Identification of N-Methyl Nicotinamide and N-Methyl Pyridazine-3-Carboxamide Pseudokinase Domain Ligands as Highly Selective Allosteric Inhibitors of Tyrosine Kinase 2 (TYK2)

Abstract

As a member of the Janus (JAK) family of nonreceptor tyrosine kinases, TYK2 plays an important role in mediating the signaling of pro-inflammatory cytokines including IL-12, IL-23, and type 1 interferons. The nicotinamide 4, identified by a SPA-based high-throughput screen targeting the TYK2 pseudokinase domain, potently inhibits IL-23 and IFNα signaling in cellular assays. The described work details the optimization of this poorly selective hit (4) to potent and selective molecules such as 47 and 48. The discoveries described herein were critical to the eventual identification of the clinical TYK2 JH2 inhibitor (see following report in this issue). Compound 48 provided robust inhibition in a mouse IL-12-induced IFNγ pharmacodynamic model as well as efficacy in an IL-23 and IL-12-dependent mouse colitis model. These results demonstrate the ability of TYK2 JH2 domain binders to provide a highly selective alternative to conventional TYK2 orthosteric inhibitors.

Preclinical evaluation of tyrosine kinase 2 inhibitors for human beta‐cell protection in type 1 diabetes

“…Both inhibitors bind to the JH2 pseudokinase domain of TYK2 and act as allosteric inhibitors of the kinase activity of the enzyme. The JH2‐directed allosteric inhibition also provides the high specificity for TYK2 over other JAK family members 16 . Summarized information on the two TYK2 inhibitors presently used is provided in Table S2.…”

New Promise and Opportunities for Allosteric Kinase Inhibitors

“…Notably, the amide D 3methyl group is located in a unique small lipophilic pocket formed by Lys 642 and the nonconserved Ala671, which contributes to target selectivity over the JH1 domain and the kinome. [49] Further systematic structure-based optimization of 23 yielded the clinical candiate BMS-986165 (24) with potent in vitro and in vivo activity, ideal PK properties in mouse, dog, and monkey, and an excellent safety profile. More importantly, 24 displays extraordinary target specificity over the JH1 domains of TYK2, JAK1, JAK2, and JAK3 (IC 50 > 10 uM) and the remainder of the human kinome.…”

Allosterische Kinaseinhibitoren – Erwartungen und Chancen

“…B. 20 – 24 von Bristol‐Myers Squibb (Abbildung ) . Diese können selektiv und direkt an die JH2‐Domäne binden und hemmen die TYK2‐Kinasefunktion durch einen allosterischen Mechanismus (hier definiert als Typ‐VI‐Binder), während sie keine offensichtlichen Auswirkungen auf die enzymatische Aktivität der JH1‐Domäne haben.…”