There are limited data on the prevalence of fostemsavir (FTR) resistance-associated polymorphisms in people with HIV in Botswana. We sought to determine the prevalence of FTR resistance-associated polymorphisms in HIV-1 subtype C sequences from antiretroviral therapy (ART)-naïve and ART-experienced individuals in Botswana. Previously reported FTR resistance-associated polymorphisms from literature were surveyed from HIV-1C proviral sequences generated from a large HIV-1 population-based cohort enrolled between 2013 and 2018. Sequences from ART-naïve and ART-experienced individuals were included in the analysis. A total of 6,078 participants with gp120 sequences were included in this study, and 6,030 (99.2%) had known ART status; 1,282 (21.3%) were from ART-naïve individuals, while 4,748 (78.7%) were from individuals on ART at study enrollment. Viral load (VL) data were available for 4,739 (99.8%) ART-experienced individuals, of whom 4,526 (95.5%) were suppressed and 213 (4.5%) had virologic failure (VF) (VL >400). Among those with VF and ART naive, the overall prevalence of FTR resistance was 13.3% (95% CI 11.6%-15.1%) and did not differ between ART-experienced with VF individuals (29/213, 13.6%) and ART-naïve individuals (170/1,282, 13.3%) (P-value = 0.9). The most predominant mutations (prevalence ≥1.0%) were M434I (9.8%), M475I (5.9%), and M426L (1.1%). The overall prevalence of FTR polymorphisms was similar in both ART-naïve and ART-experienced individuals with VF in a setting with no prior FTR exposure. We recommend further studies on the phenotypic impact of these polymorphisms to guide how to monitor for FTR resistance. (This study has been registered at ClinicalTrials.gov under registration no. NCT01965470.) IMPORTANCE Fostemsavir (FTR) is a newly licensed antiretroviral drug that has been shown to have activity against HIV-1. The mechanism of action of FTR is different from all currently available antiretrovirals (ARVs), and as such, it offers hope for HIV-1 suppression in those people with HIV (PWH) who harbor HIV-1 variants with drug resistance mutations to currently used ARVs. Using 6,030 HIV-1 sequences covering the HIV-1 envelope from PWH in Botswana who are antiretroviral therapy (ART) naïve as well as those who are failing ART, we explored the sequences for FTR resistance-associated polymorphisms. We found the prevalence of FTR polymorphisms to be similar in both ART-naïve and ART-experienced individuals with VF in this setting, with no prior FTR exposure. Further studies on the phenotypic impact of these polymorphisms are warranted to guide how to monitor for FTR resistance.

Keywords: Botswana; HIV-1 C; drug-resistant mutations (DRMs); entry inhibitors; fostemsavir (FTR); polymorphisms.