Introduction: 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.
Methods: 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.
Results: 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.
Conclusion: 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.
Keywords: Baricitinib; C max; Cytokine signaling; Deucravacitinib; IC50; Immune-mediated inflammatory disease; Janus kinase signal transducer; TYK2; Tofacitinib; Upadacitinib.
Psoriasis is a common, chronic inflammatory skin condition that impairs patients’ physical health, emotional well-being, work performance, and overall quality of life. Psoriasis and related conditions such as psoriatic arthritis are caused by abnormalities in the immune system. Various drugs are used or explored to treat these conditions, including Janus kinase (JAK) inhibitors; however, JAK inhibitors are associated with a range of side effects such as abnormal changes in blood cell, cholesterol, and triglyceride levels, as well as liver and kidney dysfunction. Deucravacitinib is a new oral drug in development that blocks a key molecule involved in the pathogenesis of psoriasis known as tyrosine kinase 2 (TYK2). This analysis compared the selectivity of deucravacitinib versus approved JAK 1/2/3 inhibitors (tofacitinib, upadacitinib, and baricitinib) for TYK2 and JAK 1/2/3 in whole blood assays, using therapeutic doses of each drug. The authors reported that deucravacitinib inhibits TYK2 with minimal or no inhibition of JAK 1/2/3. In contrast, tofacitinib, upadacitinib, and baricitinib inhibit JAK 1, JAK 2, and/or JAK 3 to various degrees but do not inhibit TYK2. These results demonstrate that deucravacitinib is a distinct class of drug compared with the JAK 1/2/3 inhibitors. The results of this analysis are consistent with those of two recently completed phase 3 trials in patients with moderate-to-severe plaque psoriasis (POETYK PSO-1 and PSO-2), as well as a phase 2 trial in psoriasis, in which deucravacitinib was efficacious and well tolerated, without clinical or laboratory abnormalities suggestive of JAK 1/2/3 inhibition being observed.
© 2021. The Author(s).