February 26, 2016
This week, we're reporting the latest research presented at CROI 2016 in Boston. We look at 32-week results from a long-acting injectable antiretroviral therapy study. We also see results about switching to emtricitabine/tenofovir alafenamide (F/TAF), a new coformulation using TAF, the improved version of tenofovir. And we make sense of the initial results about the use of a vaginal ring to reduce HIV transmission. To beat HIV, you have to follow the science!
Taking a long-acting injection of cabotegravir + rilpivirine (Edurant) either every four or eight weeks is safe and well tolerated while also maintaining high viral suppression rates, according to 32-week study results presented at CROI.
Cabotegravir is an investigational integrase inhibitor (a "cousin" of dolutegravir [Tivicay, DTG]) that has shown potential as a long-acting agent. The original LATTE study found that taking oral cabotegravir + rilpivirine daily as maintenance therapy (typically a simplified regimen after viral suppression was achieved on induction therapy) was effective up to 96 weeks.
In the highly anticipated follow-up study known as LATTE-2, after 32 weeks of maintenance therapy, 95% of those receiving injections once every eight weeks maintained an undetectable viral load, compared with 94% of those receiving injections once every four weeks and 91% of those who continued to take a daily oral regimen.
Switching from treatment regimens containing tenofovir/emtricitabine (Truvada, F/TDF) to regimens containing F/TAF maintains undetectable viral loads and improves renal and bone safety, according to 48-week study results presented at CROI 2016.
Although elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide (Genvoya) has already been approved by the U.S. Food and Drug Administration (FDA) for the treatment of HIV, tenofovir alafenamide has not yet been approved for use by itself or in other combinations, and continues to be investigated.
The popular coformulation F/TDF is a part of many recommended first-line treatment regimens and is also approved for pre-exposure prophylaxis (PrEP), However, tenofovir disoproxil fumarate (TDF, Viread) has been associated with kidney and bone toxicities. TAF is a much-discussed improved version of tenofovir that has shown better kidney and bone safety when used in elvitegravir/cobicistat/emtricitabine/tenofovir alafenamide.
In this study, after 48 weeks, 94.3% of those in the F/TAF group maintained an undetectable viral load compared with 93% in the F/TDF group. However, those in the F/TAF group showed significantly better improvements in bone and kidney safety.
Although the overall effectiveness of 27% doesn't seem too exciting, Heather Boerner reports on why there are reasons to be optimistic about a vaginal ring that can prevent HIV in women.
With just a "whisper" of drug, zero side effects and 61% effectiveness when looking at women over 25, we have a strong proof of concept.
Furthermore, we can look back at the iPrEx study as an analogy; that study examined tenofovir/emtricitabine as PrEP and the initial overall effectiveness in 2011 was 44%. But with follow-up studies, particularly the open-label extension (where participants knew what treatment they were getting), effectiveness jumped over 90%. Moreover, tenofovir/emtricitabine is approved for PrEP and we have seen zero infections for those who take it every day.
Therefore, it's reasonable to be optimistic when analyzing the initial vaginal ring results.
Warren Tong is the senior science editor for TheBody.com and TheBodyPRO.com.
Follow Warren on Twitter: @WarrenAtTheBody.
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