Thursday, July 26, 2012

Truvada: pushing the envelope or jumping the gun?

A few days ago, the Food and Drug Administration (FDA) did something that has perhaps not garnered sufficient attention among those working in bioethics. The FDA namely approved the use of the antiretroviral Truvada for use as pre-exposure prophylaxis to reduce risk getting HIV via sexual intercourse. Basically, it is like taking a pill to reduce the risk of acquiring malaria when traveling to a malaria endemic zone. Sort of. What complicates matters is that sex with other human beings is involved rather than contact with mosquitos. And HIV, unlike malaria, is incurable and a stigmatized disease. But perhaps for the moment the real difference is: we have a pretty good idea of what happens when people take malaria prophylaxis, but we do not have a very good idea of what will happen when Truvada starts being prescribed by doctors.

Now you would think that the evidence base must be quite strong before FDA would approve a 'biomedical condom', so to speak. But that is not really the case. There were a couple of randomized controlled trials that indicated a reduction in risk via sexual activity if you took the active ingredients in Truvada (emtricabine/tenofovir) daily: a 42% reduction among men who have sex with men (the iPrEx study) and a 75% reduction among serodiscordant heterosexual couples (the Partners PreP study). But overall, the scientific evidence base for HIV preexposure prophylaxis is currently murky: two other large scale studies in Africa (FEM-PreP and VOICE) recently showed no reduction of risk when using the same drug combination.

But the FDA approved Truvada for use among adults at high HIV risk exposure anyway. Compare: male circumcision as HIV prevention approach was only approved by official agencies in the US after two decades of observational studies and three randomized controlled trials that all indicated (to roughly the same degree) that being circumcised significantly reduces the risk of males acquiring HIV from their female partners. Then again, circumcision is not a pill and cannot be patented. Let me put it plainly: the low scientific bar for Truvada's approval feeds conspiracy theories about pharmaceutical companies and the FDA: the potential global market for 'a pill that protects against HIV' is huge. Is the FDA just facilitating an American company looking to gain early market advantage, while deviating from its stated mission to protect public health?

In any case, it is sobering to see studies being presented at the ongoing International AIDS Conference in Washington -- such as research on attitudes towards preexposure prophylaxis and sexual risk behavior among men who have sex with men -- that ought to have informed regulators before Truvada was approved.


Blogger city said...

thanks for sharing.

1:04 AM  
Blogger Elizabeth Dixon said...

Good points-- thanks for calling attention to the Truvada dilemma!

12:52 PM  

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