Defibrotide (DF) for the Prevention of Hepatic Veno-Occlusive Disease (VOD) in Pediatric Stem Cell Transplantion: Results of a Prospective Phase II/III Randomized, Multicenter Study.

Hepatic VOD is a life-threatening complication following SCT with a particularly high incidence in children. Development of VOD is one of the most common causes of early death after SCT. DF (Gentium SpA), a polydisperse oligonucleotide, demonstrates a protective effect on vascular endothelial cells in vitro. Small non-randomized trials to assess DF for the prophylaxis of VOD were promising without significant anticoagulant effects.

Eligibility criteria included pts <18 years with myeloablative SCT and at least 1 of the following high risk criteria for VOD: conditioning with busulfan and melphalan, pre-existing liver disease, 2nd myeloablative transplant, allo-SCT for leukemia in 2nd relapse, macrophage activating syndromes, prior abdominal irradiation, prior gemtuzumab, osteopetrosis, and adrenoleukodystrophy. Pts were prospectively randomized to the control arm (no prophylactic DF) or to receive DF 25mg/kg/day IV from the start of conditioning until D+30 post SCT. All pts diagnosed with VOD received DF for treatment. Primary endpoint: incidence of hepatic VOD by D+30 using modified Seattle criteria (2 or more of the following: bilirubin > 2 mg/dL, hepatomegaly, ascites and/or unexplained weight gain > 5%). VOD was assessed by physical exam; hepatomegaly and ascites were confirmed by abdominal ultrasound. A blinded independent review committee of 3 expert hematologists confirmed the diagnosis of VOD. Although the study was not powered to assess mortality, a composite score was assessed as a secondary endpoint that incorporated VOD-associated toxicity (respiratory failure, renal failure, encephalopathy) and mortality. Incidence and severity of graft versus host disease (GvHD) was assessed. As the true incidence of VOD in this population was unknown, the trial incorporated a planned adaptive interim analysis to be reviewed by an independent DSMB.

Based on the recommendations of the DSMB, 360 pts were enrolled between January 2006 and January 2009 by 28 centers in the EU and Israel. An Intent-to-Treat (ITT) analysis was performed on all randomized pts who signed informed consent (DF: 180; control: 176). Median age was 4.8 years; 24% infants, 52% children (ages 2-11 years) and 23% adolescents. 41% were female, 59% male. 68% were allo-, 31% auto-SCT. There were no significant differences between the two arms in disease types or risk factors. Ninety-three percent (93%) of the patients completed the primary endpoint at day +30. In the ITT analysis, 12% (22/180) of the pts of the DF arm and 20% (35/176) of the control group developed VOD by D+30 (P=0.054); in the PP analysis, the VOD incidence was 12% (20/164) vs 21% (35/169) (P=0.037). VOD was experienced by 23% of the infants, 14% of the children and 13% of the adolescents. The composite score (assessing VOD morbidity and mortality) was significantly in favor of the DF arm (P=0.034). Significantly less acute GvHD by D+100 was reported in the DF pts (32% (57/180) vs 43% (75/176); P=0.023 by Wilcoxon test). Observation of VOD in either arm led to a higher mortality: mortality of pts with VOD equaled 24.6% (14/57) compared to 7% in pts without VOD (21/299). Renal failure was observed in 1% (2/180 pts) of DF pts vs 6% (10/176) of the control (P=0.017); respiratory failure was observed in 7% vs 9% (NS); and encephalopathy in 1% vs 2% (NS). SAEs were experienced by 58% of the DF pts vs 59% of the control, including infections (24% vs 27%) and respiratory disorders (12% vs 9%); 9 hemorrhagic events were seen in the DF arm compared to 21 in the control.

This Phase II/III randomized study demonstrates the efficacy and safety of DF in preventing VOD in pediatric pts at high risk of VOD. Use of prophylactic DF results in a 40% reduction in the incidence of VOD. Consistent with the role of DF in endothelial protection, both renal failure and acute GvHD were significantly lower in the DF arm. Safety of DF was confirmed by lack of significant toxicity (including hemorrhage). DF can be recommended for the prevention of VOD in this high risk population.

Corbacioglu:Gentium S.p.A.: Consultancy, Research Funding. Massaro:Gentium S.p.A.: Consultancy. D'Agostino:Gentium S.p.A.: Consultancy, Membership on an entity's Board of Directors or advisory committees. Hoyle:Gentium S.p.A.: Employment. Iacobelli:Gentium: Employment.