TCR Reserved and Power3 (SPPL3) Gene Knock-out Allogeneic CD19-targeting CAR-T Cell Therapy in r/r B-ALL

A Phase 1/2 Multicenter Study Evaluating the Safety and Efficacy of TCR Reserved and Power3 (SPPL3) Gene Knock-out Allogeneic CD19-targeting CAR-T Cell Therapy in Adults With Refractory/Relapsed B-cell Acute Lymphoblastic Leukaemia

The safety and efficacy of the chimeric antigen receptor (CAR)-T, a CD19-targeting, TRAC and Power3 (SPPL3) double gene deleted allogeneic CAR-T cell product, are undergoing rigorous evaluation in non-Hodgkin's lymphoma (NHL) subjects from the ATHENA trial (NCT06014073). Unexpectedly, expansion of the initial residual CD3-positive CAR T from products were measured in patients' peripheral blood (PB) without exception. Accompanying with host immune reconstitution and appearance of the detectable B cells, the CD3-positive allogenic CAR T cells exhibited a compelling amplification advantage over CD3-negative CAR T cells. The amplification of CD3-positive CAR T cell population dynamically suppressed host B cell recovery, and presumably surveilled the recurrence or progression of tumors, but did not induce typical Graft-versus-host-disease (GvHD). Additionally, a series of in vitro experiments illustrated that the human leukocyte antigen (HLA)-mismatched fratricide between host T cells and TCR-reserved Power3 (SPPL3)-deleted allogenic CAR T cells was markedly slashed, which in combination with investigators' observed clinical safety data supported the notion that only genomic deletion of Power3 (SPPL3) gene in allo-CAR T cells is sufficient to overcome GvHD and host T cell-mediated rejection response.

In this study, investigators will disable the Power3 (SPPL3) gene of T cells from healthy donors to prepare CAR T cells (purified CAR-positive T cells > 90%). This approach harnesses the tonic signaling of CAR T cells, resulting in enhanced persistence and improved response to treatment. The purpose of this study is to evaluate the safety and efficacy of allogeneic Power3 (SPPL3) knock-out CD19 CAR-T in B-cell acute lymphoblastic leukaemia (B-ALL).

Phase 1 (dose escalation)

In phase 1, 6-18 subjects will be enrolled. Subjects will receive 3 doses of allogeneic Power3 (SPPL3) knock-out CD19 CAR-T cell therapy ( 1 × 10^6 cells/kg、3 × 10^6 cells/kg、6 × 10^6 cells/kg) increases from low dose to high dose according to the "3 + 3" principle:

Three (3) subjects are enrolled in a cohort corresponding to a dose level. If 1 subject in a cohort of 3 subjects experiences a dose-limiting toxicity (DLT), 3 additional subjects will be enrolled at the current dose level. For safety purposes, the administration of allogeneic Power3 (SPPL3) knock-out CD19 CAR-T will be staggered by 28 days between the first two subjects in each cohort. And for each of the remaining cohorts, the administration of allogeneic Power3 (SPPL3) knock-out CD19 CAR-T will be staggered by 28 days before enter into the next cohort.

Phase 2 (expansion cohort)

In phase 2, 10 to 12 subjects will be enrolled and receive cell infusion at dose of recommended phase 2 dose (RP2D), which will be determined based on the maximum tolerated dose (MTD), occurrence of DLT, the obtained efficacy results, pharmacokinetics/pharmacodynamics and other data according to the phase 1.

Objectives

The primary objectives of the phase 1 were to evaluate the tolerability and safety of allogeneic Power3 (SPPL3) knock-out CD19 CAR-T in patients with refractory/relapsed (r/r) B-ALL, and determine RP2D. The primary purpose of the phase 2 study was to evaluate the efficacy of allogeneic Power3 (SPPL3) knock-out CD19 CAR-T in the above population.

Inclusion Criteria:

1. Age 16-70 (inclusive).

2. Patient with r/r CD19+ B-ALL, as per guidelines (NCCN, 2019)

   • For patients with bone marrow involvement, morphologically confirmed with ≥ 5% leukaemic blasts in the bonemarrow.
   • Definition of relapsed disease: Bone marrow or extramedullary relapse after achieving CR with initial treatment, or any bone marrow or extramedullary relapse after allogeneic hematopoietic stem cell transplantation (allo-HSCT).
   • Refractory disease is defined by not achieving an initial CR after 2 cycles of a standard chemotherapy regimen (primary refractory). Subjects who were refractory to subsequent chemotherapy regimens after an initial remission were considered chemorefractory.

3. Toxicities due to prior therapy must be stable and recovered to ≤ Grade 1 (except for hematological toxicities and clinically non-significant toxicities such as alopecia).

4. Eastern Cooperative Oncology Group (ECOG) performance status ≤ 2.

5. Adequate renal, hepatic, pulmonary and cardiac function defined as:

   • Serum creatinine≤1.5 upper limit of normal (ULN) or creatinine clearance (as estimated by Cockcroft Gault) ≥ 60 mL/min.
   • Serum alanine aminotransferase / aspartate aminotransferase (ALT/AST) ≤ 3 upper limit of normal (ULN); Total bilirubin ≤ 1.5 ULN, except in subjects with 3) Gilbert's syndrome.
   • Cardiac ejection fraction ≥ 50%, no evidence of pericardial effusion as determined by an echocardiogram (ECHO), and no clinically significant electrocardiogram (ECG) findings.
   • Coagulation Function: International Normalized Ratio (INR) ≤ 1.5 times the upper limit of normal (ULN), and Activated Partial Thromboplastin Time (APTT) ≤ 1.5 times ULN.
   • Baseline oxygen saturation >91% on room air.

6. Subjects of both genders who are willing to practice birth control from the time of consent through 6 months after the completion of conditioning chemotherapy. Females of childbearing potential must have a negative serum or urine pregnancy test (females who have undergone surgical sterilization or who have been postmenopausal for at least 2 years are not considered to be of childbearing potential).

7. Voluntarily participate in this clinical trial and sign an informed consent form.

Exclusion Criteria:

1. Expected survival time < 3 months per Principal Investigator's opinion.
2. History of malignancy other than nonmelanoma skin cancer or carcinoma in situ (e.g. cervix, bladder, breast) unless disease free for at least 3 years.
3. Patients who received any immunocellular or HSCT therapy within 3 months before enrollment.
4. Active central nervous system (CNS) leukaemia (CNS-3).
5. Clinically active significant CNS dysfunction.
6. Known history of irreversible severe neurological toxicity related to previous antileukaemic treatment leading to organic central nervous system lesions.
7. Use of previous anti-leukemic therapy within 5 half-lives prior to allogeneic Power3 (SPPL3) knock-out CD19 CAR-T administration; participation in non-interventional registries or epidemiological studies is allowed.
8. Radioimmunotherapy, radiotherapy, within 8 weeks (except prophylaxis of CNS involvement) before Inclusion.
9. History of severe immediate hypersensitivity reaction to any of the agents or any component used in this study.
10. Presence or suspicion of fungal, bacterial, viral, or other infection that is uncontrolled or requiring intravenous (IV) antimicrobials for management.
11. Uncontrolled or active infectious diseases, such as human immunodeficiency virus (HIV) infection, acute or chronic active hepatitis B or C, epstein-barr virus (EBV), and cytomegalovirus (CMV) infection.
12. History or presence of CNS disorder such as seizure disorder, cerebrovascular ischemia/hemorrhage, dementia, cerebellar disease, or any autoimmune disease with CNS involvement.
13. Subjects with cardiac atrial or cardiac ventricular lymphoma involvement.
14. History of myocardial infarction, cardiac angioplasty or stenting, unstable angina, or other clinically significant cardiac disease within 12 months of enrollment.
15. Expected or possible requirement for urgent therapy within 6 weeks due to ongoing or impending oncologic emergency (eg, tumor mass effect, tumor lysis syndrome).
16. Primary immunodeficiency.
17. History of autoimmune disease (e.g. Crohn's, rheumatoid arthritis, systemic lupus) resulting in end organ injury or requiring systemic immunosuppression/systemic disease modifying agents within the last 2 years.
18. History of symptomatic deep vein thrombosis or pulmonary embolism requiring systemic anticoagulation within 6 months of enrollment.
19. Any medical condition likely to interfere with assessment of safety or efficacy of study treatment.
20. Vaccine ≤ 6 weeks prior to planned start of conditioning regimen.
21. Presence of DSAs directed against allogeneic SPPL3 knock-out CD19 CAR-T.
22. In the investigator's judgment, the subject is unlikely to complete all protocol-required study visits or procedures, including follow-up visits, or comply with the study requirements for participation.