Discovery of imidazo[1,2- b]pyridazine-containing TAK1 kinase inhibitors with excellent activities against multiple myeloma

Current treatment options for patients with multiple myeloma (MM) include Proteasome inhibitors, anti-CD38 Antibodies, and immunomodulatory agents. However, if patients have continued disease progression after administration of these treatments, there are limited options. There is a need for effective targeted therapies of MM. Recent studies have shown that the Transforming Growth Factor-β activated kinase (TAK1) is upregulated and overexpressed in MM. We have discovered that 6-substituted morpholine or piperazine imidazo[1,2-b]pyridazines, with an appropriate aryl substituent at position-3, inhibit TAK1 at nanomolar concentrations. The lead compound, 26, inhibits the enzymatic activity of TAK1 with an IC₅₀ of 55 nM. Under similar conditions, the known TAK1 inhibitor, takinib, inhibits the kinase with an IC₅₀ of 187 nM. Compound 26 and analogs thereof inhibit the growth of multiple myeloma cell lines MPC-11 and H929 with GI₅₀ values as low as 30 nM. These compounds have the potential to be translated into anti-MM therapeutics.