April 11, 2006
Public Citizen is asking the U.S. Food and Drug Administration to immediately pull the prescription version of Xenical (orlistat) because the Roche Pharmaceuticals "fat blocker" could contribute to colon cancer.
The drug has been known to cause a significant increase in aberrant crypt foci, which are widely believed to be a precursor to colon cancer.
Last week, the FDA sent an "approvable" letter concerning the over-the-counter (OTC) version of orlistat to GlaxoSmithKline. Despite safety concerns, if GlaxoSmithKline meets the conditions set by the FDA -- conditions that have not been made public -- this would make the drug eligible for final approval for OTC sales.
Public Citizen said its petition is based on findings from the pharmacology review of Roches own data and a recent independent confirmation that orlistat causes ACF in the colon of rats.
There is a large amount of scientific literature that acknowledges the importance of ACF as the earliest identifiable neoplastic colonic lesion and a putative precursor of colon cancer.
The FDAs own 1997 review of orlistat indicated a concern with colonic cell proliferation, and the drug was not initially approved by the FDA because of clinical trials that found a four- to seven-fold increased risk of getting breast cancer while taking orlistat.
In addition to cancer concerns, the group says adverse events for patients taking orlistat include a cluster of gastrointestinal symptoms and a loss of fat-soluble vitamins, including beta-carotene and vitamins A, D, E and K.
Orlistats efficacy has also been called into question because of two recently published clinical trials that showed only a 2.8 percent difference in weight loss after four years between patients taking orlistat and those on placebo.
"The failure to ban the prescription version of this drug or, worse, to make it much more widely available by allowing OTC sales, is a decision that is likely to increase cancer incidence," said Dr. Sidney Wolfe, director of Public Citizens Health Research Group.
Public Citizen is joined in the petition by two professors of pathology at Case Western Reserve School of Medicine, Dr. Theresa Pretlow and Dr. Thomas Pretlow, who are both experts on ACFs link to colorectal cancer. Their work on this topic has been largely funded by the National Cancer Institute, whose director is now acting FDA commissioner.
"The FDA should not allow a drug to remain on the market for the long-term treatment of a non-lethal condition when it combines so little efficacy coupled with a still unresolved potential to cause breast and colon cancer," says the 12-page petition. "[The] FDA is now considering increasing the number of people exposed to the drug by allowing OTC use. There is no scientific justification for this decision."
