Is there any evidence-based guidance on the onset of HIV protection when switching from daily oral PrEP (Descovy or Truvada) to oral cabotegravir (CAB) lead-in prior to initiating long-acting injectable cabotegravir?
From the available data, oral cabotegravir was primarily studied as a pharmacokinetic and tolerability lead-in, not as a validated standalone oral PrEP regimen. In HPTN 083/084, participants either continued oral TDF/FTC during the lead-in or transitioned directly into injections, and the trials were not designed to establish oral CAB efficacy for HIV prevention on its own.
Pharmacokinetically, cabotegravir reaches measurable plasma concentrations within days, with a long half-life and high protein binding, but protective drug levels and time-to-protection thresholds for oral CAB have not been clearly defined, unlike daily oral TDF/FTC where onset of protection is better characterized by tissue penetration data.
Despite this, I have seen clinicians advising patients that protection begins ~3 days after switching from oral TDF/FTC or TAF/FTC to oral cabotegravir.
Would appreciate if anyone could shed some light on this, particularly from a guideline or real-world practice perspective.
Thank you!
Mo Nakhal, PharmD, AAHIVP
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Mohammad Nakhal
Mississauga ON
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