Inclusion Criteria: 

• Adults 18 to 65 years of age, inclusive.
• The completion of the following vaccinations at least 14 days prior to Visit 0:
  • COVID-19 vaccination series according to the current Centers for Disease Control and Prevention (CDC) Advisory Committee on Immunization Practices (ACIP); recommendations; and
  • At least one dose of the herpes zoster vaccination series; and
  • Current year seasonal influenza vaccine, if available.
• History of APS according to the updated 2006 Sapporo classification criteria, including at least one of the following within the prior 5 years:
  • Arterial thrombosis, except transient ischemic attack; or
  • Venous thrombosis, except superficial thrombophlebitis; or
  • Pregnancy morbidity, based on the updated 2006 Sapporo APS classification criteria; or
  • Microvascular APS, with at least one of the following:
    • Renal biopsy documentation of aPL-associated nephropathy; or
    • Lung biopsy or bronchoalveolar lavage documentation of diffuse alveolar hemorrhage (DAH); or
    • Skin biopsy documentation of livedoid vasculopathy.
• History of triple positive aPL within the prior 5 years and at least 12 weeks prior to enrollment, including all of the following:
  • aCL IgG level > Upper Limit of Normal (ULN); and
  • aβ2GPI IgG level > ULN; and
  • Positive LA test.
• Confirmation of triple positive aPL at screening, including all of the following:
  • aCL IgG level ≥ 40 GPL; and
  • aβ2GPI IgG level ≥ 40 SGU; and
  • Positive LA test.
• Willing and able to undergo anticoagulation with warfarin or low molecular weight heparin (LMWH), if there is a history of arterial or venous thrombosis.
• Willing and able to discontinue direct oral anticoagulants, including factor Xa inhibitors and direct thrombin inhibitors, if applicable.

Exclusion Criteria:

• Inability or unwillingness to give written informed consent.
• Inability or unwillingness to comply with study protocol.
• Systemic autoimmune diseases other than APS, including but not limited to:
  • Systemic lupus erythematosus (SLE) meeting the EULAR/ACR criteria;
  • Rheumatoid arthritis meeting the ACR/EULAR classification criteria;
  • Small, medium, or large vessel vasculitis meeting ACR classification criteria.
• Catastrophic APS classification within the prior 90 days.
• Acute arterial or venous thrombosis within the prior 30 days.
• Use of the following medications:
  • Any prior treatment with CD38 targeting monoclonal antibodies, including daratumumab or isatuximab-irfc;
  • Administration of the Janssen COVID-19 vaccine within the prior 14 days;
  • The following within the prior 30 days:
    • Corticosteroids > 10 mg/day prednisone or equivalent;
    • Direct oral anticoagulants (DOACs);
    • Live attenuated vaccines;
    • IVIG.
  • Azathioprine, methotrexate, mycophenolate mofetil, mycophenolate sodium, lefluonomide, or calcineurin inhibitors within the prior 90 days;
  • Cyclophosphamide within the prior 90 days;
  • Immunomodulatory or immunosuppressive biologic agents, including belimumab, within the prior 90 days or 5 half-lives, whichever is greater;
  • Investigational agents within the prior 90 days or 5 half-lives, whichever is greater, except for COVID-19 vaccines and medications for prevention or treatment of COVID-19 per FDA Emergency Use Authorization (EUA);
  • Biologic B cell depleting agents including rituximab with either of the following:
    • Treatment within the prior 180 days; or
    • CD19+ absolute count < Lower Limit of Normal (LLN).
• Plasma exchange within the prior 90 days.
• Hemodialysis within the prior 90 days.
• Major surgical procedure within the prior 60 days.
• Known allergy, hypersensitivity, or intolerance to boron, malitol, sorbitol, corticosteroids, monoclonal antibodies including daratumumab, human proteins, or their excipients.
• Allergy, intolerance, or contraindication to acyclovir, valacyclovir, and famciclovir.
• Active or chronic infection, including the following:
  • Active bacterial, viral, fungal, or opportunistic infection;
  • Chronic infection requiring suppressive antibiotic treatment;
  • Intravenous antibiotics or hospitalization for infection within the prior 30 days;
  • Evidence of current or prior Mycobacterium tuberculosis infection (Section 8.3.3);
  • Human immunodeficiency virus (HIV);
  • Current or prior infection with hepatitis B virus (HBV);
  • Current or prior infection with hepatitis C virus (HCV), except adequately treated HCV with sustained virologic response ≥ 12 weeks;
  • Positive SARS-CoV-2 nucleic acid amplification test (NAAT) within the prior 14 days;
  • History of recurrent herpes zoster, or history of herpes zoster ophthalmicus, disseminated herpes zoster, or disseminated herpes simplex.
• The following laboratory abnormalities:
  • Absolute neutrophil count < 1500/mm^3;
  • Platelets < 100,000/mm^3 ;
  • Hemoglobin (Hgb) < 10 g/dL
  • Aspartate aminotransferase (AST), alanine aminotransferase (ALT), or alkaline phosphatase > 2 x the Upper Limit of Normal (ULN);
  • Total bilirubin > 2 x ULN, except in the case of congenital bilirubinemia then direct bilirubin > 2 x ULN;
  • eGFR < 45 ml/min/1.73 m^2 .
• History of primary immunodeficiency.
• History of solid organ or hematopoietic stem cell transplantation.
• Comorbidities requiring systemic corticosteroid therapy, including those which have required three or more courses of systemic corticosteroids within the 12 months prior to Visit 0.
• Any of the following conditions with FEV1 < 70% predicted within the prior 90 days:
  • Asthma;
  • Chronic obstructive pulmonary disease (COPD);
  • DAH.
• Pulmonary hypertension.
• Poorly controlled diabetes mellitus, defined as hemoglobin A1c (HbA1c) ≥ 8.0%.
• Concomitant malignancy or history of malignancy, except adequately treated or excised nonmetastatic squamous cell carcinoma, basal cell skin carcinoma, or cervical carcinoma in situ.
• Clinically significant cardiac disease, including but not limited to:
  • Myocardial infarction within the prior 6 months; or
  • Unstable or uncontrolled disease or condition related to or affecting cardiac function, including but not limited to:
    • Unstable angina; or
    • Congestive heart failure, New York Heart Association Class II-IV; or
    • Uncontrolled cardiac arrhythmia.
• Current diagnosed mental illness or current diagnosed or self-reported drug or alcohol abuse which, in the opinion of the investigator, would interfere with the participant’s ability to comply with study requirements.
• Severe, progressive, or uncontrolled renal, hepatic, hematological, gastrointestinal, pulmonary, cardiac, or neurological disease.
• Past or current medical problems or findings from physical examination or laboratory testing that are not listed above, which, in the opinion of the investigator, may pose additional risks from participation in the study, may interfere with the participant’s ability to comply with study requirements, or may impact the quality or interpretation of the data obtained from the study.
• Lack of peripheral venous access.
• Pregnancy, or planning a pregnancy during the 48 week study duration.
• Breast-feeding.
• Unwillingness to use medically acceptable non-prothrombotic contraception if of reproductive potential and engaging in sexual activity that could lead to pregnancy (Section 7.5).

Note: Other protocol defined Inclusion/Exclusion Criteria may apply.

Eligibility last updated 9/19/23. Questions regarding updates should be directed to the study team contact.