175. B-cell Levels in Infants of Lactating Women with Multiple Sclerosis Receiving Ocrelizumab: SOPRANINO Primary Results

Evidence suggests ocrelizumab (OCR) breastmilk transfer is minimal, although little is known on the pharmacodynamics (PD) in breastfed infants. SOPRANINO (NCT04998851) is the first prospective study measuring both PD and pharmacokinetic breastmilk parameters alongside infant humoral response to vaccines, safety, growth and development. Women with multiple sclerosis (MS) who gave birth to one healthy-term infant and decided to start/ resume OCR at 2–24 weeks postpartum while partially or exclusively breastfeeding were enrolled. Key exclusion criteria were potential OCR foetal exposure and anomalies interfering with breastfeeding. Co-primary outcomes were proportion of infants with B-cell levels below the lower limit of normal at 30 days post-infusion and OCR average daily infant dose (ADID) over 60 days post-infusion. Thirteen women with MS and their infants were enrolled (median [range] infant age at maternal infusion [months]: 2.0 [0.5–5.0]). OCR levels in breastmilk were negligible (median ADID: 45.09 µg; median relative infant dose: 0.27%) and OCR was undetectable in infant serum (median [range]: 0.0 µg/ml [0.0–0.0]). All infant B-cell levels were within age-specific normal ranges (figure). Eleven infants (84.6%) had ≥1 adverse event (AE), of which 10 experienced ≥1 infancy infection. Most infant AEs were mild to moderate (Grade 1 or 2), with one severe (Grade 3) bronchiolitis reported that resolved. No serious AEs occurred. Our results show negligible transfer of OCR into breastmilk, undetectable OCR levels in infant serum as well as normal infant B-cell levels and expected infant health, indicating that breastfeeding is compatible with OCR.