Concentration of Ofatumumab in the Breast Milk of Lactating Women With Relapsing Forms of Multiple Sclerosis

This study measures how much of a multiple sclerosis (MS) medication called ofatumumab (Kesimpta) passes into breast milk when nursing mothers take it. This helps researchers understand whether it is safe to breastfeed while on this treatment. **You may be eligible if...** - You are a woman with a relapsing form of MS - You are at least 18 years old and have recently given birth (at least 37 weeks gestation) - You are currently breastfeeding exclusively and plan to start or restart ofatumumab between 2 and 24 weeks after delivery - The decision to take ofatumumab and breastfeed was made independently with your doctor before joining the study **You may NOT be eligible if...** - You have had breast implants, augmentation, or reduction surgery - You have a history of alcohol or drug abuse in the past year - You have active hepatitis B, HIV, or a serious immune deficiency - You are pregnant - You have had a cancer diagnosis in the past 5 years - You received anti-CD20 therapy during the second or third trimester Talk to your doctor to see if this trial is right for you.