Determinants of peak axi-cel expansion. Peripheral blood mononuclear cells were collected at days 1, 8, and 15, and axi-cel copy number was measured by reverse transcription polymerase chain reaction and copies per μg DNA determined. Peak indicates the highest value identified in that patient. (A) Comparison of peak axi-cel copies per micrograms in peripheral blood between patients with NDR and those with a DR. (B) Comparison of peak axi-cel level between patients with a baseline high peripheral blood M-MDSC level (>250 cells per mL; n = 10) and a lower value (n = 9). (C) Volcano plot showing gene expression by NanoString in baseline tumor biopsy specimens collected within 1 month before axi-cel infusion. Comparison is shown between patients with an above-median peak axi-cel level (>2 × 10⁶ copies per μg; “good expansion”) and those with a lower peak (“poor expansion”). IFN signaling genes are shown as yellow squares; all other genes are shown as gray circles. (D) Comparison of peak axi-cel between patients with a very high baseline ferritin value (>1000 ng/mL; n = 10) and those with a lower value (<999 ng/mL; n = 41). (E) Comparison of baseline IL-6 levels in patients with above-overall median peak axi-cel level (>2 × 10⁶ copies per μg; n = 24) to those with a lower peak (n = 18). P values by nonparametric Mann-Whitney t tests.