Highly Selective and Reversible STAT6 Inhibition Demonstrates Potential for Differentiated Efficacy and Safety Profile in Type 2 Allergic Inflammation

Abstract RATIONALE: Biologics targeting IL-4 and IL-13 immunology have achieved clinically meaningful efficacy in type 2 (allergic) inflammatory and pruritic diseases. Binding of IL-4 or IL-13 to their cognate receptors triggers the intracellular JAK-STAT signaling cascade to propagate their inflammatory responses. However, the clinical utility of small molecule JAK inhibitors is confounded by their associated on-target safety signals, including dysregulated hematologic homeostasis (anemia, thrombocytopenia). Selective STAT6 inhibition therefore represents an opportunity to match or exceed the biologic efficacy of anti-IL-4Rα/IL-13 monoclonal antibodies, while avoiding broad JAK-mediated immune suppression. METHODS: The SH2 domain exclusively mediates STAT6 binding to the IL-4/13 cytokine receptors and triggers downstream transcriptional activity, thereby representing an attractive therapeutic target. Recludix has developed an innovative and proprietary SH2 domain platform that has enabled the discovery of a new class of small molecule inhibitors of these previously undruggable protein domains. RESULTS: We describe for the first time a reversible, SH2 domain-targeting STAT6 inhibitor that demonstrates sub-nanomolar potency in biochemical and primary human cellular assays, high selectivity across the SH2 family, including other STAT proteins, and inhibits IL-4/13 driven inflammation. We show that unlike JAK inhibitors, reversible and selective STAT6 inhibition does not impair growth factor signaling critical for hematologic homeostasis. Preclinical studies reveal suppression of phosphorylated STAT activity (pSTAT6) in blood, spleen and lung with repeat dosing without any impact on total STAT6 protein levels. In a preclinical model of allergic asthma, blocking STAT6 activation with a reversible, non-degrading inhibitor attenuated lung inflammation with efficacy comparable to antibody-mediated blockade of anti-IL-4/13 pathways. CONCLUSION: Selective, reversible STAT6 inhibition brings the promise of combining the efficacy of clinically validated biologics with the convenience of oral administration, while potentially avoiding known safety concerns observed with the broader activity of JAK inhibitors.