Cirmtuzumab Consolidation for Treatment of Patients With Detectable CLL on Venetoclax

Inclusion Criteria: * Must have detectable CLL/SLL (\> 0.01% leukemia cells present) * Must have received at least 12 months of venetoclax. * Patients may be receiving venetoclax at the time of screening and study entry. * Patients who have discontinued venetoclax more than 6 months prior to study entry must still have a disease burden meeting criteria for low risk of TLS (i.e. no lymph node greater than 5 cm in diameter; absolute lymphocyte count less than 25 k/uL) Exclusion Criteria: Evidence of other clinically significant uncontrolled condition(s) including, but not limited to: * Uncontrolled and/or active systemic infection (viral, bacterial or fungal) * Chronic hepatitis B virus (HBV) or hepatitis C (HCV) requiring treatment. Note: subjects with serologic evidence of prior vaccination to HBV (i.e. hepatitis B surface (HBs) antigen negative, anti-HBs antibody positive and anti-hepatitis B core (HBc) antibody negative) or positive anti-HBc antibody from intravenous immunoglobulins (IVIG) may participate. * Child class B or C cirrhosis Treatment with any of the following within 7 days prior to the first dose of cirmtuzumab: * Steroid therapy for anti-neoplastic intent * Biologic agent (monoclonal antibody) within 30 days for anti-neoplastic intent. * Chemotherapy (purine analog or alkylating agent) or target small molecule agent within 14 days or 5 half-lives (whichever is shorter), or has not recovered to less than CTCAE grade 2 clinically significant adverse effect(s)/toxicity(s) of previous therapy. * CLL therapy, aside from venetoclax. * History of other malignancy that could affect compliance with the protocol or interpretation of results (example: patients with a history of curatively treated basal or squamous cell carcinoma of the skin or in situ carcinoma of the cervix are generally eligible.) * Women who are pregnant or lactating