Pooled Treatment Analysis of Pediatric Patients with Defibrotide for Hepatic Veno-Occlusive Disease/Sinusoidal Obstruction Syndrome and Multi-Organ Dysfunction Following Hematopoietic Stem Cell Transplant

Introduction

Hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) is an unpredictable, potentially life-threatening complication of conditioning regimens for hematopoietic stem cell transplant (HSCT). Severe hepatic VOD/SOS (ie, with multi-organ dysfunction [MOD]), may be associated with >80% mortality. Defibrotide (DF) is approved for treatment of severe hepatic VOD/SOS in the European Union. In the United States, DF is available through an ongoing expanded-access protocol.

Methods

DF treatment for hepatic VOD/SOS with MOD is being assessed in a clinical program in pediatric and adult patients, including a phase 2 dose-finding trial, a pivotal phase 3 study of DF compared to historical controls (HC), and a single-arm expanded-access program. In the phase 2 dose-finding study, patients were randomized to receive 25 or 40 mg/kg/day. In the other 2 studies, treated patients received DF 25 mg/kg/d. DF was given in 4 divided doses for a recommended ≥14 days (dose-finding trial) or ≥21 days (pivotal and expanded-access studies). VOD/SOS was defined in each study by Baltimore and/or modified Seattle criteria. Here, we report results for treatment with DF 25 mg/kg/day in pediatric patients (aged ≤16y) with VOD/SOS plus MOD post-HSCT across these 3 studies.

Results

A pooled efficacy analysis included 255 pediatric patients with VOD/SOS and MOD post-HSCT who received DF 25 mg/kg/d in the dose-finding trial (n=22), pivotal trial (n=44), and expanded-access program (n=189). Among patients, 29.8% (n=76) were aged 0-23 mo, 48.6% (n=124) aged 2-11y, and 21.6% (n=55) aged 12-16y. 83.9% received allogeneic transplants (98.7% of patients aged 0-23 mo; 66.7% of patients aged 2-11y; 100% of patients aged 12-16y) and 16.1% received autologous transplants (1.3%, 0-23 mo; 32.3%, 2-11y; none, 12-16y). Acute leukemia (41.2%) was the most common primary disease (23.7%, 0-23 mo; 40.3%, 2-11y; 67.3%, 12-16y).

At day +100 following HSCT, the survival rate in the overall pediatric population was 51.4% (95% CI, 45.2%-57.5%; n=131/255). Day +100 survival by age subgroup was 52.6% (95% CI, 41.4%-63.9%; n=40/76) in patients aged 0-23 mo, 53.2% (95% CI, 44.4%-62.0%; n=66/124) in those aged 2-11y, and 45.5% (95% CI, 32.3%-58.6%; n=25/55) in patients aged 12-16y.

A safety analysis pooled data from the dose-finding and the pivotal trials, which incorporated on-site data monitoring, included 65 children who received DF at a dose of 25 mg/kg/day and 14 children in the HC group. At least 1 AE was reported for 93.8% (61/65) of DF-treated patients from these trials (95.5%, 0-23 mo; 89.7%, 2-11y; 100%, 12-16y), and for all HC patients. Overall AE profiles were generally similar between treated and HC patients. In these 2 trials, 67.7% of pediatric patients receiving 25 mg/kg/day DF had ≥1 serious AE (77.3%, 0-23 mo; 58.6%, 2-11y; 71.4%, 12-16y). Treatment-related AEs (TR-AEs) were reported in 44.6% of patients (31.8%, 0-23 mo; 44.8%, 2-11y; 64.3%, 12-16y). The most common TR-AE overall was pulmonary alveolar hemorrhage (2 patients per age group: 9.1%, 0-23 mo; 6.9%, 2-11y; 14.3%, 12-16y). AEs leading to death were reported for 49.2% (32/65) of patients from these 2 trials (72.7%, 0-23 mo; 31.0%, 2-11y; 50.0%, 12-16y) and 57.1% of HC patients (8/14; 40.0%, 0-23 mo; 85.7%, 2-11y; none, 12-16y). In the expanded-access program, ≥1 serious AE occurred in 98 (51.9%) patients ≤16y old; TR-AEs occurred in 41 (21.7%) of patients ≤16y old, most commonly pulmonary hemorrhage (6.9%), gastrointestinal hemorrhage (3.7%), and hypotension (3.7%).

Conclusions

In this pooled analysis of data from pediatric patients with VOD/SOS and MOD enrolled in 3 DF studies, day +100 survival was generally consistent across pediatric age subgroups. The safety profile in pediatric patients with VOD/SOS and MOD was generally consistent with what would be expected for this critically ill population.

Support: Jazz Pharmaceuticals.