Defibrotide

證據等級: L5

預測適應症: 10 個

Defibrotide: From Hepatic Veno-Occlusive Disease (VOD/SOS) Prevention to Thrombotic Thrombocytopenic Purpura

Methodology note: TxGNN's raw #1–#3 and #5–#9 ranked predictions (pseudo-von Willebrand disease, Glanzmann thrombasthenia, Scott syndrome, congenital Factor V deficiency, etc.) are all congenital bleeding disorders. The evidence pack's own rationale flags these as mechanistically backwards — defibrotide is an antithrombotic/profibrinolytic agent, and using it for diseases that already impair clotting could worsen bleeding rather than help. None of these six have any supporting trial or literature evidence (all L5/Hold). This report instead focuses on Thrombotic Thrombocytopenic Purpura (rank 4), the only candidate with real clinical evidence and a mechanistically coherent rationale (the near-identical "thrombocytopenic purpura" at rank 10 shares the same literature set and conclusion).

One-Sentence Summary

Defibrotide's established clinical use — visible in this evidence pack via trial NCT02851407 — is prevention of hepatic veno-occlusive disease/sinusoidal obstruction syndrome (VOD/SOS) in patients undergoing hematopoietic stem cell transplant (HSCT). The TxGNN model's best-supported new-indication signal is Thrombotic Thrombocytopenic Purpura (TTP), backed by 11 publications (cohort studies, reviews, and case reports/series spanning 1984–2023) but no completed clinical trials. Critically, one of those publications reports TTP developing after defibrotide therapy, so this remains an open safety question rather than a settled efficacy signal.

Quick Overview

Item	Content
Original Indication	Not formally captured in this evidence pack (original indication/MOA fields are data gaps); trial evidence (NCT02851407) indicates defibrotide's established use is VOD/SOS prophylaxis in HSCT patients
Predicted New Indication	Thrombotic Thrombocytopenic Purpura
TxGNN Prediction Score	99.71% (rank 3,665 of scored pairs)
Evidence Level	L3
Finland Market Status	✗ Not marketed
Number of Authorizations	0
Recommended Decision	Research Question

Why is This Prediction Reasonable?

Formal mechanism-of-action data for defibrotide is flagged as a data gap in this pack (DG002, High severity). However, the repurposing rationale attached to the evidence itself describes defibrotide as having endothelial-protective and antithrombotic/profibrinolytic activity — consistent with its known role in preventing microvascular thrombosis and endothelial injury in VOD/SOS after HSCT.

TTP and transplant-associated thrombotic microangiopathy (TA-TMA) share the same underlying pathophysiology as VOD/SOS: endothelial injury and microvascular thrombus formation. This mechanistic overlap is why multiple independent case series and cohort reports from 1984–2002 explored defibrotide in TTP/TA-TMA/HUS, and why a 2023 in-vitro study found defibrotide mitigates endothelial cell injury induced by plasma from TMA-related conditions (including COVID-19 vasculopathy).

That said, the evidence is entirely observational — no RCTs exist for this indication — and one 1994 case report describes the opposite causal direction (TTP occurring after defibrotide treatment), which must be weighed against the treatment-oriented reports before any clinical hypothesis is pursued.

Clinical Trial Evidence

Currently no related clinical trials registered for Thrombotic Thrombocytopenic Purpura.

(Note: trial NCT02851407 — a completed Phase 3 HARMONY study of defibrotide for VOD/SOS prophylaxis — appears elsewhere in this evidence pack under "primary release disorder of platelets," but was graded Relevance "C": its actual indication is VOD/SOS, not a platelet-release disorder, and its primary endpoint was negative. It is not counted as supporting evidence for TTP.)

Literature Evidence

PMID	Year	Type	Journal	Key Findings
30305540	2018	Review	Rinsho Ketsueki	Management of transplant-associated thrombotic microangiopathy (TA-TMA)
17603513	2007	Review	Bone Marrow Transplant	Diagnosis/treatment progress in transplantation-associated TMA
19228075	2009	Review	Drugs	TMA in HSCT: diagnosis and treatment, incidence 0.5–76%, mortality 60–90% despite treatment
11100281	2000	Cohort	Bone Marrow Transplant	TTP incidence/risk factors in 131 leukemic children after BMT
11960280	2002	Cohort	Bone Marrow Transplant	"Defibrotide as a promising treatment for TTP in patients undergoing BMT"
10775024	2000	Case Report	Clin Appl Thromb Hemost	Defibrotide used in recurrent/relapsed TTP
7896218	1994	Case Report (adverse)	Haematologica	TTP occurring after defibrotide therapy — opposite-direction safety signal
8317470	1993	Case Series	Am J Hematol	Treatment of TTP with defibrotide
6547211	1984	Case Series	Nephron	Defibrotide as antithrombotic agent in acute renal failure due to HUS/TTP
37001283	2023	Basic Science (in vitro)	Thrombosis Research	Defibrotide mitigates endothelial injury from COVID-19/TMA patient plasma

Finland Market Information

Defibrotide is not currently marketed in Finland — 0 authorizations are on file in this evidence pack.

Safety Considerations

No structured safety data (key warnings, contraindications, DDI) are available for defibrotide in this evidence pack — please refer to the package insert for safety information.

One evidence-derived signal worth flagging separately: PMID 7896218 (Haematologica, 1994) reports a case of TTP developing after defibrotide administration, indicating the drug–disease relationship for this indication may run in either direction and needs dedicated causality assessment before any clinical hypothesis is advanced.

Conclusion and Next Steps

Decision: Research Question

Rationale: The TTP signal is mechanistically plausible and has multi-decade observational support, but rests entirely on cohort/case-level evidence with no RCTs, and includes at least one report of the opposite causal direction. Formal safety data (TFDA/package-insert warnings, DDI) and MOA confirmation are both outstanding blocking/high-severity gaps (DG001, DG002), so this cannot yet clear even an initial safety screen.

To proceed, the following is needed:

TFDA/EMA package insert data (warnings, contraindications) — currently blocking (DG001)
Confirmed mechanism of action from DrugBank or primary literature (DG002)
Adjudication of the causality conflict between defibrotide-as-treatment (PMID 11960280, 10775024, 8317470) vs. defibrotide-as-trigger (PMID 7896218) for TTP
A prospective or registry-based study, since no RCT currently exists for this indication
Disclaimer

This content is for research purposes only and does not constitute medical advice. Clinical validation is required before any clinical application.