Chemical formula: C₂₉H₄₄N₈O₃ Molecular mass: 552.724 g/mol PubChem compound: 49803313
Gilteritinib fumarate is a FLT3 and AXL inhibitor.
Gilteritinib inhibits FLT3 receptor signalling and proliferation in cells exogenously expressing FLT3 including FLT3-ITD, FLT3-D835Y, and FLT3-ITD-D835Y, and it induces apoptosis in leukemic cells expressing FLT3-ITD.
In patients with relapsed or refractory AML receiving gilteritinib 120 mg, substantial (>90%) inhibition of FLT3 phosphorylation was rapid (within 24 hours after first dose) and sustained, as characterised by an ex vivo plasma inhibitory activity (PIA) assay.
A concentration-related increase in change from baseline of QTcF was observed across gilteritinib doses ranging from 20 to 450 mg. The predicted mean change from baseline of QTcF at the mean steady-state Cmax (282.0 ng/mL) at the 120 mg daily dose was 4.96 msec with an upper 1-sided 95% CI = 6.20 msec.
Following oral administration of gilteritinib, peak plasma concentrations are observed at a median tmax approximately between 4 and 6 hours in healthy volunteers and patients with relapsed or refractory AML. Gilteritinib undergoes first-order absorption with an estimated absorption rate (ka) of 0.43 h-1 with a lag time of 0.34 hours based on population PK modelling. Median steady-state maximum concentration (Cmax) is 282.0 ng/mL (CV% = 50.8), and area under the plasma concentration curve during 24-hour dosing interval (AUC0-24) is 6180 ng·h/mL (CV% = 46.4) after once-daily dosing of 120 mg gilteritinib. Steady-state plasma levels are reached within 15 days of once-daily dosing with an approximate 10-fold accumulation.
In healthy adults, gilteritinib Cmax and AUC decreased by approximately 26% and less than 10%, respectively, when a single 40 mg dose of gilteritinib was co-administered with a high fat meal compared to gilteritinib exposure in fasted state. Median tmax was delayed 2 hours when gilteritinib was administered with a high-fat meal.
The population estimate of central and peripheral volume of distribution were 1092 L and 1100 L, respectively. These data indicate gilteritinib distributes extensively outside of plasma, which may indicate extensive tissue distribution. In vivo plasma protein binding in humans is approximately 90% and gilteritinib is primarily bound to albumin.
Based on in vitro data, gilteritinib is primarily metabolised via CYP3A4. The primary metabolites in humans include M17 (formed via N-dealkylation and oxidation), M16 and M10 (both formed via N-dealkylation) and were observed in animals. None of these three metabolites exceeded 10% of overall parent exposure. The pharmacological activity of the metabolites against FLT3 and AXL receptors is unknown.
In vitro experiments demonstrated that gilteritinib is a substrate of P-gp and BCRP. Gilteritinib may potentially inhibit BCRP, P-gp and OCT1 at clinically relevant concentrations.
After a single dose of [14C]-gilteritinib, gilteritinib is primarily excreted in faeces with 64.5% of the total administered dose recovered in faeces. Approximately 16.4% of the total dose was excreted in urine as unchanged drug and metabolites. Gilteritinib plasma concentrations declined in a bi-exponential manner with a population mean estimated half-life of 113 hours. The estimated apparent clearance (CL/F) based on the population PK model is 14.85 L/h.
In general, gilteritinib exhibited linear, dose-proportional pharmacokinetics after single and multiple dose administration at doses ranging from 20 to 450 mg in patients with relapsed or refractory AML.
A population pharmacokinetic analysis was performed to evaluate the impact of intrinsic and extrinsic covariates on the predicted exposure of gilteritinib in patients with relapsed or refractory AML. Covariate analysis indicated that age (20 years to 90 years), and body weight (36 kg to 157 kg) were statistically significant; however predicted change in gilteritinib exposure was less than 2-fold.
The effect of hepatic impairment on gilteritinib pharmacokinetics was studied in subjects with mild (Child-Pugh Class A) and moderate (Child-Pugh Class B) hepatic impairment. Results indicate unbound gilteritinib exposure in subjects with mild or moderate hepatic impairment is comparable to that observed in subjects with normal hepatic function. The effect of mild hepatic impairment [as defined by NCI-ODWG] on gilteritinib exposure was also assessed using the population PK model and the results demonstrate little difference in predicted steady-state gilteritinib exposure relative to a typical patient with relapsed or refractory AML and normal liver function.
Gilteritinib has not been studied in patients with severe hepatic impairment (Child-Pugh Class C).
The pharmacokinetics of gilteritinib were evaluated in five subjects with severe (CrCL 15 - <30 mL/min) renal impairment and in four subjects with end stage renal disease (CrCL <15 mL/min). A 1.4-fold increase in mean Cmax and 1.5-fold increase in mean AUCinf of gilteritinib was observed in subjects with severe renal impairment or end stage renal disease compared to subjects with normal renal function (n=8).
Adverse reactions not observed in clinical studies, but seen in animals (safety pharmacology/repeat dose toxicity) at exposure levels similar to clinical exposure levels and with possible relevance to clinical use were as follows.
In rats, decreased urination at 30 mg/kg and higher and decreased defecation at 100 mg/kg were observed. In dogs, positive faecal occult blood at 10 mg/kg and higher, a decrease in the blood calcium concentration at 30 mg/kg, and salivation and an increase followed by a decrease in the blood calcium concentration at 100 mg/kg were observed. These changes were observed at plasma exposure levels similar to or less than clinical exposure levels. A possible clinical relevance of these findings is unknown.
In the repeated dose toxicity studies in rats and dogs, target organs of toxicity were the gastrointestinal tract (heamorrhage in dogs), lymphohaematopoietic system (lymphocyte necrosis and bone marrow hypocellularity with changes in haematological parameters), eye (inflammation and lens opacity in rats, fundus colour change in dogs, retinal vacuolation), lung (interstitial pneumonia in rats and inflammation in dogs), kidney (renal tubule changes with a positive urine occult blood reaction) and liver (hepatocyte vacuolation), urinary bladder (epithelial vacuolation), epithelial tissue (ulcer and inflammation), and phospholipidosis (lung and kidney in rats). These changes were observed at plasma exposure levels similar to or less than clinical exposure levels. Reversibility of most of the changes was indicated by the end of the 4-week recovery period. A possible clinical relevance of these findings is unknown.
Gilteritinib did not induce gene mutation or chromosomal aberrations in vitro. The in vivo micronucleus test showed that gilteritinib has a potential to induce micronuclei in mice.
Gilteritinib showed suppressed foetal growth, and induced embryo-foetal deaths and teratogenicity in the embryo-foetal development studies in rats at exposure levels similar to clinical exposure levels. Placental transfer of gilteritinib was shown in the rat resulting in transfer of radioactivity to the foetus similar to that observed in maternal plasma.
Gilteritinib was excreted into the milk of lactating rats with milk concentrations being higher than in maternal plasma. Gilteritinib was distributed through the breast milk to different tissues, except for the brain, of suckling rats.
In the juvenile toxicity study in rats, the minimum lethal dose level (2.5 mg/kg/day) was much lower than that of adult rats (20 mg/kg/day). The gastrointestinal tract was identified as one of the target organs similar as in adult rats.
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