HIV and ID Observations

Most of the pivotal trials of pre-exposure prophylaxis (PrEP) have used daily therapy.

The lone exception is the IPERGAY study. Men at high risk for acquiring HIV took two tablets of tenofovir DF/emtricitabine (TDF/FTC, Truvada) before sex, and one tablet the next 2 days.

The strategy was highly effective in preventing HIV acquisition, and intermittent PrEP is endorsed as an option in France, where the study was conducted.

(About that name — it stands for Intervention Préventive de l’Exposition aux Risques avec et pour les Gays. I have it on good word from the lead investigator that they can say it in French without smiling.)

The main concern some have raised about the IPERGAY results is that participants had relatively frequent exposures (a median of 4/month), enough so that sufficient tissue levels of TDF/FTC could be maintained.

But what about even less frequent high risk exposures, say a few of times a year? Daily PrEP for these patients seems like overkill, and intermittent PrEP may not work. Might they benefit from a different prevention strategy?

A group in Toronto just published a novel approach to these patients — instead of giving them PrEP, they are recommending on-demand postexposure prophylaxis (PEP).

(In the paper, they call it “PEP-in-pocket,” or “PIP,” but I don’t think we can tolerate another one of these single syllable abbreviations in HIV prevention that begins with “P.”)

From 2013–2017, two clinical sites identified relatively low-risk individuals from those who were initially referred for PrEP.

The preventive strategy consisted of prescribing a 28-day supply of TDF/FTC plus dolutegravir, with instructions to start it as soon as possible if the patient had what they deemed to be an exposure that might transmit HIV.

Thirty such people were identified. In the follow-up period, 4 of the 30 initiated PEP on their own, all doing so within 10 hours of the exposure. Each reported good adherence to their treatment, and were closely followed-up.

All who started preventive medications were seen in clinic within a week for clinical evaluation and blood work. There were no HIV seroconversions in 21.8 person-years of follow-up.

Of course, the small size of the study, and its retrospective, non-comparative design hardly are sufficient to incorporate this strategy into guidelines.

Nonetheless, there are several advantages to this on-demand PEP strategy. These include avoiding daily exposure to medications, lower drug costs, reducing emergency room visits, and still providing some preventive intervention, just in case. Individuals who start on-demand PEP multiple times can be transitioned to PrEP, which is what happened to 4 of the patients in this study.

I look forward to hearing more about this approach — and I’d be saying that even if the senior author weren’t a graduate of our ID fellowship program!

(Nice work, Isaac.)