Abstract 2088: The activity of the FGFR selective inhibitor Debio 1347 is correlated with high mRNA expression

Dysregulation of the fibroblast growth factor receptor (FGFR) signaling pathway due to receptor overexpression, gene amplification, point mutations or fusions/chromosomal translocations is associated with cancer development and progression. Debio 1347 (CH5183284) is an oral selective FGFR inhibitor (FGFR1, 2 and 3) currently in clinical development. The aim of this study was to investigate Debio 1347 activity in patient derived xenograft (PDX) mouse models harboring diverse FGFR alterations in multiple indications. The trial was conducted in 66 PDX models of diverse histotypes selected according to their FGFR1, 2 and 3 alteration status. Debio 1347 was administered orally once daily at 40 up to 80 mg/kg for 10 to 22 consecutive days (N=3/group). Tumor volume was compared to the vehicle control group and measured by caliper twice weekly. Treatment response was determined by relative treatment-to-control ratios (ΔT/ΔC) of which a responding model was defined as ΔT/ΔC Debio 1347 induced tumor regression in 33% of PDX models that exhibited a gene copy number gain and/or the presence of a FGFR fusion gene and/or an FGFR mutation. In addition, Debio 1347 treatment led to tumor regression in 29% of models that did not harbor any FGFR genetic alteration. In contrast, all models that responded to Debio 1347 were shown to display a high expression level (mRNA) of at least one FGFR gene. These findings suggest that high expression of at least one FGFR might be a better predictor of sensitivity to Debio 1347 than genetic alteration. Furthermore, response to Debio 1347 was associated with a decrease in DUSP6 mRNA levels, suggesting that it could be a reliable pharmacodynamic biomarker in clinical trials. These results provide new mechanistic insights into the predictive sensitivity to Debio 1347 and will help refine patient selection for FGFR-targeted therapy. Citation Format: Franck Brichory, Anna Pokorska-Bocci, Paolo Nuciforo, Stefania Rigotti, Nathalie Lembrez, Gregoire Vuagniaux, Corinne Moulon, Anne Vaslin. The activity of the FGFR selective inhibitor Debio 1347 is correlated with high mRNA expression [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 2088. doi:10.1158/1538-7445.AM2017-2088