Summary

This study will evaluate the safety and efficacy of NKTR-255 following CD19-directed chimeric
antigen (CAR)-T cell therapy in patients with relapsed or refractory (R/R) large B-cell
lymphoma (LBCL).

NKTR-255 is an investigational IL-15 receptor agonist designed to boost the immune system's
natural ability to fight cancer. T cells are infection fighting blood cells that can kill
tumor cells. Chimeric antigen (CAR)-T cell product consists of genetically engineered
T-cells, modified to recognize CD19, a protein on the surface of cancer cells. These
CD19-specific T cells may help the body's immune system identify and kill CD19-positive
cancer cells. Giving NKTR-255 following the treatment with CD19 CAR-T cell therapy may work
better in treating large B-cell lymphoma than either drug alone.

Objectives

Patients will be treated with lymphodepletion chemotherapy (as recommended by the CAR-T cell
manufacturer) and soon after will receive a one-time CD19-directed CAR-T cell infusion (as
per product label). Study drug (NKTR-255 or placebo) will be administered intravenously
approximately 14 days after CAR-T cell infusion and administered every 3 weeks for up to 7
cycles or 5 months (whichever is earlier) in the absence of disease progression or
unacceptable toxicity. After completion of study treatment, patients will be followed-up at
30 days, and then at 9,12,18, 24, and 36 months after CAR-T cell infusion.

The study will be conducted in two stages: Stage 1 (Phase II) is expected to complete the
enrollment of 56 patients by the end of 2023. Primary endpoint data will be available in the
second half of 2024. Stage 2 (Phase III) is expected to initiate before the end of 2024.

Eligibility

1. Male or female = 18 years of age at the time of consent.
2. Received standard of care therapy with axi-cel or liso-cel (Stage 1 and Stage 2), or tisa-cel (Stage 2 only), for the respective FDA (or Summary of Product Characteristics [SmPC]) approved indication(s):
3. liso-cel: Patients with LBCL (including diffuse LBCL [DLBCL] not otherwise specified [including DLBCL arising from indolent lymphoma], high-grade B-cell lymphoma, primary mediastinal LBCL, and follicular lymphoma Grade 3B), who have:
4. refractory disease to first-line chemoimmunotherapy or relapse within 12 months of first-line chemoimmunotherapy;
5. refractory disease to first-line chemoimmunotherapy or relapse after first-line chemoimmunotherapy and are not eligible for hematopoietic stem cell transplantation (HSCT) due to comorbidities or age; or,
6. relapsed or refractory disease after two or more lines of systemic therapy.
7. axi-cel: For the treatment of adult patients with LBCL that is:
8. refractory to first-line chemoimmunotherapy;
9. relapses within 12 months of first-line chemoimmunotherapy; or
10. R/R LBCL after 2 lines of systemic therapy, including DLBCL not otherwise specified, primary mediastinal LBLC, high grade B-cell lymphoma, and DLBCL arising from follicular lymphoma.
11. tisa-cel (Stage 2 only): Adult patients with R/R LBLC after two lines of systemic therapy including DLBCL not otherwise specified, high grade B-cell lymphoma and DLBCL arising from follicular lymphoma.
12. Received lymphodepleting chemotherapy regimen according to the respective FDA (or SmPC) label for CAR-T cell therapy.
13. Fluorodeoxyglucose (FDG)-avid disease on positron emission tomography (PET) imaging within 30 days prior to CAR-T cell infusion.
14. FDG avid lesion(s) on PET/computed tomography (CT) scan following bridging therapy and prior to lymphodepletion, where applicable.
15. Evidence of CD19 expression on any prior or current NHL tumor specimen or a high likelihood of CD19 expression based on disease histology per investigator's assessment.
16. Within 7 days prior to leukapheresis, patient should have an Eastern Cooperative Oncology Group (ECOG) Performance Status 0 or 1 (Appendix 3).
17. Regarding prior systemic anti-tumor therapy:
18. At least 3 months have elapsed since systemic immune checkpoint inhibitory/immune stimulatory therapy (eg, ipilimumab, nivolumab, pembrolizumab, atezolizumab, OX40 agonists, 4-1BB agonists, etc).
19. At least 2 weeks have elapsed since other prior systemic antitumor therapy.
20. Bridging therapy (including steroids) is permitted between leukapheresis and lymphodepletion as long as Exclusion Criterion 1 is satisfied.
21. Adequate organ function, defined as:
22. Adequate bone marrow function (prior to lymphodepletion) for lymphodepletion chemotherapy defined as: absolute neutrophil count (ANC) = 1000 cells/mm3, platelets = 50,000 cells/mm3, and hemoglobin = 8 g/dL in the absence of bone marrow involvement by lymphoma. No transfusion within 3 days of bone marrow function assessment; growth factor support is allowed as per institutional practice.
23. Calculated creatinine clearance (Cockcroft/Gault) > 30 mL/min (Appendix 4).
24. ALT and AST = 3 × upper limit of normal (ULN; or < 5 × ULN for patients with lymphomatous infiltration of the liver) and total bilirubin = 2 × ULN (or < 3.0 × ULN for patients with Gilbert's syndrome or lymphomatous infiltration of the liver).
25. Adequate pulmonary function, oxygen saturation on room air (SaO2) = 92%. Patients with a history of interstitial lung disease should undergo pulmonary function testing and must have a forced expiratory volume in 1 second (FEV1) of = 50% of predicted value or diffusing capacity of the lung for carbon monoxide (DLCO; corrected) = 40% of predicted value.
26. Adequate cardiac function, defined as left ventricular ejection fraction (LVEF) = 40% as assessed by echocardiogram (ECHO) or multiple uptake gated acquisition (MUGA) within 60 days before randomization.
27. ECG demonstrating Fridericia's corrected QT interval (QTcF) < 470 ms. Patients with QTcF = 470 ms will require clearance by a local cardiologist.
28. Women of reproductive potential (defined as all women physiologically capable of becoming pregnant) must agree to use suitable methods of contraception from the start of study treatment until 1 month after the last dose of study drug (Appendix 6).
29. Males who have partners of reproductive potential must agree to use an effective barrier contraceptive method from the start of study treatment until 1 month after the last dose of study drug.
30. Ability to understand and provide written informed consent.
31. Able and willing to comply with study visit schedule and procedures, including tumor biopsy where accessible. Additional Eligibility Criteria Following CD19 Targeted CAR-T Cell Infusion Patients who have received commercially released CAR-T cell infusion must satisfy the following criteria on the day of randomization:
32. No fever = 38.0°C/Grade = 1 CRS (American Society for Transplant and Cellular Therapy [ASTCT] criteria within 24 hours.
33. No Grade = 3 CRS (ASTCT criteria) within 72 hours.
34. No previous Grade = 3 immune effector cell-associated neurotoxicity syndrome (ICANS) of > 72 hours duration.
35. No Grade = 2 ICANS (ASTCT criteria).
36. No tocilizumab and/or dexamethasone within 48 hours.
37. No active, serious, and/or uncontrolled infection(s).
38. No other contraindication according to the Investigator's assessment.
39. Patients must satisfy the following laboratory test results:
40. ANC or absolute granulocyte count (AGC) = 1000/µL
41. Platelets = 30,000/µL
42. Hemoglobin = 8 g/dL
43. Leukocytes = 3000/µL Randomization should occur no more than 1 day before the first study drug infusion.

Treatment Sites in Georgia