RecruitingBiological interventionDaratumumab in Primary Antiphospholipid SyndromeThe purpose of this study is to see if the study medication, daratumumab, is safe to treat individuals with Anti-Phospholipid Syndrome (APS). Three daratumumab dosing cohorts are planned with up to six participants in each dosing cohort with the potential to enroll an additional 4 subjects in the highest safe dose (HSD) cohort, for a total of up to 22 participants. The dosing cohorts are: 4 mg/kg, 8 mg/kg, and 16 mg/kg. Each cohort will receive intravenous (IV) administration of daratumumab according to the following schedule, for a total of 8 doses. The primary objective is to determine the safety of daratumumab in APS defined as Dose Limiting Toxicities (DLTs) occurring during the dose escalation phase.