Determinants of Response to Anti CD-19 CAR-T Cells for Diffuse Large B-Cell Lymphoma in Pre-Treatment Peripheral Blood Mononuclear Cells Using Single-Cell RNA-Seq

Background: Chimeric antigen receptor T (CAR-T) cell therapy has become the standard of care in patients with relapsed/refractory diffuse large cell lymphoma (R/R DLBCL), providing durable remission in 40% of patients. Lack of response is likely to be attributed to inter- and intra-patient variability, including PBMC heterogeneity and apheresis material composition, CAR-T infusion product, in-vivo expansion and activity of CAR-T cells and the development of tumor-intrinsic mechanisms. Current methods for evaluating CAR-T cell activation and potency have limited predictive value for clinical outcomes. To address this challenge, we performed single-cell RNA sequencing (scRNA-seq) of peripheral blood mononuclear cells (PBMCs) obtained from patients with R/R LBCL patients at the time of apheresis for the manufacturing of anti-CD19 CAR-T cell therapy. Methods: Between 10/2020 and 03/2022, 31 patients who underwent lymphopheresis were enrolled. Samples were obtained – 1) At day of lymphopheresis from peripheral blood; 2) On the day of infusion of CAR-T from the product; and 3) On day +7 after infusion from peripheral blood. All patients had day +30 PET-CT. In addition, PBMCs samples from healthy donors were used as control to analyze baseline characteristics compared to the DLBCL patients. PBMCs from patients of healthy donors were purified from frozen blood samples by density gradient separation, stained using human CD45 antibody and loaded onto a 10x Chromium system. libraries were generated using the 10X Genomics Chromium Single Cell 3' Kit. The data was processed and analyzed using the Seurat R package. The study was approved by the local Ethic committee. Results: Patient characteristics: 31 RR DLBCL patients (42% females; median age 72, range 47-81 years), all treated with CAR-T cells therapy as third line of therapy, participated in the study. All patients underwent lymphopheresis, followed by CAR-T production. Disease status at lymphodepletion was complete remission (CR, n=4, 13%), partial remission (n=6, 19%), and progressive disease (n=21, 68%) and patients received either tisagenlecleucel (n=20, 65%) or axicabtagene ciloleucel (n=11, 35%) . PET scan performed on day 30 post treatment revealed that 68% and 32% obtained CR, and PD, respectively. scRNA analysis revealed differences in PBMC composition between healthy donors and LBCL patients (Figure 1A), with lower levels of naïve and memory T cells and elevated levels of activated monocytes in LBCL patients, suggesting a shift towards an inflamed and pre-dysfunctional immune state. Categorization of LBCL patients into responders (PR/CR on day +30 PET-CT) and non-responders (PD on day +30 PET-CT) revealed differences in immune cell subsets between responders and non-responders (Figure 2A), with enriched inflammation-related pathways in non-responders, In contrast, responders exhibited a distinct healthy-like immune profiles, particularly high levels of naive T cells, similar to that obtained in their age matched healthy controls. Of note, non-responders showed alterations in immune cell subsets, including increased levels of T regulatory cells and effector NK cells. Furthermore, non-responders demonstrated a prominent inflammatory immune profile, characterized by gene pathways related to inflammation and activation, such as type I and III IFN-G, and TNFb response (Figure 1B). Notably, an IFN-G score was significantly higher in non-responder's monocytes subpopulations, compared to responders. Conclusions: These findings indicate that the success of CAR-T therapy could be determined by the molecular characteristics and subpopulation distribution of each patient’s PBMC. The diverse immune profiles of DLBCL patients might impact the effectiveness of their immune cells in generating successful CAR-T products or providing a conducive environment for CAR T cells to combat cancer. Furthermore, these findings emphasize the potential of scRNA-seq in evaluating PBMC from CAR-T patients prior to treatment, allowing the potential calculation of an "immune potency score" associated with the probability of a positive outcome from CAR-T treatment of DLBCL patients. This score could potentially be used by oncologists in decision-making processes to determine the appropriate candidates for CAR-T therapy.