CC-401 Promotes β-Cell Replication via Pleiotropic Consequences of DYRK1A/B Inhibition

Pharmacologic expansion of endogenous beta cells is a promising therapeutic strategy for diabetes. To elucidate the molecular pathways that control beta-cell growthwe screened similar to 2400 bioactive compounds for rat beta-cell replication-modulating activity. Numerous hit compounds impaired or promoted rat beta-cell replication, including CC-401, an advanced clinical candidate previously characterized as a c-JunN-terminal kinase inhibitor. Surprisingly, CC-401 induced rodent (in vitro and in vivo) and human (in vitro) beta-cell replication via dual-specificity tyrosine phosphorylation-regulated kinase (DYRK) 1A and 1B inhibition. In contrast to rat beta cells, which were broadly growth responsive to compound treatment, human beta-cell replication was only consistently induced by DYRK1A/B inhibitors. This effect was enhanced by simultaneous glycogen synthase kinase-3 beta (GSK-3 beta) or activin A receptor type II-like kinase/transforming growth factor-beta (ALK5/TGF-beta) inhibition. Prior work emphasized DYRK1A/B inhibition-dependent activation of nuclear factor of activated T cells (NFAT) as the primary mechanism of human beta-cell-replication induction. However, inhibitionofNFATactivity hadlimited effectonCC-401-induced beta-cell replication. Consequently, we investigated additional effects of CC-401-dependent DYRK1A/B inhibition. Indeed, CC-401 inhibited DYRK1A-dependent phosphorylation/stabilization of the beta-cell-replication inhibitor p27Kip1. Additionally, CC-401 increased expression of numerous replication-promoting genes normally suppressed by the dimerization partner, RB-like, E2F and multivulval class B (DREAM) complex, which depends upon DYRK1A/B activity for integrity, including MYBL2 and FOXM1. In summary, we present a compendium of compounds as a valuable resource for manipulating the signaling pathways that control beta-cell replication and leverage a DYRK1A/B inhibitor (CC-401) to expand our understanding of themolecular pathways that control beta-cell growth.