Pharmacokinetic parameters of once-daily rilpivirine following administration of efavirenz in healthy subjects

Physiologically-based pharmacokinetic modelling of long-acting injectable cabotegravir and rilpivirine in pregnancy

AIMS

Long-acting cabotegravir and rilpivirine have been approved to manage HIV in adults, but data regarding safe use in pregnancy are limited. Physiologically-based pharmacokinetic (PBPK) modelling was used to simulate the approved dosing regimens in pregnancy and explore if Ctrough was maintained above cabotegravir and rilpivirine target concentrations (664 and 50 ng/mL, respectively).

METHODS

An adult PBPK model was validated using clinical data of cabotegravir and rilpivirine in nonpregnant adults. This was modified by incorporating pregnancy-induced metabolic and physiological changes. The pregnancy PBPK model was validated with data on oral rilpivirine and raltegravir (UGT1A1 probe substrate) in pregnancy. Twelve weeks' disposition of monthly and bimonthly dosing of long-acting cabotegravir and rilpivirine was simulated at different trimesters and foetal exposure was also estimated.

RESULTS

Predicted Ctrough at week 12 for monthly long-acting cabotegravir was above 664 ng/mL throughout pregnancy, but below the target in 0.5% of the pregnant population in the third trimester with bimonthly long-acting cabotegravir. Predicted Ctrough at week 12 for monthly and bimonthly long-acting rilpivirine was below 50 ng/mL in at least 40% and over 90% of the pregnant population, respectively, throughout pregnancy. Predicted medians (range) of cord-to-maternal blood ratios were 1.71 (range, 1.55-1.79) for cabotegravir and 0.88 (0.78-0.93) for rilpivirine between weeks 38 and 40.

CONCLUSIONS

Model predictions suggest that monthly long-acting cabotegravir could maintain antiviral efficacy throughout pregnancy, but that bimonthly administration may require careful clinical evaluation. Both monthly and bimonthly long-acting rilpivirine may not adequately maintain antiviral efficacy in pregnancy.

Intramuscular cabotegravir and rilpivirine concentrations after switching from efavirenz-containing regimen

AIMS

Intramuscular cabotegravir/rilpivirine (IM CAB/RPV) are metabolized by UGT1A1/CYP3A4. Efavirenz induces both enzymes; therefore, switching from an efavirenz-containing regimen to IM CAB/RPV could possibly result in suboptimal levels. Due to their long dosing interval, clinical studies with IM CAB/RPV are challenging. We used physiologically based pharmacokinetics (PBPK) modelling to simulate the switch from efavirenz to IM CAB/RPV.

METHODS

First, we developed the drug models and verified the performance of the PBPK model to predict the pharmacokinetics of IM cabotegravir, IM rilpivirine and efavirenz by comparing the simulations against observed clinical data. Second, we verified the ability of the model to predict the effect of residual induction with observed data for the switch from efavirenz to dolutegravir or rilpivirine. Finally, we generated a cohort of 100 virtual individuals (20-50 years, 50% female, 18.5-30 kg/m2 ) to simulate IM CAB/RPV concentrations after discontinuing efavirenz in extensive and slow metabolizers of efavirenz.

RESULTS

IM CAB concentrations were predicted to decrease by 11% (95% confidence interval 7-15%), 13% (6-21%) and 8% (0-18%) at day 1, 7 and 14 after efavirenz discontinuation. CAB concentrations were predicted to remain above the minimal efficacy threshold (i.e., 664 ng/mL) throughout the switch period both in extensive and slow metabolizers of efavirenz. Similarly, IM RPV concentrations were modestly decreased with the lowest reduction being 10% (6-14%) on day 7 post last efavirenz dose.

CONCLUSION

Our simulations indicate that switching from an efavirenz-containing regimen to IM CAB/RPV does not put at risk of having a time window with suboptimal drug levels.

Pharmacokinetic and pharmacokinetic/pharmacodynamic characterization of the dolutegravir/rilpivirine two-drug regimen in SWORD-1/-2 phase 3 studies

AIM

SWORD-1 and SWORD-2 phase 3 studies concluded that switching virologically suppressed participants with HIV-1 from their current three- or four-drug antiretroviral regimen (CAR) to the two-drug regimen of once-daily dolutegravir (DTG, 50 mg) and rilpivirine (RPV, 25 mg) was safe, well tolerated and noninferior for maintaining HIV-1 suppression at week 48 and highly efficacious to week 148. A secondary objective was to characterize drug exposure and exposure-efficacy/safety relationships.

METHODS

Adults with plasma HIV-1 RNA <50 copies/mL were randomized to switch to once-daily DTG + RPV on day 1 or to continue CAR for 52 weeks before switching. Trough plasma concentrations (C0) of DTG and RPV, the proportion of participants with HIV-1 RNA <50 copies/mL and adverse events to week 100 were summarized and subjected to exposure-response analyses in the overall population, in the subset of participants who switched from CAR containing enzyme-inducing drugs and by age category (≥50 and <50 years). The relationship between C0avg (individual average C0 across visits) and efficacy/safety was investigated.

RESULTS

Although week 2 DTG and RPV C0 were lower in participants switching from enzyme-inducing antiretroviral drugs, C0 and C0avg stayed above in vitro antiviral protein binding-adjusted IC90 and to week 100 with viral suppression >89%. DTG or RPV C0avg showed no relationship with virologic failures or safety. Participants ≥50 years had similar C0avg and safety response to younger participants.

CONCLUSION

No clinically relevant relationship between DTG or RPV exposures and virologic or safety response was observed, confirming the DTG + RPV switch for participants as a safe and effective treatment.

Mechanistic Modeling of Maternal Lymphoid and Fetal Plasma Antiretroviral Exposure During the Third Trimester

Pregnancy-induced changes in plasma pharmacokinetics of many antiretrovirals (ARV) are well-established. Current knowledge about the extent of ARV exposure in lymphoid tissues of pregnant women and within the fetal compartment is limited due to their inaccessibility. Subtherapeutic ARV concentrations in HIV reservoirs like lymphoid tissues during pregnancy may constitute a barrier to adequate virological suppression and increase the risk of mother-to-child transmission (MTCT). The present study describes the pharmacokinetics of three ARVs (efavirenz, dolutegravir, and rilpivirine) in lymphoid tissues and fetal plasma during pregnancy using materno-fetal physiologically-based pharmacokinetic models (m-f-PBPK). Lymphatic and fetal compartments were integrated into our previously validated adult PBPK model. Physiological and drug disposition processes were described using ordinary differential equations. For each drug, virtual pregnant women (n = 50 per simulation) received the standard dose during the third trimester. Essential pharmacokinetic parameters, including Cmax, Cmin, and AUC (0-24), were computed from the concentration-time data at steady state for lymph and fetal plasma. Models were qualified by comparison of predictions with published clinical data, the acceptance threshold being an absolute average fold-error (AAFE) within 2.0. AAFE for all model predictions was within 1.08-1.99 for all three drugs. Maternal lymph concentration 24 h after dose exceeded the reported minimum effective concentration (MEC) for efavirenz (11,514 vs. 800 ng/ml) and rilpivirine (118.8 vs. 50 ng/ml), but was substantially lower for dolutegravir (16.96 vs. 300 ng/ml). In addition, predicted maternal lymph-to-plasma AUC ratios vary considerably (6.431-efavirenz, 0.016-dolutegravir, 1.717-rilpivirine). Furthermore, fetal plasma-to-maternal plasma AUC ratios were 0.59 for efavirenz, 0.78 for dolutegravir, and 0.57 for rilpivirine. Compared with rilpivirine (0 h), longer dose forgiveness was observed for dolutegravir in fetal plasma (42 h), and for efavirenz in maternal lymph (12 h). The predicted low lymphoid tissue penetration of dolutegravir appears to be significantly offset by its extended dose forgiveness and adequate fetal compartment exposure. Hence, it is unlikely to be a predictor of maternal virological failure or MTCT risks. Predictions from our m-f-PBPK models align with recommendations of no dose adjustment despite moderate changes in exposure during pregnancy for these drugs. This is an important new application of PBPK modeling to evaluate the adequacy of drug exposure in otherwise inaccessible compartments.

Pharmacokinetics of rilpivirine and 24-week outcomes after switching from efavirenz in virologically suppressed HIV-1-infected adolescents

BACKGROUND

Rilpivirine (RPV), a non-nucleoside reverse transcriptase inhibitor drug, could be a favourable drug for maintenance therapy in HIV-infected adolescents because it has few long-term side effects. However, data among adolescents switching from efavirenz (EFV) to RPV are limited. This study investigated the pharmacokinetics (PK), safety and efficacy of RPV in virologically suppressed HIV-1-infected adolescents after switching from EFV.

METHODS

Adolescents aged 12-18 years on EFV-based antiretroviral therapy (ART) were switched from EFV to RPV (25 mg, once daily). Intensive 24-h blood samplings at 0 (pre-dose), 1, 2, 4, 5, 6, 9, 12 and 24 h were performed 4 weeks after switching. PK parameters were calculated using a non-compartmental method and compared with published data from the PAINT and pooled ECHO/THRIVE substudies. HIV RNA level was measured at weeks 12 and 24. Biochemical profiles were measured at baseline and week 24.

RESULTS

From January to June 2016, 20 adolescents (12 male) were enrolled. Median (IQR) age was 16 (15-17) years and weight was 49 (42-59) kg. Mean (sd) AUC_{24 h}, C_{24 h} and C_max of RPV were 2,041 (745) ng•h/ml, 69 (29) ng/ml and 143 (65) ng/ml, respectively. Median (IQR) T_max was 5 (2-9) h. Four adolescents had C_{24 h} <40 ng/ml. All PK parameters were comparable with published data. All adolescents remained virologically suppressed at week 24. Significant decreases in fasting total cholesterol, triglyceride and low-density lipoprotein were observed (P-value <0.05).

CONCLUSIONS

Virologically suppressed HIV-infected adolescents had adequate RPV exposure and remained virologically suppressed after switching from EFV. RPV can be used as long-term maintenance ART in HIV-infected adolescents.

Doravirine and the Potential for CYP3A-Mediated Drug-Drug Interactions

Identifying and understanding potential drug-drug interactions (DDIs) are vital for the treatment of human immunodeficiency virus type 1 (HIV-1) infection. This article discusses DDIs between doravirine, a nonnucleoside reverse transcriptase inhibitor (NNRTI), and cytochrome P450 3A (CYP3A) substrates and drugs that modulate CYP3A activity. Consistent with previously published in vitro data and DDI trials with the CYP3A substrates midazolam and atorvastatin, doravirine did not have any meaningful impact on the pharmacokinetics of the CYP3A substrates ethinyl estradiol and levonorgestrel. Coadministration of doravirine with CYP3A inhibitors (ritonavir or ketoconazole) increased doravirine exposure approximately 3-fold. However, these increases were not considered clinically meaningful. Conversely, previously published trials showed that coadministered CYP3A inducers (rifampin and rifabutin) decreased doravirine exposure by 88% and 50%, respectively (K. L. Yee, S. G. Khalilieh, R. I. Sanchez, R. Liu, et al., Clin Drug Investig 37:659-667, 2017 [https://doi.org/10.1007/s40261-017-0513-4]; S. G. Khalilieh, K. L. Yee, R. I. Sanchez, R. Liu, et al., J Clin Pharmacol 58:1044-1052, 2018 [https://doi.org/10.1002/jcph.1103]), while doravirine exposure following prior efavirenz administration led to an initial reduction in doravirine exposure of 62%, but the reduction became less pronounced with time (K. L. Yee, R. I. Sanchez, P. Auger, R. Liu, et al., Antimicrob Agents Chemother 61:e01757-16, 2017 [https://doi.org/10.1128/AAC.01757-16]). Overall, the coadministration of doravirine with CYP3A inhibitors and substrates is, therefore, supported by these data together with efficacy and safety data from clinical trials, while coadministration with strong CYP3A inducers, such as rifampin, cannot be recommended. Concomitant dosing with rifabutin (a CYP3A inducer less potent than rifampin) is acceptable if doravirine dosing is adjusted from once to twice daily; however, the effect of other moderate inducers on doravirine pharmacokinetics is unknown.

Dolutegravir/rilpivirine for the treatment of HIV-1 infection

Much progress has been made in the development of antiretroviral therapies (ARTs) for HIV-1 infection. Beginning a little over a decade ago, single tablet combination regimens (STRs) became available, and subsequently, newer STR formulations with improved safety profiles have emerged. Recently, there is a growing interest in regimen simplification with the primary goal of further reducing long-term toxicities of ART and improving medication adherence. Dolutegravir/rilpivirine (DTG/RPV) was approved by the US Food and Drug Administration (FDA) as the first dual antiretroviral STR for the maintenance therapy of HIV-1 infection. Following an extensive review of all published papers on RPV and DTG, administered alone and in combination, extracted from databases including PubMed, Google scholar, and EMBASE, as well as drug package inserts and conference abstracts and proceedings, this review discusses the chemical properties and composition, pharmacodynamics and pharmacokinetic properties, clinical trial efficacy and safety data, as well as important drug-drug interactions associated with DTG/RPV. An expert opinion section discusses ideal candidates for DTG/RPV in the context of available but limited data and in comparison to currently available and emerging ART alternatives.

Pharmacokinetics of Co-Formulated Elvitegravir/Cobicistat/Emtricitabine/Tenofovir Disoproxil Fumarate After Switch From Efavirenz/Emtricitabine/Tenofovir Disoproxil Fumarate in Healthy Subjects

BACKGROUND

Elvitegravir (EVG), a HIV integrase inhibitor, is metabolized primarily by CYP3A, and secondarily by UGT1A1/3; Efavirenz (EFV), a HIV non-nucleoside reverse transcriptase inhibitor, is metabolized by Cytochrome P450 (CYP) 2B6 and induces CYP3A and uridine diphosphate glucuronosyltransferase (UGT) with residual effects post discontinuation because of long T1/2 (40-55 hours). This study evaluated the pharmacokinetics after switching from efavirenz/emtricitabine/tenofovir disoproxil fumarate (EFV/FTC/TDF) to elvitegravir/cobicistat/emtricitabine/tenofovir disoproxil fumarate (EVG/COBI/FTC/TDF).

METHODS

Healthy subjects (n = 32 including n = 8 CYP2B6 poor metabolizers) received EVG/COBI/FTC/TDF (150/150/200/300 mg) on days 1-7, and after a washout, received EFV/FTC/TDF (600/200/300 mg) on days 15-28 and switched to EVG/COBI/FTC/TDF (150/150/200/300 mg) for 5 weeks (days 29-62). Pharmacokinetic assessments occurred on days 7, 28, 35, and 42; trough samples (Ctrough) were collected periodically until day 63. Safety was assessed throughout the study.

RESULTS

Twenty-nine subjects completed with 3 adverse events leading to discontinuation; no grade ≥3 adverse events were reported. Post-EFV/FTC/TDF, mean EVG area under concentration (AUCtau) was 37% and 29% lower and mean Ctrough ∼3- and ∼5-fold above IC95, respectively, on days 35 and 42, and 7-8-fold above IC95 by 5 weeks. COBI AUCtau returned to normal by day 42. EVG glucuronide, GS-9200, AUCtau was higher (46% and 32% on days 35 and 42, respectively) postswitch. CYP2B6 poor metabolizers displayed higher EFV AUCtau and Cmax (125% and 91%, respectively) versus non-poor metabolizers, and lower EVG and COBI exposures. EFV Ctrough was >IC90 (10 ng/mL) in all subjects postswitch. FTC and tenofovir (TFV) exposures were unaffected.

CONCLUSIONS

After EFV/FTC/TDF to EVG/COBI/FTC/TDF switch, EVG and/or EFV exposures were in an active range. These findings support further evaluation of switching regimens in HIV-1 patients.

Evaluation of Doravirine Pharmacokinetics When Switching from Efavirenz to Doravirine in Healthy Subjects

Doravirine is a novel, potent nonnucleoside reverse transcriptase inhibitor (NNRTI) for the treatment of patients with human immunodeficiency virus type 1 (HIV-1) infection that demonstrates a high genetic barrier to resistance and that has been well tolerated in studies to date. Doravirine is a candidate for patients switching from less-well-tolerated NNRTIs, such as efavirenz. While doravirine is a cytochrome P450 3A4 (CYP3A4) substrate, efavirenz induces CYP3A4; therefore, the pharmacokinetics of both drugs following a switch from efavirenz to doravirine were assessed. This was a 3-period, fixed-sequence, open-label study. Healthy adults were dosed with doravirine at 100 mg for 5 days once daily (QD) (period 1). Following a 7-day washout, efavirenz was administered at 600 mg QD for 14 days (period 2). Subsequently, doravirine was administered at 100 mg QD for 14 days (period 3). Blood samples were collected for pharmacokinetic analyses. Twenty healthy subjects were enrolled, and 17 completed the study. One day after efavirenz cessation, the doravirine area under the concentration-time curve from predosing to 24 h postdosing (AUC_0-24), maximum observed plasma concentration (C_max), and observed plasma concentration at 24 h postdosing (C₂₄) were reduced by 62%, 35%, and 85%, respectively, compared with the values with no efavirenz pretreatment. These decreases recovered to 32%, 14%, and 50% for AUC_0-24, C_max, and C₂₄, respectively, by day 14 after efavirenz cessation. The doravirine C₂₄ reached projected therapeutic trough concentrations, based on in vitro efficacy, on day 2 following efavirenz cessation. Geometric mean efavirenz concentrations were 3,180 ng/ml on day 1 and 95.7 ng/ml on day 15, and efavirenz was present at therapeutic concentrations (>1,000 ng/ml) until day 4. Though doravirine exposure was transiently decreased following efavirenz treatment cessation, dose adjustment may not be necessary to maintain therapeutic concentrations of at least one drug during switching in a virologically suppressed population.

Optimizing the virological success of tenofovir DF/FTC/rilpivirine in HIV-infected naive and virologically suppressed patients through strict clinical and virological selection

BACKGROUND

Tenofovir DF/FTC/rilpivirine (TDF/FTC/RPV) is a single tablet regimen considered as safe and efficacious in HIV population as long as food requirements, concomitant PPI administration, and compromised antiviral activity have been carefully reviewed. We evaluated TDF/FTC/RPV in a real-life setting with focus on clinical and virological outcomes.

METHODS

OCEAN II is a prospective, two-centre observational study. From September 2012 to December 2013, antiretroviral-naive patients with HIV RNA <100,000 copies/mL or wishing to switch for simplification were considered for TDF/FTC/RPV. A systematic review of potential obstacles to TDF/FTC/RPV administration was undertaken during a multidisciplinary meeting, including DNA genotyping to detect archived RPV and/or NRTI-associated resistance mutations if historical RNA resistance testing was lacking.

RESULTS

TDF/FTC/RPV was considered for 480 patients, however was not offered to 194 patients (40%), mainly because of risk of insufficient virological efficacy, issues on adherence, patient refusal, meal constraint, or PPI therapy. A total of 286 patients (269 in maintenance; 17 ART-naive) received TDF/FTC/RPV. After a median follow-up of 30 months, virological failure occurred in five patients (1.7%) without the emergence of resistance mutations. Discontinuation of TDF/FTC/RPV occurred in 98 patients, due to adverse events in 43 patients (44%) and non-safety reasons in 55 patients (56%). No grade three-fourth adverse events occurred.

CONCLUSION

In this real-life experience, cohort consisting primarily of virologically suppressed patients, TDF/FTC/RPV usually maintained virologic suppression. Discontinuation of therapy because of intolerability was due to mild adverse events. Strict clinical and virological screening probably explained the low rate of virological failure.

Pharmacokinetics of Rilpivirine in HIV-Infected Pregnant Women

BACKGROUND

Rilpivirine pharmacokinetics is defined by its absorption, distribution, metabolism, and excretion. Pregnancy can affect these factors by changes in cardiac output, protein binding, volume of distribution, and cytochrome P450 (CYP) 3A4 activity. Rilpivirine is metabolized by CYP3A4. The impact of pregnancy on rilpivirine pharmacokinetics is largely unknown.

METHODS

International Maternal Pediatric Adolescent AIDS Clinical Trials P1026s is a multicenter, nonblinded, prospective study evaluating antiretroviral pharmacokinetics in HIV-infected pregnant women that included a cohort receiving rilpivirine 25 mg once daily as part of their combination antiretrovirals for clinical care. Thirty-two women were enrolled in this study. Intensive pharmacokinetic sampling was performed at steady state during the second trimester, the third trimester, and postpartum. Maternal and umbilical cord blood samples were obtained at delivery. Plasma rilpivirine concentration was measured using liquid chromatography-mass spectrometry; lower limit of quantitation was 10 ng/mL.

RESULTS

Median (range) AUC0-24 were 1969 (867-4987, n = 15), 1669 (556-4312, n = 28), and 2387 (188-6736, n = 28) ng·h/mL in the second trimester, the third trimester, and postpartum, respectively (P < 0.05 for either trimester vs postpartum). Median (range) C24 were 63 (37-225, n = 17), 56 (<10-181, n = 30), and 81 (<10-299, n = 28) ng/mL (P < 0.05 for either trimester vs postpartum). High variability in pharmacokinetic parameters was observed between subjects. Median (range) cord blood/maternal concentration ratio was 0.55 (0.3-0.8, n = 21). Delivery HIV-1 RNA was ≤50 copies per milliliter in 70% and ≤400 copies per milliliter in 90% of women. Cmin were significantly lower at 15 visits with detectable HIV-1 RNA compared with 61 visits with undetectable HIV-1 RNA, 29 (<10-93) vs 63 (15-200) ng/mL (P = 0.0001). Cmin was below the protein binding-adjusted EC90 concentration (12.2 ng/mL) at 4 visits in 3 of 31 women (10%).

CONCLUSIONS

Rilpivirine exposure is lower during pregnancy compared with postpartum and highly variable. Ninety percent of women had minimum concentrations above the protein binding-adjusted EC90 for rilpivirine.

Pharmacokinetic interaction between etravirine or rilpivirine and telaprevir in healthy volunteers: A randomized, two-way crossover trial

Coinfection with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) may require treatment with an HIV non-nucleoside reverse transcriptase inhibitor (NNRTI), for example, rilpivirine or etravirine, and an HCV direct-acting antiviral drug such as telaprevir. In a two-panel, two-way, crossover study, healthy volunteers were randomized to receive etravirine 200 mg twice daily ± telaprevir 750 mg every 8 hours or rilpivirine 25 mg once daily ± telaprevir 750 mg every 8 hours. Pharmacokinetic assessments were conducted for each drug at steady-state when given alone and when coadministered; statistical analyses were least-square means with 90% confidence intervals. Telaprevir minimum plasma concentration (Cmin), maximum plasma concentration (Cmax), and area under the concentration-time curve (AUC) decreased 25%, 10%, and 16%, respectively, when coadministered with etravirine and 11%, 3%, and 5%, respectively, when coadministered with rilpivirine. Telaprevir did not affect etravirine pharmacokinetics, but increased rilpivirine Cmin, Cmax, and AUC by 93%, 49%, and 78%, respectively. Both combinations were generally well tolerated. The small decrease in telaprevir exposure when coadministered with etravirine is unlikely to be clinically relevant. The interaction between telaprevir and rilpivirine is not likely to be clinically relevant under most circumstances. No dose adjustments are deemed necessary when they are coadministered.

Efficacy and safety in clinical practice of a rilpivirine, tenofovir and emtricitabine single-tablet regimen in virologically suppressed HIV-positive patients on stable antiretroviral therapy

INTRODUCTION

Switching to a rilpivirine, tenofovir and emtricitabine (RTE) single-tablet regimen (STR) has been evaluated in a limited number of virologically suppressed patients. The aim of this study was to describe clinical outcomes in HIV-positive patients switched from a suppressive antiretroviral regimen to RTE STR in routine clinical practice.

METHODS

In this retrospective study of antiretroviral-treated patients with <50 copies of HIV RNA/mL switched to RTE STR, virological failure (VF) was defined as two consecutive measurements of ≥50 copies/mL or a single measurement of ≥50 copies/mL followed by any change in treatment. Treatment failure (TF) was defined as VF or discontinuation of the STR for any reason. Univariate mixed-linear models were used to identify differences in laboratory parameters over time.

RESULTS AND DISCUSSION

The analysis involved 307 patients (83% males) with a median age of 45.8 years (interquartile range (IQR 39.3-50.9), who were followed up for a median of 7.4 months (IQR 4.6-10.9). VF occurred in three patients (1%) switched from a protease inhibitor (PI)-based regimen, after a median of 2.6 months (IQR 1.6-3.0), and TF in 34 patients (11%) after a median of three months (IQR 1.4-5.8), 24 of whom (71%) were receiving a PI-based regimen at baseline. Overall, there was a slight but statistically significant improvement in the mean monthly change from baseline in CD4+ cell counts (p=0.027), the CD4+/CD8+ ratio (p=0.0001), and Hb (p=0.024), alanine amino transferase (ALT) (p=0.009), total bilirubin (p<0.0001), indirect bilirubin (p<0.0001), total cholesterol (p<0.0001) and triglyceride (p<0.0001) levels. There was also a slight but statistically significant increase in serum creatinine (p=0.0004), aspartate amino transferase (AST) (p=0.001) and liver fibrosis index (FIB-4) (p=0.002), and a decrease in eGFRcreat (p<0.0001) and high-density lipoprotein (HDL) cholesterol (p<0.0001) values. The study limitations include its retrospective design, the relatively short follow-up, and the absence of data concerning the severity of clinical adverse events; however, it does provide new information concerning the laboratory changes that occur in patients switching from PI-based or PI-sparing regimens to RTE STR.

CONCLUSIONS

The study findings confirm the efficacy and safety in clinical practice of switching to RTE STR in virologically suppressed patients receiving other antiretrovirals.

The efficacy, pharmacokinetics, and safety of a nevirapine to rilpivirine switch in virologically suppressed HIV-1-infected patients

: This prospective, open-label nonrandomized controlled trial evaluated the efficacy, safety, and pharmacokinetics of substituting nevirapine/emtricitabine/tenofovir for rilpivirine/emtricitabine/tenofovir in 50 suppressed HIV-1 switchers. One hundred thirty-nine nonswitchers remained on nevirapine as controls. Week 12 HIV-1 RNA was <50 copies per milliliter in 92.0% of switchers and was <50 copies per milliliter at week 24 in 88.0% of switchers and 90.6% of nonswitchers (difference 2.6%, 95% confidence interval: -7.6% to 12.8%). Week 3 geometric mean nevirapine concentration was undetectable and week 1 geometric mean rilpivirine concentration (0.083 mg/L) was comparable with phase 3 trial (P = 0.747). Substituting nevirapine for rilpivirine resulted in ongoing virological suppression and did not have clinically relevant pharmacokinetic effects by cytochrome P450 interactions.

HIV therapy-the state of art

HIV Attachment. In this cross section, HIV is shown at the top and a target cell is shown at the bottom in blues. HIV envelope protein (A) has bound to the receptor CD4 (B) and then to coreceptor CCR5 (C), causing a change in conformation that inserts fusion peptides into the cellular membrane Antiretroviral therapy changed the face of HIV/AIDS from that of soon and certain death to that of a chronic disease in the years following introduction of highly active antiretroviral therapy in 1995-1996 (initially termed HAART, but now most often abbreviated to ART since not all combinations of regimens are equally active). Since then, many new agents have been developed and introduced in response to problems of resistance, toxicity, and tolerability, and great advances have been achieved in accessibility of HIV drugs in resource-poor global regions. Potential challenges that providers of HIV therapy will face in the coming decade include continuing problems with resistance, especially where access to drugs is inconsistent, determining how best to combine new and existing agents, defining the role of preventive treatment (pre-exposure prophylaxis or PrEP), and evaluating the potential of strategies for cure in some populations.

Switching safely: pharmacokinetics, efficacy and safety of switching efavirenz to maraviroc twice daily in patients on suppressive antiretroviral therapy

BACKGROUND

CYP3A4 induction by efavirenz (EFV) persists after drug cessation; we assessed the pharmacokinetics (PK), efficacy and safety of maraviroc (MVC) administered to HIV-infected individuals switching from EFV-containing therapy.

METHODS

Patients with R5-tropic virus and suppressed viral load on two nucleoside/nucleotide reverse transcriptase inhibitors (NRTIs) plus EFV switched EFV to MVC 600 mg twice daily for 14 days, and then to MVC 300 mg twice daily. Following screening, three intensive PK visits were performed (sampling was pre-dose and 1, 2, 4, 6, 8 and 12 h post-dose): day 1 (VISIT 1, MVC 600 mg twice daily), day 14 (VISIT 2, steady-state MVC 600 mg twice daily) and day 28 post regimen switch (VISIT 3, steady-state MVC 300 mg twice daily); MVC trough concentration (Ctrough) was determined 3, 6 and 10 days following regimen switch and viral loads up to week 24. MVC PK parameters on visits 1 and 2 and MVC Ctrough on day 6 were compared to visit 3 (reference) via geometric mean ratios (GMR) and 95% CIs.

RESULTS

Twelve males completed the study. MVC PK parameters at visit 1 versus visit 3 were: GMR and 95% CI 12-h area under the curve (AUC0-12) 1.25 (1.00, 1.58); Cmax 1.64 (1.16, 2.31); Ctrough 0.61 (0.46, 0.80). Visit 2 MVC PK parameters were significantly higher than visit 3: GMR and 95% CI AUC0-12 2.31 (1.84, 2.90); Cmax 2.42 (1.87, 3.12); Ctrough 2.25 (1.74, 2.91). MVC was well tolerated with no grade 3/4 adverse events; all subjects maintained viral suppression to the end of the study.

CONCLUSIONS

The EFV induction effect necessitated increased MVC dose to 600 mg twice daily following switch and persisted for approximately one week after EFV cessation. This is less than the 2-week induction observed when switching EFV to etravirine and highlights the importance of studying different tail interactions. Higher dose MVC was well tolerated. All measured MVC Ctrough concentrations exceeded wild-type 90% inhibitory concentration.

Rilpivirine exposure in plasma and sanctuary site compartments after switching from nevirapine-containing combined antiretroviral therapy

OBJECTIVES

Pharmacokinetic parameters following modifications to antiretroviral therapy and sanctuary site exposure are often unknown for recently licensed antiretrovirals. We assessed plasma, CSF and seminal plasma (SP) exposure of rilpivirine after switching from nevirapine.

METHODS

HIV-infected male subjects receiving tenofovir/emtricitabine/nevirapine (245/200/400 mg) once daily switched to tenofovir/emtricitabine/rilpivirine (245/200/25 mg) once daily for 60 days when CSF and semen samples were collected. Mean and individual plasma concentrations of nevirapine and rilpivirine were compared with the proposed plasma target concentration for nevirapine (3000 ng/mL) and the protein binding-adjusted EC90 for rilpivirine (12.1 ng/mL). Mean rilpivirine CSF and SP concentrations were calculated and individual values compared with the EC50 and EC90 for wild-type virus (0.27 and 0.66 ng/mL, respectively).

RESULTS

Of 13 subjects completing study procedures including CSF examination, 8 provided seminal samples. By day 3, the mean plasma rilpivirine trough concentration was 29.7 ng/mL (95% CI: 23.8-37). No patient presented rilpivirine plasma concentrations under the proposed threshold. The mean rilpivirine concentration in CSF was 0.8 ng/mL (95% CI: 0.7-1.0), representing a CSF : plasma ratio of 1.4%, with concentrations above the EC90 in 85% (11/13) of patients. In SP, the mean rilpivirine concentration was 4.9 ng/mL (95% CI: 3.3-7.2), representing an SP : plasma ratio of 9.5%, with all concentrations above the EC90.

CONCLUSIONS

Switching from nevirapine- to rilpivirine-containing antiretroviral therapy was safe and well tolerated, with plasma rilpivirine concentrations above the protein binding-adjusted EC90 in all subjects. Rilpivirine concentrations were always above the EC50 in the CSF and the EC90 in SP.

Review of drug interactions with telaprevir and antiretrovirals

HCV infection is a major cause of mortality worldwide. HCV-related deaths also represent a leading cause of mortality in HIV-coinfected individuals. Telaprevir is an NS3/4A protease inhibitor approved for the treatment of chronic HCV genotype 1 infection in adults in combination with pegylated interferon and ribavirin. Telaprevir-based treatment has been shown to increase rates of sustained viral response in HCV genotype-1-monoinfected patients, and studies in HCV-HIV-coinfected patients are ongoing. Drug-drug interactions of telaprevir with antiretroviral drugs were investigated in a series of studies in healthy subjects. This review summarizes the results of interaction studies with low-dose ritonavir, ritonavir-boosted HIV protease inhibitors (atazanavir, darunavir, fosamprenavir and lopinavir), efavirenz, etravirine, rilpivirine, tenofovir disoproxil fumarate and raltegravir.

Rilpivirine, a novel non-nucleoside reverse transcriptase inhibitor for the management of HIV-1 infection: a systematic review

Rilpivirine (RPV) is a second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI). It remains active against HIV strains harbouring mutations that affect first-generation agents. RPV is dosed once daily with food and has been coformulated into a single tablet containing tenofovir and emtricitabine. Two Phase III studies of treatment-naive patients found RPV and efavirenz to have similar safety and efficacy. However, suboptimal virological suppression with RPV occurred more commonly in patients with higher baseline viral loads (>100,000 copies/ml). The most common mutation that emerged during RPV therapy was E138K, which often occurred in combination with M184I. E138K is likely to cause cross-resistance to other NNRTIs thereby limiting the further utilization of this class.

Antiviral drug advances in the treatment of human immunodeficiency virus (HIV) and chronic hepatitis C virus (HCV)

Antiviral therapy is recommended for all HIV infected individuals. Therefore, there is a continuous need for improvement and optimization of current therapy and the development of novel agents and drug classes. Fixed dose combinations (FDC) with the advantage of once daily dosing and improved tolerability and toxicity profiles are attractive options. The non-nucleoside reverse transcriptase inhibitor (NNRTI) based FDC of rilpivirine plus tenofovir disoproxil fumarate (TDF) and emtricitabine (FTC) (Complera(®)) and an extended release version of the NNRTI nevirapine, (Viramune XR(®)) were recent additions to the HIV armamentarium. In addition, the approval of the second integrase inhibitor, elvitegravir, and a novel pharmacoenhancer cobicistat is anticipated in 2012. These agents have been co-formulated with TDF and FTC as a single tablet and represent the first integrase inhibitor based complete FDC regimen. A new standard of care for the treatment of Chronic Hepatitis C (HCV) emerged in 2011 with the approval of the first antiviral drugs to directly inhibit HCV NS3/4A protease, telaprevir (Incivik(®)) and boceprevir (Victrelis(®)). Combined with peginterferon-alfa plus ribavirin they offer genotype-1 infected patients significantly improved sustained virologic response rates and the potential for shorter durations of therapy. HCV therapeutics will continue to evolve as there are several drugs in the protease inhibitor class and other classes such as NS5B polymerase inhibitors, NS5A inhibitors and cyclophilin inhibitors currently in development.

Effects of rilpivirine on human adipocyte differentiation, gene expression, and release of adipokines and cytokines

Rilpivirine is a nonnucleoside reverse transcriptase inhibitor (NNRTI) recently developed as a drug of choice for initial antiretroviral treatment of HIV-1 infection. Disturbances in lipid metabolism and, ultimately, in adipose tissue distribution and function are common concerns as secondary effects of antiretroviral treatment. Efavirenz, the most commonly used NNRTI, causes mild dyslipidemic effects in patients and strongly impaired adipocyte differentiation in vitro. In this study, we provide the first demonstration of the effects of rilpivirine on human adipocyte differentiation, gene expression, and release of regulatory proteins (adipokines and cytokines) and compare them with those caused by efavirenz. Rilpivirine caused a repression of adipocyte differentiation that was associated with impaired expression of the master adipogenesis regulators peroxisome proliferator-activated receptor gamma (PPARγ), CCAAT enhancer binding protein alpha (C/EBPα), and sterol regulatory element binding transcription factor 1 (SREBP-1) and their target genes encoding lipoprotein lipase and the adipokines leptin and adiponectin. Rilpivirine also repressed adiponectin release by adipocytes, but only at high concentrations, and did not alter leptin release. Rilpivirine induced the release of proinflammatory cytokines (interleukin-6 and -8, monocyte chemoattractant protein 1 [MCP-1], plasminogen activator inhibitor type 1 [PAI-1]) only at very high concentrations (10 μM). A comparison of the effects of rilpivirine and efavirenz at the same concentration (4 μM) or even at lower concentrations of efavirenz (2 μM) showed that rilpivirine-induced impairment of adipogenesis and induction of proinflammatory cytokine expression and release were systematically milder than those of efavirenz. It is concluded that rilpivirine causes an antiadipogenic and proinflammatory response pattern, but only at high concentrations, whereas efavirenz causes similar effects at lower concentrations.