The main purpose of this study is to assess the concentrations of nipocalimab (pharmacokinetics [PK]) in the breast milk after administration of a single dose of nipocalimab into the vein, in healthy lactating women.

Inclusion criteria:

• Healthy on the basis of physical examination, medical history, vital signs, clinical laboratory tests, and 12-lead electrocardiogram (ECG) performed at screening
• Study participant must have good venous accessibility in both arms
• Study participant must be between 5 weeks and 24 months post-partum, inclusive, on Day -1
• Study participant must agree, when nipple cream is needed during the assessment phase, to use only lanolin nipple cream
• Study participant must have well established lactation and must be exclusively breast-feeding her infant (or not providing more than 1 supplemental bottle of formula/day) when enrolled in the study

Exclusion criteria:

• Study participant has history of breast implants, breast augmentation, or breast reduction surgery
• Study participant currently has active or unresolved mastitis at screening or Day -1
• Study participant currently has or had an active clinically significant infection within the last 6 weeks
• Study participant has any current or previous illness that, in the opinion of the investigator, might confound the results of the study or that could prevent, limit, or confound the protocol-specified assessments
• Study participant has suspected or known allergies, hypersensitivity, or intolerance to nipocalimab or its excipients

The data sharing policy of Johnson & Johnson Innovative Medicine is available at www.jnj.com/innovativemedicine/our-innovation/clinical-trials/transparency. As noted on this site, requests for access to the study data can be submitted through Yale Open Data Access (YODA) Project site at yoda.yale.edu.