Defibrotide

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# Overview
Defibrotide is an oligonucleotide mixture with profibrinolytic properties that is FDA approved for the treatment of adult and pediatric patients with hepatic veno-occlusive disease (VOD), with renal or pulmonary dysfunction following hematopoietic stem-cell transplantation (HSCT).   Common adverse reactions include hypotension, diarrhea, vomiting, nausea, and epistaxis (10%).

# Adult Indications and Dosage

## FDA-Labeled Indications and Dosage (Adult)
Defibrotide is indicated for the treatment of adult and pediatric patients with hepatic veno-occlusive disease (VOD), also known as sinusoidal obstruction syndrome (SOS), with renal or pulmonary dysfunction following hematopoietic stem-cell transplantation (HSCT).
The recommended dosage of Defibrotide for adult and pediatric patients is 6.25 mg/kg every 6 hours given as a 2hour intravenous infusion. The dose should be based on patients baseline body weight, defined as the patients weight prior to the preparative regimen for HSCT.
Administer Defibrotide for a minimum of 21 days. If after 21 days signs and symptoms of hepatic VOD have not resolved, continue Defibrotide until resolution of VOD or up to a maximum of 60 days.
- Treatment Modification
Treatment modification, including temporary or permanent discontinuation of Defibrotide, should follow the recommendations in Table 1.
- Table 1: Treatment Modifications for Toxicity or Invasive Procedures
DEFITELIO: Defibrotide's Brand name

## Off-Label Use and Dosage (Adult)

# Pediatric Indications and Dosage

## FDA-Labeled Indications and Dosage (Pediatric)
Defibrotide is indicated for the treatment of adult and pediatric patients with hepatic veno-occlusive disease (VOD), also known as sinusoidal obstruction syndrome (SOS), with renal or pulmonary dysfunction following hematopoietic stem-cell transplantation (HSCT).
The recommended dosage of Defibrotide for adult and pediatric patients is 6.25 mg/kg every 6 hours given as a 2hour intravenous infusion. The dose should be based on patients baseline body weight, defined as the patients weight prior to the preparative regimen for HSCT.
Administer Defibrotide for a minimum of 21 days. If after 21 days signs and symptoms of hepatic VOD have not resolved, continue Defibrotide until resolution of VOD or up to a maximum of 60 days.
- Treatment Modification
Treatment modification, including temporary or permanent discontinuation of Defibrotide, should follow the recommendations in Table 1.

## Off-Label Use and Dosage (Pediatric)

# Contraindications
The use of Defibrotide is contraindicated in the following conditions:

# Warnings
- Hemorrhage
Defibrotide increased the activity of fibrinolytic enzymes in vitro, and it may increase the risk of bleeding in patients with VOD after hematopoietic stem-cell transplantation (HSCT). Do not initiate Defibrotide in patients with active bleeding. Monitor patients for signs of bleeding. If patients on Defibrotide develop bleeding, discontinue Defibrotide, treat the underlying cause, and provide supportive care until the bleeding has stopped.
Concomitant use of Defibrotide and a systemic anticoagulant or fibrinolytic therapy (not including use for routine maintenance or reopening of central venous lines) may increase the risk of bleeding. Discontinue anticoagulants and fibrinolytic agents prior to Defibrotide treatment, and consider delaying the start of Defibrotide administration until the effects of the anticoagulant have abated.
- Hypersensitivity Reactions
Hypersensitivity reactions have occurred in less than 2% of patients treated with Defibrotide. These reactions include rash, urticaria and angioedema. One case of an anaphylactic reaction was reported in a patient who had previously received Defibrotide. Monitor patients for hypersensitivity reactions, especially if there is a history of previous exposure. If a severe hypersensitivity reaction occurs, discontinue Defibrotide, treat according to the standard of care, and monitor until symptoms resolve.

# Adverse Reactions

## Clinical Trials Experience
The following adverse reactions are discussed in greater detail in other sections of the labeling:
- Hemorrhage
- Hypersensitivity Reactions
Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice.
The safety of Defibrotide was determined in 176 adult and pediatric patients with hepatic VOD with pulmonary and/or renal dysfunction following HSCT who were treated with Defibrotide 6.25 mg/kg every 6 hours. Patients were excluded from these trials if at time of study entry they had significant acute bleeding, active grades B-D graft-versus-host disease, or a requirement for multiple vasopressors to provide blood pressure support. For the purposes of adverse event recording in the clinical trials, events were not required to be reported if they were related to the hepatic VOD, or if they were expected to occur after hematopoietic stem-cell transplantation (HSCT), unless they were serious or Grade 4-5.
The median age of the safety population was 25 years (range: 1 month to 72 years), and 63% were 17 years of age. A total of 60% of patients were male, 78% were white, 89% had undergone allogeneic HSCT, and the underlying diagnosis was acute leukemia for 43%. At study entry, 13% were dialysis dependent and 18% were ventilator dependent. Defibrotide was administered for a median of 21 days (range: 1 to 83 days).
Information about adverse reactions resulting in permanent discontinuation of Defibrotide was available for 102 patients, and 35 (34%) of these patients had an adverse reaction with permanent discontinuation. Adverse reactions leading to permanent discontinuation included pulmonary alveolar hemorrhage in 5 (5%) patients; pulmonary hemorrhage, hypotension, catheter site hemorrhage, and multi-organ failure, each in 3 (3%) patients; and cerebral hemorrhage and sepsis, each in 2 (2%) patients.
Information about adverse reactions of any grade was available for all 176 patients. The most common adverse reactions (incidence 10% and independent of causality) were hypotension, diarrhea, vomiting, nausea, and epistaxis. The most common serious adverse reactions (incidence 5% and independent of causality) were hypotension (11%) and pulmonary alveolar hemorrhage (7%). Hemorrhage events of any type and any grade were reported for 104 (59%) of the patients, and the events were grade 4-5 in 35 (20%).
Table 2 presents adverse reactions independent of causality 10% any grade or Grade 4/5 2% reported in patients treated with Defibrotide.
- Table 2: Adverse Reactions(a) 10% or Grade 4-5 Adverse Reactions 2%
DEFITELIO: Defibrotide's Brand name

## Postmarketing Experience
There is limited information regarding Defibrotide Postmarketing Experience in the drug label.

# Drug Interactions
- Antithrombotic Agents
Defibrotide may enhance the pharmacodynamic activity of antithrombotic/fibrinolytic drugs such as heparin or alteplase. Concomitant use of Defibrotide with antithrombotic or fibrinolytic drugs is contraindicated because of an increased risk of hemorrhage.

# Use in Specific Populations

### Pregnancy
Pregnancy Category (FDA): N
- Risk Summary
There are no available data on Defibrotide use in pregnant women. When administered to pregnant rabbits during the period of organogenesis at doses that were comparable to the recommended human dose based on body surface area, Defibrotide sodium decreased the number of implantations and viable fetuses. Advise pregnant women of the potential risk of miscarriage.
The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risks of major birth defects and miscarriage in clinically recognized pregnancies are 2-4% and 15-20%, respectively.
- Data
- Animal Data
Embryo-Fetal toxicity assessment was attempted in rats and rabbits, but was not possible because of high maternal mortality, abortion, and fetal resorption at all doses. Pregnant rats were administered Defibrotide sodium from gestational day (GD) 6 to 15 at 0, 240, 1200, and 4800 mg/kg/day by continuous intravenous infusion over 24 hours or at 60, 120, and 240 mg/kg/day by 2-hour infusions 4 times per day. Pregnant rabbits were administered Defibrotide sodium at 0, 30, 60, or 120 mg/kg/day from GD 6 to 18 by 2-hour infusions 4 times per day.
In another study in pregnant rabbits, 3 separate subgroups of animals were treated with doses of 80 mg/kg/day Defibrotide sodium administered by 2-hour infusions 4 times per day for 5 days each in a staggered manner during the organogenesis period. The dose of 80 mg/kg/day is approximately equivalent to the recommended clinical dose on a mg/m2 basis. Subgroup 1 was dosed from GD 6 to 10, subgroup 2 was dosed from GD 10 to 14, and subgroup 3 was dosed from GD 14 to 18. An increased incidence of unilateral implantation was observed in Defibrotide sodium-treated animals. Treatment with Defibrotide sodium resulted in a decreased number of implantations and viable fetuses.
Pregnancy Category (AUS): 
There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Defibrotide in women who are pregnant.

### Labor and Delivery
There is no FDA guidance on use of Defibrotide during labor and delivery.

### Nursing Mothers
There is no information regarding the presence of Defibrotide in human milk, the effects on the breastfed infant, or the effects on milk production. Because of the potential for serious adverse reactions, including bleeding in a breastfed infant, advise patients that breastfeeding is not recommended during treatment with Defibrotide.

### Pediatric Use
The safety and effectiveness of Defibrotide have been established in pediatric patients. Use of Defibrotide is supported by evidence from an adequate and well-controlled study and a dose finding study of Defibrotide in adult and pediatric patients with VOD with evidence of renal or pulmonary dysfunction following HSCT. The clinical trials enrolled 66 pediatric patients in the following age groups: 22 infants (1 month up to less than 2 years), 30 children (2 years up to less than 12 years), and 14 adolescents (12 years to less than 17 years). The efficacy and safety outcomes were consistent across pediatric and adult patients in the clinical trials.
- Juvenile Animal Toxicity Data
A juvenile toxicity study in 21-day-old rats was conducted with intravenous bolus administration of Defibrotide sodium at 40, 150, or 320 mg/kg/day for 4 weeks. A delayed mean age of preputial separation was observed at all doses, suggesting a delay in onset of male puberty. The dose of 40 mg/kg/day is approximately 0.4 times the clinical dose on a mg/m2 basis for a child. The relevance of this finding for the onset of male puberty in humans is unknown.

### Geriatic Use
Clinical studies of Defibrotide did not include sufficient numbers of subjects aged 65 and over to determine whether they respond differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients.

### Gender
There is no FDA guidance on the use of Defibrotide with respect to specific gender populations.

### Race
There is no FDA guidance on the use of Defibrotide with respect to specific racial populations.

### Renal Impairment
There is no FDA guidance on the use of Defibrotide in patients with renal impairment.

### Hepatic Impairment
There is no FDA guidance on the use of Defibrotide in patients with hepatic impairment.

### Females of Reproductive Potential and Males
There is no FDA guidance on the use of Defibrotide in women of reproductive potentials and males.

### Immunocompromised Patients
There is no FDA guidance one the use of Defibrotide in patients who are immunocompromised.

# Administration and Monitoring

### Administration
- Administration Instructions
- Defibrotide must be diluted prior to infusion.
- Prior to administration of Defibrotide, confirm that the patient is not experiencing clinically significant bleeding and is hemodynamically stable on no more than one vasopressor.
- Administer Defibrotide by constant intravenous infusion over a 2-hour period.
- Administer the diluted Defibrotide solution using an infusion set equipped with a 0.2 micron in-line filter. Flush the intravenous administration line (peripheral or central) with 5% Dextrose Injection, USP or 0.9% Sodium Chloride Injection, USP immediately before and after administration.
- Do not coadminister Defibrotide and other intravenous drugs concurrently within the same intravenous line.
- Preparation Instructions
Dilute Defibrotide in 5% Dextrose Injection, USP or 0.9% Sodium Chloride Injection, USP to a concentration of 4 mg/mL to 20 mg/mL. Administer the diluted solution over 2 hours.
Vials contain no antimicrobial preservatives and are intended for a single-patient-use only. Partially used vials should be discarded. Use the diluted Defibrotide solution within 4 hours if stored at room temperature or within 24 hours if stored under refrigeration. Up to four doses of Defibrotide solution may be prepared at one time, if refrigerated.
Preparation Instructions:
- Determine the dose (mg) and number of vials of Defibrotide based on the individual patients baseline weight (weight prior to the preparative regimen for HSCT).
- Calculate the volume of Defibrotide needed, withdraw this amount from the vial(s) and add it to the infusion bag containing 0.9% Sodium Chloride Injection or 5% Dextrose Injection for each dose to make a final concentration of 4 mg/mL to 20 mg/mL.
- Gently mix the solution for infusion.
- Parenteral drug products should be inspected visually for particulate matter and discoloration prior to administration, whenever solution and container permit. Only clear solutions without visible particles should be used. Depending on the type and amount of diluent, the color of the diluted solution may vary from colorless to light yellow.

### Monitoring
There is limited information regarding Defibrotide Monitoring in the drug label.

# IV Compatibility
There is limited information regarding the compatibility of Defibrotide and IV administrations.

# Overdosage
There are no known cases of overdose with Defibrotide. There is no known antidote for Defibrotide, and Defibrotide is not dialyzable. If an overdose occurs, institute general supportive measures.

# Pharmacology

## Mechanism of Action
The mechanism of action of Defibrotide sodium has not been fully elucidated. In vitro, Defibrotide sodium enhances the enzymatic activity of plasmin to hydrolyze fibrin clots. Studies evaluating the pharmacological effects of Defibrotide sodium on endothelial cells (ECs) were conducted primarily in the human microvascular endothelial cell line. In vitro, Defibrotide sodium increased tissue plasminogen activator (t-PA) and thrombomodulin expression, and decreased von Willebrand factor (vWF) and plasminogen activator inhibitor1 (PAI-1) expression, thereby reducing EC activation and increasing ECmediated fibrinolysis. Defibrotide sodium protected ECs from damage caused by chemotherapy, tumor necrosis factor- (TNF-), serum starvation, and perfusion.

## Structure
Defibrotide sodium is an oligonucleotide mixture with profibrinolytic properties. The chemical name of Defibrotide sodium is polydeoxyribonucleotide, sodium salt. Defibrotide sodium is a polydisperse mixture of predominantly single-stranded (ss) polydeoxyribonucleotide sodium salts derived from porcine intestinal tissue having a mean weighted molecular weight of 13-20 kDa, and a potency of 27-39 and 28-38 biological units per mg as determined by two separate assays measuring the release of a product formed by contact between Defibrotide sodium, plasmin and a plasmin substrate. The primary structure of Defibrotide sodium is shown below.
Defibrotide sodium injection is a clear, light yellow to brown, sterile, preservative-free solution in a single-patient-use vial for intravenous use. Each milliliter of the injection contains 80 mg of Defibrotide sodium and 10 mg of Sodium Citrate, USP, in Water for Injection, USP. Hydrochloric Acid, NF, and/or Sodium Hydroxide, NF, may have been used to adjust pH to 6.8-7.8.

## Pharmacodynamics
- Cardiac Electrophysiology
At a dose 2.4 times the maximum recommended dose, Defibrotide 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.

## Pharmacokinetics
- 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 Defibrotide 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 Defibrotide 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 (Cmax) 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.

## Nonclinical Toxicology
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.

# Clinical Studies
The efficacy of Defibrotide 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 Defibrotide 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. Defibrotide 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 Defibrotide 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 Defibrotide 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 Defibrotide 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 Defibrotide 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 Defibrotide at 6.25 mg/kg Every 6 Hours
The efficacy of Defibrotide 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 Defibrotide, the expected Day +100 survival rates are 21% to 31%.

# How Supplied
Defibrotide sodium injection is supplied in a single-patient-use, clear glass vial as a clear, light yellow to brown, sterile, preservative-free solution for intravenous infusion. Each vial (NDC 68727-800-01) contains 200 mg/2.5 mL (at a concentration of 80 mg/mL) of Defibrotide sodium.
Each carton of Defibrotide sodium injection (NDC 68727-800-02) contains 10 vials.

## Storage
Store Defibrotide sodium injection at 20C-25C (68F-77F); excursions permitted between 15C to 30C (59F to 86F).

# Images

## Drug Images

## Package and Label Display Panel

# Patient Counseling Information
- Hemorrhage: Advise patients and caregivers that Defibrotide may increase the risk of bleeding (hemorrhage). Instruct patients to immediately report any signs or symptoms suggestive of hemorrhage (unusual bleeding, easy bruising, blood in urine or stool, headache, confusion, slurred speech, or altered vision).
- Hypersensitivity Reactions: Ask patients if they have been treated with Defibrotide sodium previously. Instruct patients on the risk of allergic reactions, including anaphylaxis. Describe the symptoms of allergic reactions, including anaphylaxis, and instruct the patient to seek medical attention immediately if they experience such symptoms.

# Precautions with Alcohol
Alcohol-Defibrotide interaction has not been established. Talk to your doctor regarding the effects of taking alcohol with this medication.

# Brand Names
DEFITELIO

# Look-Alike Drug Names
There is limited information regarding Defibrotide Look-Alike Drug Names in the drug label.

# Drug Shortage Status

# Price