Background: Tenofovir alafenamide (TAF) is a nucleoside reverse transcriptase inhibitor with improved renal and bone safety compared with tenofovir disoproxil fumarate (TDF). Emtricitabine (F)/TAF is approved in Europe and the US for use with boosted protease inhibitors in adults and older children, and is being evaluated with cobicistat-boosted atazanavir (ATV/co) or darunavir (DRV/co) in younger children in an ongoing open-label Phase 2/3 trial (NCT02016924). Here, we report efficacy and safety outcomes through 48 weeks in children with HIV aged 2-<12 years and weighing 14-<40 kg. Material and Methods: Participants aged 6-<12 years, weighing 25-<40 kg, received 200/25 mg F/TAF + ATV/co or DRV/co (Cohort 2). Participants aged ≥2 years and weighing 14-<25 kg received 120/15 mg F/TAF + ATV/co or DRV/co (Cohort 3). Baseline characteristics, virologic suppression, changes in clinical parameters, and changes in bone mineral density (BMD; assessed by dual-energy X-ray absorptiometry) are reported. Results: Twenty-three participants were enrolled into Cohort 2 and 26 participants were enrolled into Cohort 3. In Cohort 2, 61% of participants were female and 91% were Black; at baseline, median (range) age was 10 (8-12) years, 96% of participants had HIV-1 RNA <50 copies/mL, and median (Q1, Q3) CD4 cell count and percentage were 876 (671, 1063) cells/µL and 36.2% (31.1, 41.0), respectively. In Cohort 3, 54% of participants were female and 92% were Black; at baseline, median (range) age was 6 (3-10) years, 92% of participants had HIV-1 RNA <50 copies/mL, and median (Q1, Q3) CD4 cell count and percentage were 940 (705, 1259) cells/µL and 34.8% (29.5, 40.8), respectively. At Week 48, 100% (23/23) of participants in Cohort 2 and 96% (25/26) in Cohort 3 had HIV-1 RNA <50 copies/mL; CD4 cell counts remained stable, with a median (Q1, Q3) CD4 cell count and percentage of 785 (630, 1133) cells/µL and 38.7% (32.5, 42.1), respectively for Cohort 2, and 769 (618, 1064) cells/µL and 37.4% (32.4, 39.6), respectively, for Cohort 3. Two participants, both in Cohort 3, each experienced two Grade 3/4 study drug–related treatment-emergent adverse events (TEAEs). All four TEAEs were of elevated bilirubin/hyperbilirubinemia (Grade 3) and were considered related to ATV; one was classified as a serious TEAE. From evaluable data, no clinically significant changes were observed from baseline to Week 48 in renal parameters (estimated glomerular filtration rate), height and weight parameters (height, weight, and BMI Z-scores), and BMD (spine, and total body less head). Conclusions: Over 48 weeks of treatment, F/TAF + ATV/co or DRV/co in children aged 2-<12 years and weighing 14-<40 kg maintained high rates of virologic suppression, with an acceptable safety profile. There were no renal, bone, or weight gain/loss concerns, supporting further evaluation of these drug combinations in pediatric populations.

17th International Workshop on Pediatrics & HIV 2025

11 July 2025

11 July 2025

12 July 2025

12 July 2025