Low-doses of indinavir boosted with ritonavir in HIV-infected Thai patients: pharmacokinetics, efficacy and tolerability

Low-dose ritonavir-boosted darunavir in virologically suppressed HIV-1-infected adults: an open-label trial (ANRS 165 Darulight)

Objectives

To assess whether low-dose ritonavir-boosted darunavir (darunavir/r) in combination with two NRTIs could maintain virological suppression in patients on a standard regimen of darunavir/r + two NRTIs.

Design

A multicentre, Phase II, non-comparative, single-arm, open-label study.

Setting

Tertiary care hospitals in France.

Subjects

One hundred HIV-1-infected adults with no darunavir or NRTI resistance-associated mutations (RAMs) and a plasma HIV RNA level ≤50 copies/mL for ≥12 months on once-daily darunavir/r (800/100 mg) + two NRTIs for ≥6 months were switched to darunavir/r 400/100 mg with the same NRTIs.

Primary outcome measure

Proportion of patients with treatment success: plasma HIV RNA level ≤50  copies/mL up to 48 weeks without any change in the study regimen, in a modified ITT (mITT) analysis.

Results

At baseline, most patients were male (78%), with a median age of 43 years, median duration of HIV RNA ≤50 copies/mL of 35 months and median CD4 T cell count of 633 cells/mm3. Seventy-six percent received tenofovir/emtricitabine and 24% abacavir/lamivudine. Five patients were excluded from the mITT analysis. The rate of treatment success through to week 48 was 91.6% (87/95; 95% CI 84.1%-96.3%). No RAM was detected in three amplifiable genotypes. A total of 212 adverse events (AEs) occurred in 64 patients (64%); 9 AEs were serious, none leading to treatment discontinuation.

Conclusions

In HIV-infected patients well suppressed with darunavir/r (800/100 mg) and two NRTIs, a reduction of the darunavir dose to 400 mg/day maintained virological efficacy and was safe over 48 weeks.

Reduced indinavir exposure during pregnancy

AIM

To describe the pharmacokinetics and safety of indinavir boosted with ritonavir (IDV/r) during the second and third trimesters of pregnancy and in the post-partum period.

METHODS

IMPAACT P1026s is an on-going, prospective, non-blinded study of antiretroviral pharmacokinetics (PK) in HIV-infected pregnant women with a Thai cohort receiving IDV/r 400/100 mg twice daily during pregnancy through to 6-12 weeks post-partum as part of clinical care. Steady-state PK profiles were performed during the second (optional) and third trimesters and at 6-12 weeks post-partum. PK targets were the estimated 10(th) percentile IDV AUC (12.9 μg ml(-1)h) in non-pregnant historical Thai adults and a trough concentration of 0.1 μg ml(-1), the suggested minimum target.

RESULTS

Twenty-six pregnant women were enrolled; thirteen entered during the second trimester. Median (range) age was 29.8 (18.9-40.8) years and weight 60.5 (50.0-85.0) kg at the third trimester PK visit. The 90% confidence limits for the geometric mean ratio of the indinavir AUC(0,12 h) and Cmax during the second trimester and post-partum (ante : post ratios) were 0.58 (0.49, 0.68) and 0.73 (0.59, 0.91), respectively; third trimester/post-partum AUC(0,12 h) and Cmax ratios were 0.60 (0.53, 0.68) and 0.63 (0.55, 0.72), respectively. IDV/r was well tolerated and 21/26 women had a HIV-1 viral load < 40 copies ml(-1) at delivery. All 26 infants were confirmed HIV negative.

CONCLUSION

Indinavir exposure during the second and third trimesters was significantly reduced compared with post-partum and ∼30% of women failed to achieve a target trough concentration. Increasing the dose of IDV/r during pregnancy to 600/100 mg twice daily may be preferable to ensure adequate drug concentrations.

Pharmacokinetic optimization of antiretroviral therapy in pregnancy

Antiretroviral therapy suppresses replication of HIV allowing restoration and/or preservation of the immune system. Providing combination antiretroviral therapy during pregnancy can treat maternal HIV infection and/or reduce perinatal HIV transmission. However, providing treatment to pregnant women is challenging due to physiological changes that can alter antiretroviral pharmacokinetics. Suboptimal drug exposure can result in HIV RNA rebound, the selection of resistant virus or an increased risk of HIV-1 transmission to the infant. Increased drug exposure can produce unwarranted maternal adverse effects and/or fetal toxicity. Subsequently, dose adjustments may be necessary during pregnancy to achieve comparable antiretroviral exposure to non-pregnant adults. For several antiretrovirals, systemic exposure is decreased during the last trimester of pregnancy. By 6-12 weeks postpartum, concentrations return to those prior to pregnancy. Also, the extent of antiretroviral placental transfer to the fetus and degree of antiretroviral excretion into breast milk varies within, and between, antiretroviral drug classes. It is necessary to consider the pharmacological characteristics of each antiretroviral when optimizing combination therapy during pregnancy to treat maternal HIV infection and prevent perinatal HIV transmission.

Pharmacokinetics and 48 week efficacy of adjusted dose indinavir/ritonavir in rifampicin-treated HIV/tuberculosis-coinfected patients: a pilot study

HIV/tuberculosis (HIV/TB)-coinfected patients intolerant/resistant to nonnucleoside reverse transcriptase inhibitors (NNRTIs) have limited treatment options. We evaluated the pharmacokinetics (PK)/safety/efficacy of an adjusted dose of indinavir/ritonavir (IDV/r) 600/100 mg plus two NRTIs in HIV/TB-coinfected Thais receiving rifampicin-based anti-TB treatment. This was a prospective, open-label study. Eighteen Thai, HIV/TB-coinfected patients between 18 and 60 years were recruited. IDV/r 600 mg/100 mg plus lamivudine and stavudine were administered every 12 h (bid). When rifampicin was stopped, IDV/r was reduced to 400/100 mg BID. Clinical outcomes, adverse events, and concomitant drugs were intensively collected. Intensive 12-h PK was performed after 2 weeks of IDV/r while on rifampicin. Samples were collected: predosing and 1, 2, 3, 4, 6, 8, 10, and 12 h after drug intake. The median body weight was 55 kg. The median CD4 was 26 cells/μl. The median HIV RNA was 5.05 log(10) copies/ml. Then 15/18 underwent intensive PK at week 2. The median time between initiating rifampicin and IDV/r was 4.5 months. The median duration of rifampicin during study (rifampicin/IDV/r together) was 15.6 weeks. All received a total of 9 months of antituberculous drugs. The geometric means (GM) of indinavir AUC(0-12) and C(12) were 8.11 mg*h/liter and 0.03 mg/liter, respectively. After stopping rifampicin and reducing IDV/r to 400/100 bid, the GM indinavir C(12) increased to 0.68 mg/liter (p=0.004). In all, 8/18 (44%) had asymptomatic ALT elevation and 2/18 (11%) had symptomatic hepatotoxicity requiring IDV/r discontinuation. All 13 patients who remained on IDV/r treatment had HIV RNA <50 copies/ml at 48 weeks. Concomitant use of rifampicin and IDV/r resulted in subtherapeutic indinavir concentrations. Although 44% of them developed asymptomatic Grade 3/4 transaminitis, the rate of study drug discontinuation due to hepatotoxicity was low. Despite good virological outcome in our cohort, prolonged exposure to subtherapeutic indinavir concentrations may lead to treatment failure.

Activity of human immunodeficiency virus type 1 protease inhibitors against the initial autocleavage in Gag-Pol polyprotein processing

Inhibitors of HIV protease have proven to be important drugs in combination anti-HIV therapy. These inhibitors were designed to target mature protease and prevent viral particle maturation by blocking Gag and Gag-Pol processing by mature protease. Currently there are few data assessing the ability of these protease inhibitors to block the initial step in autoproteolytic processing of Gag-Pol. This unique step involves the dimerization of two Gag-Pol polyproteins and autocleavage of the Gag-Pol polyprotein by the embedded dimeric protease. We developed a plasmid encoding a modified form of Gag-Pol that can undergo autoprocessing only at the initial cleavage site between p2 and nucleocapsid. Using an in vitro transcription/translation system, we assessed the ability of six different approved protease inhibitors (darunavir, indinavir, nelfinavir, ritonavir, saquinavir, and tipranavir) to block this initial autocleavage step. Of these inhibitors, darunavir and saquinavir were the most effective. Darunavir and saquinavir were also the most effective at blocking the initial autoprocessing of full-length Gag-Pol in HIV-1-infected T cells. Thus, we have identified at least two HIV-1 protease inhibitors that have activity against the primary autocatalytic step of the embedded HIV-1 protease in Gag-Pol at concentrations that may be attained in HIV-1-infected patients. Due to unique aspects of the initial processing step, it may be possible to develop inhibitors with greater potency against this step, thus halting viral maturation at the earliest stages. The transcription/translation assay could be used to develop more potent inhibitors of this essential first step in viral maturation.

Influence of body weight on achieving indinavir concentrations within its therapeutic window in HIV-infected Thai patients receiving indinavir boosted with ritonavir

Indinavir boosted with ritonavir (IDV/r) dosing with 400/100 mg, twice daily, is preferred in Thai adults, but this dose can lead to concentrations close to the boundaries of its therapeutic window. The objectives of this analysis were to validate a population pharmacokinetic model to describe IDV/r concentrations in HIV-infected Thai patients and to investigate the impact of patient characteristics on achieving adequate IDV concentrations. IDV/r concentration data from 513 plasma samples were available. Population means and variances of pharmacokinetic parameters were estimated using a nonlinear mixed effects regression model (NONMEM Version VI). Monte Carlo simulations were performed to estimate the probability of achieving IDV concentrations within its therapeutic window. IDV/r pharmacokinetics were best described by a one-compartment model coupled with a single transit compartment absorption model. Body weight influenced indinavir apparent oral clearance and volume of distribution and allometric scaling significantly reduced the interindividual variability. Final population estimates (interindividual variability in percentage) of indinavir apparent oral clearance and volume of distribution were 21.3 L/h/70 kg (30%) and 90.7 L/70 kg (22%), respectively. Based on model simulations, the probability of achieving an IDV trough concentration greater than 0.1 mg/L was greater than 99% for 600/100 mg and greater than 98% for 400/100 mg, twice daily, in patients weighing 40 to 80 kg. However, the probability of achieving IDV concentrations associated with an increased risk of drug toxicity (greater than 10.0 mg/L) increased from 1% to 10% with 600/100 mg compared with less than 1% with 400/100 mg when body weight decreased from 80 to 40 kg. The validated model developed predicts that 400/100 mg of IDV/r, twice daily, provides indinavir concentrations within the recommended therapeutic window for the majority of patients. The risk of toxic drug concentrations increases rapidly with IDV/r dose of 600/100 mg for patients less than 50 kg and therapeutic drug monitoring of IDV concentrations would help to reduce the risk of IDV-induced nephrotoxicity.

Cutaneous toxicities of antiretroviral therapy for HIV: part I. Lipodystrophy syndrome, nucleoside reverse transcriptase inhibitors, and protease inhibitors

Antiretroviral medications for the treatment of HIV are common drugs with diverse and frequent skin manifestations. Multiple new cutaneous effects have been recognized in the past decade. Dermatologists play an important role in accurately diagnosing and managing the cutaneous toxicities of these medications, thereby ensuring that a patient has as many therapeutic options as possible for life-long viral suppression. Part I of this two-part series on the cutaneous adverse effects of antiretroviral medications will discuss HIV-associated lipodystrophy syndrome, which can be seen as a result of many antiretroviral medications for HIV, and the specific cutaneous effects of the nucleoside reverse transcriptase inhibitors and protease inhibitors.

Antiretroviral therapy with a twice-daily regimen containing 400 milligrams of indinavir and 100 milligrams of ritonavir in human immunodeficiency virus type 1-infected women during pregnancy

We evaluated the safety and efficacy of a twice daily regimen containing 400 mg of indinavir and 100 mg of ritonavir in 32 human immunodeficiency virus (HIV)-infected women during pregnancy. The median indinavir trough concentration was 208 ng/ml during the third trimester. At delivery, 26 of 28 women on indinavir-ritonavir had HIV RNA levels of <200 copies/ml. No infant was HIV infected. These data are encouraging for the use of this combination for prevention of mother-to-child transmission of HIV.

Second-line combination antiretroviral therapy in resource-limited settings: facing the challenges through clinical research

Combination antiretroviral therapy (ART) has dramatically altered the prognosis of individuals infected with HIV. In the past 5 years there has been a concerted effort to increase access to ART in the developing world. The evidence to date suggests that adherence to therapy and clinical outcomes in developing world programmes are at least the equal of those observed in developed countries. Although access to first-line therapy is reasonably well established, there is a substantial and unacceptable mortality rate in the first 6 months after initiation of ART, particularly in those with low CD4 cell counts and late-stage disease. Failure of first-line ART is inevitable in a proportion of patients. Access to second-line ART regimens in developing countries is problematic, mainly because of the expense of HIV protease inhibitors (PIs). Access to second-line ART may be facilitated by novel strategies using the existing recommended agents or by the use of new agents or classes. Refinement of programmes in the developing world must be underpinned by the same rigorous scientific research effort that has characterized the success of the effort in the developed world. Therefore, the funding bodies responsible for the roll-out of antiretroviral access across the globe must mandate, incorporate and fund clinical research as an intrinsic aspect of combination ART roll-out programmes.

Indinavir/ritonavir remains an important component of HAART for the treatment of HIV/AIDS, particularly in resource-limited settings

For over a decade, indinavir has been approved for the treatment of HIV/AIDS; however, following the introduction of new protease inhibitors (PIs) with improved safety and pharmacologic profiles, its use in developed countries has become almost obsolete. In contrast, in resource-limited settings where the majority of people living with HIV/AIDS reside, indinavir is part of the most affordable PI-based highly active antiretroviral treatment regimen. A major drawback of indinavir use is renal toxicity, but low-dose indinavir plus ritonavir (400/100 mg) twice daily is both efficacious and tolerable. Similar low dosing levels in children have also proven successful, but data in pregnant women remains limited. Due to its low cost and proven efficacy indinavir remains a key component of HIV/AIDS treatment in resource-limited settings.

Indinavir: the forgotten HIV-protease inhibitor. Does it still have a role?

Indinavir is one of four first-generation HIV-protease inhibitors and was the most popular amongst them in the late 1990s. It was initially licensed for use alone, given three times daily, administered away from meals and together with at least 1.5 litres of fluid per day. In clinical practice, it became common for clinicians to prescribe it with a ritonavir pharmacokinetic 'boost' to remove the food restriction, reduce the pill burden and enable a more convenient twice-daily dosing schedule. However, at a ritonavir-boosted dosing schedule of indinavir/ritonavir 800/100 mg b.i.d., the regimen proved toxic and poorly tolerable, and its use diminished as newer, better tolerated PIs became available. Recent research has suggested that ritonavir-boosted indinavir administered at lower doses, particularly indinavir/ritonavir 400/100 mg b.i.d., retains potency and is considerably less toxic. As a result, there is interest in its application in resource-constrained settings.

Efficacy and plasma concentrations of indinavir when boosted with ritonavir in human immunodeficiency virus-infected Thai children

We evaluated 19 children using 220-300 mg/m of indinavir (IDV) boosted with 100 mg ritonavir (RTV) (n = 12) or full-dose RTV (n = 7). Geometric mean (GM) (90% confidence interval, CI) of IDV Ctrough in children who took IDV with 100 mg RTV (n = 12) was 0.17 (0.06-0.50) mg/L. For children who took IDV with full-dosage RTV, GM (90% CI) was 0.40 (0.10-1.61) mg/L. C2hours were less than 10 mg/L in all subjects. Eighteen children had good virologic response. This report demonstrates that smaller IDV dosages given with RTV provide efficacious plasma concentrations and can be safely used.

Efficacy and Safety of Indinavir/Ritonavir 400/100 mg Twice Daily plus Two Nucleoside Analogues in Treatment-Naive HIV-1-Infected Patients with CD4+ T-cell Counts <200 cells/mm3: 96-Week Outcomes

Objective

To evaluate the efficacy and safety of indinavir/ritonavir 400/100 mg plus stavudine and lamivudine twice daily in antiretroviral-therapy-naive Thai HIV-1-infected patients.

Methods

This was an open-label, non-randomized single arm study. Antiretroviral-naive patients ( n=80) with CD4+ cell count <200x106/l were started on stavudine and lamivudine plus indinavir/ritonavir 400/100mg twice daily. CD4+ cell count and HIV RNA were determined at week 0, 12, 24, 48 and 96. HIV RNA was measured to a level of 50 copies/ml by RT-PCR assay. Primary analysis was statistically performed as intent to treat. The primary endpoint was the percentage of patients with plasma HIV RNA below 50 copies/ml at week 96.

Result

Eighty antiretroviral-therapy-naive patients with median CD4+ cell count 19x106/l (range: 2-197x106/l) and median baseline plasma HIV RNA of 174,000 copies/ml (range 16,800–750,000 copies/ml) were enrolled. In the intent-to-treat analysis at week 96, the proportion of patients with HIV RNA of <50 copies/ml was 68.8% (95% confidence interval [CI]: 68.3-69.3), whereas it was 88.7% (95% CI: 88.1-89.3) in the on-treatment analysis at week 96. The regimen was well tolerated. Hyperglycaemia, hypercholesterolaemia and hypertriglyceridaemia were found in 8.3, 33.3 and 37.0% of the patients, respectively. Treatment was stopped in 18 patients; two from intolerance, two switched therapy, four as a result of serious adverse event-related death, and ten were lost to follow-up.

Conclusion

Our study demonstrates that indinavir/ritonavir 400/100 mg plus stavudine and lamivudine twice daily, the least expensive boosted protease inhibitor, appears to be effective and safe up to 96 weeks despite high baseline viraemia and low CD4+ cell count in antiretroviral-naive patients.