It was good news for Arena Pharmaceuticals yesterday after an independent data safety monitoring board gave the firm the all clear to continue assessing the efficacy of lorcaserin for the treatment of obesity in Phase III trials.

There had been fears over the drug’s safety as its mode of action is similar to that of fenfluramine, which is found in Wyeth's abandoned diet drug fen-phen - a big seller in the 1990s that was pulled off shelves in 1997 after it was linked to heart valve damage - but the group said the safety review concluded the lorcaserin HCL does not raise the heart risk when compared to placebo.

“This critical milestone assessing month-12 echocardiographic data strongly supports lorcaserin's cardiovascular safety profile [and] we believe that this exposure duration, even under a conservative interpretation of the literature, would have been sufficient to observe a fenfluramine like effect on heart valves if present,” commented Jack Lief, Arena's president and chief executive. He went on to say that the firm remains committed to developing “a robust database for submission to the FDA in our efforts to provide patients a novel, safe and effective obesity treatment”.

First in class
Lorcaserin is the first in a new class of obesity drug candidates targeting the 5-HT2C serotonin receptor, and results from Phase II studies showed its ability to induce “highly statistically-significant, progressive and dose-dependent weight loss over a 12-week period”, the firm notes. Furthermore the drug was generally well tolerated at all doses tested and, if its Phase III assessment proves as successful, it is likely that US approval will be sought in 2009, according to media reports.

The obesity market is forecast to hit $2.5 billion dollars in 2012 and, given that treatment options are still relatively limited, any company offering an effective drug to combat the condition could reap substantial rewards. Unsurprisingly, investors were certainly encouraged by outcome of the safety review, as Arena’s shares closed up 3.6% at $6.54 on the Nasdaq at close of play yesterday.