Adrie Bekker1, Edmund V Capparelli2, Avy Violari3, Mark F Cotton4, Mae Cababasay5, Jiajia Wang5, Ruth Mathiba3, Lubbe Wiesner6, Andrew Wiznia7, Pearl Samson8, Renee Browning9, Jack Moye10, Firdose L Nakwa11, Eric Decloedt12, Helena Rabie4, Mark Mirochnick13, Tim R Cressey14. 1. Family Centre for Research with Ubuntu, Department of Paediatrics and Child Health, Stellenbosch University, Cape Town, South Africa. Electronic address: adrie@sun.ac.za. 2. University of California San Diego, San Diego, CA, USA. 3. Perinatal HIV Research Unit, University of the Witwatersrand, Johannesburg, South Africa. 4. Family Centre for Research with Ubuntu, Department of Paediatrics and Child Health, Stellenbosch University, Cape Town, South Africa. 5. Center for Biostatistics in AIDS Research, Harvard T H Chan School of Public Heath, Boston, MA, USA. 6. Division of Clinical Pharmacology, University of Cape Town, Cape Town, South Africa. 7. Jacobi Medical Center, Bronx, NY, USA. 8. Frontier Science Foundation, Amherst, NY, USA. 9. Division of AIDS, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD, USA. 10. Division of Extramural Research, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD, USA. 11. Department of Paediatrics, University of the Witwatersrand, Johannesburg, South Africa. 12. Division of Clinical Pharmacology, Department of Medicine, Stellenbosch University, Cape Town, South Africa. 13. Boston University School of Medicine, Boston, MA, USA. 14. AMS/PHPT Research Collaboration, Department of Medical Technology, Faculty of Associated Medical Sciences, Chiang Mai University, Chiang Mai, Thailand; MIVEGEC, University of Montpellier, CNRS, IRD, Montpellier, France; Department of Molecular and Clinical Pharmacology, University of Liverpool, Liverpool, UK.
Abstract
BACKGROUND: No evidence-based optimal dosing guidance is available for abacavir liquid formulation use from birth. We used abacavir pharmacokinetic data from neonates and infants to determine an exact abacavir dosing strategy (mg/kg) for infants aged 0-3 months and to propose dosing by WHO weight band for neonates. METHODS: Abacavir pharmacokinetic and safety data were pooled from three completed studies (1997-2020): PACTG 321 (USA), the Tygerberg Cohort (South Africa), and IMPAACT P1106 (South Africa). PACTG 321 and the Tygerberg Cohort were performed in neonates exposed to HIV receiving a single dose of abacavir. IMPAACT P1106 included predominantly low birthweight (<2500 g) infants on antiretroviral therapy enrolled when they were younger than 3 months. We developed a population pharmacokinetic model and performed simulations to achieve abacavir exposures (area under the curve for 0-12 h) within the target range of 3·2-25·2 μg·h/mL, previously reported in older children. FINDINGS: 45 infants contributed 308 abacavir concentrations; 21 neonates were younger than 15 days. At first pharmacokinetic assessment, median postnatal age for PACTG 321 was 1 day and median bodyweight was 3·1 kg; for the Tygerberg Cohort it was 10 days and 3·3 kg; and for IMPAACT P1106 it was 73 days and 3·8 kg. Our model predicted a slow abacavir clearance of 2·51 mL/min per kg at birth, which doubled by 4 weeks of age. Therapeutic targets were achieved with exact abacavir doses of 2·0 mg/kg twice daily from 0 weeks to 4 weeks and 4·0 mg/kg twice daily from 4 weeks to 12 weeks. A fixed weight-band dosing strategy of 8 mg (for 2-3 kg), 10 mg (3-4 kg), and 12 mg (4-5 kg) abacavir twice daily achieved target exposures throughout the first 4 weeks of life without the need for dose adjustment due to age or bodyweight changes. No adverse events of grade 3 or higher were related to abacavir. INTERPRETATION: Integration of these dosing strategies into national and international guidelines for the abacavir liquid formulation will expand antiretroviral options from birth and simplify the clinical management of neonates with HIV. FUNDING: National Institute of Allergy and Infectious Diseases, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institute of Mental Health, and the Collaborative Initiative for Paediatric HIV Education and Research Programme.
BACKGROUND: No evidence-based optimal dosing guidance is available for abacavir liquid formulation use from birth. We used abacavir pharmacokinetic data from neonates and infants to determine an exact abacavir dosing strategy (mg/kg) for infants aged 0-3 months and to propose dosing by WHO weight band for neonates. METHODS: Abacavir pharmacokinetic and safety data were pooled from three completed studies (1997-2020): PACTG 321 (USA), the Tygerberg Cohort (South Africa), and IMPAACT P1106 (South Africa). PACTG 321 and the Tygerberg Cohort were performed in neonates exposed to HIV receiving a single dose of abacavir. IMPAACT P1106 included predominantly low birthweight (<2500 g) infants on antiretroviral therapy enrolled when they were younger than 3 months. We developed a population pharmacokinetic model and performed simulations to achieve abacavir exposures (area under the curve for 0-12 h) within the target range of 3·2-25·2 μg·h/mL, previously reported in older children. FINDINGS: 45 infants contributed 308 abacavir concentrations; 21 neonates were younger than 15 days. At first pharmacokinetic assessment, median postnatal age for PACTG 321 was 1 day and median bodyweight was 3·1 kg; for the Tygerberg Cohort it was 10 days and 3·3 kg; and for IMPAACT P1106 it was 73 days and 3·8 kg. Our model predicted a slow abacavir clearance of 2·51 mL/min per kg at birth, which doubled by 4 weeks of age. Therapeutic targets were achieved with exact abacavir doses of 2·0 mg/kg twice daily from 0 weeks to 4 weeks and 4·0 mg/kg twice daily from 4 weeks to 12 weeks. A fixed weight-band dosing strategy of 8 mg (for 2-3 kg), 10 mg (3-4 kg), and 12 mg (4-5 kg) abacavir twice daily achieved target exposures throughout the first 4 weeks of life without the need for dose adjustment due to age or bodyweight changes. No adverse events of grade 3 or higher were related to abacavir. INTERPRETATION: Integration of these dosing strategies into national and international guidelines for the abacavir liquid formulation will expand antiretroviral options from birth and simplify the clinical management of neonates with HIV. FUNDING: National Institute of Allergy and Infectious Diseases, Eunice Kennedy Shriver National Institute of Child Health and Human Development, National Institute of Mental Health, and the Collaborative Initiative for Paediatric HIV Education and Research Programme.
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