DEFITELIO Solution for injection Ref.[9989] Active ingredients: Defibrotide

Cardiac Electrophysiology

At a dose 2.4 times the maximum recommended dose, DEFITELIO does not prolong the QTc interval to any clinically relevant extent.

PAI-1 Inhibition

Plasma concentrations of PAI-1 were assessed on an exploratory basis as a potential pharmacodynamic marker for efficacy in Study 2. PAI-1 is an inhibitor of t-PA and therefore of fibrinolysis. Mean PAI-1 levels on Days 7 and 14 were lower than those at baseline in patients with complete response (CR) and in those who were alive at Day+100, but this trend did not reach statistical significance. There were no statistically significant differences in mean PAI-1 levels by treatment or outcome.

Absorption

After intravenous administration, peak plasma concentrations of defibrotide sodium occur approximately at the end of each infusion.

Distribution

Defibrotide sodium is highly bound to human plasma proteins (average 93%) and has a volume of distribution of 8.1 to 9.1 L.

Elimination

Metabolism followed by urinary excretion is likely the main route of elimination. The estimated total clearance was 3.4 to 6.1 L/h. The elimination half-life of defibrotide sodium is less than 2 hours. Similar plasma concentration profiles were observed in VOD patients after initial and multiple-dose administration of 6.25 mg/kg every 6 hours for 5 days. Therefore, no accumulation is expected following multiple-dose administration.

Metabolism

Though the precise pathway of defibrotide sodium degradation in plasma in vivo is largely unknown, it has been suggested that nucleases, nucleotidases, nucleosidases, deaminases, and phosphorylases metabolize polynucleotides progressively to oligonucleotides, nucleotides, nucleosides, and then to the free 2'-deoxyribose sugar, purine and pyrimidine bases.

The biotransformation of defibrotide sodium was investigated in vitro by incubation with human hepatocytes from donors of different ages and showed that defibrotide sodium does not undergo appreciable metabolism by human hepatocyte cells.

Excretion

After administration of 6.25 mg/kg to 15 mg/kg doses of DEFITELIO as 2-hour infusions, approximately 5-15% of the total dose was excreted in urine as defibrotide sodium, with the majority excreted during the first 4 hours.

Specific Populations

Age: Pediatric Population

Insufficient PK data were collected in pediatric patients to draw conclusions.

Renal Impairment

The safety, tolerability, and pharmacokinetics of 6.25 mg/kg as 2-hour intravenous infusions of DEFITELIO were evaluated in patients with Hemodialysis-dependent End Stage Renal Disease (ESRD) during hemodialysis and on days off dialysis, and in patients with severe renal disease or ESRD not requiring dialysis. Defibrotide sodium was not removed by hemodialysis, which had no notable effect on plasma clearance of defibrotide sodium. Terminal half-lives were consistently less than 2 hours, and there was no accumulation of defibrotide sodium following repeated dosing. Defibrotide sodium exposure (AUC) in patients with severe renal impairment or ESRD was 50% to 60% higher than that observed in matched healthy subjects. Peak concentration (C_max) was 35% to 37% higher following single- and multiple-dose administration of defibrotide sodium.

Drug Interactions

Pharmacokinetic drug-drug interactions are unlikely at therapeutic dose. Data from in vitro studies using human biomaterial demonstrate that defibrotide sodium does not induce (CYP1A2, CYP2B6, CYP3A4, UGT1A1) or inhibit (CYP1A2, CYP2B6, CYP3A4, CYP2C8, CYP2C9, CYP2C19, CYP2D6, UGT1A1, UGT2B7) the major drug metabolizing enzymes and is not a substrate or inhibitor of the major drug uptake transporters (OAT1, OAT3, OCT1, OCT2, OATP1B1, OATP1B3) or efflux transporters (P-gp and BCRP).

There is some evidence (animal studies, ex vivo human plasma, and healthy volunteers) that defibrotide sodium may enhance the pharmacodynamic activity of heparin and alteplase [see Drug Interactions (7)].

No carcinogenicity studies have been conducted with intravenous administration of defibrotide sodium.

Defibrotide sodium was not mutagenic in vitro in a bacterial reverse mutation assay (Ames assay). Defibrotide sodium was not clastogenic in an in vitro chromosomal aberrations assay in Chinese hamster ovary cells or an in vivo micronucleus assay conducted in bone marrow from rats administered defibrotide sodium by intravenous infusion.

Studies of fertility were not conducted with defibrotide sodium administered by the intravenous route. In repeat dose general toxicology studies, when defibrotide sodium was administered intravenously to rats and dogs for up to 13 weeks, there were no effects on male or female reproductive organs.

In the 13-week toxicity studies in rats and dogs, intravenous administration of defibrotide sodium transiently prolonged activated partial thromboplastin time (APTT) at 1200 and 4800 mg/kg/day administered as a continuous infusion in rats and at 300 and 1600 mg/kg/day administered in 2-hour infusions 4 times daily in dogs. Prothrombin time (PT) was also transiently increased at 4800 mg/kg/day in rats. These findings were observed at doses at least 6 times higher on a mg/m² basis than the clinical dose of 25 mg/kg/day. The effects on APTT and PT may be due to direct effects on coagulation based on the dose-dependent response observed.

The efficacy of DEFITELIO was investigated in three studies: two prospective clinical trials (Study 1 and Study 2), and an expanded access study (Study 3).

Study 1 enrolled 102 adult and pediatric patients in the DEFITELIO treatment group with a diagnosis of VOD according to the following criteria (bilirubin of at least 2 mg/dL and at least two of the following findings: hepatomegaly, ascites, and weight gain greater than 5% by Day+21 post-HSCT) with an associated diagnosis of multi-organ dysfunction (pulmonary, renal, or both) by Day+28 post-HSCT. DEFITELIO was administered to the treatment group at a dose of 6.25 mg/kg infused every 6 hours for a minimum of 21 days and continued until patient was discharged from the hospital. Patients enrolled in the DEFITELIO treatment group were not permitted to receive concomitant medications such as heparin, warfarin, or alteplase because of an increased risk of bleeding.

Study 2 included adult and pediatric patients with a diagnosis of hepatic VOD and multi-organ dysfunction following HSCT, with 75 patients treated with DEFITELIO at a dose of 6.25 mg/kg infused every 6 hours. The planned minimum duration of treatment was 14 days. The treatment could be continued until signs of hepatic VOD resolved.

Study 3 is an expanded access program for DEFITELIO for the treatment of adult and pediatric patients with hepatic VOD. The efficacy of defibrotide was evaluated in 351 patients who had received a HSCT and developed hepatic VOD with renal or pulmonary dysfunction. All patients received DEFITELIO at a dose of 6.25 mg/kg infused every 6 hours.

Baseline demographic information and details for patients treated in these studies are provided below in Table 3.

Table 3. Baseline Demographics of Patients Treated with DEFITELIO at 6.25 mg/kg Every 6 Hours:

^a Duration of treatment from first dose to last dose is presented because days without treatment were not captured for the expanded access study.

The efficacy of DEFITELIO was based on survival at Day + 100 after HSCT. In Study 1, the survival rate was 38% (95% CI: 29%, 48%) at 100 days after transplantation. In Study 2 the survival rate was 44% (95% CI: 33%, 55%) at 100 days after transplantation. In Study 3, the Day + 100 survival was 45% (95% CI: 40%, 51%).

Based on published reports and analyses of patient level data for individuals with hepatic VOD with renal or pulmonary dysfunction who received supportive care or interventions other than DEFITELIO, the expected Day +100 survival rates are 21% to 31%.