Abstract 1913: KD5005: HER-2 dependent strong potent anti-tumor activity of an anti-HER-2 mAb-TNFaimmunocytokine

Abstract Tumor necrosis factor alpha (TNFα) is a pleiotropic cytokine with diverse biological functions, including apoptosis, cell survival, inflammation, and immunity. While recombinant human TNFα has demonstrated therapeutic efficacy in isolated limb perfusion for soft tissue sarcoma and melanoma, its systemic administration is limited by severe toxicities, including hypotension. Tumor-specific targeting and enhancement of TNFα's tumor cell killing activity hold promise for improving its therapeutic index. To address these challenges, we developed KD5005, a novel HER-2-targeted immunocytokine fusion protein comprising an anti-HER-2 IgG1 monoclonal antibody (trastuzumab) and human TNFα. Tissue distribution studies revealed that KD5005 specifically accumulated in HER-2-expressing tumors, demonstrating its tumor-targeting capability. In vitro, KD5005 exhibited reduced TNFα-mediated apoptosis in L929 cells compared to recombinant TNFα, indicating its lower non-specific toxicity. Notably, KD5005 induced apoptosis of HER-2-positive human gastric cancer NCI-N87 cells at significantly lower concentrations than trastuzumab, TNFα, or their combination, demonstrating its enhanced tumor cell killing activity. The potent apoptotic activity of KD5005 was HER-2-dependent, as it did not show increased apoptotic activity in WT mouse forestomach carcinoma (MFC) cells and had similar apoptotic activity compared to the combination of trastuzumab and TNFα. This HER-2 dependency further supports the tumor-specific targeting of KD5005. In vivo, KD5005 demonstrated superior anti-tumor efficacy compared to the combination of trastuzumab and TNFα in syngeneic tumor models using CT26 tumor cells transfected with the human HER-2 gene. KD5005 induced robust tumor regression and durable cure in 7 of 8 mice, while the combination of trastuzumab and TNFα elicited weaker therapeutic responses, resulting in tumor rejection in only 3 of 8 mice. Pharmacokinetic and toxicity studies of KD5005 were conducted in cynomolgus monkeys. KD5005 exhibited a significantly prolonged in vivo half-life compared to TNFα, indicating its improved pharmacokinetic profile. KD5005 was administered intravenously every two weeks to the same animal in a dose-escalation study at 0. 3 mg/kg, 1. 0 mg/kg, 3 mg/kg, 10 mg/kg, and 30 mg/kg. The toxicity study results showed that the maximum tolerated dose for KD5005 in cynomolgus monkeys is 10 mg/kg, indicating its favorable toxicity profile. In summary, we have developed KD5005, a HER-2-targeted immunocytokine fusion protein with enhanced tumor-killing activity, improved pharmacokinetic properties, and a favorable toxicity profile. These preclinical findings support the further clinical development of KD5005 as a promising therapeutic agent for HER-2-positive cancers. Citation Format: YI CHEN, PENG LI, GUOBO FANG, HENG WU, CHI ZHANG, ZELING CAI. KD5005: HER-2 dependent strong potent anti-tumor activity of an anti-HER-2 mAb-TNFaimmunocytokine 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 (6Suppl): Abstract nr 1913.