Abstract Background Dysregulated cytokine networks are a major driver of immune-mediated inflammatory diseases (IMIDs), such as inflammatory bowel disease and psoriasis. TL1A and IL-23 are pivotal cytokines in these pathologies. TL1A promotes Th1/Th17 differentiation and fibroblast activation, contributing to fibrosis and chronic inflammation. IL-23 sustains pathogenic Th17 cells and drives tissue damage. Dual inhibition of TL1A and IL-23 may yield synergistic effects by disrupting complementary inflammatory pathways. Here, we describe the design and preclinical evaluation of ALX001, a humanized bispecific antibody (bsAb) targeting TL1A and IL-23, engineered to enhance therapeutic potency in IMIDs. Methods Target engagement was characterized by competition ELISA. Blockade activities on TL1A and IL-23 signaling pathways were evaluated in TF-1 apoptosis assay and IL-23 reporter cell assay, respectively. The synergistic effect of dual-target inhibition was assessed in human PBMCs by measuring IL-17/IL-22 release. In vivo efficacy was evaluated in TNBS-induced colitis model and cytokine-induced psoriasis model, examining DAI (Disease Activity Index), histopathology, and cytokine levels. Pharmacokinetics (PK) profile following a single dose was determined in non-human primates (NHPs). Results ALX001 is a bispecific antibody with a “2 + 2” symmetric format. ALX001 exhibited high-affinity binding to TL1A (KD 0.1 nM) and IL-23 (KD 0.01 nM), with specific DR3 blockade while sparing DcR3. It inhibited TL1A-induced TF1 apoptosis and IL23-induced signaling with comparable potency to reference monoclonal antibodies (mAbs). In the mouse colitis model, it reduced DAI scores, diminished crypt loss, and suppressed mucosal cytokines, outperforming mAbs. Synergistic inhibition of cytokine release (INF-γ, IL-17, IL-22) was observed in human PBMCs and the mouse psoriasis model with reduced epidermal thickness and IL-17A secretion. The bsAb exhibited a long half-life in the NHP PK study. Conclusion The TL1A/IL-23 bsAb demonstrated superior preclinical efficacy over monotherapies by concurrently neutralizing two master regulators of inflammation. Mechanistic synergy and robust alleviation of intestinal and skin inflammation have been confirmed. The favorable PK profile supports extended dosing intervals, a key benefit for patients with chronic IMIDs. These findings warrant further development of ALX001 for the treatment of IMIDs. Conflict of interest: Zhou, Yali: No conflict of interest Li, Huilin: No conflict of interest Wang, Haiying: No conflict of interest Zhao, Mingjun: No conflict of interest Lu, Zhen: No conflict of interest Fan, Yanliu: No conflict of interest Yi, Simin: No conflict of interest Wang, Yali: No conflict of interest Zhou, Yupeng: No conflict of interest Duplantis, Barry: No conflicts Dr. Wang, Yuhao: No conflict of interest Yang, Lingjian: No conflict of interest He, Xiangyu: No conflict of interest Yu, Quan: No conflict of interest Li, Yi: No conflict of interest
Zhou et al. (Thu,) studied this question.