Phase II Open‑Label Multicenter Study of Autologous Dual‑CAR T‑Cell Therapy (AUTO1) in Ph‑negative CD19⁺ B‑precursor ALL Patients with MRD ≥10⁻⁴ in First Remission

Primary objective: to assess the effect of Obe‑cel on event free survival at 12 months in patients with minimal residual disease after frontline therapy for B‑precursor acute lymphoblastic leukaemia. Secondary objectives include evaluation of MRD response rates at month 3 (complete MRD negativity, intermediate MRD, and MRD failure), determination of the duration of MRD negativity, measurement of time to molecular or hematologic relapse, analysis of the impact of Obe‑cel on the duration of complete hematologic remission, overall survival, relapse‑free survival, and repeat assessment of event free survival, safety and tolerability profiling, characterization of relapse localization and CD19 expression, incidence of secondary malignancies, interval from enrollment to first infusion, frequency of bridging chemotherapy cycles, eligibility for lymphodepletion, rates of withdrawal after a single infusion, delayed second‑dose administration, hospitalization days, kinetics of CAR‑T expansion, B‑cell reconstitution, occurrence and duration of severe hypogammaglobulinemia and immunoglobulin replacement, rate of subsequent allogeneic stem‑cell transplantation, and correlative analyses linking CAR‑T persistence in bone marrow and peripheral blood, B‑cell aplasia, and T‑cell phenotypes with clinical outcomes and toxicity.

The trial enrolled adult patients of both sexes, aged 55 to 75 years, who were in first complete remission of B-precursor ALL that was Philadelphia‑negative and CD19‑positive, with molecular failure defined as a minimal residual disease level of 10⁻⁴ or greater after induction II of front‑line therapy. Participants were required to have an ECOG performance status below 2, left ventricular ejection fraction greater than 30 % on cardiac ultrasound, renal clearance of at least 30 mL/min, and hepatic enzymes within specified limits; they also needed to test negative for HIV, hepatitis B and C, HTLV‑1/2, and syphilis, and to meet defined pancreatic and contraceptive criteria. Enrollment was limited to individuals who could provide written informed consent and who were registered with the German Multicenter Study Group for Adult ALL, with molecular markers for MRD assessment confirmed by a central reference laboratory. No specific dietary, physical activity, or habit restrictions were stipulated in the inclusion criteria. The sponsor did not provide information on the total number of participants enrolled.

The study is an open‑label, multicenter, phase II investigation of Obe‑cel (autologous enriched T cells retrovirally transduced to express two chimeric antigen receptors targeting CD19 and CD22) administered as a single intravenous infusion at a dose of 3.1 × 10⁸ cells in patients with Philadelphia‑negative B‑precursor acute lymphoblastic leukaemia who have minimal residual disease (MRD) ≥10⁻⁴ after induction II. The trial is not randomized or blinded. Recruitment is planned to begin on 1 July 2026 and to continue until 1 October 2032, with each participant followed for up to 24 months after infusion. The visit schedule includes a screening visit for eligibility verification, MRD assessment, cardiac, hepatic, renal and infectious disease testing; a baseline visit for lymphodepleting chemotherapy; the infusion visit (day 0); follow‑up visits on day 28, month 3, month 6, month 12, month 18 and month 24, culminating in an end‑of‑study visit at month 24. Primary efficacy is the probability of event‑free survival at 12 months, defined as absence of death in remission, molecular or morphological relapse, secondary malignancy, or initiation of new anti‑ALL therapy. Secondary assessments include MRD response rates, relapse‑free survival, overall survival, adverse event incidence (including CRS and ICANS), immunoglobulin levels, and need for allogeneic stem‑cell transplantation. Participants are expected to remain in the study for the full 24‑month period unless early termination occurs, which may be triggered by withdrawal of consent, unacceptable toxicity, disease progression, failure to meet lymphodepletion criteria, or investigator‑determined inability to continue safely.

The investigational product designated AUTO1 consists of autologous enriched T cells retrovirally transduced to express two chimeric antigen receptors targeting CD19 and CD22. The cellular therapy is supplied as an infusion for intravenous administration. Each dose contains 310,000,000 transduced T cells and is delivered as a single intravenous infusion; no repeated dosing schedule is specified.

Administration of AUTO1 is performed under controlled clinical conditions with continuous monitoring of vital signs during the infusion and observation for immediate adverse events thereafter. Post‑infusion assessments, including laboratory evaluations and safety monitoring, are conducted according to the study protocol to ensure adherence to the dosing regimen and to document participant compliance.

The primary efficacy assessment is the probability of event‑free survival at 12 months after infusion of the investigational product. An event is defined as death while in complete remission, molecular relapse, morphological relapse, development of a secondary malignancy, or initiation of any new anti‑B‑ALL therapy, including allogeneic stem‑cell transplantation.

Secondary efficacy parameters include:

• MRD complete response rate (incidence of MRD negativity) at month 3 post‑infusion, confirmed by quantitative evaluation of clonal IG or TR gene rearrangements with a sensitivity of at least 10⁻⁴.
• Incidence of MRD response at 28 days after infusion, expressed as the proportion of evaluable patients.
• Duration of MRD response, defined as the interval from the first documented MRD response to the last confirmed continuous response or loss of response.
• Relapse‑free survival, measured from infusion to morphological relapse or death of any cause, censored at last follow‑up or at allogeneic stem‑cell transplantation.
• Median time to molecular or hematologic relapse.
• Probability of continuous complete remission at 12, 18, and 24 months.
• Probability of overall survival at 12, 18, and 24 months.
• Probability of event‑free survival at 12, 18, and 24 months.

MRD assessments are performed using validated quantitative polymerase chain reaction assays targeting immunoglobulin or T‑cell receptor gene rearrangements, with a detection threshold of 10⁻⁴. Bone‑marrow samples are examined for morphological relapse, defined by >5 % abnormal lymphoblasts, or for new unequivocal central‑nervous‑system or extramedullary disease. Additional laboratory evaluations include quantification of immunoglobulins, the infused CAR‑T cells, and B‑cell subsets at scheduled visits corresponding to the efficacy timepoints.