Edward M. Gardner

The Spectrum of Engagement in HIV Care and its Relevance to Test-and-Treat Strategies for Prevention of HIV Infection

For individuals with human immunodeficiency virus (HIV) infection to fully benefit from potent combination antiretroviral therapy, they need to know that they are HIV infected, be engaged in regular HIV care, and receive and adhere to effective antiretroviral therapy. Test-and-treat strategies for HIV prevention posit that expanded testing and earlier treatment of HIV infection could markedly decrease ongoing HIV transmission, stemming the HIV epidemic. However, poor engagement in care for HIV-infected individuals will substantially limit the effectiveness of test-and-treat strategies. We review the spectrum of engagement in care for HIV-infected individuals in the United States and apply this information to help understand the magnitude of the challenges that poor engagement in care will pose to test-and-treat strategies for HIV prevention.

Pharmacological considerations for tenofovir and emtricitabine to prevent HIV infection

The use of antiretroviral medications in HIV-negative individuals as pre-exposure prophylaxis (PrEP) is a promising approach to prevent HIV infection. Tenofovir disoproxil fumarate (TDF) and emtricitabine exhibit desirable properties for PrEP including: favourable pharmacokinetics that support infrequent dosing; few major drug-drug or drug-food interactions; an excellent clinical safety record; and pre-clinical evidence for efficacy. Several large, randomized, controlled clinical trials are evaluating the safety and efficacy of TDF and emtricitabine for this new indication. A thorough understanding of variability in drug response will help determine future investigations in the field and/or implementation into clinical care. Because tenofovir and emtricitabine are nucleos(t)ide analogues, the HIV prevention and toxicity effects depend on the triphosphate analogue formed intracellularly. This review identifies important cellular pharmacology considerations for tenofovir and emtricitabine, which include drug penetration into relevant tissues and cell types, race/ethnicity/pharmacogenetics, gender, cellular activation state and appropriate episodic or alternative dosing strategies based on pharmacokinetic principles. The current state of knowledge in these areas is summarized and the future utility of intracellular pharmacokinetics/pharmacodynamics for the PrEP field is discussed.

Antiretroviral medication adherence and the development of class-specific antiretroviral resistance.

Objective:To assess the association between antiretroviral adherence and the development of class-specific antiretroviral medication resistance. Design and methods:Literature and conference abstract review of studies assessing the association between adherence to antiretroviral therapy and the development of antiretroviral medication resistance. Results:Factors that determine class-specific adherence–resistance relationships include antiretroviral regimen potency, viral fitness or, more specifically, the interplay between the fold-change in resistance and fold-change in fitness caused by drug resistance mutations, and the genetic barrier to antiretroviral resistance. During multidrug therapy, differential drug exposure increases the likelihood of developing resistance. In addition, antiretroviral medications with higher potency and higher genetic barriers to resistance decrease the incidence of resistance for companion antiretroviral medications at all adherence levels. Conclusion:Knowledge of class-specific adherence–resistance relationships may help clinicians and patients tailor therapy to match individual patterns of adherence in order to minimize the development of resistance at failure. In addition, this information may guide the selection of optimal drug combinations and regimen sequences to improve the durability of antiretroviral therapy.

Differential adherence to combination antiretroviral therapy is associated with virological failure with resistance

Objectives: To investigate the occurrence of differential adherence to components of combination antiretroviral therapy and assess its predictors and association with virological failure and antiretroviral medication resistance. Design: A secondary analysis of prospective clinical trial data. Methods: The Flexible Initial Retrovirus Suppressive Therapies study (Community Programs for Clinical Research on AIDS 058) was a randomized trial comparing non-nucleoside reverse transcriptase inhibitor (NNRTI) versus protease inhibitor (PI) versus NNRTI plus PI-based (three-class) antiretroviral therapy in treatment-naive HIV-1-infected individuals. Adherence was assessed at months 1 and 4, and then every 4 months. Differential adherence, defined as any difference in self-reported level of adherence to individual antiretroviral medications at the same timepoint, was evaluated as a binary time-updated variable in multivariate Cox regression analyses of time to initial virological failure (HIV-RNA > 1000 copies/ml) and initial virological failure with genotypic antiretroviral resistance. Results: Differential adherence was reported at least once by 403 of 1379 participants (29%), over 60 months median follow-up. Differential adherence was more commonly reported by participants randomly assigned to the three-class strategy (35%) than the NNRTI (28%) or PI (25%) strategies (P = 0.005), but was not associated with demographic or baseline disease-specific factors. Of those reporting differential adherence, 146 (36%) reported it before initial virological failure. These participants had an increased risk of initial virological failure and initial virological failure with antiretroviral resistance compared with participants without differential adherence before initial virological failure. Conclusion: Differential adherence was commonly reported and was associated with an increased risk of initial virological failure and initial virological failure with antiretroviral resistance.

Risk-based human immunodeficiency virus (HIV) testing fails to detect the majority of HIV-infected persons in medical care Settings.

Objectives: To evaluate opportunities for earlier human immunodeficiency virus (HIV) diagnosis within a comprehensive public health care system. Study Design: Retrospective review of newly diagnosed HIV-infected patients between September 2001 and December 2003. Results: One hundred twenty of 348 (34%) newly diagnosed HIV-infected patients had medical care within our system in the 3 years before diagnosis. One hundred five of 120 (88%) patients had at least 1 prior encounter in the emergency department or urgent care center, whereas just 12 (10%) HIV diagnoses were made in these 2 sites. Only 33 (28%) patients previously presented with an HIV clinical indicator condition or sexually transmitted infection. Conclusions: Although one-third of newly diagnosed HIV-infected patients had clinical visits in the 3 years before diagnosis, few presented with clinical conditions typically associated with HIV infection. Targeted testing based on clinical presentations is not likely to result in substantially earlier HIV diagnosis. Routine screening in high prevalence settings could be more effective.

Antiretroviral medication adherence and class-specific resistance in a large prospective clinical trial

Objective:To assess the association between adherence to antiretroviral therapy and the presence of class-specific antiretroviral medication resistance. Design:Secondary analysis of prospective clinical trial data. Methods:Participants randomized to the protease inhibitor or nonnucleoside reverse transcriptase inhibitor (NNRTI) strategies of the Community Programs for Clinical Research on AIDS (CPCRA) Flexible Initial Retrovirus Suppressive Therapies (FIRST) Study were included. Adherence was measured by 7-day self-report. Virological failure was defined as an HIV-RNA more than 1000 at or after 4 months. The association between cumulative adherence and the development of class-specific genotypic resistance was assessed by Cox regression analysis. Results:Included were 457 and 446 antiretroviral-naive participants on the protease inhibitor and NNRTI strategies, respectively. The median time to initial virological failure in the protease inhibitor strategy was 1.2 years; 135 (30%) individuals failed with resistance. The median time to initial virological failure in the NNRTI strategy was 3.0 years; 127 (28%) failed with resistance. No association was found between cumulative adherence and protease inhibitor resistance [hazard ratio 1.1, 95% confidence interval (CI) 0.9–1.4 per 10% lower adherence]. However, lower cumulative adherence was associated with an increased risk of NNRTI resistance at initial virological failure (hazard ratio 1.2, 95% CI 1.1–1.3 per 10% lower adherence). In both strategies, lower cumulative adherence was associated with an increased risk of nucleoside reverse transcriptase inhibitor (NRTI) resistance at initial virological failure. Conclusion:Adherence–resistance relationships are class-specific. For NRTIs and NNRTIs, initial virological failure with resistance is more likely at lower levels of cumulative adherence.

A randomized comparison of two instruments for measuring self-reported antiretroviral adherence

Abstract A randomised trial compared two instruments for assessing self-reported adherence to antiretroviral medications: (1) a day-by-day recall instrument that elicited the number of missed doses in each of the prior three days (3-day instrument; n=64) and (2) a general recall instrument that elicited an estimate of proportion of pills taken during the prior seven days (7-day instrument; n=70). Adherence was measured at study visits over 12 months among participants in a clinical trial assessing treatment strategies for individuals with virologic failure and multidrug-resistant HIV. Participants had a median (interquartile range) of 133 (41–264) CD4 cells/ml3 and a median of 10 major HIV resistance mutations at baseline. Mean adherence levels were 90–98% throughout the study. There was a greater trend in the likelihood of 100% adherence when measured by the 3-day versus the 7-day instrument (odds ratio (OR)=1.45; p=0.06). The likelihood of consistent 100% adherence measured by either instrument decreased over time (p<0.001). Participants reporting 100% adherence at more than half of study visits had better virologic and immunologic outcomes at month-12 compared to those reporting 100% adherence at half or fewer visits (HIV RNA decline of 0.96 versus 0.51 log, respectively, p=0.02; and CD4 cell increase of 51.0 versus 17.8 cells, p=0.04). This study demonstrated the utility of the general 7-day recall adherence self-report instrument as well as the 3-day day-by-day recall adherence self-report instrument for measuring antiretroviral adherence. Self-reported adherence was significantly associated with virologic and immunologic outcomes in this population with advanced drug-resistant HIV disease.

Atazanavir pharmacokinetics in genetically determined CYP3A5 expressors versus non-expressors

OBJECTIVES The objective of this study was to compare atazanavir pharmacokinetics in genetically determined CYP3A5 expressors versus non-expressors. METHODS HIV-negative adult volunteers were pre-screened for CYP3A5 *3, *6 and *7 polymorphisms and enrollment was balanced for CYP3A5 expressor status, gender and race (African-American versus non-African-American). Participants received atazanavir 400 mg daily for 7 days followed by atazanavir/ritonavir 300 mg/100 mg daily for 7 days with pharmacokinetic studies on days 7 and 14. Other measures collected were bilirubin, UGT1A1 *28, and ABCB1 1236C > T, 2677G > T/A and 3435C > T genotypes. Data analyses utilized least squares regression. RESULTS Fifteen CYP3A5 expressors and 16 non-expressors participated. The day 7 atazanavir oral clearance (CL/F) was 1.39-fold faster (0.25 versus 0.18 L/h/kg; P = 0.045) and the C(min) was half (87 versus 171 ng/mL; P = 0.044) in CYP3A5 expressors versus non-expressors. Non-African-American CYP3A5 expressor males had 2.1-fold faster CL/F (P = 0.003) and <20% the C(min) (P = 0.0001) compared with non-African-American non-expressor males. No overall CYP3A5 expressor effects were observed during the ritonavir phase. One or two copies of wild-type ABCB1 haplotype (1236C/2677G/3435C) was predictive of slower atazanavir and ritonavir CL/F compared with zero copies (P < 0.06). Indirect bilirubin increased 1.6- to 2.8-fold more in subjects with UGT1A1 *28/*28 versus *1/*28 or *1/*1. CONCLUSIONS CYP3A5 expressors had faster atazanavir CL/F and lower C(min) than non-expressors. The effect was most pronounced in non-African-American men. Ritonavir lessened CYP3A5 expressor effects. The wild-type ABCB1 CGC haplotype was associated with slower CL/F and the UGT1A1 *28 genotype was associated with increased bilirubin. Thus, CYP3A5, ABCB1 and UGT1A1 polymorphisms are associated with atazanavir pharmacokinetics and pharmacodynamics in vivo.

Selective drug taking during combination antiretroviral therapy in an unselected clinic population.

Objectives:Multidrug therapy is necessary to achieve sustained viral suppression. Discordant adherence to individual components of a multidrug regimen may lead to adverse outcomes. Methods:Antiretroviral-naive patients initiating therapy from 1997 through 2002 were included. Adherence for each antiretroviral was determined using pharmacy refill data. Selective drug taking was defined as ≥5% difference in adherence between 2 components of an antiretroviral regimen lasting at least 60 days. Results:A total of 322 of 415 patients (78%) met inclusion criteria. Selective drug taking occurred in 47 of 322 patients (15%) and on 51 of 438 regimens (12%). Factors associated with selective drug taking were lower baseline CD4 lymphocyte count (adjusted odds ratio [AOR]: 1.3, 95% CI: 1.1 to 1.6 per 100 cell/μL decrease); 3 times daily dosing schedule (AOR: 4.1, 95% CI: 1.1 to 15.5); and the presence of significant adverse drug events (AOR: 2.9, 95% CI: 1.3 to 6.4). Regimens containing a fixed-dose combination dosage form were less likely to have selective drug taking (AOR: 0.5, 95% CI: 0.2 to 0.99). Outcomes independently associated with selective drug taking included earlier progression to a new AIDS-defining illness or death (hazard ratio: 2.3, 95% CI: 1.2 to 4.5). Conclusions:Selective drug taking was relatively common among patients taking combination antiretroviral therapy. The factor most closely associated with selective drug taking was the presence of an adverse drug event. Clinical outcomes appeared worse in patients with selective drug taking.

The association of adherence to antiretroviral therapy with healthcare utilization and costs for medical care

BackgroundThe association between antiretroviral adherence, healthcare utilization and medical costs has not been well studied.ObjectiveTo examine the relationship of adherence to antiretroviral medications to healthcare utilization and healthcare costs.MethodsA retrospective cohort study was conducted using data from 325 previously antiretroviral medication-naive HIV-infected individuals initiating first antiretroviral therapy from 1997 through 2003. The setting was an inner-city safety net hospital and HIV clinic in the US. Adherence was assessed using pharmacy refill data. The average wholesale price was used for prescription costs. Healthcare utilization data and medical costs were obtained from the hospital billing database, and differences according to quartile of adherence were compared using analysis of variance (ANOVA). Multivariate logistic regression was used to assess predictors of higher annual medical costs. Sensitivity analyses were used to examine alternative anti-retroviral pricing schemes. The perspective was that of the healthcare provider, and costs were in year 2005 values.ResultsIn 325 patients followed for a mean (± SD) 3.2 (1.9) years, better adherence was associated with lower healthcare utilization but higher total medical costs. Annual non-antiretroviral medical costs were