Selectivity Profile of the Tyrosine Kinase 2 Inhibitor Deucravacitinib Compared with Janus Kinase 1/2/3 Inhibitors.

Deucravacitinib, a novel, oral, selective inhibitor of tyrosine kinase 2 (TYK2) signaling, acts via an allosteric mechanism by binding to the enzyme's regulatory domain instead of the catalytic domain. This unique binding provides high functional selectivity for TYK2 versus the closely related Janus kinases (JAKs) 1/2/3. Deucravacitinib was efficacious in phase 2 and 3 psoriasis trials, without clinical or laboratory parameters indicative of JAK 1/2/3 inhibition being observed. This analysis compared the kinase specificities of deucravacitinib versus JAK 1/2/3 inhibitors at therapeutic exposures. Signaling via JAK 1/3, JAK 2/2, and TYK2/JAK 2 dimers was measured in in vitro whole blood assays. Concentrations providing half-maximal inhibition (IC50) in these assays were determined for deucravacitinib and the JAK 1/2/3 inhibitors tofacitinib, upadacitinib, and baricitinib. Newly derived whole blood IC50 values were plotted against available pharmacokinetic profiles using doses evaluated in phase 2/3 trials. Simulated average daily inhibition and durations over which concentrations exceeded IC50 were evaluated. At clinically relevant exposures, projected steady-state deucravacitinib plasma concentrations were higher than TYK2 IC50 for approximately 9-18 h. Maximal plasma concentrations (Cmax) of deucravacitinib were 8- to 17-fold lower than JAK 1/3 IC50 and > 48- to > 102-fold lower than JAK 2/2 IC50. Simulated daily average TYK2 inhibition by deucravacitinib ranged from 50% to 69%. Simulations indicated that tofacitinib, upadacitinib, and baricitinib at steady state exhibited varying degrees of JAK 1/3 (daily average inhibition, 70-94%) and JAK 2/2 (23%-67%) inhibition at therapeutic concentrations, with Cmax values 17- to 33-fold lower than their TYK2 IC50 levels. At clinically relevant doses and exposures, deucravacitinib demonstrates highly selective inhibition of TYK2 and not JAK 1/2/3. Tofacitinib, upadacitinib, and baricitinib variably inhibit JAK 1/2/3 but not TYK2. These results indicate that deucravacitinib is a distinct class of kinase inhibitor compared with JAK 1/2/3 inhibitors.

Chimalakonda A ，Burke J ，Cheng L ，Catlett I ，Tagen M ，Zhao Q ，Patel A ，Shen J ，Girgis IG ，Banerjee S ，Throup J ... -  《-》

Nonclinical evaluations of deucravacitinib and Janus kinase inhibitors in homeostatic and inflammatory pathways.

Translational medicine provides insight into novel drugs and predicts unwanted effects. In well-characterized pathways (e.g., cytokine-Janus kinase [JAK]-signal transducers and activators of transcription [STAT]), a variety of in vitro assessments were used to estimate selectivity of effects on different potential targets (i.e., JAK1, JAK2, JAK3, and tyrosine kinase 2 [TYK2]). Several approved drugs were characterized as selective for the JAK family. These assessments are challenged by a lack of compounds that only inhibit one JAK family member. Deucravacitinib is a first-in-class, oral, selective, allosteric inhibitor of TYK2, a kinase required for IL-12, IL-23, and Type I interferon signaling. Unlike deucravacitinib, which selectively binds to the TYK2 regulatory domain, JAK1,2,3 inhibitors target the catalytic domain, contributing to nonselective targeting of JAK1,2,3. Cytokines associated with JAK1,2,3 signaling are required for both immune and nonimmune functions. A similar laboratory abnormality profile was observed in clinical trials using JAK1,2,3 inhibitors that has not been observed with deucravacitinib. In vitro testing of JAK1,2,3 inhibitors has relied upon assays of signal transduction, such as those measuring STAT phosphorylation, for estimates of potency and selectivity. These assay systems can be effective in estimating in vivo efficacy; however, they may not provide insight into downstream outcomes of receptor signaling, which may be more relevant for evaluating safety aspects. Assay systems assessing functional outcomes from cells may yield a more useful translational evaluation. Here, deucravacitinib was assessed for potency and selectivity versus three representatives of the JAK inhibitor class (tofacitinib, baricitinib, and upadacitinib) based on functional assays. JAK inhibitors had suppressive activity against JAK2-dependent hematopoietic colony-forming assays modeling thrombopoiesis, erythropoiesis, and myelopoiesis; however, deucravacitinib did not. Deucravacitinib had limited potency against NK cells, cytotoxic T cells, T-helper cells, and regulatory T cells activated by JAK1/JAK3-dependent common gamma chain cytokines. These data are consistent with the biologic role of JAK1,2,3 and pharmacodynamic changes in clinical laboratory abnormalities. Against TYK2-dependent cytokines, deucravacitinib selectively inhibited Type I interferon stimulation of monocytes and dendritic cells and was a more potent inhibitor than JAK inhibitors. IL-12 and IL-23 functional outputs were similarly potently inhibited by deucravacitinib. Results are consistent with deucravacitinib selectively inhibiting TYK2.

Johnson B ，Cheng L ，Koenitzer J ，Catlett IM ，Schafer P ... -  《Frontiers in Immunology》

Deucravacitinib is an allosteric TYK2 protein kinase inhibitor FDA-approved for the treatment of psoriasis.

Psoriasis is a heterogeneous, inflammatory, autoimmune skin disease that affects up to 2% of the world's population. There are many treatment modalities including topical medicines, ultraviolet light therapy, monoclonal antibodies, and several oral medications. Cytokines play a central role in the pathogenesis of this disorder including TNF-α, (tumor necrosis factor-α) IL-17A (interleukin-17A), IL-17F, IL-22, and IL-23. Cytokine signaling involves transduction mediated by the JAK-STAT pathway. There are four JAKS (JAK1/2/3 and TYK2) and six STATS (signal transducer and activators of transcription). Janus kinases contain an inactive JH2 domain that is aminoterminal to the active JH1 domain. Under basal conditions, the JH2 domain inhibits the activity of the JH1 domain. Deucravacitinib is an orally effective N-trideuteromethyl-pyridazine derivative that targets and stabilizes the TYK2 JH2 domain and thereby blocks TYK2 JH1 activity. Seven other JAK inhibitors, which target the JAK family JH1 domain, are prescribed for the treatment of neoplastic and other inflammatory diseases. The use of deuterium in the trimethylamide decreases the rate of demethylation and slows the production of a metabolite that is active against a variety of targets in addition to TYK2. A second unique aspect in the development of deucravacitinib is the targeting of a pseudokinase domain. Deucravacitinib is rather specific for TYK2 and its toxic effects are much less than those of the other FDA-approved JAK inhibitors. The successful development of deucravacitinib may stimulate the development of additional pseudokinase ligands for the JAK family and for other kinase families as well.

Roskoski R Jr 《-》

Comparison of baricitinib, upadacitinib, and tofacitinib mediated regulation of cytokine signaling in human leukocyte subpopulations.

McInnes IB ，Byers NL ，Higgs RE ，Lee J ，Macias WL ，Na S ，Ortmann RA ，Rocha G ，Rooney TP ，Wehrman T ，Zhang X ，Zuckerman SH ，Taylor PC ... -  《-》

Tyrosine kinase 2 and Janus kinase‒signal transducer and activator of transcription signaling and inhibition in plaque psoriasis.

Plaque psoriasis is a common, chronic, systemic, immune-mediated inflammatory disease. The Janus kinase-signal transducer and activator of transcription pathway plays a major role in intracellular cytokine signaling in inflammatory processes involved in psoriasis. Although Janus kinase (JAK) 1-3 inhibitors have demonstrated efficacy in patients with moderate-to-severe psoriasis, safety concerns persist and no JAK inhibitor has received regulatory approval to treat psoriasis. Thus, an opportunity exists for novel oral therapies that are safe and efficacious in psoriasis. Tyrosine kinase 2 (TYK2) is a member of the JAK family of kinases and regulates signaling and functional responses downstream of the interleukin 12, interleukin 23, and type I interferon receptors. Deucravacitinib, which is an oral, selective inhibitor that binds to the regulatory domain of TYK2, and brepocitinib (PF-06700841) and PF-06826647, which are topical and oral TYK2 inhibitors, respectively, that bind to the active (adenosine triphosphate-binding) site in the catalytic domain, are in development for psoriasis. Selective, allosteric inhibition of TYK2 signaling may reduce the potential for toxicities associated with pan-JAK inhibitors. This article reviews Janus kinase-signal transducer and activator of transcription and TYK2 signaling and the efficacy and safety of JAK inhibitors in psoriasis to date, focusing specifically on TYK2 inhibitors.

Krueger JG ，McInnes IB ，Blauvelt A 《-》