Identification of highly selective SIK 1/2 inhibitors that modulate innate immune activation and suppress intestinal inflammation

The salt- inducible kinases (SIK) 1-3 are key regulators of pro- versus anti- inflammatory cytokine responses during innate immune activation. The lack of highly SIK- family or SIK isoform- selective inhibitors suitable for repeat, oral dosing has limited the study of the optimal SIK isoform selectivity profile for suppressing inflammation in vivo. To overcome this challenge, we devised a structure-based design strategy for developing potent SIK inhibitors that are highly selective against other kinases by engaging two differentiating features of the SIK catalytic site. This effort resulted in SIK1/2- selective probes that inhibit key intracellular proximal signaling events including reducing phos-phorylation of the SIK substrate cAMP response element binding protein (CREB) regulated transcription coactivator 3 (CRTC3) as detected with an internally generated phospho- Ser329- CRTC3- specific antibody. These inhibitors also suppress production of pro- inflammatory cytokines while inducing anti- inflammatory interleukin-10 in activated human and murine myeloid cells and in mice following a lipopolysaccharide challenge. Oral dosing of these compounds ameliorates disease in a murine colitis model. These findings define an approach to generate highly selective SIK1/2 inhibitors and establish that targeting these isoforms may be a useful strategy to suppress pathological inflammation.