A Novel Generation of Anti-CD7 Universal CAR-T Therapy for Patients with Relapsed or Refractory CD7 Positive T-ALL/Lbl: A Phase I Clinical Trial

Background: Clinical studies using CD7-targeting CAR-T cells, derived from autologous T cells or HSCT donor T cells, have shown anti-leukemic activity but was challenged by high production cost and potential product contaminations. Previously, we developed CD7-targeting “off-the-shelf” universal CAR-T cells (RD13-01) with T cell receptor (TCR), CD7, and human leukocyte antigen (HLA) class II knockout (KO) to reduce GvHD and prevent fratricide and allo-rejection. Additionally, an NK inhibitory (NKi) molecule was included to prevent host NK cell cytotoxicity[Hu et al., Cell Ressearch 2022]. These allogeneic CAR-T cells exhibited robust tumor control and expansion in patients (pts). However, we identified host CD7^- CD8⁺ T cells that mediated allo-rejection of universal CAR-T cells during the treatment. To address this, we engineered two inhibitory receptors (i1, i2) to resist rejection mediated by host NK and T cells. These modified cells are designated as RD13-02. This study investigated the safety and efficacy of RD13-02 in a phase I clinical trial (NCT05716113) involving R/R T-ALL/LBL pts.

Method: Pts diagnosed with CD7⁺ R/R T-ALL/LBL were eligible and sequentially enrolled in a accelerated dose titration and “3+3” dose escalation study. Four dosing levels (DL-1: 0.5×10⁸ CAR⁺ T cells; DL1: 2×10⁸ CAR⁺ T cells; DL2: 4×10⁸ CAR⁺ T cells; DL3: 6×10⁸ CAR⁺ T cells) were categorized based on the total dose of RD13-02 administered. All pts received a standard lymphodepletion regimen consisting of fludarabine (30mg/m²/day) and cyclophosphamide (500mg/m²/day) for three consecutive days (day -5 to day -3) before CAR-T infusion (day 0). Disease assessment was assessed by Day28/M2/M3 bone marrow (BM) aspirate/biopsy, and PETCT, if applicable, per NCCN Guidelines for Acute Lymphoblastic Leukemia Version 1.2021 and Lugano 2014 criteria. After dose escalation, study would proceed to dose expansion.

Results: As of August 1, 2024, a total of 18 eligible pts with R/R T-ALL/LBL were enrolled (13 ALL, 5 LBL), with a median age of 33.5 years (range, 11 to 67). The median prior lines of therapy were 2 (range, 1 to 5), and 4 pts had prior allo-HSCT before enrollment. The median proportion of BM blasts was 71% (range: 6% to 90%) among 18 pts, with 9 (6 ALL, 3 LBL) showing extramedullary involvement. No dose-limiting toxicity (DLT) event or neurotoxicity was observed at all dose levels, with only one case of Gr1 GvHD occurring. Cytokine release syndrome (CRS) was manageable with the majority being mild (Gr1, n=10; Gr2, n=5; Gr3, n=3). Any-grade infections occurred in 13 (72%) pts (≥Gr3 in 2 [11%] pts). Due to the occurrence of Gr3 CRS in one pt each from DL2 and DL3 levels, investigators set the DL1 as expansion dose with a paramount focus on safety and efficacy. During the dose expansion, one pt died from tumor lysis syndrome on Day 20 post infusion.

At the initial 28-day assessment post-infusion, 14 out of 17 evaluable pts achieved CR/CRi. While by the 2^nd month post-infusion, two more pts reached CR/CRi, with CR/CRi rate of 94%(16/17). Among pts with CR/CRi, 100% achieved minimal residual disease (MRD) negative status by flow cytometry analysis. The median C_max of CAR-T cells in the peripheral blood was 1,863,601 copies/μg genomic DNA (range, 275,044 to 3,763,587) by qPCR, with the longest duration exceeding 90 days.

Conclusion: RD13-02, an "off-the-shelf" universal CAR-T product, showed a manageable safety profile and enhanced efficacy in treating R/R CD7⁺ T-ALL/LBL. Notably, 100% of CR/CRi pts achieved MRD-negative status, offering pts more prompt treatment options. Dose expansion is ongoing at DL1, and additional clinical and correlative analyses will be presented at the meeting.