First‐in‐human phase I study of E7090, a novel selective fibroblast growth factor receptor inhibitor, in patients with advanced solid tumors

Fibroblast growth factor receptors (FGFR) are a family of transmembrane receptor tyrosine kinases involved in regulating cellular processes. FGFR mutations are implicated in oncogenesis, representing therapeutic potential in the form of FGFR inhibitors. This phase I, first-in-human study in Japan evaluated safety and tolerability of E7090, a potent selective FGFR1-3 inhibitor, in patients with advanced solid tumors. Dose escalation (daily oral dose of 1-180 mg) was carried out to assess dose-limiting toxicity (DLT), maximum tolerated dose, and pharmacokinetics. Pharmacodynamic markers (serum phosphate, fibroblast growth factor 23, and 1,25-(OH)2 -vitamin D) were also evaluated. A total of 24 patients refractory to standard therapy or for whom no appropriate treatment was available were enrolled. No DLT were observed up to the 140-mg dose; one patient in the 180-mg cohort experienced a DLT (increased aspartate aminotransferase/alanine aminotransferase, grade 3). The maximum tolerated dose was not reached. Dose-dependent increases in the maximum concentration and area under the curve from time 0 to the last measurable concentration were observed up to 180 mg. Dose-dependent increases were observed in all pharmacodynamic markers and plateaued at 100-140 mg, indicating sufficient FGFR pathway inhibition at doses ≥100 mg. In conclusion, E7090 showed a manageable safety profile with no DLT at doses ≤140 mg. Maximum tolerated dose was not determined. The recommended dose for the follow-up expansion part, restricted to patients with tumors harboring FGFR alterations, was determined as 140 mg, once daily.