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