Pharmacokinetics, Pharmacodynamics, and Safety of ASP015K (Peficitinib), a New Janus Kinase Inhibitor, in Healthy Subjects

Tofacitinib and peficitinib inhibitors of Janus kinase for autoimmune disease treatment: a quantum biochemistry approach

Autoimmune inflammatory diseases, such as rheumatoid arthritis (RA) and ulcerative colitis, are associated with an uncontrolled production of cytokines leading to the pronounced inflammatory response of these disorders. Their therapy is currently focused on the inhibition of cytokine receptors, such as the Janus kinase (JAK) protein family. Tofacitinib and peficitinib are JAK inhibitors that have been recently approved to treat rheumatoid arthritis. In this study, an in-depth analysis was carried out through quantum biochemistry to understand the interactions involved in the complexes formed by JAK1 and tofacitinib or peficitinib. Computational analyses provided new insights into the binding mechanisms between tofacitinib or peficitinib and JAK1. The essential amino acid residues that support the complex are also identified and reported. Additionally, we report new interactions, such as van der Waals; hydrogen bonds; and alkyl, pi-alkyl, and pi-sulfur forces, that stabilize the complexes. The computational results revealed that peficitinib presents a similar affinity to JAK1 compared to tofacitinib based on their interaction energies.

Safety and efficacy in the nursing care of people with rheumatic diseases on janus kinase inhibitor therapy

Nurses's support of patients needs an evidence base as much as that of specialists management. However, some more practical aspects need specific questions that are not addressed in medical societies' recommendations. Our objective was to investigate the effect of Janus kinase inhibitors (jakinibs) on efficacy, safety, infections, cardiovascular risk, vaccination, pregnancy and lactation, interactions, surgery, and switch in adult patients with rheumatic diseases. We used the methodology for rapid reviews. Medline was searched for systematic reviews of randomised clinical trials and longitudinal observational studies reporting on the target aspects, without limits, yielding 540 titles, of which 70 articles were selected for detailed reading after the screening of title and abstract. In the case of no systematic review being published on a specific question, we resorted to the information provided by primary studies. The efficacy and safety profiles are similar to that of TNF-inhibitors to which they are compared in most studies; however, there is an increased risk of herpes zoster infections with jakinibs. The evidence on pregnancy, surgery and switches between jakinibs is very limited, although, so far, there are no major issues to inform patients about or to implement specific measures. In general, evidence to support nursing management in patients being treated with jakinibs is of moderate quality and scarce, ought to the recent incursion of jakinibs as a treatment.

Pharmacokinetics and Safety of Single and Multiple Doses of Peficitinib (ASP015K) in Healthy Chinese Subjects

Objective

To investigate the pharmacokinetics and safety of peficitinib (Janus kinase inhibitor for the treatment of rheumatoid arthritis) in healthy Chinese subjects following single and multiple doses.

Methods

This open-label, randomized study was conducted at one site in China. Subjects received peficitinib 50, 100 or 150 mg as a single dose on Day 1 (fasted) and once daily from Days 8 to 13 in the multiple-dose period (fed). Blood samples were collected before administration each day, and up to 72h post administration. Pharmacokinetic assessments included area under the concentration curve (AUC), half-life (t_1/2), maximum concentration (C_max), and time to maximum concentration (t_max) of peficitinib and its metabolites (H1, H2 and H4). Treatment-emergent adverse events (TEAEs) were evaluated.

Results

Thirty-six subjects were enrolled (12 per dose group). After a single dose of peficitinib, median t_max was 1.0–1.5h and mean t_1/2 was 7.4–13.0h for all doses. In the multiple-dose period, median t_max was 1.5–2.0h. Dose-proportional increases in C_max and AUC_24h were observed for peficitinib and its metabolites following single and multiple doses, with minimal drug accumulation. The major metabolite was H2, with a systemic exposure of >150% of the parent AUC. Drug-related TEAEs were experienced by 5 (13.9%) and 12 (33.3%) subjects in the single- and multiple-dose periods, respectively. Following multiple doses of peficitinib, TEAEs were more frequent in higher than lower dose groups but were mild in severity with no related discontinuation or death.

Conclusion

Following single and multiple doses of peficitinib in healthy Chinese subjects, peficitinib demonstrated rapid absorption and was well tolerated at all doses.

Clinicaltrials.gov Identifier

NCT04143477.

JAK Inhibitors and Modulation of B Cell Immune Responses in Rheumatoid Arthritis

Rheumatoid arthritis (RA) is a chronic, systemic immune-mediated inflammatory disease that can lead to joint destruction, functional disability and substantial comorbidity due to the involvement of multiple organs and systems. B cells have several important roles in RA pathogenesis, namely through autoantibody production, antigen presentation, T cell activation, cytokine release and ectopic lymphoid neogenesis. The success of B cell depletion therapy with rituximab, a monoclonal antibody directed against CD20 expressed by B cells, has further supported B cell intervention in RA development. Despite the efficacy of synthetic and biologic disease modifying anti-rheumatic drugs (DMARDs) in the treatment of RA, few patients reach sustained remission and refractory disease is a concern that needs critical evaluation and close monitoring. Janus kinase (JAK) inhibitors or JAKi are a new class of oral medications recently approved for the treatment of RA. JAK inhibitors suppress the activity of one or more of the JAK family of tyrosine kinases, thus interfering with the JAK-Signal Transducer and Activator of Transcription (STAT) signaling pathway. To date, there are five JAK inhibitors (tofacitinib, baricitinib, upadacitinib, peficitinib and filgotinib) approved in the USA, Europe and/ or Japan for RA treatment. Evidence from the literature indicates that JAK inhibitors interfere with B cell functions. In this review, the main results obtained in clinical trials, pharmacokinetic, in vitro and in vivo studies concerning the effects of JAK inhibitors on B cell immune responses in RA are summarized.

Population pharmacokinetic analysis of peficitinib in patients with rheumatoid arthritis

Aims

To analyse the population pharmacokinetics (PK) of peficitinib in patients with rheumatoid arthritis (RA) and assess the potential PK covariates to identify the requirement for dose adjustment in RA patients.

Methods

The analysis incorporated 2464 observations from 98 healthy volunteers and 4919 observations from 989 RA patients. A population PK model for peficitinib in RA patients was constructed by a nonlinear mixed effect model using NONMEM with prior information from a healthy volunteer model.

Results

A 2‐compartment model with sequential zero‐ and first‐order absorption and lag time was constructed for RA patients. Covariate exploration in the RA patient model revealed that estimated glomerular filtration rate (eGFR) and lymphocyte count had a significant effect on apparent total systemic clearance (CL), which was 91.7 L/h (2.3% relative standard error). Compared with the mean population CL, the model predicted mean changes in CL of 12.3 and −10.7% in patients with observed minimum and maximum lymphocyte count of 500 and 4600 10⁶/L, respectively, and mean changes in CL of −17.8 and 16.7% in patients with minimum and maximum eGFR of 36.4 and 188 mL/min/1.73m², respectively. The simulated population mean area under plasma concentration–time curve for 24 hours after dosing showed a 1.35‐fold increase in patients with severe renal impairment (eGFR 22.5 mL/min/1.73m²) compared with patients with reference eGFR (91.5 mL/min/1.73m²).

Conclusion

The population PK model identified eGFR and lymphocyte count as covariates for CL. The magnitude of changes was not considered clinically relevant, indicating no requirement for dose adjustment.

Pharmacokinetics, Pharmacodynamics, and Safety of Peficitinib (ASP015K) in Healthy Male Caucasian and Japanese Subjects

BACKGROUND AND OBJECTIVE

Peficitinib pharmacokinetics and pharmacodynamics have been characterized mainly in Caucasian subjects. This study investigated the pharmacokinetics, pharmacodynamics, safety, and tolerability of peficitinib in healthy Japanese subjects compared with Caucasian subjects.

METHODS

In this single-center, randomized, double-blind, placebo-controlled study, a cohort of healthy Japanese (n = 24) and Caucasian (n = 24) men received a single oral dose of peficitinib (20, 60, or 200 mg) or placebo. Another cohort of Japanese men (n = 24) received peficitinib (10, 30, or 100 mg) or placebo twice daily for 7 days. Pharmacokinetic and pharmacodynamic parameters were assessed, and adverse events (AEs) monitored throughout.

RESULTS

Dose proportionality of maximum plasma drug concentration (C_max) and area under the plasma concentration-time curve extrapolated to infinity (AUC_inf) was demonstrated for both ethnicities. The geometric mean ratio for dose-normalized C_max was 45.7-98.8% higher and AUC_inf was 33.8-66.4% higher in Japanese versus Caucasian subjects. Mean peak inhibition of STAT5 phosphorylation was higher in Japanese than Caucasian subjects for a given peficitinib dose, but inhibition was comparable across ethnicities for a given plasma peficitinib concentration. In the multiple-dose study, plasma peficitinib concentrations were similar on day 1 and day 7. All AEs were mild, and none resulted in study discontinuation.

CONCLUSIONS

Peficitinib was well tolerated at doses up to 200 mg daily for 7 days in healthy Japanese subjects. Dose-proportional exposure was demonstrated across the single-dose range of 20-200 mg, with greater peficitinib exposure in Japanese compared with Caucasian subjects. The pharmacokinetic/pharmacodynamic relationships were considered comparable between these populations. CLINICALTRIALS.

GOV IDENTIFIER

NCT01225224.

Investigation of Potential Drug-Drug Interactions between Peficitinib (ASP015K) and Methotrexate in Patients with Rheumatoid Arthritis

BACKGROUND

Methotrexate is frequently used to treat rheumatoid arthritis. Peficitinib (ASP015K; Smyraf®), an oral Janus kinase inhibitor indicated for the treatment of rheumatoid arthritis, may be coadministered with methotrexate.

OBJECTIVE

The objective of this study was to investigate potential drug-drug interactions of peficitinib with methotrexate and the short-term safety of coadministration.

PATIENTS AND METHODS

This phase I, open-label, single-sequence study included patients with rheumatoid arthritis taking a stable dose of methotrexate. Patients received their prescribed methotrexate dose (Day 1) and then peficitinib (100 mg) twice daily from Day 3 until the morning of Day 9; a second methotrexate dose was coadministered with peficitinib on Day 8. Serial blood samples were collected for methotrexate concentration after dosing on Days 1 (methotrexate alone) and 8 (methotrexate plus peficitinib) and for peficitinib concentration after dosing on Days 7 (peficitinib alone) and 8 (methotrexate plus peficitinib). Pre-dose concentrations of peficitinib were measured (Days 3-8).

RESULTS

Peficitinib concentrations reached steady state on Day 5. Administration of peficitinib did not result in changes to methotrexate area under the concentration-time curve from time zero to infinity or maximum observed concentration following a methotrexate dose (15-25 mg), and there was no significant effect of methotrexate (15-25 mg) on peficitinib area under the concentration-time curve within a 12-hour dosing interval. There were no new tolerability or safety signals after coadministration of peficitinib and methotrexate. One patient experienced two serious adverse events and withdrew from the study without receiving peficitinib.

CONCLUSIONS

Pharmacokinetic results showed no significant interactions between peficitinib and methotrexate. CLINICALTRIALS.

GOV IDENTIFIER

NCT01754805.

JAK-Inhibitors for the Treatment of Rheumatoid Arthritis: A Focus on the Present and an Outlook on the Future

Janus kinase inhibitors (JAKi) belong to a new class of oral targeted disease-modifying drugs which have recently revolutionized the therapeutic panorama of rheumatoid arthritis (RA) and other immune-mediated diseases, placing alongside or even replacing conventional and biological drugs. JAKi are characterized by a novel mechanism of action, consisting of the intracellular interruption of the JAK-STAT pathway crucially involved in the immune response. The aim of this narrative review is to globally report the most relevant pharmacological features and clinical outcomes of the developed and incoming JAKi for RA, based on the available preclinical and clinical evidence. A total of 219 papers, including narrative and systematic reviews, randomized controlled trials (RCTs), observational studies, case reports, guidelines, and drug factsheets, were selected. The efficacy and safety profile of both the first generation JAKi (baricitinib and tofacitinib) and the second generation JAKi (upadacitinib, filgotinib, peficitinib, decernotinib and itacitinib) were compared and discussed. Results from RCTs and real-life data are encouraging and outline a rapid onset of the pharmacologic effects, which are maintained during the time. Their efficacy and safety profile are comparable or superior to those of biologic agents and JAKi proved to be efficacious when given as monotherapy. Finally, the manufacturing of JAKi is relatively easier and cheaper than that of biologics, thus increasing the number of compounds being formulated and tested for clinical use.

The Bioequivalence of Two Peficitinib Formulations, and the Effect of Food on the Pharmacokinetics of Peficitinib: Two-Way Crossover Studies of a Single Dose of 150 mg Peficitinib in Healthy Volunteers

The marketed tablet formulation of peficitinib differs from the tablet used during the clinical trials. The bioequivalence of the marketed formulation and developmental tablet, and the food effect on the marketed formulation, were analyzed in 2 Japanese open‐label, randomized, 2‐way crossover studies in healthy male volunteers. Volunteers received a single oral dose of the marketed 150‐mg peficitinib tablet under fasted conditions (bioequivalence), and under fed or fasted conditions (food effect). Bioequivalence was compared with the developmental 150‐mg tablet. Samples for pharmacokinetic analysis were collected before dose and ≤72 hours after dose. Safety assessments included adverse events, vital signs, and laboratory variables. In total, 40 and 18 subjects were randomized to the bioequivalence and food effect studies, respectively. The 2 peficitinib formulations were bioequivalent (90% confidence intervals of the geometric mean ratios for C_max and AUC_t of peficitinib were within predefined limits of 0.8 to 1.25). The AUC_last and the C_max of the marketed tablet were 36.8% and 56.4% higher, respectively, under fed versus fasted conditions. Peficitinib was well tolerated. The marketed 150‐mg tablet formulation of peficitinib was bioequivalent to the developmental 150‐mg formulation, with no discernible safety differences. Bioavailability increased under fed conditions with the marketed tablet formulation.

Pharmacokinetics and Safety of a Single Oral Dose of Peficitinib (ASP015K) in Japanese Subjects with Normal and Impaired Renal Function

BACKGROUND AND OBJECTIVE

This study measured and compared the exposure and safety of peficitinib (ASP015K), a novel oral Janus kinase inhibitor, in subjects with normal and impaired renal function after a single oral, clinically relevant peficitinib dose.

METHODS

This was an open-label, parallel-group study conducted at two centres in Japan. Subjects with normal and mildly, moderately, or severely impaired renal function received a single oral dose of peficitinib (one 150 mg tablet) under fasting conditions in a hospital setting. Blood samples were collected prior to administration and up to 72 h post-dose for pharmacokinetic assessment. Safety was assessed up to 7 days post-dose.

RESULTS

Peficitinib plasma concentration-time profiles were similar between those with normal and impaired renal function. In subjects with impaired renal function, area under the plasma concentration-time curve and maximum concentration were 0.8- to 1.1-fold those in subjects with no impairment. Two subjects (one in the normal group and one in the mildly impaired group) each experienced a treatment-emergent adverse event (TEAE). There were no serious TEAEs, deaths or TEAEs leading to treatment withdrawal.

CONCLUSIONS

Peficitinib exposure and TEAEs were similar in subjects with and without renal impairment after a single oral 150 mg dose. Based on these findings, it is not expected that peficitinib dose adjustment will be required in clinical practice, according to the degree of renal impairment. CLINICALTRIALS.

GOV IDENTIFIER

NCT02603497.

A drug-drug interaction study to evaluate the impact of peficitinib on OCT1- and MATE1-mediated transport of metformin in healthy volunteers

Purpose

Peficitinib is an oral pan-Janus kinase inhibitor for the treatment of rheumatoid arthritis. Co-administration of peficitinib with metformin, a type 2 diabetes therapy, can occur in clinical practice. Hepatic and renal uptake of metformin is mediated by organic cation transporter 1 (OCT1) and OCT2, respectively, and its renal excretion by multidrug and toxin extrusion 1 (MATE1) and MATE2-K. This study investigated the effect of peficitinib on metformin pharmacokinetics in vitro and in healthy volunteers.

Methods

Inhibitory effects of peficitinib and its metabolite H2 on metformin uptake into human OCT1/2- and MATE1/2-K-expressing cells were assessed in vitro. In an open-label, drug–drug interaction study, 24 healthy volunteers received a single dose of metformin 750 mg on Days 1 and 10, and a single dose of peficitinib 150 mg on Days 3 and 5–11. Blood and urine samples were collected pre-dose on Days 1 and 10, and at intervals ≤ 48 h post-dose. Metformin concentration was determined by liquid chromatography–tandem mass spectrometry and its pharmacokinetic parameters calculated.

Results

Peficitinib, but not H2, inhibited metformin uptake into OCT1- and MATE1/2-K-expressing cells. Repeated-dose administration of peficitinib reduced metformin area under the concentration–time curve from 0 h extrapolated to infinity (AUC_inf) by 17.4%, maximum plasma concentration (C_max) by 17.0%, and renal clearance (CL_R) by 12.9%. Co-administration of peficitinib with metformin was generally well tolerated.

Conclusion

Slight changes in AUC_inf, C_max and CL_R of metformin were observed when co-administered with peficitinib; however, these changes were considered not clinically relevant.

Electronic supplementary material

The online version of this article (10.1007/s00228-020-02876-2) contains supplementary material, which is available to authorized users.

Peficitinib for the treatment of rheumatoid arthritis: an overview from clinical trials

INTRODUCTION

The treatment of rheumatoid arthritis (RA), a chronic, systemic, autoimmune disease, has been greatly advanced by the introduction of biologic disease-modifying antirheumatic drugs (DMARDs); however, many patients still fail to achieve disease remission. Peficitinib, an orally bioavailable inhibitor of the Janus kinase (JAK) receptor family, was approved in Japan in 2019 and Korea in 2020 for the treatment of RA.

AREAS COVERED

This review provides an overview of JAK inhibitors currently marketed or in development; the pharmacodynamics and pharmacokinetics of peficitinib; and the efficacy and safety data for peficitinib from Phase 2b and 3 trials.

EXPERT OPINION

Peficitinib has proven clinical efficacy in Asian patients (Japan, Korea, and Taiwan) with RA who have an inadequate response to conventional DMARDs. In Phase 3 trials, clinical improvements and prevention of joint destruction were demonstrated for both 100 mg and 150 mg once-daily peficitinib versus placebo, and treatment for up to 52 weeks was well tolerated. Safety signals, in particular the increased incidence of herpes zoster-related disease, appeared in line with other JAK inhibitors. Post-launch monitoring will establish the long-term safety and effectiveness of this drug, and further studies are necessary to determine its potential use in non-Asian populations.

Pharmacokinetics and Safety of a Single Oral Dose of Peficitinib (ASP015K) in Japanese Subjects With Normal and Impaired Hepatic Function

Peficitinib (ASP015K) is a novel Janus kinase inhibitor developed for the treatment of rheumatoid arthritis (RA). The impact of hepatic impairment on the peficitinib pharmacokinetic (PK) and safety profile was investigated in non‐RA subjects (n = 24) in an open‐label, parallel‐group, multicenter comparative study in Japan. Subjects received a single, clinically relevant, oral dose of a peficitinib 150 mg tablet under fasting conditions. Plasma PK parameters were measured for peficitinib and its metabolites H1 (sulfate and methylated metabolite), H2 (sulfate metabolite), and H4 (methylated metabolite) in subjects with normal hepatic function, mild hepatic impairment, or moderate hepatic impairment. The peficitinib area under the plasma‐concentration–time curve from time 0 to infinity (AUC_inf) and maximum observed concentration (C_max) were not markedly different in subjects with mild hepatic impairment versus normal hepatic function. In subjects with moderate hepatic impairment versus normal hepatic function, the geometric mean ratios for peficitinib AUC_inf and C_max, were 1.92 (90% CI: 1.39, 2.66) and 1.82 (90% CI: 1.24, 2.69), respectively. Five treatment‐emergent adverse events (TEAEs) were experienced by 3 subjects, 1 in each group. There were no deaths, no serious TEAEs, and no TEAEs leading to withdrawal. In summary, the PK profile was unaltered in subjects with mild hepatic impairment after a single clinically relevant dose of peficitinib, but exposure almost doubled in subjects with moderate hepatic impairment. Peficitinib dose reduction may be considered in RA patients with moderate hepatic impairment.

Peficitinib: First Global Approval

Peficitinib [Smyraf^® (Astellas Pharma)] is a Janus kinase (JAK)1, JAK2, JAK3 and tyrosine kinase (Tyk)2 (pan-JAK) inhibitor recently approved in Japan for the treatment of rheumatoid arthritis. Inhibition of JAK suppresses the activation of cytokine signalling pathways involved in inflammation and joint destruction in rheumatoid arthritis. Peficitinib has been shown to significantly improve ACR20 and other measures of disease severity and to reduce the mean modified total Sharp score change from baseline in clinical trials. This article summarizes the milestones in the development of peficitinib leading to this first approval as a treatment for rheumatoid arthritis in patients who have an inadequate response to conventional therapies.

JAK3-selective inhibitor peficitinib for the treatment of rheumatoid arthritis

Introduction: Rheumatoid arthritis (RA) is a chronic progressive autoimmune disease characterized by synovitis as well as symmetric and destructive arthropathy. Although several disease modified antirheumatic-drugs (DMARDs) have widely used in clinical practice, certain patients are nonresponsive to or cannot take such medications due to adverse reactions. It is evident that Janus kinase (JAK) inhibitors have the potential to provide a significant breakthrough in the treatment of RA. These potent, orally administered, JAK inhibitors simplify the treatment options for patients. Areas covered: We discuss the pharmacodynamics, pharmacokinetics, efficacy, and safety of peficitinib for the treatment of RA. Expert opinion: Peficitinib is a novel JAK3 inhibitor potently inhibiting JAK3 enzymatic activity and JAK1/3-mediated cell proliferation. Its selectivity for JAK family kinases is similar to that of tofacitinib, but slightly less potent for JAK2. It is currently being evaluated by the FDA to treat adult patients with moderately to severely active RA who show inadequate response to or are intolerant of methotrexate. It can be used either as monotherapy or combination therapy with methotrexate, or other DMARDs. However, we think that more cautious consideration and measurement for adverse events are needed, after considering the safety results of ongoing clinical studies of peficitinib.

Comparison of Janus kinase inhibitors in the treatment of rheumatoid arthritis: a systemic literature review

Several Janus kinase (JAK) inhibitors, oral targeted disease-modifying drugs, will be approved for the treatment of rheumatoid arthritis (RA) and other diseases. This review compares and contrasts the efficacy of JAK inhibitors (tofacitinib, baricitinib, upadacitinib, filgotinib, peficitinib and decernotinib) in RA including: early RA methotrexate-naive patients, post methotrexate failure and post biologics. Trials in monotherapy, combination with disease modifying drugs such as methotrexate, and comparing with adalimumab in biologic-naive patients were studied. The efficacy is superior to methotrexate in naive patients and equal or superior to adalimumab depending on the drug and dose. There is a class effect of adverse events. Serious infections occur at a rate similar to other advanced therapies in RA, although more reactivation of herpes zoster occurs.

Targeting Activated Synovial Fibroblasts in Rheumatoid Arthritis by Peficitinib

Background: Synovial fibroblasts (SF) play a major role in the pathogenesis of rheumatoid arthritis (RA) and develop an aggressive phenotype destroying cartilage and bone, thus termed RASF. JAK inhibitors have shown to be an efficient therapeutic option in RA treatment, but less is known about the effect of JAK inhibitors on activated RASF. The aim of the study was to examine the effects of JAK inhibitors on activated RASF.

Methods: Synovium of RA patients was obtained during knee replacement surgeries. Synoviocytes were isolated and pretreated with JAK inhibitors. Pro-inflammatory cytokines and matrix degrading proteinases were measured by ELISA in supernatant after stimulation with oncostatin M or IL-1β. The proliferation of RASF was measured by BrdU incorporation. Cell culture inserts were used to evaluate cell migration. For adhesion assays, RASF were seeded in culture plates. Then, plates were extensively shaken and adherent RASF quantified. Cell viability, cytotoxicity and apoptosis were measured using the ApoTox-Glo™ Triplex and the CellTox™ Green Cytotoxicity Assay.

Results: Tofacitinib and baricitinib decreased the IL-6 release of RASF stimulated with oncostatin M. JAK inhibition attenuated the IL-6 release of IL-1β activated and with soluble IL-6 receptor treated RASF. In contrast, only peficitinib and filgotinib decreased the IL-6 release of RASF activated with IL-1β. Peficitinib decreased also the MMP-3, CXCL8, and CXCL1 release at 5 μM. Moreover, peficitinib was the only JAK inhibitor suppressing proliferation of activated RASF at 1 μM. Peficitinib further decreased the migration of RASF without being cytotoxic or pro-apoptotic and without altering cell adhesion.

Conclusions: JAK inhibitors effectively suppress the inflammatory response induced by oncostatin M and by transsignaling of IL-6 in RASF. Only peficitinib modulated the IL-1β-induced response of RASF and their proliferation in vitro at concentrations close to reported Cmax values of well tolerated doses in vivo. In contrast to filgotinib, peficitinib also highly suppressed RASF migration showing the potential of peficitinib to target RASF.

Clinical efficacy of new JAK inhibitors under development. Just more of the same?

Janus kinase inhibition is promising in the treatment of RA, with already two oral drugs marketed. New compounds are under investigation that are more selective for Janus kinase 1 or Janus kinase 3. Phase II results for filgotinib, upadacitinib, peficitinib and decernotinib are reviewed showing almost consistently a fast dose-dependent clinical improvement similar to already approved drugs tofacitinib and baricitinib. I will reflect on the most frequently reported dose-dependent adverse events and laboratory changes. Some are similar for all drugs of this class, some are more specific for a certain drug, but all may influence future treatment effectiveness in daily practice. This implies the need for a critical evaluation of phase III trials, and eventually trials specifically powered for conclusions on the safety profile and registries once these drugs become marketed. These innovative drugs also need head-to-head trials versus biologics or in-class as well as specific strategy studies to determine their optimal future use.

JAK inhibitors in dermatology: The promise of a new drug class

New molecularly targeted therapeutics are changing dermatologic therapy. Janus kinase-signal transducer and activator of transcription (JAK-STAT) is an intracellular signaling pathway upon which many different proinflammatory signaling pathways converge. Numerous inflammatory dermatoses are driven by soluble inflammatory mediators, which rely on JAK-STAT signaling, and inhibition of this pathway using JAK inhibitors might be a useful therapeutic strategy for these diseases. Growing evidence suggests that JAK inhibitors are efficacious in atopic dermatitis, alopecia areata, psoriasis, and vitiligo. Additional evidence suggests that JAK inhibition might be broadly useful in dermatology, with early reports of efficacy in several other conditions. JAK inhibitors can be administered orally or used topically and represent a promising new class of medications. The use of JAK inhibitors in dermatology is reviewed here.