BTK Inhibitor Synergizes with CD19-Targeted Chimeric Antigen Receptor-T Cells in Patients with Relapsed or Refractory B-Cell Lymphoma: An Open-Label Pragmatic Clinical Trial
Authors: Luo Wenjing , Zhang Yinqiang , Li Chenggong , Xu Jia , Zhuolin Wu , Wang Xindi , Kang Yun , Liao Danying , Kou Haiming , Xie Wei , Xiong Wei , Deng Jun , Hu Yu , Mei Heng 
Published: December 2024

Background: Preclinical and clinical studies have demonstrated that ibrutinib could promote T and chimeric antigen receptor (CAR)-T cell proliferation, enrich less-differentiated phenotypes, downregulate the expression of exhaustion markers, and further improve CD19-targeted CAR-T cell (CART19) efficacy. Our previous study revealed that three Bruton tyrosine kinase inhibitors (BTKis), ibrutinib, zanubrutinib, and orelabrutinib, preserved CAR-T cell functionality and modulated tumor microenvironment in B-cell lymphoma (BCL). Here, we designed this open-label, non-randomized pragmatic clinical trial to prospectively investigate the synergism of BTKi and humanized CART19 in relapsed or refractory BCL (NCT05020392).

Methods: Eligible patients must age ≥18 and ≤70 years, and previous CAR-T cell therapy was not allowed. After screening, patients received BTKi selectively, which depends on both disease status and their own accord. Fludarabine-based lymphodepletion chemotherapy was followed by CART19 infusion. The primary end point was the safety. Cytokine release syndrome (CRS) and neurotoxicity were graded by the criteria of the ASTCT, and other adverse effects (AEs) were recorded and assessed according to the CTCAE 5.0. The secondary end points were clinical responses, which were evaluated per Lugano criteria. Other objectives included the pharmacokinetics of CAR-T cells and the phenotype of T cells.

Results: At data cutoff, 37 patients included were assigned to CAR-T cell monotherapy (n = 24) or combination therapy with BTKi (n = 13) , among who 3 patients received ibrutinib, 6 received zanubrutinib, and 4 received orelabrutinib. Median age was 57 (range, 24-69) years, and 73.0% of patients (27/37) were diagnosed with diffuse large B-cell lymphoma. The median prior lines of treatment were 3 (range, 2-9). Baseline characteristics were comparable between the two groups. Grade 1-2 and grade 3 cytokine release syndrome occurred in 43.2% and 2.7% of patients, respectively. One patient experienced grade 3 neurotoxicity. The most common severe AEs were hematological toxicities, including neutropenia (in 97.3% of patients), thrombocytopenia (in 40.5%), and anemia (in 43.2%). The adverse effects were comparable between the two groups. The best objective response rates were 84.6% vs 66.7% in patients with and without BTKi, and the best complete response (CR) rates were 61.5% vs 25.0%. The combination of BTKi significantly prolonged the overall survival (P = 0.029 ) but did not affect the progression-free survival (P = 0.21) or the duration of response (P = 0.53). CAR-T cells peaked at a median of 50 250 (range, 2 440-521 930) cells/mL by flow cytometry on day 14; CAR copies peaked at a median of 91 500 (range, 2 550-1 119 500) copies/μg DNA by droplet digital PCR on day 10. Peak expansion was not significantly associated with the combination of BTKi. Peripheral T cells from patients treated with BTKi were predisposed to early differentiation and less exhaustion 3 months after CAR-T cell infusion. One patient in the combination group started receiving ZB at 0.5 month prior to infusion and stoped at 4.4 months; the patient obtained a CR at 1 month and kept durable remission until 18 months after infusion. Single-cell RNA analysis of the patient indicated that T cells at relapse obtained a more dysfunctional immunotype, and monocytes/macrophages at relapse highly expressed M2-related genes.

Conclusion: Our study demonstrated that the combination of BTKi and CART19 induced good efficacy in terms of response depth and long-term survival. Prolonging the duration of BTKi maintenance might contribute to superior outcomes in patients with BCL through improving immune function.