Peripheral cytokine levels in patients with and without cytopenia treated with CAR-37 in comparison with CAR-19. (A) Serum protein levels were measured using the Luminex at the indicated time points. Circle size corresponds to the log₁₀ scaled concentration of the analyte in comparison with the minimum concentration (conc) of the analyte across patients. Circle color corresponds to the log₂ fold change of the analyte in comparison with the day 5 time point for each patient. (B-D) Banked serum samples from patients treated at our institution with a licensed CD19 CAR for lymphoma were analyzed using a custom kit measuring (B) IL-8, (C) IFN-γ, and (D) IL-18 on the Ella, bio-techne and were compared with serum samples from our CAR-37 patients measured with the same kit. Patients were classified as having prolonged cytopenia if they had an ANC <0.5 x10³ cells per μL blood at ≥28 days after CAR T-cell infusion. Patients were excluded if they had another cause of cytopenia, such as myelodysplasia or constitutional bone marrow failure. We compared CD19 CAR patients without cytopenia (n = 12) and cytopenia (n = 12) with CAR-37 patients without cytopenia (n = 1) and with cytopenia (n = 4). (E) IL-18 BP levels were measured on the Ella (Bio-Techne) for CAR-37 patients. Absolute values, AUC, and peak fold change from baseline are shown. (F) The ratio of IL-18 to IL-18 BP is shown over time after infusion. P values were calculated using a 1-way analysis of variance test with Tukey multiple comparisons test.