Ovarian cancer is one of the deadliest malignancies in women, and up to 70% of patients with epithelial ovarian cancer have FAK overexpression, amplification, or activation. FAK plays an important role in cellular migration, growth factor signaling, cell cycle progression, cellular survival and chemoresistance. This biomarker is also significantly associated with higher tumor stage, metastasis, and shorter overall survival in patients with ovarian cancer. Inhibition of FAK is therefore emerging as a promising treatment target.

APG-2449 is a clinical stage FAK/ALK/ROS1 multi-kinase inhibitor. In this study we investigated antitumor activity of APG-2449 combined with standard-of-care chemotherapeutics in ovarian cancer in the preclinical setting. In a mouse xenograft tumor model derived from ovarian cancer cell line OVCAR-3, which was resistant to platinum-based therapies, APG-2449 combined with paclitaxel, and paclitaxel plus carboplatin, synergistically enhanced antitumor activity, whereas the chemotherapeutics showed no activity. Synergistic antitumor activity was also observed in multiple patient-derived xenograft (PDX) models derived from women with chemoinsensitive ovarian cancer, which also frequently expresses high levels of FAK.

By comparing gene expression profiles of PDX tumors obtained from responders and nonresponders to the combined therapy, we identified CD44 (a marker for cancer stem cells) as a potentially predictive biomarker. Western blot analysis confirmed higher protein levels of CD44 in pretreated tumors of responders. Interestingly, downregulation of CD44 levels was observed in combination-treated tumors, suggesting that these combinations reduced cancer stem cell populations in ovarian cancer. Accordingly, in ovarian cancer cells exposed to APG-2449 alone or combined with paclitaxel, numbers of cells positive for CD44 or aldehyde dehydrogenase 1 (ALDH1; another marker for cancer stem cells) decreased in a dose-dependent manner.

In summary, our data suggest that FAK inhibition by APG-2449 sensitizes ovarian tumors to chemotherapeutics in preclinical tumor models of ovarian cancer. The synergistic antitumor activity was mediated by downregulation of CD44+ or ALDH1+ cancer stem cell populations. These findings encourage clinical development of APG-2449 in combination with chemotherapies for treatment of ovarian cancer.

Citation Format: Ran Tao, Douglas D. Fang, Yuanbao Li, Kaixiang Zhang, Chunhua Xu, Xu Fang, Qixin Wang, Dajun Yang, Yifan Zhai. Focal adhesion kinase (FAK) inhibitor APG-2449 sensitizes ovarian tumors to chemotherapy via CD44 downregulation [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 968.