Eisai Will Sell Arena’s Obesity Drug Lorcaserin, Pending FDA Approval

Arena Pharmaceuticals has landed a partner for marketing its weight loss drug, lorcaserin- Japan's Eisai. This makes Arena the first of the three big contenders in the obesity drug race to nab a partner. In the deal, announced in the wee hours of this morning, Arena gets $50 million upfront from Eisai, and stands to make more in milestone payments upon delivering the product for launch time, if lorcaserin gets approved by the FDA. Still more additional payments, which could total up to $1.16 billion, will be tiered based on how well lorcaserin sells. Eisai gets exclusive U.S. rights to market the drug. Arena's stock jumped this morning on the news. You can get the specifics on the deal from Arena's press release. OK. You know it's news when the company provides snazzy photos with the press release. Arena said last month it planned to go it alone with lorcaserin if it couldn't find a partner. But at the time, Leerink Swann analyst Steve Y. Yoo said in a report to investors that "the best source of funding, in our view, would be an upfront payment by a partner for lorcaserin." Well, now Arena's got that cash. What does it mean for the obesity drug race as a whole? Around the interwebs a few folks are wondering whether the terms of the deal still signal some caution on the part of Eisai. My two cents are that in the obesity area, safety may reassure potential partners more than efficacy does. As we wrote back in 2009, lorcaserin disappointed investors as early Phase III trial results came to light, because the compound met some but not all of FDA's numerical weight-loss benchmarks. But lorcaserin's safety profile is very good. Perhaps it's because Arena had the most to prove. Lorcaserin targets the same serotonin receptor as fenfluramine, an ingredient in the infamous Fen-Phen obesity drug combo. Fenfluramine was associated with heart valve damage and a fatal lung disorder- it was pulled from the market in 1997. But lorcaserin is different from fenfluramine- it is more selective for one specific subtype of serotonin receptor and avoids the one that's found in the heart. Arena has had to pay special attention to safety throughout lorcaserin's development and they haven't run into heart valve trouble. Given the history of failures in the weight-loss drug field (Fen-Phen, rimonabant, etc), and given that a weight loss drug will be taken by many people who are otherwise healthy and may not even be clinically obese, it could be that safety will turn out to be king.

Author: Carmen Drahl

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