Interesting expose of the BiDil saga in this month’s Scientific American (Jonathan Kahn ‘Race in a Bottle’ Sci Am Aug 2007; 26 - 31) – I was vaguely aware of this but didn’t know the details. BiDil is a drug that was approved in 2005 by the FDA for heart failure – but in African-Americans only.
The logic case was that African-Americans have different gene frequencies to white Americans and so race-specific drugs represent sensible genetic targeting. In principle this might just about be true for small tightly knit kinships but 'African-American' is a huge category. Black Americans do seem to suffer a higher rate of stroke than Whites at any given blood pressure level, suggesting perhaps some relevant cardiovascular genetics, but the facts of this particular case turn out to be very different.
Firstly, and I hadn’t realised this, BiDil is just a combination
pill of two very common drugs for heart disease: hydrallazine and nitrate.
Nothing special there which is likely to be gene-specific.
Secondly the effect of BiDil on African-Americans was noted
only in post-hoc sub-group analysis of a much larger trial. This is well known
to be an extremely dangerous thing to do. A trial had shown no overall survival
benefit from BiDil but if you split the subjects by ethnic group there was a
small survival advantage in the 49 Black patients. This then led to a trial
which only recruited self identified African-Americans. This second
trial demonstrated a large (43%) survival advantage in the treatment group
versus the placebo group. Because the trial had only been conducted in Black
patients, the FDA only licensed BiDil for Black patients.
As Kahn points out, this is barmy – no drug has ever been
licensed for whites only because the trial only included white patients. This
is policy making ‘on the hoof’ – I feel some sympathy for the FDA
asked to rule on a complex issue they didn’t have time to think through
properly. We’ve all been there, albeit
on a smaller scale.
Take home message – beware retrospective sub-group
analysis! and don't make policy on the hoof.