A Study to Evaluate the Safety and Preliminary Efficacy of ATA3219 in Participants With Relapsed/Refractory B-cell Non-Hodgkin Lymphoma

The purpose of this study is to evaluate the safety and preliminary efficacy of ATA3219 in participants with relapsed/refractory (R/R) B-cell non-Hodgkin Lymphoma (NHL).

This is a phase 1, open-labeled study to evaluate the safety and preliminary efficacy of ATA3219 (as monotherapy) in participants with NHL. During dose escalation, participants with R/R large B-cell lymphoma (LBCL), follicular lymphoma (FL), or mantle cell lymphoma (MCL) may be enrolled sequentially. Up to 4 dose levels will be explored in dose escalation. Prior to undergoing any screening procedure, prospective participants must undergo the ATA3219 inventory check assessments to ensure availability of an appropriate partially human leukocyte antigen-matched ATA3219 lot. Before administration of ATA3219, participants will receive conditioning chemotherapy within 7 days of enrollment. Participants will be hospitalized for at least 1 week to receive ATA3219, which will be administered by intravenous (IV) infusion on Day 1 in a staggered manner to allow appropriate safety monitoring. Four different dose levels will be studied in a sequential manner, and a lower dose level may be added, if needed. At least 3 and up to 6 dose-limiting toxicity (DLT)-evaluable participants, those who complete the 28-day DLT observation period, will be assessed at each dose level. Disease response will be assessed on Day 28 (+ 5 days) following each dose of ATA3219 by the investigator using the Lugano criteria (Cheson 2014). Participants who achieve complete response (CR) or progressive disease at Day 28 will enter the 24-month follow-up period. Participants who achieve partial response (PR), stable disease, or those who relapse within 12 months of the ATA3219 dose, may be considered for the second dose of ATA3219 per protocol. A third and final dose of ATA3219 may also be considered as per protocol. After recommended phase 2 dose (RP2D) has been determined in the dose escalation stage, additional participants may be enrolled in 2 expansion cohorts (CD19-directed naive and prior CD19-directed therapy), opened at sponsor discretion and dosed at the proposed RP2D. After treatment is completed or discontinued, participants will be followed for response and safety for up to 24 months from the last dose of ATA3219. After 2 years, a separate long-term follow-up study will be conducted to follow participants for up to a total of 15 years.