Targeting canonical and non-canonical STAT3 signaling by WB737, a novel potent STAT3 inhibitor, in natural killer/T-cell lymphoma

Activating mutations of STAT3 were frequently found in patients with natural killer/T-cell lymphoma (NKTL), suggesting that targeted inhibition of STAT3 is a potential therapeutic option for NKTL patients. Here, we have developed a novel and potent STAT3 inhibitor WB737 that directly binds to the STAT3-SH2 domain with high affinity. WB737 selectively inhibits cell growth of NKTL harbored STAT3 mutations through inducing apoptosis and blocking colony formation. Mechanistically, WB737 inhibits both canonical and non-canonical STAT3 signaling via suppression of STAT3 phosphorylation at Tyr705 and Ser727 sites, respectively. Moreover, the activity of WB737 has a more potent inhibition on STAT3 compared to Sttatic, resulting in a significant anti-tumor effect followed by almost complete tumor regression in a NKTL xenograft model harboring STAT3 activating mutation. Collectively, these findings provide a preclinical proof-of-concept for WB737 as a novel therapeutic strategy for the treatment of NKTL patients with STAT3-activating mutations. RNA-seq for NKYS treated with DMSO or WB737 was performed (duplicate).