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HPTN 083 demonstrated that injectable cabotegravir (CAB) was superior to oral tenofovir disoproxil fumarate-emtricitabine (TDF-FTC) for HIV prevention in cisgender men and transgender women who have sex with men. We previously analyzed 58 infections in the blinded phase of HPTN 083 (16 in the CAB arm and 42 in the TDF-FTC arm). This report describes 52 additional infections that occurred up to 1 year after study unblinding (18 in the CAB arm and 34 in the TDF-FTC arm). Retrospective testing included HIV testing, viral load testing, quantification of study drug concentrations, and drug resistance testing. The new CAB arm infections included 7 with CAB administration within 6 months of the first HIV-positive visit (2 with on-time injections, 3 with ≥1 delayed injection, and 2 who restarted CAB) and 11 with no recent CAB administration. Three cases had integrase strand transfer inhibitor (INSTI) resistance (2 with on-time injections and 1 who restarted CAB). Among 34 CAB infections analyzed to date, diagnosis delays and INSTI resistance were significantly more common in infections with CAB administration within 6 months of the first HIV-positive visit. This report further characterizes HIV infections in persons receiving CAB preexposure prophylaxis and helps define the impact of CAB on the detection of infection and the emergence of INSTI resistance.

BackgroundThe HPTN 083 trial demonstrated that long-acting cabotegravir (CAB-LA) was superior to tenofovir-disoproxil fumarate/emtricitabine for human immunodeficiency virus (HIV) preexposure prophylaxis (PrEP). Integrase strand transfer inhibitor (INSTI) resistance-associated mutations (RAMs) were detected in some participants with HIV infection. We used a low viral load INSTI genotyping assay to evaluate the timing of emergence of INSTI RAMs and assessed whether HIV screening with a sensitive RNA assay would have detected HIV infection before INSTI resistance emerged.MethodsSingle-genome sequencing to detect INSTI RAMs was performed for samples with viral loads

: Introduction: HPTN 083 demonstrated the superiority of long‐acting cabotegravir (CAB‐LA) versus daily oral emtricitabine/tenofovir disoproxil fumarate (TDF/FTC) as pre‐exposure prophylaxis (PrEP) among cisgender men and transgender women who have sex with men (MSM/TGW). HPTN 083 provided the first opportunity to understand experiences with injectable PrEP in a clinical trial. Methods: Participants from two US sites (Chicago, IL and Atlanta, GA) and one international site (Rio de Janeiro, Brazil) were purposively sampled for individual qualitative interviews (N = 40), between November 2019 and March 2020, to explore trial experiences, barriers to adherence and other factors that may have impacted study implementation or outcomes. The blinded phase ended early due to efficacy; this analysis includes interviews conducted prior to unblinding with three groups defined by adherence (i.e. injection visit attendance): adherent (n = 27), non‐adherent (n = 12) and early discontinuers (n = 1). Data were organized using NVivo software and analysed using content analysis. Results: Participants (mean age: 27) were primarily cisgender MSM (90%) and Black/African American (60%). Reasons for trial enrolment and PrEP use included a preference for using HIV prevention medication versus treatment in the event of HIV acquisition; the ability to enhance health via study‐related education and services; access to a novel, convenient HIV prevention product at no cost; and contributing to MSM/TGW communities through research. Participants contrasted positive experiences with study staff with their routine clinical care, and emphasized increased scheduling flexibility, thorough communication, non‐judgemental counselling and open, affirming environments (e.g. compassion, less stigma) as adherence facilitators. Injection experiences were positive overall; some described early injection‐related anxiety, which abated with time and when given some measure of control (e.g. pre‐injection countdown), and minimal injection site discomfort. Some concerns and misperceptions about injectable PrEP were reported. Barriers to adherence, across all adherence categories, included structural factors (e.g. financial constraints, travel) and competing demands (e.g. work schedules). Conclusions: Respondents viewed injectable PrEP trial participation as a positive experience and a means of enhancing wellbeing. Study site flexibility and affirming clinic environments, inclusive of non‐judgemental counselling, were key facilitators of adherence. To support injection persistence, interventions that address structural barriers and promote flexible means of injection delivery may be most effective., INTRODUCTION HIV Prevention Trials Network (HPTN) 083 was the first large‐scale, randomized, double‐blind efficacy trial of long‐acting injectable cabotegravir (CAB‐LA) versus daily oral emtricitabine/tenofovir disoproxil fumarate (TDF/FTC) as pre‐exposure prophylaxis [...]

[This corrects the article DOI: 10.1021/acsptsci.0c00181.].

Cabotegravir (CAB) is an integrase strand-transfer inhibitor of HIV that has proven effective for HIV treatment and prevention in a long-acting injectable formulation, typically preceded by an oral formulation lead-in phase. Previous in vitro studies have demonstrated that CAB is primarily metabolized via glucuronidation by uridine diphosphate glucuronosyltransferase (UGT) 1A1 and 1A9. In this study, we performed next-generation sequencing of genomic DNA isolated from the HPTN 077 participants to explore the variants within UGT1A1 and UGT1A9. Additionally, to enable correlation of UGT1A1 and UGT1A9 genotypes with plasma CAB-glucuronide levels, we quantified glucuronidated CAB following both oral administration of CAB and intramuscular injection of long-acting CAB. From these studies, 48 previously unreported variants of UGT1A1 and UGT1A9 were detected. Notably, 5/68 individuals carried a UGT1A1 454C>A variant that resulted in amino acid substitution P152T, and the use of in silico tools predicted a deleterious effect of the P152T substitution. Thus, the impact of this mutant on a range of UGT1A1 substrates was tested using a COS-7 cell-based assay. The glucuronide conjugates of CAB, dolutegravir, and raltegravir, were not formed in the COS-7 cells expressing the UGT1A1 P152T mutant. Further, formation of glucuronides of raloxifene and 7-ethyl-10-hydroxycamptothecin were reduced in the cells expressing the UGT1A1 P152T mutant. Using the same approach, we tested the activities of two UGT1A9 mutants, UGT1A9 H217Y and UGT1A9 R464G, and found that these mutations were tolerated and decreased function, respectively. These data provide insight into previously unreported genetic variants of UGT1A1 and UGT1A9.

ObjectivesTo evaluate whether hormonal contraceptive use among cisgender women is associated with differences in pharmacokinetic (PK) parameters of a long-acting injectable formulation of the integrase strand transfer inhibitor, cabotegravir (CAB-LA).SettingThis is a secondary analysis of 85 cisgender women enrolled in HPTN 077, a phase 2a multicenter study that enrolled HIV-uninfected, low-risk individuals in Malawi, Brazil, South Africa, and the United States.MethodsParticipants received 4-week daily oral cabotegravir lead-in, followed by CAB-LA 800 mg injection every 12 weeks (cohort 1) or 600 mg every 8 weeks (after 4-week initial interval between injections, cohort 2), over 41 weeks. Participants were followed 52-76 weeks subsequent to final injection. Generalized estimating equations and linear regression were used to evaluate differences in CAB-LA PK parameters (peak concentration, trough concentration, area under the curve, apparent terminal half-life, and time to lower limit of quantification) and self-reported hormonal contraceptive stratified by type (oral, injectable, implants, and other), controlling for body mass index and cohort.ResultsCompared to women reporting no hormonal contraception (n = 6), oral contraceptive use (n = 18) was associated with lower CAB-LA peak concentration but was not associated with differences in other PK parameters. No other hormonal contraceptive type (injectable, implants, and other) was associated with significant differences in CAB-LA PK parameters.ConclusionAlthough oral contraceptive use was associated with differences in CAB-LA peak concentration, no differences were observed in other PK parameters, suggesting that this association is not likely to be clinically significant. However, these data highlight the need for further research exploring potential drug-drug interactions between CAB-LA and hormonal contraceptives.

BackgroundCabotegravir (CAB) is a novel strand-transfer integrase inhibitor being developed for HIV treatment and prevention. CAB is formulated both as an immediate-release oral tablet for daily administration and as a long-acting injectable suspension (long-acting CAB [CAB LA]) for intramuscular (IM) administration, which delivers prolonged plasma exposure to the drug after IM injection. HIV Prevention Trials Network study 077 (HPTN 077) evaluated the safety, tolerability, and pharmacokinetics of CAB LA in HIV-uninfected males and females at 8 sites in Brazil, Malawi, South Africa, and the United States.Methods and findingsHPTN 077 was a double-blind, placebo-controlled phase 2a trial. Healthy individuals age 18-65 years at low HIV risk were randomized (3:1) to receive CAB or placebo (PBO). In the initial oral phase, participants received 1 daily oral tablet (CAB or PBO) for 4 weeks. Those without safety concerns in the oral phase continued and received injections in the injection phase (Cohort 1: 3 injections of CAB LA 800 mg or 0.9% saline as PBO IM every 12 weeks for 3 injection cycles; Cohort 2: CAB LA 600 mg or PBO IM for 5 injection cycles; the first 2 injections in Cohort 2 were separated by 4 weeks, the rest by 8 weeks). The primary analysis included weeks 5 to 41 of study participation, encompassing the injection phase. The cohorts were enrolled sequentially. Primary outcomes were safety and tolerability. Secondary outcomes included pharmacokinetics and events occurring during the oral and injection phases. Between February 9, 2015, and May 27, 2016, the study screened 443 individuals and enrolled 110 participants in Cohort 1 and 89 eligible participants in Cohort 2. Participant population characteristics were as follows: 66% female at birth; median age 31 years; 27% non-Hispanic white, 41% non-Hispanic black, 24% Hispanic/Latino, 3% Asian, and 6% mixed/other; and 6 transgender men and 1 transgender woman. Twenty-two (11%) participants discontinued the oral study product; 6 of these were for clinical or laboratory adverse events (AEs). Of those who received at least 1 CAB LA injection, 80% of Cohort 1 and 92% of Cohort 2 participants completed all injections; injection course completion rates were not different from those in the PBO arm. Injection site reactions (ISRs) were common (92% of Cohort 1 and 88% of Cohort 2 participants who received CAB LA reported any ISR). ISRs were mostly Grade 1 (mild) to Grade 2 (moderate), and 1 ISR event (Cohort 1) led to product discontinuation. Grade 2 or higher ISRs were the only AEs reported more commonly among CAB LA recipients than PBO recipients. Two Grade 3 (severe) ISRs occurred in CAB recipients, 1 in each cohort, but did not lead to product discontinuation in either case. Seven incident sexually transmitted infections were diagnosed in 6 participants. One HIV infection occurred in a participant 48 weeks after last injection of CAB LA: CAB was not detectable in plasma both at the time of first reactive HIV test and at the study visit 12 weeks prior to the first reactive test. Participants in Cohort 2 (unlike Cohort 1) consistently met prespecified pharmacokinetic targets of at least 95% of participants maintaining CAB trough concentrations above PA-IC90, and 80% maintaining trough concentrations above 4× PA-IC90. Study limitations include a modest sample size, a short course of injections, and a low-risk study population.ConclusionsIn this study, CAB LA was well tolerated at the doses and dosing intervals used. ISRs were common, but infrequently led to product discontinuation. CAB LA 600 mg every 8 weeks met pharmacokinetic targets for both male and female study participants. The safety and pharmacokinetic results observed support the further development of CAB LA, and efficacy studies of CAB LA for HIV treatment and prevention are in progress.Trial registrationClinicalTrials.gov Registry: ClinicalTrials.gov Trial number: NCT02178800.

BackgroundMaraviroc (MVC) is a candidate drug for HIV preexposure prophylaxis (PrEP).ObjectiveTo assess the safety and tolerability of MVC-containing PrEP over 48 weeks in U.S. women at risk for HIV infection.DesignPhase 2 randomized, controlled, double-blinded study of 4 antiretroviral regimens used as PrEP. (ClinicalTrials.gov: NCT01505114).Setting12 clinical research sites of the HIV Prevention Trials Network and AIDS Clinical Trials Group.ParticipantsHIV-uninfected women reporting condomless vaginal or anal intercourse with at least 1 man with HIV infection or unknown serostatus within 90 days.InterventionMVC only, MVC-emtricitabine (FTC), MVC-tenofovir disoproxil fumarate (TDF), and TDF-FTC (control).MeasurementsAt each visit, clinical and laboratory (including HIV) assessments were done. Primary outcomes were grade 3 and 4 adverse events and time to permanent discontinuation of the study regimen. All randomly assigned participants were analyzed according to their original assignment.ResultsAmong 188 participants, 85% completed follow-up, 11% withdrew early, and 4% were lost to follow-up; 19% discontinued their regimen prematurely. The number discontinuing and the time to discontinuation did not differ among regimens. Grade 3 or 4 adverse events occurred in 5 (MVC), 13 (MVC-FTC), 9 (MVC-TDF), and 8 (TDF-FTC) participants; rates did not differ among regimens. One death (by suicide) occurred in the MVC-TDF group but was judged not to be related to study drugs. Of available plasma samples at week 48 (n = 126), 60% showed detectable drug concentrations. No new HIV infections occurred.LimitationsParticipants were not necessarily at high risk for HIV infection. The regimen comprised 3 pills taken daily. The study was not powered for efficacy.ConclusionMaraviroc-containing PrEP regimens were safe and well-tolerated compared with TDF-FTC in U.S. women. No new HIV infections occurred, although whether this was due to study drugs or low risk in the population is uncertain. Maraviroc-containing PrEP for women may warrant further study.Primary funding sourceNational Institutes of Health.

BackgroundMaraviroc (MVC) is a candidate for human immunodeficiency virus (HIV) pre-exposure prophylaxis.MethodsPhase 2 48-week safety/tolerability study was conducted, comparing 4 regimens: MVC alone, MVC plus emtricitabine (FTC), MVC plus tenofovir disoproxil fumarate (TDF), and TDF plus FTC. Eligible participants were HIV-uninfected men and transgender women reporting condomless anal intercourse with ≥1 HIV-infected or unknown-serostatus man within 90 days. At each visit, assessments, laboratory testing, and counseling were done. Analyses were intention to treat.ResultsAmong 406 participants, 84% completed follow-up, 7% stopped early, and 9% were lost to follow-up; 9% discontinued their regimen early. The number discontinuing and the time to discontinuation did not differ among study regimens (P = .60). Rates of grade 3-4 adverse events did not differ among regimens (P = .37). In a randomly selected subset, 77% demonstrated detectable drug concentrations at week 48. Five participants acquired HIV infection (4 MVC alone, 1 MVC + TDF; overall annualized incidence, 1.4% [95% confidence interval, .5%-3.3%], without differences by regimen; P = .32); 2 had undetectable drug concentrations at every visit, 2 had low concentrations at the seroconversion visit, and 1 had variable concentrations.ConclusionsMVC-containing regimens were safe and well tolerated compared with TDF + FTC; this study was not powered for efficacy. Among those acquiring HIV infection, drug concentrations were absent, low, or variable. MVC-containing regimens may warrant further study for pre-exposure prophylaxis.Clinical trials registrationNCT01505114.

Cabotegravir long-acting injectable HIV pre-exposure prophylaxis (LA PrEP) is efficacious, with a good safety profile, and was approved by the US Food and Drug Administration in December 2021. Understanding variations in potential user preferences for LA PrEP may inform implementation and subsequently improve uptake and community-level effectiveness. HIV-negative, sexually active men who have sex with men (MSM) aged ≥15 years were recruited online for the 2019 American Men's Internet Survey, before LA PrEP approval. Respondents completed a discrete-choice experiment (DCE) with hypothetical LA PrEP attributes (out-of-pocket cost, perceived side effects, injection frequency, perceived stigma, service location). Latent class analysis segmented respondents into groups based on their preferences for the attributes presented, and relative importance of preference weights and willingness-to-pay were calculated. While the majority had never used daily oral PrEP, 73% of the 2489 respondents were very or somewhat likely to use LA PrEP. Three latent classes were identified from 2241 respondents in the DCE. The "side effects-averse" class was the largest group (64% of respondents) and placed 61% relative importance on side effects. The "ambivalent" class (20% of respondents) placed higher importance on stigma (17% of relative importance) than other classes. The "cost-conscious" class (16% of respondents) placed higher relative importance (62%) on cost compared with other attributes and classes. Perceived side effects were an important hypothetical barrier for LA PrEP uptake among a large proportion of potential MSM users. Minimizing out-of-pocket costs is likely to increase uptake and may be important to equitable access. Tailored communication strategies are recommended for the different groups of potential LA PrEP users. [ABSTRACT FROM AUTHOR]

Detection of HIV infection may be challenging in persons using long-acting cabotegravir (CAB-LA) pre-exposure prophylaxis (PrEP) due to viral suppression and reduced/delayed antibody production. We evaluated two point-of-care tests for detecting HIV infection in persons who received CAB-LA in the HPTN 083 trial. Samples were obtained from 12 participants who received CAB-LA and had delayed detection of HIV infection using HIV rapid tests and an antigen/antibody test (52 plasma samples; 18 dried blood spot [DBS] samples). Plasma samples were tested with the Xpert HIV-1 Viral Load XC test (Xpert VL-XC); DBS samples were tested with the total nucleic acid Xpert HIV-1 Qual XC test (Xpert Qual-XC). Results from these assays were compared to results from three reference, laboratory-based, plasma RNA assays (Aptima HIV-1 Qualitative assay [Aptima Qual]; Aptima HIV-1 Quant DX Assay [Aptima Quant]; cobas HIV-1/HIV-2 Qualitative Test [cobas]). HIV RNA was detected with all four plasma assays for all samples with viral loads (VLs) ≥ 200 copies/mL; the number of samples with VLs < 200 copies/mL with HIV RNA detected was: Xpert VL-XC: 19/26 (73.1%); Aptima Qual: 17/26 (65.4%); Aptima Quant: 17/26 (65.4%); and cobas: 12/21 (57.1%). The Xpert Qual-XC assay was positive for all DBS samples with VLs ≥ 200 copies/mL and 1/10 DBS with VLs < 200 copies/mL. The performance of the Xpert VL-XC assay was comparable to the reference assays for detecting HIV infection in these cases. The Xpert Qual-XC assay was less sensitive than plasma-based HIV RNA assays for detecting HIV in the setting of CAB-LA PrEP., Importance: HIV RNA assays can detect HIV infections earlier than HIV rapid tests or Ag/Ab tests in persons using CAB-LA PrEP. Earlier HIV diagnosis could allow for earlier treatment initiation and reduced risk of INSTI resistance. POC tests may help detect HIV infection before CAB-LA administration and may be more accessible than laboratory-based assays in some settings. In this study, the POC Xpert VL-XC assay detected HIV RNA in most samples from individuals who received CAB-LA PrEP and had delayed detection of HIV infection with HIV rapid tests and an Ag/Ab test. The performance of this assay was similar to laboratory-based HIV RNA assays in this cohort. The POC Xpert Qual-XC assay detects both HIV RNA and DNA, with a higher viral load cutoff for RNA detection. This assay was negative for most lower viral load samples and did not offer an advantage for HIV screening in persons using CAB-LA PrEP.

Long-acting cabotegravir is approved for pre-exposure prophylaxis and combination HIV treatment, both initiated with optional short-term oral lead-in (OLI). We evaluated the impact of OLI on long-acting cabotegravir pharmacokinetics. Cabotegravir plasma concentrations were compared between HIV-positive participants initiating injections with ( n = 278) or without ( n = 110) OLI in phase III treatment study FLAIR and in HIV-negative participants using OLI ( n = 263) in pivotal pre-exposure prophylaxis studies HPTN 083 and HPTN 084. Cabotegravir pharmacokinetic profiles were simulated in three populations (assigned-male-at-birth, 50%-assigned-female-at-birth, and assigned-female-at-birth) under three scenarios: first injection given (A) 1 or (B) 3 days after final OLI dose (OLI-injection gap) or (C) without OLI. The PK objective was 80% of participants achieving 4× in vitro protein-adjusted 90% maximal inhibitory concentration (PA-IC 90 ) and 50% achieving 8× PA-IC 90 . Observed trough concentrations ( C τ ) were similar with and without OLI ( P > 0.3). With a 3-day OLI-injection gap, simulated pre-injection C τ remained above PK objective. Approximately 1-2 weeks after the first injection, simulated PK profiles became nearly identical among all scenarios. Without OLI, it was predicted that 80% of participants achieve 4× PA-IC 90 in 1.2, 1.8, and 2.8 days after the first injection in each population, respectively, and 50% achieve 8× PA-IC 90 in 1.4, 2.1, and 3.8 days, respectively. Observed long-acting cabotegravir exposure was similar with or without OLI, supporting optional OLI use. Cabotegravir exposure was predicted to remain above PK objective for OLI-injection gaps of ≤3 days and rapidly achieve PK objective after first injection without OLI. Findings are consistent between assigned-male-at-birth and assigned-female-at-birth populations.This study is registered with ClinicalTrials.gov as NCT02720094.

Objectives: To evaluate whether hormonal contraceptive use among cisgender women is associated with differences in pharmacokinetic (PK) parameters of a long-acting injectable formulation of the integrase strand transfer inhibitor, cabotegravir (CAB-LA)., Setting: This is a secondary analysis of 85 cisgender women enrolled in HPTN 077, a phase 2a multicenter study that enrolled HIV-uninfected, low-risk individuals in Malawi, Brazil, South Africa, and the United States., Methods: Participants received 4-week daily oral cabotegravir lead-in, followed by CAB-LA 800 mg injection every 12 weeks (cohort 1) or 600 mg every 8 weeks (after 4-week initial interval between injections, cohort 2), over 41 weeks. Participants were followed 52-76 weeks subsequent to final injection. Generalized estimating equations and linear regression were used to evaluate differences in CAB-LA PK parameters (peak concentration, trough concentration, area under the curve, apparent terminal half-life, and time to lower limit of quantification) and self-reported hormonal contraceptive stratified by type (oral, injectable, implants, and other), controlling for body mass index and cohort., Results: Compared to women reporting no hormonal contraception (n = 6), oral contraceptive use (n = 18) was associated with lower CAB-LA peak concentration but was not associated with differences in other PK parameters. No other hormonal contraceptive type (injectable, implants, and other) was associated with significant differences in CAB-LA PK parameters., Conclusion: Although oral contraceptive use was associated with differences in CAB-LA peak concentration, no differences were observed in other PK parameters, suggesting that this association is not likely to be clinically significant. However, these data highlight the need for further research exploring potential drug-drug interactions between CAB-LA and hormonal contraceptives.

Objective: This study was performed to evaluate a once-daily dual-therapy regimen, maraviroc (MVC) + atazanavir/ritonavir (ATV/r), in treatment-naive patients., Design: A phase 2b, randomized, open-label pilot study., Methods: In Study A4001078 (NCT00827112), treatment-naive patients with CCR5-tropic HIV-1 (HIV-1 RNA ≥1000 copies/mL; CD4 cell count ≥100 cells/mm) were randomized to receive either MVC 150 mg once daily (n = 60) or tenofovir/emtricitabine (TDF/FTC) 300/200 mg once daily (n = 61) + ATV/r 300/100 mg once daily. Primary endpoint was proportion of patients with HIV-1 RNA <50 copies per milliliter at week 48., Results: At week 48, 44 (74.6%) and 51 (83.6%) patients in the MVC and TDF/FTC treatment groups, respectively, had plasma HIV-1 RNA <50 copies per milliliter. Median change from baseline in CD4 cell count at week 48 was +173 and +187 cells per cubic millimeter with MVC and TDF/FTC, respectively. Seven patients discontinued from each arm; there were no deaths. The incidence of serious adverse events (AEs) was similar in each group; however, there were more grade 3/4 AEs in the MVC group (18 vs 11), mostly due to hyperbilirubinemia. Three patients in each arm were evaluable for virological analysis at discontinuation or failure (HIV-1 RNA >500 copies/mL); no genotypic resistance, change in tropism, or loss of susceptibility relevant to treatment was observed., Conclusions: The virological activity and immunological benefit of once-daily MVC + ATV/r were confirmed. Indirect hyperbilirubinemia and associated signs were the most commonly reported AEs in both study treatment groups and were not associated with significant transaminase increases. No drug resistance occurred.

We compared viroimmunologic response after real phenotype (r-PHT) versus virtual phenotype (v-PHT) in patients failing highly active antiretroviral therapy (HAART). A total of 201 patients with >2 years of exposure, more than six experienced drugs, >1000 HIV RNA copies/mL, and on stable HAART for >6 months were randomized to the r-PHT or v-PHT arm. The primary end point was the proportion of HIV plasma viral load (pVL) <400 copies/mL. Secondary end points were absolute pVL change, proportion of pVL reduction >0.5 log(10) copies/mL, and absolute CD4 cell change. In the intention-to-treat-last observation carried forward analysis, study outcomes were not significantly different between arms over 48 weeks of follow-up: 20% and 24% pVL <400 copies/mL; 58% and 61% pVL reduction >0.5 log(10) copies/mL; -0.92 and -0.94(10) log copies/mL mean pVL decrease; and +41.6 and +94.4 cells/mm(3) mean absolute CD4 increase in the r-PHT and v-PHT arms, respectively. On-treatment analyses gave similar results. In the multivariate analysis of pVL <400 copies/mL, the following covariates were independent predictors at week 48: adherence (OR p= 0.25; p=.002), baseline CD4 (OR = 4.39; p=.007), intravenous drug use as risk factor for HIV acquisition (OR = 0.33; p=.024), and sensitivity score of the new regimens by biologic cut-offs (OR = 1.84; p=.029). Prescribed drugs for which patients were naive resulted in marginal prediction (OR = 1.93; p=.054). In conclusion, virologic and immunologic outcomes did not differ when r-PHT or v-PHT was used in this cohort of heavily pretreated patients. Several factors should be considered to take better advantage of resistance testing, including treatment history, clinical status, and patients' ability to adhere to treatment.