Receptive anal intercourse (RAI) contributes significantly to HIV acquisition underscoring the need to develop HIV prevention options for populations engaging in RAI practices. We explored the feasibility of formulating rectal suppositories with potent antiviral drugs for on-demand use. A fixed-dose combination of tenofovir (TFV) and elvitegravir (EVG) (40 mg each) was co-formulated in six different suppository bases (three fat- and three water-soluble). Fat-soluble witepsol H15 and water-soluble polyethylene glycol (PEG) based suppositories demonstrated favorable in vitro release and were advanced to assess in vivo pharmacokinetics following rectal administration in macaques. In vivo drug release profiles were similar for both suppository bases. Median concentrations of TFV and EVG detected in rectal fluids at 2 h were 1- and 2-logs higher than the in vitro IC50, respectively; TFV-diphosphate levels in rectal tissues met or exceeded those associated with high efficacy against rectal simian HIV (SHIV) exposure in macaques. Leveraging on these findings, a PEG-based suppository with a lower dose combination of tenofovir alafenamide (TAF) and EVG (8 mg each) was developed and found to achieve similar rectal drug exposures in macaques. This study establishes the utility of rectal suppositories as a promising on-demand strategy for HIV PrEP and supports their clinical development.

Pre-exposure prophylaxis (PrEP) with a weekly oral regimen of antiretroviral drugs could be a suitable preventative option for individuals who struggle with daily PrEP or prefer not to use long-acting injectables. We assessed in macaques the efficacy of weekly oral tenofovir alafenamide (TAF) at doses of 13.7 or 27.4 mg/kg. Macaques received weekly oral TAF for six weeks and were exposed twice-weekly to SHIV vaginally or rectally on day 3 and 6 after each dose. Median TFV-DP levels in PBMCs following the 13.7 mg/kg dose were 3110 and 1137 fmols/10⁶ cells on day 3 and 6, respectively. With the 27.4 mg/kg dose, TFV-DP levels were increased (~2-fold) on day 3 and 6 (6095 and 3290 fmols/10⁶ cells, respectively). Both TAF doses (13.7 and 27.4 mg/kg) conferred high efficacy (94.1% and 93.9%, respectively) against vaginal SHIV infection. Efficacy of the 27.4 mg/kg dose against rectal SHIV infection was 80.7%. We estimate that macaque doses of 13.7 and 27.4 mg/kg are equivalent to approximately 230 and 450 mg of TAF in humans, respectively. Our findings demonstrate the effectiveness of a weekly oral PrEP regimen and suggest that a clinically achievable oral TAF dose could be a promising option for non-daily PrEP.

Background/Objectives: The prevention of sexual HIV-1 acquisition in women and girls in sub-Saharan Africa remains an important public health priority. Expanding the existing biomedical product portfolio to include long-acting vaginal products, such as intravaginal rings (IVRs), is expected to appeal to end users and drive adoption. Methods: We formulated two different triple-combination antiretroviral IVRs, both delivering the acid salt tenofovir (TFV), disoproxil fumarate (TDF), and the free base emtricitabine (FTC), with one delivering elvitegravir (EVG) as the free acid and the other as the sodium salt. The devices were evaluated for pharmacokinetics and local safety in two established preclinical models, sheep and pig-tailed macaques. Results: The IVRs were safe and maintained cervicovaginal fluid (CVF) drug concentrations that were above our efficacy targets derived from prior humanized mouse studies. All three agents were uniformly distributed vaginally, as evidenced by CVF and vaginal tissue measurements. Elevated drug concentrations were observed in macaque vaginal tissue samples collected three days after IVR removal, suggesting a possible forgiveness window. TFV and FTC concentrations in rectal tissue and fluid suggested potential for dual-compartment HIV-1 protection, although the vaginal-to-rectal drug transport mechanism appeared to differ across both species. The humanized mouse vaginal HIV-1 efficacy model was used to empirically compare combination effects when TDF, FTC, and EVG were co-administered, and TDF-EVG was identified as a promising combination to be developed further for IVR delivery in parallel with the triple combination.

Prevention of HIV infection and unintended pregnancies are public health priorities. In sub-Saharan Africa, where HIV prevalence is highest, depot medroxyprogesterone acetate (DMPA) is widely used as contraception. Therefore, understanding potential interactions between DMPA and antiretrovirals is critical. Here, we use a macaque model to investigate the effect of DMPA on the pharmacology of the antiretroviral tenofovir alafenamide (TAF). Female rhesus macaques received 30 mg of DMPA (n = 9) or were untreated (n = 9). Macaques received a human equivalent dose of TAF (1.5 mg/kg) orally by gavage. Tenofovir (TFV) and TFV-diphosphate (TFV-DP) were measured in blood, secretions, and tissues over 72 h. The median area under the curve (AUC_0–72h) values for TFV-DP in peripheral blood mononuclear cells were similar in DMPA-treated (6991 fmol*h/10⁶ cells) and untreated controls (5256 fmol*h/10⁶ cells) (P = 0.174). Rectal tissue TFV-DP concentrations from DMPA+ animals [median: 20.23 fmol/mg of tissue (range: 4.94–107.95)] were higher than the DMPA- group [median: below the limit of quantification (BLOQ-11.92)], (P = 0.019). TFV-DP was not detectable in vaginal tissue from either group. A high-dose DMPA treatment in macaques was associated with increased rectal TFV-DP levels, indicating a potential tissue-specific drug-drug interaction. The lack of detectable TFV-DP in the vaginal tissue warrants further investigation of PrEP efficacy with single-agent TAF products. DMPA did not affect systemic TAF metabolism, with similar PBMC TFV-DP in both groups, suggesting that DMPA use should not alter the antiviral activity of TAF.

Background: Second‐generation HIV‐1 integrase strand transfer inhibitors (INSTIs)—bictegravir (BIC), cabotegravir (CAB), and dolutegravir (DTG)—are leading components of highly potent antiretroviral therapy, and CAB is also used for long‐acting chemoprevention. Rapid detection of clinically relevant INSTI concentrations could support point‐of‐care assessment and real‐time clinical decision‐making. We developed a lateral flow assay (LFA) that detects BIC, CAB, and DTG in whole blood and plasma and evaluated its performance against predefined concentration thresholds and high‐performance liquid chromatography‐tandem mass spectrometry (LC‐MS/MS). Methods: A single LFA cassette design was developed using a monoclonal antibody to distinguish BIC, CAB, and DTG concentrations below trough, at minimal‐to‐moderate trough, and at ideal concentrations. LFA results were read visually at 20 min and were compared with LC‐MS/MS–quantified INSTI concentrations for 124 clinical plasma specimens. Results: For 24 plasma samples from US participants receiving treatment involving one of the three INSTIs, the LFA interpretations matched all LC‐MS/MS results except for one DTG specimen, which was interpreted by LFA as 1.0–1.6 μg/mL but measured 2.1 μg/mL by LC‐MS/MS. Among 100 plasma remnants from routine national surveillance in Eswatini, the LFA correctly interpreted DTG concentrations in 95 specimens. Four specimens had DTG LC‐MS/MS concentrations slightly above the LFA‐determined range, differing by ≤ 0.1 μg/mL, and one specimen measured at 1.20 μg/mL by LC‐MS/MS was interpreted as ≥ 1.6 μg/mL by LFA. In total, 6 of 124 specimens (4.8%) had LFA‐interpreted INSTI concentrations that varied slightly from the LC‐MS/MS results, with no statistically significant difference in overall performance by Wilcoxon signed‐rank test ( W = 8.00, p = 0.94, one‐tailed). Conclusions: The LFA design successfully provided clinically useful interpretations of BIC, CAB, and DTG concentrations with minor discrepancies in < 5% of samples. Importantly, all low‐concentration samples of < 1 μg/mL were correctly interpreted by LFA. The assay shows promise as a point‐of‐care tool for assessing clinically relevant INSTI concentrations.