Potent and Selective Knockdown of Tyrosine Kinase 2 by Antisense Oligonucleotides

Tyrosine kinase 2 (TYK2) is a member of the JAK family of nonreceptor tyrosine kinase, together with JAK1, JAK2, and JAK3. JAKs are important signaling mediators of many proinflammatory cytokines and represent compelling pharmacological targets for autoimmune and inflammatory diseases. Pan-acting small-molecule JAK inhibitors were approved for the treatment of rheumatoid arthritis and ulcerative colitis. However, their limited selectivity among JAK members have led to undesirable side effects, driving a search toward specific JAK inhibitors. Recently, TYK2 has emerged as a target of choice for the treatment of autoimmune diseases and severe COVID-19 with an optimum balance between efficacy and safety, based on observations from human genetics studies and clinical outcomes of several agents targeting cytokine pathways for which TYK2 plays an essential role. In this article, we address selective targeting of TYK2 from the genetic sequence space through development of antisense oligonucleotides (ASOs) against TYK2 mRNA. Potent ASO candidates were identified from the screening of over 200 ASOs using locked nucleic acid gapmer design. The lead ASOs exhibited potent and selective knockdown of TYK2 mRNA and protein across a panel of model human cell lines in a dose-dependent manner, showing no reduction in the mRNA and protein expression levels of other JAK paralogs. In agreement with the depletion of TYK2 proteins, several TYK2-mediated cytokine signaling pathways, including IFN-α and IL-12, were inhibited upon ASO treatment. Our results established the TYK2 ASOs as investigational tool compound and potential therapeutic agent for the treatment of autoimmune diseases and severe COVID-19.