Pharmacokinetics of darunavir/cobicistat and etravirine alone and co-administered in HIV-infected patients

Pharmacokinetic and toxicological considerations affecting antiretroviral drug dosing in pregnant women

INTRODUCTION

To prevent mother-to-child transmission (PMTCT) of the human immunodeficiency virus (HIV) during pregnancy, the appropriate dosing regimens of antiretroviral (ARV) drugs need to be determined. Reliable data about pharmacokinetic (PK) characteristics of ARVs from randomized clinical trials (RCTs) are lacking, and post-marketing observational studies may offer valuable, but sometimes insufficient data, especially in pregnant people living with HIV (PLWHIV). This review article is focused PK and toxicological considerations affecting ARV dosing in pregnant PLWHIV.

AREAS COVERED

In our search, we included studies focused on PKs of ARVs in pregnancy available on PubMed, abstracts from recent global conferences and data from modeling studies. There are no significant changes in PKs of nucleoside/nucleotide reverse transcriptase inhibitors and non-nucleoside reverse transcriptase inhibitors throughout pregnancy. In contrast, the PKs of PIs and INSTIs are more variable, especially in the second and third trimesters.

EXPERT OPINION

Pregnant women are left out of RCTs. To the greatest extent possible, future research should include pregnant persons in RCTs, including PK studies, strictly considering maternal and fetal safety. Alternative innovative approaches/models need to be developed to obtain reliable data about rational pharmacotherapy of ARVs in the effective PMTCT of HIV, with maximum safety.

Pharmacokinetics and tolerability of the maturation inhibitor GSK3640254 coadministered with darunavir/ritonavir and/or etravirine in healthy adults

AIMS

This phase I study investigated potential drug-drug interactions of the maturation inhibitor GSK3640254 (GSK'254) with darunavir/ritonavir (DRV/RTV) and/or etravirine (ETR).

METHODS

In this randomized, open-label, single-sequence, multiple-dose study, healthy participants received GSK'254 200 mg once daily alone or coadministered with DRV/RTV 600/100 mg twice daily (BID; n = 19), ETR 200 mg BID (n = 19) or DRV/RTV 600/100 mg + ETR 200 mg BID (n = 16) under fed conditions. Primary endpoints were steady-state area under the plasma concentration-time curve from time 0 to the end of the dosing interval (AUC0-τ ) and maximum observed concentration (Cmax ). Secondary endpoints included trough concentration (Cτ ), safety and tolerability. Pharmacokinetic parameters were calculated using standard noncompartmental analysis, and geometric least-squares mean ratios were derived from linear mixed-effects models.

RESULTS

GSK'254 AUC0-τ (geometric least-squares mean ratio [90% confidence interval], 1.14 [1.00-1.29]), Cmax (1.07 [0.92-1.24]) and Cτ (1.17 [1.01-1.35]) were similar when administered alone and with DRV/RTV. Etravirine coadministration decreased GSK'254 AUC0-τ (0.53 [0.48-0.59]), Cmax (0.60 [0.53-0.68]) and Cτ (0.51 [0.39-0.66]). Similar reductions were not observed with GSK'254 + DRV/RTV + ETR (AUC0-τ , 0.94 [0.82-1.09]; Cmax , 0.89 [0.75-1.07]; Cτ , 1.02 [0.89-1.18]). GSK'254 had no meaningful effect on DRV/RTV or ETR concentrations. All reported adverse events (AEs) were grade 1; 3 led to withdrawal and resolved (rash, asymptomatic electrocardiogram T-wave inversion, periorbital oedema). Most common AEs were diarrhoea (n = 9) and headache (n = 7). No deaths or serious AEs occurred.

CONCLUSION

GSK'254 pharmacokinetics was not meaningfully affected by DRV/RTV or DRV/RTV + ETR, but were reduced with only ETR; no new tolerability concerns were observed.

Magnitude of Drug–Drug Interactions in Special Populations

Drug–drug interactions (DDIs) are one of the most frequent causes of adverse drug reactions or loss of treatment efficacy. The risk of DDIs increases with polypharmacy and is therefore of particular concern in individuals likely to present comorbidities (i.e., elderly or obese individuals). These special populations, and the population of pregnant women, are characterized by physiological changes that can impact drug pharmacokinetics and consequently the magnitude of DDIs. This review compiles existing DDI studies in elderly, obese, and pregnant populations that include a control group without the condition of interest. The impact of physiological changes on the magnitude of DDIs was then analyzed by comparing the exposure of a medication in presence and absence of an interacting drug for the special population relative to the control population. Aging does not alter the magnitude of DDIs as the related physiological changes impact the victim and perpetrator drugs to a similar extent, regardless of their elimination pathway. Conversely, the magnitude of DDIs can be changed in obese individuals or pregnant women, as these conditions impact drugs to different extents depending on their metabolic pathway.

Clinical Pharmacokinetics and Pharmacodynamics of Etravirine: An Updated Review

Etravirine is a second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) for the treatment of human immunodeficiency virus type 1 infection. It is a potent inhibitor of HIV reverse transcriptase and retains activity against wild-type and most NNRTI-resistant HIV. The pharmacokinetic profile of etravirine and clinical data support twice-daily dosing, although once-daily dosing has been investigated in treatment-naïve and treatment-experienced persons. Despite similar pharmacokinetic and pharmacodynamic results compared with twice-daily dosing, larger studies are needed to fully support once-daily etravirine dosing in treatment-naïve individuals. Etravirine is reserved for use in third- or fourth-line antiretroviral treatment regimens, as recommended, for example, in treatment guidelines by the US Department of Health and Human Services-Guidelines for the Use of Antiretroviral Agents in Adults and Adolescents Living with HIV. Etravirine exhibits the potential for bi-directional drug-drug interactions with other antiretrovirals and concomitant medications through its interactions with cytochrome P450 (CYP) isozymes: CYP3A4, CYP2C9, and CYP2C19. This review summarizes the pharmacokinetic and pharmacodynamic parameters of etravirine, with particular attention to information on drug-drug interactions and use in special patient populations, including children/adolescents, women, persons with organ dysfunction, and during pregnancy.

Effectiveness of Switching to Darunavir/Cobicistat in Virologically Suppressed HIV-Positive Patients Receiving Ritonavir-Boosted Protease Inhibitor-Based Regimen: The "STORE" Study

OBJECTIVE

This study investigates the effectiveness and tolerability of switching to a darunavir/cobicistat (DRV/c)-based antiretroviral regimen from a ritonavir-boosted protease inhibitor (PI/r)-based regimen in virologically suppressed HIV-positive patients. DRV trough values were also investigated.

SETTING

Prospective, multicenter, single-country, noninterventional cohort study.

METHODS

This study included patients on a PI/r-based ART for at least 12 months having plasma HIV-1 RNA <50 copies/mL since at least 6 months. The primary endpoint, defined as HIV-1 RNA <50 copies/mL, was measured at 48 ± 6 weeks from baseline. A secondary analysis was performed using the time to loss of virological response algorithm. Biochemical parameters, including DRV trough samples, were collected as per clinical practice and measured using high-performance liquid chromatography.

RESULTS

Of 336 patients enrolled, 282 completed the study: 70.8% had plasma HIV-1 RNA <50 copies/mL at 48 weeks; using the time to loss of virological response algorithm, 82.7% maintained virological suppression. Virological failure was observed in 6 patients (1.8%). Adverse event-related discontinuations were 4.5%. After 48 weeks, we found a significant improvement in both triglycerides (median, 130 to 113.5 mg/dL, P = 0.0254) and high-density lipoprotein cholesterol (48 to 49 mg/dL, P < 0.0001) but no change in other biomarkers. DRV trough concentrations in 56 subjects showed a median value of 2862.5 (1469.5-4439) ng/mL, higher in women than in men (4221 vs. 2634 ng/mL, P = 0.046).

CONCLUSIONS

In stable HIV-1 positive virologically suppressed patients, the switch to DRV/c-based ART was beneficial in terms of low rates of virological failure and adverse events due to its high tolerability and improvement in triglycerides.

Drug-Drug Interactions with Antiretroviral Drugs in Pregnant Women Living with HIV: Are They Different from Non-Pregnant Individuals?

Background and Objective

Although the separate effects of drug–drug interactions and pregnancy on antiretroviral drug pharmacokinetics have been widely studied and described, their combined effect is largely unknown. Physiological changes during pregnancy may change the extent or clinical relevance of a drug–drug interaction in a pregnant woman. This review aims to provide a detailed overview of the mechanisms, magnitude, and clinical significance of antiretroviral drug–drug interactions in pregnant women.

Methods

We performed a literature search and selected studies that compared the magnitude of drug–drug interactions with antiretroviral drugs in pregnant vs non-pregnant women.

Results

Forty-eight papers examining drug–drug interactions during pregnancy were selected, of which the majority focused on pharmacokinetic boosting. Other selected studies examined the drug–drug interactions between efavirenz and lumefantrine, efavirenz and tuberculosis drugs, etravirine and tenofovir disoproxil fumarate, atazanavir and tenofovir disoproxil, and mefloquine and nevirapine in pregnant compared to non-pregnant women. The clinical significance of antiretroviral drug–drug interactions changed during pregnancy from a minimal effect to a contra-indication. In almost all cases, the clinical significance of a drug–drug interaction was more relevant in pregnant women, owing to the combined effects of pregnancy-induced physiological changes and drug–drug interactions leading to a lower absolute drug exposure.

Conclusions

Multiple studies show that the clinical relevance of a drug–drug interaction can change during pregnancy. Unfortunately, many potential interactions have not been studied in pregnancy, which may place pregnant women living with human immunodeficiency virus and their newborns at risk.

Optimizing concentrations of concomitant antiretrovirals by reducing etravirine doses: two case reports of complex drug-drug interactions

We report the cases of two treatment-experienced HIV-infected patients with complex antiretroviral regimens that showed significant drug-drug interactions with etravirine. Unexpectedly high etravirine concentrations likely caused subtherapeutic levels of darunavir, elvitegravir and dolutegravir through concentration-dependent metabolic induction. Therapeutic drug monitoring allowed safe etravirine dose decreases to manage these interactions.

Pharmacokinetics, Placental and Breast Milk Transfer of Antiretroviral Drugs in Pregnant and Lactating Women Living with HIV

BACKGROUND

Remarkable progress has been achieved in the identification of HIV infection in pregnant women and in the prevention of vertical HIV transmission through maternal antiretroviral treatment (ART) and neonatal antiretroviral drug (ARV) prophylaxis in the last two decades. Millions of women globally are receiving combination ART throughout pregnancy and breastfeeding, periods associated with significant biological and physiological changes affecting the pharmacokinetics (PK) and pharmacodynamics (PD) of ARVs. The objective of this review was to summarize currently available knowledge on the PK of ARVs during pregnancy and transport of maternal ARVs through the placenta and into the breast milk. We also summarized main safety considerations for in utero and breast milk ARVs exposures in infants.

METHODS

We conducted a review of the pharmacological profiles of ARVs in pregnancy and during breastfeeding obtained from published clinical studies. Selected maternal PK studies used a relatively rich sampling approach at each ante- and postnatal sampling time point. For placental and breast milk transport of ARVs, we selected the studies that provided ratios of maternal to the cord (M:C) plasma and breast milk to maternal plasma (M:P) concentrations, respectively.

RESULTS

We provide an overview of the physiological changes during pregnancy and their effect on the PK parameters of ARVs by drug class in pregnancy, which were gathered from 45 published studies. The PK changes during pregnancy affect the dosing of several protease inhibitors during pregnancy and limit the use of several ARVs, including three single tablet regimens with integrase inhibitors or protease inhibitors co-formulated with cobicistat due to suboptimal exposures. We further analysed the currently available data on the mechanism of the transport of ARVs from maternal plasma across the placenta and into the breast milk and summarized the effect of pregnancy on placental and of breastfeeding on mammal gland drug transporters, as well as physicochemical properties, C:M and M:P ratios of individual ARVs by drug class. Finally, we discussed the major safety issues of fetal and infant exposure to maternal ARVs.

CONCLUSIONS

Available pharmacological data provide evidence that physiological changes during pregnancy affect maternal, and consequently, fetal ARV exposure. Limited available data suggest that the expression of drug transporters may vary throughout pregnancy and breastfeeding thereby possibly impacting the amount of ARV crossing the placenta and secreted into the breast milk. The drug transporter's role in the fetal/child exposure to maternal ARVs needs to be better understood. Our analysis underscores the need for more pharmacological studies with innovative study design, sparse PK sampling, improved study data reporting and PK modelling in pregnant and breastfeeding women living with HIV to optimize their treatment choices and maternal and child health outcomes.

Ambrisentan use in a HIV-1 infected patient with end-stage renal disease and pulmonary hypertension: minimal removal by hemodialysis - a case report

BACKGROUND

Ambrisentan is a selective endothelin receptor antagonist used for the treatment of pulmonary arterial hypertension (PAH). Little is known about ambrisentan removal by hemodialysis in patients with end-stage renal disease (ESRD).

CASE PRESENTATION

A 53-year-old woman with HIV/hepatitis C virus (HCV) co-infection, PAH and ESRD on regular hemodialyis was admitted in our hospital due to refractory heart failure while on treatment with bosentan (125 mg twice daily) and tadalafil (20 mg once daily) for PAH and antiretroviral treatment (cART) including darunavir/cobicistat (800/150 mg once daily). Excessive exposure to bosentan due to drug interactions between bosentan and darunavir/cobicistat was suspected. Bosentan was replaced by ambrisentan, with progressive improvement in her clinical condition. Pre- and postdialyzer cocentrations of ambrisentan in plasma were determined and hemodialysis extraction ratio for ambrisentan was 2%.

CONCLUSIONS

Our results suggest that hemodialysis results in minimal ambrisentan removal, and therefore no specific ambrisentan dosage adjustment seems to be required in ESRD patients undergoing hemodialysis.

Pharmacokinetic drug evaluation of ritonavir (versus cobicistat) as adjunctive therapy in the treatment of HIV

Introduction: Ritonavir and cobicistat are pharmacoenhancers used to improve the disposition of other HIV antiretrovirals. These drugs are, however, characterized by important pharmacokinetic differences.Areas covered: Here, the authors firstly update the available information on the pharmacokinetics of ritonavir and cobicistat. Subsequently, the review focuses on the description of drug-drug interactions (DDIs) involving cobicistat and comedications that might beneficiate from a shift-back to ritonavir. A MEDLINE Pubmed search for articles published from January 1995 to April 2019 was completed matching the term ritonavir or cobicistat with pharmacokinetics, DDIs, and pharmacology. Moreover, additional studies were identified from the reference list of retrieved articles.Expert opinion: Despite more than 20 years after its introduction on the market, ritonavir still represents a valid option for the treatment of selected HIV-infected patients. The large-scale switch to cobicistat may result in some unexpected DDIs not previously reported for ritonavir. Besides the issue of DDIs, additional advantage of ritonavir over cobicistat is its use in pregnancy, and its availability as single component of pharmaceutical formulations allowing the fine-tuning of antiretroviral regimens in patients with heavy polypharmacy when other unboosted-based therapeutic options cannot be used.

Efficacy of single-tablet darunavir, cobicistat, emtricitabine, and tenofovir alafenamide in the treatment of HIV-1

INTRODUCTION

HIV eradication is not feasible and lifelong treatment is warranted to manage HIV infection. In this scenario, the advent of single-tablet, once-daily, fixed-dose co-formulations is important for reducing pill burden and maximize long-term drug adherence. Cobicistat-boosted darunavir along with emtricitabine and tenofovir alafenamide co-formulation (DRV/c/FTC/TAF or the trade name Symtuza®) is the first marketed protease inhibitor-based fixed-dose combination regimen for the treatment of HIV infection. It was approved in late 2017 by the European Medical Agency both for naïve patients and treatment-experienced patients with viral suppression. Areas covered: PubMed, ClinicalTrials.gov and presentations at scientific meetings were searched with the terms 'darunavir/cobicistat' and 'tenofovir alafenamide and emtricitabine' for clinical trials either conducted to date or ongoing as well as a review of abstracts from major HIV/AIDS and infectious diseases conferences from 2015 to up to date. Expert opinion: DRV/c/FTC/TAF is a novel unique antiretroviral drug co-formulation that exhibits a convenient dosing, satisfactory safety profile, and high antiviral efficacy, even in patients harboring viruses with resistance to antivirals other than darunavir in the short-midterm. It represents the first fixed-dose combination therapy including a protease inhibitor given as one single pill once daily for drug-naïve patients and as second-line antiretroviral therapy.