Potential harms of type 2 diabetes drugs have been ignored, finds BMJ investigation

Drug regulators and manufacturers have been criticised for failing to take enough action in response to research highlighting the potential serious adverse effects of new forms of drugs used to treat type 2 diabetes, known as glucagon-like peptide-1 (GLP-1) based drugs.

A joint investigation by the BMJ and Channel 4’s Dispatches current affairs programme has found that concerns about the drugs, also called incretin therapies, started to emerge in 2007.1 Since then many published reports, regulatory documents, and adverse event databases have highlighted concerns about the safety of these drugs and linked them with an increased risk of pancreatitis, pancreatic cancer, and thyroid cancer.

But a number of drug manufacturers failed to perform certain safety trials, delayed some studies, and did not publish their findings, the investigation found.

The investigation also criticises drug regulators in Europe and the United States for their slow response to the concerns.

The US Food and Drug Administration (FDA) and the European Medicines Agency (EMA) announced only in March this year that they were to review whether the drugs may cause or contribute to the development of pancreatic cancer.2

In the US hundreds of people are suing manufacturers, alleging that the drugs caused pancreatitis and in some cases cancer.

During the investigation the BMJ reviewed thousands of pages of regulatory documents obtained under freedom of information legislation. It found that many studies carried out by drug manufacturers remain unpublished. Independent researchers and lawyers representing patients who have sought to analyse all the evidence have been denied access to the raw data.

Deborah Cohen, the BMJ’s investigations editor, said, “On their own the individual pieces of unpublished evidence may seem inconclusive, but when considered alongside other emerging and longstanding evidence a worrying picture emerges, posing serious questions about the safety of this class of drug.”

The EMA and the FDA confirmed to the BMJ that they had found a “signal” for pancreatic cancer, but this does not mean that there is a causal link.

However, some scientists and manufacturers have defended their actions and the drugs’ safety, arguing that the published evidence against the drugs was weak.

Others have called for all the study data to be made public for independent analysis. Some believe that the drugs should be withdrawn while the potential harms are investigated. They are against the drugs being licensed as a new treatment for obesity.

A team of UK and US academics recently wrote in a head to head debate on this class of drugs in Diabetes Care, “The story is familiar. A new class of antidiabetes agents is rushed to market and widely promoted in the absence of any evidence of long-term beneficial outcomes. Evidence of harm accumulates, but is vigorously discounted.”3

More information on the drugs is expected later this month, when the US National Institutes of Health holds a two day meeting on possible links between diabetes, antidiabetes drugs, and pancreatic cancer.