Key Inclusion Criteria:
* Diagnosis of cardiac sarcoidosis based on one of the following pathways:
* Histological Diagnosis
* Myocardial or extracardiac biopsy demonstrating non-caseating granuloma with no alternative cause identified AND
* Abnormal FDG uptake on cardiac PET-CT conducted within six weeks of Screening, in a pattern consistent with active cardiac sarcoidosis AND
* Exclusion of other causes for cardiac manifestations
* Clinical Diagnosis
* One or more of the following is present:
* Steroid +/- immunosuppressant responsive cardiomyopathy or heart block
* Unexplained reduced LVEF (\< 40%) and/or segmental wall motion abnormalities not related to coronary artery disease or another defined cause
* Unexplained sustained (spontaneous or induced) VT
* Mobitz type II 2nd degree heart block or 3rd degree heart block
* CT chest and/or FDG PET-CT showing features consistent with pulmonary sarcoidosis and/or hilar lymphadenopathy AND
* Abnormal FDG uptake on cardiac PET-CT conducted within 6 weeks of Screening, in a pattern consistent with active cardiac sarcoidosis AND
* Exclusion of other causes for cardiac manifestations
* Active cardiac sarcoidosis based on abnormal FDG uptake on cardiac PET-CT conducted within six weeks of Screening, in a pattern consistent with active cardiac sarcoidosis
* No current treatment with immunosuppressive medications other than a steroid-sparing medication (including methotrexate, leflunomide, azathioprine, or mycophenolate mofetil), and/or prednisone (or equivalent) at a dose of ≤ 20mg daily at Baseline
Key Exclusion Criteria:
* Receipt of a non-biologic DMARD or immunosuppressive agent other than methotrexate, leflunomide, azathioprine, mycophenolate mofetil, hydroxychloroquine, or glucocorticoids within 28 days prior to screening
* Receipt of a bDMARD or tsDMARD, including non-depleting B-cell-directed therapy (eg, belimumab), T cell costimulatory blockade (eg, abatacept), TNF-alpha inhibition (eg, infliximab, adalimumab, etanercept, golimumab, certolizumab pegol), interleukin-6 inhibition (eg, tocilizumab, sarilumab), interleukin-1 inhibition (eg, anakinra), JAK inhibition (eg, tofacitinib, upadacitinib, baricitinib), or other biologic immunomodulatory agent within 28 days prior to screening
* Receipt of any biologic B cell-depleting therapy (eg, rituximab, ocrelizumab, obinutuzumab, ofatumumab, inebilizumab) in the 6 months prior to screening; receipt of such a B cell-depleting agent in the period 6-12 months prior to screening is exclusionary unless B cell counts have returned to ≥ LLN
* History of venous thromboembolism (VTE) or an increased risk for VTE
* Current smoking
* Estimated glomerular filtration rate \< 30 mL/min/1.73 m2 by Modification of Diet in Renal Disease Study (MDRD) equation
* Blood tests at screening that meet any of the following criteria:
* Hemoglobin \< 7.5 g/dL
* Neutrophils \< 1000/mm3
* Absolute lymphocyte count \< 500/mm3
* Platelets \< 100 x 109/L
* Subjects with the following abnormal liver function tests:
* Aspartate aminotransferase (AST) \> 2x ULN
* Alanine aminotransferase (ALT) \> 2x ULN
* Total bilirubin (TBL) \> 2x ULN unless AST, ALT, and hemoglobin are within central laboratory normal range and the patient has a known history of Gilbert syndrome
* Active, clinically significant infection at the time of Screening
* Active malignancy or history of malignancy that was active within the last 5 years, except as follows:
* In situ carcinoma of the cervix following apparently curative therapy \> 12 months prior to screening,
* Cutaneous basal cell or squamous cell carcinoma following apparently curative therapy, or
* Prostate cancer treated with radical prostatectomy or radiation therapy with curative intent \> 3 years prior to screening and without known recurrence or current treatment
