The Washington Post recently ran a story about a potential use of Enbrel, an anti-inflammatory drug, to reduce the risk of Alzheimer’s disease. The article reports that a non-randomized, non-interventional, retrospective, non-published, non-peer-reviewed, internal review of insurance claims was correlated with a reduced risk for Alzheimer’s disease. This hypothesis was dismissed after internal consideration, on the basis of scientific (and probably business) considerations.
You can probably guess my take on it, given the way I describe it, but for people who are unfamiliar with the hierarchy of medical evidence, this kind of data mining represents pretty much the lowest, most unreliable form of medical evidence there is. If you were, for some reason, looking for even lower-level evidence than this, you would need to go into the case study literature, but even that would at least be peer-reviewed and published for public scrutiny. If you need further convincing, Derek Lowe has already published a fairly substantial debunking of why this was not a missed Alzheimer’s opportunity on his blog.
Many people, even after being convinced that Pfizer probably made the right call in not pursuing a clinical trial of Enbrel in Alzheimer’s, still think that the evidence should have been made public.
There’s been lots of opinions thrown around on the subject, but there’s one point that people keep missing, and it relates to a paper I wrote in the British Medical Journal (also the final chapter of my doctoral thesis). Low-level evidence that causes suspicion of activity of a drug, when it is not swiftly followed up with confirmatory testing, can create something that we call “Clinical Agnosticism.”
Not all evidence is sufficient to guide clinical practice. But in the absence of a decisive clinical trial, well-intentioned physicians or patients who have exhausted approved treatment options may turn to off-label prescription of approved drugs in indications that have not received regulatory sanction. This occurs where there is a suggestion of activity from exploratory trials, or in this case, extremely poor quality retrospective correlational data.
Pfizer should not be expected to publish every spurious correlation that can be derived from any data set. In fact, doing so would only create Clinical Agnosticism, and potentially encourage worse care for patients.