FormalPara Key Summary Points

Why carry out this study?

Atopic dermatitis (AD) is a chronic inflammatory disease characterized by eczematous lesions and severe pruritus that reduce patient quality of life.

The Mas-related G protein-coupled receptor X2 (MRGPRX2) could be implicated in AD pathophysiology via regulation of mast cell degranulation.

A randomized, placebo-controlled trial was conducted to evaluate the safety, tolerability, and pharmacodynamics of the MRGPRX2 antagonist EP262 in patients with AD.

What was learned from the study?

Although EP262 was well tolerated in patients with AD, no meaningful changes in gene expression, skin thickness, or efficacy measures were observed compared with placebo.

These data suggest that MRGPRX2 antagonism may not be a viable treatment approach for the treatment of AD, although additional studies are warranted.

Introduction

Atopic dermatitis (AD) is a chronic, heterogeneous, relapsing inflammatory dermatologic disease characterized by impaired skin barrier function, eczematous lesions, and severe pruritus, compromising both patients’ and caregivers’ quality of life [1, 2]. Mast cells (MCs) are innate immune cells that, upon activation and subsequent degranulation via immunoglobulin E (IgE)-dependent and -independent pathways, can initiate inflammatory responses that cause pruritus, pain, and vasodilation [3, 4]. One key mediator of IgE-independent degranulation of MCs is Mas-related G protein-coupled receptor X2 (MRGPRX2), which is predominantly expressed on MCs and is activated by a variety of agonists, such as neuropeptides (e.g., substance P [SP]) [3, 4].

Patients with AD have shown increased numbers of MCs in the skin compared with healthy controls, with numbers of MCs in AD lesions significantly correlating to disease severity [5,6,7]. Additionally, elevated MRGPRX2 activity, as well as elevated levels of MRGPRX2 ligands (i.e., SP) in skin and blood have been reported in patients with AD [5, 7], suggesting a pathogenic role for MRGPRX2-mediated, IgE-independent MC activation and subsequent skin inflammation in AD.

EP262 (INCB000262) is a potent, small-molecule antagonist of the human MRGPRX2 receptor [8]. Daily oral administration of EP262 significantly diminished AD development in a mouse model of AD using MRGPRX2 knock-in mice expressing the human receptor [9]. A first-in-human, phase 1 study demonstrated that all evaluated doses of EP262 were well tolerated, with no moderate or severe treatment-emergent adverse events (TEAEs) reported [10]. The aims of the phase 2 study presented here were to evaluate the safety, tolerability, pharmacodynamics, and efficacy of EP262 compared with placebo in patients with AD.

Methods

Patients and Study Design

EASE (NCT06144424) was a phase 2a, randomized, double-blind, placebo-controlled study conducted at ten sites in the US and Canada. Eligible patients were aged 18 to 80 years with a clinically confirmed diagnosis of active AD for ≥ 1 year, affected body surface area (BSA) of 3% to 20%, a validated Investigator’s Global Assessment for AD (vIGA-AD) score ≥ 3 at screening and Day 1, and no significant AD flares ≥ 4 weeks before screening. Patients were also required to have used a protocol-permitted, non-urea emollient for ≥ 1 week before baseline; patients agreed to continue using the same emollient daily at the same frequency throughout the study. Exclusion criteria included other active skin diseases associated with chronic pruritus, clinically infected AD that required antibiotic therapy, use of dupilumab within 26 weeks of baseline, use of other monoclonal antibodies within 4 months or five half-lives (whichever was longer), use of other systemic therapy for AD (including oral Janus kinase inhibitors) or phototherapy within 4 weeks of baseline, and use of topical medications for AD within 1 week of baseline.

Following a screening period (7–30 days), eligible patients were randomized via an interactive web response system in a 2:1 ratio to receive 150 mg EP262 or placebo once daily orally for 6 weeks. All patients who completed the treatment period or discontinued the study drug had a follow-up visit approximately 4 weeks (± 3 days) following the last dose of study drug. The study sponsor, investigators, site staff, and patients were blinded to the patients’ assigned treatment until the database lock.

This study was conducted in accordance with ethical principles of the Declaration of Helsinki, International Council for Harmonisation, and Good Clinical Practice guidelines. Protocols were approved by the institutional review board or ethics committee (Advarra, Inc., Columbia, MD, USA). All patients provided written informed consent before the start of the study.

Assessments

The primary endpoint was safety and tolerability, as assessed by the type, frequency, and severity of TEAEs and the change from baseline in clinical laboratory parameters. The pharmacodynamic effects of EP262 were evaluated as a secondary endpoint: change from baseline to Week 6 in gene expression signature and skin histology from skin punch biopsies. A panel of 67 genes involved in AD and MRGPRX2 pathways was evaluated using RNA sequencing. These included mast cell genes as well as any other genes that changed in response to EP262 treatment in the murine AD model. For gene expression and histology, lesional skin biopsy samples at baseline and Week 6 were compared with nonlesional reference samples at baseline.

Disease severity assessments, including the Eczema Area and Severity Index (EASI), vIGA-AD, and Peak Pruritus Numerical Rating Scale (PP-NRS), were assessed as exploratory endpoints. For PP-NRS, patients rated their worst level of itch over the previous 24 h on a scale of 0 (no itch) to 10 (worst imaginable itch); assessments were performed in the morning throughout the study, and scores were calculated as the weekly average of the 7 daily scores.

Statistical Analysis

No formal sample size calculations were made. The sample size was selected to provide adequate information on the safety, tolerability, and pharmacodynamics of EP262 over 6 weeks. Analyses were conducted in patients who received ≥ 1 dose of study drug.

Safety and pharmacodynamic endpoints were analyzed descriptively. Differentially expressed genes had an absolute log2 fold change > 1.5 and a Bonferroni-adjusted P value < 0.05 using the Wilcoxon signed rank test or paired Student’s t-test. Changes in epidermal thickness and number of cells positive for MRGPRX2, tryptase, filaggrin, and major basic protein (MBP) from baseline to Week 6 were analyzed using a covariance model with fixed effects for treatment group and covariate adjustment for the reference values.

Results

Patients

A total of 32 patients were randomized (EP262, n = 21; placebo, n = 11), and 30 (93.8%) completed treatment (Fig. 1). Two patients discontinued from EP262 (patient withdrawal and other). Overall, the median (range) patient age was 41.0 (18–70) years; most patients were female (59.4%) and White (68.8%). The median (range) disease duration was 18.5 (1–51) years, and 81.3% of patients had received prior treatment for AD. Mean (SD) baseline EASI scores were 6.7 (3.1) and 6.7 (4.2) for the EP262 and placebo groups, respectively. Demographics and baseline disease characteristics were generally similar across treatment groups (Table 1).

Fig. 1
Fig. 1
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Patient disposition. QD, once daily. a Reason stated was incarceration

Table 1 Patient demographics and baseline characteristics
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Safety

TEAEs were reported in four patients (19.0%) who received EP262 and seven patients (63.6%) who received placebo; none were considered treatment-related. No specific TEAE was reported in > 1 patient receiving EP262 (Table 2). No grade ≥ 3 or serious TEAEs were observed, and no TEAEs led to dose interruptions or treatment discontinuations. Treatment with EP262 did not result in any meaningful changes in hematology, chemistry, or coagulation parameters; values outside of normal ranges were infrequent. No TEAEs were associated with laboratory test results.

Table 2 Safety summary
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Gene Expression

Of the 67 genes analyzed in either treatment group, none met the criteria for differential expression between baseline lesional or nonlesional samples and those from Week 6 lesional samples. Lesional skin transcriptomic profiles showed a nominal shift toward that of nonlesional skin in both treatment groups (Fig. 2). Genes typically observed to be dysregulated in patients with AD (e.g., upregulated keratin 16 and involucrin; downregulated keratin 77, filaggrin, and late cornified envelope 2B) were differentially expressed in lesional versus nonlesional skin at baseline, but no changes between sample types were observed after treatment in either group.

Fig. 2
Fig. 2
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Changes in the lesional AD transcriptome from baseline to Week 6. AD, atopic dermatitis; B, baseline; DR, genes downregulated versus nonlesional B; FC, fold change; IQR, interquartile range; QD, once daily; UR, genes upregulated versus nonlesional B. Data represented as mean, IQR, and outliers. Only patients with a Week 6 biopsy are included in the analysis

Skin Histology

There was no difference between groups in mean (SE) change from baseline in epidermal thickness of lesional skin (EP262, − 31.7 [18.8] µm; placebo, 14.4 [21.4] µm; least squares mean difference [SE], − 40.3 [29.6]; P = 0.1855; Fig. 3). Changes in MRGPRX2-, tryptase-, filaggrin-, and MBP-positive cells were minimal in both treatment groups, with no meaningful differences between groups; the percentage of MBP cells was low, which may affect interpretation.

Fig. 3
Fig. 3
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Epidermal thickness and histologic biomarkers. B, baseline; DAPI, 4’,6-diamidino-2-phenylindole; L, lesional sample; MBP, major basic protein; MRGPRX2, Mas-related G protein-coupled receptor X2; NL, nonlesional sample; QD, once daily. Values for each mean target-specific positive cell count (top) and mean total nucleated (DAPI positive) cell count (bottom) are shown for histologic markers

Efficacy

There were no observed improvements with EP262 versus placebo in measures of disease severity, extent, or itch (Table 3). The mean [SE] percentage change from baseline in EASI scores at Week 6 among patients who received EP262 versus placebo were − 14.9% (27.0%) and − 40.7% (17.2%), respectively. The proportions of patients who achieved a vIGA-AD score of 0 or 1 at Week 6 with a ≥ 2-point improvement from baseline were 21.1% in the EP262 group and 27.3% in the placebo group. The percentage change from baseline in average daily PP-NRS scores at Week 6 was also similar among patients who received EP262 versus placebo (mean [SE], − 26.7% [11.4%] vs − 25.1% [10.4%]).

Table 3 Efficacy outcomes at Week 6
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Discussion

MCs and MRGPRX2 have been implicated in the pathophysiology of AD skin lesions and disease severity [7, 11]. EP262, a potent, small-molecule antagonist of the human MRGPRX2 receptor [8], has demonstrated safety and tolerability in a first-in-human, phase 1 clinical study involving healthy participants [10].

Results of the phase 2a EASE study showed EP262 to be well tolerated; overall TEAE incidence was lower among patients in the EP262 cohort compared with patients receiving placebo. All TEAEs were mild or moderate in severity; none were treatment-related or serious, nor did any lead to dose interruptions or treatment discontinuation. Additionally, no clinically meaningful trends were observed in laboratory assessments.

No substantial changes in efficacy outcomes or expression of genes associated with AD were observed after treatment with EP262. Multiple factors may explain the lack of observed treatment effects. Although MRGPRX2-mediated MC activation may contribute to disease pathogenesis, inhibition of a single pathway may be insufficient to achieve measurable clinical improvement, given the heterogeneous nature of AD [1]. In addition, the mean baseline EASI score of 6.7 was low, despite patients meeting the enrollment criteria of vIGA-AD ≥ 3; this may have limited the ability to detect measurable treatment-related improvement during the study period. The 6-week treatment duration may also have been insufficient to capture the full therapeutic potential of MRGPRX2 blockade. This timeframe was selected because it was considered sufficient to demonstrate changes in pharmacodynamic measures and provide trends in efficacy based on the anticipated rapid onset of EP262 to directly block activation of MRGPRX2; however, a longer treatment duration may be required to fully characterize treatment effects, particularly in a population with relatively mild disease. Future studies with extended treatment duration may help clarify whether delayed clinical benefits emerge over time.

Limitations of this study include the relatively mild disease severity of patients at baseline and the short treatment duration, which may have led to the absence of detectable treatment effects. Another limitation was the relatively small sample size.

To the best of our knowledge, this is the first report of a clinical study that examined the efficacy of MRGPRX2 antagonism in patients with AD. A planned second part of a phase 2 study evaluating EP262 for chronic spontaneous urticaria (NCT06077773) was terminated because of in vivo preclinical toxicology findings in animals [12]. Nevertheless, EP262 showed a favorable safety and tolerability profile in both the present phase 2a study in AD and the previously reported phase 1 study in healthy participants [10].

Conclusions

Consistent with a prior study in healthy participants, EP262 was well tolerated in patients with AD, with few TEAEs reported. Although MCs may be a factor in AD pathophysiology, the lack of efficacy observed with EP262 versus placebo in the EASE study suggests that their activation by MRGPRX2 does not play a pivotal role in AD pathophysiology. Although predicted target plasma concentrations were achieved by Week 1 of the study (data not shown), it remains plausible that EP262 did not adequately engage the target in the skin to see meaningful clinical differences. Further investigations with larger patient populations may be warranted to expand on these results.