Zai Lab (NASDAQ: ZLAB) has reported initial first-in-human results from the global Phase I/1b trial of ZL-1503, its bispecific antibody in development for moderate-to-severe atopic dermatitis. In healthy volunteers, a single dose was associated with suppression of certain biomarkers through Week 12, providing a basis for evaluating longer maintenance intervals. The findings are preliminary and do not establish efficacy in patients.
Biomarker suppression persisted through Week 12
The randomized, double-blind study enrolled 48 healthy volunteers and compared placebo with ZL-1503 doses ranging from 50 mg to 1,000 mg. A single dose of 200 mg or more suppressed phosphorylated STAT6, a biomarker linked to atopic dermatitis signaling, by at least 90%. Suppression was sustained through Week 12.
Several blood biomarkers associated with type 2 inflammation also declined, including TARC, CCL26 and IgE. Pharmacokinetic results showed that drug exposure increased with dose, with a half-life of approximately 40 to 50 days. Zai Lab said this is close to twice the half-life of some approved anti-IL-13 and anti-IL-31 biologics. The company said the results support evaluating a maintenance schedule of once every 12 weeks; dosing frequency and clinical benefit in patients have yet to be established.
ZL-1503 targets IL-13 and IL-31 pathways
Designed by Zai Lab, ZL-1503 uses technology intended to extend serum half-life and targets both IL-13 and the IL-31 receptor alpha. IL-13 is associated with type 2 inflammation and tissue remodeling, while IL-31 is involved in itch and local immune responses. In previously disclosed preclinical animal studies, the candidate reduced itch and inflammation. Animal findings do not establish efficacy in humans.
Participants across dose groups generally tolerated treatment well in the reported study. As of the data cutoff, there were no serious adverse events, dose-limiting toxicities or detectable anti-drug antibodies. Most treatment-emergent adverse events were mild and related mainly to study procedures or unrelated conditions; none led to discontinuation of study drug. As the trial expands and follow-up continues, its safety profile may become clearer.
Patient data expected in the first half of 2027
Zai Lab is continuing dose-escalation evaluation in adults with moderate-to-severe atopic dermatitis. Data from the Part B patient cohort are expected in the first half of 2027. The company has also completed enrollment in a bioavailability bridging study comparing intravenous and subcutaneous administration, with initial Phase I results also expected in 2027.
When the news was released on November 13, Zai Lab shares were quoted at $24.26, down 6.84%. The page's displayed quote was $24.21, down 7.01%. The early trial results and the day's share-price move do not, on their own, establish how the market views the candidate. Key forthcoming data include patient efficacy and safety results, as well as bioavailability findings for the different administration routes.