[[Updated last paragraph: 9:38 am EDT]] Arena Pharmaceuticals has some good news this morning, although it will take some time to sort out how good. The San Diego-based biotech company said its experimental drug for obesity was able to reach its goals for helping people lose weight, without the side effect of damaging heart valves like the fen-phen drug combination did in the 1990s. That’s an important test for Arena’s drug, lorcaserin, because it’s designed to curb appetite like fen-phen while avoiding similar receptors on heart valves.
The long-awaited results come from an analysis of 3,182 patients in a clinical trial called Bloom, which followed people who took Arena’s lorcaserin pill twice a day or a placebo for two years. The study found that patients lost an average of 5.8 percent of their body weight if they took Arena’s drug, compared with 2.2 percent of their weight in the placebo group.
That finding by itself isn’t enough for Arena to whip up an application to the FDA for approval, because the agency has said in guidelines that a new obesity drug needs to show 5 percentage points more weight loss than patients on a placebo (Arena’s difference was 3.6 percentage points). But there’s another path to clearance, if a drugmaker can show that at least 35 percent of patients on the drug see a 5 percent weight loss, and the loss occurs in twice as many patients as on placebo. Arena cleared that hurdle for FDA approvability, with 47.5 percent patients achieving that amount of weight loss on the drug, compared with 20.3 percent who did that well on placebo.
Since Arena’s drug is made to work like Wyeth’s fen-phen combination—stimulating a receptor in the brain that makes people feel full—regulators have always been extra cautious to make sure it is truly doesn’t hit any related receptors on heart valves that might cause serious side effects. With lorcaserin, researchers saw no drug-related damage to patients’ heart valves after two years of reviewing their echocardiogram images, Arena said. There were some “infrequent” cases of depression, anxiety, and suicidal thinking, although the rates were similar in both the drug and placebo groups, Arena said.
Arena still has two more clinical trials to finish up, Blossom and Bloom-DM, before it intends to turn in its application to the FDA to bring lorcaserin to the market. If it can confirm these findings, it will have a potential big seller. About two-thirds of U.S. adults are overweight or obese, which makes them more likely to get a litany of other conditions like heart disease, diabetes, high blood pressure, and arthritis. The cost of this excess weight is huge to the U.S. healthcare system—a U.S. Surgeon General’s report pegged it at $117 billion in 2000, or about 9 percent of national health care spending. One of the researchers on the study quoted in an Arena press release this morning called the results “medically important weight loss,” although an analyst who follows the company said it didn’t look likely that Arena’s data would allow it to capture a big piece of this market.
“Although the results technically satisfy the FDA requirements for approvability, we consider the weight loss benefits to be underwhelming at best,” said Cory Kasimov, an analyst with JP Morgan, in a note to clients. It’s positive that no major safety problems were seen in the trial, Kasimov said. He expects Arena stock to drop when the market opens this morning, because the news wasn’t as overwhelmingly positive as investors had hoped.
Shares of Arena (NASDAQ: ARNA) fell $1.25, or 28 percent, at the opening bell after the news was released.