Would you use belimumab in a breastfeeding patient with SLE who has persistent joint pain, leukopenia and elevated dsDNA despite HCQ and azathioprine?

While our understanding of the biologics safety in breastfeeding is still evolving and data is limited, based on my literature review, there are no signals that Belimumab is associated with an increased risk of adverse events in pregnancy/breastfeeding. Belimumab is a relatively large molecule, therefore, it is unlikely to be expressed in breast milk at high concentrations. GI absorption of Belimumab is minimal, further decreasing potential risks to the infant. A comprehensive up-to-date reference on rheumatologic medications in pregnancy/breastfeeding was published by the British Society of Rheumatology in 2022 (Russell et al., PMID 36318966).

I agree with the comments from Drs. @Dr. First Last and @Dr. First Last regarding evidence to date that belimumab is safe for breastfeeding mothers and their child as well as likely during pregnancy. My additional comment addresses the issue of musculoskeletal complaints in a patient despite HCQ and azathioprine even in the presence of abnormal serology as elevated dsDNA and leukopenia. The first order of business is to determine if joint pain is in fact inflammatory and as per Dr. Pisetsky's work categorized as Type 1. On the other hand, many lupus patients can have symptoms of joint pain absent clear evidence of an immune-mediated inflammatory process (i.e. synovitis or tenosynovitis) which can be categorized as Type II and rather than re...

YES!!! As a large monoclonal antibody, Belimumab has little, if any passage into breastmilk, similar to other biologics. And if this medication did enter into breastmilk, as a protein, it would be digested by the infants stomach and not absorbed or have any therapeutic possiblity. This also why they have to be injected or infused. LactMed is a great resource for this information.