Study Evaluating SC291 in Subjects With r/r B-cell Malignancies (ARDENT)

Inclusion Criteria: Male or female subjects aged 18-75 years at the time of signing informed consent. Diagnosis of NHL (WHO 2016 criteria) or CLL (iwCLL criteria), including: Large B-cell lymphoma, including diffuse large B-cell lymphoma (DLBCL) not otherwise - - specified (including DLBCL arising from indolent lymphoma), primary mediastinal large -- - B-cell lymphoma, high grade B-cell lymphoma, follicular lymphoma grade 3B Follicular lymphoma (dose escalation only except for follicular lymphoma grade 3B) Marginal zone lymphoma (dose escalation only) Mantle cell lymphoma (dose escalation only) CLL or SLL Relapsed/refractory disease after at least 2 prior systemic regimens per standard of care or after autologous stem cell transplant ECOG performance status of 0 or 1. At least one measurable lesion per Lugano Classification (NHL); CLL subjects must meet iwCLL treatment criteria Life expectancy ≥12 weeks Exclusion Criteria: Prior anti-CD19 therapy including CD19-directed CAR T treatment or other CD19-directed antibody or cell therapy (e.g., NK cell). (Part 2 dose expansion only - prior approved CD19-directed CAR T therapy required) History of primary central nervous system (CNS) lymphoma or presence of CNS metastases Systemic anticancer therapy (including platinum-based chemotherapies and I/O therapies) or radiotherapy within 14 days of SC291 (28 days for biologics) Autologous HSCT within 6 weeks of treatment with SC291 (or allogeneic HSCT at any time). Active autoimmune disease or any other diseases requiring immunosuppressive therapy or corticosteroid therapy (defined as >20 mg/day prednisone or equivalent). History or presence of cardiac or CNS disorders as defined in the protocol