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Dapivirine (DPV) is a potent NNRTI used to prevent the sexual transmission of HIV. In a phase 1 trial (IPM 028), the concomitant use of a DPV vaginal ring and an antifungal miconazole (MIC) vaginal capsule was found to increase the systemic exposure to DPV in women, suggesting a potential for drug-drug interactions. This study’s objective was to investigate the mechanism of DPV-MIC interactions using drug-metabolizing enzymes (DMEs; CYPs and UGTs) that are locally expressed in the female reproductive tract (FRT). In vitro studies were performed to evaluate the metabolism of DPV and its inhibition and induction potential with DMEs. In addition, the impact of MIC on DPV metabolism and the inhibitory potential of DPV with DMEs were studied. Our findings suggest that DPV is a substrate of CYP1A1 and CYP3A4 enzymes and that MIC significantly decreased the DPV metabolism by inhibiting these two enzymes. DPV demonstrated potent inhibition of CYP1A1 and moderate/weak inhibition of the six CYP and eight UGT enzymes evaluated. MIC showed potent/moderate inhibition of seven CYP enzymes and weak/no inhibition of eight UGT enzymes. The combination of DPV and MIC showed potent inhibition of seven CYP enzymes (1A1, 1A2, 1B1, 2B6, 2C8, 2C19, and 3A4) and four UGT enzymes (1A3, 1A6, 1A9, and 2B7). DPV was not an inducer of CYP1A2, CYP2B6, and CYP3A4 enzymes in primary human hepatocytes. Therefore, the increased systemic concentrations of DPV observed in IPM 028 were likely due to the reduced metabolism of DPV because of CYP1A1 and CYP3A4 enzymes inhibition by MIC in the FRT.

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.

The dapivirine (DPV) vaginal ring was developed by the nonprofit International Partnership for Microbicides (IPM) for reducing the risk of HIV infection. A clinical study (IPM 028) showed that concomitant use of the DPV ring and miconazole (MIC) altered DPV pharmacokinetic profile. In this work, we investigated whether or not DPV transport and permeation contributed to the observed DPV-MIC interaction. Our study evaluated the interaction between DPV and several transporters that are highly expressed in the human female reproductive tract, including MRP1, MRP4, P-gp, BCRP, and ENT1, using vesicular and cellular systems. We also evaluated the impact of DPV/MIC on cellular tight junctions by monitoring transepithelial electrical resistance with the Ussing chamber. Lastly, we evaluated the effect of MIC on DPV permeability across human cervical tissue. Our findings showed that DPV was not a substrate of MRP1, MRP4, P-gp, BCRP, or ENT1 transporters. Additionally, DPV did not inhibit the activity of these transporters. DPV, MIC, and their combination also did not disrupt cellular tight junctions. MIC did not affect DPV tissue permeability but significantly reduced DPV tissue levels. Therefore, our results suggest that the DPV-MIC interaction is not due to these five transporters, altered tight junction integrity, or altered tissue permeability.

Background/Objectives: With the ongoing efforts in supporting the discovery of novel targeted drug delivery systems for the upper region of the female reproductive tract (FRT), it is imperative to understand the local drug disposition pathways. We aim to obtain a comprehensive profile of the drug transporters and drug-metabolizing enzymes in the human ectocervix, uterus, and fallopian tubes, as these factors may substantially influence mucosal penetration, tissue exposure, drug disposition, and the risk of drug–drug interactions. Methods: Gene expression of 12 drug transporters and 21 drug-metabolizing enzymes was quantified using RT-qPCR. Protein expression of highly expressed transporters was assessed using immunohistochemistry (IHC). Results: Among the 12 transporters analyzed, the efflux transporters P-gp, BCRP, and MRP4 exhibited the highest expression across the ectocervix, endometrium, myometrium, and fallopian tubes, with P-gp consistently showing the greatest abundance in all evaluated FRT tissues. Expression of these transporters was significantly higher (6–17×) in myometrium compared with ectocervix. IHC demonstrated strong localization of P-gp, BCRP, and MRP4 to epithelial layers facing the lumen, as well as to stromal and vascular endothelial cells. For drug-metabolizing enzymes, all 21 phase I and II enzymes were detectable across the FRT, and 15 were expressed at comparatively higher levels across all tissue types. These included CYP1A1, CYP1B1, CYP2B6, CYP2C8, CYP2C19, CYP3A4, UGT1A1, UGT1A3, UGT1A4, UGT1A7, UGT1A8, UGT1A10, UGT2B4, UGT2B15, and UGT2B17. Conclusions: The gene expression and localization data obtained from this work may improve our understanding of drug disposition in the FRT, which will inform selection, design, and optimization of drugs intended for targeted delivery within the FRT.

Background/Objectives: Given the potential for achieving high concentrations at the target site while limiting systemic exposure, delivering drugs directly to the female reproductive tract (FRT) is emerging as a promising strategy for enhancing women’s reproductive health. However, quantitative data describing matrix-specific solubility, matrix-specific binding, and permeability across FRT tissues remain limited, constraining development of physiologically based pharmacokinetic (PBPK) models for intravaginal and intrauterine therapies. Methods: Our work was conducted to help fill this critical gap, evaluating four model drugs with diverse physicochemical and transporter profiles, dapivirine (DPV), levonorgestrel (LNG), MK-2048, and 4′-ethynyl-2-fluoro-2′-deoxyadenosine (EFdA; also known as islatravir or MK-8591) in in vitro and ex vivo human models. Plasma solubility, matrix-specific binding in plasma, cervicovaginal fluid, and FRT tissues, and bidirectional permeability across FRT tissues were quantified. Results: Our results demonstrated that the plasma solubility varied markedly across compounds, following lipophilicity trends, with DPV (34.14 ± 1.04 µg/mL) and EFdA (1808.02 ± 67.36 µg/mL) exhibiting the lowest and highest solubility, respectively. Hydrophobicity-dependent solubility enhancement by plasma proteins (~2× to >30× higher comparing to aqueous solubility in the literature) was observed for all four model drugs. Apparent binding in plasma, cervicovaginal fluid, and FRT tissues was highly correlated with the model compounds’ lipophilicity, with DPV having the most highly matrix-specific binding (97–99%) and EFdA having the least matrix-specific binding with the greatest variability (15–62%). Regional permeability differed significantly across FRT tissues: the human ectocervix, myometrium, endometrium, and fallopian tubes demonstrated distinct transport patterns consistent with epithelial architecture and the transporter-substrate status of the model compounds. Efflux transporter involvement was evident for MK-2048 and EFdA in Caco-2 models (efflux ratios 2.59 and 7.14, respectively), but was less pronounced in the 3D vaginal model and ex vivo tissues. Across all datasets, permeability and binding were strongly influenced by drug lipophilicity and ionization characteristics. Conclusions: Collectively, these findings demonstrate the interplay among solubility, matrix-specific binding, and tissue permeability in governing local drug distribution within the FRT. The experimentally derived parameters provide quantitative inputs for FRT PBPK model development, and are expected to inform design of safe and effective localized therapies for women’s reproductive health.