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ORAL 40 - Biology 1 (ID 154)
- Event: WCLC 2015
- Type: Oral Session
- Track: Thymoma, Mesothelioma and Other Thoracic Malignancies
- Presentations: 1
ORAL40.05 - The Cancer Stem Cell Inhibitors VS-6063 and VS-5584 Exhibit Synergistic Anticancer Activity in Pre-Clinical Models of Mesothelioma (ID 2753)
16:45 - 18:15 | Author(s): J. Testa
Malignant pleural mesothelioma (MPM) is an aggressive tumor in the pleural lining of the lung and peritoneum usually resulting from prior exposure to asbestos. Median overall survival with standard of care (SOC) chemotherapy is only 12 months from diagnosis. This poor prognosis may be attributable at least in part to cancer stem cells (CSCs) that are resistant to chemotherapy and can mediate cancer recurrence and progression. VS-6063 (defactinib) is an oral small molecule that targets cancer stem cells through the inhibition of focal adhesion kinase (FAK). VS-6063 has demonstrated tolerability, target inhibition, and preliminary signs of clinical activity as a single agent and in combination with paclitaxel in Phase 1 clinical trials (Jones et al., J Clin Oncol 29: 2011 (suppl; abstr 3002); Patel et al., J Clin Oncol 32:5s, 2014 (suppl; abstr 5521)). Currently, VS-6063 is being tested in a randomized, double-blind, placebo-controlled trial in malignant pleural mesothelioma immediately following front-line therapy (COMMAND Trial, NCT01870609). In an effort to identify additional mesothelioma patients who may benefit from a CSC targeting agent, we sought to identify compounds that show synergistic anticancer activity with VS-6063. PI3K/mTOR inhibitors were previously demonstrated to show activity in mesothelioma. VS-5584 is a potent oral small molecule that selectively kills CSCs by targeting multiple PI3K isoforms and mTORC1/2 (Kolev et al, Cancer Res; 75:1, 2014). VS-5584 is currently being investigated as a single agent in a Phase 1 clinical trial, (NCT01991938).
The synergy between VS-6063 and VS-5584 was demonstrated in vitro using cell viability assays analyzed by CalcuSyn, HSA and Loewe models. CSCs from mesothelioma cell lines were assessed by the Aldefluor+ flow cytometric assays. The anti-tumor activity of the VS-6063 and VS-5584 combination treatment was tested with in vivo mouse mesothelioma xenograft models.
A dual PI3K/mTOR inhibitor VS-5584 showed synergistic activity with a FAK inhibitor, VS-6063. VS-5584 further enhanced reduction of mesothelioma CSCs by VS-6063 measured by the Aldefluor+ assay in Mero-14 mesothelioma cells. In a 3D matrigel cell viability assay, the combination of VS-6063 and VS-5584 displayed synergistic reduction in cell viability based on multiple combination analysis models. In a MM87 mesothelioma xenograft model in vivo, the single agent treatment with either VS-6063 or VS-5584 was active in inhibiting mesothelioma tumor growth. Combination treatment further enhanced the antitumor efficacy of either agent alone (p <0.0001).
VS-6063 (defactinib) and VS-5584 exhibit synergistic anticancer activity in preclinical models of mesothelioma. These data provide a strong preclinical rationale for the open dose-escalation Phase I clinical trial of VS-6063 and VS-5584 in patients with relapsed mesothelioma (NCT02372227).
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