The randomized, double-blind Phase 1 trial enrolled 64 healthy participants (24 single-dose IV, 24 single-dose SC, 16 multiple-dose IV), demonstrating >99% TL1A inhibition in 86% of participants during induction and >90% in 90% during maintenance with a 74-day terminal half-life. Treatment was well tolerated with no serious TEAEs and only mild injection-site reactions. Anti-drug antibodies appeared in 57% of participants overall but had no impact on pharmacokinetics or safety.

The global Phase 2b XENITH-UC study is enrolling ~220 patients across three active arms and one placebo arm using asymmetric randomization, targeting clinical remission by modified Mayo score at week 12. Enrollment remains on schedule for a blinded interim analysis around year-end 2026 and full primary endpoint data in H2 2027. A single 12-week subcutaneous maintenance dose reflects the potential best-in-market dosing profile.

XmAb412 is a first-in-class bispecific antibody targeting TL1A and IL23p19, designed with XenLock™ Fab domains for high affinity, extended half-life, and low immunogenicity. Preclinical characterization will be presented at DDW, and a first-in-human dose-escalation study in healthy participants is expected to begin in Q3 2026 to assess pharmacokinetics and pharmacodynamics. The program aims to advance multi-specific biologics for autoimmune and inflammatory diseases in 2027.

Xencor will host a webcast on May 5 at 8:00 a.m. EDT to review the final Phase 1 XmAb942 data and preclinical XmAb412 findings, with a live Q&A session. The webcast can be accessed via the investors section of Xencor’s website, and a recording will be available for 30 days. Management intends to discuss implications for the TL1A franchise and development milestones.