The Pharmacokinetics, Metabolism, and Clearance Mechanisms of Ritlecitinib, a Janus Kinase 3 and Tyrosine-Protein Kinase Family Inhibitor, in Humans.

Ritlecitinib is an oral once-daily irreversible inhibitor of Janus kinase 3 and tyrosine-protein kinase family being developed for the treatment of moderate-to-severe alopecia areata. This study examined the disposition of ritlecitinib in male participants following oral and intravenous administration using accelerator mass spectroscopy methodology to estimate pharmacokinetic parameters and characterize metabolite profiles. The results indicated ritlecitinib had a systemic clearance of 43.7 L/h, a steady state volume of distribution of 73.8 L, extent of absorption of 89%, time to maximum plasma concentration of ∼0.5 hours, and absolute oral bioavailability of 64%. An observed long terminal half-life of total radioactivity was primarily attributed to ritlecitinib binding to plasma albumin. Ritlecitinib was the main circulating drug species in plasma (∼30%), with one major pharmacologically inactive cysteine conjugated metabolite (M2) at >10%. Oxidative metabolism (fractional clearance 0.47) and glutathione-related conjugation (fractional clearance 0.24) were the primary routes of elimination for ritlecitinib with the greatest disposition of radioactivity shown in the urine (∼71%). In vitro phenotyping indicated ritlecitinib cytochrome P450 (CYP) fraction of metabolism assignments of 0.29 for CYP3A, 0.09 for CYP2C8, 0.07 for CYP1A2, and 0.02 for CYP2C9. In vitro phenotyping in recombinant human glutathione S-transferases indicated ritlecitinib was turned over by a number of cytosolic and microsomal enzyme isoforms. SIGNIFICANCE STATEMENT: This study provides a detailed understanding of the disposition and metabolism of ritlecitinib, a JAK3 and TEC family kinase inhibitor for alopecia areata in humans, as well as characterization of clearance pathways and pharmacokinetics of ritlecitinib and its metabolites. As an AMS-based ADME study design, we have expanded on reporting the standard ADME endpoints, providing key pharmacokinetic parameters, such as clearance, volume of distribution, and bioavailability, allowing for a more comprehensive understanding of drug disposition.

Model-Informed Assessment of Probability of Phase 3 Success for Ritlecitinib in Patients with Moderate-to-Severe Ulcerative Colitis.

Ritlecitinib, an oral Janus kinase 3/tyrosine kinase expressed in hepatocellular carcinoma family inhibitor, was evaluated in patients with ulcerative colitis (UC) in a phase 2b trial. Model-informed drug development strategies were applied to bridge observations from phase 2b to predictions for a proposed phase 3 study design to assess the probability of achieving the target efficacy outcome. A longitudinal exposure-response model of the time course of the 4 Mayo subscores (rectal bleeding, stool frequency, physician's global assessment, and endoscopic subscore) in patients with UC receiving placebo or ritlecitinib was developed using population modeling approaches and an item response theory framework. The quantitative relationships between the 4 Mayo subscores accommodated the prediction of composite endpoints such as total Mayo score and partial Mayo score (key endpoints from phase 2b), and modified clinical remission and endoscopic remission (proposed phase 3 endpoints). Clinical trial simulations using the final model assessed the probability of candidate ritlecitinib dosing regimens (including those tested in phase 2b and alternative) and phase 3 study designs for achieving target efficacy outcomes benchmarked against an approved treatment for moderate-to-severe UC. The probabilities of achieving target modified clinical remission and endoscopic improvement outcomes at both weeks 8 and 52 for ritlecitinib 100 mg once daily was 74.8%. Model-based assessment mitigated some of the risk associated with proceeding to pivotal phase 3 trials with dosing regimens of which there was limited clinical experience.

Employing zero-inflated beta distribution in an exposure-response analysis of TYK2/JAK1 inhibitor brepocitinib in patients with plaque psoriasis.

Brepocitinib is an oral selective dual TYK2/JAK1 inhibitor and based on its cytokine inhibition profile is expected to provide therapeutic benefit in the treatment of plaque psoriasis. Efficacy data from a completed Phase 2a study in patients with moderate-to-severe plaque psoriasis were utilized to develop a population exposure-response model that can be employed to inform dose selection decisions for further clinical development. A modeling approach that employs the zero-inflated beta distribution was used to account for the bounded nature and distributional characteristics of the Psoriasis Area and Severity Index (PASI) score data. The developed exposure-response model provided an adequate description of the observed PASI scores across all the treatment arms tested and across both the induction and maintenance dosing periods of the study. In addition, the developed model exhibited a good predictive capacity with regard to the derived responder metrics (e.g., 75%/90%/100% improvement in PASI score [PASI75/90/100]). Clinical trial simulations indicated that the induction/maintenance dosing paradigm explored in this study does not offer any advantages from an efficacy perspective and that doses of 10, 30, and 60 mg once-daily may be suitable candidates for clinical evaluation in subsequent Phase 2b studies.

Master protocols and other innovative trial designs in inflammation and immunology to expedite clinical drug development.

Master protocol designs, such as umbrella and basket studies, allow multiple compounds or multiple target populations to be evaluated simultaneously within a single protocol, and have been widely adopted in oncology clinical trials. These novel designs can also be applied in other therapeutic areas, where they could have several benefits over conducting traditional randomized controlled trials. Here, we detail Pfizer's recent implementations of master protocol designs in inflammation and immunology clinical studies, focusing on the opportunities for cost and resource savings and how these designs can expedite the time required to bring new treatments to patients in need.

Brepocitinib, Zimlovisertib, and Ropsacitinib in Hidradenitis Suppurativa.

BACKGROUND: Hidradenitis suppurativa (HS) is a debilitating, inflammatory skin disease with limited treatment options and partially understood pathophysiology. Using an umbrella trial design, three kinase inhibitor immunomodulators with different mechanisms of action were evaluated. METHODS: This phase 2a, double-blind, parallel-group trial enrolled adults with moderate to severe HS who were then randomly assigned (1:1:1:1) to once-daily brepocitinib 45 mg (a JAK1/TYK2 inhibitor), zimlovisertib 400 mg (an IRAK4 inhibitor), ropsacitinib 400 mg (a TYK2 inhibitor), or matching placebo for 16 weeks. The primary end point was the percentage of participants achieving HS clinical response (HiSCR) at week 16. Safety, including treatment-emergent adverse events (TEAEs), was monitored throughout. RESULTS: Totals of 52, 47, 47, and 48 participants were assigned to brepocitinib, zimlovisertib, ropsacitinib, and placebo, respectively. At week 16, 28% were lost to follow-up and assumed to be nonresponders; HiSCR occurred in 33.3% (16/48) of participants receiving placebo and in 51.9% (27/52), 34.0% (16/47), and 37.0% (17/46) of those receiving brepocitinib, zimlovisertib, and ropsacitinib (difference in percentage points vs. placebo [90% confidence interval], 18.7 [2.7 to 34.6], 0.7 [−15.2 to 16.7], and 3.5 [−12.6 to 19.6]), respectively. TEAEs occurred more frequently with active treatment (brepocitinib, 30 [57.7%]; zimlovisertib, 26 [55.3%]; ropsacitinib, 29 [61.7%]; placebo, 23 [47.9%]). Most TEAEs (infections, skin disorders, and gastrointestinal symptoms) were mild; there were no deaths. CONCLUSIONS: Participants with moderate to severe HS treated with brepocitinib experienced greater clinical response, whereas those on zimlovisertib and ropsacitinib did not, compared with placebo. These results favor the JAK/STAT pathway as an immunologic target in HS and did not confirm a role for selective IRAK4 or TYK2 inhibition. These results should be confirmed in larger studies with longer follow-up. (Funded by Pfizer; ClinicalTrials.gov registration number, NCT04092452.)

Population pharmacokinetic modeling of oral brepocitinib in healthy volunteers and patients with immuno-inflammatory diseases.

The objective of this population pharmacokinetic (PK) analysis was to characterize the concentration-time profile of brepocitinib plasma concentration after single- and multiple-oral administration in healthy volunteers (HVs) and patients with immuno-inflammatory diseases. Blood samples from phase I HV and phase II clinical studies of patients with alopecia areata, psoriasis, psoriatic arthritis, ulcerative colitis (UC), vitiligo, and hidradenitis suppurativa were analyzed using a nonlinear mixed-effects modeling approach. Effects of patients' characteristics on brepocitinib exposure were investigated. Overall, 8552 brepocitinib plasma concentrations from 775 individuals were included in the analysis. The PKs of brepocitinib were adequately described by a two-compartment model with first-order absorption and a lag time for tablet formulation, dose-dependent bioavailability, and Box-Cox transformed interindividual variabilities on apparent clearance (CL/F) and apparent central volume of distribution (Vc/F). For a typical 70-kg non-Asian female patient with baseline aspartate aminotransferase of 22 unit/liter, CL/F and Vc/F estimates were 17.5 L/h and 88.5 L, respectively. Asians had a higher exposure (independent of body weight), caused by a 10% lower CL/F when compared to other individuals. Independent of baseline body weight, the male population showed 13% higher Vc/F compared to the female population. Patients with UC were predicted to have 46% slower absorption rate compared to other individuals. The PKs of brepocitinib were well-characterized by a two-compartment model with first-order absorption and dose-dependent bioavailability. Several covariates, such as race and sex, were identified to have statistically significant, but not clinically meaningful, effects on the estimated PK parameters.

Baseline Serum and Stool Microbiome Biomarkers Predict Clinical Efficacy and Tissue Molecular Response After Ritlecitinib Induction Therapy in Ulcerative Colitis.

BACKGROUND AND AIMS: Ritlecitinib, an oral JAK3/TEC family kinase inhibitor, was well-tolerated and efficacious in the phase 2b VIBRATO study in participants with moderate-to-severe ulcerative colitis [UC]. The aim of this study was to identify baseline serum and microbiome markers that predict subsequent clinical efficacy and to develop noninvasive serum signatures as potential real-time noninvasive surrogates of clinical efficacy after ritlecitinib. METHODS: Tissue and peripheral blood proteomics, transcriptomics, and faecal metagenomics were performed on samples before and after 8 weeks of oral ritlecitinib induction therapy [20 mg, 70 mg, 200 mg, or placebo once daily, N = 39, 41, 33, and 18, respectively]. Linear mixed models were used to identify baseline and longitudinal protein markers associated with efficacy. The combined predictivity of these proteins was evaluated using a logistic model with permuted efficacy data. Differential expression of faecal metagenomics was used to differentiate responders and nonresponders. RESULTS: Peripheral blood serum proteomics identified four baseline serum markers [LTA, CCL21, HLA-E, MEGF10] predictive of modified clinical remission [MR], endoscopic improvement [EI], histological remission [HR], and integrative score of tissue molecular improvement. In responders, 37 serum proteins significantly changed at Week 8 compared with baseline [false discovery rate of <0.05]; of these, changes in four [IL4R, TNFRSF4, SPINK4, and LAIR-1] predicted concurrent EI and HR responses. Faecal metagenomics analysis revealed baseline and treatment response signatures that correlated with EI, MR, and tissue molecular improvement. CONCLUSIONS: Blood and microbiome biomarkers stratify endoscopic, histological, and tissue molecular responses to ritlecitinib, which may help guide future precision medicine approaches to UC treatment. ClinicalTrials.gov NCT02958865.

Comparative Study of Dermal Pharmacokinetics Between Topical Drugs Using Open Flow Microperfusion in a Pig Model.

PURPOSE: Accurate methods to determine dermal pharmacokinetics are important to increase the rate of clinical success in topical drug development. We investigated in an in vivo pig model whether the unbound drug concentration in the interstitial fluid as determined by dermal open flow microperfusion (dOFM) is a more reliable measure of dermal exposure compared to dermal biopsies for seven prescription or investigational drugs. In addition, we verified standard dOFM measurement using a recirculation approach and compared dosing frequencies (QD versus BID) and dose strengths (high versus low drug concentrations). METHODS: Domestic pigs were topically administered seven different drugs twice daily in two studies. On day 7, drug exposures in the dermis were assessed in two ways: (1) dOFM provided the total and unbound drug concentrations in dermal interstitial fluid, and (2) clean punch biopsies after heat separation provided the total concentrations in the upper and lower dermis. RESULTS: dOFM showed sufficient intra-study precision to distinguish interstitial fluid concentrations between different drugs, dose frequencies and dose strengths, and had good reproducibility between studies. Biopsy concentrations showed much higher and more variable values. Standard dOFM measurements were consistent with values obtained with the recirculation approach. CONCLUSIONS: dOFM pig model is a robust and reproducible method to directly determine topical drug concentration in dermal interstitial fluid. Dermal biopsies were a less reliable measure of dermal exposure due to possible contributions from drug bound to tissue and drug associated with skin appendages.

Evolution of Ritlecitinib Population Pharmacokinetic Models During Clinical Drug Development.

BACKGROUND: Ritlecitinib is an oral Janus kinase 3/tyrosine kinase expressed in hepatocellular carcinoma family inhibitor undergoing parallel clinical development for alopecia areata, vitiligo, ulcerative colitis, Crohn's disease, and rheumatoid arthritis. OBJECTIVE: As studies read out simultaneously, strategic planning of population pharmacokinetic model development and evaluation is required to ensure timely decisions. METHODS: Data from healthy participants and patients from 12 clinical trials between December 2014 and July 2021 were included: seven phase I studies in healthy participants and organ impairment, five phase II/III studies in patients with rheumatoid arthritis, ulcerative colitis, alopecia areata, and vitiligo. Population pharmacokinetic models consisted of stepwise procedures to accommodate data availability and the model's application to answering clinical development questions. At each iteration of the model update, parameters of the next model were re-estimated by leveraging previous information and new data. RESULTS: Three model development lifecycle iterations of the ritlecitinib population pharmacokinetic model were conducted to support alopecia areata, vitiligo, and ulcerative colitis study readouts. Initial structural modeling based on healthy participant data (and some rheumatoid arthritis and alopecia areata data) in iteration 1 provided a platform for comprehensive covariate testing during iteration 2, and model evaluation and implementation of the frequentist prior approach in iteration 3. The final model was a two-compartment model with first-order absorption and direct-response non-stationary clearance and bioavailability driven by concentrations in the peripheral compartment. CONCLUSIONS: The present approach demonstrated the evolution of three population pharmacokinetic models with accumulating data, addressed clinical drug development questions related to systemic exposures of ritlecitinib, and informed the approved product label. CLINICAL TRIAL REGISTRATION: NCT02309827, NCT02684760, NCT02958865, NCT02969044, NCT03232905, NCT03732807, NCT04016077, NCT03715829, NCT04037865, NCT04004663, NCT04634565, NCT02974868.

A phase 1 study to investigate the absorption, distribution, metabolism and excretion of brepocitinib in healthy males using a 14 C-microdose approach.

AIMS: Brepocitinib is a tyrosine kinase 2/Janus kinase 1 inhibitor being investigated for the treatment of several autoimmune diseases. This study assessed the absorption, distribution, metabolism and excretion of oral brepocitinib, and the absolute oral bioavailability (F) and fraction absorbed (Fa ) using a 14 C microtracer approach. METHODS: This was a phase 1 open-label, nonrandomized, fixed sequence, two-period, single-dose study of brepocitinib in healthy male participants. Participants received a single oral 60 mg dose of 14 C brepocitinib (~300 nCi) in Period A, then an unlabelled oral 60 mg dose followed by an intravenous (IV) 30 µg dose of 14 C labelled brepocitinib (~300 nCi) in Period B. Mass balance, pharmacokinetic parameters and safety were assessed. RESULTS: Six participants were enrolled. Brepocitinib was absorbed rapidly following oral administration. In Period A, total recovery of the oral dose was 96.7% ± 6.3% (88.0% ± 8.0% in urine, 8.7% ± 2.1% in faeces). In Period B, a small fraction (6.0% of the oral dose) was recovered unchanged in urine. F and Fa were 74.6% (90% confidence interval 67.3%, 82.8%) and 106.9%, respectively. Brepocitinib demonstrated an acceptable safety profile and was well tolerated following oral or oral then IV administrations. No deaths, serious adverse events or discontinuations were reported. CONCLUSION: Intestinal absorption of brepocitinib was essentially complete after oral administration, with F ~75%. Drug-related material recovery was high, with the majority excreted in urine. The major route of elimination of brepocitinib was renal excretion as metabolites, whereas urinary elimination of unchanged brepocitinib was minor. NCT: NCT03770039.

Efficacy and safety of topical brepocitinib cream for mild-to-moderate chronic plaque psoriasis: a phase IIb randomized double-blind vehicle-controlled parallel-group study.

BACKGROUND: Plaque psoriasis (PsO) is an inflammatory skin disease driven, in part, by the activation of Janus kinase (JAK) signalling pathways. OBJECTIVES: To assess the efficacy and safety of multiple doses of topical brepocitinib, a tyrosine kinase 2/JAK1 inhibitor, in participants with mild-to-moderate PsO. METHODS: This phase IIb multicentre randomized double-blind study was conducted in two stages. In stage 1, participants received one of eight treatments for 12 weeks: brepocitinib 0.1% once daily, 0.3% once or twice daily, 1.0% once or twice daily, 3.0% once daily, or vehicle once or twice daily. In stage 2, participants received brepocitinib 3.0% twice daily or vehicle twice daily. The primary endpoint was the change from baseline in Psoriasis Area and Severity Index (PASI) score at week 12, analysed using analysis of covariance. The key secondary endpoint was the proportion of participants who achieved a Physician Global Assessment response [score of clear (0) or almost clear (1) and an improvement of ≥ 2 points from baseline] at week 12. Additional secondary endpoints included the difference vs. vehicle in change from baseline in PASI, using mixed-model repeated measures, and the change from baseline in Peak Pruritus Numerical Rating Scale at week 12. Safety was monitored. RESULTS: Overall, 344 participants were randomized. Topical brepocitinib did not result in statistically significant changes compared with respective vehicle controls in the primary or key secondary efficacy endpoints for any dose group. At week 12, least squares mean change from baseline in PASI score ranged from -1.4 to -2.4 for the brepocitinib once-daily groups vs. -1.6 for vehicle once daily, and from -2.5 to -3.0 for the brepocitinib twice-daily groups vs. -2.2 for vehicle twice daily. From week 8, change from baseline in PASI score separated from vehicle in all brepocitinib twice daily groups. Brepocitinib was well tolerated, with adverse events (AEs) occurring at similar rates across groups. One participant in the brepocitinib 1.0% once-daily group developed a treatment-related AE of herpes zoster in the neck area. CONCLUSIONS: Topical brepocitinib was well tolerated but did not result in statistically significant changes compared with vehicle when administered at the doses evaluated to treat signs and symptoms of mild-to-moderate PsO.

Oral Ritlecitinib and Brepocitinib for Moderate-to-Severe Ulcerative Colitis: Results From a Randomized, Phase 2b Study.

BACKGROUND & AIMS: The efficacy and safety of ritlecitinib (oral JAK3/TEC family kinase inhibitor) and brepocitinib (oral TYK2/JAK1 inhibitor) as induction therapy were assessed in patients with active, moderate-to-severe ulcerative colitis. METHODS: This phase 2b, parallel-arm, double-blind umbrella study randomized patients with moderate-to-severe ulcerative colitis to receive 8-week induction therapy with ritlecitinib (20, 70, 200 mg), brepocitinib (10, 30, 60 mg), or placebo once daily. The primary endpoint was total Mayo Score (TMS) at week 8. RESULTS: Of 319 randomized patients, 317 received ritlecitinib (n = 150), brepocitinib (n = 142), or placebo (n = 25). The placebo-adjusted mean TMSs (90% confidence interval) at week 8 were -2.0 (-3.2 to -0.9), -3.9 (-5.0 to -2.7), and -4.6 (-5.8 to -3.5) for ritlecitinib 20, 70, and 200 mg, respectively (P = .003, P < .001, P < .001), and -1.8 (-2.9 to -0.7), -2.3 (-3.4 to -1.1), and -3.2 (-4.3 to -2.1) for brepocitinib 10, 30, and 60 mg, respectively (P = .009, P = .001, P < .001). Estimates (90% confidence interval) for placebo-adjusted proportions of patients with modified clinical remission at week 8 were 13.7% (0.5%-24.2%), 32.7% (20.2%-45.3%), and 36.0% (23.6%-48.6%) for ritlecitinib 20, 70, and 200 mg, respectively, and 14.6% (1.9%-25.7%), 25.5% (11.0%-38.1%), and 25.5% (11.0%-38.1%) for brepocitinib 10, 30, and 60 mg, respectively. Adverse events were mostly mild, and there were no serious cases of herpes zoster infection. Infections were observed with brepocitinib (16.9% [12.5%-23.7%]), ritlecitinib (8.7% [5.2%-13.4%]), and placebo (4.0% [0.2%-17.6%]). One death due to myocardial infarction (ritlecitinib) and 1 thromboembolic event (brepocitinib) occurred; both were considered unrelated to study drug. CONCLUSIONS: Ritlecitinib and brepocitinib induction therapies were more effective than placebo for the treatment of moderate-to-severe active ulcerative colitis, with an acceptable short-term safety profile. CLINICALTRIALS: gov number: NCT02958865.

Population Pharmacokinetics of Oral Brepocitinib in Healthy Volunteers and Patients.

Brepocitinib is a tyrosine kinase 2 and Janus kinase 1 inhibitor in development for treatment of inflammatory autoimmune diseases. This analysis aimed to add to the pharmacokinetic knowledge of the medication, through development of a population pharmacokinetic model and identification of factors that affect drug disposition. Plasma samples from 5 clinical trials were collated, composed of healthy volunteers, patients with psoriasis and patients with alopecia areata taking oral brepocitinib. NONMEM was used to develop a population pharmacokinetic model, and patient demographics were tested as covariates. The final model was a 1-compartment model with first-order absorption. The typical values for apparent clearance and apparent volume of distribution were 18.7 L/h (78% coefficient of variation [CV]) and 136 L (60.5% CV), respectively. Absorption was rapid with an absorption constant of 3.46 h, with an absorption lag of 0.24 hours observed with the oral tablet formulation. The proportional residual error was found to be 52.7% CV in healthy volunteers and 87.5% CV in patients. High-fat meals were associated with a reduction in both the rate (69.9% lower) and extent (28.3% lower) of absorption, while Asian populations had reduced clearance (24.3% lower). Nonlinear pharmacokinetics were observed at doses of 175 mg and above, with a 35.1% higher relative bioavailability at these doses. There were insufficient data to describe this nonlinearity as a continuous relationship. This initial description of the population pharmacokinetics will act as a foundation for the model-informed drug development of brepocitinib and will facilitate future modeling of this medicine. ClinicalTrials.gov numbers NCT02310750 NCT03236493 NCT03656952 NCT02969018 NCT02974868.

Efficacy and safety of topical brepocitinib for the treatment of mild-to-moderate atopic dermatitis: a phase IIb, randomized, double-blind, vehicle-controlled, dose-ranging and parallel-group study.

BACKGROUND: Atopic dermatitis (AD) is a prevalent inflammatory, pruritic skin disease. The Janus kinase (JAK) pathway is a treatment target. OBJECTIVES: To assess the efficacy, safety and pharmacokinetics of topical cream brepocitinib, a small-molecule tyrosine kinase 2 (TYK2)/JAK1 inhibitor, in participants with mild-to-moderate AD. METHODS: In this phase IIb, double-blind, dose-ranging study, participants were randomized to receive one of eight treatments for 6 weeks: brepocitinib 0·1% once daily (QD), 0·3% QD or twice daily (BID), 1·0% QD or BID, 3·0% QD, or vehicle QD or BID. The primary endpoint was the percentage change from baseline in the Eczema Area and Severity Index (EASI) total score at week 6. Adverse events (AEs) were monitored. RESULTS: Overall, 292 participants were enrolled and randomized. The brepocitinib 1% QD and 1% BID groups achieved statistically significantly greater (with multiplicity-adjusted P < 0·05 due to Hochberg's step-up method) percentage reductions from baseline in EASI total score at week 6 [least squares mean (90% confidence interval, CI): QD: -70·1 (-82·1 to -58·0); BID: -75·0 (-83·8 to -66·2)] compared with respective vehicle [QD: -44·4 (-57·3 to -31·6); BID: -47·6 (-57·5 to -37·7)]. There was not a dose-dependent trend in AE frequency, and there were no serious AEs or deaths. CONCLUSIONS: Topical brepocitinib is effective and well tolerated in participants with mild-to-moderate AD. What is already known about this topic? Janus kinase (JAK) inhibitors are in development for treatment of atopic dermatitis (AD). The tyrosine kinase 2 and JAK 1 inhibition by brepocitinib may bring a new profile for topical JAK inhibitors for treatment of mild-to-moderate AD. What does this study add? Topical brepocitinib can provide rapid, effective symptom reduction, and could offer a novel alternative to current topical treatments for mild-to-moderate AD.

The Pharmacokinetics, Metabolism, and Clearance Mechanisms of Abrocitinib, a Selective Janus Kinase Inhibitor, in Humans.

Abrocitinib is an oral once-daily Janus kinase 1 selective inhibitor being developed for the treatment of moderate-to-severe atopic dermatitis. This study examined the disposition of abrocitinib in male participants following oral and intravenous administration using accelerator mass spectroscopy methodology to estimate pharmacokinetic parameters and characterize metabolite (M) profiles. The results indicated abrocitinib had a systemic clearance of 64.2 L/h, a steady-state volume of distribution of 100 L, extent of absorption >90%, time to maximum plasma concentration of ∼0.5 hours, and absolute oral bioavailability of 60%. The half-life of both abrocitinib and total radioactivity was similar, with no indication of metabolite accumulation. Abrocitinib was the main circulating drug species in plasma (∼26%), with 3 major monohydroxylated metabolites (M1, M2, and M4) at >10%. Oxidative metabolism was the primary route of elimination for abrocitinib, with the greatest disposition of radioactivity shown in the urine (∼85%). In vitro phenotyping indicated abrocitinib cytochrome P450 fraction of metabolism assignments of 0.53 for CYP2C19, 0.30 for CYP2C9, 0.11 for CYP3A4, and ∼0.06 for CYP2B6. The principal systemic metabolites M1, M2, and M4 were primarily cleared renally. Abrocitinib, M1, and M2 showed pharmacology with similar Janus kinase 1 selectivity, whereas M4 was inactive. SIGNIFICANCE STATEMENT: This study provides a detailed understanding of the disposition and metabolism of abrocitinib, a Janus kinase inhibitor for atopic dermatitis, in humans, as well as characterization of clearance pathways and pharmacokinetics of abrocitinib and its metabolites.

Ritlecitinib and brepocitinib demonstrate significant improvement in scalp alopecia areata biomarkers.

BACKGROUND: Janus kinase (JAK) inhibitors have shown encouraging results in the treatment of alopecia areata (AA), an autoimmune form of hair loss, in small, uncontrolled studies and case reports. OBJECTIVE: We conducted a biopsy substudy during the randomized, double-blind, placebo-controlled first 24 weeks of a phase 2a clinical trial that evaluated the efficacy and safety of ritlecitinib, an inhibitor of JAK3 and the tyrosine kinase expressed in hepatocellular carcinoma (TEC) kinase family, and brepocitinib, an inhibitor of tyrosine kinase 2 (TYK2)/JAK1 in the treatment of AA. METHODS: Change in biomarkers in lesional scalp biopsy samples between baseline and weeks 12 and 24 was an exploratory end point, and 46 patients participated from the ritlecitinib (n = 18), brepocitinib (n = 16), and placebo (n = 12) groups. Correlations of biomarkers with hair regrowth, measured using the Severity of Alopecia Tool (SALT) score, were also evaluated. CLINICAL TRIAL REGISTRATION: NCT02974868. RESULTS: At week 24, both ritlecitinib and brepocitinib demonstrated improvement exceeding 100% in the lesional scalp transcriptome toward a nonlesional profile. At week 12, the improvements in scalp tissue were greater with brepocitinib than ritlecitinib; however, at week 24, the improvements were greater with ritlecitinib. CONCLUSIONS: For both ritlecitinib and brepocitinib, improvement in the SALT scores was positively associated with expression of TH1 markers and negatively associated with expression of hair keratins. Larger, long-term clinical trials are warranted.

Anti-TL1A Antibody PF-06480605 Safety and Efficacy for Ulcerative Colitis: A Phase 2a Single-Arm Study.

BACKGROUND & AIMS: An immune component of inflammatory bowel disease is up-regulated tumor necrosis factor-like ligand 1A (TL1A). Anti-TL1A antibodies such as PF-06480605, a fully human immunoglobulin G1 monoclonal antibody, may have therapeutic potential. METHODS: This Phase 2a, multicenter, single-arm, open-label study (TUSCANY) evaluated safety, tolerability, efficacy, pharmacokinetics, and immunogenicity in PF-06480605-treated participants with moderate to severe ulcerative colitis (UC). Participants received 500 mg intravenous PF-06480605 every 2 weeks, 7 doses total, with a 3-month follow-up period. Primary safety and efficacy endpoints were the incidence of adverse events (AEs) and week 14 endoscopic improvement (EI) (Mayo endoscopic subscore = 0 or 1), respectively. Secondary endpoints included total soluble TL1A (free/drug-bound) (sTL1A), incidence of anti-drug and neutralizing antibodies, PF-06480605 concentrations, and changes in fecal calprotectin and high-sensitivity C-reactive protein. Histology was assessed at week 14. RESULTS: The study enrolled 50 participants; 42 completed. Of 109 treatment-emergent AEs, 18 were treatment-related. The most common AEs were UC disease exacerbation and arthralgia (6 participants each). Four serious AEs, no deaths, and no malignancies were reported. Week 14 EI was observed in a statistically significant proportion of participants (38.2% [uniformly minimum-variance unbiased estimator, per protocol population]). Minimal histologic disease was observed after treatment (Robarts Histopathology Index ≤5: 33.3%; Geboes Index ≤3.2: 47.6%). sTL1A increase over time from baseline indicated sustained target engagement. Forty-one participants (82%) tested positive for anti-drug antibodies and 5 (10%) for neutralizing antibodies. CONCLUSIONS: PF-06480605 demonstrated an acceptable safety profile and statistically significant EI in participants with moderate to severe UC, warranting further study in a larger participant cohort. Tissue histopathology analyses support this conclusion. TRIAL REGISTRATION NUMBER: https://clinicaltrials.gov/NCT02840721.

A phase 2a randomized, placebo-controlled study to evaluate the efficacy and safety of the oral Janus kinase inhibitors ritlecitinib and brepocitinib in alopecia areata: 24-week results.

BACKGROUND: Alopecia areata (AA) is an autoimmune form of hair loss with limited treatments. OBJECTIVE: To evaluate the efficacy and safety of the Janus kinase inhibitors ritlecitinib and brepocitinib in patients who have AA with ≥ 50% scalp hair loss. METHODS: Patients were randomized to once-daily ritlecitinib, brepocitinib, or placebo. The primary efficacy endpoint was a 24-week change from baseline in the Severity of Alopecia Tool (SALT) score. The key secondary efficacy endpoint was the proportion of patients achieving 30% improvement in SALT score (SALT30). RESULTS: The ritlecitinib, brepocitinib, and placebo groups included 48, 47, and 47 patients, respectively. At week 24, least-squares mean difference from placebo in SALT score change from baseline was 31.1 (95% confidence interval [CI], 18.8-43.5) for ritlecitinib and 49.2 (95% CI, 36.6-61.7) for brepocitinib (P < .0001 for both comparisons with placebo). SALT30 was achieved by 50% (90% CI, 38%-62%) of patients receiving ritlecitinib, 64% (90% CI, 51%-75%) receiving brepocitinib, and 2% (90% CI, 0%-9%) receiving placebo. Two patients experienced a serious adverse event (rhabdomyolysis) in the brepocitinib group only. LIMITATIONS: Only a single-dosage regimen of each study drug was included. CONCLUSION: Treatment with ritlecitinib or brepocitinib for 24 weeks was efficacious and generally well tolerated.

Kinetic-Pharmacodynamic Model of Platelet Time Course in Patients With Moderate-to-Severe Atopic Dermatitis Treated With Oral Janus Kinase 1 Inhibitor Abrocitinib.

The oral Janus kinase 1 (JAK1) inhibitor abrocitinib reduced signs and symptoms of atopic dermatitis (AD) in a placebo-controlled, randomized, double-blind, phase IIb trial (dose range 10-200 mg). A kinetic-pharmacodynamic (K-PD) model consisting of proliferation, maturation, and blood circulation compartments was developed to characterize platelet count changes during the study. The K-PD model consisted of a drug elimination constant, four system parameters describing platelet dynamics, variance terms, correlation, and residual errors. Overall, these patients exhibited mean transit time from progenitor cells to platelets of 8.2 days (longer than the reported megakaryocyte life span), likely arising from JAK1-induced perturbations of platelet progenitor homeostasis. The final model described dose-related platelet count declines until nadir at treatment week 4 and return to baseline levels thereafter. The model was deemed suitable to support the design of subsequent abrocitinib AD trials and indicated limited clinically relevant platelet reductions in the range of doses studied.