Targeting of IRAK4 and GSPT1 enhances therapeutic efficacy in AML via c-Myc destabilization
IRAK4 is a therapeutic target in myeloid malignancies, but current IRAK4 inhibitors show only modest clinical efficacy in acute myeloid leukemia (1), highlighting the need for combination strategies. To identify drugs with synergistic potential alongside IRAK4 inhibitors, we conducted a high-throughput screen of 2,803 investigational and approved drugs in isogenic IRAK4-deficient and wild-type human AML cells. The top hit from this screen was the Cereblon E3 ligase modulator (CELMoD) CC-885. Validation in vitro and in vivo confirmed that CC-885 and related CELMoDs synergize with IRAK4 inhibitors to suppress leukemic cells. Among CC-885 substrates, GSPT1 loss showed the most pronounced effects in IRAK4-inhibited leukemic cells. Transcriptional and proteomic analyses revealed that CC-885 treatment led to c-Myc suppression in IRAK4-deficient leukemic cells. GSPT1 loss reduces translation efficiency, particularly for proteins with short half-lives, such as c-Myc. Accelerated c-Myc protein loss was confirmed following GSPT1 degradation in leukemic cells, with decreased protein stability observed following inhibition of IRAK4. These effects were validated in AML patient cells, supporting the potential of IRAK4 inhibitors to modulate c-Myc activity and enhance combinatorial therapies. This study demonstrates that IRAK4 is a therapeutic target in AML, and that combination therapies, such as with certain GSPT1-targeting CELMoDs, will be necessary to achieve maximal clinical responses. Overall design: Bulk RNAseq profiling of THP1 cells with electroporation with or without CAS9 and sgRNA targeting IRAK4 and grown through single cell cloning, treated with the CELMoD CC-885 at 50nM or equivalent amount of DMSO for 12 hours.