In a first-in-human, phase I clinical trial, Kim and colleagues investigated the use of the fibroblast growth factor receptor 4 (FGFR4) inhibitor fisogatinib in patients with hepatocellular carcinoma, demonstrating that it is generally tolerable and may be of clinical utility in patients positive for fibroblast growth factor 19 By investigating mechanisms of resistance to fisogatinib in select patients in the trial as well as by conducting further in vitro and in vivo studies, Hatlen, Schmidt-Kittler, and colleagues found evidence that FGFR4 is, as has been suspected but never proven, a driver of hepatocellular carcinoma For details, please see the article by Kim and colleagues on page 1696 and the article by Hatlen, Schmidt-Kittler, and colleagues on page 1686.