Beyond Th2: Single-Dose Aletekitug Targets IL-18 to Deliver Sustained Clinical and Molecular Remission in Atopic Dermatitis

Highlights

Durable Clinical Efficacy from a Single Dose

A single intravenous infusion of aletekitug (2 mg/kg) resulted in a significant reduction in the Eczema Area and Severity Index (EASI) score at Week 12 (-68.3%), with clinical benefits sustained through Week 24.

Broad Immunomodulatory Impact

Transcriptomic analysis demonstrated that aletekitug modulates immune mechanisms beyond the traditional Type 2 (T2) axis, impacting Th1, Th17, and Th22 pathways, effectively shifting lesional skin toward a non-lesional molecular profile.

Improvement in Patient-Reported Outcomes

Beyond physical clearance, patients reported substantial improvements in itch intensity, sleep quality, and overall quality of life, highlighting the drug’s impact on the holistic disease burden.

Background: The Heterogeneity of Atopic Dermatitis

Atopic dermatitis (AD) is a chronic, relapsing inflammatory skin disease characterized by intense pruritus and eczematous lesions. For years, the therapeutic landscape was dominated by the Th2 paradigm, focusing on cytokines like IL-4 and IL-13. While biologics targeting these pathways have revolutionized care, a significant subset of patients remains refractory or experiences incomplete clearance. This suggests that AD is not a monolithic T2-driven disease but rather a complex interplay of multiple immune axes.

Interleukin-18 (IL-18), a member of the IL-1 family, has emerged as a key mediator in this complexity. Produced by keratinocytes and myeloid cells, IL-18 is a pleiotropic cytokine that induces the production of IFN-gamma (Th1) but can also promote Th2 and Th17 responses depending on the local cytokine milieu. Elevated levels of IL-18 are found in the serum and skin of AD patients, correlating with disease severity. Aletekitug, a potent anti-IL-18 monoclonal antibody, was designed to neutralize this upstream driver and potentially provide a more comprehensive modulation of the AD immune landscape.

Study Design and Methodology

This phase 1/2, randomised, double-blind, parallel-group, placebo-controlled study evaluated the safety and efficacy of aletekitug in 34 adults with moderate-to-severe AD. The cohort included both biologic-naïve patients and those who were inadequate responders or intolerant to dupilumab, representing a clinically challenging population.

Participants were randomized in a 2:1 ratio to receive either a single intravenous (IV) dose of aletekitug at 2 mg/kg (n = 23) or a placebo (n = 11). The primary endpoint was the percentage change from baseline (PCFB) in the EASI score at Week 12. Secondary endpoints included the proportion of patients achieving EASI-75, changes in the Peak Pruritus Numerical Rating Scale (NRS), and safety assessments. Crucially, the study also utilized skin biopsies for transcriptomic analysis to assess the molecular impact of IL-18 inhibition on the skin’s inflammatory signature.

Key Findings: Clinical Efficacy and Durability

The study met its primary endpoint with high statistical confidence. At Week 12, the aletekitug group showed a posterior median PCFB in EASI score of -68.3% (95% CrI: -79.68, -56.68), compared to -32.9% (95% CrI: -45.74, -21.10) for the placebo group.

One of the most striking observations was the durability of the response. Despite only receiving a single dose at the start of the study, the clinical benefits in the aletekitug group were maintained through Week 24. This suggests a prolonged pharmacodynamic effect or perhaps a fundamental resetting of the inflammatory threshold in these patients. In contrast, the placebo group did not show comparable sustained improvement.

Patient-Reported Outcomes (PROs)

Clinical scores were mirrored by significant improvements in quality of life. Patients treated with aletekitug experienced:
– Rapid and sustained reduction in itch (Pruritus NRS).
– Improved sleep quality and reduced fatigue.
– Significant improvements in the Dermatology Life Quality Index (DLQI).

Molecular Insights: Shifting the Transcriptomic Profile

The transcriptomic analysis provided a mechanistic explanation for the observed clinical success. Aletekitug treatment led to a significant reduction in the expression of genes associated with various inflammatory axes, not limited to T2 immunity.

Lesional skin biopsies at Week 12 and Week 24 showed a movement toward a non-lesional molecular profile. Specifically, there was a down-regulation of markers associated with Th1 (IFNG), Th17 (S100A proteins), and Th22 (IL22) pathways. This broad-spectrum immunomodulation differentiates aletekitug from current T2-specific inhibitors and may explain its efficacy in patients who have failed prior biologics. The data suggests that IL-18 acts as a ‘master switch’ that orchestrates multiple inflammatory cascades in the skin.

Safety and Tolerability

Aletekitug was well tolerated throughout the 24-week period. There were no serious adverse events (SAEs) reported, and no patients discontinued the study due to adverse events. The most common side effects were mild and consistent with those typically seen in biologic trials for AD, such as nasopharyngitis or mild injection-site reactions. Importantly, no safety signals related to systemic immunosuppression or unusual infections were identified, which is a critical consideration for upstream cytokine inhibitors.

Expert Commentary

The results of this study are significant for several reasons. First, the efficacy of a single dose over a 24-week period is highly unusual in the treatment of chronic inflammatory skin diseases, where most biologics require bi-weekly or monthly administration. This could potentially translate into better patient adherence and reduced healthcare costs.

Second, the molecular data reinforces the idea that IL-18 is a viable therapeutic target for ‘difficult-to-treat’ AD. By modulating Th1 and Th17/22 pathways in addition to Th2, aletekitug addresses the underlying immune heterogeneity that often leads to treatment failure with Th2-exclusive agents. However, clinicians must note that this was a small, early-phase study. Larger Phase 3 trials will be necessary to confirm these findings across more diverse populations and to establish the long-term safety profile of IL-18 inhibition.

Conclusion

The Phase 1/2 study of aletekitug marks a promising step forward in the precision treatment of atopic dermatitis. By targeting IL-18, the therapy achieves broad immunomodulatory effects that translate into deep and durable clinical responses. As the field moves toward more personalized medicine, aletekitug offers a potential new pathway for patients who require more than just T2 inhibition to achieve clear skin and a better quality of life.

Funding and Clinical Trial Information

This study was funded by Sanofi and Regeneron Pharmaceuticals, Inc.
ClinicalTrials.gov Identifier: NCT04642430.

References

Ellis J, Fortunato L, Wajdner H, et al. Clinical and Molecular Effect of the Anti-IL-18 Antibody Aletekitug in Adults With Atopic Dermatitis. Allergy. 2026 Feb;81(2):539-551. doi: 10.1111/all.70172. Epub 2025 Dec 18. PMID: 41410194.