TYK2 is an emerging drug target for various human autoimmune diseases. However, discovery of selective TYK2 inhibitor over other JAK family members (i.e., JAK1, 2, 3) by targeting the catalytically active site (Janus Homologue 1 (JH1) domain) is challenging. This Viewpoint discusses the discovery of a series of N-methyl pyridazine-3-carboxamides as novel selective pseudokinase (JH2) domain binders of TYK2. A systematic structure-based optimization yielded a highly potent and selective allosteric TYK2 inhibitor candidate that is currently in phase III clinical trial for psoriasis.