title: Virologic and immunologic responses in treatment-naive patients to ritonavir-boosted atazanavir or efavirenz with a common backbone.
abstract: BACKGROUND
  Atazanavir boosted with ritonavir (ATV/r) and efavirenz (EFV) are both recommended as first-line therapies for HIV-infected patients. We compared the 2 therapies for virologic efficacy and immune recovery.
  
  
  METHODS
  We included all treatment-naïve patients in the Swiss HIV Cohort Study starting therapy after May 2003 with either ATV/r or EFV and a backbone of tenofovir and either emtricitabine or lamivudine. We used Cox models to assess time to virologic failure and repeated measures models to assess the change in CD4 cell counts over time. All models were fit as marginal structural models using both point of treatment and censoring weights. Intent-to-treat and various as-treated analyses were carried out: In the latter, patients were censored at their last recorded measurement if they changed therapy or if they were no longer adherent to therapy.
  
  
  RESULTS
  Patients starting EFV (n = 1,097) and ATV/r (n = 384) were followed for a median of 35 and 37 months, respectively. During follow-up, 51% patients on EFV and 33% patients on ATV/r remained adherent and made no change to their first-line therapy. Although intent-to-treat analyses suggest virologic failure was more likely with ATV/r, there was no evidence for this disadvantage in patients who adhered to first-line therapy. Patients starting ATV/r had a greater increase in CD4 cell count during the first year of therapy, but this advantage disappeared after one year.
  
  
  CONCLUSIONS
  In this observational study, there was no good evidence of any intrinsic advantage for one therapy over the other, consistent with earlier clinical trials. Differences between therapies may arise in a clinical setting because of differences in adherence to therapy.
authors.affiliation: Basel Institute for Clinical Epidemiology and Biostatistics, University Hospital Basel, Basel, Switzerland.
authors.forename: Qing
authors.initials: Q
authors.lastname: Wang
authors.affiliation: Basel Institute for Clinical Epidemiology and Biostatistics, University Hospital Basel, Basel, Switzerland.
authors.forename: Jim
authors.initials: J
authors.lastname: Young
authors.affiliation: Division of Infectious Diseases, Regional Hospital of Lugano, Lugano, Switzerland.
authors.forename: Enos
authors.initials: E
authors.lastname: Bernasconi
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, Cantonal Hospital St. Gallen, St. Gallen, Switzerland.
authors.forename: Pietro
authors.initials: P
authors.lastname: Vernazza
authors.affiliation: Division of Infectious Diseases, University Hospital Geneva, Geneva, Switzerland.
authors.forename: Alexandra
authors.initials: A
authors.lastname: Calmy
authors.affiliation: Division of Infectious Diseases, University Hospital Lausanne, Lausanne, Switzerland.
authors.forename: Matthias
authors.initials: M
authors.lastname: Cavassini
authors.affiliation: Department of Infectious Diseases, Bern University Hospital and University of Bern, Bern, Switzerland.
authors.forename: Hansjakob
authors.initials: H
authors.lastname: Furrer
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital and University of Zürich, Zürich, Switzerland.
authors.forename: Jan
authors.initials: J
authors.lastname: Fehr
authors.affiliation: Basel Institute for Clinical Epidemiology and Biostatistics, University Hospital Basel, Basel, Switzerland.
authors.forename: Heiner C
authors.initials: HC
authors.lastname: Bucher
authors.affiliation: Division of Infectious Diseases and Hospital Epidemiology, University Hospital Basel, Basel, Switzerland.
authors.forename: Manuel
authors.initials: M
authors.lastname: Battegay
mesh_terms: D000328:Adult; D000480:Alkynes; D000069446:Atazanavir Sulfate; D048588:Benzoxazines / Q000008:administration & dosage*; D018791:CD4 Lymphocyte Count; D015331:Cohort Studies; D003521:Cyclopropanes; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000188:drug therapy* / Q000276:immunology / Q000821:virology; D006801:Humans; D008297:Male; D009842:Oligopeptides / Q000008:administration & dosage*; D011446:Prospective Studies; D011725:Pyridines / Q000008:administration & dosage*; D019438:Ritonavir / Q000008:administration & dosage*
chemical_list: D000480:Alkynes; D048588:Benzoxazines; D003521:Cyclopropanes; D009842:Oligopeptides; D011725:Pyridines; D000069446:Atazanavir Sulfate; C098320:efavirenz; D019438:Ritonavir
keywords: CD4; antiretroviral therapy; epidemiology; protease inhibitors; reverse transcriptase inhibitors; viral load