Etravirine and rilpivirine resistance in HIV-1 subtype CRF01_AE-infected adults failing non-nucleoside reverse transcriptase inhibitor-based regimens

Delayed identification of treatment failure causes high levels of acquired drug resistance and less future drug options among HIV-1-infected South Indians

PURPOSE

HIV-1 Drug Resistance Mutations (DRMs) among Immunological failure (IF) on NRTI based first-line regimens, Thymidine analogue (TA) - AZT & D4T and Non-Thymidine Analogue (NTA) -TDF; and predict viral drug susceptibility to gain vision about optimal treatment strategies for second-line.

METHODS

Cross-sectionally, 300 HIV-1 infected patients, failing first-line HAART were included. HIV-1 pol gene spanning 20-240 codons of RT was genotyped and mutation pattern was examined, (IAS-USA 2014 and Stanford HIV drug resistance database v7.0).

RESULTS

The median age of the participants was 35 years (IQR 29-40), CD4 T cell count of TDF failures was low at 172 cells/μL (IQR 80-252), and treatment duration was low among TDF failures (24 months vs. 61 months) (p < 0.0001). Majority of the TDF failures were on EFV based first-line (89 % vs 45 %) (p < 0.0001). Level of resistance for TDF and AZT shows, that resistance to TDF was about one-third (37 %) of TDF participants and onefourth (23 %) of AZT participants; resistance to AZT was 17 % among TDF participants and 47 % among AZT participants; resistance to both AZT and TDF was significantly high among AZT participants [21 % vs. 8 %, OR 3.057 (95 % CI 1.4-6.8), p < 0.0001].

CONCLUSION

Although delayed identification of treatment failure caused high levels of acquired drug resistance in our study. Thus, we must include measures to regularize virological monitoring with integrated resistance testing in LMIC (Low and Middle Income Countries) like in India; this will help to preserve the effectiveness of ARV and ensure the success of ending AIDS as public health by 2030.

Switching protease inhibitors to rilpivirine in HIV-positive individuals with complete viral suppression and without prior HIV drug resistance in a resource-limited setting: a randomized controlled trial

Introduction

Prior to the availability of rilpivirine (RPV), patients who could not tolerate efavirenz and nevirapine (NVP) were treated with protease inhibitor (PI)‐based antiretroviral therapy (ART). Dyslipidaemia and other metabolic complications are commonly associated with PI use. This study aimed to compare the efficacy and adverse events between switching from PI‐based to RPV‐based regimen, versus continuing PI‐based regimens in HIV‐positive individuals with complete viral suppression.

Methods

A randomized controlled trial was conducted in HIV‐positive individuals receiving PI‐based regimens with undetectable HIV RNA and without prior HIV drug resistance. Patients were enrolled between July and December 2017 in a university medical centre in Bangkok, Thailand. They were randomized to switch from PIs to RPV (switch group) or continue ritonavir‐boosted PI (control group). Primary endpoint was the proportion of patients with undetectable HIV RNA at 48 weeks. Changes in CD4 cell counts, lipid profiles and adverse events were also analysed.

Results and discussion

A total of 84 patients were enrolled, 42 in each group. Mean age was 47.7 years and 53.6% were males. At 48 weeks, 95.2% of patients in the switch group and 92.9% of control group had maintained undetectable HIV RNA (difference rate 2.4%; 95% CI, −9.6 to 14.7). Means of CD4 cell counts were 611 and 641 cells/mm³ in switch and control groups respectively (p = 0.632). Mean changes in lipid profiles (switch vs. control groups) were: total cholesterol, −12.5 versus + 12.2 (p = 0.024); LDL, −3.4 versus + 6.2 (p = 0.040); HDL, +1.6 versus + 1.9 (p = 0.887); and triglycerides, −82.6 versus − 24.4 mg/dL (p = 0.031). The mean changes of glucose and eGFR were similar (p > 0.05) between the two groups. The mean change of ALT was significantly greater in switch group (18.2 vs. 4.0 U/L, p = 0.017). One patient in switch group had anorexia and elevated ALT at 14 weeks and completely recovered after RPV discontinuation.

Conclusions

Switching PIs to RPV, in patients with complete viral suppression and without prior HIV drug resistance, sustains viral suppression and yields better lipid profiles. This finding supports its use as switching therapy in patients receiving PI‐based regimens due to intolerance to efavirenz and NVP and previous alternatives limited to PI in resource‐limited settings.

Non-Nucleoside Reverse Transcriptase Inhibitors Join Forces with Integrase Inhibitors to Combat HIV

In the treatment of acquired immune deficiency syndrome (AIDS), the diarylpyrimidine (DAPY) analogs etravirine (ETR) and rilpivirine (RPV) have been widely effective against human immunodeficiency virus (HIV) variants that are resistant to other non-nucleoside reverse transcriptase inhibitors (NNRTIs). With non-inferior or improved efficacy, better safety profiles, and lower doses or pill burdens than other NNRTIs in the clinic, combination therapies including either of these two drugs have led to higher adherence than other NNRTI-containing treatments. In a separate development, HIV integrase strand transfer inhibitors (INSTIs) have shown efficacy in treating AIDS, including raltegravir (RAL), elvitegravir (EVG), cabotegravir (CAB), bictegravir (BIC), and dolutegravir (DTG). Of these, DTG and BIC perform better against a wide range of resistance mutations than other INSTIs. Nevertheless, drug-resistant combinations of mutations have begun to emerge against all DAPYs and INSTIs, attributable in part to non-adherence. New dual therapies that may promote better adherence combine ETR or RPV with an INSTI and have been safer and non-inferior to more traditional triple-drug treatments. Long-acting dual- and triple-therapies combining ETR or RPV with INSTIs are under study and may further improve adherence. Here, highly resistant emergent mutations and efficacy data on these novel treatments are reviewed. Overall, ETR or RPV, in combination with INSTIs, may be treatments of choice as long-term maintenance therapies that optimize efficacy, adherence, and safety.

Genetic diversity and antiretroviral resistance-associated mutation profile of treated and naive HIV-1 infected patients from the Northwest and Southwest regions of Cameroon

BACKGROUND

Antiretroviral therapy (ART) has improved the survival of HIV infected persons. However, rapid scale-up of ART and the high HIV-1 genetic variability, has greatly influenced the emergence of drug-resistant strains. This constitutes a potential threat to achieving the UNAIDS' 90-90-90 goals by 2020. We investigated the prevalent HIV-1 genotypes, drug resistance-associated mutations and assessed some predictors of the occurrence of these mutations.

METHODS

This was a hospital-based cross-sectional study conducted between October 2010 and June 2012. Participants were consecutively enrolled from selected HIV treatment centers of the Southwest and Northwest regions of Cameroon. Viral load was determined with the automated Abbott Real-time HIV-1 m2000rt System. HIV genotyping and antiretroviral resistance mutations analysis were performed using Bayer's HIV-1 TRUGENE™ Genotyping Kit and OpenGene DNA Sequencing system. The drug resistance mutation was interpreted with the Stanford HIV database. Epidemiological data were obtained using pre-tested semi-structured questionnaires.

RESULTS

Of the 387 participants, 239 were successfully genotyped. The median age of these participants was 33 years (interquartile range, IQR: 28-40 years), and a majority (65.7%) were female. A total of 29.3% of the participants were receiving ART. The median duration of ART was 10.5 months (IQR: 4-17.25 months). The median CD4 count and log10 viral load of study participants were 353.5 cells/ml (IQR:145-471) and 4.89 copies/ml (IQR: 3.91-5.55) respectively. CRF02 (A/G) (69%) was the most prevalent subtype followed by G (8.2%) and F (6.7%). Overall, resistance mutations were present in 37.1% of ART-experienced and 10.7% of ART-naive patients. Nucleoside reverse transcriptase inhibitors (NRTI) mutations occurred in 30% of ART-experienced and 2.4% of ART-naïve patients, while non-nucleoside reverse transcriptase inhibitors (NNRTI) mutations occurred in 34.2% of ART-experienced and 10.1% of -naïve patients. M184V (8.4%, 20/239) and K103N (5.4%, 13/239) were the most prevalent mutations. Major protease inhibitor mutations occurred in 3 (1.3%) out of the 239 sequences. The duration of ART independently predicted the occurrence of resistance mutation among ART-experienced patients.

CONCLUSION

The high resistance to NNRTIs, which are the main support to the backbone (NRTIs) first-line antiretroviral regimen in Cameroon, has prompted the need to rollout an integrase strand transfer inhibitor regimen (containing Dolutegravir) with a higher genetic barrier to resistance as the preferred first line regimen.

High discordance in blood and genital tract HIV-1 drug resistance in Indian women failing first-line therapy

Objectives

Examine HIV-1 plasma viral load (PVL) and genital tract (GT) viral load (GVL) and drug resistance in India.

Methods

At the YRG Centre for AIDS Research and Education, Chennai, we tested: PVL in women on first-line ART for ≥6 months; GVL when PVL >2000 copies/mL; and plasma, genital and proviral reverse transcriptase drug resistance when GVL >2000 copies/mL. Wilcoxon rank-sum and Fisher's exact tests were used to identify failure and resistance associations. Pearson correlations were calculated to evaluate PVL-GVL associations. Inter-compartmental resistance discordance was evaluated using generalized estimating equations.

Results

Of 200 women, 37% had detectable (>400 copies/mL) PVL and 31% had PVL >1000 copies/mL. Of women with detectable PVL, 74% had PVL >2000 copies/mL, of which 74% had detectable GVL. Higher PVL was associated with higher GVL. Paired plasma and genital sequences were available for 21 women; mean age of 34 years, median ART duration of 33 months, median CD4 count of 217 cells/mm3, median PVL of 5.4 log10 copies/mL and median GVL of 4.6 log10 copies/mL. Drug resistance was detected in 81%-91% of samples and 67%-76% of samples had dual-class resistance. Complete three-compartment concordance was seen in only 10% of women. GT-proviral discordance was significantly larger than plasma-proviral discordance. GT or proviral mutations discordant from plasma led to clinically relevant resistance in 24% and 30%, respectively.

Conclusions

We identified high resistance and high inter-compartmental resistance discordance in Indian women, which might lead to unrecognized resistance transmission and re-emergence compromising treatment outcomes, particularly relevant to countries like India, where sexual HIV transmission is predominant.

Novel HIV-1 Non-nucleoside Reverse Transcriptase Inhibitors: A Combinatorial Approach

Highly active antiretroviral therapy (HAART) is one of the most effective means for fighting against HIV-infection. HAART primarily targets HIV-1 reverse transcriptase (RT), and 14 of 28 compounds approved by the FDA as anti-HIV drugs act on this enzyme. HIV-1 non-nucleoside reverse transcriptase inhibitors (NNRTIs) hold a special place among HIV RT inhibitors owing to their high specificity and unique mode of action. Nonetheless, these drugs show a tendency to decrease their efficacy due to high HIV-1 variability and formation of resistant virus strains tolerant to clinically applied HIV NNRTIs. A combinatorial approach based on varying substituents within various fragments of the parent molecule that results in development of highly potent compounds is one of the approaches aimed at designing novel HIV NNRTIs. Generation of HIV NNRTIs based on pyrimidine derivatives explicitly exemplifies this approach, which is discussed in this review.

Etravirine and Rilpivirine Drug Resistance Among HIV-1 Subtype C Infected Children Failing Non-Nucleoside Reverse Transcriptase Inhibitor-Based Regimens in South India

We have analyzed reverse transcriptase (RT) region of HIV-1 pol gene from 97 HIV-infected children who were identified as failing first-line therapy that included first-generation non-nucleoside RT inhibitors (Nevirapine and Efavirenz) for at least 6 months. We found that 54% and 65% of the children had genotypically predicted resistance to second-generation non-nucleoside RT inhibitors drugs Etravirine (ETR) and Rilpivirine, respectively. These cross-resistance mutations may compromise future NNRTI-based regimens, especially in resource-limited settings. To complement these investigations, we also analyzed the sequences in Stanford database, Monogram weighted score, and DUET weighted score algorithms for ETR susceptibility and found almost perfect agreement between the three algorithms in predicting ETR susceptibility from genotypic data.

Clinical and Virologic Outcomes After Changes in First Antiretroviral Regimen at 7 Sites in the Caribbean, Central and South America Network

BACKGROUND

HIV-infected persons in resource-limited settings may experience high rates of antiretroviral therapy (ART) change, particularly because of toxicity or other nonfailure reasons. Few reports address patient outcomes after these modifications.

METHODS

HIV-infected adults from the 7 Caribbean, Central and South America network clinical cohorts who modified >1 drug from the first ART regimen (ART-1) for any reason thereby starting a second regimen (ART-2) were included. We assessed cumulative incidence of, and factors associated with, death, virologic failure (VF), and regimen change after starting ART-2.

RESULTS

Five thousand five hundred sixty-five ART-naive highly active ART initiators started ART-2 after a median of 9.8 months on ART-1; 39% changed to ART-2 because of toxicity and 11% because of failure. Median follow-up after starting ART-2 was 2.9 years; 45% subsequently modified ART-2. Cumulative incidences of death at 1, 3, and 5 years after starting ART-2 were 5.1%, 8.4%, and 10.5%, respectively. In adjusted analyses, death was associated with older age, clinical AIDS, lower CD4 at ART-2 start, earlier calendar year, and starting ART-2 because of toxicity (adjusted hazard ratio = 1.5 vs. failure, 95% confidence interval: 1.0 to 2.1). Cumulative incidences of VF after 1, 3, and 5 years were 9%, 19%, and 25%. In adjusted analyses, VF was associated with younger age, earlier calendar year, lower CD4 at the start of ART-2, and starting ART-2 because of failure (adjusted hazard ratio = 2.1 vs. toxicity, 95% confidence interval: 1.5 to 2.8).

CONCLUSIONS

Among patients modifying the first ART regimen, risks of subsequent modifications, mortality, and virologic failure were high. Access to improved antiretrovirals in the region is needed to improve initial treatment success.

Role of Rilpivirine and Etravirine in Efavirenz and Nevirapine-Based Regimens Failure in a Resource-Limited Country: A Cross- Sectional Study

Introduction

Etravirine(ETR) can be used for patients who have failed NNRTI-based regimen. In Thailand, ETR is approximately 45 times more expensive than rilpivirine(RPV). However, there are no data of RPV use in NNRTI failure. Therefore, we assessed the susceptibility and mutation patterns of first line NNRTI failure and the possibility of using RPV compared to ETV in patients who have failed efavirenz(EFV)- and nevirapine(NVP)-based regimens.

Methods

Clinical samples with confirmed virological failure from EFV- or NVP-based regimens were retrospectively analyzed. Resistance-associated mutations (RAMs) were interpreted by IAS-USA Drug Resistance Mutations. Susceptibility of ETR and RPV were interpreted by DUET, Monogram scoring system, and Stanford University HIV Drug Resistance Database.

Results

1,279 and 528 patients failed EFV- and NVP-based regimens, respectively. Y181C was the most common NVP-associated RAM (54.3% vs. 14.7%, p<0.01). K103N was the most common EFV-associated RAM (56.5% vs. 19.1%, P<0.01). The results from all three scoring systems were concordant. 165(11.1%) and 161(10.9%) patients who failed NVP-based regimen were susceptible to ETR and RPV, respectively (p = 0.85). 195 (32.2%) and 191 (31.6%) patients who failed EFV-based regimen, were susceptible to ETR and RPV, respectively (p = 0.79). The susceptibility of ETV and RPV in EFV failure was significantly higher than NVP failure (p<0.01).

Conclusion

The mutation patterns for ETR and RPV were similar but 32% and 11% of patients who failed EFV and NVP -based regimen, respectivly were susceptible to RPV. This finding suggests that RPV can be used as the alternative antiretroviral agent in patients who have failed EFV-based regimen.

High prevalence of PI resistance in patients failing second-line ART in Vietnam

Background

There are limited data from resource-limited settings on antiretroviral resistance mutations that develop in patients failing second-line PI ART.

Methods

We performed a cross-sectional virological assessment of adults on second-line ART for ≥6 months between November 2006 and December 2011, followed by a prospective follow-up over 2 years of patients with virological failure (VF) at the Hospital for Tropical Diseases, Vietnam. VF was defined as HIV RNA concentrations ≥1000 copies/mL. Resistance mutations were identified by population sequencing of the pol gene and interpreted using the 2014 IAS-USA mutation list and the Stanford algorithm. Logistic regression modelling was performed to identify predictors of VF.

Results

Two hundred and thirty-one patients were enrolled in the study. The median age was 32 years; 81.0% were male, 95.7% were on a lopinavir/ritonavir-containing regimen and 22 (9.5%) patients had VF. Of the patients with VF, 14 (64%) carried at least one major protease mutation [median: 2 (IQR: 1–3)]; 13 (59%) had multiple protease mutations conferring intermediate- to high-level resistance to lopinavir/ritonavir. Mutations conferring cross-resistance to etravirine, rilpivirine, tipranavir and darunavir were identified in 55%, 55%, 45% and 27% of patients, respectively. Higher viral load, adherence <95% and previous indinavir use were independent predictors of VF. The 2 year outcomes of the patients maintained on lopinavir/ritonavir included: death, 7 (35%); worsening virological/immunological control, 6 (30%); and virological re-suppression, 5 (25%). Two patients were switched to raltegravir and darunavir/ritonavir with good HIV control.

Conclusions

High-prevalence PI resistance was associated with previous indinavir exposure. Darunavir plus an integrase inhibitor and lamivudine might be a promising third-line regimen in Vietnam.

Predicted residual activity of rilpivirine in HIV-1 infected patients failing therapy including NNRTIs efavirenz or nevirapine

Rilpivirine is a second-generation nonnucleoside reverse-transcriptase inhibitor (NNRTI) currently indicated for first-line therapy, but its clinical benefit for HIV-1 infected patients failing first-generation NNRTIs is largely undefined. This study quantified the extent of genotypic rilpivirine resistance in viral isolates from 1212 patients upon failure of efavirenz- or nevirapine-containing antiretroviral treatment, of whom more than respectively 80% and 90% showed high-level genotypic resistance to the failing NNRTI. Of all study patients, 47% showed a rilpivirine resistance-associated mutation (RPV-RAM), whereas preserved residual rilpivirine activity was predicted in half of the patients by three genotypic drug resistance interpretation algorithms. An NNRTI-dependent impact on rilpivirine resistance was detected. Compared with the use of nevirapine, the use of efavirenz was associated with a 32% lower risk of having a RPV-RAM and a 50% lower risk of predicted reduced rilpivirine susceptibility. Most prevalent RPV-RAMs after nevirapine experience were Y181C and H221Y, whereas L100I+K103N, Y188L and K101E occurred most in efavirenz-experienced patients. Predicted rilpivirine activity was not affected by HIV-1 subtype, although frequency of individual mutations differed across subtypes. In conclusion, this genotypic resistance analysis strongly suggests that the latest NNRTI, rilpivirine, may retain activity in a large proportion of HIV-1 patients in whom resistance failed while they were on an efavirenz- or nevirapine-containing regimen, and may present an attractive option for second-line treatment given its good safety profile and dosing convenience. However, prospective clinical studies assessing the effectiveness of rilpivirine for NNRTI-experienced patients are warranted to validate knowledge derived from genotypic and phenotypic drug resistance studies.

Drug resistance in non-B subtype HIV-1: impact of HIV-1 reverse transcriptase inhibitors

Human immunodeficiency virus (HIV) causes approximately 2.5 million new infections every year, and nearly 1.6 million patients succumb to HIV each year. Several factors, including cross-species transmission and error-prone replication have resulted in extraordinary genetic diversity of HIV groups. One of these groups, known as group M (main) contains nine subtypes (A-D, F-H and J-K) and causes ~95% of all HIV infections. Most reported data on susceptibility and resistance to anti-HIV therapies are from subtype B HIV infections, which are prevalent in developed countries but account for only ~12% of all global HIV infections, whereas non-B subtype HIV infections that account for ~88% of all HIV infections are prevalent primarily in low and middle-income countries. Although the treatments for subtype B infections are generally effective against non-B subtype infections, there are differences in response to therapies. Here, we review how polymorphisms, transmission efficiency of drug-resistant strains, and differences in genetic barrier for drug resistance can differentially alter the response to reverse transcriptase-targeting therapies in various subtypes.

High level of HIV-1 resistance in patients failing long-term first-line antiretroviral therapy in Mali

OBJECTIVES

In resource-limited settings, few data are available on virological failure after long-term first-line antiretroviral therapy. This study characterized the genotypic resistance patterns at the time of failure after at least 36 months of a first-line regimen in Mali, West Africa.

METHODS

Plasma samples from 84 patients who were receiving first-line antiretroviral treatment and with an HIV-1 RNA viral load (VL) >1000 copies/mL were analysed. Genotypic resistance testing was performed and HIV-1 drug resistance was interpreted according to the latest version of the National Agency for HIV and Hepatitis Research algorithm.

RESULTS

At the time of resistance testing, patients had been treated for a median of 60 months (IQR 36-132 months) and had a median CD4 cell count of 292 cells/mm(3) (IQR 6-1319 cells/mm(3)), a median HIV-1 RNA level of 28266 copies/mL (IQR 1000-2 93 495 copies/mL) and a median genotypic susceptibility score of 1 (IQR 1-4). The prevalence of nucleoside reverse transcriptase inhibitor (NRTI) and non-nucleoside reverse transcriptase inhibitor (NNRTI) resistance mutations was 78% and 82%, respectively. Viruses were resistant to at least one drug in 92% of cases. Although etravirine and rilpivirine were not used in the first-line regimens, viruses were resistant to etravirine in 34% of cases and to rilpivirine in 49% of cases. The treatment duration, median number of NRTI and NNRTI mutations and some reverse transcriptase mutations (T215Y/F/N, L210W, L74I, M41L and H221Y) were associated with the VL at virological failure.

CONCLUSIONS

This study demonstrated a high level of resistance to NRTIs and NNRTIs, compromising second-generation NNRTIs, for patients who stayed on long-term first-line regimens. It is crucial to expand the accessibility of virological testing in resource-limited settings to limit the expansion of resistance and preserve second-line treatment efficacy.

Transmitted drug resistance to rilpivirine among antiretroviral-naïve patients living with HIV from northern Poland

Introduction

Rilpivirine (RPV) is a second-generation non-nucleoside reverse transcriptase inhibitor (NNRTI) that was recently approved for the treatment of antiretroviral-naïve individuals with HIV-1 viral load of <100,000 copies/ml. As transmission of the drug resistance mutations to this NNRTI may affect treatment outcomes, the frequency of primary, RPV-associated drug resistance mutations was assessed in this study.

Methods

For the study, 244 viral genome sequences from antiretroviral-naïve individuals were obtained by bulk sequencing. RPV-associated mutations were divided into RPV resistance mutations (K101E/P, E138A/G/K/Q/R, V179L, Y181C/I/V, Y188L, H221Y, F227C and M230I/L) according to the International AIDS Society-USA (IAS-USA) mutation list and variants potentially affecting RPV susceptibility (L100I, K101H/T, E138S, V179F/D/G/T, G190A/E/S, F227L and M230V) based on the in vitro and in vivo data.

Results

IAS-USA RPV drug resistance mutations were found in 5.3% sequences, with E138A and E138G being the most common (3.7 and 0.8%, respectively), followed by K101E (0.4%) and Y181C (0.4%), with no significant differences in the frequency between subtype B and non-B clades. Mutations potentially reducing RPV susceptibility were found in 2.5% of sequences, and they included V179D (1.6%) and G190A (0.8%), with equal distribution among non-B (n=2, 2.5%) and subtype B (n=4, 2.5%) clades. Clustering of RPV mutations was infrequent.

Conclusions

Prevalence of RPV-associated drug resistance mutations was low in the analysed sample and did not vary across the subtypes. The frequency of variants with potential influence on RPV susceptibility was similar among non-B variants if compared to B clades. Transmitted drug resistance to RPV is uncommon, which makes this a good option for the treatment of ARV-naïve patients; however, genotype resistance testing should remain compulsory before starting an RPV-based regimen.

Prevalence in the USA of rilpivirine resistance-associated mutations in clinical samples and effects on phenotypic susceptibility to rilpivirine and etravirine

BACKGROUND

The prevalence of rilpivirine resistance-associated mutations (RAMs) in the USA, and their effect on phenotypic susceptibility to rilpivirine and etravirine, was evaluated in clinical samples from HIV-1-infected patients.

METHODS

In total, 15,991 samples submitted to Monogram Biosciences (South San Francisco, CA, USA) for routine resistance testing between January 2010 and June 2011 were assessed for the presence of known rilpivirine RAMs K101E/P, E138A/G/K/Q/R, V179L, Y181C/I/V, Y188L, H221Y, F227C and M230I/L; non-nucleoside reverse transcriptase inhibitor (NNRTI) RAMs K103N, L100I and L100I+K103N; and the nucleoside reverse transcriptase inhibitor (NRTI) RAMs M184I/V and their combinations with rilpivirine RAMs. Phenotypic susceptibility (PhenoSenseGT(®) assay; Monogram Biosciences) was evaluated, with reduced susceptibility defined as fold change (FC) in 50% inhibitory concentration (IC50)>2.0 for rilpivirine and FC>2.9 for etravirine.

RESULTS

Of the 15,991 samples, 17% harboured ≥1 rilpivirine RAMs. The prevalence of most rilpivirine RAMs and combinations of NNRTI RAMs of interest was low (≤3%), except for Y181C (7%). Rilpivirine RAMs were often associated with reduced rilpivirine phenotypic susceptibility. Median FC values >2.0 were observed for clinical isolates with rilpivirine RAMs K101P, E138Q/R, Y181C/I/V, Y188L or M230L, and for the combination of E138K with M184I/V, and K101E with M184I. Most rilpivirine FC values >2.0 were associated with etravirine FC values >2.9 for individual rilpivirine RAMs and those combined with M184I/V. There was no relationship between the presence of K103N and rilpivirine FC. However, the L100I+K103N combination (without rilpivirine RAMs), at <2% prevalence, was associated with a rilpivirine FC>2.0.

CONCLUSIONS

Based on 15,991 US clinical samples from HIV-1-infected patients, the frequency of most known rilpivirine RAMs apart from Y181C was low.

HIV-1 Genetic Variability and Clinical Implications

Despite advances in antiretroviral therapy that have revolutionized HIV disease management, effective control of the HIV infection pandemic remains elusive. Beyond the classic non-B endemic areas, HIV-1 non-B subtype infections are sharply increasing in previous subtype B homogeneous areas such as Europe and North America. As already known, several studies have shown that, among non-B subtypes, subtypes C and D were found to be more aggressive in terms of disease progression. Luckily, the response to antiretrovirals against HIV-1 seems to be similar among different subtypes, but these results are mainly based on small or poorly designed studies. On the other hand, differences in rates of acquisition of resistance among non-B subtypes are already being observed. This different propensity, beyond the type of treatment regimens used, as well as access to viral load testing in non-B endemic areas seems to be due to HIV-1 clade specific peculiarities. Indeed, some non-B subtypes are proved to be more prone to develop resistance compared to B subtype. This phenomenon can be related to the presence of subtype-specific polymorphisms, different codon usage, and/or subtype-specific RNA templates. This review aims to provide a complete picture of HIV-1 genetic diversity and its implications for HIV-1 disease spread, effectiveness of therapies, and drug resistance development.

Resistance to the most recent protease and non-nucleoside reverse transcriptase inhibitors across HIV-1 non-B subtypes

OBJECTIVES

Limited data are available on resistance to etravirine, rilpivirine, darunavir and tipranavir in patients infected with HIV-1 non-B subtypes, in which natural polymorphisms at certain positions could influence the barrier and/or pathways to drug resistance.

METHODS

FASTA format sequences from the reverse transcriptase and protease genes recorded within the Spanish Drug Resistance database (ResRIS) were examined.

RESULTS

From 8272 genotypes derived from 5930 different HIV-1 patients included in ResRIS, 5276 genotypes had complete treatment information. Overall, 85% were from antiretroviral-experienced subjects and 7.5% belonged to HIV-1 non-B subtypes: CRF02_AG, C, F and G being the most prevalent variants. For etravirine, only G190A was more prevalent in B than non-B subtypes, whereas V90I and V179E were more frequent in non-B than B subtypes. For rilpivirine, V108I and Y188I were more frequent in B than non-B subtypes, whereas V90I was more prevalent in non-B subtypes. Despite these differences, the overall prevalence of resistance did not differ significantly when comparing etravirine or rilpivirine in B versus non-B subtypes (11.3% versus 7.4%, P = 0.13, and 10.5% versus 7.4%, P = 0.23, respectively). Despite more frequent natural polymorphisms in non-B than B subtypes at tipranavir resistance positions, the prevalence of tipranavir resistance was greater in B than non-B subtypes (11% versus 4.3%, P = 0.004), reflecting a greater antiretroviral exposure in the former. Darunavir resistance did not differ significantly when comparing B and non-B subtypes (5.8% versus 5.5%, P = 0.998).

CONCLUSIONS

The rate of resistance to the most recently approved protease and non-nucleoside reverse transcriptase inhibitors is low in antiretroviral-experienced patients, regardless of the HIV-1 subtype.

Rilpivirine resistance mutations in HIV patients failing non-nucleoside reverse transcriptase inhibitor-based therapies

OBJECTIVE

Rilpivirine (RPV) is the latest approved nonnucleoside reverse transcriptase inhibitor (NNRTI). It displays in-vitro activity extending over other NNRTI-resistant HIV strains. There is scarce information about the rate of RPV resistance-associated mutations (RAMs) in patients failing other NNRTIs.

METHODS

RPV RAMs were examined in plasma samples collected from HIV patients that had recently failed NNRTI-based regimens at 22 clinics in Spain.

RESULTS

Resistance tests from a total of 1064 patients failing efavirenz (EFV) (54.5%), nevirapine (NVP) (40%) or etravirine (ETR) (5.5%) were examined. The prevalence of RPV RAMs was K101E (9.1%), K101P (1.4%), E138A (3.9%), E138G (0.3%), E138K (0.3%), E138Q (0.8%), V179L (0.2%), Y181C (21.8%), Y181I (0.5%), Y181V (0.2%), H221Y (8.3%), F227C (0.1%) and M230L (1.5%). K101E/M184I was seen in 1%. E138K/M184I were absent. Mutations L100I and V108I were significantly more frequent in patients failing EFV than NVP (7.9 vs. 0.2 and 12.2 vs. 7.3%, respectively). Conversely, Y181C, Y181I, V106A, H221Y and F227L were more prevalent following NVP than EFV failures. Using the Spanish resistance interpretation algorithm, 206 genotypes (19.3%) from patients failing NNRTI (NVP 52%, EFV 40.8% and ETR 7.8%) were considered as RPV resistant. In patients with ETR failure, cross-resistance to RPV was seen in 27.6%, mainly as result of Y181C (81.3%), V179I (43.8%), V90I (31.3%) and V108I (18.8%).

CONCLUSION

RPV resistance is overall recognized in nearly 20% of patients failing other NNRTIs. It is more common following ETR (27.6%) or NVP (25%) failures than EFV (14.5%). E138 mutants are rarely seen in this context.

The nucleoside reverse transcriptase inhibitors, nonnucleoside reverse transcriptase inhibitors, and protease inhibitors in the treatment of HIV infections (AIDS)

The majority of the drugs currently used for the treatment of HIV infections (AIDS) belong to either of the following three classes: nucleoside reverse transcriptase inhibitors (NRTIs), nonnucleoside reverse transcriptase inhibitors (NNRTIs), and protease inhibitors (PIs). At present, there are 7 NRTIs, 5 NNRTIs, and 10 PIs approved for clinical use. They are discussed from the following viewpoints: (i) chemical formulae; (ii) mechanism of action; (iii) drug combinations; (iv) clinical aspects; (v) preexposure prophylaxis; (vi) prevention of mother-to-child transmission; (vii) their use in children; (viii) toxicity; (ix) adherence (compliance); (x) resistance; (xi) new NRTIs, NNRTIs, or PIs in (pre)clinical development; and (xii) the prospects for a "cure" of the disease.

Susceptibility to etravirine of HIV type 1 subtype C isolates from nevirapine/efavirenz-experienced patients: comparative interpretation of ANRS and STANFORD algorithms

Abstract We analyzed subtype C HIV-1 isolates from patients at failure of a regimen including nevirapine or efavirenz for their susceptibility or resistance to etravirine according to the ANRS and STANFORD algorithms. Statistical analysis showed a consensus that more than 45% of these viral strains are potentially resistant to etravirine.

Association of APOBEC3G genotypes and CD4 decline in Thai and Cambodian HIV-infected children with moderate immune deficiency

INTRODUCTION

Human APOBEC3G is a host defense factor that potently inhibits HIV replication. We hypothesize that HIV-infected children with a genetic variant of APOBEC3G will have a more rapid disease progression.

METHODS

Antiretroviral therapy (ART)-naïve children, aged 1-12 years old with CD4 15-24% and without severe HIV-related symptoms were enrolled. The children had CD4% and absolute CD4 counts every 12 weeks and HIV-RNA every 24 weeks until 144 weeks. ART was started when CD4% declined to < 15% or AIDS-related events developed.APOBEC3G genetic variants were performed by PCR-based restriction fragment length polymorphism techniques from peripheral blood mononuclear cells. Random-effect linear regression analysis was performed to correlate APOBEC3G genotypes and disease progression.

RESULTS

147 children, 35% male, with a median (IQR) age of 6.5 (4.3-8.8) years were enrolled. CDC N:A:B were 1:63:36%. Median baseline values were 20% for CD4% 605 cells/mm3 for CD4 count and 4.7 log10copies/mL for HIV-RNA.The frequencies of APOBEC3G genotypes AA (186H/H), AG (186H/R), GG (186R/R) were 86%, 12%, and 2% respectively. The APOBEC3G genotype GG was associated with a significant decline in CD4% -5.1% (-8.9 to -1.2%), p<0.001, and CD4 counts -226 (-415 to -34) cells/mm3, p<0.001 by random-effect liner regression analysis. No significant associations of APOBEC3G genotypes with HIV-RNA changes overtime (p=0.16) or progression to CDC B and C (p=0.49) were observed.

CONCLUSIONS

APOBEC3G genotype GG was significantly associated with a more rapid decline in CD4. APOBEC3G's antiviral effects on HIV disease progression in children should be further explored.

HIV-1 antiretroviral resistance: scientific principles and clinical applications

The efficacy of an antiretroviral (ARV) treatment regimen depends on the activity of the regimen's individual ARV drugs and the number of HIV-1 mutations required for the development of resistance to each ARV - the genetic barrier to resistance. ARV resistance impairs the response to therapy in patients with transmitted resistance, unsuccessful initial ARV therapy and multiple virological failures. Genotypic resistance testing is used to identify transmitted drug resistance, provide insight into the reasons for virological failure in treated patients, and help guide second-line and salvage therapies. In patients with transmitted drug resistance, the virological response to a regimen selected on the basis of standard genotypic testing approaches the responses observed in patients with wild-type viruses. However, because such patients are at a higher risk of harbouring minority drug-resistant variants, initial ARV therapy in this population should contain a boosted protease inhibitor (PI) - the drug class with the highest genetic barrier to resistance. In patients receiving an initial ARV regimen with a high genetic barrier to resistance, the most common reasons for virological failure are nonadherence and, potentially, pharmacokinetic factors or minority transmitted drug-resistant variants. Among patients in whom first-line ARVs have failed, the patterns of drug-resistance mutations and cross-resistance are often predictable. However, the extent of drug resistance correlates with the duration of uncontrolled virological replication. Second-line therapy should include the continued use of a dual nucleoside/nucleotide reverse transcriptase inhibitor (NRTI)-containing backbone, together with a change in the non-NRTI component, most often to an ARV belonging to a new drug class. The number of available fully active ARVs is often diminished with each successive treatment failure. Therefore, a salvage regimen is likely to be more complicated in that it may require multiple ARVs with partial residual activity and compromised genetic barriers of resistance to attain complete virological suppression. A thorough examination of the patient's ARV history and prior resistance tests should be performed because genotypic and/or phenotypic susceptibility testing is often not sufficient to identify drug-resistant variants that emerged during past therapies and may still pose a threat to a new regimen. Phenotypic testing is also often helpful in this subset of patients. ARVs used for salvage therapy can be placed into the following hierarchy: (i) ARVs belonging to a previously unused drug class; (ii) ARVs belonging to a previously used drug class that maintain significant residual antiviral activity; (iii) NRTI combinations, as these often appear to retain in vivo virological activity, even in the presence of reduced in vitro NRTI susceptibility; and rarely (iv) ARVs associated with previous virological failure and drug resistance that appear to have possibly regained their activity as a result of viral reversion to wild type. Understanding the basic principles of HIV drug resistance is helpful in guiding individual clinical decisions and the development of ARV treatment guidelines.