The Fgfr-Inhibitor Derazantinib (Dzb) Is Active In Pdx-Models Of Gi-Cancer With Specific Aberrations In Fgfr

421 Background: DZB is an oral small-molecule Fibroblast Growth Factor Receptor 1/2/3 inhibitor (FGFRi) with clinical activity in FGFR2-fusion-positive cholangiocarcinoma. DZB was screened for activity in gastrointestinal cancer (GIC), by using a panel of GIC cell-lines, human tumor xenografts and 30 GIC patient-derived xenograft (PDX) models. Methods: DZB anti-proliferative potency was determined in 26 GIC cell lines to determine the GI50. The GIC cell-line, SNU-16 was grown s.c. in nude mice and treated daily for 3-weeks with DZB at the MTD of 75 mg/kg, p.o. Plasma and tumor were removed and analyzed for drug-levels and PD biomarkers to assess pathway inhibition. DZB (@MTD) was tested in the PDX-screen (15 biliary, 13 gastric and 2 colorectal cancer; n≥3/group) using models with FGFR-fusions, FGFR-mutations and/or differing FGFR copy-number (CN)/RNA-seq expression levels. Efficacy and tolerability were quantified as a dT/C (treated/control). Results: Cellular GI50s ranged from 0.02-20 μM; the most sensitive (GI50≤0.5 μM) had FGFR-fusions or high-expression. In mice, DZB induced stasis of SNU-16 tumors (dT/C∼0.0) and was well tolerated (dT/C > 1.0); the plasma PK was dose-dependent with a Cmax of 2 μM (4 hr), a Cmin of 0.5 μM. DZB induced dose- and time-dependent changes in the MAPK-pathway and expression of downstream genes, consistent with its mode of action. In PDX-models, efficacy varied from no-response to 100% regression. Known driver-mutations were associated with partial-responses (best dT/C = 0.42), but models with FGFR-fusions, especially FGFR2-fusions, were very sensitive leading to stasis or strong-regression, particularly in gastric cancer. High-expression of FGFR2 was also associated with strong responses. There was no direct correlation between CN and high RNA-seq values suggesting amplification was not always a predictor of high expression. Endpoint PD-analyses of the PDX-models is ongoing to identify other potential stratifiers and PD-markers of response. Conclusions: DZB showed convincing activity in GIC-models with FGFR-fusions and/or high expression. A clinical trial is planned in patients with gastric cancer to investigate DZB as mono- and combination-therapy.