Deferasirox (Page 5 of 8)

8.5 Geriatric Use

Four hundred thirty-one (431) patients greater than or equal to 65 years of age were studied in clinical trials of deferasirox tablets for oral suspension in the transfusional iron overload setting. The majority of these patients had myelodysplastic syndrome (MDS) (n=393). In these trials, elderly patients experienced a higher frequency of adverse reactions than younger patients. Monitor elderly patients for early signs or symptoms of adverse reactions that may require a dose adjustment. Elderly patients are at increased risk for toxicity due to the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy. Dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range.
In elderly patients, including those with MDS, individualize the decision to remove accumulated iron based on clinical circumstances and the anticipated clinical benefit and risks of deferasirox tablets for oral suspension therapy.

8.6 Renal Impairment

Deferasirox tablets for oral suspension is contraindicated in patients with eGFR less than 40 mL/min/1.73 m2 [see Contraindications (4)]. For patients with renal impairment (eGFR 40 to 60 mL/min/1.73 m2), reduce the starting dose by 50% [see Dosage and Administration (2.4)]. Exercise caution in pediatric patients with eGFR between 40 and 60 mL/minute/1.73 m2 [see Dosage and Administration (2.4)]. If treatment is needed, use the minimum effective dose with enhanced monitoring of glomerular and renal tubular function. Individualize dose titration based on improvement in renal injury [see Dosage and Administration (2.4, 2.5)].

Deferasirox tablets for oral suspension can cause glomerular dysfunction, renal tubular toxicity, or both, and can result in acute renal failure. Monitor all patients closely for changes in eGFR and renal tubular dysfunction during deferasirox tablets for oral suspension treatment. If either develops, consider dose reduction, interruption or discontinuation of deferasirox tablets for oral suspension until glomerular or renal tubular function returns to baseline [see Dosage and Administration (2.4, 2.5), Warnings and Precautions (5.1)].

8.7 Hepatic Impairment

Avoid the use of deferasirox tablets for oral suspension in patients with severe (Child-Pugh C) hepatic impairment. For patients with moderate (Child-Pugh B) hepatic impairment, the starting dose should be reduced by 50%. Closely monitor patients with mild (Child-Pugh A) or moderate (Child-Pugh B) hepatic impairment for efficacy and adverse reactions that may require dose titration [see Dosage and Administration (2.4), Warnings and Precautions (5.2)].

10 OVERDOSAGE

Cases of overdose (2 to 3 times the prescribed dose for several weeks) have been reported. In one case, this resulted in hepatitis, which resolved without long-term consequences after a dose interruption. In one pediatric case, a dose of 2 to 3 times the prescribed dose for 6 days, resulted in acute renal failure requiring hemofiltration and acute liver injury/failure, which were reversible with intensive care support. Single doses up to 80 mg per kg per day in iron overloaded beta-thalassemic patients have been tolerated with nausea and diarrhea noted. In healthy volunteers, single doses of up to 40 mg per kg per day were tolerated. There is no specific antidote for deferasirox tablets for oral suspension. In case of overdose, induce vomiting and employ gastric lavage.

11 DESCRIPTION

Deferasirox is an iron chelating agent. Deferasirox tablets for oral suspension contain 125 mg, 250 mg, or 500 mg deferasirox. Deferasirox is designated chemically as 4-[3,5-Bis (2-hydroxyphenyl)-1H-1,2,4-triazol-1-yl]-benzoic acid and its structural formula is:

Structure

Deferasirox is a white to slightly yellow powder. Its molecular formula is C21 H15 N3 O4 and its molecular weight is 373.36 g/mol.

Inactive Ingredients: Crospovidone (NF), sodium starch glycolate (NF), croscarmellose sodium (NF), colloidal silicon dioxide (NF), sodium lauryl sulphate (NF), povidone (K-30) (USP), lactose monohydrate (NF), and magnesium stearate (NF).

12 CLINICAL PHARMACOLOGY

12.1 Mechanism of Action

Deferasirox tablets for oral suspension are an orally active chelator that is selective for iron (as Fe3+). It is a tridentate ligand that binds iron with high affinity in a 2:1 ratio. Although deferasirox has very low affinity for zinc and copper there are variable decreases in the serum concentration of these trace metals after the administration of deferasirox. The clinical significance of these decreases is uncertain.

12.2 Pharmacodynamics

Pharmacodynamic effects tested in an iron balance metabolic study showed that deferasirox (10, 20, and 40 mg per kg per day) was able to induce a mean net iron excretion (0.119, 0.329, and 0.445 mg Fe/kg body weight per day, respectively) within the clinically relevant range (0.1 to 0.5 mg per kg per day). Iron excretion was predominantly fecal.

An analysis of pooled pediatric clinical trial data found a statistically significant relationship between exposure and the probability of renal toxicity (increase in serum creatinine and urinary protein), resulting in a decrease in renal function. Decreases in renal function resulted in an increase in deferasirox exposure, which may increase the probability of renal toxicity.

Cardiac Electrophysiology

At the maximum approved recommended dose, deferasirox does not prolong the QT interval to any clinically relevant extent.

12.3 Pharmacokinetics

Absorption

Deferasirox tablets for oral suspension are absorbed following oral administration with median times to maximum plasma concentration (Tmax ) of about 1.5 to 4 hours. The Cmax and AUC of deferasirox increase approximately linearly with dose after both single administration and under steady-state conditions. Exposure to deferasirox increased by an accumulation factor of 1.3 to 2.3 after multiple doses. The absolute bioavailability (AUC) of deferasirox tablets for oral suspension is 70% compared to an intravenous dose. The bioavailability (AUC) of deferasirox was variably increased when taken with a meal.

Distribution

Deferasirox is highly (~99%) protein bound almost exclusively to serum albumin. The percentage of deferasirox confined to the blood cells was 5% in humans. The volume of distribution at steady state (Vss ) of deferasirox is 14.37 ± 2.69 L in adults.

Metabolism

Glucuronidation is the main metabolic pathway for deferasirox, with subsequent biliary excretion. Deconjugation of glucuronidates in the intestine and subsequent reabsorption (enterohepatic recycling) is likely to occur. Deferasirox is mainly glucuronidated by UGT1A1 and to a lesser extent UGT1A3. CYP450-catalyzed (oxidative) metabolism of deferasirox appears to be minor in humans (about 8%). Deconjugation of glucuronide metabolites in the intestine and subsequent reabsorption (enterohepatic recycling) was confirmed in a healthy volunteer study in which the administration of cholestyramine 12 g twice daily (strongly binds to deferasirox and its conjugates) 4 and 10 hours after a single dose of deferasirox resulted in a 45% decrease in deferasirox exposure (AUC) by interfering with the enterohepatic recycling of deferasirox.

Excretion

Deferasirox and metabolites are primarily (84% of the dose) excreted in the feces. Renal excretion of deferasirox and metabolites is minimal (8% of the administered dose). The mean elimination half-life (t1/2 ) ranged from 8 to 16 hours following oral administration.

Drug Interactions

Midazolam: In healthy volunteers, the concomitant administration of deferasirox tablets for oral suspension and midazolam (a CYP3A4 probe substrate) resulted in a decrease of midazolam peak concentration by 23% and exposure by 17%. In the clinical setting, this effect may be more pronounced. The study was not adequately designed to conclusively assess the potential induction of CYP3A4 by deferasirox [see Drug Interactions (7.2)].

Repaglinide: In a healthy volunteer study, the concomitant administration of deferasirox tablets for oral suspension (30 mg per kg/day for 4 days) and the CYP2C8 probe substrate repaglinide (single dose of 0.5 mg) resulted in an increase in repaglinide systemic exposure (AUC) to 2.3-fold of control and an increase in Cmax of 62% [see Drug Interactions (7.3)].

Theophylline: In a healthy volunteer study, the concomitant administration of deferasirox tablets for oral suspension (repeated dose of 30 mg per kg/day) and the CYP1A2 substrate theophylline (single dose of 120 mg) resulted in an approximate doubling of the theophylline AUC and elimination half-life. The single dose Cmax was not affected, but an increase in theophylline Cmax is expected to occur with chronic dosing [see Drug Interactions (7.4)].

Rifampicin: In a healthy volunteer study, the concomitant administration of deferasirox tablets for oral suspension (single dose of 30 mg per kg) and the potent UDP-glucuronosyltransferase (UGT) inducer rifampicin (600 mg/day for 9 days) resulted in a decrease of deferasirox systemic exposure (AUC) by 44% [see Drug Interactions (7.5)].

Cholestyramine: The concomitant use of deferasirox tablets for oral suspension with bile acid sequestrants may result in a decrease in deferasirox tablets for oral suspension efficacy. In healthy volunteers, the administration of cholestyramine after a single dose of deferasirox resulted in a 45% decrease in deferasirox exposure (AUC) [see Drug Interactions (7.6)].

Busulfan: Concomitant administration of deferasirox and busulfan resulted in an increase of busulfan exposure (AUC).

In vitro Studies:

  • Cytochrome P450 Enzymes: Deferasirox inhibits human CYP3A4, CYP2C8, CYP1A2, CYP2A6, CYP2D6, and CYP2C19 in vitro.
  • Transporter Systems: The addition of cyclosporin A (PgP/MRP1/MRP2 inhibitor) or verapamil (PgP/MRP1 inhibitor) did not influence ICL670 permeability in vitro.

Pharmacokinetics in Specific Populations

Pediatric: Following oral administration of single or multiple doses, systemic exposure of adolescents and children to deferasirox was less than in adult patients. In children less than 6 years of age, systemic exposure was about 50% lower than in adults.

Geriatric: The pharmacokinetics of deferasirox have not been studied in elderly patients (65 years of age or older).

Gender: Females have a moderately lower apparent clearance (by 17.5%) for deferasirox compared to males.

Renal Impairment: Compared to patients with MDS and eGFR greater than 60 mL/min/1.73 m2 , patients with MDS and eGFR 40 to 60 mL/min/1.73 m2 (n=34) had approximately 50% higher mean deferasirox trough plasma concentrations.

Hepatic Impairment: In a single dose (20 mg/kg) study in patients with varying degrees of hepatic impairment, deferasirox exposure was increased compared to patients with normal hepatic function. The average total (free and bound) AUC of deferasirox increased 16% in 6 patients with mild (Child-Pugh A) hepatic impairment, and 76% in 6 patients with moderate (Child-Pugh B) hepatic impairment compared to 6 patients with normal hepatic function. The impact of severe (Child-Pugh C) hepatic impairment was assessed in only 1 patient.

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