Abstract 5625: EphB4 agonist B4-007 was effectively against high-grade serous ovarian cancer (HGSC) as a single agent in cell-based and patient-derived xenograft models

Introduction: This study aimed to assess the therapeutic potential and molecular mechanisms of B4-007, an agonist peptide with high binding affinity (Kd = 7.0 nM) to EphB4, a receptor tyrosine kinase implicated in cancer progression and angiogenesis, in preclinical models of high-grade serous ovarian cancer (HGSC). Methods: EphB4-agonistic activity of B4-007 or its analogues was confirmed by determining tyrosine-phosphorylation levels of EphB4 (p-EphB4) treated with a gradient of B4-007 (500 nM-10 µM) and incubation times (up to 60 minutes). Two orthotopic HGSC models, including a platinum-resistant patient-derived xenograft (PDX2428) model carried by female NOG mice and a human tumor xenograft OVCAR8-ip2-luc carried by female nude mice were used. On 2 weeks after tumor inoculation, B4-007 was injected intraperitoneally (IP) at a dose of 13 mg/kg, 3 times a week for 6 weeks. After 18 doses, all mice were euthanized, and tumor weight and number of tumor nodules in the peritoneal cavity were recorded. For the OVCAR-ip2-luc mouse model, B4-007 was injected via IP at doses of 13 or 52 mg/kg/injection, three times a week for a total of ten doses. Tumor growth was monitored weekly using bioluminescence imaging. Results: In vitro, B4-007 or its analogues induced EphB4 phosphorylation, with maximal phosphorylation observed at 60 minutes at 1.0 µM. Notably, higher concentrations (10 µM) did not yield further increase in p-EphB4 level. In vivo, B4-007 demonstrated significant antitumor efficacy in both HGSC models as a single agent. In the PDX2428-NOG model, tumor burden in the B4-007-treated mice was significantly decreased than those in the control mice (p<0.05). In the OVCAR8-ip2-luc model, bioluminescence imaging showed that B4-007 at both doses (13 mg/kg and 52 mg/kg) was effective in suppress tumor growth. However, treatment at the higher dose did not provide additional benefit. B4-007 was well tolerated as reflected by stable mouse body weight across each group. These findings underscore the importance of optimizing dosing schedules and suggest that future studies should prioritize lower concentrations (e.g., <13 mg/kg/injection) to determine the minimal effective dose. Conclusion: B4-007 demonstrated significant anti-tumor efficacy as a single agent without apparent toxicity in orthotopic HGSC models. Our finding has implications for further developing a novel EphB4-targeted therapy to maximize antitumor efficacy and minimize toxicity. Citation Format: Qiu-Xu Teng, Chiyi Xiong, Ping Pan, Thanh Chung Vu, Yunfei Wen, Chun Li. EphB4 agonist B4-007 was effectively against high-grade serous ovarian cancer (HGSC) as a single agent in cell-based and patient-derived xenograft models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5625.