title: Comparison of atazanavir/ritonavir and darunavir/ritonavir based antiretroviral therapy for antiretroviral naïve patients.
abstract: Atazanavir/ritonavir and darunavir/ritonavir are common protease inhibitor-based regimens for treating patients with HIV. Studies comparing these drugs in clinical practice are lacking.
  
  
  
  We conducted a retrospective cohort study of antiretroviral naïve participants in the Canadian Observational Cohort (CANOC) collaboration initiating atazanavir/ritonavir- or darunavir/ritonavir-based treatment. We used separate Fine and Gray competing risk regression models to compare times to regimen failure (composite of virologic failure or discontinuation for any reason). Additional endpoints included virologic failure, discontinuation due to virologic failure, discontinuation for other reasons, and virologic suppression.
  
  
  
  We studied 222 patients treated with darunavir/ritonavir and 1791 patients treated with atazanavir/ritonavir. Following multivariable adjustment, there was no difference between darunavir/ritonavir and atazanavir-ritonavir in the risk of regimen failure (adjusted hazard ratio 0.76, 95% CI 0.56 to 1.03) Darunavir/ritonavir-treated patients were at lower risk of virologic failure relative to atazanavir/ritonavir treated patients (aHR 0.50, 95% CI 0.28 to 0.91), findings driven largely by high rates of virologic failure among atazanavir/ritonavir-treated patients in the province of British Columbia. Of 108 discontinuations due to virologic failure, all occurred in patients starting atazanavir/ritonavir. There was no difference between regimens in time to discontinuation for reasons other than virologic failure (aHR 0.93; 95% CI 0.65 to 1.33) or virologic suppression (aHR 0.99, 95% CI 0.82 to 1.21).
  
  
  
  The risk of regimen failure was similar between patients treated with darunavir/ritonavir and atazanavir/ritonavir. Although darunavir/ritonavir was associated with a lower risk of virologic failure relative to atazanavir/ritonavir, this difference varied substantially by Canadian province and likely reflects regional variation in prescribing practices and patient characteristics.
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada. tantoniou@smh.ca.|Department of Family and Community Medicine, St. Michael's Hospital, Toronto, ON, Canada. tantoniou@smh.ca.|University of Toronto, 410 Sherbourne Street, Toronto, ON, ON M4X 1K2, Canada. tantoniou@smh.ca.
authors.forename: Tony
authors.initials: T
authors.lastname: Antoniou
authors.affiliation: Toronto General Research Institute, University Health Network, Toronto, ON, Canada.
authors.forename: Leah
authors.initials: L
authors.lastname: Szadkowski
authors.affiliation: University of Toronto, 410 Sherbourne Street, Toronto, ON, ON M4X 1K2, Canada.|Toronto General Research Institute, University Health Network, Toronto, ON, Canada.
authors.forename: Sharon
authors.initials: S
authors.lastname: Walmsley
authors.affiliation: The Ottawa Hospital Research Institute, University of Ottawa, Ottawa, ON, Canada.
authors.forename: Curtis
authors.initials: C
authors.lastname: Cooper
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada.|Department of Family and Community Medicine, St. Michael's Hospital, Toronto, ON, Canada.|University of Toronto, 410 Sherbourne Street, Toronto, ON, ON M4X 1K2, Canada.
authors.forename: Ann N
authors.initials: AN
authors.lastname: Burchell
authors.affiliation: Keenan Research Centre, Li Ka Shing Knowledge Institute, St. Michael's Hospital, Toronto, ON, Canada.|University of Toronto, 410 Sherbourne Street, Toronto, ON, ON M4X 1K2, Canada.
authors.forename: Ahmed M
authors.initials: AM
authors.lastname: Bayoumi
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, BC, Canada.|University of British Columbia, Vancouver, BC, Canada.
authors.forename: Julio S G
authors.initials: JS
authors.lastname: Montaner
authors.affiliation: University of Toronto, 410 Sherbourne Street, Toronto, ON, ON M4X 1K2, Canada.|Women's College Hospital Research Institute, Toronto, ON, Canada.|Maple Leaf Medical Clinic, Toronto, ON, Canada.
authors.forename: Mona
authors.initials: M
authors.lastname: Loutfy
authors.affiliation: McGill University Health Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: Marina B
authors.initials: MB
authors.lastname: Klein
authors.affiliation: Clinique Médicale l'Actuel, Montreal, Quebec, Canada.
authors.forename: Nima
authors.initials: N
authors.lastname: Machouf
authors.affiliation: McGill University Health Centre, McGill University, Montreal, Quebec, Canada.
authors.forename: Christos
authors.initials: C
authors.lastname: Tsoukas
authors.affiliation: Regina Qu'Appelle Health Region, Regina, SK, Canada.
authors.forename: Alexander
authors.initials: A
authors.lastname: Wong
authors.affiliation: British Columbia Centre for Excellence in HIV/AIDS, St. Paul's Hospital, Vancouver, BC, Canada.|Simon Fraser University, Burnaby, BC, Canada.
authors.forename: Robert S
authors.initials: RS
authors.lastname: Hogg
authors.affiliation: University of Toronto, 410 Sherbourne Street, Toronto, ON, ON M4X 1K2, Canada.|Toronto General Research Institute, University Health Network, Toronto, ON, Canada.
authors.forename: Janet
authors.initials: J
authors.lastname: Raboud
mesh_terms: D000328:Adult; D019380:Anti-HIV Agents / Q000008:administration & dosage / Q000627:therapeutic use*; D000069446:Atazanavir Sulfate / Q000008:administration & dosage / Q000627:therapeutic use*; D001955:British Columbia; D002170:Canada; D015331:Cohort Studies; D000069454:Darunavir / Q000008:administration & dosage / Q000627:therapeutic use*; D004359:Drug Therapy, Combination; D005260:Female; D015658:HIV Infections / Q000188:drug therapy*; D015497:HIV-1; D006801:Humans; D008297:Male; D008875:Middle Aged; D012189:Retrospective Studies; D019438:Ritonavir / Q000008:administration & dosage / Q000627:therapeutic use*
chemical_list: D019380:Anti-HIV Agents; D000069446:Atazanavir Sulfate; D019438:Ritonavir; D000069454:Darunavir
keywords: Antiretroviral therapy; Atazanavir; Darunavir; HIV; Protease inhibitor