Population Pharmacokinetics of Oral Brepocitinib in Healthy Volunteers and Patients

Therapeutic inhibition of the JAK-STAT pathway in the treatment of inflammatory bowel disease

Inflammatory bowel disease (IBD) encompasses a group of non-specific chronic intestinal inflammatory conditions of unclear etiology. The current treatment and long-term management primarily involve biologics. Nevertheless, some patients experience treatment failure or intolerance to biologics [1], making these patients a primary focus of IBD research. The Janus kinase (JAK)-Signal Transducers and Activator of Transcription (STAT) signal transduction pathway is crucial to the regulation of immune and inflammatory responses [2], and plays an important role in the pathogenesis of IBD. JAK inhibitors alleviate IBD by suppressing the transmission of JAK-STAT signaling pathway. As the first small-molecule oral inhibitor for IBD, JAK inhibitors greatly improved the treatment of IBD and have demonstrated significant efficacy, with tofacitinib and upadacitinib being approved for the treatment of ulcerative colitis (UC) [3]. JAK inhibitors can effectively alleviate intestinal inflammation in IBD patients who have failed to receive biologics, which may bring new treatment opportunities for refractory IBD patients. This review aims to elucidate the crucial roles of JAK-STAT signal transduction pathway in IBD pathogenesis, examine its role in various cell types within IBD, and explore the research progress of JAK inhibitors as therapeutic agents, paving the road for new IBD treatment strategies.

The Metabolism and Disposition of Brepocitinib in Humans and Characterization of the Formation Mechanism of an Aminopyridine Metabolite

Brepocitinib is an oral once-daily Janus kinase 1 and Tyrosine kinase 2 selective inhibitor currently in development for the treatment of several autoimmune disorders. Mass balance and metabolic profiles were determined using accelerator mass spectrometry in six healthy male participants following a single oral 60 mg dose of 14C-brepocitinib (∼300 nCi). The average mass balance recovery was 96.7% ± 6.3%, with the majority of dose (88.0% ± 8.0%) recovered in urine and 8.7% ± 2.1% of the dose recovered in feces. Absorption of brepocitinib was rapid, with maximal plasma concentrations of total radioactivity and brepocitinib achieved within 0.5 hours after dosing. Circulating radioactivity consisted primarily of brepocitinib (47.8%) and metabolite M1 (37.1%) derived from hydroxylation at the C5' position of the pyrazole ring. Fractional contributions to metabolism via cytochrome P450 enzymes were determined to be 0.77 for CYP3A4/5 and 0.14 for CYP1A2 based on phenotyping studies in human liver microsomes. However, additional clinical studies are required to understand the potential contribution of CYP1A1. Approximately 83% of the dose was eliminated as N-methylpyrazolyl oxidative metabolites, with 52.1% of the dose excreted as M1 alone. Notably, M1 was not observed as a circulating metabolite in earlier metabolic profiling of human plasma from a multiple ascending dose study with unlabeled brepocitinib. Mechanistic studies revealed that M1 was highly unstable in human plasma and phosphate buffer, undergoing chemical oxidation leading to loss of the 5-hydroxy-1-methylpyrazole moiety and formation of aminopyrimidine cleavage product M2. Time-dependent inhibition and trapping studies with M1 yielded insights into the mechanism of this unusual and unexpected instability. SIGNIFICANCE STATEMENT: This study provides a detailed understanding of the disposition and metabolism of brepocitinib, a JAK1/TYK2 inhibitor for atopic dermatitis, in humans as well as characterization of clearance pathways and pharmacokinetics of brepocitinib and its metabolites.

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.

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.

Pharmacokinetic Profile of Brepocitinib with Topical Administration in Atopic Dermatitis and Psoriasis Populations: Strategy to Inform Clinical Trial Design in Adult and Pediatric Populations

INTRODUCTION

Topical brepocitinib, a tyrosine kinase (TYK)2/Janus kinase (JAK)1 inhibitor, is in development for psoriasis (PsO) and atopic dermatitis (AD). Quantitative analyses of prior clinical trial data were used to inform future clinical trial designs.

METHODS

Two phase 2b studies in patients with AD and PsO were used to characterize the amount of topical brepocitinib and the resultant systemic trough concentration (CTrough) using a linear mixed-effects regression (LMER). This model was used to predict brepocitinib systemic CTrough for higher treated body surface areas (BSAs) in adults and children. Information from non-clinical and clinical trials with oral brepocitinib was leveraged to set safety thresholds. This combined approach was used to inform future dose-strength selection and treated BSA limits.

RESULTS

Data from 256 patients were analyzed. Patient type, dose strength, and frequency had significant impacts on the dose-exposure relationship. Systemic concentration in patients with PsO was predicted to be 45% lower than in patients with AD from the same dose. When topically applied to the same percentage BSA, brepocitinib systemic exposures are expected to be comparable between adults and children. The systemic steady-state exposure after 3% once daily and twice daily (2 mg/cm2) cream applied to less than 50% BSA in patients with AD and PsO, respectively, maintains at least a threefold margin to non-clinical safety findings and clinical hematologic markers.

CONCLUSION

The relationship between the amount of active drug applied and brepocitinib systemic CTrough, described by LMER, may inform the development strategy for dose optimization in the brepocitinib topical program.

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.