Defibrotide

Defibrotide has a profibrinolytic effect and this may potentially enhance the activity of antithrombotic/fibrinolytic medicinal products.

There is currently no reported experience in patients on the concomitant treatment with Low Molecular Weight Heparins (LMWHs), warfarin or the concomitant treatment with direct thrombin inhibitors (e.g., dabigatran) or direct Factor Xa inhibitors (e.g., rivaroxaban and apixaban). Therefore, the use of defibrotide with antithrombotic/fibrinolytic medicinal products is not recommended. However, if used, in exceptional cases, caution should be exercised by closely monitoring the coagulation parameters.

In patients who have or develop clinically significant acute bleeding requiring blood transfusion, defibrotide is not recommended or should be discontinued. Temporary discontinuation of defibrotide is recommended in patients who undergo surgery or invasive procedures at significant risk of major bleeding.

Administration of defibrotide to patients who have haemodynamic instability, defined as inability to maintain mean arterial pressure with single pressor support, is not recommended.

There are no studies using defibrotide in pregnant women. Embryo-foetal developmental toxicology studies in pregnant rats and rabbits of defibrotide doses close to the recommended therapeutic human dose, revealed a high rate of haemorrhagic abortion.

Defibrotide should not be used during pregnancy unless the clinical condition of the woman requires treatment with defibrotide.

It is not known whether defibrotide is excreted in human milk. Considering the nature of the medicinal product, a risk to the newborns/infants is not expected. Defibrotide may be used during breastfeeding.

Contraception in males and females

Effective contraception is required for patients and partners of patients during exposure to defibrotide and for one week subsequent to discontinuation.

Fertility

There are no studies investigating the effects of defibrotide on human fertility.

Defibrotide has no or negligible influence on the ability to drive and use machines. However, patients would not be expected to drive or operate machinery due to the nature of the underlying disease.

Summary of the safety profile

The safety evaluation of defibrotide is based on the safety pooled data set, which included patients who received 25 mg/kg/day of defibrotide for the treatment of VOD, from 4 clinical studies: The Phase 3 pivotal treatment study (2005-01), the Treatment-IND study, the dose-finding study (99-118), and a controlled randomised prophylaxis study (2004-000592-33). In the Phase 3 pivotal treatment study, the overall incidence of adverse events was similar in the defibrotide treatment group and in the control group (historical). The tabulated list of adverse reactions incorporates the ADRs observed in the safety pooled data set [ADR = any event reported as possibly related on at least two occasions] and TEAEs observed in the final completed Treatment-IND 2006-05 study [TEAE = any AE that started or worsened in severity after the first dose of defibrotide]. For the adverse reactions reported the highest frequency was used in the table below. The safety data from the pivotal study are supported and confirmed with data from the completed Treatment-IND study.

The most frequent adverse reactions observed during the treatment of hepatic VOD are haemorrhage (including but not limited to gastrointestinal haemorrhage, pulmonary haemorrhage and epistaxis) and hypotension.

In addition, although in the defibrotide studies in VOD there have been no reports of hypersensitivity, cases of hypersensitivity including anaphylaxis were reported from a previously marketed formulation of defibrotide, consequently hypersensitivity is included as an ADR.

Tabulated list of adverse reactions

Adverse reactions observed are listed below, by system organ class and frequency. Within each frequency grouping, undesirable effects are presented in order of decreasing seriousness. Frequencies are defined as: very common (≥1/10), common (≥1/100 to <1/10), uncommon (≥1/1 000 to <1/100), rare (≥1/10 000 to <1/1 000), very rare (<1/10 000).

Paediatric population

In the treatment studies over 50% of the patients were children. In doses above the recommended dose of 25 mg/kg/day there was a higher proportion of patients with bleeding events in the high dose group but since many events occurred in the follow-up period, a clear relationship with defibrotide treatment could not be determined. In the paediatric prevention study at 25 mg/kg/day there was an increased incidence of any bleeding events in the defibrotide group compared with the treatment group.

However there was no difference in incidence of serious bleeding or bleeding events with fatal outcome.

The frequency nature and severity of adverse reactions in children are otherwise the same as in adults. No special precautions are indicated.