Improving the Oral Bioavailability and In vivo Efficacy of a Novel TAK1 Inhibitor Targeting Rheumatoid Arthritis

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Project Summary / Abstract Rheumatoid arthritis (RA) is a chronic inflammatory disease in which hyperactivated immune cells induce maladaptive persistent inflammation in the joints, leading to synovial inflammation and bone remodeling. In the US, RA currently affects roughly 1% of the population and carries a total annual societal cost burden of approximately $39.2 billion. In RA, sustained elevations of pro-inflammatory cytokines elicit chronic tissue damage and pain, which ultimately leads to loss of mobility and significant impairment of the patient’s lifestyle. Tumor necrosis factor (TNF) has been shown to play an important role in RA pathogenesis and pro-inflammatory signaling, and various TNF-sequestering antibodies (e.g., Remicade® and Enbrel®) are indicated for this disease. However, up to 40% of patients fail to respond to these therapies, treatments are burdened with high administration costs and noncompliance rates, and almost all carry serious safety issues, leading to a large need for an orally bioavailable alternative with a novel MOA which can reduce the intracellular effects of TNF and mitigate RA symptoms and damage. A key signaling element in the mediated TNF pro-survival/inflammatory response pathway is the protein kinase TAK1 (TGFβ activated protein kinase). TAK1 plays a crucial role in facilitating activation of protein kinase-mediated signaling pathways implicated in the pathogenesis of inflammatory and oncogenic processes. Because of its critical role in these pathways, TAK1 has emerged as a potential therapeutic target for the treatment of various inflammatory-mediated diseases including RA. Our recent discovery of the takinib scaffold has identified a highly specific potent inhibitor of TAK1 (IC50 ~9nM), and promising results from preliminary efficacy studies have supported targeted inhibition of TAK1 as a valid approach to regulating TNF production and signaling. Additionally, since the role of TAK1 appears to be largely confined to mediating TNF signaling, such an orally bioavailable drug would potentially have limited side effects, in contrast to alternative therapeutics including conventional DMARDs, biologics, and the cutting edge JAK/STAT inhibitors (e.g., tofacitinib). In order to successfully attain proof-of-concept for takinib, the project includes two Specific Aims: Aim 1 (Achieve Oral Bioavailability): Based on the co-crystal structure of takinib, develop a new series of analogs that retain selectivity towards TAK1 in vitro, and are orally bioavailable in normal rats. Milestone – Identify at least 3 selective analogs that exhibit significant oral bioavailability in serum. Aim 2 (Efficacy vs Enbrel®): Evaluate the anti-inflammatory response conferred by prioritized lead molecules in the collagen induced arthritis (CIA) mouse model of RA. Milestone – Demonstrate that the lead molecule exhibits equal or better efficacy than Enbrel® in the CIA mouse model. Achieving the Specific Aims above will provide for an orally bioavailable, first-in-class TAK1 inhibitor lead compound as an alternative to TNF-targeting biologics and JAK/STAT inhibitors for treating RA. Completion of these studies will provide the necessary data for us to pursue a Phase II NIH SBIR application to fund IND-enabling safety studies en route to a Phase I clinical trial.