.

Orexigen Therapeutics (OREX) and Takeda received FDA approval to sell Contrave, a competing weight-loss pill, in September.

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