Abstract 5627: Characterization of the Rac inhibitor CPV-337 in metastatic breast cancer

Rac and Cdc42 are homologous Rho GTPases that act as anticancer and antimetastatic targets regulating cancer progression and metastasis-associated cell functions such as cell survival, cell polarity, proliferation, migration, and invasion. Our lead compound MBQ-167, a dual Rac/Cdc42 inhibitor (IC50 of ∼100nM; GI50 of 130nM), is currently in Phase I clinical trials for advanced triple-negative breast cancer (NCT06075810). By screening a panel of MBQ-167 derivatives to identify molecules with a range of inhibitory mechanisms that address distinct cancer types, we identified CPV-337, with an IC50 of ∼50nM for inhibiting Rac activation, via pulldown assays to capture the GTP bound Rac, and a GI50 of ∼55nM for inhibiting the viability of metastatic breast cancer cells, as measured by MTT assays. However, CPV-337 does not affect the viability of human mammary epithelial cells (HMECs), demonstrating non-toxic effects in primary epithelial cells. Additionally, wound healing assays show that CPV-337 reduces breast cancer cell migration by ∼50% at 50nM. These data show that CPV-337 is ∼2.5X more effective than MBQ-167. We then compared the efficacy of CPV-337 and MBQ-167 in nude mice with orthotopic tumors established from green fluorescent protein-tagged metastatic HER2-positive breast cancer cells. Results demonstrate that CPV-337 administered at 5mg/kg Body Weight (BW) parallels MBQ-167 treatments of 10mg/kg Body Weight (BW) at 5X a week for 2 months. Compared to the vehicle, both CPV-337 and MBQ-167 reduced tumor growth by ∼90-95%, from quantification of the integrated density of fluorescent tumors for 62 days. Lung metastases were inhibited by ∼50% in CPV-337 treated mice, and both compounds inhibited liver and kidney metastases by ∼95%. At necropsy, blood was collected, and whole blood was analyzed by flow cytometry for the phosphorylated form of the Rac and Cdc42 downstream effector p21-activated kinase (p-PAK), using a fluorescent anti-p-PAKT423antibody, as a measure of Rac activation inhibition. CPV-337 inhibited PAK activation significantly by 37.4%, compared to vehicle. Interestingly, a significant increase in M1 anti-tumorigenic macrophages was observed in splenocytes of mice treated with CPV-337, implicating CPV-337 in the anticancer immune response. Further evaluation of CPV-337’s inhibitory mechanism, toxicity, bioavailability, and Rac/Cdc42 regulated processes in the tumor microenvironment are warranted to translate this promising anticancer compound to the clinic. Citation Format: Jessica Colon Gonzalez, Nilmary Grafals Ruiz, Anamaris Torres Sanchez, Stephanie Dorta Estremera, Cornelis Vlaar, Suranganie Dharmawardhane. Characterization of the Rac inhibitor CPV-337 in metastatic breast cancer [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 5627.