Hematologic toxicity after 5F11-Ts. (A) Patient 15 in cohort 1 experienced expected acute thrombocytopenia after CAR T-cell infusion, with initial partial recovery by day +10. He then experienced an abrupt decrease in platelet count on day +14, followed by progressive pancytopenia. (B) His absolute neutrophil count (ANC) was 0 (103/μL) on day +40. His ANC values were <0.2 (103/μL) on days +43 to +44, as denoted by the asterisk. He required platelet transfusions and growth factor support with filgrastim until day +58 and day +70, respectively. (C) Patient 18 in cohort 1 had elevated platelets of 467 (103/μL) before conditioning chemotherapy. Her platelet count decreased to 31 (103/μL) on day +10. (D) Patient 18 experienced an expected acute neutrophil decrease, with ANC <0.2 (103/μL) on days +3 to +6, as indicated by the asterisk. After initial recovery with growth factor support with filgrastim and pegfilgrastim, her ANC again decreased to values of ≤0.5 (103/μL) on days +32 to +72, as denoted by the line of asterisks, and with values of ≤0.2 (103/μL) on days +40 to +70. (E) The baseline BM biopsy for patient 15 is shown. H&E staining at 20× original magnification shows mildly hypocellular marrow for age at 40% overall cellularity with trilineage hematopoiesis. (F) H&E staining at 20× original magnification of patient 15’s day +16 BM biopsy demonstrates markedly hypocellular marrow with <5% overall cellularity, trilineage hypoplasia, and fibrosis. (G) The baseline BM biopsy for patient 4 in cohort 1 is shown. H&E staining at 20× original magnification shows baseline hypocellularity and trilineage hypoplasia. (H) H&E staining at 20× magnification of patient 4’s day +18 BM biopsy demonstrates ongoing hypocellularity and hypoplasia, as well as fibrosis. (I) Kaplan-Meier curve showing cumulative incidence of hematologic recovery (TTHR) for patients who received 5F11-Ts compared with patients who received Hu19-CD828Z-Ts. Multivariable CPH regression, P = .0499.
