Epidemiology of antiretroviral multiclass resistance

Heavily treatment-experienced persons living with HIV currently in care in Italy: characteristics, risk factors, and therapeutic options-the ICONA Foundation cohort study

OBJECTIVES

Heavily treatment-experienced (HTE) people living with HIV (PLWH) pose unique challenges due to limited antiretroviral treatment (ART) options. Our study aimed to investigate the prevalence and features of HTE individuals followed up in the Italian Cohort Naïve Antiretrovirals (ICONA) cohort as of December 31, 2021.

METHODS

HTE were defined based on meeting specific conditions concerning their current ART and their ART history up to December 31, 2021. Descriptive statistics were performed by HTE status. Regression analyses explored factors associated with becoming HTE based on pre-ART patients' characteristics. Cluster dendrogram analysis provided insights into subgroups with inadequate responses based on clusters of differentiation (CD4) counts and viral load (VL) trajectories.

RESULTS

Among the 8758 PLWH actively followed in our cohort, 163 individuals (1.9%), mainly female, younger, Italian, and infected through heterosexual contact, met the HTE criteria. A lower CD4 count at ART initiation (odds ratio [OR] 1.60 per 100 cells/mmc lower CD4, 95% confidence interval [CI] 1.06-2.41, P = 0.03) and hepatitis C virus antibody positivity (OR 1.90, 95% CI 1.16-3.11, P = 0.01) were associated with higher HTE risk. Thirty PLWH exhibited ongoing immune-virological failure (18% of the HTE subgroup and 0.003% of the total population). Thirty PLWH exhibited ongoing immune-virological failure (i.e., with a current CD4 count <200 cells/mmc or VL>200 copies/mL). A cluster analysis identified 13 (43%) with a current CD4 count <200 cells/mmc. Also, notably, 19/30 (63%) had major acquired resistance-associated mutations to at least one antiretroviral drug class.

CONCLUSIONS

HTE is rare in our cohort and tends to co-exist with major resistance mutations. A focused investigation into treatment history and immuno-virological response is warranted, particularly given the availability of new antiretroviral drugs.

A characterization of the HIV population with limited/exhausted treatment options: a multicenter Belgian study

OBJECTIVE

Describe the prevalence and characteristics of people living with HIV (PLWH) in Belgium with limited/exhausted treatment options.

METHODS

A cross-sectional, multicenter study involving adult treatment-experienced individuals with limited/exhausted treatment options defined as having a multi-drug resistant HIV-1 or a history of multiple treatment changes. The primary outcome was to determine the prevalence of these individuals and classify them based on their two most recent consecutive HIV-1 viral loads (VLs): suppressed (2 VLs < 50 copies/mL), intermediate (≥1 VL between 50-200 copies/mL), or unsuppressed (2 VLs > 200 copies/mL). Secondary outcome was to characterize the participants included in this analysis.

RESULTS

There were 119 individuals included (prevalence of 0.97%; 119 of 12 282 in care). The majority were aged > 50 years (88.2%), women represented 35.3%, and individuals were primarily White (54.7%). Median (IQR) CD4+ T-cell count was 635 (400-875) cells/µL and most (42%) were on a 3-drug ART regimen. Overall, 87.4% were classified as suppressed, 9.2% as intermediate, and 3.4% as unsuppressed. On multivariable analysis, CD4+ T-cell count < 200 cells/µL was associated with being classified as intermediate or unsuppressed (p = 0.004).

CONCLUSION

In this analysis of PLWH in Belgium, individuals with limited/exhausted treatment options represented a small fraction. Most were on a 3-drug ART regimen, were virologically suppressed, and had a CD4+ T-cell count within normal range. A small proportion were not virologically suppressed while others, despite being suppressed, were on ≥ 4-drug ART regimens. As such, new therapeutic options are needed to achieve and maintain virologic suppression in such individuals while decreasing their pill burden.

Substantial decline in heavily treated therapy-experienced persons with HIV with limited antiretroviral treatment options

OBJECTIVE

Historically, a high burden of resistance to antiretroviral therapy (ART) in heavily treatment-experienced (HTE) persons with HIV (PWH) resulted in limited treatment options (LTOs). We evaluated the prevalence, risk factors, and virologic control of HTE PWH with LTO throughout the modern ART era.

DESIGN

We examined all ART-experienced PWH in care between 2000 and 2017 in the Centers for AIDS Research Network of Integrated Clinical Systems cohort.

METHODS

We computed the annual prevalence of HTE PWH with LTO defined as having two or less available classes with two or less active drugs per class based on genotypic data and cumulative antiretroviral resistance. We used multivariable Cox proportional hazards models to examine risk of LTO by 3-year study entry periods adjusting for demographic and clinical characteristics.

RESULTS

Among 27 133 ART-experienced PWH, 916 were classified as having LTO. The prevalence of PWH with LTO was 5.2-7.5% in 2000-2006, decreased to 1.8% in 2007, and remained less than 1% after 2012. Persons entering the study in 2009-2011 had an 80% lower risk of LTO compared with those entering in 2006-2008 (adjusted hazard ratio 0.20; 95% confidence interval: 0.09-0.42). We found a significant increase in undetectable HIV viral loads among PWH ever classified as having LTO from less than 30% in 2001 to more than 80% in 2011, comparable with persons who never had LTO.

CONCLUSION

Results of this large multicenter study show a dramatic decline in the prevalence of PWH with LTO to less than 1% with the availability of more potent drugs and a marked increase in virologic suppression in the current ART era.

Advances in Long-Acting Agents for the Treatment of HIV Infection

Long-acting antiretroviral therapy holds the promise of new options for human immunodeficiency virus (HIV) treatment beyond the current paradigm of daily oral pills. Of particular interest is their potential role in addressing challenges with adherence to oral therapy and treatment fatigue. Similar to other conditions where long-acting formulations have proven effective such as contraception and mental health, long-acting antiretroviral therapy could provide additional treatment choices to people with HIV. This review provides an outline of the current landscape of long-acting antiretroviral therapy for HIV treatment, both approved and under development, including cabotegravir, rilpivirine, leronlimab, islatravir, albuvirtide, GS-6207, and broadly neutralizaing antibodies. However, there are a number of research gaps for long-acting antiretroviral therapy including issues regarding resistance and understudied populations, and this review highlights some of the challenges that will need to be addressed for clinical implementation of these novel treatment modalities.

Clinical and Economic Impact of Ibalizumab for People With Multidrug-Resistant HIV in the United States

BACKGROUND

We projected the clinical outcomes, cost-effectiveness, and budget impact of ibalizumab plus an optimized background regimen (OBR) for people with multidrug-resistant (MDR) HIV in the United States.

METHODS

Using the Cost-Effectiveness of Preventing AIDS Complications microsimulation model and a health care sector perspective, we compared 2 treatment strategies for MDR HIV: (1) IBA + OBR-ibalizumab plus OBR and (2) OBR-OBR alone. Ibalizumab efficacy and cohort characteristics were from trial data: mean age 49 years, 85% male, and mean CD4 150/µL. Six-month viral suppression was 50% with IBA + OBR and 0% with OBR. The ibalizumab loading dose cost $10,500, and subsequent ibalizumab injections cost $8400/month; OBR cost $4500/month. Incremental cost-effectiveness ratios (ICERs) were calculated using discounted (3%/year) quality-adjusted life years (QALYs) and costs. ICERs ≤$100,000/QALY were considered cost-effective. We performed sensitivity analysis on key parameters and examined budget impact.

RESULTS

In the base case, 5-year survival increased from 38% with OBR to 47% with IBA + OBR. Lifetime costs were $301,700/person with OBR and $661,800/person with IBA + OBR; the ICER for IBA + OBR compared with OBR was $260,900/QALY. IBA + OBR was not cost-effective even with 100% efficacy. IBA + OBR became cost-effective at base case efficacy if ibalizumab cost was reduced by ≥88%. For an estimated 12,000 people with MDR HIV in the United States, IBA + OBR increased care costs by $1.8 billion (1.5% of total treatment budget) over 5 years.

CONCLUSIONS

For people with MDR HIV lacking other treatment options, ibalizumab will substantially increase survival when effective. Although adding ibalizumab to OBR is not cost-effective, the low number of eligible patients in the United States makes the budget impact relatively small.

Phase 3 Study of Ibalizumab for Multidrug-Resistant HIV-1

BACKGROUND

Ibalizumab, a humanized IgG4 monoclonal antibody, blocks the entry of human immunodeficiency virus type 1 (HIV-1) by noncompetitive binding to CD4.

METHODS

In this single-group, open-label, phase 3 study, we enrolled 40 adults with multidrug-resistant (MDR) HIV-1 infection in whom multiple antiretroviral therapies had failed. All the patients had a viral load of more than 1000 copies of HIV-1 RNA per milliliter. After a 7-day control period in which patients continued to receive their current therapy, a loading dose of 2000 mg of ibalizumab was infused; the viral load was quantified 7 days later. Through week 25 of the study, patients received 800 mg of ibalizumab every 14 days, combined with an individually optimized background regimen including at least one fully active agent. The primary end point was the proportion of patients with a decrease in viral load of at least 0.5 log₁₀ copies per milliliter from baseline (day 7) to day 14.

RESULTS

A total of 31 patients completed the study. The mean baseline viral load was 4.5 log₁₀ copies per milliliter, and the mean CD4 count was 150 per microliter. Of the 40 patients in the intention-to-treat population, 33 (83%) had a decrease in viral load of at least 0.5 log₁₀ copies per milliliter from baseline (P<0.001 for the comparison with the control period). The mean viral-load decrease was 1.1 log₁₀ copies per milliliter. During the control period, 1 patient, who received the optimized background regimen prematurely, had a decrease in viral load of 0.5 log₁₀ copies per milliliter. At week 25, patients who had received ibalizumab plus an optimized background regimen had a mean decrease of 1.6 log₁₀ copies per milliliter from baseline; 43% of the patients had a viral load of less than 50 copies per milliliter, and 50% had a viral load of less than 200 copies per milliliter. Among 10 patients who had virologic failure or rebound, in vitro testing identified 9 who had a lower degree of susceptibility to ibalizumab than at baseline. The most common adverse event was diarrhea (in 20% of patients). Four patients died from causes related to underlying illnesses; 1 had a serious adverse event (the immune reconstitution inflammatory syndrome) that was deemed to be related to ibalizumab therapy.

CONCLUSIONS

In patients with MDR HIV-1 infection who had advanced disease and limited treatment options, ibalizumab had significant antiviral activity during a 25-week study. Evidence of the emergence of diminished ibalizumab susceptibility was observed in vitro in patients who had virologic failure. (Funded by the Orphan Products Clinical Trials Grants Program of the Food and Drug Administration and TaiMed Biologics; TMB-301 ClinicalTrials.gov number, NCT02475629 .).

Long-term effectiveness of initiating non-nucleoside reverse transcriptase inhibitor- versus ritonavir-boosted protease inhibitor-based antiretroviral therapy: implications for first-line therapy choice in resource-limited settings

Introduction

In many resource-limited settings, combination antiretroviral therapy (cART) failure is diagnosed clinically or immunologically. As such, there is a high likelihood that patients may stay on a virologically failing regimen for a substantial period of time. Here, we compared the long-term impact of initiating non-nucleoside reverse transcriptase inhibitor (NNRTI)- versus boosted protease inhibitor (bPI)-based cART in British Columbia (BC), Canada.

Methods

We followed prospectively 3925 ART-naïve patients who started NNRTIs (N=1963, 50%) or bPIs (N=1962; 50%) from 1 January 2000 until 30 June 2013 in BC. At six months, we assessed whether patients virologically failed therapy (a plasma viral load (pVL) >50 copies/mL), and we stratified them based on the pVL at the time of failure ≤500 versus >500 copies/mL. We then followed these patients for another six months and calculated their probability of achieving subsequent viral suppression (pVL <50 copies/mL twice consecutively) and of developing drug resistance. These probabilities were adjusted for fixed and time-varying factors, including cART adherence.

Results

At six months, virologic failure rates were 9.5 and 14.3 cases per 100 person-months for NNRTI and bPI initiators, respectively. NNRTI initiators who failed with a pVL ≤500 copies/mL had a 16% higher probability of achieving subsequent suppression at 12 months than bPI initiators (0.81 (25th–75th percentile 0.75–0.83) vs. 0.72 (0.61–0.75)). However, if failing NNRTI initiators had a pVL >500 copies/mL, they had a 20% lower probability of suppressing at 12 months than pVL-matched bPI initiators (0.37 (0.29–0.45) vs. 0.46 (0.38–0.54)). In terms of evolving HIV drug resistance, those who failed on NNRTI performed worse than bPI in all scenarios, especially if they failed with a viral load >500 copies/mL.

Conclusions

Our results show that patients who virologically failed at six months on NNRTI and continued on the same regimen had a lower probability of subsequently achieving viral suppression and a higher chance of evolving HIV drug resistance. These results suggest that improving access to regular virologic monitoring is critically important, especially if NNRTI-based cART is to remain a preferred choice for first-line therapy in resource-limited settings.

Transmitted drug resistance in recently infected HIV-positive Individuals from four urban locations across Asia (2007-2010) - TASER-S

BACKGROUND

The availability of HIV antiretroviral therapy (ART) has been associated with the development of transmitted drug resistance-associated mutations (TDRM). TDRM can compromise treatment effectiveness in patients initiating ART and the prevalence can vary in different clinical settings. In this study, we investigated the proportion of TDRM in treatment-naïve, recently infected HIV-positive individuals sampled from four urban locations across Asia between 2007-2010.

METHODS

Patients enrolled in the TREAT Asia Studies to Evaluate Resistance - Surveillance Study (TASER-S) were genotyped prior to ART initiation, with resulting resistance mutations analysed according to the WHO 2009 list.

RESULTS

Proportions of TDRM from recently infected individuals from TASER-S ranged from 0% to 8.7% - Hong Kong: 3/88 (3.4%, 95% CI (0.71%-9.64%)); Thailand: Bangkok: 13/277 (4.7%, 95% CI (2.5%-7.9%)), Chiang Mai: 0/17 (0%, 97.5% CI (0%-19.5%)); and the Philippines: 6/69 (8.7%, 95% CI (3.3%-18.0%)). There was no significant increase in TDRM over time across all four clinical settings.

CONCLUSIONS

The observed proportion of TDRM in TASER-S patients from Hong Kong, Thailand and the Philippines was low to moderate during the study period. Regular monitoring of TDRM should be encouraged, especially with the scale-up of ART at higher CD4 levels.

Modeling scenarios for the end of AIDS

At the end of 2012, 3 decades after the human immunodeficiency virus (HIV) was first identified, neither a cure nor a fully preventive vaccine was available. Despite multiple efforts, the epidemic remains an exceptional public health challenge. At the end of 2012, it was estimated that, globally, 35 million people were living with HIV, 2.3 million had become newly infected, and 1.6 million had died from AIDS-related causes. Despite substantial prevention efforts and increases in the number of individuals on highly active antiretroviral therapy (HAART), the epidemic burden continues to be high. Here, we provide a brief overview of the epidemiology of HIV transmission, the work that has been done to date regarding HIV modeling in different settings around the world, and how to finance the response to the HIV epidemic. In addition, we suggest discussion topics on how to move forward with the prevention agenda and highlight the role of treatment as prevention (TasP) in curbing the epidemic.

Cohort Profile: HAART Observational Medical Evaluation and Research (HOMER) cohort

Since 1986, antiretroviral therapy (ART) has been available free of charge to individuals living with HIV in British Columbia (BC), Canada, through the BC Centre of Excellence in HIV/AIDS (BC-CfE) Drug Treatment Program (DTP). The Highly Active Antiretroviral Therapy (HAART) Observational Medical Evaluation and Research (HOMER) cohort was established in 1996 to maintain a prospective record of clinical measurements and medication profiles of a subset of DTP participants initiating HAART in BC. This unique cohort provides a comprehensive data source to investigate mortality, prognostic factors and treatment response among people living with HIV in BC from the inception of HAART. Currently over 5000 individuals are enrolled in the HOMER cohort. Data captured include socio-demographic characteristics (e.g. sex, age, ethnicity, health authority), clinical variables (e.g. CD4 cell count, plasma HIV viral load, AIDS-defining illness, hepatitis C co-infection, mortality) and treatment variables (e.g. HAART regimens, date of treatment initiation, treatment interruptions, adherence data, resistance testing). Research findings from the HOMER cohort have featured in numerous high-impact peer-reviewed journals. The HOMER cohort collaborates with other HIV cohorts on both national and international scales to answer complex HIV-specific research questions, and welcomes input from external investigators regarding potential research proposals or future collaborations. For further information please contact the principal investigator, Dr Robert Hogg (robert_hogg@sfu.ca).

The successful application of a national peer advisory committee for physicians who provide salvage regimens to heavily antiretroviral-experienced patients in mexican human immunodeficiency virus clinics

BACKGROUND

Designing optimal antiretroviral (ARV) salvage regimens for multiclass drug-resistant, human immunodeficiency virus (HIV)-infected patients demands specific clinical skills. Our aim was to assess the virologic and immunologic effects of the treatment recommendations drafted by a peer advisory board to physicians caring for heavily ARV-experienced patients.

METHODS

We conducted a nationwide, HIV clinic-based, cohort study in Mexico. Adults infected with HIV were assessed for a median of 33 months (interquartile range [IQR] = 22-43 months). These patients had experienced the virologic failure of at least 2 prior ARV regimens and had detectable viremia while currently being treated; their physicians had received therapeutic advice, by a panel of experts, regarding the ARV salvage regimen. The primary endpoint was the incidence of loss of virologic response (plasma HIV-RNA levels of <200 copies per mL, followed by levels above this threshold) during the follow-up assessment using an observed-failure competing risks regression analysis.

RESULTS

A total of 611 patients were observed (median ARV therapy exposure = 10.5 years; median prior regimens = 4). The probabilities of virologic failure were 11.9%, 14.4%, 16.9%, and 19.4% at the 12-, 24-, 36-, and 48-month follow-up assessments, respectively. Of the 531 patients who achieved a confirmed plasma HIV-RNA level below 200 copies per mL, the median increase in blood CD4(+) T-cell count was 162 cells per mL (IQR = 45-304 cells per mL).

CONCLUSIONS

In routine practice, a high rate of patients with extensive ARV experience, who received an optimized salvage regimen recommended by a peer advisory committee, achieved a long-term sustained virologic response and immune reconstitution.

HIV-1 disease progression during highly active antiretroviral therapy: an application using population-level data in British Columbia: 1996-2011

BACKGROUND

Accurately estimating rates of disease progression is of central importance in developing mathematical models used to project outcomes and guide resource allocation decisions. Our objective was to specify a multivariate regression model to estimate changes in disease progression among individuals on highly active antiretroviral treatment in British Columbia, Canada, 1996-2011.

METHODS

We used population-level data on disease progression and antiretroviral treatment utilization from the BC HIV Drug Treatment Program. Disease progression was captured using longitudinal CD4 and plasma viral load testing data, linked with data on antiretroviral treatment. The study outcome was categorized into (CD4 count ≥ 500, 500-350, 350-200, <200 cells/mm, and mortality). A 5-state continuous-time Markov model was used to estimate covariate-specific probabilities of CD4 progression, focusing on temporal changes during the study period.

RESULTS

A total of 210,083 CD4 measurements among 7421 individuals with HIV/AIDS were included in the study. Results of the multivariate model suggested that current highly active antiretroviral treatment at baseline, lower baseline CD4 (<200 cells/mm), and extended durations of elevated plasma viral load were each associated with accelerated progression. Immunological improvement was accelerated significantly from 2004 onward, with 23% and 46% increases in the probability of CD4 improvement from the fourth CD4 stratum (CD4 < 200) in 2004-2008 and 2008-2011, respectively.

CONCLUSION

Our results demonstrate the impact of innovations in antiretroviral treatment and treatment delivery at the population level. These results can be used to estimate a transition probability matrix flexible to changes in the observed mix of clients in different clinical stages and treatment regimens over time.

Cost-Effectiveness of Antiretroviral Therapy for Multidrug-Resistant HIV: Past, Present, and Future

In the early years of the highly active antiretroviral therapy (HAART) era, HIV with resistance to two or more agents in different antiretroviral classes posed a significant clinical challenge. Multidrug-resistant (MDR) HIV was an important cause of treatment failure, morbidity, and mortality. Treatment options at the time were limited; multiple drug regimens with or without enfuvirtide were used with some success but proved to be difficult to sustain for reasons of tolerability, toxicity, and cost. Starting in 2006, data began to emerge supporting the use of new drugs from the original antiretroviral classes (tipranavir, darunavir, and etravirine) and drugs from new classes (raltegravir and maraviroc) for the treatment of MDR HIV. Their availability has enabled patients with MDR HIV to achieve full and durable viral suppression with more compact and cost-effective regimens including at least two and often three fully active agents. The emergence of drug-resistant HIV is expected to continue to become less frequent in the future, driven by improvements in the convenience, tolerability, efficacy, and durability of first-line HAART regimens. To continue this trend, the optimal rollout of HAART in both rich and resource-limited settings will require careful planning and strategic use of antiretroviral drugs and monitoring technologies.

Standing genetic variation and the evolution of drug resistance in HIV

Drug resistance remains a major problem for the treatment of HIV. Resistance can occur due to mutations that were present before treatment starts or due to mutations that occur during treatment. The relative importance of these two sources is unknown. Resistance can also be transmitted between patients, but this process is not considered in the current study. We study three different situations in which HIV drug resistance may evolve: starting triple-drug therapy, treatment with a single dose of nevirapine and interruption of treatment. For each of these three cases good data are available from literature, which allows us to estimate the probability that resistance evolves from standing genetic variation. Depending on the treatment we find probabilities of the evolution of drug resistance due to standing genetic variation between and . For patients who start triple-drug combination therapy, we find that drug resistance evolves from standing genetic variation in approximately 6% of the patients. We use a population-dynamic and population-genetic model to understand the observations and to estimate important evolutionary parameters under the assumption that treatment failure is caused by the fixation of a single drug resistance mutation. We find that both the effective population size of the virus before treatment, and the fitness of the resistant mutant during treatment, are key-parameters which determine the probability that resistance evolves from standing genetic variation. Importantly, clinical data indicate that both of these parameters can be manipulated by the kind of treatment that is used.

For HIV patients who are treated with antiretroviral drugs, treatment usually works well. However, the virus can, and sometimes does, become resistant against one or more drugs. HIV drug resistance results from the acquisition of specific and well known mutations. It is currently unknown whether drug resistance mutations usually stem from standing genetic variation, i.e., they were already present at low frequency before treatment started, or whether they tend to occur during treatment. In the current manuscript, I make use of several large datasets and evolutionary modeling to estimate the probability that drug resistance mutations are present before treatment starts and lead to viral failure. I find that for the most common type of treatment with a combination of three drugs, drug resistance evolves from pre-existing mutations in 6% of the patients. With other types of treatment, this probability varies from 0 to 39%. I conclude that there is room for improvement in preventing the evolution of drug resistance from pre-existing mutations.

Missing data on the estimation of the prevalence of accumulated human immunodeficiency virus drug resistance in patients treated with antiretroviral drugs in north america

Determination of the prevalence of accumulated antiretroviral drug resistance among persons infected with human immunodeficiency virus (HIV) is complicated by the lack of routine measurement in clinical care. By using data from 8 clinic-based cohorts from the North American AIDS Cohort Collaboration on Research and Design, drug-resistance mutations from those with genotype tests were determined and scored using the Genotypic Resistance Interpretation Algorithm developed at Stanford University. For each year from 2000 through 2005, the prevalence was calculated using data from the tested subset, assumptions that incorporated clinical knowledge, and multiple imputation methods to yield a complete data set. A total of 9,289 patients contributed data to the analysis; 3,959 had at least 1 viral load above 1,000 copies/mL, of whom 2,962 (75%) had undergone at least 1 genotype test. Using these methods, the authors estimated that the prevalence of accumulated resistance to 2 or more antiretroviral drug classes had increased from 14% in 2000 to 17% in 2005 (P < 0.001). In contrast, the prevalence of resistance in the tested subset declined from 57% to 36% for 2 or more classes. The authors' use of clinical knowledge and multiple imputation methods revealed trends in HIV drug resistance among patients in care that were markedly different from those observed using only data from patients who had undergone genotype tests.