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Estimating the impact of PrEP regimens containing long-acting injectable cabotegravir or daily oral tenofovir/emtricitabine among men who have sex with men in the United States: mathematical modelling for HPTN 083

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BACKGROUND: The HPTN 083 trial demonstrated superiority of a regimen containing long-acting injectable cabotegravir (CAB) to daily oral tenofovir/emtricitabine (TDF/FTC) for HIV pre-exposure prophylaxis (PrEP) among men who have sex with men (MSM) and transgender women. We estimated and compared the potential impact of TDF/FTC and CAB use among MSM in Atlanta, Georgia, US, where 21% of HIV-negative MSM used oral PrEP in 2018.
METHODS: An age-, race- and risk-stratified HIV transmission model for MSM (risk based on PrEP eligibility criteria) was parameterised and calibrated with Atlanta-specific behavioural, HIV prevalence and PrEP usage data, assuming PrEP was only offered to eligible high-risk MSM (~60% of MSM). We estimated the proportion of new HIV infections averted over one/five years if TDF/FTC use were maintained, or if all TDF/FTC users switched to CAB in January 2021, compared with no PrEP use. CAB scenarios with 10% and 20% more users were also considered. CAB effectiveness (efficacyÃ?adherence; 92%) was estimated through back-calculations from HPTN 083 data. TDF/FTC efficacy and race-/age-specific adherence ('¥4 doses/week; 96%,73-94%) were based on iPrEx trial and US PrEP Demo project data.
RESULTS: Our model predicted that TDF/FTC at current uptake levels would avert 32.4% of new HIV infections (95% credible interval 26.2-41.5%) among Atlanta MSM over 2021, vs. no PrEP. Switching to CAB may prevent 27% more infections than TDF/FTC, for a total 41.2% (27.8-45.3%) infections prevented. Increasing CAB usage by 10 or 20% increased infections averted by 13% and 34%, to 46.3% and 55.0% overall vs. no PrEP, respectively. Predicted five-year impacts (vs. no PrEP) were 13-17% greater than one-year impacts across scenarios (Figure).


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CONCLUSIONS: TDF/FTC and CAB could both prevent many new HIV infections among Atlanta MSM, with CAB likely to prevent more infections than TDF/FTC at similar or greater reported usage, due to higher sex-act coverage achieved by bi-monthly injections.