Abstract PS4-06-30: Increased Survival in Nude Mice Inoculated with MCF7 Breast Cancer (BC) in the Mammary Fat-Pad Achieved via a Single Injection of a Lipid-like Hydrogel Emulsion Containing a New Molecular Entity (NME) and N-allyl Noroxymorphone (NaN) Compared to Tamoxifen (TAM) and Abemaciclib (ABE)

Abstract Background: First-line therapies after the diagnosis of a BC malignancy depends on the phenotype (e.g., HR+, HER2+, or triple negative BC) includes neo-adjuvant therapy, surgical intervention (e.g., mastectomy or lumpectomy), and sometimes post-surgical radiation. Both targeted therapies (e.g., TAM and ABE) and chemotherapies are systemically administered, which results in negative off-target effects. Initial results for Zeta-BC-007, which is a fixed-dose drug that comprises an NME and NaN in a lipid-like hydrogel emulsion, shows superior tumoricidal effects that increased survival after a single intratumoral injection relative to groups treated with systemically administered TAM or ABE. Importantly, other hydrophobic drugs, such as ABE, can be loaded into the lipid nanoparticles (LNP) for delivery via Zeta-BC-007. Methods: The NME (lanthanum (III) tri 9,10-diacetoxy octadecanoate) and the lipid-like hydrogel emulsion contains alginate and linoleic acid. All other drugs were obtained commercially. The NME is an intrinsic component of the LPNs in Zeta-BC-007 while other drugs were loaded onto LNPs (size = 200-nm) prior to incorporation into the lipid-like hydrogel emulsion. MCF7 cells treated with the NME, ABE, and NaN in vitro were assessed for cell proliferation and death. Nude mice were inoculated with the MCF7 HR+ BC cells (N=142 total; N=8/group) and treated when tumors were palpable (150-mm3). Mice were sorted into groups: 1) Control; 2) TAM (1-mg/mL) and 3) ABE (125-mg/mL) given via oral gavage every 72-hours; 4) Zeta-BC-007 with the NME only; 5) Zeta-BC-007 with the NME + NaN; 6) Zeta-BC-007 with the NME + ABE; and 7) Zeta-BC-007 with the NME + NaN + ABE. Tumor volumes were measured every 72-hours for 60-days. Excised tumors processed for H&E histology were evaluated with histomorphology (e.g., tumor volume and necrosis) and histopathology. Results: In vitro, a significant dose-dependent decrease in cell number was seen for the MCF7 cells through 72-hours for the NME, NaN, and ABE (p<0.05). The combination of 5-fold less NaN (1-mM) + 10-nM of ABE resulted in a 60% decrease in cell number (p<0.01), suggesting a synergistic effect from pairing the 2 drugs. In the mouse study, we found that TAM and ABE treatment decreased tumor volume 34% and 15%, relative to Controls. Treatment with Zeta-BC-007 with the NME only decreased tumor volume 27% while the tumor volume was decreased 53% for Zeta-BC-007 with the NME + NaN, 57% for Zeta-BC-007 with the NME + ABE, and 66% for Zeta-BC-007 with the NME + NaN + ABE. Zeta-BC-007 loaded with NaN or ABE alone or in combination resulted in a 30% - 60% decrease in tumor volume relative to TAM and ABE administered alone. By day 60, all mice in the Control, TAM, and ABE treated groups were dead. Histology showed a decrease in tumor volume and increased adipose tissue and necrosis for the mice treated with any of the Zeta-BC-007 drug combinations. Mice in the Zeta-BC-007 groups also had no ki67 staining (i.e., no tumor activity) and increased numbers of macrophages, the latter of which was confirmed by increased numbers of circulating monocytes. Conclusion: Treatment of BC via intratumoral injection is a novel therapeutic approach that promises to increase drug bioavailability while eliminating negative off-target effects. ABE and NaN appear to have synergistic treatment effects while the NME also induced significant cytotoxicity. Zeta-BC-007 showed significant reductions in tumor volume via increased necrosis that relates to increased cytotoxicity in the tumor. This increase tumoricidal effect from Zeta-BC-007 led to increased survival. Further work in needed; however, these initial results point to a new treatment paradigm. Citation Format: B. S. Margulies, J. C. Loy. Increased Survival in Nude Mice Inoculated with MCF7 Breast Cancer (BC) in the Mammary Fat-Pad Achieved via a Single Injection of a Lipid-like Hydrogel Emulsion Containing a New Molecular Entity (NME) and N-allyl Noroxymorphone (NaN) Compared to Tamoxifen (TAM) and Abemaciclib (ABE) [abstract]. In: Proceedings of the San Antonio Breast Cancer Symposium 2025; 2025 Dec 9-12; San Antonio, TX. Philadelphia (PA): AACR; Clin Cancer Res 2026;32(4 Suppl):Abstract nr PS4-06-30.