Arena Pharmaceuticals Inc. and partner Eisai Pharmaceuticals Co. Ltd. will have a fine line to walk as they market Belviq lorcaserin for obesity. They want to improve patient compliance, which historically has not been good in obesity, while also preventing the key thing doctors believe could make Belviq a blockbuster - combining it with the generic drug phentermine.

On June 27, FDA approved Belviq in combination with diet and exercise for chronic weight management in adults with a BMI >=30 kg/m2 or in adult patients with a BMI >=27 kg/m2 with at least one co-morbid indication.