PRN1371

PRN1371 is a specific and potent FGFR1-4 and CSF1R inhibitor (IC50s: 0.6/1.3/4.1/19.3/8.1 nM for FGFR1/2/3/4 and CSF1R) .PRN1371 presents a unique profile of high biochemical and cellular potency (FGFR1 IC50:0.6 nM, SNU16 IC50: 2.6 nM), prolonged target engagement (FGFR1 occupancy 24 h=96%), 100 μM.In PK studies of rat, dog, and cynomolgus monkey, PRN1371show rapid iv clearance in all species. PRN1371 shows rapid clearance (Cl=160 mL per min per kg), yet dosing p.o (20 mg/kg) demonstrates high oral exposure (AUC=4348 h·ng/mL) and a reasonable half-life (t1/2=3.8 h) . Low levels of pFGFR2 confirm the ability of PRN1371 to block FGFR2 activity in tumor tissue. PRN1371 induces a dose-dependent reduction in tumor volume and up to 68% tumor growth inhibition at the highest dose of 10 mg/kg b.i.d. following 27 days of treatment. All doses are well tolerated with no significant bodyweight loss. (In Vitro) :PRN1371 presents a unique profile of high biochemical and cellular potency (FGFR1 IC50=0.6 nM, SNU16 IC50=2.6 nM), prolonged target engagement (FGFR1 occupancy 24 h=96%), 100 μM. Broader kinome-wide biochemical profiling of PRN1371 against 251 kinases identifies only FGFR1 4 and CSF1R as being potently inhibited. (In Vivo) :PK studies of PRN1371 in rat, dog, and cynomolgus monkey show rapid iv clearance in all species. PRN1371 shows rapid clearance (Cl=160 mL per min per kg), yet dosing po (20 mg/kg) demonstrates high oral exposure (AUC=4348 h·ng/mL) and a reasonable half-life (t1/2=3.8 h) . Low levels of pFGFR2 confirms the ability of PRN1371 to block FGFR2 activity in tumor tissue. PRN1371 induces a dose-dependent reduction in tumor volume and up to 68% tumor growth inhibition at the highest dose of 10 mg/kg b.i.d. following 27 days of treatment. All doses are well tolerated with no significant body weight loss. PRN1371 free base has been administered orally once daily as powder in a capsule on a 28-day continuous schedule. Human plasma concentrations for doses ranging from 15 to 35 mg confirm good oral exposure, rapid systemic clearance, no accumulation from day 1 to day 15, and a dose-dependent increase in AUC. Serum phosphate, a pharmacodynamic marker of FGFR inhibition, is increased for all doses studied and shows a dose-dependent increase between 20 and 35 mg, despite the administration of prophylactic phosphate binders.