Schuler M, Cho BC, Sayehli CM, et al. - Because the clinical activity of fibroblast growth factor receptor (FGFR) inhibitors appears to only impact cancers harboring rare FGFR genetic aberrations, and response to rogaratinib (an oral pan-FGFR inhibitor) was predicted by high tumor FGFR mRNA expression in preclinical investigations, researchers undertook this phase 1 dose-escalation and dose-expansion study at 22 sites in Germany, Switzerland, South Korea, Singapore, Spain, and France to evaluate the safety, maximum tolerated dose, recommended phase 2 dose, pharmacokinetics, and preliminary clinical activity of rogaratinib among adults with advanced cancers. For FGFR mRNA expression, 866 patients were screened. Of these, treatment was received by 23 FGFR mRNA-unselected patients in the dose-escalation phase and 103 patients with FGFR mRNA-overexpressing tumors in the dose-expansion phase. They found no dose-limiting toxicities. The maximum tolerated dose was not reached; the recommended phase 2 dose was 800 mg twice daily and was chosen for the dose-expansion phase. Findings revealed good tolerability of rogaratinib, as well as its clinical activity against several types of cancer. For the recognition of a broader patient population who could be eligible for FGFR inhibitor treatment, the possible utility of FGFR mRNA expression-based selection was suggested as an additional biomarker.