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UPDATE: Research linking two diabetes drugs to cancer spawns debate

Kathleen Blanchard's picture

Glucagon-like-peptide-1 (GLP-1)-derived diabetes medications (exenatide and sitagliptin) have been in the news for a "possible" link to cancer, which has generated some debate between drug manufacturers and researchers. Professor Michael A. Nauck, (Diabetes Center Bad Lauterberg, Germany) says" that there is no evidence that these therapies [Byetta and Januvia] increase cancer risk.

Research conducted by Robert Elashoff of the University of California at Los Angeles, which included Dr. Peter Butler, director of the Larry L. Hillblom Islet Research Center at UCLA found a link between the drugs and cancer when they explored FDA drug databases, but so far, there is no “hard” evidence that Byetta or other GLP-1 drugs cause cancer, leading drug companies to defend the medications.

Diabetes drug safety concerning

Butler says cancer risk from the two diabetes drugs is a concern, based on mouse studies. He also warned more studies are needed to prove or disprove the drugs might raise the risk of pancreatic and thyroid cancer or diabetes.

Dr. Nauck writes the research finding Elashoff and colleagues poses "...a serious issue of whether or not incretin-based medications potentially increase the risk for pancreatitis, pancreatic cancer, and thyroid cancer.

Since the firm exclusion of such a risk would mean analysing large databases with sufficient numbers of patients and events… he suggests the possible link between the two diabetes drugs and cancer “needs to be carefully and critically scrutinised."

In other words, it will take a long time to show if the type 2 diabetes drugs, Januvia and Byetta, increase the risk of cancer.

EmaxHealth was asked by one of the drug company’s PR firm, to change our title of the UCLA research piece, which didn't originally include the word "possibility" or "possible" link between the diabetes drugs and pancreatitis and cancer.

The firm stated the title reflected an "inaccuracy" per an e-mail communication. Amylin Pharmaceuticals, Inc. and Lilly USA, LLC manufacture Byetta and Merck is the manufacturer of Januvia.

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Dr. Nauck feels the UCLA evidence that the diabetes drugs might possibly cause cancer is inconclusive, and says," duct proliferation in response to DPP-4 inhibitor treatment has not been confirmed in other animal models.

Going from pancreatitis to pancreatic cancer (without experimental evidence) is highly speculative and not directly supported by data" - which is true because that data doesn't exist per "gold standard" research.

Nauck, who has been a lead researcher for incretin-based diabetes therapies, says one case of pancreatitis was detected out of 8 rats receiving sitagliptin treatment, which could be a "chance" finding.

He also argues the link between the diabetes drugs and thyroid cancer by saying " Thyroid C-cell abnormalities (including C-cell carcinoma) have been observed in rodents, in whom there are more C-cells, which express GLP-1 receptors and respond with increased calcitonin secretion. Human C-cells do not express similar levels of GLP-1 receptors, do not respond with increased cAMP levels and stimulated calcitonin secretion. Medullary (C-cell-) carcinomas represent a small minority of thyroid cancer. "

Dr. Nauck adds that drawing any conclusion about Januvia or Byetta causing cancer, based on animal studies of models prone to develop the disease, "may well be erroneous" .

The debate, which was the focus at the European Association for the Study of Diabetes (EASD) conference in Lisbon last week, has been ongoing. In January 2010, FDA official, Curtis Rosenbraugh, MD, PhD wrote a memo suggesting Byetta and other GLP-1diabetes drugs might have safety risks. The FDA delayed approving Byetta, but never required more studies.

In a commentary, published by BMJ, Dr. Mark Struthers, a General Practioner in Bedfordshire, UK wrote,” With very little background investigation, thalidomide was promoted to the public, far and wide, as a 'wonder drug', all the time "stressing that the drug was completely non-poisonous ... safe ... astonishingly safe ... non-toxic ... fully harmless and even that it could be taken "in higher dosages than recommended without any danger."

He ends his commentary saying, “ I think it was Mark Twain who said, "History doesn't repeat itself, but it rhymes."

The comment was in response to the current study from Michael Elashoff and colleagues, which can be viewed here.
Consumers might consider Vioxx, the NSAID manufactured by Merck, which was withdrawn from the market in 2004. In a court hearing, internal e-mails were released, showing the drug company intentionally sought to “neutralize” physicians alarmed about the cardiovascular deaths seen from the drug.

Whether or not Januvia and Byetta can up the risk of pancreatitis and pancreatic or thyroid cancer remains to be seen. Dr. Peter Butler and Dr. Nauck discussed the issue last week at the EASD. The newest study notes the possibility that a link between the type 2 diabetes drugs and cancer exists.