Abstract 17: MBQ-167, a Rac/Cdc42 targeted therapeutic, in combination with paclitaxel for TNBC treatment

Abstract Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer, with a high predisposition for locally advanced and metastatic cancer. While targeted therapies for TNBC are in various stages of development, current standard chemotherapies include taxanes such as paclitaxel and anthracycline agents. With the objective of specifically targeting invasive cancer, our group has been developing small-molecule inhibitors of the Rho GTPases Rac and Cdc42, which are known drivers of cancer cell invasion and metastasis. Of these, MBQ-167 inhibits both Rac and Cdc42 with IC50s of 103 and 78 nmol/L, respectively, and consequently inhibits p21-activated kinase (PAK) signaling, metastatic cancer cell proliferation, migration, tumor growth, and metastasis (Humphries-Bickley et al., Mol Cancer Ther 2017). We found that in addition to blocking HER2-type breast cancer progression, MBQ-167 is also highly effective against TNBC cell and tumor growth, as well as metastasis in mouse models. The purpose of this study was to test the efficacy of MBQ-167 in combination with the current chemotherapeutic paclitaxel. We hypothesized that the combination of paclitaxel and MBQ-167 is a rational strategy to inhibit tumor growth and metastasis in TNBC. To test this hypothesis, we administered a nontoxic dosage of individual MBQ-167, paclitaxel, or combined MBQ-167 and paclitaxel to immunocompromised mice bearing mammary fat pad tumors from GFP-tagged MDA-MB-468 or MDA-MB-231 human TNBC cells. Tumor growth was monitored weekly and metastasis was quantified at the end of the study. Treatment with MBQ-167 and/or paclitaxel resulted in reduced tumor growth by 70-80% in both models. In the MDA-MB-231 model, MBQ-167 paralleled paclitaxel treatment with a modest benefit in combined therapy. However, in the epidermal growth factor receptor (EGFR)-positive TNBC model MDA-MB-468, MBQ-167 alone or in combination significantly reduced metastasis to the lungs and spleen, while paclitaxel alone increased metastasis to the liver, lungs, and spleen. These results show that MBQ-167 is a promising antimetastatic agent that can be effective in combination with current chemotherapeutic agents. Citation Format: Jean Ruiz-Calderon, Irmaris Lopez-Lopez, Ailed Cruz-Collazo, Suranganie Dharmawardhane. MBQ-167, a Rac/Cdc42 targeted therapeutic, in combination with paclitaxel for TNBC treatment [abstract]. In: Proceedings of the AACR Special Conference on Advancing Precision Medicine Drug Development: Incorporation of Real-World Data and Other Novel Strategies; Jan 9-12, 2020; San Diego, CA. Philadelphia (PA): AACR; Clin Cancer Res 2020;26(12_Suppl_1):Abstract nr 17.