Fig. 1: Evaluation of cytotoxicity by UCART123 against MOLM13 (AML cell line) expressing CD123 in vitro and in vivo.

a CAR construct containing a scFv derived from an anti-CD123 murine antibody linked to a CD8-derived hinge/transmembrane domain, as well as 4-1BB and CD3zeta signaling domains. The CAR is co-expressed with RQR8, an artificial cell surface protein containing two CD20 epitopes recognized by Rituximab. b CD123-negative cell line, Jurkat, and CD123-positive AML cell line, MOLM13, were co-cultured with UCART123 with indicated various E:T ratios for 24 h. UCART123 induced significant cell death in MOLM13 at all E:T ratios, but not in Jurkat cells. Each symbol represents independent experiments (n = 23) and bar represents the average with the SD. ****p < 0.0001 c IFN-γ levels in supernatants were measured after 24 h when UCART123 was co-cultured with MOLM13 and Jurkat cells. Each symbol represents independent experiments (n = 19) and bar represents the average with the SD. ****p < 0.0001. d NSG mice were injected with MOLM13 cells expressing luciferase (MOLM13) and were treated with UCART123 at different cell doses on day 7 post injection of MOLM13. Leukemia burden was monitored weekly with bioluminescence imaging (BLI) and survival was evaluated. Diagram created with biorender.com e Weekly tracking of leukemia burden by BLI. UCART123-treated mice efficiently eliminated leukemia (except one mouse in the cohort treated with the lowest dose of UCART123), n = 6. f UCART123-treated mice achieved significant longer survival compared to control (p = 0.0027 for each of the UCART123-treated cohorts compared to control, log-rank test). Each symbol represents one mouse. g MOLM13 engrafted mice were treated with PBS, UCART123, or UCART123 followed by rituximab (RTX). Representative BLI images at pre-treatment, day 28 and day 42 measured are shown for each group. h top, Frequencies of UCART123 (%) in mononuclear cells in peripheral blood on day 23 post UCART123 treatment were measured with flow cytometry. Each symbol represents one mouse and bar represents the average with the SD. ****p < 0.0001, one-way ANOVA. bottom, Average radiance measured with BLI on day 28 and day 42 are shown, Each symbol represents a mouse in the cohort (UCART123/vehicle n = 10; UCART123/RTX n = 8) and the bar represents the average with the SD. ***p < 0.001, Mann–Whitney test. Source data are provided as a Source Data file.