Abstract 1350: KD6001: A promising new anti-CTLA-4 human monoclonal antibody for cancer therapy

Abstract Cytotoxic T lymphocyte antigen-4 (CTLA-4) is a crucial immune checkpoint that negatively regulates T cell activation. Inhibiting this negative regulation through CTLA-4 blockade has emerged as a promising therapeutic strategy against cancer. Herein, we present the preclinical pharmacology study of KD6001, a novel anti-CTLA-4 IgG1 kappa human monoclonal antibody with superior properties compared to ipilimumab, a currently approved anti-CTLA-4 mAb. Surface plasmon resonance (SPR) analysis revealed that KD6001 exhibits a higher affinity for CTLA-4 compared to ipilimumab (KD = 0.57 nM vs 1.20 nM). Competition ELISA experiments demonstrated that KD6001 is significantly more potent than ipilimumab in disrupting CTLA-4 interactions with CD80 (IC50 = 16 ng/mL vs 93 ng/mL) and CD86. Further, amino acid point mutation analysis indicated that two specific residues following the CD80/CD86 binding site (99MYPPPY104) are critical for ipilimumab binding, whereas mutation of the two residues had minimal impact on KD6001's CTLA-4 binding activity. These findings suggest that KD6001 and ipilimumab bind distinct epitopes on CTLA-4. In vitro experiments demonstrated that KD6001 enhances the production of IL-2 and IFNγ in PHA-activated human lymphocytes and exhibits synergistic anti-tumor effects when combined with anti-PD-1/L1 antibodies. Moreover, in vivo studies utilizing syngeneic murine tumor models established in human CTLA-4 gene knock-in mice revealed that KD6001 effectively inhibits or delays tumor growth in colon cancer MC38, melanoma B16, and hepatocellular carcinoma Hepa1-6 models. Additionally, KD6001 demonstrated synergistic anti-tumor effects when combined with a mouse anti-PD-1 antibody or ibuprofen. Toxicity evaluation in cynomolgus monkeys revealed that KD6001 was generally well-tolerated at doses ranging from 1 mg/kg to 10 mg/kg administered intravenously once weekly for four weeks. The primary pathological changes observed were lymphocyte/monocyte infiltration or increased lymphocyte/monocyte infiltration in several organs, consistent with KD6001's mechanism of action. Notably, the similar affinity of KD6001 for human and cynomolgus monkey CTLA-4 suggests that the toxicity profile observed in monkeys accurately reflects the dose-toxicity relationship in human. The promising preclinical data presented herein support the further clinical development of KD6001 as a potential therapeutic agent for cancer treatment. Currently, clinical trials evaluating KD6001 in patients with advanced melanoma are ongoing. Citation Format: Yi Chen, Peng Li, Guobo Fang, Heng Wu, Chi Zhang, Zeling Cai. KD6001: A promising new anti-CTLA-4 human monoclonal antibody for cancer therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 1350.