Zai Lab Advances Atopic Dermatitis Candidate Toward Potential Quarterly Maintenance Dosing

Zai Lab Limited (NASDAQ: ZLAB) has reported promising preliminary results from its first-in-human Phase 1/1b clinical trial of ZL-1503, a bispecific antibody designed to treat moderate-to-severe atopic dermatitis. The trial involved 48 healthy volunteers and demonstrated that ZL-1503 rapidly and sustainably inhibited the IL-13 pathway, with a single dose of 200 mg or higher reducing phosphorylated STAT6, a key signaling biomarker for atopic dermatitis, by at least 90% through Week 12.

The treatment also lowered levels of other inflammatory biomarkers such as TARC, CCL26, and IgE. The study evaluated doses ranging from 50 mg to 1,000 mg in a randomized, double-blind setup.

Pharmacokinetic assessments showed dose-proportional exposure and an extended half-life of approximately 40 to 50 days for ZL-1503, nearly doubling the half-life of several existing anti-IL-13 and anti-IL-31 biologics. This extended half-life supports the potential for once-every-12-week maintenance dosing, a significant advantage over current treatments.

Participants tolerated ZL-1503 well, with no serious adverse events, dose-limiting toxicities, or detectable anti-drug antibodies observed up to the data cutoff. The majority of treatment-emergent adverse events were mild and attributed to study procedures or unrelated illnesses, leading to no interruptions in study drug administration.

Zai Lab's innovative serum half-life extension technology targets both IL-13 and IL-31 receptor alpha. While IL-13 is responsible for type 2 inflammation and tissue remodeling, IL-31 triggers itch and amplifies local immune responses. Preclinical studies conducted earlier this year indicated that ZL-1503 provided rapid itch relief and significantly reduced inflammation in animal models.

Zai Lab plans to further evaluate multiple ascending doses of ZL-1503 in adults with moderate-to-severe atopic dermatitis and anticipates releasing Part B cohort data in the first half of 2027. Additionally, the company has completed enrolling participants in an intravenous-to-subcutaneous bioavailability bridging study, with initial Phase 1 results expected in 2027. As of the report's publication, ZLAB shares were trading down 6.84% at $24.26.