Determinants of early change in serum creatinine after initiation of dolutegravir-based antiretroviral therapy in South Africa

AIMS

Dolutegravir increases serum creatinine by inhibiting its renal tubular secretion and elimination. We investigated determinants of early changes in serum creatinine in a southern African cohort starting first-line dolutegravir-based antiretroviral therapy (ART).

METHODS

We conducted a secondary analysis of data from participants in a randomized controlled trial of dolutegravir, emtricitabine and tenofovir disoproxil fumarate (TDF) or tenofovir alafenamide fumarate (TAF) (ADVANCE, NCT03122262). We assessed clinical, pharmacokinetic and genetic factors associated with change in serum creatinine from baseline to Week 4 using linear regression models adjusted for age, sex, baseline serum creatinine, HIV-1 RNA concentration, CD4 T-cell count, total body weight and co-trimoxazole use.

RESULTS

We included 689 participants, of whom 470 had pharmacokinetic data and 315 had genetic data. Mean change in serum creatinine was 11.3 (SD 9.9) μmol.L-1. Factors that were positively associated with change in serum creatinine at Week 4 were increased log dolutegravir area under the 24-h concentration-time curve (change in creatinine coefficient [β] = 2.78 μmol.L-1 [95% confidence interval (CI) 0.54, 5.01]), TDF use (β = 2.30 [0.53, 4.06]), male sex (β = 5.20 [2.92, 7.48]), baseline serum creatinine (β = -0.22 [-0.31, -0.12]) and UGT1A1 rs929596 A→G polymorphism with a dominant model (β = -2.33 [-4.49, -0.17]). The latter did not withstand correction for multiple testing.

CONCLUSIONS

Multiple clinical and pharmacokinetic factors were associated with early change in serum creatinine in individuals initiating dolutegravir-based ART. UGT1A1 polymorphisms may play a role, but further research on genetic determinants is needed.

Comparative Clinical Pharmacokinetics and Pharmacodynamics of HIV-1 Integrase Strand Transfer Inhibitors: An Updated Review

Bictegravir, cabotegravir, dolutegravir, elvitegravir, and raltegravir are members of the latest class of antiretrovirals available to treat human immunodeficiency virus (HIV) infection, the integrase strand transfer inhibitors. Integrase strand transfer inhibitors are potent inhibitors of the HIV integrase enzyme with IC_90/95 values in the low nanogram per milliliter range and they retain antiviral activity against strains of HIV with acquired resistance to other classes of antiretrovirals. Each of the integrase strand transfer inhibitors have unique pharmacokinetic/pharmacodynamic properties, influencing their role in clinical use in specific subsets of patients. Cabotegravir, approved for use in Canada but not yet by the US Food and Drug Administration, is formulated in both oral and intramuscular formulations; the latter of which has shown efficacy as a long-acting extended-release formulation. Cabotegravir, raltegravir, and dolutegravir have minimal drug-drug interaction profiles, as their metabolism has minimal cytochrome P450 involvement. Conversely, elvitegravir metabolism occurs primarily via cytochrome P450 3A4 and requires pharmacokinetic boosting to achieve systemic exposures amenable to once-daily dosing. Bictegravir metabolism has similar contributions from both cytochrome P450 3A4 and uridine 5'-diphospho-glucuronosyltransferase 1A1. Bictegravir, dolutegravir, and raltegravir are recommended components of initial regimens for most people with HIV in the US adult and adolescent HIV treatment guidelines. This review summarizes and compares the pharmacokinetics and pharmacodynamics of the integrase strand transfer inhibitor agents, and describes specific pharmacokinetic considerations for persons with hepatic impairment, renal dysfunction, pregnancy, and co-infections.

HIV-1 Integrase Inhibitors: A Comparative Review of Efficacy and Safety

The newest class of antiretrovirals for all persons living with HIV are the integrase strand transfer inhibitors (INSTIs). Since 2007, five INSTIs have been introduced: raltegravir, elvitegravir, dolutegravir, bictegravir, and cabotegravir. The INSTIs have favorable pharmacokinetic and pharmacodynamic properties, which contribute to both their effectiveness and their ease of use. With the exception of cabotegravir, each INSTI is US Food and Drug Administration approved for treatment-naïve individuals initiating antiretroviral therapy. All of the INSTIs, except raltegravir, are approved for antiretroviral treatment simplification for virologically suppressed patients without INSTI resistance. Data also support the use of dolutegravir and raltegravir in individuals with antiretroviral resistance as part of an optimized antiretroviral regimen. INSTIs are generally well tolerated by people living with HIV compared with older classes of antiretrovirals, but emerging data suggest that some INSTIs contribute to weight gain. Due to their efficacy, safety, and ease of use, HIV treatment guidelines recommend oral INSTIs as preferred components of antiretroviral therapy for individuals initiating therapy. The newest INSTI, cabotegravir, represents an alternative to oral administration of life-long antiretroviral therapy with the availability of a long-acting injectable formulation. This review summarizes the current use of INSTIs in adults living with HIV, highlighting the similarities and differences within the class related to pharmacodynamics, pharmacokinetics, safety, dosing, and administration that contribute to their role in modern antiretroviral therapy.

Simplified dolutegravir dosing for children with HIV weighing 20 kg or more: pharmacokinetic and safety substudies of the multicentre, randomised ODYSSEY trial

BACKGROUND

Paediatric dolutegravir doses approved by stringent regulatory authorities (SRAs) for children weighing 20 kg to less than 40 kg until recently required 25 mg and 10 mg film-coated tablets. These tablets are not readily available in low-resource settings where the burden of HIV is highest. We did nested pharmacokinetic substudies in patients enrolled in the ODYSSEY-trial to evaluate simplified dosing in children with HIV.

METHODS

We did pharmacokinetic and safety substudies within the open-label, multicentre, randomised ODYSSEY trial (NCT02259127) of children with HIV starting treatment in four research centres in Uganda and Zimbabwe. Eligible children were randomised to dolutegravir in ODYSSEY and weighed 20 kg to less than 40 kg. In children weighing 20 kg to less than 25 kg, we assessed dolutegravir's pharmacokinetics in children given once daily 25 mg film-coated tablets (approved by the SRAs at the time of the study) in part one of the study, and 50 mg film-coated tablets (adult dose) or 30 mg dispersible tablets in part two of the study. In children weighing 25 kg to less than 40 kg, we also assessed dolutegravir pharmacokinetics within-subject on film-coated tablet doses of 25 mg or 35 mg once daily, which were approved by the SRAs for the children's weight band; then switched to 50 mg film-coated tablets once daily. Steady-state 24 h dolutegravir plasma concentration-time pharmacokinetic profiling was done in all enrolled children at baseline and 1, 2, 3, 4, 6, and 24 h after observed dolutegravir intake. Target dolutegravir trough concentrations (C_trough) were based on reference adult pharmacokinetic data and safety was evaluated in all children in the corresponding weight bands who consented to pharmacokinetic studies and received the studied doses.

FINDINGS

Between Sept 22, 2016, and May 31, 2018, we enrolled 62 black-African children aged from 6 years to younger than 18 years (84 pharmacokinetic-profiles). In children weighing 20 kg to less than 25 kg taking 25 mg film-coated tablets, the geometric mean (GM) C_trough (coefficient of variation) was 0·32 mg/L (94%), which was 61% lower than the GM C_trough of 0·83 mg/L (26%) in fasted adults on dolutegravir 50 mg once-daily; in children weighing 25 kg to less than 30 kg taking 25 mg film-coated tablets, the GM C_trough was 0·39 mg/L (48%), which was 54% lower than the GM C_trough in fasted adults; and in those 30 kg to less than 40 kg taking 35 mg film-coated tablets the GM C_trough was 0·46 mg/L (63%), which was 45% lower than the GM C_trough in fasted adults. On 50 mg film-coated tablets or 30 mg dispersible tablets, C_trough was close to the adult reference (with similar estimates on the two formulations in children in the 20 to <25 kg weight band), with total exposure (area under the concentration-time curve from 0 h to 24 h) in between reference values in adults dosed once and twice daily, where safety data are reassuring, although maximum concentrations were higher in children weighing 20 kg to less than 25 kg than in the twice-daily adult reference. Over a 24-week follow-up period in 47 children on 30 mg dispersible tablets or 50 mg film-coated tablets, none of the three reported adverse events (cryptococcal meningitis, asymptomatic anaemia, and asymptomatic neutropenia) were considered related to dolutegravir.

INTERPRETATION

Adult dolutegravir 50 mg film-coated tablets given once daily provide appropriate pharmacokinetic profiles in children weighing 20 kg or more, with no safety signal, allowing simplified practical dosing and rapid access to dolutegravir. These results informed the WHO 2019 dolutegravir paediatric dosing guidelines and have led to US Food and Drug Administration approval of adult dosing down to 20 kg.

FUNDING

Paediatric European Network for Treatment of AIDS Foundation, ViiV Healthcare, UK Medical Research Council.

Prediction of Maternal and Fetal Pharmacokinetics of Dolutegravir and Raltegravir Using Physiologically Based Pharmacokinetic Modeling

BACKGROUND

Predicting drug pharmacokinetics in pregnant women including placental drug transfer remains challenging. This study aimed to develop and evaluate maternal-fetal physiologically based pharmacokinetic models for two antiretroviral drugs, dolutegravir and raltegravir.

Pharmacokinetics and Pharmacodynamics of Cabotegravir, a Long-Acting HIV Integrase Strand Transfer Inhibitor

Available antiretroviral drugs have demonstrated effectiveness in both pre-exposure prophylaxis and treatment of HIV infection. However, some concerns still persist regarding these therapies, mainly related to patient adherence, drug toxicity and dosing convenience. Cabotegravir is a potent integrase strand transfer inhibitor with a chemical structure similar to dolutegravir that is under clinical evaluation both as oral and long-acting injectable (LAI) formulations for both the prevention or treatment of HIV infection. Indeed, preclinical and clinical studies have consistently shown that LAI cabotegravir is readily absorbed following intramuscular and subcutaneous administration, with an elimination half-life of approximately 40 days, permitting infrequent dosing, possibly once every 1 or 2 months (eventually combined with rilpivirine). Here, we reviewed the existing literature on the preclinical and clinical pharmacokinetics and pharmacodynamics of LAI cabotegravir, with emphasis on the actual pharmacokinetic challenges of this novel formulation, as well as its potential to act as a victim or perpetrator of drug-drug interactions.

Safety and pharmacokinetics of dolutegravir in pregnant mothers with HIV infection and their neonates: A randomised trial (DolPHIN-1 study)

BACKGROUND

The global transition to use of dolutegravir (DTG) in WHO-preferred regimens for HIV treatment is limited by lack of knowledge on use in pregnancy. Here we assessed the relationship between drug concentrations (pharmacokinetics, PK), including in breastmilk, and impact on viral suppression when initiated in the third trimester (T3).

METHODS AND FINDINGS

In DolPHIN-1, HIV-infected treatment-naïve pregnant women (28-36 weeks of gestation, age 26 (19-42), weight 67kg (45-119), all Black African) in Uganda and South Africa were randomised 1:1 to dolutegravir (DTG) or efavirenz (EFV)-containing ART until 2 weeks post-partum (2wPP), between 9th March 2017 and 16th January 2018, with follow-up until six months postpartum. The primary endpoint was pharmacokinetics of DTG in women and breastfed infants; secondary endpoints included maternal and infant safety and viral suppression. Intensive pharmacokinetic sampling of DTG was undertaken at day 14 and 2wPP following administration of a medium-fat breakfast, with additional paired sampling between maternal plasma and cord blood, breastmilk and infant plasma. No differences in median baseline maternal age, gestation (31 vs 30 weeks), weight, obstetric history, viral load (4.5 log10 copies/mL both arms) and CD4 count (343 vs 466 cells/mm3) were observed between DTG (n = 29) and EFV (n = 31) arms. Although DTG Ctrough was below the target 324ng/mL (clinical EC90) in 9/28 (32%) mothers in the third trimester, transfer across the placenta (121% of plasma concentrations) and into breastmilk (3% of plasma concentrations), coupled with slower elimination, led to significant infant plasma exposures (3-8% of maternal exposures). Both regimens were well-tolerated with no significant differences in frequency of adverse events (two on DTG-ART, one on EFV-ART, all considered unrelated to drug). No congenital abnormalities were observed. DTG resulted in significantly faster viral suppression (P = 0.02) at the 2wPP visit, with median time to <50 copies/mL of 32 vs 72 days. Limitations related to the requirement to initiate EFV-ART prior to randomisation, and to continue DTG for only two weeks postpartum.

CONCLUSION

Despite low plasma DTG exposures in the third trimester, transfer across the placenta and through breastfeeding was observed in this study, with persistence in infants likely due to slower metabolic clearance. HIV RNA suppression <50 copies/mL was twice as fast with DTG compared to EFV, suggesting DTG has potential to reduce risk of vertical transmission in mothers who are initiated on treatment late in pregnancy.

TRIAL REGISTRATION

clinicaltrials.gov NCT02245022.

Pharmacokinetics and Pharmacodynamics of Cabotegravir, a Long-Acting HIV Integrase Strand Transfer Inhibitor

Available antiretroviral drugs have demonstrated effectiveness in both pre-exposure prophylaxis and treatment of HIV infection. However, some concerns still persist regarding these therapies, mainly related to patient adherence, drug toxicity and dosing convenience. Cabotegravir is a potent integrase strand transfer inhibitor with a chemical structure similar to dolutegravir that is under clinical evaluation both as oral and long-acting injectable (LAI) formulations for both the prevention or treatment of HIV infection. Indeed, preclinical and clinical studies have consistently shown that LAI cabotegravir is readily absorbed following intramuscular and subcutaneous administration, with an elimination half-life of approximately 40 days, permitting infrequent dosing, possibly once every 1 or 2 months (eventually combined with rilpivirine). Here, we reviewed the existing literature on the preclinical and clinical pharmacokinetics and pharmacodynamics of LAI cabotegravir, with emphasis on the actual pharmacokinetic challenges of this novel formulation, as well as its potential to act as a victim or perpetrator of drug-drug interactions.

Pharmacokinetics of HIV-Integrase Inhibitors During Pregnancy: Mechanisms, Clinical Implications and Knowledge Gaps

Prevention of mother-to-child transmission of HIV and optimal maternal treatment are the most important goals of antiretroviral therapy in pregnant women with HIV. These goals may be at risk due to possible reduced exposure during pregnancy caused by physiological changes. Limited information is available on the impact of these physiological changes. This is especially true for HIV-integrase inhibitors, a relatively new class of drugs, recommended first-line agents and hence used by a large proportion of HIV-infected patients. Therefore, the objective of this review is to provide a detailed overview of the pharmacokinetics of HIV-integrase inhibitors in pregnancy. Second, this review defines potential causes for the change in pharmacokinetics of HIV-integrase inhibitors during pregnancy. Despite increased clearance, for raltegravir 400 mg twice daily and dolutegravir 50 mg once daily, exposure during pregnancy seems adequate; however, for elvitegravir, the proposed minimal effective concentration is not reached during pregnancy. Lower exposure to these drugs may be caused by increased hormone levels and, subsequently, enhanced drug metabolism during pregnancy. The pharmacokinetics of bictegravir and cabotegravir, which are under development, have not yet been evaluated in pregnant women. New studies need to prospectively assess whether adequate exposure is reached in pregnant women using these new HIV-integrase inhibitors. To further optimize antiretroviral treatment in pregnant women, studies need to unravel the underlying mechanisms behind the changes in the pharmacokinetics of HIV-integrase inhibitors during pregnancy. More knowledge on altered pharmacokinetics during pregnancy and the underlying mechanisms contribute to the development of effective and safe antiretroviral therapy for HIV-infected pregnant women.

Dolutegravir pharmacokinetics in pregnant and postpartum women living with HIV

OBJECTIVE

To evaluate dolutegravir pharmacokinetics during pregnancy compared with postpartum and in infant washout samples after delivery.

DESIGN

Ongoing, nonrandomized, open-label, parallel-group, multicenter phase-IV prospective study of antiretroviral pharmacokinetics in HIV-infected pregnant women and infants.

METHODS

Intensive steady-state 24 h pharmacokinetic profiles after dolutegravir 50 mg once-daily were performed during the second trimester (2T), third trimester (3T) and postpartum. Maternal delivery and postnatal infant samples were collected after birth. Dolutegravir was measured by validated LC-MS/MS; quantitation limit was 0.005 μg/ml. A two-tailed Wilcoxon signed-rank test (α = 0.10) was employed for paired within-subject comparisons.

RESULTS

Twenty-nine enrolled participants had a median age of 32 years (range 21-42). Pharmacokinetic data were available for 15 (2T), 28 (3T) and 23 (postpartum) women. Median dolutegravir AUC0-24,Cmax and C24 were 25-51% lower in the 2T and 3T compared with postpartum. The median cord blood/maternal plasma concentration ratio was 1.25 (n = 18). In 21 infants, median elimination half-life was 32.8 h after in utero exposure. Viral load at delivery was less than 50 copies/ml for 27/29 women (93%). Twenty-nine infants were HIV-negative. Renal abnormalities noted on ultrasound in two infants were deemed possibly related to dolutegravir.

CONCLUSION

Dolutegravir exposure is lower in pregnancy compared with postpartum in the same women on once-daily dosing. Median AUC0-24 during pregnancy was similar to, whereas trough concentrations were lower than, those seen in nonpregnant adults. Trough concentrations in pregnancy were well above dolutegravir EC90 (0.064 μg/ml). Dolutegravir readily crosses the placenta. Infant elimination is prolonged, with half-life over twice that of historical adult controls.

A Two-Way Steady-State Pharmacokinetic Interaction Study of Doravirine (MK-1439) and Dolutegravir

INTRODUCTION

Doravirine, a non-nucleoside reverse-transcriptase inhibitor in development for the treatment of patients with human immunodeficiency virus-1 infection, has potential to be used concomitantly in antiretroviral therapy with dolutegravir, an integrase strand transfer inhibitor. The pharmacokinetic interactions between these drugs were therefore assessed.

METHODS

Oral formulations of doravirine and dolutegravir were dosed both individually and concomitantly once daily in healthy adults. Twelve subjects (six were male), 23-42 years of age, were enrolled and 11 completed this phase I, open-label, three-period, fixed-sequence study per protocol; one subject was discontinued for a positive cotinine test at admission to period 2. In period 1, dolutegravir 50 mg was administered for 7 days. After a 7-day washout, doravirine 200 mg was dosed for 7 days in period 2, followed (without washout) by both doravirine and dolutegravir simultaneously for 7 days in period 3. Plasma samples were taken to determine dolutegravir and doravirine concentrations.

RESULTS

The steady-state concentration 24 h post-dose (C₂₄) of dolutegravir was not substantially altered by co-administration of doravirine multiple doses; area under the plasma concentration-time curve from dosing to 24 h post-dose (AUC_0-24), maximum concentration (C _max), and C₂₄ geometric mean ratios were 1.36, 1.43, and 1.27, respectively. The pharmacokinetics of doravirine was not affected by multiple doses of dolutegravir (geometric mean ratios: 1.00, 0.98, and 1.06 for AUC_0-24, C₂₄, and C _max, respectively). Both drugs were generally well tolerated.

CONCLUSION

The results of this study demonstrate that concomitant administration of doravirine and dolutegravir in healthy subjects causes no clinically significant alteration in the pharmacokinetic and safety profiles of the two drugs, thereby supporting further evaluation of co-administration of these agents for human immunodeficiency virus-1 treatment.

Genetic barrier to resistance for dolutegravir

Dolutegravir is a novel integrase strand-transfer inhibitor that displays potent in vitro activity and a remarkably different resistance profile. Its robust pharmacokinetic/pharmacodynamic properties - long plasma t1/2, high plasma inhibition quotient, and slow dissociation rate from the integrase complex - suggest it should present a high barrier to resistance development. This has been confirmed in pivotal phase III studies of initial therapy, with none out of 1,118 treated individuals selecting resistance-associated mutations at the integrase or reverse transcriptase. In integrase-naive subjects with virological failure, a rescue intervention with dolutegravir has shown significantly higher rates of virological suppression than raltegravir, as well as significantly lower rates of selection of resistance both at the integrase and against the optimized background. Unexpectedly, a mutation rarely selected in this scenario (R263K) induces a fitness cost that prevents HIV-1 from evading drug pressure, and accumulation of further secondary mutations does not occur and has not been able to compensate the replication capacity deficit in the aftermath of the appearance of a single drug resistance mutation. Therefore, both in vitro and in vivo, it leads the virus to a previously unnoticed evolutionary pathway with low chances to develop resistance to both dolutegravir and other families of antiretrovirals present in the background. This high genetic barrier to resistance development in early stages of antiretroviral treatment can help preserve future treatment options in patients who fail antiretroviral therapy.

Pharmacokinetics and dose-range finding toxicity of a novel anti-HIV active integrase inhibitor

Integration of viral DNA into human chromosomal DNA catalyzed by HIV integrase represents the "point of no return" in HIV infection. For this reason, HIV integrase is considered a crucial target in the development of new anti-HIV therapeutic agents. We have discovered a novel HIV integrase inhibitor 1, that exhibits potent antiviral activity and a favorable metabolism profile. This paper reports on the pharmacokinetics and toxicokinetics of compound 1 and the relevance of these findings with respect to further development of this integrase-targeted antiviral agent. Oral administration of compound 1 in Sprague Dawley rats revealed rapid absorption. Drug exposure increased with increasing drug concentration, indicative of appropriate dose-dependence correlation. Compound 1 exhibited suitable plasma half-life, extensive extravascular distribution and acceptable bioavailability. Toxicity studies revealed no compound-related clinical pathology findings. There were no changes in erythropoietic, white blood cell or platelet parameters in male and female rats. There was no test-article related change in other clinical chemistry parameters. In addition, there were no detectable levels of bilirubin in the urine and there were no treatment-related effects on urobilinogen or other urinalysis parameters. The preclinical studies also revealed that the no observed adverse effect level and the maximum tolerated dose were both high (>500mg/kg/day). The broad and significant antiviral activity and favorable metabolism profile of this integrase inhibitor, when combined with the in vivo pharmacokinetic and toxicokinetic data and their pharmacological relevance, provide compelling and critical support for its further development as an anti-HIV therapeutic agent.

Effect of ginkgo biloba on the pharmacokinetics of raltegravir in healthy volunteers

Medicinal herbs may cause clinically relevant drug interactions with antiretroviral agents. Ginkgo biloba extract is a popular herbal product among HIV-infected patients because of its positive effects on cognitive function. Raltegravir, an HIV integrase inhibitor, is increasingly being used as part of combined antiretroviral therapy. Clinical data on the potential inhibitory or inductive effect of ginkgo biloba on the pharmacokinetics of raltegravir were lacking, and concomitant use was not recommended. We studied the effect of ginkgo biloba extract on the pharmacokinetics of raltegravir in an open-label, randomized, two-period, crossover phase I trial in 18 healthy volunteers. Subjects were randomly assigned to a regimen of 120 mg of ginkgo biloba twice daily for 15 days plus a single dose of raltegravir (400 mg) on day 15, a washout period, and 400 mg of raltegravir on day 36 or the test and reference treatments in reverse order. Pharmacokinetic sampling of raltegravir was performed up to 12 h after intake on an empty stomach. All subjects (9 male) completed the trial, and no serious adverse events were reported. Geometric mean ratios (90% confidence intervals) of the area under the plasma concentration-time curve from dosing to infinity (AUC(0-∞)) and the maximum plasma concentration (C(max)) of raltegravir with ginkgo biloba versus raltegravir alone were 1.21 (0.93 to 1.58) and 1.44 (1.03 to 2.02). Ginkgo biloba did not reduce raltegravir exposure. The potential increase in the C(max) of raltegravir is probably of minor importance, given the large intersubject variability of raltegravir pharmacokinetics and its reported safety profile.

Pharmacology of HIV integrase inhibitors

PURPOSE OF REVIEW

The purpose of this study is to review recent and relevant pharmacology data for three HIV integrase inhibitors: raltegravir (marketed), dolutegravir, and elvitegravir (both in phase III drug development).

RECENT FINDINGS

Data from January 2011 to April 2012 were evaluated. These data better characterized integrase inhibitor pharmacokinetics, assessed dosing regimens, and investigated previously undescribed drug-drug interactions. Due to formulation challenges, raltegravir inter-patient and intra-patient pharmacokinetic variability is high. Twice-daily 400  mg dosing has been shown to be clinically superior to 800  mg once-daily dosing. A pediatric formulation of raltegravir with less variable pharmacokinetics and greater bioavailability was US Food and Drug Administration (US FDA)-approved in December 2011. Cobicistat-boosted elvitegravir, and the second-generation integrase inhibitor dolutegravir, have lower pharmacokinetic variability and are dosed once daily. Dolutegravir drug interactions are similar to raltegravir, whereas boosted elvitegravir participates in additional CYP3A-mediated interactions.

SUMMARY

Raltegravir's potent antiretroviral activity has resulted in widespread use in both treatment-naïve and experienced patients. Dolutegravir and cobicistat-boosted elvitegravir have some pharmacokinetic advantages. Pharmacokinetic data in special populations (pregnancy, pediatrics) to optimize dosing are still required.

Effects of etravirine alone and with ritonavir-boosted protease inhibitors on the pharmacokinetics of dolutegravir

Dolutegravir (DTG) is an unboosted, once-daily integrase inhibitor currently in phase 3 trials. Two studies evaluated the effects of etravirine (ETR) alone and in combination with ritonavir (RTV)-boosted protease inhibitors (PIs) on DTG pharmacokinetics (PK) in healthy subjects. DTG 50 mg every 24 h (q24h) was administered alone for 5 days in period 1, followed by combination with ETR at 200 mg q12h for 14 days in period 2 (study 1) or with ETR/lopinavir (LPV)/RTV at 200/400/100 mg q12h or ETR/darunavir (DRV)/RTV at 200/600/100 mg q12h for 14 days in period 2 (study 2). PK samples were collected on day 5 in period 1 and day 14 in period 2. All of the treatments were well tolerated. ETR significantly decreased exposures of DTG, with geometric mean ratios of 0.294 (90% confidence intervals, 0.257 to 0.337) for the area under the curve from time zero until the end of the dosage interval (AUC(0-τ)), 0.484 (0.433 to 0.542) for the observed maximum plasma concentration (C(max)), and 0.121 (0.093 to 0.157) for the plasma concentration at the end of the dosage interval (C(τ)). ETR combined with an RTV-boosted PI affected the exposure of DTG to a lesser degree: ETR/LPV/RTV treatment had no effect on the DTG plasma AUC(0-τ) and C(max), whereas the C(τ) increased by 28%. ETR/DRV/RTV modestly decreased the plasma DTG AUC(0-τ), C(max), and C(τ) by 25, 12, and 37%, respectively. Such effects of ETR/LPV/RTV and ETR/DRV/RTV are not considered clinically relevant. The combination of DTG and ETR alone should be avoided; however, DTG may be coadministered with ETR without a dosage adjustment if LPV/RTV or DRV/RTV is concurrently administered.

6-Benzylamino 4-oxo-1,4-dihydro-1,8-naphthyridines and 4-oxo-1,4-dihydroquinolines as HIV integrase inhibitors

SAR studies on the quinolone carboxylic acid class of HIV-1 integrase inhibitors focused on improving the metabolic stability and led to the discovery of 27 and 38.

Prevention of HIV protease inhibitor-induced dysregulation of hepatic lipid metabolism by raltegravir via endoplasmic reticulum stress signaling pathways

Hyperlipidemia associated with the HIV protease inhibitor (PI), the major component of highly active antiretroviral treatment (HAART) for HIV infection, has stimulated interest in developing new agents that minimize these side effects in the clinic. HIV integrase inhibitor is a new class of anti-HIV agents. Raltegravir is a first-in-its-class oral integrase inhibitor and has potent inhibitory activity against HIV-1 strains that are resistant to other antiretroviral regimens. Our previous studies have demonstrated that HIV PI-induced endoplasmic reticulum (ER) stress links to dysregulation of lipid metabolism. However, little information is available as to whether raltegravir would have similar effects as the HIV PIs. In this study, we examined the effect of raltegravir on lipid metabolism both in primary rat hepatocytes and in in vivo mouse models, and we further determined whether the combination of raltegravir with existing HIV PIs would potentially exacerbate or prevent the previously observed development of dyslipidemia. The results indicated that raltegravir did not induce ER stress or disrupt lipid metabolism either in vitro or in vivo. However, HIV PI-induced ER stress and lipid accumulation were significantly inhibited by raltegravir both in in vitro primary rat hepatocytes and in in vivo mouse liver. High-performance liquid chromatography analysis further demonstrated that raltegravir did not affect the uptake and metabolism of HIV PIs in hepatocytes. Thus, raltegravir has less hepatic toxicity and could prevent HIV PI-induced dysregulation of lipid metabolism by inhibiting ER stress. These results suggest that incorporation of this HIV integrase inhibitor may reduce the side effects associated with current HAART.

[Pharmacokinetics and interactions of raltegravir]

Raltegravir is the first integrase inhibitor approved for the treatment of HIV-1 infection in pretreated adults with evidence of viral replication despite receiving antiretroviral therapy. Raltegravir is administered orally at a dose of 400 mg every 12 hours, with or without food. This drug is mainly eliminated through UGT1A1-mediated glucuronidation and is not an inhibitor or inducer of the main liver cytochrome P450 isoenzymes; consequently there is virtually no risk of pharmacological interactions with most commonly used drugs such as methadone, azole antifungal agents or drugs used to treat erectile dysfunction. Studies of interaction with other antiretroviral agents show that raltegravir can be used in combination with tenofovir, efavirenz, atazanavir, ritonavir or tipranavir/ritonavir without the need for dose adjustments. When combined with rifampicin, the dose of raltegravir should be increased to 800 mg/12 h. Proton pump inhibitors increase plasma levels of raltegravir (a 3-fold increase in exposure or AUC levels), and consequently their combined use should be avoided as far as posible. Raltegravir is well tolerated and does not require dose adjustments in patients with severe renal impairment or mild-to-moderate liver impairment. There are no studies in patients with severe liver impairment.

[Potential of integrase inhibitors to deplete HIV reservoirs or prevent their replenishment]

The early establishment of an HIV-1 reservoir with integrated provirus in the DNA of cells with latent infection hampers viral eradication, despite maintenance of viral loads lower than 50 copies/mL for years. By early initiation of highly suppressive antiretroviral therapy (ART), the half-life of this reservoir could be as short as 4.6 months and require only 7.7 years for complete elimination. The constant presence of low-grade viral replication probably indefinitely replenishes this resting CD4+ T cell reservoir. This reservoir probably results from both the release of virus stored in latently-infected cells that have become activated and from residual replication of some still-activated cells. This also allows new resistant mutants selected after therapeutic failure to be incorporated into the reservoir. Raltegravir has been demonstrated to significantly reduce elimination times in the first two viral decay phases after initiation of ART. On starting the second phase, the viral load was 70% lower in patients treated with raltegravir than in those treated with efavirenz. Through its late mechanism of action in the HIV-1 cell cycle, this drug could induce greater decreases in proviral DNA than other antiretroviral agents. The presence of unintegrated HIV DNA under prolonged effective ART indicates that either there is continual low-level viral replication or that this unintegrated DNA can persist for prolonged periods. In both cases, intensification of ART with raltegravir could provide beneficial effects on the speed of elimination of the HIV-1 reservoir.

Raltegravir: the first HIV integrase inhibitor

BACKGROUND

The availability of new classes of antiretroviral drugs has made it possible for HIV-infected individuals who are highly treatment experienced to achieve the goals of immunologic recovery and virologic suppression. Raltegravir is the first integrase inhibitor to be approved by the US Food and Drug Administration for use in antiretroviral treatment- experienced adult patients with viral resistance.

OBJECTIVE

This article reviews the pharmacology, pharmacokinetics, pharmacodynamics, efficacy, tolerability, resistance profile, drug interactions, and dosing and administration of raltegravir.

METHODS

Searches of MEDLINE and International Pharmaceutical Abstracts from 1964 to July 2008 were conducted using the terms integrase, raltegravir, and MK-0518. Relevant information was extracted from the identified clinical trials and review articles. Abstracts from the Conference on Retroviruses and Opportunistic Infections (1998-2008); Interscience Conference on Antimicrobial Agents and Chemotherapy (1999-2007); International AIDS Society Conference on HIV Pathogenesis, Treatment and Prevention (2001-2007); and European AIDS Conference (2001-2007) were also searched.

RESULTS

Raltegravir blocks HIV replication by inhibiting essential strand-transfer activities of integrase. Raltegravir is rapidly absorbed, with a median T(max) of approximately 4 hours in the fasting state. No dose adjustment is recommended in patients with moderate renal or hepatic insufficiency, and raltegravir may be taken without regard to meals. In Phase II studies in treatment-naive patients, raltegravir had efficacy similar to that of standard initial therapies. In 2 interrelated Phase III clinical studies in treatment-experienced patients with drug-resistant disease, the addition of raltegravir to an optimized background regimen significantly lowered HIV RNA compared with optimized background treatment alone (62.1% vs 32.9%, respectively; P < 0.001). Raltegravir was generally well tolerated. The most common adverse effects reported in Phase II/III trials in treatment-experienced patients were diarrhea (16.6%), nausea (9.9%), and headache (9.7%). Cytochrome P450-related drug interactions are not expected, as raltegravir is not a CYP substrate, inducer, or inhibitor. However, to prevent failure of raltegravir, the drug should not be coadministered with rifampin.

CONCLUSION

Raltegravir is a potent and generally well tolerated antiretroviral agent that may play an important role in the treatment of patients harboring resistance to other antiretrovirals.

Elvitegravir, an oral HIV integrase inhibitor, for the potential treatment of HIV infection

The treatment of HIV is often complicated by the emergence of antiretroviral (ARV) resistance, which has prompted the development of ARV drugs with novel mechanisms of action and resistance profiles. One of the newest classes of ARVs is the integrase inhibitors. These agents inhibit viral replication by preventing integration of viral DNA into the host cell. Japan Tobacco Inc and Gilead Sciences Inc are developing elvitegravir, a novel integrase inhibitor undergoing phase III clinical trials. Elvitegravir is predominantly metabolized via cytochrome P450 (CYP)3A4, along with minor pathways including glucuronidation via UGT1A1/3 and oxidative metabolism. Consequently, the coadministration of elvitegravir with the protease inhibitor ritonavir (a substantial CYP3A4 inhibitor) results in significantly enhanced bioavailability and a longer half-life than with elvitegravir alone, allowing for the once-daily dosing of elvitegravir. In vitro and clinical data suggest that elvitegravir has an overlapping resistance profile with raltegravir and with other integrase inhibitors that are in development. Data from phase I/II clinical trials have demonstrated excellent virological responses with elvitegravir, as well as minimal toxicities. At the time of publication, phase III trials to examine the efficacy and toxicity of elvitegravir were enrolling patients infected with HIV-1.

Drug interactions with new and investigational antiretrovirals

More than 20 individual and fixed-dose combinations of antiretrovirals are approved for the treatment of human immunodeficiency virus (HIV) infection. However, owing to the ongoing limitations of drug resistance and adverse effects, new treatment options are still required. A number of promising new agents in existing or new drug classes are in development or have recently been approved by the US FDA. Since these agents will be used in combination with other new and existing antiretrovirals, understanding the potential for drug interactions between these compounds is critical to their appropriate use. This article summarizes the drug interaction potential of new and investigational protease inhibitors (darunavir), non-nucleoside reverse transcriptase inhibitors (etravirine and rilpivirine), chemokine receptor antagonists (maraviroc, vicriviroc and INCB 9471), integrase inhibitors (raltegravir and elvitegravir) and maturation inhibitors (bevirimat).

Constraints on the dominant mechanism for HIV viral dynamics in patients on raltegravir

BACKGROUND

Raltegravir is the first publicly released HIV integrase inhibitor. In clinical trials, patients on a raltegravir-based highly active antiretroviral therapy (HAART) regimen were observed to have 70% less viraemia in the second-phase decay of viraemia than patients on an efavirenz-based HAART regimen. Because of this accelerated decay of viraemia, raltegravir has been speculated to have greater antiretroviral activity than efavirenz. Alternative explanations for this phenomenon are also possible. For example, the stage in the viral life cycle at which raltegravir acts might explain the distinct viral dynamics produced by this drug.

METHODS

In this report, we use a mathematical model of HIV viral dynamics to explore several hypotheses for why raltegravir causes different viral dynamics than efavirenz. Using the experimentally observed viral dynamics of raltegravir, we calculated constraints on the mechanisms possibly responsible for the unique viral dynamics produced by raltegravir.

RESULTS

We predicted that the dominant mechanism for the 70% reduction in the second-phase viraemia is not antiviral efficacy but the stage of the HIV viral life cycle at which raltegravir acts. Furthermore, we found that the kinetic constraints placed on the identity of the virus-producing cells of the second phase were most consistent with monocytes/macrophages.

CONCLUSIONS

Our model predictions have important implications for the motivation behind the use of raltegravir and our understanding of the virus-producing cells of the second-phase viraemia. Our results also highlight that the viral dynamics produced by different antiretroviral drugs should not be directly compared with each other.

Pharmacokinetic and pharmacodynamic predictions of novel potential HIV-1 integrase inhibitors

Virtual screening docking-based approach has been employed in order to select novel HIV-1 integrase (IN) potential inhibitors in large databases. Toxicity, metabolism and drug-like properties have been analyzed for the most promising compounds, using computational chemistry techniques. Results were compared and discussed with that obtained for a known HIV-1 (IN) inhibitor reported in the literature.

Studies of metabolism and disposition of potent human immunodeficiency virus (HIV) integrase inhibitors using19F-NMR spectroscopy

(19)F-nuclear magnetic resonance (NMR) has been extensively used in a drug-discovery programme to support the selection of candidates for further development. Data on an early lead compound, N-(4-fluorobenzyl)-5-hydroxy-1-methyl-2-(4-methylmorpholin-3-yl)-6-oxo-1,6-dihydropyrimidine-4-carboxamide (compound A (+)), and MK-0518 (N-(4-fluorobenzyl)-5-hydroxy-1-methyl-2-(1-methyl-1-{[(5-methyl-1,3,4-oxadiazol-2-yl)carbonyl]amino}ethyl)-6-oxo-1,6-dihydropyrimidine-4-carboxamide), a potent inhibitor of this series currently in phase III clinical trials, are described. The metabolic fate and excretion balance of compound A (+) and MK-0518 were investigated in rats and dogs following intravenous and oral dosing using a combination of (19)F-NMR-monitored enzyme hydrolysis and solid-phase extraction chromatography and NMR spectroscopy (SPEC-NMR). Dosing with the (3)H-labelled compound A (+) enabled the comparison of standard radiochemical analysis with (19)F-NMR spectroscopy to obtain quantitative metabolism and excretion data. Both compounds were eliminated mainly by metabolism. The major metabolite identified in rat urine and bile and in dog urine was the 5-O-glucuronide.

Lack of a significant drug interaction between raltegravir and tenofovir

Raltegravir is a novel human immunodeficiency virus type 1 (HIV-1) integrase inhibitor with potent in vitro activity (95% inhibitory concentration of 31 nM in 50% human serum). This article reports the results of an open-label, sequential, three-period study of healthy subjects. Period 1 involved raltegravir at 400 mg twice daily for 4 days, period 2 involved tenofovir disoproxil fumarate (TDF) at 300 mg once daily for 7 days, and period 3 involved raltegravir at 400 mg twice daily plus TDF at 300 mg once daily for 4 days. Pharmacokinetic profiles were also determined in HIV-1-infected patients dosed with raltegravir monotherapy versus raltegravir in combination with TDF and lamivudine. There was no clinically significant effect of TDF on raltegravir. The raltegravir area under the concentration time curve from 0 to 12 h (AUC(0-12)) and peak plasma drug concentration (C(max)) were modestly increased in healthy subjects (geometric mean ratios [GMRs], 1.49 and 1.64, respectively). There was no substantial effect of TDF on raltegravir concentration at 12 h postdose (C(12)) in healthy subjects (GMR [TDF plus raltegravir-raltegravir alone], 1.03; 90% confidence interval [CI], 0.73 to 1.45), while a modest increase (GMR, 1.42; 90% CI, 0.89 to 2.28) was seen in HIV-1-infected patients. Raltegravir had no substantial effect on tenofovir pharmacokinetics: C(24), AUC, and C(max) GMRs were 0.87, 0.90, and 0.77, respectively. Coadministration of raltegravir and TDF does not change the pharmacokinetics of either drug to a clinically meaningful degree. Raltegravir and TDF may be coadministered without dose adjustments.

Raltegravir, an HIV-1 integrase inhibitor for HIV infection

Merck & Co has developed and launched raltegravir, an HIV-1 integrase inhibitor for the treatment of HIV-1 infection in treatment-experienced adult patients who have evidence of viral replication and HIV-1 strains resistant to multiple antiretroviral agents. This drug is the lead from a series of integrase strand transfer inhibitors and, by April 2008, it had been launched in Canada, the US, the UK, France, Germany and Spain, and had been filed for approval in Japan.

Discovery and Synthesis of HIV Integrase Inhibitors: Development of Potent and Orally Bioavailable N-Methyl Pyrimidones

The human immunodeficiency virus type-1 (HIV-1) encodes three enzymes essential for viral replication: a reverse transcriptase, a protease, and an integrase. The latter is responsible for the integration of the viral genome into the human genome and, therefore, represents an attractive target for chemotherapeutic intervention against AIDS. A drug based on this mechanism has not yet been approved. Benzyl-dihydroxypyrimidine-carboxamides were discovered in our laboratories as a novel and metabolically stable class of agents that exhibits potent inhibition of the HIV integrase strand transfer step. Further efforts led to very potent compounds based on the structurally related N-Me pyrimidone scaffold. One of the more interesting compounds in this series is the 2-N-Me-morpholino derivative 27a, which shows a CIC95 of 65 nM in the cell in the presence of serum. The compound has favorable pharmacokinetic properties in three preclinical species and shows no liabilities in several counterscreening assays.

Safety, Tolerability, and Pharmacokinetics of Raltegravir After Single and Multiple Doses in Healthy Subjects

Raltegravir is a novel human immunodeficiency virus-1 integrase inhibitor with potent in vitro activity (95% inhibitory concentration (IC95)=33 nM in 50% human serum). Three double-blind, randomized, placebo-controlled, pharmacokinetic, safety, and tolerability studies were conducted: (1) single-dose escalation study (10-1,600 mg), (2) multiple-dose escalation study (100-800 mg q12 h x 10 days), and (3) single-dose female study (400 mg). Raltegravir was rapidly absorbed with a terminal half-life (t1/2) approximately 7-12 h. Approximately 7-14% of raltegravir was excreted unchanged in urine. Area under the curve (AUC)(0-infinity) was similar between male and female subjects. After multiple-dose administration, steady state was achieved within 2 days; there was little to modest accumulation of raltegravir. Trough levels were >33 nM for dose levels of 100 mg and greater. Raltegravir is generally well tolerated at doses of up to 1,600 mg/day given for up to 10 days and exhibits a pharmacokinetic profile supportive of twice-daily dosing with multiple doses of 100 mg and greater achieving trough levels >33 nM.

Dihydroxypyridopyrazine-1,6-dione HIV-1 integrase inhibitors

A series of potent novel dihydroxypyridopyrazine-1,6-dione HIV-1 integrase inhibitors was identified. These compounds inhibited the strand transfer process of HIV-1 integrase and viral replication in cells. Compound 6 is active against replication of HIV with a CIC(95) of 0.31 microM and exhibits no shift in potency in the presence of 50% normal human serum. It displays a good pharmacokinetic profile when dosed in rats and no covalent binding with microsomal proteins in both in vitro and in vivo models.

Metabolism and Disposition in Humans of Raltegravir (MK-0518), an Anti-AIDS Drug Targeting the Human Immunodeficiency Virus 1 Integrase Enzyme

Raltegravir is a potent human immunodeficiency virus 1 (HIV-1) integrase strand transfer inhibitor that is being developed as a novel anti-AIDS drug. The absorption, metabolism, and excretion of raltegravir were studied in healthy volunteers after a single oral dose of 200 mg (200 microCi) of [(14)C]raltegravir. Plasma, urine, and fecal samples were collected at specified intervals up to 240 h postdose, and the samples were analyzed for total radioactivity, parent compound, and metabolites. Radioactivity was eliminated in substantial amounts in both urine (32%) and feces (51%). The elimination of radioactivity was rapid, since the majority of the recovered dose was attributable to samples collected through 24 h. In extracts of urine, two components were detected and were identified as raltegravir and the glucuronide of raltegravir (M2), and each accounted for 9% and 23% of the dose recovered in urine, respectively. Only a single radioactive peak, which was identified as raltegravir, was detected in fecal extracts; raltegravir in feces is believed to be derived, at least in part, from the hydrolysis of M2 secreted in bile, as demonstrated in rats. The major entity in plasma was raltegravir, which represented 70% of the total radioactivity, with the remaining radioactivity accounted for by M2. Studies using cDNA-expressed UDP-glucuronosyltransferases (UGTs), form-selective chemical inhibitors, and correlation analysis indicated that UGT1A1 was the main UGT isoform responsible for the formation of M2. Collectively, the data indicate that the major mechanism of clearance of raltegravir in humans is UGT1A1-mediated glucuronidation.

Dihydroxypyrimidine-4-carboxamides as novel potent and selective HIV integrase inhibitors

Human immunodeficiency virus type-1 (HIV-1) integrase, one of the three constitutive viral enzymes required for replication, is a rational target for chemotherapeutic intervention in the treatment of AIDS that has also recently been confirmed in the clinical setting. We report here on the design and synthesis of N-benzyl-5,6-dihydroxypyrimidine-4-carboxamides as a class of agents which exhibits potent inhibition of the HIV-integrase-catalyzed strand transfer process. In the current study, structural modifications on these molecules were made in order to examine effects on HIV-integrase inhibitory potencies. One of the most interesting compounds for this series is 2-[1-(dimethylamino)-1-methylethyl]-N-(4-fluorobenzyl)-5,6-dihydroxypyrimidine-4-carboxamide 38, with a CIC95 of 78 nM in the cell-based assay in the presence of serum proteins. The compound has favorable pharmacokinetic properties in preclinical species (rats, dogs, and monkeys) and shows no liabilities in several counterscreening assays, highlighting its potential as a clinically useful antiviral agent.

Role of integrase inhibitors in the treatment of HIV disease

The introduction of highly active antiretroviral therapy (HAART) has produced a dramatic reduction in HIV-related mortality and morbidity among populations with widespread access to drugs. However, the increase in mutated HIV strains with reduced susceptibility to antiretroviral agents and the emergence of HAART-related side effects make it necessary to develop novel compounds characterized by activity against resistant viruses, a high genetic barrier to resistance and favorable pharmacokinetic and toxicity profiles. Integrase is a key enzyme in the life cycle of HIV and has represented an appealing target of antiretroviral therapy for several years. In 2006, after more than a decade of advances, pitfalls and disappointments, large clinical trials with integrase inhibitors in HIV-positive subjects have eventually begun.

4,5-dihydroxypyrimidine carboxamides and N-alkyl-5-hydroxypyrimidinone carboxamides are potent, selective HIV integrase inhibitors with good pharmacokinetic profiles in preclinical species

The dihydroxypyrimidine carboxamide 4a was discovered as a potent and selective HIV integrase strand transfer inhibitor. The optimization of physicochemical properties, pharmacokinetic profiles, and potency led to the identification of 13 in the dihydroxypyrimidine series and 18 in the N-methylpyrimidinone series having low nanomolar activity in the cellular HIV spread assay in the presence of 50% normal human serum and very good pharmacokinetics in preclinical species.

Antiretroviral Activity, Pharmacokinetics, and Tolerability of MK-0518, a Novel Inhibitor of HIV-1 Integrase, Dosed As Monotherapy for 10 Days in Treatment-Naive HIV-1-Infected Individuals

BACKGROUND

MK-0518 is a novel HIV-1 integrase strand transfer inhibitor with potent in vitro activity against HIV-1 (95% inhibitory concentration [IC95] = 33 nM in 50% human serum) and good bioavailability in uninfected subjects. This study explored the antiretroviral activity and safety of MK-0518 versus placebo for 10 days as monotherapy in antiretroviral therapy-naive HIV-1-infected patients with plasma HIV-1 RNA levels of at least 5000 copies/mL and CD4 T-cell counts of at least 100 cells/mm.

METHODS

This was a multicenter, double-blind, randomized, placebo-controlled 2-part study, with the first part using MK-0518 in 1 of 4 doses (100, 200, 400, and 600 mg) versus placebo (randomized 1:1:1:1:1) given twice daily for 10 days of monotherapy. Patients were monitored for safety, pharmacokinetic parameters, and antiretroviral effect.

RESULTS

Thirty-five patients were enrolled (6-8 patients per treatment group) and completed 10 days of therapy; the mean baseline log10 HIV RNA level ranged from 4.5 to 5.0 copies/mL in each group. On day 10, the mean decrease from baseline in the log10 HIV RNA level was -0.2 copies/mL for the placebo group and -1.9, -2.0, -1.7 and -2.2 log10 copies/mL for the MK-0518 100-, 200-, 400-, and 600-mg treatment groups, respectively. All dose groups had superior antiretroviral activity compared with placebo (P < 0.001 for comparison of each dose with placebo). At least 50% of patients in each MK-0518 dose group achieved an HIV RNA level <400 copies/mL by day 10. Mean trough MK-0518 concentrations at each dose exceeded the IC95 of 33 nM. Study therapy was generally well tolerated. The most common adverse experiences were headache and dizziness; these were similar between active and control groups. There were no discontinuations because of adverse experiences and no serious adverse experiences.

CONCLUSIONS

MK-0518 showed potent antiretroviral activity as short-term monotherapy and was generally well tolerated at all doses. Based on these results, part 2 of the study, a dose-ranging 48-week trial of MK-0518 versus efavirenz in a combination regimen, has been initiated.

A potent and orally active HIV-1 integrase inhibitor

A 1,6-naphthyridine inhibitor of HIV-1 integrase has been discovered with excellent inhibitory activity in cells, good pharmacokinetics, and an excellent ability to inhibit virus with mutant enzyme.

The clinical pharmacology of antiretrovirals in development

Drugs in development for the management of HIV type 1 (HIV-1) infection include agents in existing classes and agents of novel classes. Of existing classes, new protease inhibitors, nucleoside reverse transcriptase inhibitors and non-nucleoside reverse transcriptase inhibitors are in development. Novel therapeutic approaches include the development of chemokine receptor (CCR)5 antagonists, integrase inhibitors and maturation inhibitors. CCR5 antagonists are thought to inhibit HIV-1 entry into host cells by occupying a specific site on the CCR5 receptor, preventing attachment of the HIV-1 envelope protein gp120. Integrase inhibitors are small synthetically prepared molecules that block RNA/DNA interactions and modify protein or enzyme synthesis. Data on the pharmacokinetics and pharmacodynamics of these new antiretroviral agents continue to generate interest. This review reports the known data on the pharmacokinetics of experimental antiretrovirals, and describe the main drug-drug interactions studied so far.

Pharmacokinetics and metabolism of 1,5-dicaffeoylquinic acid in rats following a single intravenous administration

1,5-Dicaffeoylquinic acid (1,5-DCQA) is a potentially important HIV-1 integrase inhibitor widely distributed in many plants. To characterize the pharmacokinetic and metabolic properties of 1,5-DCQA in rats following single intravenous administration (160 mg/kg), the plasma concentrations of 1,5-DCQA were measured by high-performance liquid chromatography (HPLC) and the metabolites formed in urine were identified by liquid chromatography-mass spectrometry (LC-MS) in parallel to diode-array detection (DAD). The results showed that the concentrations of 1,5-DCQA in plasma declined rapidly in a biphasic manner with a mean terminal half-life (t(1/2)) of 1.40 h. The mean clearance (CL) and the apparent volume of distribution (Vd(B)) of 1,5-DCQA were 0.44l/h/kg and 0.89l/kg, respectively. A total of 15 metabolites in rat urine were identified, including four isomeric O-mono-methylated (M1-M4), six isomeric O-di-methylated (M5-M10), one isomeric O-mono-methyl-glucuronidated (M11) and four isomeric O-di-methyl-glucuronidated (M12-M15) metabolites. The O-methylation positions of three important metabolites (M1, M2 and M5) were determined (3''-, 3'-, and 3',3''-) by comparing with synthesized standards. These results suggested that the disappearance of 1,5-DCQA from plasma was rapid, and that its quick urinary excretion and extensive metabolism, including methylation and glucuronidation, were two factors causing its rapid elimination from the circulation.

A series of 5-(5,6)-dihydrouracil substituted 8-hydroxy-[1,6]naphthyridine-7-carboxylic acid 4-fluorobenzylamide inhibitors of HIV-1 integrase and viral replication in cells

Introduction of a 5,6-dihydrouracil functionality in the 5-position of N-(4-fluorobenzyl)-8-hydroxy-[1,6]naphthyridine-7-carboxamide 1 led to a series of highly active HIV-1 integrase inhibitors. These compounds displayed low nanomolar activity in inhibiting both the strand transfer process of HIV-1 integrase and viral replication in cells. Compound 11 is a 150-fold more potent antiviral agent than 1, with a CIC(95) of 40 nM in the presence of human serum. It displays good pharmacokinetics when dosed in rats and dogs.

Single-dose hemodynamic toxicity and pharmacokinetics of a partial phosphorothioate anti-HIV oligonucleotide (AR177) after intravenous infusion to cynomolgus monkeys

5' GTGGTGGGTGGGTGGGT-3' (AR177) is a 17-mer oligonucleotide with anti-human immunodeficiency virus (HIV) activity that is composed of a phosphodiester backbone and single phosphorothioate linkages at the 3' and 5' ends. A hemodynamic toxicity study was conducted in which cynomolgus monkeys were infused i.v. over a 10-minute period with single doses of 5, 20 or 50 mg AR177/kg or saline. Blood pressure, ECG, clinical chemistry, hematology, complement factors, coagulation parameters and the AR177 plasma concentration were determined. AR177 did not cause any mortality in this study, nor did it cause changes in blood pressure, ECG, clinical chemistry or hematology parameters at any dose. There was a minimal, dose-dependent increase in the levels of complement split product Bb and total hemolytic complement. There was a significant dose-dependent and reversible inhibition of coagulation with the 20- and 50-mg/kg doses that lasted up to several hours after infusion. The time course of the inhibition of coagulation closely matched the plasma levels of AR177. There was a no-effect plasma AR177 concentration vs. activated partial thromboplastin time of approximately 60 to 100 micrograms AR177/ml, above which there was prolongation of activated partial thromboplastin time. These data demonstrate that AR177 does not cause significant hemodynamic toxicity at the doses studied and that this drug could be administered as a rapid infusion without any acute, life-threatening effects at doses that produce plasma concentrations that have shown anti-HIV activity in vitro.

Repeat-dose toxicity and pharmacokinetics of a partial phosphorothioate anti-HIV oligonucleotide (AR177) after bolus intravenous administration to cynomolgus monkeys

5'GTGGTGGGTGGGTGGGT-3' (AR177) is a partial phosphorothioate, 17-mer oligonucleotide that has been shown to have anti-human immunodeficiency virus (HIV) activity in vitro and to be a potent inhibitor of HIV-1 integrase. A repeat-dose toxicity and pharmacokinetic study was conducted in which cynomolgus monkeys were given bolus i.v. injections of 2.5, 10 or 40 mg AR177/kg/day every other day for a total of 12 doses. Control monkeys received saline. ECG, clinical chemistry, hematology, coagulation parameters, histopathology and the AR177 plasma concentration were evaluated. AR177 did not cause any mortality in this study, nor did it cause changes in ECG, clinical chemistry, hematology values or histology. However, there was a dose-dependent inhibition of coagulation measured by a prolongation of activated partial thromboplastin time; this inhibition was reversible with drug washout. Analysis of plasma samples by HPLC demonstrated that there was no difference between the AR177 plasma concentrations that were achieved after the 1st and 12th (last) doses of 2.5, 10 or 40 mg/kg. There was a direct relationship between the AR177 plasma concentration and activated partial thromboplastin time. These results indicate that repeated bolus i.v. administration of AR177 to cynomolgus monkeys at doses as high as 40 mg/kg was well tolerated and was not associated with the serious cardiovascular responses previously observed with other oligonucleotides administered i.v.