More on Suppressed Clinical Trials

We read in the BMJ that a German agency refuses to rule on drug’s benefits until Pfizer discloses all trial results. The drug is reboxetine (Edronax), which readers will recall was recently deemed to be the worst new antidepressant by an Oxford team.


The agency, the IQWiG, are an independent organization, but they were comissioned by the German federal government to report on the benefits of three antidepressants: reboxetine, mirtazapine, and buproprion. Their decision will have major implications in terms of which drugs are available through the German public healthcare system. However, they decided to suspend judgement on reboxetine because the manufacturers, Pfizer, did not provide them with the results of all available trials.

Ten relevant trials for reboxetine that could definitely be included were identified from the literature search in bibliographic databases, publicly accessible drug approval documents, and clinical trial registries. However, 3 of these trials could not be analysed with regard to the antidepressive effect of reboxetine because the publications only contained data on partial populations ...

Furthermore, 6 potentially relevant trials were identified that could not be included because no full publication existed and the manufacturer of reboxetine (Pfizer) refused to provide full information on all trials with reboxetine...

[and] Due to insufficient cooperation from the manufacturer of reboxetine, it remained unclear whether additional unpublished trials exist. It may well be that the identified data represent an even smaller portion of available evidence.

IQWiG have pulled no punches. It's not every day that a healthcare agency puts out a press release headlined "Pfizer conceals study data: Drug manufacturer hinders the best possible treatment of patients with depression". And to be fair to Pfizer, they are hardly behaving worse than their rivals. Essex pharmaceuticals, the manufacturers of mirtazapine, also failed to provide all the data on their drug. GlaxoSmithKline, who make buproprion, did in fact play ball in this case, but this is the very same company who have been widely accused of suppressing data on Seroxat-induced suicides in kids.

So the problem is not unique to Pfizer, or to reboxetine. The problem is with the system which allows drug manufacturers to conduct as many trials as they like and only publish the results they want. The resulting publication bias is damaging to every field of medicine. One solution is for scientific journals to only publish trials that were pre-registered before they started, so that everyone knows about trials before they happen. But maybe this isn't enough. The IQWiG note that the US has a law mandating that clinical trial results must be registered and reported to the FDA, and call for the EU to adopt similar legislation.

Stafford, N. (2009). German agency refuses to rule on drug's benefits until Pfizer discloses all trial results BMJ, 338 (jun22 1) DOI: 10.1136/bmj.b2521