Study to Evaluate Safety and Tolerability of XmAb13676 (Plamotamab) in Patients With CD20-expressing Hematologic Malignancies

Inclusion criteria

• Able to provide written informed consent
• Diagnosis of either Non-CLL B cell malignancy
• Ineligible for or have exhausted standard therapeutic options and have relapsed or refractory disease
• ECOG performance status 0-2
• Fertile patients must agree to use highly effective contraception during and for 5 months (male patients) and 8 months (female patients) after last dose of XmAb13676
• Able and willing to complete the entire study

Additional Patient Inclusion Criteria for the DLBCL Cohort (Expansion Phase)

• Histologically confirmed diagnosis (specified by 2016 World Health Organization) of DLBCL or transformed low-grade lymphoma with measurable disease
• Patient must be refractory or have relapsed after 2 or more standard therapeutic options, at least one of which must have included anti-CD20 antibody therapy.
• Not a candidate for or refusing treatment with hematopoietic stem cell transplantation

Additional Patient Inclusion Criteria for the Follicular Lymphoma Cohort (Expansion Phase)

• Diagnosis of follicular lymphoma Grades 1-3a
• Patient must be ineligible for or have exhausted standard therapeutic options and have had 2 or more prior systemic regimens.

Exclusion criteria

• Cytotoxic chemotherapy, radiotherapy, or immunotherapy including other anti-CD20 antibodies within 4 weeks, or small molecule or investigational agents within 5 elimination half-lives of the first dose of XmAb13676
• Prior solid organ transplantation
• Failure to recover from Grade 3 or 4 toxicity from previous treatment
• Multiple myeloma/plasma cell leukemia or B cell acute lymphoblastic leukemia
• Known intolerance to CD20 monoclonal antibody therapy
• History of primary central nervous system lymphoma or neoplastic central nervous system disease
• Platelet count < 50 x 10^9/L
• Absolute neutrophil count < 1.0 x 10^9/L
• Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) at screening > 3x upper limit of normal (ULN)
• Bilirubin > 1.5 mg/dL unless prior diagnosis and documentation of ongoing hemolysis or Gilbert's syndrome has been made)
• Estimated creatinine clearance < 40 mL/min
• Active/uncontrolled autoimmune disease
• Clinically significant cardiac/cardiovascular disease, or pulmonary compromise
• Seizure disorder
• History of stroke with the past 6 mos prior to study entry
• History or evidence of a clinically unstable/uncontrollable disorder, condition or disease other than primary malignancy, that in the opinion of the Investigator would pose a risk to the patient safety or interfere with the study evaluation, procedures or completion
• Evidence of any serious bacterial, viral, parasitic or systemic fungal infections within the 30 days prior to study entry
• Positive test for human immunodeficiency virus (HIV) or hepatitis C (HCV) antibodies (unless HCV viral load test by PCR is negative)
• Positive test for HbsAg, or positive test for HBcAb (unless serology is positive due to recent intravenous immunoglobulin therapy). HBcAb positivity will be allowed if HBsAb is present or HBV-DNA is negative and patient is receiving Hep B reactivation prophylaxis.
• Patient is pregnant or breast feeding, or planning to become pregnant while enrolled in the study, and 8 months after the last dose of study drug
• Positive urine pregnancy test (ie, urine human chorionic gonadotropin) at screening
• Live viral vaccine within 2 weeks of the first dose of XmAb13676