Synergistic effect of ibrutinib and CD19 CAR-T cells on Raji cells in vivo and in vitro.

Ibrutinib might improve the efficacy of anti-CD19 chimeric antigen receptor (CD19 CAR) T-cell therapy in chronic lymphocytic leukemia (CLL). We studied the possibility and mechanism of the synergistic effect of ibrutinib and CAR-T cells in other types of lymphoma. In this study, we selected the CD19 CAR-T cells of a patient with lymphoma who failed in his CD19 CAR-T-cell therapy and a dose of 8 mg/kg/d ibrutinib. Subcutaneous and tail vein tumorigenic mice were established with Raji cells. The differences in the synergistic effect between these 2 models were compared by bioluminescence imaging (BLI) monitoring and flow cytometry (FCM). The expression of the STAT-3 signaling pathway was assessed by western blot analysis. There was no synergistic effect of ibrutinib and CD19 CAR-T cells in vitro. Programmed cell death-ligand 1 (PD-L1) was expressed in 0.23 ± 0.06% of Raji cells. In the subcutaneous tumorigenic model, the luciferase signal was reduced significantly in the group receiving ibrutinib combined with CD19 CAR-T cells. Moreover, the proportion of CD19 CAR-T cells was higher in the polytherapy group than in the CAR-T-cell monotherapy group. However, we did not get an analogous synergistic effect in the tail vein tumorigenic model. STAT-3 signaling pathway expression in the residual tumor cells did not differ between those with and those without ibrutinib, suggesting that the IL-10/STAT-3/PD-L1 pathway was not involved in the synergistic effect. Therefore, some other mechanism might be a target for ibrutinib. Our results provide evidence for the use of ibrutinib in polytherapy for other types of B-cell lymphoma.