Abstract B020: M1 macrophage engineered vesicles as ovarian cancer treatment in a mouse xenograft model

Abstract Ovarian cancer is the deadliest gynecologic cancer in the United States, and new treatment strategies are needed. We have developed M1 (anticancer) derived engineered vesicles (MEVs) which are able to both deliver chemotherapy and re-polarize tumor associated macrophages (TAMs) to an M1 or anticancer phenotype. 34 mouse xenografts were generated with CAOV-3 luciferase expressing ovarian cancer cells that were injected intraperitoneally into BALB/c scid mice. Mice were randomized into 4 groups, control, empty MEVs (E-MEVs), cisplatin loaded MEVs (C-MEVs), and cisplatin. Weekly bioluminescence imaging tracked progression of tumor in the mouse xenografts. M1 MEVs were made from cultured RAW 264. 7 cells, mouse macrophage cells, that were stimulated with IFN-ϒ and LPS to the M1 phenotype. MEVs were generated by nitrogen cavitation in the presence and absence of cisplatin to generate C-MEVs and E-MEVs, respectively. MEV size and quantity was assessed with a NanoSight NS300. MEV quantity was matched between C-MEVs and E-MEVs and cisplatin concentration in C-MEVs was quantitated by mass spectrometry (MS) and the dose was matched in the cisplatin group. Weekly intraperitoneal treatments were started after luminescence reached 1 × 108 photons/second within a whole mouse region of interest. Ten treatments were administered, and the mice were followed for 120 days post-treatment initiation for a planned survival endpoint. Statistical tests were performed using GraphPad Prism and R. The mean particle size of C-MEVs and E-MEVs was 159. 04 +/- 16. 95 nm (n=20) and 159. 94 +/- 11. 36 nm (n=20), respectively, which are not significantly different (p=0. 87). Yields of C-MEVs were significantly lower than E-MEVs, 2. 28 × 1012 +/- 6. 39 × 1011 particles/ml (n=20) and 4. 21 × 1012 +/- 7. 37 × 1011 particles/ml (n=20), respectively, (p0. 0001). Mean cisplatin concentration of C-MEVs was 566. 49 μg/mL (range 174. 62-1, 874. 56 μg/mL) by MS, and the mean dose of cisplatin administered was 118. 8 μg per mouse. The cisplatin group received eight weekly treatments before meeting endpoint criteria for euthanasia. Control, E-MEV, and C-MEV groups received 10 weekly treatments. Using last known luminescence values for the cisplatin group, mean radiance for the four treatment groups were: control 3. 53 × 1010 (SEM 1. 55 × 1010), cisplatin 1. 56 × 109 (SEM 7. 19 × 108), E-MEVs 1. 04 × 1010 (SEM 2. 56 × 109), and C-MEVs 2. 13 × 109 (SEM 6. 97 × 108). A pairwise comparison on luminescence between treatment groups demonstrated radiance was significantly different between control vs cisplatin (p=0. 0010), control vs E-MEVs (p=0. 0141), and control vs C-MEVs (p=0. 0010). The control, E-MEVs, and C-MEVs groups were followed 120-days post treatment initiation. On survival analysis, a Log-rank test demonstrates a difference in survival between groups (p0. 0001). E-MEVs and C-MEVs are well tolerated and have anticancer activity in an in vivo ovarian cancer mouse xenograft model. M1 MEVs are a novel immunotherapy and drug delivery vehicle that can be generated with consistent numbers, size, and concentrations. Citation Format: Connie D. Cao, Joseph R. McCorkle, Namrata Anand, Donglin Yan, David Schweer, Lan Li, Tanner Boggs, Derek B. Allison, Charles S. Dietrich, Frederick R. Ueland, Christopher I. Richards, Jill M. Kolesar. M1 macrophage engineered vesicles as ovarian cancer treatment in a mouse xenograft model abstract. In: Proceedings of the AACR Special Conference on Ovarian Cancer; 2023 Oct 5-7; Boston, Massachusetts. Philadelphia (PA): AACR; Cancer Res 2024;84 (5 Suppl₂): Abstract nr B020.