Abstract
Background: Chimeric antigen receptor (CAR) T-cell therapy has proven to be a standard of care (SOC) for patients with relapsed/refractory B-cell lymphoma (R/R B-NHL).Nevertheless, a substantial subset of patients fails to achieve sustained remission with CD19-targeted CAR-T therapy. While CAR-T cell efficacy is known to be influenced by multifactorial determinants, the association between T-cell exhaustion markers (e.g., Programmed cell death protein 1[PD-1]) and clinical outcomes remains incompletely characterized in current studies.
Aims: We aimed to explore the correlation between the ratio of circulating PD-1+CAR-T cells to those in the infusion product and the efficacy of CAR-T cell therapy in R/R B-NHL.
Methods: From July 2022 to November 2024, 129 patients who received CD19 CAR T-cell therapy from Beijing GoBroad Hospital were enrolled.The median age was 52(23-75)years old.Diagnoses included DLBCL NOS (n=112), PMBCL(n=5) ,tFL(n=7), and BL (n=5). In the primary cohort, 114/129 (88.4%) patients were at stage III-IV at the time of salvage therapy. The median IPI score was 3 (range 2-5). 46/129 (35.7%) patients had central nervous system violations. 48/129(37.2%)patients had>7cm bulky disease and 14/129(10.9%)patients failure of prior autologous hematopoietic stem cell transplantation (HSCT).In order to further reduce the tumor burden, 61/129(47.3%) patients were treated with bridging therapy before CAR-T cell infusion.
Using spectral flow cytometry, we analyzed the CAR-T cell product and post-infusion samples collected on days 7, 14, and 28 from each patient, with specific focus on calculating the ratio of circulating PD-1+CAR-T cells to their counterparts in the infusion product (designated as the circulating-to-product [C/P] ratio).
The receiver operating characteristic (ROC) curve and area under the ROC curve (AUC) were used to compare the accuracy of each C/P ratio in predicting complete remission (CR) rate at 3 months. The value corresponding to the maximum Youden index was selected as the optimal cut-off value. The optimal cutoff values of C/P ratio at days 7, 14 and 28 after infusion were 2.049, 2.629 and 2.241, respectively.
The C/P ratio were transformed into binary predictors based on the optimal cut-off values, and univariate logistic regression analyses were performed to assess the association between C/P ratio predictors and the CR rate at 3 months. Survival curves were plotted using the Kaplan–Meier method to calculate the survival rate, and the log-rank test was carried out to compare the survival outcomes between groups.
Results There were 90/129(69.8%) patients achieve CR at 3 month after CAR T infusion.
The median follow-up time was 13.15 (range 10.92-18.97) months.The 2-year progression-free survival (PFS) was 71.57%(95% CI:62.57,78.77)and overall survival (OS) was 81.66%(95% CI:72.53,88.00)for the overall population, respectively.
We found that patients with C/P ratio higher than the optimal cutoff value had significantly improved PFS and OS.
At day 7 post-infusion, the high C/P ratio group showed superior PFS [2-year 76.62%(95% CI: 62.45-86.02) vs. 55.72%(95% CI:35.55-71.84); P=0.046] and OS [2-year 84.69%(95% CI: 70.26-92.48) vs. 68.49%(95% CI:47.35-82.57); P=0.035]. These benefits were further amplified by day 28, with the high C/P ratio group maintaining significantly better PFS[2-year 89.74%(95% CI: 74.94-96.02) vs. 71.25%(95% CI:51.88-83.94); P=0.044]and OS [2-year 97.14%(95% CI:81.40-99.59)vs.82.53%(95% CI:62.27-92.51); P=0.039], demonstrating the prognostic value of C/P ratio levels following CAR-T cell infusion.
The 2-year PFS was higher in high C/P ratio group [77.84%(95% CI: 64.87-86.50) vs. 67.15%(95% CI:50.52-79.27); P=0.282], and the 2-year OS was also higher in high C/P ratio group [83.44%(95% CI: 70.32-91.11)vs.81.93%(95% CI: 65.91-90.91); P=0.640]on days 14 after infusion. However, these differences were not statistically significant.
Conclusion: Our longitudinal analysis revealed that the circulating-to-product (C/P) ratio of PD-1+ CAR-T cells—calculated by comparing their frequency in peripheral blood at days 7 and 28 post-infusion to baseline levels in the manufactured product—served as a robust early predictor of durable disease control.A high PD-1+CAR-T C/P ratio strongly correlated with improved clinical outcomes such as response and progression-free survival.
