AS1842856: A dual FOXO1-GSK3 inhibitor for targeting B-ALL-specific molecular vulnerabilities

Activation of the transcription factor FOXO1 contributes to multiple pathological processes. The FOXO1 inhibitor AS1842856 demonstrated strong therapeutic effects in pre-clinical models of common diseases like diabetes and anthracyclines-induced heart failure. We have previously identified FOXO1 as a B-ALL dependency and demonstrated in in vivo B-ALL models that AS1842856 increased the survival and decreased B-ALL tumor load in all critical organ compartments, but most efficiently in the CNS. Here, we interrogated the underlying molecular mechanisms by comparison of the transcriptomic effects of AS1842856 and Foxo1-KO in a B-ALL mouse model. Despite the significant similarity in sets of regulated genes, we identified GSK3B inhibition as a signature enriched only in AS1842856-treated cells. Using an in vitro kinase assay, we identified AS1842856 as a direct GSK3B inhibitor that ultimately stabilizes CTNNB1. CTNNB1-KO partially protected B-ALL cell lines from the cytotoxic effect of AS1842856. At the same time, using a chemical protein degradation model, we found that FOXO1 indeed contributes to the cytotoxic effect of AS1842856. We conclude that AS1842856 targets two known B-ALL vulnerabilities: GSK3B and FOXO1. The unique mode of action, low toxicity, and ability to penetrate the blood-brain barrier warrant further investigation of the therapeutic potential of AS1842856 in B-ALL. RNA-sequencing was performed in BCR-ABL1+ Cre-ERT2 Foxo1fl/fl murine B-ALL cells treated with 200 nM 4-OHT or equivalent amount of vehicle EtOH or with 70 nM AS1842856 or equivalent amounts of DMSO vehicle. RNA was isolated after 24 hours and 48 hours.