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New WashU Medicine research supports consideration of HCV treatment during lactation 

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Researchers at WashU Medicine have published the first study to measure glecaprevir/pibrentasvir (GLE/PIB) levels in breastmilk among postpartum women treated for chronic hepatitis C. The findings suggest infant exposure through breastfeeding is minimal, providing reassuring evidence to support consideration of GLE/PIB during lactation. 

Image title: Glecaprevir and Pibrentasvir Concentrations in Plasma and Breastmilk. Table text: Glecaprevir: Plasma Concentration, ng/mL 817 (722, 1724); Breastmilk Concentration, ng/mL 5.17 (2, 7.28); Milk/Plasma Concentration Ratio 0.0063 (0.0028, 0.0042); Estimated Infant Daily Dose From Breastmilk, mg/kg/d 0.0009 (0.0003, 0.0011); % Relative Infant Dose 0.0210% (0.0070%, 0.0255%). Pibrentasvir: Plasma Concentration, ng/mL 166 (136.5, 234); Breastmilk Concentration, ng/mL 7.035 (2.11, 41.7); Milk/Plasma Concentration Ratio 0.0423 (0.0155, 0.1782); Estimated Infant Daily Dose From Breastmilk, mg/kg/d 0.0011 (0.0003, 0.0014); % Relative Infant Dose 0.0641% (0.0185%, 0.3649%). Table note: Concentrations, ratios, estimated dose, and relative infant dose are shown as mean (minimum, maximum). Total adult daily dose of glecaprevir is 300 mg normalized to 70 kg adult. Total adult daily dose of pibrentasvir is 120 mg normalized to 70 kg adult. Published in Clinical Infectious Diseases September 25, 2026. Key takeaway: This is the first report measuring Glecaprevir and Pibrentasvir concentrations in breastmilk. Both drugs were detected at low levels, and infant exposure through breastmilk appears minimal. These findings are reassuring for infant safety and support consideration of Glecaprevir and Pibrentasvir during breastfeeding.

This study helps address an important gap in postpartum HCV care, especially given low rates of maternal linkage to treatment after delivery. The work is a collaboration among the Department of Medicine Division of Infectious Diseases, the Center for Women’s Infectious Disease Research, and the Department of Obstetrics & Gynecology Division of Maternal-Fetal Medicine & Ultrasound, with lead authors Laura Marks, MD, PhD, Assistant Professor of Medicine, Division of Infectious Diseases, and Madeline McCrary, Assistant Professor of Medicine, Division of Infectious Diseases. It was published September 25, 2026, in Clinical Infectious Diseases. 

McCrary LM, Fujiwara H, Robinson J, Kelly J, Curtis MR, Durkin MJ, Habrock-Bach T, Henderson JP, Marks LR. Glecaprevir/Pibrentasvir Concentrations in the Breastmilk of Lactating Women. Clin Infect Dis. 2026 Sep 25:ciag503. doi: 10.1093/cid/ciag503. Epub ahead of print. PMID: 42788470.