Pharmacokinetics and safety of twice-daily atazanavir 300 mg and raltegravir 400 mg in healthy individuals

Applied physiologically-based pharmacokinetic modeling to assess uridine diphosphate-glucuronosyltransferase-mediated drug-drug interactions for Vericiguat

Vericiguat (Verquvo; US: Merck, other countries: Bayer) is a novel drug for the treatment of chronic heart failure. Preclinical studies have demonstrated that the primary route of metabolism for vericiguat is glucuronidation, mainly catalyzed by uridine diphosphate-glucuronosyltransferase (UGT)1A9 and to a lesser extent UGT1A1. Whereas a drug-drug interaction (DDI) study of the UGT1A9 inhibitor mefenamic acid showed a 20% exposure increase, the effect of UGT1A1 inhibitors has not been assessed clinically. This modeling study describes a physiologically-based pharmacokinetic (PBPK) approach to complement the clinical DDI liability assessment and support prescription labeling. A PBPK model of vericiguat was developed based on in vitro and clinical data, verified against data from the mefenamic acid DDI study, and applied to assess the UGT1A1 DDI liability by running an in silico DDI study with the UGT1A1 inhibitor atazanavir. A minor effect with an area under the plasma concentration-time curve (AUC) ratio of 1.12 and a peak plasma concentration ratio of 1.04 was predicted, which indicates that there is no clinically relevant DDI interaction anticipated. Additionally, the effect of potential genetic polymorphisms of UGT1A1 and UGT1A9 was evaluated, which showed that an average modest increase of up to 1.7-fold in AUC may be expected in the case of concomitantly reduced UGT1A1 and UGT1A9 activity for subpopulations expressing non-wild-type variants for both isoforms. This study is a first cornerstone to qualify the PK-Sim platform for use of UGT-mediated DDI predictions, including PBPK models of perpetrators, such as mefenamic acid and atazanavir, and sensitive UGT substrates, such as dapagliflozin and raltegravir.

Drug-drug interactions that alter the exposure of glucuronidated drugs: Scope, UDP-glucuronosyltransferase (UGT) enzyme selectivity, mechanisms (inhibition and induction), and clinical significance

Drug-drug interactions (DDIs) arising from the perturbation of drug metabolising enzyme activities represent both a clinical problem and a potential economic loss for the pharmaceutical industry. DDIs involving glucuronidated drugs have historically attracted little attention and there is a perception that interactions are of minor clinical relevance. This review critically examines the scope and aetiology of DDIs that result in altered exposure of glucuronidated drugs. Interaction mechanisms, namely inhibition and induction of UDP-glucuronosyltransferase (UGT) enzymes and the potential interplay with drug transporters, are reviewed in detail, as is the clinical significance of known DDIs. Altered victim drug exposure arising from modulation of UGT enzyme activities is relatively common and, notably, the incidence and importance of UGT induction as a DDI mechanism is greater than generally believed. Numerous DDIs are clinically relevant, resulting in either loss of efficacy or an increased risk of adverse effects, necessitating dose individualisation. Several generalisations relating to the likelihood of DDIs can be drawn from the known substrate and inhibitor selectivities of UGT enzymes, highlighting the importance of comprehensive reaction phenotyping studies at an early stage of drug development. Further, rigorous assessment of the DDI liability of new chemical entities that undergo glucuronidation to a significant extent has been recommended recently by regulatory guidance. Although evidence-based approaches exist for the in vitro characterisation of UGT enzyme inhibition and induction, the availability of drugs considered appropriate for use as 'probe' substrates in clinical DDI studies is limited and this should be research priority.

Drug-Drug Interaction Studies to Evaluate the Effect of Inhibition of UGT1A1 and CYP3A4 and Induction of CYP3A4 on the Pharmacokinetics of Tropifexor in Healthy Subjects

Tropifexor, a farnesoid X receptor agonist, is currently under clinical development for the treatment of nonalcoholic steatohepatitis. Tropifexor undergoes glucuronidation by uridine 5'-diphosphoglucuronosyltransferase (UGT) 1A1 and oxidation by cytochrome P450 (CYP) 3A4, as reported in in vitro studies. Here, we report the results from 2 drug-drug interaction studies. Study 1 enrolled 20 healthy subjects to investigate the effect of the UGT1A1 inhibitor atazanavir (ATZ) on tropifexor pharmacokinetics (PK). Study 2 had 2 cohorts with 16 healthy subjects each to investigate the effect of the strong CYP3A4 inhibitor itraconazole and strong CYP3A4 inducer rifampin on the PK of tropifexor. Coadministration of ATZ reduced the maximum plasma concentration (C_max ) of tropifexor by 40%; however, it did not lead to increased exposure of tropifexor (both area under the plasma concentration-time curve [AUC] from time 0 to the last quantifiable concentration [AUC_last ] and AUC from time 0 to infinity [AUC_inf ] reduced by only 10%), suggesting minor relevance of the UGT1A1 pathway for clearance of tropifexor and no expected drug-drug interactions based on UGT1A1 inhibition. Inhibition of CYP3A4 by itraconazole increased the C_max of tropifexor by only 9% and exposure (both AUC_last and AUC_inf ) by 47%, suggesting a weak effect of strong CYP3A4 inhibitors on tropifexor PK. Inducing CYP3A4 with rifampin decreased C_max (55%) and AUC (AUC_last by 79% and AUC_inf by 77%). Coadministration of tropifexor with either ATZ, itraconazole, or rifampin was well tolerated.

Pharmacokinetic drug interactions of integrase strand transfer inhibitors

The integrase strand transfer inhibitor (INSTI)-containing regimens are currently considered as the first-line treatment of human immunodeficiency virus (HIV) infection. Although possessing a common mechanism of action to inhibit HIV integrase irreversibly to stop HIV replication cycle, the INSTIs, including raltegravir, elvitegravir, dolutegravir, and bictegravir, differ in pharmacokinetic characteristics. While raltegravir undergoes biotransformation by the UDP-glucuronosyltransferases (UGTs), elvitegravir is primarily metabolized by cytochrome P450 (CYP) 3A4 and co-formulated with cobicistat to increase its plasma exposure. The metabolism pathways of dolutegravir and bictegravir are similar, both including CYP3A and UGT1A1, and both agents are substrates to different drug transporters. Because of their differences in metabolism, INSTIs interact with other medications differently through CYP enzymes and transporters as inducers or inhibitors. These drug interactions may become an important consideration in the long-term clinical use because the life expectancy of people with HIV (PWH) approaches to that of the general population. Also, common geriatric challenges such as multimorbidity and polypharmacy have been increasingly recognized in PWH. This review provides a summary of pharmacokinetic interactions with INSTIs and future perspectives in implications of INSTI drug interactions.

PBPK Modeling as a Tool for Predicting and Understanding Intestinal Metabolism of Uridine 5'-Diphospho-glucuronosyltransferase Substrates

Uridine 5′-diphospho-glucuronosyltransferases (UGTs) are expressed in the small intestines, but prediction of first-pass extraction from the related metabolism is not well studied. This work assesses physiologically based pharmacokinetic (PBPK) modeling as a tool for predicting intestinal metabolism due to UGTs in the human gastrointestinal tract. Available data for intestinal UGT expression levels and in vitro approaches that can be used to predict intestinal metabolism of UGT substrates are reviewed. Human PBPK models for UGT substrates with varying extents of UGT-mediated intestinal metabolism (lorazepam, oxazepam, naloxone, zidovudine, cabotegravir, raltegravir, and dolutegravir) have demonstrated utility for predicting the extent of intestinal metabolism. Drug–drug interactions (DDIs) of UGT1A1 substrates dolutegravir and raltegravir with UGT1A1 inhibitor atazanavir have been simulated, and the role of intestinal metabolism in these clinical DDIs examined. Utility of an in silico tool for predicting substrate specificity for UGTs is discussed. Improved in vitro tools to study metabolism for UGT compounds, such as coculture models for low clearance compounds and better understanding of optimal conditions for in vitro studies, may provide an opportunity for improved in vitro–in vivo extrapolation (IVIVE) and prospective predictions. PBPK modeling shows promise as a useful tool for predicting intestinal metabolism for UGT substrates.

How Science Is Driving Regulatory Guidances

This chapter provides regulatory perspectives on how to translate in vitro drug metabolism findings into in vivo drug-drug interaction (DDI) predictions and how this affects the decision of conducting in vivo DDI evaluation. The chapter delineates rationale and analyses that have supported the recommendations in the U.S. Food and Drug Administration (FDA) DDI guidances in terms of in vitro-in vivo extrapolation of cytochrome P450 (CYP) inhibition-mediated DDI potential for investigational new drugs and their metabolites as substrates or inhibitors. The chapter also describes the framework and considerations to assess UDP-glucuronosyltransferase (UGT) inhibition-mediated DDI potential for drugs as substrates or inhibitors. The limitations of decision criteria and further improvements needed are also discussed. Case examples are provided throughout the chapter to illustrate how decision criteria have been utilized to evaluate in vivo DDI potential from in vitro data.

Recent Advancement in Nanotechnology-Based Drug Delivery System Against Viral Infections

In the last few decades, the exponential rise in the incidence of viral infections sets a global health emergency across the world. The biomimetic architecture, the ability to hijack host immune responses, continuous antigen shifting, and drafting are the major critical factors that are responsible for the unavailability of a concrete therapeutic regimen against viral infections. Further, inappropriate pharmacodynamic physicochemical and biological parameters such as low aqueous solubility, poor permeability, high affinity for plasm proteins, short biological half-lives, and fast elimination from the systemic circulation are the major critical factors that govern the suboptimal drug concentration at the target site that leads to the development of drug resistance. To address this issue, nanotechnology-based drug delivery approach is emerged as an altering method to attain the optimal drug concentration at the target site for a prolonged period by integrating the nanoengineering tools in the synthesis of nanoparticles. Nanodimensional configuration with enhanced permeability and retention effect, increased surface-area-to-volume ratio, provision for surface functionalization, etc., are the privileged aspects that make it an effective drug delivery system for dispensing the antiviral therapeutics. However, size, shape, charge, and surface topology of nanoparticles are the greater influential factors that determine target-specific drug delivery, optimum cellular uptake, degree of opsonization by the host immune cells, drug retention time, transcytosis, the extension of biological half-life, in vivo stability, and cytotoxicity. The review will enlighten the elaborative role of nanotechnology-based drug delivery and the major challenging aspect of clinical safety and efficacy.

Decreased darunavir concentrations during once-daily co-administration with maraviroc and raltegravir: OPTIPRIM-ANRS 147 trial

Background

The OPTIPRIM-ANRS 147 trial compared intensive combination ART (darunavir/ritonavir, tenofovir disoproxil fumarate/emtricitabine, raltegravir and maraviroc) started early during primary HIV-1 infection with standard tritherapy with darunavir/ritonavir, tenofovir disoproxil fumarate and emtricitabine. From month 6 to 18, the percentage of viral load values <50 copies/mL was lower in the pentatherapy arm than in the tritherapy arm. Here we compared antiretroviral drug concentrations between the two arms.

Methods

Plasma samples were collected from 50 patients at various times after drug administration. A Bayesian approach based on published population pharmacokinetic models was used to estimate residual drug concentrations (Ctrough) and exposures (AUC) in each patient. A mixed linear regression model was then used to compare the AUC and Ctrough values of each drug used in both groups.

Results

Published models adequately described our data and could be used to predict Ctrough and AUC. No significant difference in tenofovir disoproxil fumarate, emtricitabine and ritonavir parameters was found between the two arms. However, darunavir Ctrough and AUC were significantly lower in the pentatherapy arm than in the tritherapy arm (P = 0.03 and P = 0.04, respectively).

Conclusions

Adding maraviroc and raltegravir to darunavir-based tritherapy decreased darunavir concentrations. Compliance issues, maraviroc-darunavir interaction and raltegravir-darunavir interaction were suspected and may affect the kinetics of viral decay during pentatherapy. A specific pharmacokinetic interaction study is needed to explore the interactions between darunavir and maraviroc and raltegravir.

Efficacy, safety and pharmacokinetics of atazanavir (200mg twice daily) plus raltegravir (400mg twice daily) dual regimen in the clinical setting

BACKGROUND

Unboosted atazanavir with raltegravir has been investigated at 300mg twice daily showing frequent hyperbilirubinemia and selection of resistance-associated mutations.

OBJECTIVES

Atazanavir 200mg twice daily could increase tolerability and plasma exposure.

STUDY DESIGN

Patients on atazanavir/raltegravir (200/400 twice daily), with self-reported adherence >95% and no concomitant interacting drugs were retrospectively evaluated.

RESULTS

102 patients [72.5% male, age 46.4 years (42-54), BMI 24kg/m² (22-26)] were included. CD4+ T lymphocytes were 417 cell/μL (302-704) and 76 patients (74.5%) had HIV-RNA <50 copies/ml. After 123 weeks 18.6% patients showed virological failure and 3.9% discontinued for intolerance. Available genotypes showed selection of major integrase (7/10 patients) and protease resistance-associated mutations (5/13 patients). In patients switching with dyslipidemia (n=67) total, LDL cholesterol and triglycerides significantly decreased. Patients switching with eCRCL<60ml/min (n=27) had no significant changes while patients with eCRCL >60ml/min showed significant decrease (-9.8ml/min, p=0.003) at 96-weeks. Atazanavir and raltegravir trough concentrations were 321ng/mL (147-720) and 412ng/mL (225-695). Self-reported non-adherence (n=4) was significantly associated with virological failure (p=0.02); patients with virological success had borderline longer previous virological control (33 vs. 18 months, p=0.07).

DISCUSSION

Switch to atazanavir/raltegravir was safe and well tolerated allowing optimal drugs' plasma exposure. However, a concerning rate (18.6%) failed with newly selected mutations and stopped ATV/RAL because of DDI and intolerance issues or were lost to follow-up. This regimen might be considered in selected patients, without history of protease inhibitors failure or HBV infection, showing optimal adherence and prolonged suppression.

Switch to Ritonavir-Boosted versus Unboosted Atazanavir plus Raltegravir Dual-Drug Therapy Leads to Similar Efficacy and Safety Outcomes in Clinical Practice

Objectives

To assess immunovirological response, safety and pharmacokinetic of NRTI-sparing regimen dual therapy of atazanavir (ATV) and raltegravir (RAL) in maintenance strategy.

Methods

A retrospective analysis was conducted on a cohort of HIV-infected adults followed in French centers (Dat’AIDS cohort), comparing the proportions of virological and therapeutic failures between ATV + RAL and ATV/ritonavir + RAL dual therapy regimens.

Results

283 patients were assessed: 185 switched for ATV + RAL and 98 for ATV/ritonavir + RAL dual therapy. Virological failure rate at week 96 was 13.8% (95% CI, 9.8–17.8), without difference between the two groups (Log-rank Test, p = 0.87). The cumulative percentages of patients remaining free of therapeutic failure at week 24, 48 and 96 of dual therapy were 74.9% (95% CI, 69.9–80.0), 65.4% (95% CI, 59.8–70.9) and 53.4% (95% CI, 47.5–59.2), respectively. Four out of 39 confirmed virological failures developed RAL resistance. By multivariate analysis, virological failure was associated with high HIV-1 RNA zenith (p = 0.02), low CD4+ T-cell count at baseline (p<0.001) and short duration on antiretroviral therapy (p<0.001). Before week 96, dual therapy was discontinued in 44 patients (16%) because of various adverse events, with no difference between the two groups. Minimal plasma levels were targeted in 84% and 87% of patients for ATV and RAL, respectively, and both were significantly higher in ritonavir-boosted regimen.

Conclusions

Emerging RAL-resistance and discontinuations for adverse events resulted in moderate efficacy rates of ATV and RAL dual therapy in heavily pretreated patients.

Muscle symptoms and creatine phosphokinase elevations in patients receiving raltegravir in clinical practice: Results from the SCOLTA project long-term surveillance

Muscle alterations ranging from asymptomatic creatine phosphokinase (CPK) increases to rhabdomyolysis and central nervous system (CNS) symptoms have been reported in patients receiving raltegravir. Muscle symptoms and CPK increases were investigated in a cohort of HIV-infected patients receiving raltegravir-based antiretroviral therapy, and possible associated predictors were evaluated. The SCOLTA Project is a prospective, observational, multicentre study created to assess the incidence of adverse events in patients receiving new antiretroviral drugs in clinical practice. In total, 496 HIV-infected patients were enrolled [333 (67.1%) male]. CDC stage was C in 196 patients (39.5%). Mean age at enrolment was 45.9 ± 9.3 years. Median follow-up was 21 months. Twenty-six patients (5.2%) reported muscle symptoms (16 muscle pain and 17 weakness; 7 had both). Of 342 patients with normal baseline CPK values, 72 (21.1%) had a CPK increase. Seven patients (1.4%) discontinued raltegravir because of muscular events (three for muscle pain/weakness and four CPK increases). No cases of rhabdomyolysis were observed. Patients with muscle symptoms were more frequently receiving in their regimen than those not receiving atazanavir (P=0.04) and were more likely to also report CNS symptoms (P<0.0001). Significant predictors of muscle symptoms were CNS symptoms and use of atazanavir. Female sex was associated with a reduced risk of CPK increase. In conclusion, muscle symptoms and CPK elevations occurred frequently and caused most discontinuations due to adverse events. Their monitoring in patients receiving raltegravir should be considered, especially when co-administered with atazanavir or when CNS symptoms are also present.

Efficacy and safety of switching to raltegravir plus atazanavir dual therapy in pretreated HIV-1-infected patients over 144 weeks: a cohort study

BACKGROUND

To decrease drug burden among HIV-1-positive adults, we need a new gold standard for antiretroviral therapy maintenance strategies.

METHODS

This retrospective study aimed to assess efficacy in maintenance strategy of atazanavir (ATV) and raltegravir (RAL) dual therapy. The proportion of patients with HIV-1 RNA < 40 copies/ml at specific time points was recorded. Immunological response, safety, and pharmacokinetics were assessed.

RESULTS

Overall, 39 patients were switched to a RAL/ATV (n = 32) or RAL/ATV plus ritonavir (n = 7) regimen. Almost all patients (95%) received RAL twice daily. Most patients (70%) received a 400 mg ATV dosing per day, once (26%) or twice daily (44%). The percentages of virological success at weeks 24, 48, 96, and 144 were 92% (95% confidence interval (CI), 83-10), 86% (95% CI, 74-98), 70% (95% CI, 52-88), and 63% (95% CI, 42-84), respectively. Overall, 12 (31%) patients stopped dual therapy: 7 patients because of adverse events, mostly clinical myositis (n = 3). Confirmed virological failure occurred in three patients; two of them developed RAL resistance patterns. A significant increase in the CD4+/CD8 + T-cell ratio was observed at week 48 (p < 0.005). Only grade 1-2 adverse events were observed. Trough plasma levels presented a wide variability. Suggested trough concentrations were achieved in 79% and 94% of patients for ATV and RAL, respectively. An unboosted 400 mg per day ATV dosing seemed to be appropriate, regarding the targeted levels achieved and the lack of grade 3 or 4 hyperbilirubinemia.

CONCLUSIONS

We demonstrated, on a 3-year follow-up, the efficacy and safety of RAL plus ATV maintenance dual therapy.

HIV protease inhibitors disrupt lipid metabolism by activating endoplasmic reticulum stress and inhibiting autophagy activity in adipocytes

BACKGROUND

HIV protease inhibitors (PI) are core components of Highly Active Antiretroviral Therapy (HAART), the most effective treatment for HIV infection currently available. However, HIV PIs have now been linked to lipodystrophy and dyslipidemia, which are major risk factors for cardiovascular disease and metabolic syndrome. Our previous studies have shown that HIV PIs activate endoplasmic reticulum (ER) stress and disrupt lipid metabolism in hepatocytes and macrophages. Yet, little is known on how HIV PIs disrupt lipid metabolism in adipocytes, a major cell type involved in the pathogenesis of metabolic syndrome.

METHODOLOGY AND PRINCIPAL FINDINGS

Cultured and primary mouse adipocytes and human adipocytes were used to examine the effect of frequently used HIV PIs in the clinic, lopinavir/ritonavir, on adipocyte differentiation and further identify the underlying molecular mechanism of HIV PI-induced dysregulation of lipid metabolism in adipocytes. The results indicated that lopinavir alone or in combination with ritonavir, significantly activated the ER stress response, inhibited cell differentiation, and induced cell apoptosis in adipocytes. In addition, HIV PI-induced ER stress was closely linked to inhibition of autophagy activity. We also identified through the use of primary adipocytes of CHOP(-/-) mice that CHOP, the major transcriptional factor of the ER stress signaling pathway, is involved in lopinavir/ritonavir-induced inhibition of cell differentiation in adipocytes. In addition, lopinavir/ritonavir-induced ER stress appears to be associated with inhibition of autophagy activity in adipocytes.

CONCLUSION AND SIGNIFICANCE

Activation of ER stress and impairment of autophagy activity are involved in HIV PI-induced dysregulation of lipid metabolism in adipocytes. The key components of ER stress and autophagy signaling pathways are potential therapeutic targets for HIV PI-induced metabolic side effects in HIV patients.

Unboosted atazanavir for treatment of HIV infection: rationale and recommendations for use

Atazanavir (Reyataz®) is a protease inhibitor (PI) for the treatment of HIV infection. Several trials have demonstrated the good efficacy and toxicity profile of atazanavir boosted by ritonavir (atazanavir/r). However, several toxicity events and pharmacokinetic issues due to drug-to-drug interactions (partly related to ritonavir) may complicate atazanavir/r therapy. This is why regimens with unboosted atazanavir have been experimented with and are used in clinical practice. The aim of this article is to identify the clinical settings in which unboosted atazanavir may be a safe and effective option for the long-term control of HIV replication. Despite the fact that a favourable lipid profile and good gastrointestinal tolerability have been reported in comparative trials, unboosted atazanavir should not be considered an optimal choice for treatment-naive patients. In fact, boosting with ritonavir produces higher atazanavir plasma levels, which are beneficial in terms of efficacy, especially in untreated patients with high plasma HIV RNA. Clinical data indicate that, in patients with sustained undetectable HIV RNA and without previous virological failure or HIV drug resistance-associated mutations, a switch to unboosted atazanavir-based regimens is a feasible option to control and prevent toxicity events, especially in patients who cannot tolerate ritonavir and in those with severe hyperbilirubinaemia on atazanavir/r. Moreover, while unboosted atazanavir must not be used in pregnant women, it is a recommended option in special populations, such as patients with moderate liver insufficiency. Lastly, unboosted atazanavir in combination with raltegravir may allow the construction of a well tolerated and effective regimen without nucleoside reverse transcriptase inhibitors in patients for whom these drugs are contraindicated. In conclusion, there is a good rationale, significant clinical interest and accumulating clinical experience with unboosted atazanavir-based regimens, although this formulation should be used only in specific situations and as a maintenance strategy. Moreover, therapeutic drug monitoring could be useful in specific circumstances (such as in patients with liver impairment or in case of potential drug-drug interactions).

Lack of a clinically significant drug-drug interaction in healthy volunteers between the hepatitis C virus protease inhibitor boceprevir and the HIV integrase inhibitor raltegravir

BACKGROUND

Patients coinfected with human immunodeficiency virus (HIV) and hepatitis C virus (HCV) are likely to use both HIV and HCV treatment. Drug-drug interactions have been demonstrated between boceprevir, an HCV protease inhibitor, and frequently prescribed antiretroviral drugs, such as efavirenz and boosted HIV protease inhibitors. Concomitant administration of boceprevir with these drugs should be avoided. This study was designed to investigate the absence of a drug-drug interaction between boceprevir and raltegravir, an HIV integrase inhibitor.

METHODS

This was an open-label, randomized, 2-period, crossover phase 1 trial in 24 healthy volunteers. All subjects were randomly assigned to receive boceprevir 800 mg every 8 hours for 9 days plus a single dose of raltegravir 400 mg on day 10 followed by a washout period and a single dose of raltegravir 400 mg on day 38, or the same medication in reverse order. Blood samples for pharmacokinetics were collected and pharmacokinetic parameters were calculated.

RESULTS

The geometric mean (GM) of raltegravir area under the concentration-time curve (AUC)(0-12h) and maximum plasma concentration (C(max)) for raltegravir + boceprevir vs raltegravir alone were 4.27 (95% confidence interval [CI], 3.22-5.66) vs 4.04 (95% CI, 3.09-5.28) mg * hour/L and 1.06 (95% CI, .76-1.49) vs 0.93 (95% CI, .70-1.23) mg/L, respectively. GM ratio estimates of raltegravir AUC(0-12h) and C(max) for raltegravir + boceprevir vs raltegravir alone were 1.04 (90% CI, .88-1.22) and 1.11 (90% CI, .91-1.36), respectively. The GM of boceprevir AUC(0-8h), C(max), and C(8h) were 5.45 (95% CI, 5.11-5.81) mg * hour/L, 1.88 (95% CI, 1.72-2.06) mg/L, and 0.09 (95% CI, .07-.11) mg/L, respectively. These data are comparable to those from historical controls.

CONCLUSIONS

Due to the absence of a clinically significant drug interaction, raltegravir can be recommended for combined HIV/HCV treatment including boceprevir.

CLINICAL TRIALS REGISTRATION

NCT01288417.

Update on raltegravir and the development of new integrase strand transfer inhibitors

Raltegravir (RAL) is the first antiretroviral in the integrase strand transfer inhibitors (INSTI) class. The use of RAL has expanded since its approval in October 2007 for multidrug-resistant human immunodeficiency virus type 1 infection in adults. RAL is now a guideline-preferred treatment option for antiretroviral-naïve patients, indicated for treatment in adolescents, and is being studied as an integral part of nucleoside sparing regimens. The development of resistance and the need for a once-daily dosing option has led to the development of new INSTIs, including elvitegravir and dolutegravir. Elvitegravir is being studied in a promising once-daily single-tablet regimen with tenofovir, emtricitabine, and the investigational pharmacoenhancer cobicistat. The development of cobicistat and the new once-daily INSTIs may revolutionize the treatment of human immunodeficiency virus type 1 infection. This article reviews the current literature on raltegravir and new developments in the INSTI class.

Population pharmacokinetic analysis and pharmacogenetics of raltegravir in HIV-positive and healthy individuals

The objectives of this study were to characterize raltegravir (RAL) population pharmacokinetics in HIV-positive (HIV(+)) and healthy individuals, identify influential factors, and search for new candidate genes involved in UDP glucuronosyltransferase (UGT)-mediated glucuronidation. The pharmacokinetic analysis was performed with NONMEM. Genetic association analysis was performed with PLINK using the relative bioavailability as the phenotype. Simulations were performed to compare once- and twice-daily regimens. A 2-compartment model with first-order absorption adequately described the data. Atazanavir, gender, and bilirubin levels influenced RAL relative bioavailability, which was 30% lower in HIV(+) than in healthy individuals. UGT1A9*3 was the only genetic variant possibly influencing RAL pharmacokinetics. The majority of RAL pharmacokinetic variability remains unexplained by genetic and nongenetic factors. Owing to the very large variability, trough drug levels might be very low under the standard dosing regimen, raising the question of a potential relevance of therapeutic drug monitoring of RAL in some situations.

Acceptable plasma concentrations of raltegravir and etravirine when administered by gastrostomy tube in a patient with advanced multidrug-resistant human immunodeficiency virus infection

STUDY OBJECTIVE

To determine whether the absorption of four antiretroviral agents-raltegravir, etravirine, emtricitabine, and tenofovir-is compromised when administered by gastrostomy tube.

DESIGN

Pharmacokinetic analysis.

SETTING

University medical center.

PATIENT

A 52-year-old African-American man coinfected with advanced multidrug-resistant human immunodeficiency virus (HIV) and chronic hepatitis B, who was receiving treatment with raltegravir, etravirine, emtricitabine, and tenofovir, and developed ulcerative esophagitis with perforation, requiring a gastrostomy tube.

MEASUREMENTS AND MAIN RESULTS

Due to the patient's esophageal perforations, all nutrition and drug therapy had to be provided by gastrostomy tube. As his antiretroviral regimen of raltegravir, etravirine, and emtricitabine-tenofovir was not available in liquid or powder formulations, the oral tablets were crushed or dispersed and mixed with water, then administered by gastrostomy tube. To ensure that the absorption of the drugs was sufficient for antiretroviral response, plasma samples were collected at 2 hours and 12 hours after dosing, and drug concentrations were quantitated by using validated assays. The 2- and 12-hour postdose plasma concentrations were 1220 and 446 ng/ml for raltegravir, 212 and 274 ng/ml for etravirine, 1148 and 164 ng/ml for emtricitabine, and 320 and 94 ng/ml for tenofovir, respectively. The patient's plasma concentrations were then compared with those in published pharmacokinetic studies of oral regimens administered to HIV-infected persons and healthy volunteers. Overall, the plasma concentrations of the antiretrovirals administered by gastrostomy tube were similar to published values. No drug toxicities were observed in this patient.

CONCLUSION

These pharmacokinetic data suggest that absorption of raltegravir, etravirine, emtricitabine, and tenofovir was not compromised when the drugs were administered by gastrostomy tube. These findings provide a basis for further investigation of the pharmacokinetics, safety, tolerance, and antiretroviral response to raltegravir, etravirine, and emtricitabine-tenofovir when the oral route of administration is not possible.

Adherence and preexisting major protease inhibitor resistance mutations are associated with virologic failure of a dual-class antiretroviral regimen with inhibitors of HIV-1 viral protease and integrase

OBJECTIVES

Novel treatment strategies are needed for treatment-experienced HIV-infected individuals. We retrospectively evaluated virologic outcomes on a dual-class, protease inhibitor (PI) plus raltegravir, antiretroviral (ARV) regimen.

METHODS

Virologic success was defined by a plasma HIV-RNA level ≤200 copies/mL. Adherence was measured using pharmacy refill data. The association between adherence and virologic failure was assessed using bivariate logistic regression.

RESULTS

In 39 individuals, median prior antiretroviral therapy (ART) exposure was 11 years. Of 39 individuals, 36 (92%) achieved an HIV-RNA ≤200 copies/mL. After a median follow-up of 328 days (interquartile range [IQR] 190-737 days), 74% maintained an HIV-RNA <200 copies/mL but only 44% had <50 copies/mL. Median adherence was 96.4% (IQR 83.3%-100%). For every 10% decrease in adherence, the odds of virologic failure increased by 90% (odds ratio [OR] = 1.9, 95% confidence interval [CI] 1.1-3.3). In all, 4 individuals had ≥2 preexisting major PI resistance mutations and all 4 had virologic failure.

CONCLUSIONS

Most treatment-experienced individuals achieved virologic suppression on a dual-class regimen of a PI plus raltegravir. Success was limited by poor medication adherence and preexisting major PI resistance mutations.

Raltegravir and unboosted atazanavir dual therapy in virologically suppressed antiretroviral treatment-experienced HIV patients

BACKGROUND

Because of the favourable safety and tolerability profiles of atazanavir (ATV) and raltegravir (RAL), attention has recently turned to the use of dual ATV plus RAL therapy as a nucleoside reverse transcriptase inhibitor-sparing treatment strategy in highly antiretroviral treatment (ART)-experienced HIV-infected patients.

METHODS

A retrospective observational study was carried out to assess the maintenance of viral suppression and ART tolerability in 20 highly ART-experienced patients with viral suppression, who had been switched to RAL and unboosted ATV dual therapy, using data collected during standard-of-care visits.

RESULTS

At 6, 12 and 18 months, viral load was maintained at <400 HIV RNA copies/ml, with only one participant recording a detectable viral load (150 copies/ml) at the 6-month time point. Stable CD4(+) T-cell counts were maintained throughout the study period. Five participants changed regimen during the 18-month follow-up, with the median time to switch being 9 months (range 2-12). In three cases, patients were changed from dual therapy because of adverse events while on the regimen. These included increased fatigue (two patients), persistently increased bilirubin (one patient) and gastrointestinal side effects (one patient). Two additional patients changed therapy: one patient added lamivudine and one ceased ATV to pre-empt a potential drug-drug interaction. All five patients who switched from ATV/RAL before 12 months follow-up maintained viral suppression, implying no disadvantage from switching to dual therapy.

CONCLUSIONS

Dual therapy with ATV plus RAL maintained viral suppression in this small group of highly ART-experienced patients. Further investigation of this novel dual therapy regimen is warranted.

Raltegravir is a substrate for SLC22A6: a putative mechanism for the interaction between raltegravir and tenofovir

The identification of transporters of the HIV integrase inhibitor raltegravir could be a factor in an understanding of the pharmacokinetic-pharmacodynamic relationship and reported drug interactions of raltegravir. Here we determined whether raltegravir was a substrate for ABCB1 or the influx transporters SLCO1A2, SLCO1B1, SLCO1B3, SLC22A1, SLC22A6, SLC10A1, SLC15A1, and SLC15A2. Raltegravir transport by ABCB1 was studied with CEM, CEM(VBL100), and Caco-2 cells. Transport by uptake transporters was assessed by using a Xenopus laevis oocyte expression system, peripheral blood mononuclear cells, and primary renal cells. The kinetics of raltegravir transport and competition between raltegravir and tenofovir were also investigated using SLC22A6-expressing oocytes. Raltegravir was confirmed to be an ABCB1 substrate in CEM, CEM(VBL100), and Caco-2 cells. Raltegravir was also transported by SLC22A6 and SLC15A1 in oocyte expression systems but not by other transporters studied. The K(m) and V(max) for SLC22A6 transport were 150 μM and 36 pmol/oocyte/h, respectively. Tenofovir and raltegravir competed for SLC22A6 transport in a concentration-dependent manner. Raltegravir inhibited 1 μM tenofovir with a 50% inhibitory concentration (IC(50)) of 14.0 μM, and tenofovir inhibited 1 μM raltegravir with an IC(50) of 27.3 μM. Raltegravir concentrations were not altered by transporter inhibitors in peripheral blood mononuclear cells or primary renal cells. Raltegravir is a substrate for SLC22A6 and SLC15A1 in the oocyte expression system. However, transport was limited compared to endogenous controls, and these transporters are unlikely to have a great impact on raltegravir pharmacokinetics.

Noninfectious HIV-related comorbidities and HAART toxicities: choosing alternative antiretroviral strategies

In the HAART era, clinicians are faced with the challenge of treating an aging HIV-infected population increasingly affected by severe comorbidities, which may compromise the tolerability of antiretroviral regimens. In this special population, it is imperative for physicians to carefully tailor antiretroviral treatment in order not to worsen patients’ underlying clinical conditions and to achieve both tolerability and immune–virologic efficacy. This article aims to explore the impact of standard HAART regimens on the different noninfectious HIV-related comorbidities: metabolic, cardiovascular, bone and renal diseases, in order to provide tools to fit the most appropriate antiretroviral combination according to individual clinical conditions. Clinical experience with alternative antiretroviral strategies, avoiding nucleoside reverse transcriptase inhibitor toxicities and involving new antiretroviral classes, will be reviewed to obtain an overview on future perspectives.