Defibrotide for late-onset sinusoidal obstruction syndrome following umbilical cord blood transplantation: a single-center retrospective study.

Late-onset sinusoidal obstruction syndrome (SOS) after allogeneic hematopoietic cell transplantation remains difficult to diagnose and treat. We retrospectively analyzed 14 umbilical cord blood transplant recipients who developed late-onset SOS and received defibrotide at Toranomon Hospital between 2019 and 2021. All patients presented with very severe SOS accompanied by multiorgan failure. The cumulative incidence of complete remission was 35.7% at one year after initiation of defibrotide therapy. Overall survival was 57.1% at day 100 and 35.7% at two years after SOS diagnosis. Patients with anicteric SOS tended to have better survival than those with icteric disease. Defibrotide was generally well tolerated, with only two grade ≥ 3 bleeding events. Despite the small sample size and retrospective design, these findings suggest that Defibrotide may provide clinical benefit in patients with late-onset SOS following umbilical cord blood transplantation.