The study will examine the safety profile of SGN-CD19B administered as a single agent. The main purpose of the study is to estimate the highest dose that does not cause unacceptable side effects of SGN-CD19B in patients with relapsed or refractory aggressive B-cell non-Hodgkin lymphoma (NHL) subtypes of diffuse large B-cell lymphoma (DLBCL) and Grade 3 follicular lymphoma (FL3). Additionally, the pharmacokinetic profile and antitumor activity of SGN-CD19B will be assessed.

SGN-CD19B will be given to patients at increasing doses every 28 days (or on an alternative dosing schedule of every 42 days).

Individual expansion cohorts of up to approximately 20 patients will be opened at dose levels selected by the Safety Monitoring Committee based on the aggregate known safety and activity data to further define the safety and antitumor activity in refractory and relapsed disease subgroups.

Inclusion Criteria:

• Relapsed, refractory, or progressive disease following at least 2 prior systemic therapies
• Measurable disease
• Eastern Cooperative Oncology Group status of 0 or 1
• Adequate baseline renal and hepatic function

Exclusion Criteria:

• Prior treatment with CD19 directed agents unless CD19 expression is confirmed after completion of CD19-directed treatment
• Known HIV, active hepatitis B or active hepatitis C infection
• Prior allogeneic stem cell transplant
• Inadequate lung function
• Anticancer treatment within 4 weeks of study drug or 2 weeks if patient experienced disease progression on prior treatment