Zai Lab Showcases ZL-1503’s Rapid Itch Relief and Anti-Inflammatory Effects in Atopic Diseases
Zai Lab Limited has unveiled new preclinical findings highlighting the therapeutic promise of ZL-1503, an investigational bispecific antibody designed to simultaneously target IL-13 and IL-31Rα pathways. The data, presented at the IMMUNOLOGY2026 conference in Boston, provide compelling evidence that this dual-targeting approach may offer sustained relief from itching (pruritus) and inflammation associated with atopic diseases, including moderate-to-severe atopic dermatitis.
Atopic diseases are driven by complex immune responses, with cytokines such as interleukin-13 (IL-13) and interleukin-31 (IL-31) playing central roles. IL-13 is known to promote type 2 inflammation, contributing to tissue remodeling and disease progression, while IL-31 is strongly associated with itch and amplifies local immune responses. Together, these molecules fuel the persistent itch-scratch-inflammation cycle that characterizes conditions like atopic dermatitis, asthma, allergic rhinitis, and conjunctivitis. Despite the availability of existing biologics, many therapies target only one pathway, leaving a significant unmet need for treatments capable of addressing both inflammation and itch simultaneously.
ZL-1503 was specifically engineered to meet this need. By acting as a bispecific antibody, it blocks both IL-13 and IL-31Rα-mediated signaling at the same time. This dual inhibition is intended to disrupt the interconnected biological mechanisms driving atopic disease, potentially offering more comprehensive and durable symptom control than single-target therapies.
The preclinical study presented at IMMUNOLOGY2026 evaluated the efficacy and safety of ZL-1503 across a range of disease models. One of the most notable findings was the durability of its effect. A single intravenous dose—administered at varying levels of 0.3, 3, and 10 mg/kg—resulted in sustained, dose-dependent suppression of both IL-31-induced scratching and IL-13-driven signaling activity, as measured by pSTAT6. Remarkably, these effects were maintained over a 112-day observation period, suggesting that ZL-1503 could potentially enable less frequent dosing compared to currently available biologics.
Beyond itch suppression, ZL-1503 demonstrated broad anti-inflammatory activity. In preclinical models of asthma, allergic rhinitis, and conjunctivitis triggered by controlled allergen exposure, a single 10 mg/kg dose led to significant improvements in lung function, reduced airway inflammation, and alleviation of upper respiratory and ocular symptoms. These findings indicate that the antibody’s benefits may extend across multiple atopic conditions, reinforcing its potential as a versatile therapeutic option.
Further supporting these results, detailed molecular and tissue-level analyses were conducted. Transcriptomic studies revealed widespread suppression of T helper 2 (TH2)-related inflammatory pathways, which are central to the pathogenesis of atopic diseases. Histopathological examinations showed reduced immune cell infiltration and decreased mast cell activation in key tissues, including the lungs, nasal mucosa, and conjunctiva. Together, these findings provide mechanistic insight into how ZL-1503 exerts its effects at the site of inflammation, confirming that its activity goes beyond symptom control to address underlying disease processes.
Equally important is the safety profile observed in these studies. ZL-1503 demonstrated favorable nonclinical safety across all tested doses, with no significant adverse findings reported. This safety profile supports its continued development and transition into human clinical trials.
Building on these promising preclinical results, Zai Lab initiated a first-in-human Phase 1/1b clinical trial of ZL-1503 in December 2025. The study is being conducted across multiple regions, including Australia, New Zealand, and China, and is enrolling both healthy volunteers and adult patients with moderate-to-severe atopic dermatitis. The trial aims to evaluate the antibody’s safety, tolerability, pharmacokinetics, and preliminary efficacy in humans. Initial clinical data from this study are anticipated in the second half of 2026.
According to Zai Lab’s leadership, the breadth and durability of ZL-1503’s activity reinforce confidence in its potential as a first-in-class therapy. By addressing both itch and inflammation in a sustained manner, the antibody could represent a meaningful advancement for patients who continue to experience inadequate symptom control with existing treatments. The possibility of less frequent dosing may also improve patient convenience and adherence, further enhancing its clinical value.
The development of ZL-1503 reflects a broader trend in immunology and drug development toward multi-targeted therapies that can more effectively address complex disease biology. In atopic diseases, where multiple signaling pathways interact to drive symptoms and progression, such approaches may offer significant advantages over traditional single-target strategies.
As research continues, the upcoming clinical data will be critical in determining whether the promising results observed in preclinical models translate into meaningful benefits for patients. If successful, ZL-1503 could potentially redefine the treatment landscape for atopic dermatitis and other IL-13- and IL-31-driven conditions, offering faster onset of action, improved efficacy, and longer-lasting relief.
In summary, the data presented at IMMUNOLOGY2026 highlight ZL-1503 as a highly promising investigational therapy with the potential to address key unmet needs in atopic disease management. Its dual-targeting mechanism, durable efficacy, broad anti-inflammatory effects, and favorable safety profile collectively support its advancement in clinical development. With ongoing trials underway and results expected later this year, Zai Lab is positioning ZL-1503 as a potential breakthrough in the treatment of chronic inflammatory and pruritic diseases.
About ZL-1503
ZL-1503 is a potential first-in-class bispecific antibody targeting IL-13 and IL-31Rα engineered by Zai Lab’s in-house discovery engine to simultaneously suppress both inflammatory and pruritogenic (itch-causing) pathways implicated in AD and other IL-13 and IL-31-driven diseases, potentially offering faster onset of action and superior efficacy compared to single-pathway inhibition.
ZL-1503 is currently being evaluated in the ongoing global Phase 1/1b clinical trial evaluating its safety, tolerability, pharmacokinetics, and efficacy. This clinical advancement is supported by preclinical studies in which ZL-1503 demonstrated the ability to simultaneously suppress inflammatory and pruritogenic pathways implicated in AD.
Zai Lab Limited (NASDAQ: ZLAB; HKEX: 9688) is an innovative, research-based, commercial-stage biopharmaceutical company based in China and the United States. We are focused on discovering, developing, and commercializing innovative products that address medical conditions with significant unmet needs in the areas of oncology, immunology, neuroscience, and infectious disease. Our goal is to leverage our competencies and resources to positively impact human health.
