Almost a year after getting approval, Arena Pharmaceuticals' weight loss drug Belviq will be launched this week in the USA by partner Eisai.

At the end of June 2012, the US Food and Drug Administration approved Belviq (lorcaserin) for chronic weight management in adults with a body mass index of 30 or greater, or adults with a BMI of 27 who have at least one weight-related condition such as hypertension, type 2 diabetes or high cholesterol. However, the agency said at the time that Belviq had to be classified by the US Drug Enforcement Administration as a scheduled drug, ie its potential for abuse needed to be evaluated.

This held up a launch but last month the DEA placed Belviq into Schedule IV of the Controlled Substances Act, which means the treatment has a low potential for abuse. In connection with the US launch, Arena, which manufactures Belviq at its facility in Switzerland and sells it to Eisai, will pocket $65 million in milestones and is also eligible to receive $1.19 billion in purchase price adjustment and other payments based on annual sales.

Belviq, a twice-daily treatment, will compete against Vivus' Qsymia (phentermine/topiramate), approved later but launched in September. However Qsymia, which is also classed as Schedule IV, has had disappointing sales, hit by reimbursement issues and the fact that it could only be sold by mail order, although that situation is changing.