A phase 1, multicenter, dose-escalation study of PRN1371, an irreversible covalent FGFR1-4 kinase inhibitor, in patients with advanced solid tumors, followed by expansion cohorts in patients with FGFR genetic alterations.

Abstract

TPS2616 Background: FGFR inhibition is a promising and clinically proven therapeutic approach in a number of solid tumors where genetic alterations of FGFR drive oncogenesis. PRN1371 is a highly selective oral, irreversible inhibitor of FGFR1-4 that exhibits high potency in cancer cell lines harboring FGFR alterations, including mutations and fusions. Methods: Part A of this phase 1 clinical trial explores ascending doses of PRN1371 in adult patients with advanced solid tumors in a "3 + 3" design, where cohorts of three patients are studied at each level until additional patients need to be added to better assess safety, establish the maximum tolerated dose and define the recommended phase 2 dose (RP2D). PRN1371 is dosed once or twice daily in continuous, 28-day cycles until disease progression. Part B studies include two or three expansion cohorts of different tumor types, 10 patients each with FGFR1-4 gene mutations, fusions, or amplification at the RP2D. The on-target effect of serum phosphorus and FGF23 increases are measured as potential pharmacodynamic biomarkers. Elevated serum phosphorus is managed with oral phosphate binding medications and a low phosphate diet, with dose interruptions and use of acetazolamide if certain thresholds are exceeded. Circulating tumor DNA from patients at baseline and during follow up is analyzed for FGFR genetic alterations. Pre and on-treatment tumor biopsies in Part B will be tested for a panel of pharmacodynamic biomarkers of FGFR inhibition. Clinical trial information: NCT02608125.