HIV and ID Observations

From The Lancet comes this important study of tenofovir pre-exposure prophylaxis for injection drug users (IDUs):

In this randomised, double-blind, placebo-controlled trial, we enrolled volunteers from 17 drug-treatment
clinics in Bangkok, Thailand … We randomly assigned [2413] participants to either tenofovir or placebo … 50 became infected during follow-up: 17 in the tenofovir group and 33 in the placebo group, indicating a 48·9% reduction in HIV incidence (95% CI 9·6–72·2; p=0·01).

As with other PrEP studies, better adherence = more protection. There was more nausea and vomiting in the tenofovir treatment group, but no significant differences in serious adverse events. No one who acquired HIV in the TDF arm developed HIV resistance.

So now what? In parallel with publication of the study — which was done in part by CDC investigators — CDC has issued an update on their “Interim Guidance” on PrEP, now focusing on IDUs. Key aspects of the recommendation:

• Consider it only in those at “very high risk” for HIV via IDU, meaning: sharing of injection equipment, injecting at least daily, and use of cocaine or methamphetamine.
• Critical to exclude HIV infection before starting PrEP, monitor regularly for incident HIV, side effects, pregnancy, etc.
• Use tenofovir/emtricitabine (TDF/FTC), even though the Thai study used tenofovir.

The rationale behind this last recommendation, even though the cost of TDF/FTC is higher?

TDF/FTC contains the same dose of TDF (300 mg) proven effective for IDUs, 2) TDF/FTC showed no additional toxicities compared with TDF alone in PrEP trials that have provided both regimens, 3) IDUs also are at risk for sexual HIV acquisition for which TDF/FTC is indicated, and 4) TDF/FTC has an approved label indication for PrEP to prevent sexual HIV acquisition in the United States.

Makes sense to me.

(What also makes sense is that they’re abbreviating it “TDF/FTC”, rather than “FTC-TDF”, as in iPrEx — that was driving me crazy.)

Both the study and the Guidance are welcome additions to the HIV prevention effort. Still, I suspect PrEP in this population will prove particularly difficult to implement, as adherence to medical interventions — for example, HIV treatment — is notoriously challenging among those with active injection drug use.