Background The secondary lymphoid tissues (LTs), lymph nodes (LNs) and gut-associated lymphoid tissue (GALT) are considered reservoirs for HIV. Antiretrovirals (ARVs) have lower penetration into LT. In vitro models predictive of ARV LT penetration have not been established. Objectives To develop an in vitro model of LT bioavailability using human lymphoid endothelial cells (HLECs) and investigate its predictability with in vivo pharmacokinetic (PK) studies in mice. Methods ARV bioavailability in HLECs was evaluated at the maximum plasma concentration (Cmax) observed in HIV-infected patients. ARVs were: abacavir, atazanavir, darunavir, dolutegravir, efavirenz, elvitegravir, emtricitabine, maraviroc, raltegravir, rilpivirine, ritonavir, tenofovir disoproxil fumarate and the PK booster cobicistat. The LT PK of representative drugs showing high (efavirenz), intermediate (dolutegravir) and low (emtricitabine) HLEC bioavailability was investigated in BALB/c mice given 50/10/30 mg/kg efavirenz/dolutegravir/emtricitabine orally, daily for 3 days. The concordance of in vitro and in vivo ARV bioavailability was examined. Results ARVs showed high (>67th percentile; rilpivirine, efavirenz, elvitegravir and cobicistat), intermediate (67th–33rd percentile; ritonavir, tenofovir disoproxil fumarate, dolutegravir and maraviroc) and low (<33rd percentile; atazanavir, darunavir, raltegravir, emtricitabine and abacavir) HLEC bioavailability. The hierarchy of efavirenz, dolutegravir and emtricitabine bioavailability in LN, gut and brain tissues of mice was: efavirenz>dolutegravir>emtricitabine. Conclusions ARVs displayed distinct HLEC penetration patterns. PK studies of representative ARVs in LT of mice were concordant with HLEC bioavailability. These findings support further development of this approach and its translational predictability in humans.

The secondary lymphoid tissues (LT), lymph nodes (LN) and gut-associated lymphoid tissue are the primary sites of HIV replication and where the latent pool of virus is maintained. We compared the pharmacokinetics of tenofovir disoproxil fumarate (TDF) and tenofovir alafenamide (TAF) in LT of 13 HIV-infected persons receiving a TDF-containing antiretroviral regimen who subsequently switched to a TAF-containing regimen. Study participants were on stable antiretroviral therapy for ≥12 months with plasma HIV-RNA < 48 copies/mL for 6 months before enrollment and entry CD4 cell counts > 300 cells/µL. Intracellular concentrations of tenofovir-diphosphate (TFV-DP) and emtricitabine-triphosphate (FTC-TP) were quantified in PBMCs and in mononuclear cells obtained from LN, ileum and rectal tissues. With TAF, the TFV-DP concentrations in PBMCs and LN were 7.3-fold and 6.4-fold higher (ratios of geometric means of TAF to TDF), respectively, compared with TDF; ileal and rectal concentrations, however, were lower with geometric mean ratios of 0.14 and 0.18, respectively. A statistically significant relationship was observed between PBMC and LN concentrations of TFV-DP. During TDF-containing therapy, the expected effect of cobicistat to increase TFV plasma concentrations was observed, as were higher TFV-DP concentrations in PBMCs and mononuclear cells from LN, ileum and rectal tissues. The higher TFV-DP concentrations achieved with TAF in the LN provides the first human correlate of the observation in animals that TAF produced higher tenofovir LN concentrations. The ability to increase LN concentrations allows investigations of whether antiretroviral regimens with improved LN pharmacokinetics elicit a more complete virologic response in that compartment.

current strategies to treat tuberculosis (tB) and co-morbidities involve multidrug combination therapies. Rifamycin antibiotics are a key component of tB therapy and a common source of drugdrug interactions (DDis) due to induction of drug metabolizing enzymes (DMes). Management of rifamycin DDIs are complex, particularly in patients with co-morbidities, and differences in DDI potential between rifamycin antibiotics are not well established. DME profiles induced in response to tuberculosis antibiotics (rifampin, rifabutin and rifapentine) were compared in primary human hepatocytes. We identified rifamycin induced DMEs, cytochrome P450 (CYP) 2C8/3A4/3A5, SULT2A, and UGT1A4/1A5 and predicted lower DDIs of rifapentine with 58 clinical drugs used to treat co-morbidities in tB patients. transcriptional networks and upstream regulator analyses showed FOXA3, HNF4α, NR1I2, NR1I3, NR3C1 and RXRα as key transcriptional regulators of rifamycin induced DMEs. Our study findings are an important resource to design effective medication regimens to treat common co-conditions in tB patients.

Background Multiple tissue reservoirs are established soon after HIV infection, and some tissues may also be pharmacological sanctuaries. Parenteral administration of antiretroviral (ARV) drugs for treatment and prevention of HIV infection is an active area of drug development. The influence of route of administration on ARV tissue pharmacokinetics is not known. Objectives To investigate ARV pharmacokinetics in lymphatic and select non-lymphatic tissues (e.g. brain and testes) after intramuscular and subcutaneous administration compared with oral in BALB/c mice. Methods Tissue concentrations of cobicistat, efavirenz, elvitegravir, maraviroc, rilpivirine, tenofovir alafenamide and tenofovir disoproxil fumarate were determined. The tissue penetration ratio (TPR) was the primary measure for comparison; a change in TPR arises from factors affecting tissue distribution controlling for changes in systemic bioavailability. Results Intramuscular and subcutaneous delivery increased TPRs in the lymph node and spleen for 27 of 28 (96%) drug administration events. Decreased TPRs, however, were found in some tissues such as the brain and testes. Conclusions These results demonstrate a change in route of drug administration from oral to intramuscular or subcutaneous can change tissue uptake. This has implications for HIV pharmacotherapy. For example, HIV persists in lymphoid tissues despite long-term oral ARV therapy, and low ARV concentrations have been found in lymphoid tissues. The improved ARV lymphatic tissue bioavailability with intramuscular and subcutaneous administration allows future studies to investigate these routes of drug administration as a therapeutic manoeuvre to limit viral persistence and eliminate viral sanctuaries in the lymphatic tissues, which is a prerequisite for eradication of HIV.

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