[Clinical analysis of long-term survival and influencing factors of chimeric antigen receptor T-cell therapy in relapsed/refractory acute B-cell lymphoblastic leukemia]

Objective: To analyze the survival and influencing factors of chimeric antigen receptor (CAR) T-cell therapy in relapsed/refractory acute B-cell lymphoblastic leukemia (R/R B-ALL) . Methods: Clinical information of patients who received CAR-T-cell therapy and achieved complete remission of R/R B-ALL between May 2015 and June 2018 at the Shaanxi Provincial People's Hospital was obtained. Kaplan-Meier analysis was used to evaluate the overall survival (OS) and leukemia-free survival (LFS) times of patients, and Cox regression analysis was performed to analyze the prognostic factors that affect patient survival after CAR-T therapy. Results: Among the 38 patients with R/R B-ALL, 21 were men, with a median age of 25 (6-59) years and a median OS time of 18 (95% CI 3-33) months. Multivariate Cox regression analysis showed that positive MLL-AF4 fusion gene expression was an independent risk factor for OS and LFS (OS: HR=4.888, 95% CI 1.375-17.374, P=0.014; LFS: HR=6.683, 95% CI 1.815-24.608, P=0.004). Maintenance therapy was a protective factor for OS and LFS (OS: HR=0.153, 95% CI 0.054-0.432, P<0.001; LFS: HR=0.138, 95% CI 0.050-0.382, P<0.001). In patients with MRD negative conversion, LFS benefit (HR=0.209, 95% CI 0.055-0.797, P=0.022) and OS difference was statistically insignificant (P=0.111). Moreover, patients with high tumor burden were risk factors for OS and LFS at the level of 0.1 (OS: HR=2.662, 95% CI 0.987-7.184, P=0.053; LFS: HR=2.452, 95% CI 0.949-6.339, P=0.064) . Conclusion: High tumor burden and high-risk genetics may affect the long-term survival rate of patients with R/R B-ALL receiving CAR-T, and lenalidomide-based maintenance therapy may improve their prognosis.

C3aR costimulation enhances the antitumor efficacy of CAR-T cell therapy through Th17 expansion and memory T cell induction

Although chimeric antigen receptor (CAR)-modified adoptive T cell therapy is a promising immunotherapy for hematological malignancies, the efficacy improvement in relapsed/refractory acute lymphoblastic leukemia (ALL) with extramedullary infiltration and in multiple myeloma (MM) is still warranted. Since C3aR activation can promote the expansion of tumor-killing Th17 cells, we hypothesized that incorporating C3aR as a costimulatory domain would augment the antitumor activity of CAR-T. In this study, we introduced the C3aR domain into a CAR and generated BB-ζ-C3aR CAR-T targeting CD19 or BCMA. These new CAR-T exhibited a potent cytolytic ability to eradicate tumor cells expressing CD19 or BCMA in vitro. When administered intravenously to ALL or MM xenograft mouse models, BB-ζ-C3aR CAR-T reduced the tumor burden and improved the survival rate. Of note, these CAR-T could effectively eradicate subcutaneous CD19⁺ tumor cells, highlighting the therapeutic potential in extramedullary leukemia. Mechanistically, BB-ζ-C3aR CAR-T tended to exhibit a Th17 phenotype favoring tumor killing and suppressed Tregs. In addition, the induction of memory T cell in the BB-ζ-C3aR CAR-T cells indicated their long-term effects. Together, our findings suggest that the application of C3aR costimulation boosts the ability of CAR-T to eradicate aggressive tumor cells via Th17 expansion and memory T cell induction.

Efficacy and safety of CD19 CAR T constructed with a new anti-CD19 chimeric antigen receptor in relapsed or refractory acute lymphoblastic leukemia

Background

Recent evidence suggests that resistance to CD19 chimeric antigen receptor (CAR)-modified T cell therapy may be due to the presence of CD19 isoforms that lose binding to the single-chain variable fragment (scFv) in current use. As such, further investigation of CARs recognize different epitopes of CD19 antigen may be necessary.

Methods

We generated a new CD19 CAR T (HI19α-4-1BB-ζ CAR T, or CNCT19) that includes an scFv that interacts with an epitope of the human CD19 antigen that can be distinguished from that recognized by the current FMC63 clone. A pilot study was undertaken to assess the safety and feasibility of CNCT19-based therapy in both pediatric and adult patients with relapsed/refractory acute lymphoblastic leukemia (R/R B-ALL).

Results

Data from our study suggested that 90% of the 20 patients treated with infusions of CNCT19 cells reached complete remission or complete remission with incomplete count recovery (CR/CRi) within 28 days. The CR/CRi rate was 82% when we took into account the fully enrolled 22 patients in an intention-to-treat analysis. Of note, extramedullary leukemia disease of two relapsed patients disappeared completely after CNCT19 cell infusion. After a median follow-up of 10.09 months (range, 0.49–24.02 months), the median overall survival and relapse-free survival for the 20 patients treated with CNCT19 cells was 12.91 months (95% confidence interval [CI], 7.74–18.08 months) and 6.93 months (95% CI, 3.13–10.73 months), respectively. Differences with respect to immune profiles associated with a long-term response following CAR T cell therapy were also addressed. Our results revealed that a relatively low percentage of CD8⁺ naïve T cells was an independent factor associated with a shorter period of relapse-free survival (p = 0.012, 95% CI, 0.017–0.601).

Conclusions

The results presented in this study indicate that CNCT19 cells have potent anti-leukemic activities in patients with R/R B-ALL. Furthermore, our findings suggest that the percentage of CD8⁺ naïve T cells may be a useful biomarker to predict the long-term prognosis for patients undergoing CAR T cell therapy.

Trial registration

ClinicalTrials.gov: NCT02975687; registered 29 November, 2016. https://clinicaltrials.gov/ct2/keydates/NCT02975687