Pemigatinib (INCB054828), a potent and selective oral fibroblast growth factor receptor 1-3 inhibitor, is a Biopharmaceutical Classification System class II compound with good permeability and pH-dependent solubility that is predominantly metabolized by cytochrome P450 (CYP) 3A. Two drug-drug interaction studies, one with acid-reducing agents, esomeprazole (proton pump inhibitor [PPI]) and ranitidine (histamine-2 [H2] antagonist), and the other with potent CYP3A-modulating agents, itraconazole (CYP3A inhibitor) and rifampin (CYP3A inducer), were performed. Both were open-label, fixed-sequence studies conducted in up to 36 healthy participants each, enrolled into two cohorts (n = 18 each). Pemigatinib plasma concentration was measured, and pharmacokinetic parameters were derived by non-compartmental analysis. There was an 88% and 17% increase in pemigatinib area under the plasma drug concentration-time curve (AUC) and maximum plasma drug concentration (Cmax), respectively, with itraconazole, and an 85% and 62% decrease in pemigatinib AUC and Cmax with rifampin coadministration. There was a 35% and 8% decrease in pemigatinib AUC and Cmax, respectively, with esomeprazole, and a 2% decrease in Cmax and 3% increase in AUC with ranitidine coadministration. In both studies, all adverse events reported were grade ≤ 2. Coadministration with itraconazole or rifampin resulted in a clinically significant change in pemigatinib exposure. Therefore, coadministration of strong CYP3A inducers with pemigatinib should be avoided, and the dose of pemigatinib should be reduced if coadministration with strong CYP3A inhibitors cannot be avoided. The effect of PPIs/H2 antagonists on pemigatinib exposure was modest, and pemigatinib can be administered without regard to coadministration of PPIs/H2 antagonists.