Introduction: Prolonged grade 3-4 (G3-4) cytopenias lasting beyond day 30 have been observed with various chimeric antigen receptor (CAR) T-cell products. Their biologic mechanism remains largely unknown, since it is unclear whether it is related to the effects of the conditioning regimen or due to CAR T-cell activity.

Methods: We measured 29 analytes associated with CAR-T cell activity by multiplex assays (V-Plex, Meso Scale Diagnostics) and CAR T-cell amplification by RT-PCR in serial plasma samples at baseline and days 7, 14, and 30 (D30) after standard-of-care axicabtagene ciloleucel (axi-cel) in patients with refractory large B-cell lymphoma (LBCL) treated at MD Anderson Cancer Center between March and August 2018. Patients with G3-4 cytopenia before conditioning, defined according to CTCAE v5, and those who progressed and/or died before D30 were excluded from the analysis. Unpaired t-test was used for area under the curve (AUC) and mean peak comparison, and the Benjamini-Hochberg method for adjustment of false discovery rate (FDR).

Results: Of 19 patients included in the analysis, 9 (47%) had ongoing G3-4 cytopenia at D30. Baseline clinical characteristics were not significantly different between the 2 groups. Patients with D30 G3-4 cytopenia had a significantly higher AUC for the following cytokine levels: IFN-ɣ, FLT3-L, G-CSF, GM-CSF, CXCL1, IL-1Rα, IL-3, IL-8, IL-10, M-CSF, CCL2 (p<0.05); IL-1β, IL-2Rα, IL-6, IL-15, TNF-α (p<0.01); and VWF (p<0.001). In contrast, a significantly lower AUC was observed for Ang-1 (p=0.0002) and EGF (p=0.05). After adjusting for FDR, the association was maintained only for the following cytokines: Ang-1, IL-10, IL-15, IL-1β, IL-2Rα, IL-6, IL-8, TNF-α, and VWF. As the majority of cytokines outlined above showed a peak at day 7, the association between day 7 peak and D30 G3-4 cytopenia was evaluated. Patients with D30 G3-4 cytopenia showed a significantly higher peak at day 7 for the following cytokines: IFN-ɣ, G-CSF, GM-CSF, CXCL1, IL-1β, IL-2Rα, IL-3, IL-6, IL-8, IL-10, M-CSF, CCL2 (p<0.05), and FLT3-L (p<0.001), and a significantly lower peak for EGF (p=0.005). After adjusting for FDR, the only cytokine maintaining its association was FLT3-L. Patients with D30 G3-4 cytopenia had a significantly higher AUC for CAR T-cell amplification (123794 vs. 71548 DNA copies/µg), though not statistically significant because of small sample size (p=0.57).

Conclusions: Development of prolonged cytopenia after axi-cel in patients with LBCL is associated with significant increase in the levels of multiple inflammatory cytokines and with CAR T-cell amplification early after infusion, suggesting this is due to CAR T-cell activity rather than to the myelosuppressive effect of conditioning regimen. The majority of these cytokines appear to be derived from myeloid cells and peak at day 7, providing potential targets for prophylactic intervention in these patients.

Citation Format: Paolo Strati, Nahum Puebla-Osorio, Guangchun Han, Jason R. Westin, Loretta J. Nastoupil, Sairah Ahmed, Felipe Samaniego, Nathan H. Fowler, Luis E. Fayad, Hun J. Lee, Christopher R. Flowers, Samer A. Srour, Grace Watson, Linghua Wang, Michael R. Green, Sattva S. Neelapu. Association between cytokine levels and prolonged cytopenia after axicabtagene ciloleucel in patients with refractory large B-cell lymphoma [abstract]. In: Proceedings of the AACR Virtual Meeting: Advances in Malignant Lymphoma; 2020 Aug 17-19. Philadelphia (PA): AACR; Blood Cancer Discov 2020;1(3_Suppl):Abstract nr PO-57.