Abstract 4808: Aflibercept is highly active in clinically relevant, patient derived xenografts of colorectal cancer

Abstract

Abstract Aflibercept (ziv-aflibercept in USA), a new fusion protein, targets vascular endothelial growth factor (VEGF)-A, VEGF-B, and placental growth factor (PlGF). Aflibercept + FOLFIRI is approved for treating metastatic colorectal cancer (mCRC) that is resistant to or has progressed following an oxaliplatin containing regimen. We investigated the pharmacological activity of aflibercept in CRC patient derived xenografts (PDX), most metastases-derived, and characterized PDX molecular and phenotypic properties. In 48 CRC PDX, Whole Exome Sequencing revealed: 85% APC, 79% TP53, 51% KRAS, 3% NRAS, 25% PIK3CA, 11% PTEN and 8% BRAF mutants. There was no significant association between angiogenic factors, tumor mutation profiles, and response to aflibercept. In tumors, protein levels of human (h) VEGF-A were significantly higher than mouse (m) VEGF-A, hPlGF, and mPlGF (Chiron et al, ESMO, 2013). Affymetrix probes detected VEGF-A and PIGF but not VEGF-B mRNA in most PDX. There was no significant association between expression of angiogenic factors and response to aflibercept. Histological sections of CRC tumors from PDX, xenografts created from cell lines, and patients’ tumor specimens indicated that stromal involvement in human tumors was recapitulated in PDX but not in tumors from cell lines. PlGF expression was analyzed by immunohistochemistry on colon cancer tissue arrays. A significant number of colon cancer specimens were positive for PlGF, expressed in tumor cells and stroma. Aflibercept resulted in anti-tumor activity in 47/48 CRC PDX models and complete tumor stasis in 31/48 models. Efficacy data from 5 PDX models responsive to aflibercept and CRC standard of care (SOC) drugs, all administered as monotherapies, are below. The robust activity of aflibercept in CRC PDX models that are sensitive to SOC drugs suggest that CRC patients would benefit from aflibercept treatment, independently of mutational status or expression of angiogenic factors. In Vivo Sensitivity Profile (optimal Tumor/Control (%))CRC PDX ModelPrior TreatmentsAflibercept 25 mg/kg, SC, 2x/wk5-FU100 mg/kg, IP, 1x/wkIrinotecan 50 mg/kg, IV, 1x/wkOxaliplatin 10 mg/kg, IP, Q2WCetuximab30 mg/kg, IV,1x/wkKRAS StatusCFX 1991Not available-2.531.51.856.342.1MutantCFX 2032Not available3.147.76.760.535.7MutantCFX 2048Not available-10.326.221.350.12.6Wild-typeCFX 20655-FU, leucovorin-11.920.614.471.82.2Wild-typeCFX 2067None6.253.045.158.914.2Wild-type Citation Format: Rebecca G. Bagley, Zakia Amalou, Marielle Chiron, Vincent Vuaroqueaux, Anne Caron, Nina Baltes, Heinz H. Fiebig. Aflibercept is highly active in clinically relevant, patient derived xenografts of colorectal cancer. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 4808. doi:10.1158/1538-7445.AM2014-4808