Etravirine: clinical review of a treatment option for HIV type-1-infected patients with non-nucleoside reverse transcriptase inhibitor resistance

Antiretroviral Resistance After First-Line Antiretroviral Therapy Failure in Diverse HIV-1 Subtypes in the SECOND-LINE Study

We investigate mutations and correlates according to HIV-1 subtype after virological failure (VF) of standard first-line antiretroviral therapy (ART) (non-nucleoside/nucleotide reverse transcriptase inhibitor [NNRTI] +2 nucleoside/nucleotide reverse transcriptase inhibitor [N(t)RTI]). SECOND-LINE study participants were assessed at baseline for HIV-1 subtype, demographics, HIV-1 history, ART exposure, viral load (VL), CD4(+) count, and genotypic ART resistance. We used backward stepwise multivariate regression (MVR) to assess associations between baseline variables and presence of ≥3 N(t)RTI mutations, ≥1 NNRTI mutation, ≥3 thymidine analog-N(t)RTI [ta-N(t)RTI] mutations (TAMs), the K65/K70 mutation, and predicted etravirine (ETV)/rilpivirine (RPV) activity. The inclusion p-value for MVR was p < .2. The exclusion p-value from stepwise elimination was p > .05. Of 541 participants, 491 (91%) had successfully characterized baseline viral isolates. Subtype distribution: B (n = 123, 25%), C (n = 202, 41%), CRF01_AE (n = 109, 22%), G (n = 25, 5%), and CRF02_AG (n = 27, 5%). Baseline CD4(+) 200-394 cells/mm(3) were associated with <3 N(t)RTI mutations (OR = 0.47; 95% CI 0.29-0.77; p = .003), absence of the K65/K70 mutation (OR = 0.43; 95% CI 0.26-0.73; p = .002), and higher ETV sensitivity (OR = 0.52; 95% CI 0.35-0.78; p = .002). Recent tenofovir (TDF) use was associated with K65/K70 mutations (OR = 8.91; 95% CI 5.00-15.85; p < .001). Subtype CRF01_AE was associated with ≥3 N(t)RTI mutations (OR = 2.34; 95% CI 1.31-4.17; p = .004) and higher RPV resistance (OR = 2.13; 95% CI 1.30-3.49; p = .003), and subtype C was associated with <3 TAMs (OR = 0.45; 95% CI 0.21-0.99; p = .015). Subtypes CRF01_AE (OR = 2.46; 95% CI 1.26-4.78; p = .008) and G (OR = 4.77; 95% CI 1.44-15.76; p = .01) were associated with K65/K70 mutations. Higher VL at confirmed first-line VF was associated with ≥3 N(t)RTI mutations (OR = 1.39; 95% CI 1.07-1.78; p = .013) and ≥3 TAMs (OR = 1.62; 95% CI 1.15-2.29; p = .006). The associations of first-line resistance mutations across the HIV-1 subtypes in this study are consistent with knowledge derived from subtype B, with some exceptions. Patterns of resistance after failure of a first-line ta-N(t)RTI regimen support using TDF in N(t)RTI-containing second-line regimens, or using N(t)RTI-sparing regimens.

Drug susceptibility to etravirine and darunavir among Human Immunodeficiency Virus Type 1-derived pseudoviruses in treatment-experienced patients with HIV/AIDS in South Korea

Background

In South Korea, about 20 types of antiretroviral drugs are used in the treatment of patients with human immunodeficiency virus/acquired immune deficiency syndrome. Since 2010, raltegravir, etravirine, and darunavir have been spotlighted as new drugs for highly active antiretroviral therapy (HAART)-experienced adults with resistant HIV-1 in South Korea. In this study, we investigated potential susceptibility of pseudoviruses derived from treatment-experienced Korean patients to etravirine vs efavirenz and to darunavir vs amprenavir and indinavir using a modified single-round assay.

Methods

Pseudoviruses derived from nine treatment-experienced patients infected with HIV-1 were investigated by comparison with the wild-type strain pNL4-3. The 50% inhibitory concentration (IC₅₀) values were calculated and drug susceptibility was compared. The intensity of genotypic drug resistance was classified based on the ‘SIR’ interpretation of the Stanford data base.

Results

Drug susceptibility was generally higher for etravirine and darunavir compared with efavirenz, amprenavir, and indinavir in pseudoviruses derived from treatment-experienced patients. Pseudoviruses derived from patients KRB4025 and KRB8014, who exhibited long-term use of protease inhibitors, showed an outside of tested drug concentration, especially for amprenavir and indinavir. However, they exhibited a lower fold-change in resistance to darunavir.

Conclusions

Etravirine and darunavir have been used in HAART since 2010 in South Korea. Therefore, these antiretroviral drugs together with other newly introduced antiretroviral drugs are interesting for the optimal treatment of patients with treatment failure. This study may help to find a more effective HAART in the case of HIV-1 infected patients that have difficulty being treated.

Current perspectives on HIV-1 antiretroviral drug resistance

Current advancements in antiretroviral therapy (ART) have turned HIV-1 infection into a chronic and manageable disease. However, treatment is only effective until HIV-1 develops resistance against the administered drugs. The most recent antiretroviral drugs have become superior at delaying the evolution of acquired drug resistance. In this review, the viral fitness and its correlation to HIV-1 mutation rates and drug resistance are discussed while emphasizing the concept of lethal mutagenesis as an alternative therapy. The development of resistance to the different classes of approved drugs and the importance of monitoring antiretroviral drug resistance are also summarized briefly.

New therapeutic landscape of NNRTIs for treatment of HIV: a look at recent data

INTRODUCTION

A key objective with highly active antiretroviral therapy for the treatment of HIV infection has been the optimization of antiretroviral drug combinations for individual patients.

AREAS COVERED

Overall, non-nucleoside reverse transcriptase inhibitor (NNRTI)-based regimens (in combination with two nucleoside reverse transcriptase inhibitors (NRTIs)) have become mainstays for initial ARV regimens. Early NNRTIs, efavirenz and nevirapine, are similarly efficacious, but differ according to their toxicity profiles. Newer NNRTIs, rilpivirine and etravirine are also efficacious. Etravirine was designed to overcome common first-line NNRTI resistance mutations, and serves as a second line agent.

EXPERT OPINION

As a class, NNRTIs are key components of ARV regimens. Currently, there are 3 NNRTIs that may be used in first-line regimens, and one in second-line regimens. ARV regimen optimization depends on matching individual drug efficacy, safety, resistance, and toxicity profiles to particular patients. Once-daily dosing options are essential to treatment simplification strategies, which have been shown to enhance regimen compliance and durabiltiy. These are especially important due to the low genetic barrier to resistance generally associated with NNRTIs. As newer drugs are introduced, especially as part of once-daily, single-tablet regimens, this will expand the number of convenient and efficacious treatment options available.

[Characteristics of antiretroviral drugs]

As of November 2010, a total of 22 antiretroviral agents are marketed in Spain. These agents are divided into 6 classes according to their mechanism of action: 1) nucleos(t)ide reverse transcriptase inhibitors (NRTI) (abacavir, didanosine, emtricitabine, stavudine, lamivudine, zidovudine, and tenofovir), 2) non-nucleoside reverse transcriptase inhibitors (NNRTI) (efavirenz, etravirine, and nevirapine), 3) protease inhibitors (PI) (atazanavir, darunavir, fosamprenavir, indinavir, lopinavir, nelfinavir, ritonavir, saquinavir, tipranavir), 4) entry inhibitors (enfuvirtide), 5) coreceptor CCR5 inhibitors (maraviroc), and 6) integrase inhibitors (raltegravir). All 22 agents are indicated for the treatment of HIV-1 infection in combination with other antiretroviral drugs. Most have also proven to be active against HIV-2 (except the NNRTIs, enfuvirtide, and maraviroc) and some are active against hepatitis B virus (lamivudine, emtricitabine, and tenofovir). The present article reviews the main characteristics of the different antiretroviral agents and classes, namely, commercial presentations, paediatric and adult dosages, dose adjustments in renal and hepatic insufficiency, pharmacokinetics and interactions, mechanism of action, treatment indications, resistance, adverse effects, and safety during pregnancy and breastfeeding. Some of the characteristics of antiretrovirals are class-specific and common to other agents of the same class, and others are individual and different from those of other drugs in the same class. Knowledge of these characteristics enables us to prepare efficacious therapeutic regimens according to the specific requirements of the patient (tolerability, simplicity, adaptability to lifestyle) and clinical setting (naive, simplification, rescue, resistance).

Combination antiretroviral therapy

Combination antiretroviral therapy (cART) was one of the greatest achievements in medicine in the twentieth century. It has rapidly evolved during the last 10 years from suboptimal monotherapy to an effective triple therapy that can change the natural history of HIV-1 infection from a deadly disease to a chronic, manageable condition. However, a dreadful toll of long-term toxicity was experienced by HIV-1-infected patients in the cART era. We have recently entered in a new phase of cART, in which efficacy has been increased and toxicity minimized. Currently, the greatest challenge is to make cART available to everybody who needs it with the future prospects of HIV-1 eradication.