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

Inclusion Criteria:

• Histologically confirmed, R/R, B-cell NHL according to the 2022 revision of theWorld Health Organization classification of lymphoid neoplasms [Alaggio 2022]defined as any of the following:

1. LBCL

2. FL Grade 3b

3. MCL

• The following criteria apply for details of prior treatment/therapy: R/R to at least 2 lines of therapy; if the most recent line of therapy was autologous hematologiccell transplant (HCT), relapse within 12 months of the transplant.

• Measurable disease by scan (diagnostic positron emission tomography-positive and/orcomputed tomography-measurable) as per Lugano Classification [Cheson 2014]. Magneticresonance imaging may be used when computed tomography with contrast iscontraindicated or when mandated by local practice.

• If sufficient archival material is not available from the latest relapse, a newtumor biopsy is required any time during screening, prior to conditioningchemotherapy.

• Participants who have received prior CD19-directed therapy as the prior line oftherapy:

1. must have achieved either a CR or partial response as a best response andmaintained the response for ≥ 3 months after receiving CD19-directed treatment,and

2. must still have CD19+ disease as determined by a local laboratory.

• Eastern Cooperative Oncology Group performance status ≤ 2

• Adequate organ function

• Written informed consent as per protocol.

• Participants are able to commit to the inpatient portion of the study, encompassingconditioning (if per the institution's standard practice), and frequent monitoringduring Days 1-15, as well as remain within 1 hour travel time of the clinical sitefor 28 days after each infusion.

Exclusion Criteria:

• History of a human immunodeficiency virus infection or acute or chronic activehepatitis B or C infection.

• History or presence of clinically relevant central nervous system (CNS) pathology.

• Unresolved Grade 1-2 Immune effector cell-associated neurotoxicity syndrome (ICANS)or experienced Grade 3-4 ICANS from prior chimeric antigen receptor T-cell.

• Unresolved graft-versus-host disease (GvHD) or Grade 3-4 acute GvHD from any priortherapy or moderate to severe chronic GvHD from any prior therapy.

• History of any one of the following cardiovascular conditions: class III or IV heartfailure as defined by the New York Heart Association [The Criteria Committee of theNew York Heart Association 1994], cardiac angioplasty or stenting, myocardialinfarction, unstable angina, or other clinically meaningful cardiac disease, withinthe past 6 months of study informed consent.

• History of malignancies, other than R/R NHL, unless the participant has beendisease-free for ≥ 1 year (certain noninvasive malignancies are allowed).

• Active primary, CNS-only, or systemic plus CNS involvement by lymphoma, unless theCNS involvement has been effectively treated.

• Active autoimmune disorders or inflammatory conditions that require systemicimmunosuppressive therapies, including therapeutic doses of steroids.

• Has received prior allogeneic HCT or prior solid organ transplant.

• Systemic bacterial, viral, fungal, or other infection that is untreated orunresponsive to appropriate treatment (or requires IV antibiotics at enrollment);participants must be afebrile for ≥ 48 hours. Prophylactic antibiotics, antivirals,and antifungals are permitted.

• Concurrent serious uncontrolled or unresolved medical condition, including anylaboratory abnormality or psychiatric illness.

• The following therapies within defined periods prior to the conditioning regimen:therapeutic doses of corticosteroids (> 0.5 mg/kg/day of prednisone or equivalent),lymphodepleting chemotherapeutic agents, live attenuated vaccines, prior systemiccancer therapy, investigational agents, including approved drugs being used offlabel, autologous HCT, donor lymphocyte infusions, radiation, alemtuzumab.

• Female who is breastfeeding or pregnant.

• Inability or unwillingness to comply with study procedures.

• Unwilling to use protocol specified contraceptive methods.

• Life expectancy of ≤ 8 weeks.

• For participants being considered for retreatment: had a DLT with prior ATA3219dose.