Switching to unboosted atazanavir reduces bilirubin and triglycerides without compromising treatmentefficacy in UGT1A1*28 polymorphism carriers

Hyperbilirubinaemia is a frequent complication of atazanavir-containing antiretroviral therapy and its severity is related to UDP-glucuronosyl transferase (UGT) 1A128 polymorphism. The aim of this study was to evaluate the safety and outcome of unboosted atazanavir-containing regimens based on the genetic constitution. Fifty-one HIV-1-infected patients on boosted atazanavir were prospectively enrolled in the study. Twenty-five patients with a UGT1A128 allele switched to 400 mg of unboosted atazanavir. At baseline, UGT1A1 heterozygous and homozygous patients had significantly higher bilirubin levels than wild-type (P0.012 and P0.001, respectively). After ritonavir removal, a reduction was observed in total bilirubin (from 4.09 to 1.82 mg/dL; P0.001), -glutamyl transpeptidase (P0.015), triglycerides (P0.03) and total cholesterol (P0.05). No significant changes in CD4 T cell count and no increases in viral load were observed 12 months after unboosting. Plasma drug monitoring after ritonavir removal revealed the presence of therapeutic atazanavir concentrations in all patients except one with poor therapy adherence. UGT1A128 is significantly related to hyperbilirubinaemia in HIV-1 patients receiving atazanavir. Genotyping before the initiation of antiretroviral therapy can reduce the emergence of severe hyperbilirubinaemia. Unboosted atazanavir-containing therapy is safe and efficacious in patients with an undetectable viral load with a UGT1A128 polymorphism, allowing the use of atazanavir in patients otherwise likely unable to receive it.