The Food and Drug Administration (FDA) has expanded the indication of Tybost (cobicistat; Gilead), CYP3A inhibitor, for coadministration with darunavir to include pediatric patients with HIV-1 infection weighing at least 40kg. Previously, Tybost was not recommended in combination with darunavir in pediatric patients.

The approval was supported by data from the phase 2/3 multicenter, open-label trial that evaluated the pharmacokinetics, safety, and efficacy of Tybost coadministered with atazanavir or darunavir in HIV-1 infected antiretroviral treatment-experienced (for ≥3 months), virologically suppressed, pediatric patients aged 3 months to <18 years with a baseline estimated CrCl ≥90mL/min/1.73m2. Patients were switched onto Tybost 150mg once daily from ritonavir and continued with either atazanavir (N=14) or darunavir (N=7) once daily with 2 nucleotide reverse transcriptase inhibitors (NRTIs).

Findings from the study showed 86% of patients (N=6/7) treated with Tybost plus darunavir remained suppressed (HIV-1 RNA <50 copies/mL), and 1 patient had missing data at Week 48. The median change from baseline in CD4+ cell count and CD4+% at Week 48 was -342 cells/mm3 (range -1389 to 219 cells/mm3) and -6% (range -12% to 5%), respectively. By Week 48, CD4+ cell counts were greater than 800 cells/mm3 in all 6 patients. The safety profile of Tybost in pediatric patients was similar to that observed in adults.

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Tybost is already indicated to increase systemic exposure of atazanavir or darunavir (once-daily dosing) in combination with other antiretroviral agents in the treatment of HIV-1 infection in adults; or, to increase systemic exposure of atazanavir in combination with other antiretroviral agents in the treatment of HIV-1 infection in pediatric patients weighing at least 35kg with HIV-1 infection. 


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For more information visit fda.gov.