Arena Weight Loss Drug Approaches Critical Turning Point Next Month

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to present full data in a prominent journal, or at a medical meeting. It will almost surely heat up negotiations with potential Big Pharma partners. And it will provide part of an application—along with a 7,000-patient trial called Blossom—that the company hopes to put together for the FDA by the end of this year.

Arena has gotten as far as it has because it has passed animal studies showing its drug can specifically stimulate a serotonin receptor in the brain called 5-HT2c, which is associated with sending signals to tell the body it’s full and to stop eating. There are 14 receptors in this family of serotonin receptor subtypes, which are structurally similar, Behan says.

One of those members of the family is 5-HT2b, a receptor found on heart valves that Arena most definitely wants its drug to avoid. “It’s very important to develop a drug that’s specific to the 2c receptor, and that can avoid other receptors,” Behan says.

The Bloom study will provide the most thorough evidence to date on whether lorcaserin works, but data from smaller trials so far have shown encouraging signs. A mid-stage study of 469 patients found that patients lost more weight on progressively higher doses. Patients on the highest dose, a 10 milligram, twice-daily pill, lost 7.9 pounds after 12 weeks, compared with 0.7 pounds for placebo patients. More than 90 percent of patients on the high dose had some degree of weight loss, and about one-third reached the FDA guidelines by losing 5 percent of their body weight, according to research published in Obesity, the peer-reviewed journal of The Obesity Society.

Still, any obesity drug is going to have to pass much more rigorous long-term safety studies before it catches on. Investors have fresh memories of another obesity drug that was shot down by an FDA advisory panel in June 2007. French drugmaker Sanofi-Aventis gave up on the weight loss drug Acomplia shortly after an FDA advisory panel recommended it be kept off the U.S. market because of studies that suggested it was linked with a higher risk of psychiatric side effects, like depression, anxiety, and suicide risk.

One key difference is that Acomplia is designed to hit a different target on cells, the cannabanoid receptors, specifically CB-1, Behan says. “It’s a completely different mechanism,” Behan says.

Even so, many Big Pharma companies, probably remembering the fen-phen debacle quite well, have chosen to sit on the sidelines with obesity drugs, Behan says. Many decided to scrap their drugs in development against the CB-1 receptor after the Acomplia failure. That’s left three small U.S. biotech companies in the hunt with drugs in late-stage development—Arena, San Diego-based Orexigen Therapeutics (NASDAQ: OREX), and Mountain View, CA-based Vivus (NASDAQ: VVUS). NeuroSearch, a Scandinavian company, also has a drug in late-stage development called tesofensine.

Arena doesn’t see itself being hemmed in by competitors so much as coming up with a great drug that can capture a sizable chunk of such a big market opportunity. “This is such a big problem, it’s not like this is some big race to the market. There’s really very few players,” Behan says. By the end of next month, Arena will have a much clearer idea of whether it’s still in the game.

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