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Descovy is one of the medications used for PrEP (Pre-Exposure Prophylaxis) to prevent HIV. However, its on-demand (event-based) use in PrEP, taking it only when needed for sexual activity, is still limited and primarily left to clinical judgment by healthcare providers.

In this blog, we will explain the concept of using Descovy as “on-demand” PrEP, referencing clinical practice reports and guidelines from United States and Europe, as well as our own clinical experience.

Current Status of PrEP

PrEP medications are mainly available in two options: Truvada and Descovy. Truvada has well-established evidence for both daily PrEP (taken every day) and on-demand PrEP (the “2+1+1” regimen, taken only around sexual activity). In contrast, Descovy lacks robust clinical trial data supporting its use in an on-demand regimen, and as a result, it has not yet received FDA approval for this indication in the United States.

However, recent guidelines from the European AIDS Clinical Society (EACS) mention the possibility of using Descovy (F/TAF) for on-demand PrEP in certain situations. The EACS guidelines state that in specific cases, on-demand use of Descovy (F/TAF) can be considered.

EACS Guidelines 2024

Key Points from EACS Guidelines: Descovy for On-Demand PrEP

・The standard “2+1+1” regimen for on-demand PrEP (2 pills taken 2–24 hours before sex, 1 pill 24 hours later, and 1 pill 48 hours later) is strongly recommended based on robust scientific evidence and has been shown to be highly effective for MSM (men who have sex with men).

・Descovy (F/TAF) can be considered for on-demand PrEP. Pharmacokinetic (PK) studies suggest some effectiveness, and it may be suitable for individuals who need to consider kidney function and bone marrow health.

Should Descovy Be Used for On-Demand PrEP?

・MSM may consider it as an option based on EACS guidelines. However, for those at risk via vaginal sex (receptive), Descovy is generally not recommended for on-demand PrEP.

・If considering its use for vaginal intercourse, consultation with an HIV specialist is essential. It should not be used without medical guidance.

Clinical Data on Descovy for On-Demand PrEP from the CHAPS Study

The CHAPS study evaluated the efficacy of various drug regimens and dosing strategies for on-demand PrEP, including Descovy (FTC/TAF). The study included pharmacokinetic (PK) and pharmacodynamic (PD) data from participants in South Africa and Uganda.

Key Findings

・Across all dosing regimens, PrEP with Descovy (FTC/TAF) resulted in higher TFV-DP (Tenofovir Diphosphate) concentrations in foreskin explants and peripheral blood mononuclear cells (PBMCs) compared to Truvada (FTC/TDF).

・The “2+1” dosing regimen (2 pills before sex, 1 pill 24 hours later) resulted in higher TFV-DP levels in foreskin tissue than a single-dose regimen of 2 tablets.

・Taking 2 tablets of either Truvada or Descovy 5 or 21 hours before sex provided foreskin tissue protection against ex vivo HIV challenge.

These findings suggest the potential for on-demand Descovy PrEP, though further clinical trial data is needed to establish its efficacy definitively.

Reference:
Herrera C, Serwanga J, Else L, et al. Dose finding study for on-demand HIV pre-exposure prophylaxis for insertive sex in sub-Saharan Africa: results from the CHAPS open-label randomized controlled trial. EBioMedicine. 2023;93:104648.

On-Demand PrEP with Descovy at PHC

At our clinic, we have prescribed on-demand PrEP with Descovy for individuals based on pharmacokinetic data. Over the past five years, approximately 1,855 individuals have used Descovy for on-demand PrEP, and not a single case of HIV infection has been reported.

While some might question whether this is simply due to low actual risk, a survey on sexual behavior found that about 70% of respondents engaged in sex with multiple partners.

Dr. Shiojiri’s Flexible Approach to On-Demand PrEP

*”On-demand PrEP has often been criticized for its extremely short dosing period of 2-1-1. In the case of daily PrEP, when stopping the medication, users are advised to continue taking it for one week after the last sexual encounter before discontinuing. Similarly, for on-demand PrEP, instead of stopping after just two days of post-sex dosing (2-1-1), some suggest extending the regimen to one full week for increased safety (2-1-1-1-1-1-1).

Rather than adhering to a rigid dosing schedule, why not adopt a more flexible approach and consider extending the medication period slightly for enhanced protection?”*

▶More information about PrEP and its costs