Abstract 3920: The role of humanized monoclonal antibody ALT-100 in reducing cancer-induced bone pain: A murine animal model study

Abstract Breast cancer commonly metastasises to the bone promoting a combination of inflammatory and neuropathic mechanisms. This leads to different perceptions of pain with a reported 30-50% of all cancer patients and 75-90% of late-stage patients having cancer-induced bone pain (CIBP). Thus, there is a need for therapeutic interventions to decrease pain caused by the mechanisms of CIBP. Extracellular Nicotinamide Phosphoribosyltransferase (eNAMPT) is a cytokine overexpressed in metastatic breast carcinoma that binds to Toll-like Receptor 4 (TLR4), triggering a signaling cascade through Nuclear Factor kappa beta (NFk-B) and resulting in inflammation, osteoclastogenesis, and severe bone pain. To assess the impact of eNAMPT on CIBP, ALT-100, a monoclonal antibody neutralizing eNAMPT, was tested in a murine CIBP model. The left femur of C57BL/6J female mice was inoculated with EO771 breast cancer cells and allowed 7 days for recovery from tumor growth and the development of cancer-induced pain. Behavioral data were collected to evaluate ALT-100's effectiveness in reducing pain. Four groups were used: sham + saline, sham + ALT-100, cancer + ALT-100, and cancer + saline, with ALT-100 dosed at 4 mg/kg. Pain was assessed on days 0, 7 (pre- and 2 hours post-injection of ALT-100), 10, and 14 using flinching and guarding behavior tests. A two-way ANOVA and Tukey's multiple comparisons test indicated that ALT-100 significantly reduced pain compared to the cancer + saline group. Bone scoring on days 0 and 14 showed no significant differences in bone lesions and fractures between cancer + ALT-100 and cancer + saline groups. To test ALT-100's efficacy in inhibiting osteoclastogenesis in vitro, RAW 264.7 macrophage cells were plated in five groups exposed to different drug combinations: media, eNAMPT, ALT-100, 1:1 eNAMPT + ALT-100, and 1:2 eNAMPT + ALT-100. After 5 days a marker for osteoclastogenesis, Tartrate-Resistant Acid Phosphatase staining, was measured demonstrating that cells treated with ALT-100 + eNAMPT had significantly fewer osteoclasts than those treated with eNAMPT alone. Together these results indicate that ALT-100 inhibits metastatic breast cancer pain and eNAMPT-induced osteoclast differentiation. Citation Format: Nikhil C. Mathur, Ethan Villarroel, Isabella Villarroel, Erfan Bahramnedjad, Sally Dickinson, Joe G. Garcia, Tally Largent-Milnes, Todd W. Vanderah. The role of humanized monoclonal antibody ALT-100 in reducing cancer-induced bone pain: A murine animal model study [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 3920.