Interaction of Rifampin and Darunavir-Ritonavir or Darunavir-Cobicistat In Vitro

The Effect of Rifampicin on Darunavir, Ritonavir, and Dolutegravir Exposure within Peripheral Blood Mononuclear Cells: a Dose Escalation Study

Ritonavir-boosted darunavir (DRV/r) and dolutegravir (DTG) are affected by induction of metabolizing enzymes and efflux transporters caused by rifampicin (RIF). This complicates the treatment of people living with HIV (PLWH) diagnosed with tuberculosis. Recent data showed that doubling DRV/r dose did not compensate for this effect, and hepatic safety was unsatisfactory. We aimed to evaluate the pharmacokinetics of DRV, ritonavir (RTV), and DTG in the presence and absence of RIF in peripheral blood mononuclear cells (PBMCs). PLWH were enrolled in a dose-escalation crossover study with 6 treatment periods of 7 days. Participants started with DRV/r 800/100 mg once daily (QD), RIF and DTG were added before the RTV dose was doubled, and then they received DRV/r 800/100 twice daily (BD) and then 1,600/200 QD or vice versa. Finally, RIF was withdrawn. Plasma and intra-PBMC drug concentrations were measured through validated liquid chromatography-tandem mass spectrometry (LC-MS/MS) methods. Seventeen participants were enrolled but only 4 completed all study phases due to high incidence of liver toxicity. Intra-PBMC DRV trough serum concentration (C_trough) after the addition of RIF dropped from a median (interquartile range [IQR]) starting value of 261 ng/mL (158 to 577) to 112 ng/mL (18 to 820) and 31 ng/mL (12 to 331) for 800/100 BD and 1,600/200 QD DRV/r doses, respectively. The DRV intra-PBMC/plasma ratio increased significantly (P = 0.003). DTG and RIF intra-PBMC concentrations were in accordance with previous reports in the absence of RIF or DRV/r. This study showed a differential impact of enzyme and/or transporter induction on DRV/r concentrations in plasma and PBMCs, highlighting the usefulness of studying intra-PBMC pharmacokinetics with drug-drug interactions. (This study has been registered at ClinicalTrials.gov under registration no. NCT03892161.)

In utero exposure to antiretroviral drugs and pregnancy outcomes: Analysis of the French ANRS pharmacovigilance database

AIMS

In 2018, 1.07 million pregnant women received antiretroviral drugs, raising whether this affects pregnancy outcomes. We assessed the adverse pregnancy outcomes associated with prenatal antiretroviral drug exposure, notified to the French ANRS pharmacovigilance system.

METHODS

An exhaustive case report series has been performed using the ANRS pharmacovigilance database. All ANRS-sponsored HIV clinical research studies using antiretroviral drugs either in pregnant women or women of childbearing age were eligible from 2004 to 2019. We analysed the following pregnancy outcomes: abortion, ectopic pregnancy, stillbirth, prematurity (<37 weeks of gestational age), low birth weight (<2500 g) and congenital abnormalities. A logistic regression was performed to assess the odds ratio (OR) for each outcome separately (if occurrence >50) compared to the outcome observed when exposed to non-nucleoside-reverse-transcriptase-inhibitor (NNRTI)-based regimen as the reference.

RESULTS

Among the 34 studies selected, 918 deliveries occurred, of whom 88% had pregnancy outcomes documented. Pregnant women were mainly exposed to PI (n = 387, 48.6%), NNRTI (n = 331, 41.5%) and INI-based combinations (n = 40, 5.0%, 18 on dolutegravir). Compared to NNRTI-based combinations, there was no significant association observed with exposure to other antiretroviral combination for spontaneous abortion, prematurity or low birth weight, except an increased risk of low birth weight in new-born exposed to exclusive nucleoside-reverse-transcriptase-inhibitor (NRTI) combinations (n = 4; OR 7.50 [1.49-37.83]).

CONCLUSIONS

Our study, mainly based on protease inhibitor (PI) and NNRTI-based regimens, is overall reassuring on the risk of adverse pregnancy outcomes, except for NRTI which should be interpreted cautiously (small number, indication bias). In this study, the number of integrase inhibitor (INI)-based combinations was too low to draw any conclusions.

In vitro assessment of the potential for dolutegravir to affect hepatic clearance of levonorgestrel

Objectives:

The World Health Organization recommends that all countries adopt dolutegravir-based antiretroviral therapy as the preferred regimen for all individuals living with HIV. Levonorgestrel is a commonly used hormonal contraceptive, which undergoes drug–drug interactions with some antiretrovirals, but the potential interaction between dolutegravir and levonorgestrel has not been examined. We aimed to evaluate cytochrome P450 (CYP)-mediated levonorgestrel metabolism and quantify the effects of dolutegravir on levonorgestrel apparent intrinsic clearance (CL_int.app.) and CYP gene expression.

Methods:

In vitro CYP-mediated CL_int.app. of levonorgestrel was quantified using a recombinant human CYP (rhCYP) enzyme system. A primary human hepatocyte model of drug metabolism was used to assess the effects of dolutegravir on (1) levonorgestrel CL_int.app., using liquid chromatography-tandem mass spectrometry, and (2) the expression of specific CYP enzymes, using quantitative real-time polymerase chain reaction.

Results:

Levonorgestrel clearance was mediated by multiple rhCYPs, including rhCYP3A4. Under control conditions, levonorgestrel CL_int.app. was 22.4 ± 5.0 μL/min/10⁶ hepatocytes. Incubation with 43.1 nM of unbound dolutegravir elevated levonorgestrel CL_int.app. to 31.4 ± 7.8 μL/min/10⁶ hepatocytes (P = 0.168), while 142.23 nM increased levonorgestrel CL_int.app. to 37.0 ± 2.9 μL/min/10⁶ hepatocytes (P = 0.012). Unbound dolutegravir ≥ 431 nM induced expression of CYP3A4 (≥ two-fold) in a dose-dependent manner, while 1.44 μM of unbound dolutegravir induced CYP2B6 expression 2.2 ± 0.3-fold (P = 0.0004).

Conclusions:

In summary, this in vitro study suggests that dolutegravir has the potential to increase hepatic clearance of levonorgestrel by inducing both CYP3A and non-CYP3A enzymes. The observed in vitro dolutegravir–levonorgestrel drug–drug interaction should be further examined in clinical studies.

Utilization of Physiologically Based Pharmacokinetic Modeling in Clinical Pharmacology and Therapeutics: an Overview

The purpose of this review was to assess the advancement of applications for physiologically based pharmacokinetic (PBPK) modeling in various therapeutic areas. We conducted a PubMed search, and 166 articles published between 2012 and 2018 on FDA-approved drug products were selected for further review. Qualifying publications were summarized according to therapeutic area, medication(s) studied, pharmacokinetic model type utilized, simulator program used, and the applications of that modeling. The results showed a 13-fold increase in the number of papers published from 2012 to 2018, with the largest proportion of articles dedicated to the areas of infectious diseases, oncology, and neurology, and application extensions including prediction of drug-drug interactions due to metabolism and/or transporter-mediated effects and understanding drug kinetics in special populations. In addition, we profiled several high-impact studies whose results were used to guide package insert information and formulate dose recommendations. These results show that while utilization of PBPK modeling has drastically increased over the past several years, regulatory support, lack of easy-to-use systems for clinicians, and challenges with model validation remain major challenges for the widespread adoption of this practice in institutional and ambulatory settings. However, PBPK modeling will continue to be a useful tool in the future to assess therapeutic drug monitoring and the growing field of personalized medicine.

Pharmacokinetic profile and safety of adjusted doses of darunavir/ritonavir with rifampicin in people living with HIV

BACKGROUND

Darunavir/ritonavir is better tolerated than lopinavir/ritonavir and has a higher genetic barrier to resistance. Co-administration with rifampicin has been contraindicated as a significant reduction in darunavir exposure is expected. This is a barrier to darunavir/ritonavir use where TB is endemic.

OBJECTIVES

To evaluate the safety and pharmacokinetic profile of adjusted doses of darunavir/ritonavir with rifampicin.

METHODS

Virally suppressed participants on second-line lopinavir/ritonavir-based ART were switched to darunavir/ritonavir 800/100 mg q24h. In sequence: rifampicin was added; the dose of ritonavir was escalated; and darunavir was increased (darunavir/ritonavir 1600/200 mg q24h and 800/100 mg q12h were given in randomized sequence with rifampicin). Darunavir plasma concentrations were measured on the seventh/last day of each treatment period. To prevent viral rebound, dolutegravir (50 mg q12h) was added during rifampicin administration and for 1 week thereafter. Clinical events, ALT and bilirubin were monitored every 2-3 days during rifampicin administration.

RESULTS

A total of 17/28 participants started study treatment. Six (35.3%) were withdrawn for symptomatic hepatitis with severe ALT elevations, developing after 9-11 days of rifampicin and 2-4 days of ritonavir 200 mg. The study was stopped prematurely due to this high rate of hepatotoxicity. Only four participants completed the study. All hepatotoxicity resolved on withdrawal of study treatment. All participants were successfully re-established on their lopinavir/ritonavir-based regimen. After doubling the darunavir/ritonavir doses on rifampicin, darunavir pre-dose concentrations approached those on standard doses without rifampicin for q12h doses, but not for q24h doses.

CONCLUSIONS

Adjusted doses of darunavir/ritonavir with rifampicin had unacceptable risk of hepatotoxicity. Darunavir trough concentrations were markedly reduced with the daily adjusted dose.

Darunavir-cobicistat-emtricitabine-tenofovir alafenamide: safety and efficacy of a protease inhibitor in the modern era

A fixed-dose combination consisting of darunavir (Drv), cobicistat (Cobi), emtricitabine (2′,3′-dideoxy-5-fluoro-3′-thiacytidine [FTC]), and tenofovir alafenamide (Taf) has been recently approved by the European Medicines Agency for the treatment of HIV infection, and is the first ever protease-inhibitor-based single-tablet regimen. This article provides a detailed description of its pharmacokinetic, efficacy, and safety profile. The pharmacokinetics of single compounds were analyzed, with a special focus on contrasts between Drv/Cobi and Drv/ritonavir (Rtv). When comparing Cobi and Rtv, multiple interactions must be taken into account: in comparison to Rtv, Cobi is a more selective CYP3A4 inhibitor and has no clinical effect on other isoenzymes inhibited by Rtv (eg, 2C8 and 2C9). Moreover, unlike Cobi, Rtv shows in vivo induction activity on some CYP isoenzymes (eg, 1A2, 2C19, 2C8, 2C9, and 2B6), glucuronyltransferases (eg, UGT1A4), and Pgp. Drv-Cobi-FTC-Taf has recently been demonstrated to be of equal efficacy to Drv-Rtv and other protease inhibitors in both experienced (EMERALD study) and naïve (AMBER study) patients. Moreover, kidney and bone safety profiles have been shown to be good, as has central nervous system tolerance. Total cholesterol:low-density-lipoprotein cholesterol and total cholesterol:high-density-lipoprotein cholesterol ratios are generally high in Drv-Cobi-FTC-Taf vs Rtv-Drv-FTC + tenofovir disoproxil fumarate. An unlikely role of Drv in influencing cardiovascular risk in HIV infection has also been reported. Kidney safety profile is influenced by Cobi, with an increase in creatinine plasma concentration of 0.05–0.1 mg/dL and a parallel glomerular filtration-rate reduction of 10 mL/min within the first 4 weeks after Cobi introduction, which remains stable during treatment. Bone and central nervous system safety profiles were found to be good in randomized clinical trials of both experienced and naïve patients. The efficacy and safety of Drv/Cobi/FTC/Taf are comparable to other drug regimens recommended for HIV treatment.

Derivation of CYP3A4 and CYP2B6 degradation rate constants in primary human hepatocytes: A siRNA-silencing-based approach

The first-order degradation rate constant (k_deg) of cytochrome P450 (CYP) enzymes is a known source of uncertainty in the prediction of time-dependent drug-drug interactions (DDIs) in physiologically-based pharmacokinetic (PBPK) modelling. This study aimed to measure CYP k_deg using siRNA to suppress CYP expression in primary human hepatocytes followed by incubation over a time-course and tracking of protein expression and activity to observe degradation. The magnitude of gene knockdown was determined by qPCR and activity was measured by probe substrate metabolite formation and CYP2B6-Glo™ assay. Protein disappearance was determined by Western blotting. During a time-course of 96 and 60 h of incubation, over 60% and 76% mRNA knockdown was observed for CYP3A4 and CYP2B6, respectively. The k_deg of CYP3A4 and CYP2B6 protein was 0.0138 h^-1 (±0.0023) and 0.0375 h^-1 (±0.025), respectively. The k_deg derived from probe substrate metabolism activity was 0.0171 h^-1 (±0.0025) for CYP3A4 and 0.0258 h^-1 (±0.0093) for CYP2B6. The CYP3A4 k_deg values derived from protein disappearance and metabolic activity were in relatively good agreement with each other and similar to published values. This novel approach can now be used for other less well-characterised CYPs.

Cobicistat Versus Ritonavir: Similar Pharmacokinetic Enhancers But Some Important Differences

OBJECTIVE

To describe properties of cobicistat and ritonavir; compare boosting data with atazanavir, darunavir, and elvitegravir; and summarize antiretroviral and comedication interaction studies, with a focus on similarities and differences between ritonavir and cobicistat. Considerations when switching from one booster to another are discussed.

DATA SOURCES

A literature search of MEDLINE was performed (1985 to April 2017) using the following search terms: cobicistat, ritonavir, pharmacokinetic, drug interactions, booster, pharmacokinetic enhancer, HIV, antiretrovirals. Abstracts from conferences, article bibliographies, and product monographs were reviewed.

STUDY SELECTION AND DATA EXTRACTION

Relevant English-language studies or those conducted in humans were considered.

DATA SYNTHESIS

Similar exposures of elvitegravir, darunavir, and atazanavir are achieved when combined with cobicistat or ritonavir. Cobicistat may not be as potent a CYP3A4 inhibitor as ritonavir in the presence of a concomitant inducer. Ritonavir induces CYP1A2, 2B6, 2C9, 2C19, and uridine 5'-diphospho-glucuronosyltransferase, whereas cobicistat does not. Therefore, recommendations for cobicistat with comedications that are extrapolated from studies using ritonavir may not be valid. Pharmacokinetic properties of the boosted antiretroviral can also affect interaction outcome with comedications. Problems can arise when switching patients from ritonavir to cobicistat regimens, particularly with medications that have a narrow therapeutic index such as warfarin.

CONCLUSIONS

When assessing and managing potential interactions with ritonavir- or cobicistat-based regimens, clinicians need to be aware of important differences and distinctions between these agents. This is especially important for patients with multiple comorbidities and concomitant medications. Additional monitoring or medication dose adjustments may be needed when switching from one booster to another.