Evommune terminates oral drug’s development in CSU

Evommune Halts EVO756 Development in CSU After Phase IIb Failure

Evommune announced the termination of development for its oral MRGPRX2 antagonist, EVO756, in chronic spontaneous urticaria (CSU) after the drug failed to meet its primary endpoint in a Phase IIb study (NCT06873516). The trial, involving 160 moderate-to-severe antihistamine-refractory CSU patients, showed no benefit in mean change in Urticaria Activity Score over seven days (UAS7) at 12 weeks. Despite this setback, Evommune will continue investigating EVO756 for atopic dermatitis and migraine prophylaxis. The news led to a 37.92% drop in Evommune's stock.

• Evommune's oral MRGPRX2 antagonist, EVO756, failed to achieve its primary endpoint in a Phase IIb study (NCT06873516) for chronic spontaneous urticaria (CSU). The trial, which enrolled 160 moderate-to-severe antihistamine-refractory CSU patients, did not demonstrate a significant mean change in Urticaria Activity Score over seven days (UAS7) at 12 weeks across any tested dose, leading to the discontinuation of its development for this specific indication.
• EVO756 is characterized as a first-in-class, potent, and highly selective oral small molecule antagonist targeting Mas-related G protein-coupled receptor X2 (MRGPRX2), a receptor primarily found on mast cells and peripheral sensory neurons. Despite the CSU setback, Evommune plans to continue the development of EVO756 for other indications, specifically atopic dermatitis (AD) (NCT07150845) and migraine prophylaxis, with data from the AD trial anticipated in late 2026.
• The announcement of EVO756's failure in CSU resulted in a sharp decline in Evommune's stock, dropping 37.92% to $15.63. This contrasts with the positive market reaction to another company asset, EVO301, an IL-18BP fusion protein, which showed promising Phase IIa data in AD earlier in 2026, causing a 70.86% stock increase. The broader atopic dermatitis market is projected for significant growth, from $8.5 billion in 2023 to $22.4 billion by 2033.

Why EVO756's Phase IIb Trial in CSU Missed its Primary Endpoint

Recent clinical research in chronic spontaneous urticaria (CSU) has generated a broad evidence base spanning BTK inhibition, biologics, antihistamine optimization, and novel investigational approaches. The studies summarized below reflect findings from meta-analyses, randomized trials, real-world registries, and case series published in 2025–2026.

• BTK Inhibitors Meta-Analysis (2026): A systematic review and meta-analysis of 5 RCTs (n = 1,489; 71.93% receiving BTK inhibitors, including remibrutinib) demonstrated significantly increased likelihood of achieving UAS7 = 0 at weeks 4, 8, and 12 (RR 5.64, 3.78, and 2.68, respectively; all P ≤ .05), and UAS7 ≤ 6 at the same timepoints (RR 4.30, 2.60, and 2.05; all P < .00001). No significant differences in overall adverse events (RR 1.06; P = .47) or serious AEs (RR 1.17; P = .71) were observed versus placebo.

• Remibrutinib Meta-Analysis (2025): A pooled analysis of 3 RCTs (n = 997) in antihistamine-refractory CSU showed remibrutinib significantly improved disease control versus placebo, with higher odds of achieving UAS7 ≤ 6 (OR 4.38; P < 0.0001) and greater UAS7 reductions (MD −9.45; P < 0.00001). Complete response (UAS7 = 0) did not reach statistical significance (OR 2.14; P = 0.16). Mild infections, nasopharyngitis, petechiae, and URTIs were more frequent with remibrutinib, though overall AEs, serious events, and discontinuation rates were comparable to placebo.

• AAAAI/ACAAI JTFPP Network Meta-Analysis (2025): This guideline-informing systematic review and network meta-analysis encompassed 93 studies (n = 11,398; 83 RCTs and 10 non-randomized studies) evaluating 42 interventions. With high certainty, standard-dose omalizumab (300 mg every 4 weeks) and remibrutinib ranked among the most effective agents across urticaria activity, angioedema activity, and health-related quality of life outcomes. Dupilumab improved urticaria activity, but its effect on quality of life was uncertain and no trials addressed angioedema activity. Cyclosporine demonstrated potential efficacy but carried the highest adverse event burden. Benralizumab, quilizumab, and tezepelumab did not differ significantly from placebo. The safety profile of remibrutinib was characterized as less certain compared to omalizumab.

• Bilastine Up-Dosing Trial (2026): An institution-based, open-label, longitudinal trial in 35 CSU patients uncontrolled on licensed doses of other second-generation antihistamines evaluated bilastine dose escalation. Bilastine 20 mg reduced mean UAS7 from 25.7 to 6.0 at day 14 (P < 0.001), with 16 patients achieving complete resolution. Up-dosing to 40 mg further reduced UAS7 to 1.9 (P < 0.001), achieving complete control in an additional 15 patients; only 4 required 80 mg, with minimal incremental benefit (P = 0.1). Overall, 94% achieved complete disease control. Somnolence (22%) and headache (50%) were reported at higher doses, with generally good tolerability.

• Middle East Omalizumab Real-World Study (2026): A retrospective observational study at a tertiary allergy clinic included 75 adults with CSU of more than 6 months' duration unresponsive to 4-fold doses of H1-antihistamines. Omalizumab produced significant improvement in Urticaria Control Test scores (mean change −7.56; P < .001), with response rates of 84% complete, 13% partial, and 3% poor. Most complete responders achieved control after 1 or 2 doses. Baseline IgE levels did not predict response. Adverse events were infrequent and mild.

• GLP-1 Receptor Agonist Case Series (2026): Two female patients aged 44 and 45 years with long-standing CSU inadequately controlled on high-dose H1-antihistamines initiated GLP-1 receptor agonist therapy (semaglutide or tirzepatide) for metabolic indications. Both patients achieved complete resolution of CSU within 3 weeks of GLP-1RA initiation, with remission persisting for over 6 months. A proposed immunometabolic mechanism links GLP-1 signaling with mast cell activation.

• Dupilumab Case Report and Systematic Review (2026): A case report described a 32-year-old man with refractory CSU, asthma, and eosinophilic gastroenteritis who achieved complete remission of all three conditions with dupilumab, with no reported side effects. A supporting systematic literature review identified 8 studies comprising 25 CSU patients, the majority of whom had coexisting atopic dermatitis or asthma; most achieved symptom control of both urticaria and comorbid Th2 diseases, with only one report of mild side effects across the cohort.

• Probiotics Combined with Antihistamines Meta-Analysis (2025): A systematic review and meta-analysis with trial sequential analysis of 11 clinical trials (n = 1,014) evaluated probiotics combined with antihistamines versus antihistamines alone. Combination therapy significantly improved urticaria relief rate (OR 2.90; P < 0.00001), reduced UAS7 (MD −3.29; P < 0.00001), reduced DLQI (MD −2.95; P < 0.00001), and decreased recurrence rate (OR 0.29; P = 0.0008). The adverse event rate was also significantly lower in the combination arm (OR 0.39; P = 0.007).

Persistent Challenges in Treating Antihistamine-Refractory Chronic Spontaneous Urticaria

Despite advances in understanding CSU pathophysiology, significant treatment gaps remain across the therapeutic hierarchy — from first-line antihistamines to biologics. A substantial proportion of patients fail to achieve complete disease control at each escalation step, and real-world data consistently reveal a disconnect between guideline recommendations and clinical practice.

• Antihistamine failure is common and poorly addressed in practice: H1-antihistamines remain the cornerstone of CSU management, yet they fail to control disease in approximately 10% of patients even at higher-than-licensed doses. Short courses of oral corticosteroids induce remission in only ~50% of cases, and real-world data from the CURE Registry show that 28.6% of patients clinically eligible for treatment escalation (UCT < 12) did not receive step-up therapy — with 10.6% actually stepped down — remaining poorly controlled at follow-up.

• Response rates at each escalation step remain low: Complete response rates following treatment escalation are modest at best: only 5.3% of patients achieved complete response when moving from no treatment to licensed-dose second-generation H1-antihistamines (sgH-AH), 6.0% when escalating to up-dosed sgH-AH, and 28.4% when escalating from any sgH-AH dose to omalizumab — underscoring that only approximately one quarter of patients achieve full disease control with appropriate escalation.

• Omalizumab and cyclosporine have meaningful limitations: While omalizumab is effective in antihistamine-unresponsive patients, optimal treatment duration remains undefined, and a subset of patients experiences limited efficacy, adverse effects, or faces access and cost barriers. Immunosuppressive treatment with cyclosporine is effective in the majority of antihistamine-resistant CSU patients, but its use is constrained by a challenging side effect profile.

• Evidence base for alternative therapies is weak: There is a paucity of controlled trials supporting most nonbiologic, nonantihistamine treatment options. For example, a probiotic intervention study found that 71.1% of patients experienced no symptom improvement, and only 2.6% achieved complete remission — illustrative of the limited efficacy of many alternative approaches evaluated outside of controlled settings.

• Special populations present additional therapeutic complexity: Pediatric patients show limited benefit from fourfold antihistamine updosing beyond double the standard dose, with 18.2% requiring omalizumab and 15.1% experiencing symptom relapse upon dose reduction. In elderly patients, antihistamine use is complicated by drug interactions and heightened risk of adverse effects in the context of comorbidities and polypharmacy.

• Emerging therapies carry unresolved safety concerns: For KIT inhibitors — a class under active investigation — long-term safety data beyond 12 weeks are still lacking. Anti-KIT monoclonal antibodies, based on available preliminary data and mechanistic considerations, may carry a less favorable safety profile compared to omalizumab, and larger controlled trials are warranted to establish an adequate evidence base for these and other emerging treatment modalities.

MRGPRX2 Antagonists: A Crossroads in Chronic Urticaria

Evommune's decision to terminate the development of its oral MRGPRX2 antagonist, EVO756, for chronic spontaneous urticaria (CSU) following a Phase IIb failure sends a clear signal across the pharmaceutical landscape. The Mas-related G protein-coupled receptor X2 (MRGPRX2) has long been identified as a key non-IgE-mediated mast cell activation receptor, with its expression and agonists, such as substance P, correlating with disease severity in CSU and atopic dermatitis. The mechanism of action—inhibiting mast cell degranulation and the release of pro-inflammatory mediators—is well-supported by preclinical literature, with several small molecule MRGPRX2 antagonists demonstrating efficacy in various in vitro and in vivo models.

However, the clinical reality for EVO756 in CSU proved challenging. This outcome underscores the inherent complexities of CSU, a multifactorial disease involving both IgE-dependent and independent pathways. Studies have even identified gain-of-function mutations in MRGPRX2 that contribute to enhanced disease activity, suggesting that a single antagonist might not universally address the diverse patient population, particularly those refractory to standard antihistamines. This failure, coupled with the prior halting of another MRGPRX2 antagonist (EP-262) in CSU development, prompts a critical re-evaluation of the target's overall potential in this specific indication.

Evommune's strategic pivot to continue investigating EVO756 in atopic dermatitis and migraine prophylaxis is a logical next step. MRGPRX2 is also implicated in the pathogenesis of atopic dermatitis, and other antagonists have shown promise in AD models. This suggests that while the target may be valid, its optimal therapeutic application might lie in different disease contexts or patient subsets. For the broader industry, this event will likely:

• Intensify scrutiny on other MRGPRX2 antagonist programs, demanding more robust clinical evidence and potentially better patient stratification strategies.

• Accelerate focus on alternative emerging mechanisms for refractory CSU, such as BTK inhibitors and anti-KIT antibodies, which are advancing rapidly through clinical trials.

Ultimately, this setback serves as a reminder of the high bar for innovation in complex inflammatory diseases and the continuous need to refine our understanding of target biology in specific clinical settings.