So Much for Big Pharma's 'Anti-Pot' Pill

An independent U.S. Food and Drug Administration advisory committee determined yesterday that the controversial "anti-pot" pill Rimonabant is unsafe for human consumption in the United States. Sanofi-Aventis' would-be diet aid -- which has been linked to suicidal thoughts, depression and even multiple sclerosis -- counteracts the effects of marijuana and similar naturally occurring chemicals in the body (so-called endocannabinoids), causing users to lose their appetites and, according to the warnings of experts, a host of other unwanted and dangerous side effects.

Rimonabant does not possess a "favorable risk-benefit profile" to warrant U.S. market approval, members of the FDA's Endocrinologic and Metabolic Drug advisory panel determined in a 14-0 vote. Panelists reported that patients prescribed Rimonabant experienced increased incidences of depression, nausea, vomiting, and suicidal tendencies. Adverse neurological symptoms in some patients were also reported.

The expert panel's rejection sent shares of Sanofi stock plummeting and may have worldwide implications. Last summer European regulators gave preliminary approval to the pill, which has now been prescribed to some 100,000 patients under the trade name Acomplia. However, following Wednesday's unanimous decision, representatives of the European Medicines Agency immediately announced that they will begin hearings to consider recalling the drug.

For Sanofi stockholders and analysts, who had predicted that pharmaceutical giant's "anti-pot" pill could one day rake in some $3 billion in annual profits, the news is a disappointing financial setback. But to health experts familiar with the workings of Rimonabant and similar drugs, the FDA panel's decision comes as little surprise and is long overdue.

The dark side of Acomplia

As a weight loss drug, Rimonabant is far from a miracle cure. In controlled studies, patients who ceased taking Rimonabant typically gained their weight back -- implying that the drug may have to be prescribed indefinitely. It's that likelihood, coupled with the drug's reported and potential side effects, that have raised eyebrows among the scientific community.

Because the endocannabinoid system is involved in the regulation of a broad range of primary biological functions -- including appetite, mood regulation, blood pressure, bone density, reproduction, learning capacity, and motor coordination -- some experts are concerned that the long-term use of Rimonabant and/or similar drugs to counteract it could contribute to a host of significant adverse health effects. Animal data appears to substantiate this concern. Newborn mice injected with Rimonabant refuse feeding and often die days after birth. Mice genetically bred to lack certain cannabinoid receptors also suffer from numerous health defects such as cognitive decline, hypoalgesia, decreased locomotor activity and increased mortality compared to healthy controls. Could similar risks await long-term users of Rimonabant?

Dr. Franjo Grotenhermen, director of the Association for Cannabis as Medicine (ACM) in Germany, states, "One of the major functions of the endocannabinoid system is the protection of nerve cells from damage by overactivation of neurotransmitters," Grotenhermen says. "The long-term use of [endocannabinoid] receptor antagonists may impair this neuroprotective effect with an accelerated loss of nerve cells and negative consequences on brain functions such as memory."

Investigators at Amsterdam's Vrije University (the Netherlands) express a similar viewpoint. Writing recently in the journal Multiple Sclerosis, they report of a 46-year-old woman who was diagnosed with the disease after taking Rimonabant daily for seven months. They note that the woman had no prior history of neurological symptoms before taking the drug and that the patient recovered to "near normal" several weeks after discontinuing the medication. "It does not seem implausible that [endocannabinoid] antagonism may cause [central nervous system damage] in susceptible subjects," they concluded.

Among patients administered Rimonabant in clinical trials, many report experiencing adverse effects such as nausea, anxiety and depression. According to published data, more than 15 percent of subjects who try the drug discontinue its use because of intolerable side effects. In addition, at least one study of the drug reported a 2.7-fold increased risk of psychiatric disorders in Acomplia users. Dr. Mitch Earleywine, author of Understanding Marijuana: A New Look at the Scientific Evidence (Oxford University Press, 2002), isn't surprised. "Given what we are now learning about the endocannabinoid system, one would think that any blocking of its receptors, especially long-term, would be an invitation for a host of negative health consequences involving pain, brain function, and mood -- particularly depression," he says.

At yesterday's hearing, FDA experts voiced similar concerns and recommended the agency shelve the drug when it makes its official determination next month. If so, it will be the second time the FDA has refused to grant market approval to Rimonabant, which Sanofi initially tried to sell in the United States as a prescription smoking-cessation agent. Ultimately, in the eyes of the FDA, a healthy body needs all the "pot" it can get.