Background: Futibatinib is an oral, irreversible, highly selective fibroblast growth factor receptor (FGFR)1e4 inhibitor with potent preclinical activity against tumors harboring FGFR aberrations. This first-in-human, phase I dose-escalation trial (NCT02052778) evaluates the safety and pharmacokinetics/pharmacodynamics of futibatinib in advanced solid tumors. Patients and methods: Following a standard 3þ3 dose-escalation design, eligible patients with advanced solid tumors refractory to standard therapies received 8e200 mg futibatinib three times a week (t.i.w.) or 4e24 mg once daily (q.d.). Results: A total of 86 patients were enrolled in the nine t.i.w. (n ¼ 42) and five q.d. cohorts (n ¼ 44); 71 patients (83%) had tumors harboring FGF/FGFR aberrations. Three of nine patients in the 24-mg q.d. cohort experienced dose-limiting toxicities, including grade 3 increases in alanine transaminase, aspartate transaminase, and blood bilirubin (n ¼ 1 each). The maximum tolerated dose (MTD) was determined to be 20 mg q.d.; no MTD was defined for the t.i.w. schedule. Across cohorts (n ¼ 86), the most common treatment-emergent adverse events (TEAEs) were hyperphosphatemia (59%), diarrhea (37%), and constipation (34%); 48% experienced grade 3 TEAEs. TEAEs led to dose interruptions, dose reductions, and treatment discontinuations in 55%, 14%, and 3% of patients, respectively. Pharmacokinetics were dose proportional across all q.d. doses but not all t.i.w. doses evaluated, with saturation observed between 80 and 200 mg t.i.w. Serum phosphorus increased dose dependently with futibatinib on both schedules, but a stronger exposureeresponse relationship was observed with q.d. dosing, supporting 20 mg q.d. as the recommended phase II dose (RP2D). Overall, partial responses were observed in five patients [FGFR2 fusion-positive intrahepatic cholangiocarcinoma (n ¼ 3) and FGFR1-mutant primary brain tumor (n ¼ 2)], and stable disease in 41 (48%). Conclusions: Futibatinib treatment resulted in manageable safety, pharmacodynamic activity, and preliminary responses in patients with advanced solid tumors. The results of this phase I dose-escalation trial support 20 mg q.d. futibatinib as the RP2D. Clinical trial registration: FOENIX-101 (ClinicalTrials.gov, NCT02052778).
Futibatinib, an oral, irreversible fibroblast growth factor receptor (FGFR) 1-4 inhibitor, is being evaluated for FGFRaberrant tumors. Two open-label phase 1 studies evaluated the effects of high-fat, high-calorie food and concomitant proton pump inhibitors (PPIs; lansoprazole) on single-dose futibatinib (20 mg) pharmacokinetics and safety in healthy adults. In the food effect study (N = 17), subjects received futibatinib under fed and fasted conditions, separated by a 7-day washout. In the PPI study (N = 20), subjects received futibatinib alone, underwent a 2-day washout, and then received lansoprazole 60 mg once daily for 5 days, with futibatinib also administered on day 5. Under fed versus fasted conditions, futibatinib bioavailability was 11.2% lower (area under the plasma concentration-time curve from time 0 to infinity geometric mean ratio 88.8%; 90% confidence interval, 79.8%-98.9%), and median time to maximum plasma concentration was significantly delayed (4.0 vs 1.5 hours; P < .0001). There were no significant differences in futibatinib exposure between futibatinib plus lansoprazole and futibatinib alone. No serious adverse events occurred in either study. These findings suggest that food and PPIs are unlikely to have clinically meaningful impacts on futibatinib bioavailability. Thus, futibatinib may be used with or without food and concomitantly with acid-reducing agents.
Tegafur (FT), a prodrug of 5-fluorouracil, is a chiral molecule, a racemate of R-and S-isomers, and CYP2A6 plays an important role in the enantioselective metabolism of FT in human liver microsomes (R-FT >> S-FT). This study examined the enantioselective metabolism of FT by microsomes prepared from Sf9 cells expressing wildtype CYP2A6 and its variants (CYP2A6*7, *8, *10, and *11) that are highly prevalent in the Asian population. We also investigated the metabolism of coumarin and nicotine, both CYP2A6 probe drugs, in these variants. Enzyme kinetic analyses showed that CYP2A6.7 (I471T) and CYP2A6.10 (I471T and R485L) had markedly lower V max values for both enantiomers than wild-type enzyme (CYP2A6.1) and other variant enzymes, whereas K m values were higher in most of the variant enzymes for both enantiomers than CYP2A6.1. The ratios of V max and K m values for R-FT to corresponding values for S-FT (R/S ratio) were similar among enzymes, indicating little difference in enantioselectivity among the wild-type and variant enzymes. Similarly, both CYP2A6.7 and CYP2A6.10 had markedly lower V max values for coumarin 7-hydroxylase and nicotine C-oxidase activities than CYP2A6.1 and other variant enzymes, whereas K m values were higher in most of the variant enzymes for both activities than CYP2A6.1. In conclusion, the amino acid substitutions in CYP2A6 variants generally resulted in lower affinity for substrates, while V max values were selectively reduced in CYP2A6.7 and CYP2A6.10. Consistent R/S ratios among CYP2A6.1 and variant enzymes indicated that the amino acid substitutions had little effect on enantioselectivity in the metabolism of FT.
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