(A) Western blots for MALT1 targets Roquin, CYLD, and uncleaved BCL10 in PDX specimens were used to establish the MALT1 activation state in each specimen. (B) Cell counts relative to vehicle-treated cells for the indicated DLBCL PDX specimens ex vivo. Four different concentrations of compound 3 were assayed. Data represent the mean ± SD of 1 representative experiment. Each experiment was performed at least twice with similar results. (C) CFSE dilution assay results for 2 different concentrations of compound 3 in the indicated PDX specimens. (D) CFSE MFI FC relative to the mean of the vehicle-treated cells. (E) hIL-10 levels in the supernatant of PDX ex vivo culture. Data represent the mean ± SEM of 1 representative experiment performed in quadruplicate. **P ≤ 0.01, ***P < 0.001, and ****P < 0.0001, by ANOVA with Dunnett’s multiple comparisons adjustment (B and D) and unpaired, 2-tailed Student’s t test (E).