The following pharmacokinetic parameters were observed following administration of gilteritinib 120 mg once daily, unless otherwise specified.
Gilteritinib exposure (Cmax and AUC24) increases proportionally with once daily doses ranging from 20 mg to 450 mg (0.17 to 3.75 times the recommended dosage) in patients with relapsed or refractory AML. Gilteritinib mean (±SD) steady-state Cmax is 374 ng/mL (±190) and AUC24 is 6943 ng•hr/mL (±3221). Steady-state plasma levels are reached within 15 days of dosing with an approximate 10-fold accumulation.
Absorption
The time to maximum gilteritinib concentration (tmax) observed is approximately between 4 and 6 hours post dose in the fasted state.
Effect of Food
In healthy adults administered a single gilteritinib 40 mg dose (0.3 times the recommended dosage), gilteritinib Cmax decreased by 26% and AUC decreased by less than 10% when co-administered with a high-fat meal (approximately 800 to 1,000 total calories with 500 to 600 fat calories, 250 carbohydrate calories, 150 protein calories) compared to a fasted state. Median tmax was delayed 2 hours when gilteritinib was administered with a high-fat meal.
Distribution
The population mean (%CV) estimates of apparent central and peripheral volume of distribution were 1092 L (9.22%) and 1100 L (4.99%), respectively, which may indicate extensive tissue distribution. In vivo, gilteritinib is approximately 94% bound to human plasma proteins. In vitro, gilteritinib is primarily bound to human serum albumin.
Elimination
The estimated half-life of gilteritinib is 113 hours, and the estimated apparent clearance is 14.85 L/h.
Metabolism
Gilteritinib is primarily metabolized via CYP3A4 in vitro. At steady state, the primary metabolites in humans include M17 (formed via N-dealkylation and oxidation), M16 and M10 (both formed via N‑dealkylation). None of these 3 metabolites exceeded 10% of overall parent exposure.
Excretion
After a single radiolabeled dose, gilteritinib is excreted in feces with 64.5% of the total administered dose recovered in feces. Of the total radiolabeled dose of gilteritinib, 16.4% was recovered in urine as unchanged drug and metabolites.
Specific Populations
Age (20-87 years), sex, race, mild (Child-Pugh Class A) or moderate (Child-Pugh Class B) hepatic impairment and mild (creatinine clearance (CLCr) 50-80 mL/min) or moderate (CLCr 30-50 mL/min) renal impairment do not have clinically meaningful effects on the pharmacokinetics of gilteritinib.
The effect of severe hepatic (Child-Pugh Class C) or severe renal impairment (CLCr ≤ 29 mL/min) on gilteritinib pharmacokinetics is unknown.
Drug Interaction Studies
Clinical Studies
Combined P-gp and Strong CYP3A Inducers:
Gilteritinib Cmax decreased approximately 30% and AUC decreased approximately 70% when co-administered with rifampin (a combined P-gp and strong CYP3A inducer).
Strong CYP3A Inhibitors:
Gilteritinib Cmax increased approximately 20% and AUC increased approximately 120% when co-administered with itraconazole (a strong CYP3A inhibitor).
Moderate CYP3A Inhibitors:
Gilteritinib Cmax increased approximately 16% and AUC increased approximately 40% when co-administered with fluconazole (a moderate CYP3A inhibitor).
CYP3A Substrates:
Midazolam (a CYP3A substrate) Cmax and AUC increased approximately 10% when co-administered with gilteritinib.
MATE1 Substrates:
Cephalexin (a MATE1 substrate) Cmax and AUC decreased by less than 10% when co-administered with gilteritinib.
In Vitro Studies
Gilteritinib inhibits human 5HT2B receptor or sigma nonspecific receptors, which may reduce the effects of drugs that target these receptors such as escitalopram, fluoxetine, sertraline.
Gilteritinib is a substrate of P-gp transporter and has the potential to inhibit breast cancer resistance protein (BCRP) and organic cation transporter 1 (OCT1) transporters.