Edward P. Acosta

Adherence-resistance relationships for protease and non-nucleoside reverse transcriptase inhibitors explained by virological fitness.

Objective:To compare the prevalence of resistance by adherence level in patients treated with non-nucleoside reverse transcriptase inhibitors (NNRTI) or protease inhibitors (PI). Also to examine the mechanism of differential class-specific adherence–resistance relationships, focusing on the patient-derived capacity of wild-type and drug-resistant recombinant variants to replicate in vitro in the presence of variable drug levels. Methods:Participants received unannounced pill count measures to assess adherence, viral load monitoring, and genotypic resistance testing. The replicative capacity of drug-susceptible and drug-resistant recombinants was determined using a single-cycle recombinant phenotypic susceptibility assay. Drug exposure was estimated using population-averaged pharmacological measurements adjusted by participant-specific levels of adherence. Results:In the NNRTI-treated group, 69% had resistance at 0–48% adherence compared to 13% at 95–100% (P = 0.01). PI resistance was less common than NNRTI resistance at 0–48% adherence (69% versus 23%; P = 0.01). In multivariate analysis, the odds for PI resistance increased (P = 0.03) while the odds for NNRTI resistance decreased (P = 0.04) with improving adherence. Individuals with drug-resistant variants were more likely to have levels of drug exposure where the resistant variant was more fit than the drug-susceptible variant in vitro, while those with drug-susceptible virus were more likely to have levels of drug exposure where the drug-susceptible virus was more fit than the drug-resistant variant (P = 0.005). Conclusions:NNRTI resistance was more common than PI resistance at low levels of adherence. Class-specific adherence–resistance relationships are associated with the relative replicative capacity of drug-resistant versus wild-type variants to replicate in the presence of clinically relevant drug levels.

Dose-response curve slope sets class-specific limits on inhibitory potential of anti-HIV drugs

Highly active antiretroviral therapy (HAART) can control HIV-1 replication, but suboptimal treatment allows for the evolution of resistance and rebound viremia. A comparative measure of antiviral activity under clinically relevant conditions would guide drug development and the selection of regimens that maximally suppress replication. Here we show that current measures of antiviral activity, including IC50 and inhibitory quotient, neglect a key dimension, the dose-response curve slope. Using infectivity assays with wide dynamic range, we show that this slope has noteworthy effects on antiviral activity. Slope values are class specific for antiviral drugs and define intrinsic limitations on antiviral activity for some classes. Nucleoside reverse transcriptase inhibitors and integrase inhibitors have slopes of ∼1, characteristic of noncooperative reactions, whereas non-nucleoside reverse transcriptase inhibitors, protease inhibitors and fusion inhibitors unexpectedly show slopes >1. Instantaneous inhibitory potential (IIP), the log reduction in single-round infectivity at clinical drug concentrations, is strongly influenced by slope and varies by >8 logs for anti-HIV drugs. IIP provides a more accurate measure of antiviral activity and in general correlates with clinical outcomes. Only agents with slopes >1 achieve high-level inhibition of single-round infectivity, a finding with profound implications for drug and vaccine development.

Impact of Efavirenz on Neuropsychological Performance and Symptoms in HIV-Infected Individuals

Context Neurologic toxicity is the most commonly reported adverse effect of the antiretroviral drug efavirenz. Contribution In this substudy of a randomized, controlled trial, 12 of 200 (6%) HIV-infected individuals discontinued treatment with efavirenz because of central nervous system symptoms or mood disorders versus 0 of 103 individuals (0%) who were not receiving the drug. Although patients taking efavirenz had more neuropsychological symptoms, such as bad dreams, in the first week of therapy, no statistically significant neuropsychological differences were found at weeks 4, 12, and 24. Implications Some adverse neuropsychological effects associated with efavirenz are probably transient. The Editors Efavirenz is a non-nucleoside reverse transcriptase inhibitor approved for treatment of HIV infection. The drug is potent, is generally well tolerated, and can be administered once daily, making it a preferred treatment option for HIV infection (1, 2). The most commonly reported adverse effect with efavirenz is neurologic toxicity, with more than 50% of patients reporting symptoms in open-label studies (1, 3). Our randomized, controlled study prospectively characterized aspects of the neurologic toxicity of 3 protease inhibitorsparing antiretroviral regimens for the initial treatment of HIV infection. Methods This investigator-initiated trial was a substudy of the AIDS Clinical Trials Group study A5095, a randomized, double-blind trial of 3 antiretroviral regimens: zidovudine and lamivudine in combination with efavirenz; abacavir; or abacavir and efavirenz in combination (4). For simplicity, we will refer to 2 groups: patients who received efavirenz (with or without abacavir) and those who did not. Randomization was performed centrally without reference to center. The study was supported by the National Institutes of Health (NIH) and was approved by the institutional review boards at each of the participating institutions, with each patient providing informed consent to participate in the substudy. All patients at sites taking part in the substudy were invited to participate before randomization for the parent study (Figure 1). Unblinding and within-class substitutions were allowed in cases of treatment-limiting toxicity (we substituted stavudine for zidovudine, didanosine for abacavir, and nevirapine for efavirenz). Participants had not previously received antiretroviral therapy, and their baseline plasma HIV-1 RNA levels were greater than 400 copies/mL. Parent study A5095 enrolled 1147 participants, of whom 303 at 36 clinical trials units volunteered to participate in the additional evaluations for A5097s. Participants were recruited between March 2001 and January 2002. Figure 1. CONSORT diagram of substudy 5097s. The primary measures of neuropsychological performance were the Trail Making Tests (Parts A and B) and the Digit Symbol Substitution Test (part of the Wechsler Adult Intelligence Scale III [5]). A summary neuropsychological Z score (NPZ3) was derived from the sum of the scores from these 3 tests and standardized for age. Positive scores indicated above-normal function, whereas negative scores indicated below-normal function. The entire score was coded as missing if any component of the NPZ3 was not available. The Neurologic AIDS Research Consortium provided administrator training at each site. These tests assessed functioning in the areas of motor persistence, sustained attention, response speed, visuomotor coordination, and conceptual shifting and tracking. Neuropsychometric measures were collected at baseline and at weeks 1, 4, 12, and 24. Testing was performed at each time point to assess symptoms that might be associated with efavirenz use, sleep disorders, anxiety, depression, and history of drug abuse. The instruments are summarized in Table 1. The symptom questionnaire developed for this study is shown in the Appendix Figure. Appendix Figure. Sample participant questionnaire. Table 1. Testing Instruments Whole blood was collected from all participants to determine efavirenz trough concentrations in plasma (13). These data were used to explore relationships between drug exposure and other variables that were evaluated in the study. Statistical Analysis Our substudy was designed to compare neurologic changes from baseline in patients who received efavirenz with changes in those who did not. The study had 90% power to detect a standard deviation of 0.4 for change in the summary neuropsychological performance score from baseline to week 1. We presented descriptive statistics for the study sample and used nonparametric tests to determine treatment differences. Using the nonparametric methods of Hodges and Lehmann (14) and Proc-StatXact software, version 4.0.1 (Cytel Software Corp., Cambridge, Massachusetts), we estimated treatment differences for continuous outcomes with corresponding exact confidence intervals. Generalized estimating equation modeling (a regression method) and the Wei-Johnson test (a nonparametric method for analyzing incomplete 2-sample data) (15) were used to compare treatment groups longitudinally; both methods assumed that data were missing completely at random. We used the Spearman correlation coefficient, a rank-based method that is robust to extreme observations, to evaluate correlations. All significance testing was performed at an level of 0.05 with no adjustment for multiple testing. All reported P values were 2-sided. To assess the potential effect of any missing data, we performed multiple imputation, analyzed 2 worst-case scenarios (Appendix Table 1 and Appendix Table 2), and conducted an as-treated analysis that excluded patients who discontinued efavirenz therapy. We used SAS software (SAS Institute, Inc., Cary, North Carolina) to perform statistical analyses. Test sources included Elsevier Science (Oxford, United Kingdom) for the Pittsburgh Sleep Quality Index, Mind Garden (Redwood City, California) for the State-Trait Anxiety Inventory for Adults, and the National Institute of Mental Health (Bethesda, Maryland) for the Center for Epidemiologic Studies Depression Scale. Role of the Funding Sources This investigator-initiated protocol was supported by the NIH. Drugs used in the study were donated by pharmaceutical companies whose representatives participated in team discussions. The study was monitored by NIH-contracted monitors and was supervised by a data safety monitoring committee that was appointed by the National Institute of Allergy and Infectious Diseases. The NIH-supported biostatistical team working with the AIDS Clinical Trials Group and the Neurologic AIDS Research Consortium performed the statistical analyses. The protocol team, led by the first author, had final responsibility for the study protocol, case report forms, statistical analysis plan, progress of the study, analysis, and reporting of the data, regardless of outcome. The final version was the sole responsibility of the authors. The team had full access to the data files of the study. Results Baseline Evaluations Recruitment characteristics are displayed in Figure 1; demographic characteristics of the study participants are presented in Table 2. The treatment groups were balanced at baseline with respect to demographic characteristics, neuropsychological measures, and responses to the symptom questionnaire. The sleep disturbance component of the global sleep index demonstrated a baseline difference; the patients who eventually received efavirenz had marginally more sleep disturbances (P= 0.048) (data not shown). Other components of the sleep index, including quality, latency, duration, efficiency, use of sleeping medication, and daytime dysfunction, were similar between groups. Alcohol abuse, drug use, and affective disturbances were infrequent and similar for both groups. Table 2. Baseline Characteristics and Evaluations by Treatment Group Disposition of Study Participants The study allowed for drug substitution from the same class of antiretroviral agents in cases of treatment-limiting toxicity. Table 3 summarizes the modifications that occurred and the respective reasons. Appendix Table 3 gives further details of timing of modifications and the ethnicity of the individuals. Primary end point data (the change in NPZ3 from baseline to week 1) were observed in 283 of the 303 (93.4%) participants. Table 3. Reasons for Modification of Treatment Appendix Table 1. Neuropsychological Performance Appendix Table 2. Results of Sensitivity Analysis by Generalized Estimating Equation Method Appendix Table 3. Status and Ethnicity of Patients Requiring Modification of Treatment Prospective Evaluations Median NPZ3 scores improved in both groups during the study, with the greatest change occurring in the first week of treatment (Figure 2). No statistically significant differences in changes in neuropsychological performance were observed between the groups at any time point. We conducted conventional longitudinal analyses to further investigate differences in neuropsychological scores between the treatment groups. On the basis of these analyses, we had insufficient evidence to conclude that there were treatment differences (generalized estimating equation modeling in which treatment was the only independent variable and an exchangeable correlation structure was assumed, P= 0.176; Wei-Johnson test, P= 0.196). Multiple sensitivity analyses were performed, including single and multiple imputation methods, as-treated analyses, and 2 forms of worst-case scenarios. Details of these analyses are shown in Appendix Table 1. Multiple imputation and as-treated analyses generally provided similar results to observed data at specific weeks; however, the worst-case analyses at weeks 4, 12, and 24 displayed significant differences between groups. These results suggest that differences between groups might exist if the worst-case scenario were true, that is, if patients without data who were receiving efavirenz had wors

Pharmacogenetics of Plasma Efavirenz Exposure after Treatment Discontinuation: An Adult AIDS Clinical Trials Group Study

BACKGROUND Efavirenz has a long plasma half-life and a low genetic barrier to resistance. Simultaneously stopping treatment with all agents in efavirenz-containing regimens may result in functional efavirenz monotherapy that selects for drug-resistant human immunodeficiency virus type 1. Lower plasma efavirenz clearance is associated with a cytochrome P450 2B6 gene (CYP2B6) polymorphism (516G-->T) that is more frequent among African American individuals than among European American individuals. METHODS We characterized relationships between this polymorphism and predicted plasma efavirenz concentration-time profiles after discontinuation of therapy with use of data obtained from subjects receiving therapy. Pharmacokinetic parameters were estimated using population-based methods. Concentrations after discontinuation of therapy were predicted from subject-specific estimates. RESULTS. Median estimated efavirenz half-lives were 23, 27, and 48 h for patients with CYP2B6 position 516 GG (78 patients), GT (60), and TT (14) genotypes, respectively (P<.001). After therapy was stopped, plasma efavirenz concentrations in patients with GG, GT, and TT genotypes were predicted to exceed 46.7 ng/mL (the estimated protein-adjusted 95% inhibitory concentration for wild-type virus) for a median of 5.8 days (interquartile range [IQR], 4.4-8.3 days), 7.0 days (IQR, 5.0-8.0 days), and 14 days (IQR, 11.1-21.2 days), respectively (P<.001). Plasma efavirenz levels were predicted to exceed 46.7 ng/mL for >21 days in 5% of subjects with GG genotype, 5% of subjects with GT genotype, and 29% of subjects with TT genotype. CONCLUSIONS The CYP2B6 position 516 TT genotype or a prolonged measured elimination half-life may predict increased risk of developing drug resistance among patients who discontinue efavirenz-containing regimens. This has implications for strategies to safely discontinue antiretroviral regimens while avoiding the emergence of drug resistance.

Short-Course Raltegravir Intensification Does Not Reduce Persistent Low-Level Viremia in Patients with HIV-1 Suppression during Receipt of Combination Antiretroviral Therapy

BACKGROUND Combination antiretroviral therapy suppresses but does not eradicate human immunodeficiency virus type 1 (HIV-1) in infected persons, and low-level viremia can be detected despite years of suppressive antiretroviral therapy. Short-course (28-day) intensification of standard antiretroviral combination therapy is a useful approach to determine whether complete rounds of HIV-1 replication in rapidly cycling cells contribute to persistent viremia. We investigated whether intensification with the integrase inhibitor raltegravir decreases plasma HIV-1 RNA levels in patients receiving suppressive antiretroviral therapy. METHODS Subjects (n = 10) with long-term HIV-1 suppression receiving combination antiretroviral regimens had their regimens intensified for 4 weeks with raltegravir. Plasma HIV-1 RNA level was determined before, during, and after the 4-week intensification period, using a sensitive assay (limit of detection, 0.2 copies of HIV-1 RNA/mL of plasma). A 4-week intensification course was chosen to investigate potential HIV-1 replication in cells with relatively short (approximately 1-14-day) half-lives. RESULTS There was no evidence in any subject of a decline in HIV-1 RNA level during the period of raltegravir intensification or of rebound after discontinuation. Median levels of HIV-1 RNA before (0.17 log10 copies/mL), during (0.04 log10 copies/mL), and after (0.04 log10 copies/mL) raltegravir intensification were not significantly different (P > .1 for all comparisons in parametric analyses). High-performance liquid chromatography and mass spectroscopy experiments confirmed that therapeutic levels of raltegravir were achieved in plasma during intensification. CONCLUSIONS Intensification of antiretroviral therapy with a potent HIV-1 integrase inhibitor did not decrease persistent viremia in subjects receiving suppressive regimens, indicating that rapidly cycling cells infected with HIV-1 were not present. Eradication of HIV-1 from infected persons will require new therapeutic approaches. TRIAL REGISTRATION ClinicalTrials.gov identifier: NCT00618371.

Pharmacokinetic and Pharmacodynamic Assessment of Oral Valganciclovir in the Treatment of Symptomatic Congenital Cytomegalovirus Disease

BACKGROUND Intravenous ganciclovir administered for 6 weeks improves hearing outcomes in infants with symptomatic congenital cytomegalovirus (CMV) disease involving the central nervous system. METHODS Twenty-four subjects received antiviral therapy for 6 weeks. Serial pharmacokinetic assessments were performed after administration of valganciclovir oral solution and of intravenous ganciclovir. RESULTS On the basis of a previous pharmacokinetic study of the use of intravenous ganciclovir in this population, a target AUC12 (area under the concentration-time curve over a 12-h period) of 27 mg x h/L was defined. The median dose of oral valganciclovir administered in the present trial was 16 mg/kg, which produced a geometric mean AUC12 of 27.4 mg x h/L. The bioavailability of valganciclovir was 41.1%. Of the 18 subjects who had detectable CMV in whole blood at baseline or during therapy, 11 had <4 log viral DNA copies/mL at baseline, and 7 had > or =4 log viral DNA copies/mL at baseline; subjects who started the study with the higher viral burden experienced greater decreases in viral load but did not clear virus during the 42-day course of therapy. Neutropenia of grade 3 or 4 developed in 38% of subjects. CONCLUSIONS In neonates with symptomatic congenital CMV disease, valganciclovir oral solution provides plasma concentrations of ganciclovir comparable to those achieved with administration of intravenous ganciclovir. The results of the present study cannot be extrapolated to extemporaneously compounded liquid formulations of valganciclovir.

Preexisting Resistance to Nonnucleoside Reverse-Transcriptase Inhibitors Predicts Virologic Failure of an Efavirenz-Based Regimen in Treatment-Naive HIV-1–Infected Subjects

A case-cohort study was used to determine the effect of baseline nonnucleoside reverse-transcriptase inhibitor (NNRTI) resistance, as assessed by viral genotyping, on the response to efavirenz-containing regimens in AIDS Clinical Trials Group A5095. The sample included a random cohort of efavirenz-treated subjects plus unselected subjects who experienced virologic failure. Of 220 subjects in the random cohort, 57 (26%) had virologic failure. The prevalence of baseline NNRTI resistance was 5%. The risk of virologic failure for subjects with baseline NNRTI resistance was higher than that for subjects without such resistance (hazard ratio 2.27 [95% confidence interval], 1.15-4.49; P = .018). These results support resistance testing before starting antiretroviral therapy.

Effectiveness of a city-wide program to prevent mother-to-child HIV transmission in Lusaka, Zambia

Objective:To determine the population effectiveness of a city-wide perinatal HIV prevention program. Design:An anonymous surveillance of newborn cord blood for HIV serology and nevirapine (NVP). Methods:All 10 public-sector delivery centers in Lusaka, Zambia participated. All mother–infant pairs delivering during the 12-week surveillance period at the participating centers and who received antenatal care at a public-sector facility in Lusaka were included in the study. The main outcome measure was population NVP coverage, defined as the proportion of HIV-infected women and HIV-exposed infants in the population that ingested NVP. Results:Of 8787 women in the surveillance population, 7204 (82%) had been offered antenatal HIV testing, of which 5149 (71%) had accepted, and of which 5129 (99%) had received a result. Overall, 2257 of 8787 (26%) were cord seropositive. Of the 1246 (55%) cord blood seropositive women who received an antenatal HIV test result, 1112 (89%) received a positive result; the other 134 comprise seroconverters and clerical errors. Only 751 of 1112 (68%) women who received a positive antenatal test result and a NVP tablet for ingestion at labor onset had NVP detected in the cord blood (i.e., maternal non-adherence rate was 32%). A total of 675 infants born to 751 adherent mothers (90%) received NVP before discharge. Thus, only 675 of 2257 (30%) seropositive mother–infant pairs in the surveillance population received both a maternal and infant dose of NVP. Conclusions:Successful perinatal HIV prevention requires each mother–infant pair to negotiate a cascade of events that begins with offering HIV testing and continues through adherence to the prescribed regimen. This novel surveillance demonstrates that failures occur at each step, resulting in reduced coverage and diminished program effectiveness.

Effect of CYP2B6, ABCB1, and CYP3A5 polymorphisms on efavirenz pharmacokinetics and treatment response: an AIDS Clinical Trials Group Study.

In AIDS Clinical Trials Group protocols 384, A5095, and A5097s, we characterized relationships between 22 polymorphisms in CYP2B6, ABCB1, and CYP3A5; plasma efavirenz exposure; and/or treatment responses. A stepwise logistic regression procedure selected polymorphisms associated with reduced drug clearance adjusted for body mass index and the composite CYP2B6 516/983 genotype. Relationships between selected polymorphisms and treatment responses were characterized by competing risk methodology. Association analyses involved 821 individuals (317 for pharmacokinetics and 643 for treatment response). Models that included CYP2B6 516/983 genotype best predicted pharmacokinetics. Slow-metabolizer genotypes were associated with increased central nervous system events among white participants and decreased virologic failure among black participants.

Efficacy of a nucleoside-sparing regimen of darunavir/ritonavir plus raltegravir in treatment-naive HIV-1-infected patients (ACTG A5262).

Objective:To explore darunavir/ritonavir (DRV/r) plus raltegravir (RAL) combination therapy in antiretroviral-naive patients. Design:Phase IIb, single-arm, open-label, multicenter study. Methods:One hundred and twelve antiretroviral-naive, HIV-1-infected patients received DRV/r 800/100 mg once daily and RAL 400 mg twice daily. Primary endpoint was virologic failure by week 24. Virologic failure was defined as confirmed viral load of 1000 copies/ml or more at week 12, or an increase of more than 0.5 log10 copies/ml in viral load from week 4 to 12, or a confirmed viral load of more than 50 copies/ml at or after week 24. Protease and integrase genes were sequenced in patients experiencing virologic failure. Results:Virologic failure rate was 16% [95% confidence interval (CI) 10–24] by week 24 and 26% (95% CI 19–36) by week 48 in an intent-to-treat analysis. Viral load at virologic failure was 51–200 copies/ml in 17/28 failures. Adjusting for age and sex, virologic failure was associated with baseline viral load of more than 100 000 copies/ml [hazard ratio 3.76, 95% CI (1.52–9.31), P = 0.004] and lower CD4 cell count [0.77 per 100 cells/&mgr;l increase (95% CI 0.61–0.98), P = 0.037]. When trough RAL concentrations were included as a time-varying covariate in the analysis, virologic failure remained associated with baseline viral load more than 100 000 copies/ml [hazard ratio = 4.67 (95% CI 1.93–11.25), P < 0.001], whereas RAL level below detection limit in plasma at one or more previous visits was associated with increased hazard [hazard ratio = 3.42 (95% CI 1.41–8.26), P = 0.006]. All five participants with integrase mutations during virologic failure had baseline viral load more than 100 000 copies/ml. Conclusion:DRV/r plus RAL was effective and well tolerated in most patients, but virologic failure and integrase resistance were common, particularly in patients with baseline viral load more than 100 000 copies/ml.