Inhibition of ITK and RLK Kinases with PRN694: A Promising Therapeutic Approach for T-Cell Mediated Diseases

The research focuses on the development of a novel inhibitor, PRN694, targeting the Tec family kinases ITK and RLK, which are pivotal in T and NK cell signaling. The study employs a combination of tailored covalency and structure-based design to develop selective inhibitors. PRN694 was identified through molecular modeling and optimization, demonstrating high selectivity and potency against ITK and RLK with IC50 values of 0.3 nM and 1.3 nM, respectively. The inhibitor's selectivity was validated in Jurkat T cells and was found to suppress TCR pathways, including NFAT1 and PLCγ1 activation. The specific interaction with ITK was confirmed through the use of a mutation that removed PRN694's binding site. PRN694 was also shown to prevent TCR-induced activation in cells expressing both ITK and RLK. In vitro assays confirmed PRN694's ability to inhibit TCR or FcR-induced activation in primary T or NK cells, T-cell proliferation, and pro-inflammatory cytokine release. In vivo assays revealed PRN694's durable pharmacodynamic effects on ITK with high occupancy percentages at various time points. The compound's therapeutic potential was examined in T-cell leukemias and T-cell driven inflammation, with effective blockade of TCR stimulation observed in HH cutaneous T-cell lymphoma and T-PLL cells, and significant inhibition of a DTH reaction in a cell-mediated immunity model. The study concludes that PRN694, a covalent ITK/RLK inhibitor, has potential therapeutic applications for T or NK cell-related diseases, including inflammation, autoimmune diseases, and malignancy. Disclosures include various affiliations and funding sources related to pharmaceutical companies and research institutions.