The race to bring a new obesity treatment to market is heating up as Arena Pharmaceuticals announced a marketing and supply agreement with Eisai worth up to $1.3 billion in payments for its experimental obesity drug lorcaserin and its competitor Orexigen announced promising results from a late-stage clinical trial for its experimental drug Contrave the same week.

Despite the much talked about obesity epidemic and analyst estimates of a multi-billion dollar market for drugs to treat the condition, the hunt for treatments has been plagued with safety concerns, market withdrawals, and clinical failures. The market research firm Datamonitor referred to obesity in a 2009 report as the “$11 billion market that never was” as it forecast drug sales in the category to reach just $560 million in 2018, far less that the $12.2 billion market opportunity it says is there. The problem, says Datamonitor, is that “current approaches just aren’t good enough to capitalize on this opportunity.”

Under the terms of the agreement, Eisai will give San Diego-based Arena an upfront payment of $50 million and, upon regulatory approval and the delivery of a supply of the product for its launch, up to an additional $90 million in milestone payments.

Arena will sell lorcaserin to Eisai for a purchase price starting at 31.5 percent of Eisai's annual net product sales, and the purchase price will increase on a tiered basis to as high as 36.5 percent on the portion of annual net product sales exceeding $750 million. Arena is also eligible to receive nearly $1.2 billion in one-time purchase price adjustment payments based on annual sales levels of lorcaserin and up to an additional $70 million in regulatory and development milestone payments.

Lorcaserin is the most advanced candidate in Arena’s pipeline. It is a member of a new class of selective serotonin 2C receptor agonists. The serotonin 2C receptor is expressed in the brain, including the hypothalamus, an area involved in the control of appetite and metabolism. Stimulation of this receptor, the company said, is strongly associated with feeding behavior and satiety. The FDA is expected to act on Arena’s application to begin marketing lorcaserin by October 22.

Separately, Arena’s La Jolla, California-based neighbor Orexigen Therapeutics released promising results for its late-stage obesity drug Contrave. Contrave combines the antidepressant Wellbutrin with a sustained-release version of an opioid blocker used to treat alcohol, drug, and other addictions.

The company said a late-stage trial of Contrave in patients with type 2 diabetes showed that after 56 weeks of treatment, overweight or obese patients with the disease lost significantly more weight and achieved greater improvement in glycemic control than those treated with placebo.

The study found more than twice as many patients lost at least 5 percent of their body weight on Contrave versus placebo on an intent-to-treat basis, researchers said during a presentation at the 70th Scientific Sessions of the American Diabetes Association. Contrave-treated patients experienced clinically significant reductions in A1C. Average baseline A1C, the standard test for monitoring glycemic control, of approximately 8.0 percent was reduced by 0.6 percent for Contrave compared to 0.1 percent for placebo. A1C provides a measure of how much glucose is in the blood over an extended period.

This translated to over 44 percent of Contrave patients reaching the American Diabetes Association treatment target for A1C of less than 7 percent, the company said. That compares to 26 percent of placebo patients reached the same threshold.

Orexigen’s Contrave will be the third up before the FDA in the most recent string of obesity drugs. Vivus’ treatment Qnexa is expected to get a thumbs up or down from the agency by July 15, well before Arena’s October date or Orexigen’s January date.