Arena and Eisai release data on obesity drug candidate lorcaserin to be used in CRL response

USA-based Arena Pharmaceuticals (Nasdaq: ARNA) and Japanese partner Eisai (TYO: 4523) announced the completion of a clinical study that measured lorcaserin concentrations in human cerebrospinal fluid (CSF) and plasma and related data analyses. Eisai acquired rights to the obesity drug candidate in an up to $1.37 billion deal last year (The Pharma Letter July 1, 2010).

The new data might provide useful ammunition in persuading the US Food and Drug Administration, which has not approved a weight-loss drug since 1999, and which issued a complete response letter regarding lorcaserin, citing a number of reasons, particularly regarding tumors found in animal studies (TPL October 25, 2010). As well as turning down lorcaserin, the FDA has also declined to approve Vivus' Qnexa (phentermine/topiramate) and Orexigen Therapeutics' Contrave (sustained-release naltrexone/bupropion), partnered with Takeda.

The study was conducted to provide additional data that may be informative for determining the human relevance of the observation of brain astrocytoma in male rats, the companies stated. Using the results of this study and other preclinical and clinical studies, Arena estimates that the mean exposure of the human brain to lorcaserin at the clinically tested dose (10mg dosed twice daily (BID)) is approximately 1.7 times the exposure in the human plasma. In contrast, the measured exposure of the male rat brain to lorcaserin at the dose at which no brain astrocytoma was observed (10mg/kg/day) is around 24 times the exposure in the rat plasma.