biostudies-literatureUnknownKrawczyk MEuropean Research CouncilNHLBI NIH HHSCD19-CAR-T-cells emerge as a major therapeutic option for relapsed/refractory B-cell-derived malignancies, however approximately half of patients eventually relapse. To identify resistance-driving factors, we repeatedly exposed B-cell lymphoma/B-cell acute lymphoblastic leukemia to 4-1BB/CD28-based CD19-CAR-T-cells <i>in vitro</i>. Generated models revealed costimulatory domain-dependent differences in CD19 loss. While CD19-4-1BB-CAR-T-cells induced combination epitope/total CD19 protein loss, CD19-CD28-CAR-T-cells did not drive antigen-escape. Consistent with observations in patients relapsing after CD19-4-1BB-CAR-T-cells, we identified CD19 frameshift/missense mutations affecting residues critical for FMC63 epitope recognition. Mathematical simulations revealed that differences between CbioRxiv : the preprint server for biology2025.02.28.640707https://www.ebi.ac.uk/biostudies/studies/S-EPMC11908201biostudies-literatureThe costimulatory domain influences CD19 CAR-T cell resistance development in B-cell malignancies.PMC11908201T32 HL007150805038Winiarski TKrawczyk MWalchli SBenard EPepek MFernandez-Fuentes NDavis JThomas-Tikhonenko AGraczyk-Jarzynka AMenendez PPuente XSFidyt KBousquets-Munoz PWiniarska MfalseThe costimulatory domain influences CD19 CAR-T cell resistance development in B-cell malignancies.CD19-CAR-T-cells emerge as a major therapeutic option for relapsed/refractory B-cell-derived malignancies, however approximately half of patients eventually relapse. To identify resistance-driving factors, we repeatedly exposed B-cell lymphoma/B-cell acute lymphoblastic leukemia to 4-1BB/CD28-based CD19-CAR-T-cells <i>in vitro</i>. Generated models revealed costimulatory domain-dependent differences in CD19 loss. While CD19-4-1BB-CAR-T-cells induced combination epitope/total CD19 protein loss, CD19-CD28-CAR-T-cells did not drive antigen-escape. Consistent with observations in patients relapsing after CD19-4-1BB-CAR-T-cells, we identified CD19 frameshift/missense mutations affecting residues critical for FMC63 epitope recognition. Mathematical simulations revealed that differences between C2025-01-01T00:00:00Z2025 Mar2026-04-08T19:50:51.711Z2025-04-05T22:10:32.42ZS-EPMC119082014009309610.1101/2025.02.28.640707