Abstract 4337: TGI-17b: A potential first-in-class PD-1/VEGF/IL-2α-bias trispecific antibody and the potential next generation cornerstone for pan-cancer therapy

Abstract Background: Immune checkpoint inhibitors (ICIs) have revolutionized the treatment of solid tumors. However, their efficacy is often limited by resistance, remaining a major therapeutic challenge for many patients. Various next-generation immuno-oncology (IO) therapeutics are under extensive investigation. Among these, PD-1/VEGF and PD-1/IL-2α-bias bispecific antibodies have demonstrated promising efficacy in patients with ICI-resistant and immunologically "cold" tumors.To build upon these advances, we developed TGI-17b, a trispecific antibody combined of PD-1/VEGF/IL-2α-bias. TGI-17b demonstrated superior anti-tumor efficacy compared to either PD-1/VEGF or PD-1/IL-2α-bias alone in preclinical models, positioning it as a potential next generation cornerstone therapy for pan-cancer applications. Methods: The binding affinity of TGI-17b for PD-1, VEGF, IL-2Rα, and IL-2Rβγ was evaluated using Surface Plasmon Resonance (SPR). Its in vitro functional activity was assessed by measuring the blockade of PD-1/PD-L1, VEGF/VEGFR1 and VEGF/VEGFR2 interactions. Toxicity was evaluated by intravenous administration of a murine surrogate antibody (mPD-1/VEGF/IL-2α-bias) in wild-type mice, compared with a clinical-stage competitor's murine surrogate (mPD-1/IL-2α-bias). The anti-tumor efficacy of TGI-17b was investigated in MC38 and B16F10 syngeneic tumor models using humanized PD-1 transgenic mice. Results: TGI-17b exhibited high affinity for VEGF (0.86 nM) and intermediate affinity for IL-2Rα (KD = 24.3 nM), with minimal binding to IL-2Rβγ, confirming its pronounced IL-2Rα-bias character. In functional assays, TGI-17b blocked PD-1/PD-L1 interaction with a slightly higher EC50, and blocked VEGF/VEGFR1 and VEGF/VEGFR2 interactions with significantly lower EC50 values compared to AK112, a PD-1/VEGF bispecific antibody (PD-1/PD-L1 blockade EC50: 0.70 µg/mL for TGI-17b vs. 0.32 µg/mL for AK112; VEGF/VEGFR1 blockade EC50: 0.37 µg/mL vs. 3.53 µg/mL; VEGF/VEGFR2 blockade EC50: 1.29 µg/mL vs. 7.71 µg/mL). In toxicity studies, TGI-17b surrogate demonstrated a favorable safety profile at 40 mg/kg (IV, twice weekly), whereas the competitor's surrogate mPD-1/IL-2α-bias antibody was lethal at 5 mg/kg.In the in vivo efficacy studies, TGI-17b showed superior anti-tumor activity compared to the PD-1/VEGF bispecific antibody in the MC38 model. In the B16F10 model, its efficacy substantially exceeded that of both the PD-1/VEGF and PD-1/IL-2α-bias bispecific antibodies. Conclusions: These results indicate that TGI-17b, a potential first-in-class PD-1/VEGF/IL-2α-bias trispecific antibody, possesses compelling anti-tumor efficacy and a favorable safety profile in preclinical models. This robust evidence supports its further clinical development as a promising therapeutic candidate for pan-cancer applications. Citation Format: Guoshuai Cao, Yangyang Li, Yuwei Wu, Haoyu Sun, Zhigang Tian. TGI-17b: A potential first-in-class PD-1/VEGF/IL-2α-bias trispecific antibody and the potential next generation cornerstone for pan-cancer therapy abstract. In: Proceedings of the American Association for Cancer Research Annual Meeting 2026; Part 1 (Regular Abstracts); 2026 Apr 17-22; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2026;86(7 Suppl):Abstract nr 4337.