Bosentan

證據等級: L5

預測適應症: 10 個

Bosentan: From Pulmonary Arterial Hypertension to Rheumatoid Arthritis

One-Sentence Summary

Bosentan is a dual endothelin receptor antagonist (ETA/ETB) originally approved for pulmonary arterial hypertension (PAH), blocking endothelin-1 (ET-1) signalling to reduce vasoconstriction and pathological vascular remodelling. The TxGNN model predicts it may be effective for Rheumatoid Arthritis, with 1 clinical trial (indirectly relevant, targeting Giant Cell Arteritis) and 16 publications currently supporting this direction — though all human evidence is indirect and efficacy in RA remains unproven in a clinical setting.

Quick Overview

Item	Content
Original Indication	Pulmonary Arterial Hypertension (PAH)
Predicted New Indication	Rheumatoid Arthritis
TxGNN Prediction Score	99.80%
Evidence Level	L4
Singapore Market Status	✗ Not Marketed
Number of Registrations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Detailed mechanism of action data was not available in this evidence pack. Based on pharmacological knowledge, Bosentan is a competitive dual antagonist at both ETA and ETB endothelin receptors. By blocking ET-1 — a potent vasoconstrictor and pro-fibrotic mediator — it reduces pulmonary vascular resistance and inhibits pathological remodelling. This is the basis for its established use in PAH and, in several jurisdictions, for prevention of new digital ulcers in systemic sclerosis.

The mechanistic bridge to rheumatoid arthritis (RA) depends on the role of ET-1 in joint inflammation. ET-1 concentrations are elevated in both the plasma and synovial membrane of RA patients. Through ETA and ETB receptors, ET-1 upregulates TNF-α, IL-1β, and LTB4, amplifying synovitis and sensitising articular nociceptors. Blocking this axis with bosentan may therefore attenuate TNF-driven joint destruction and reduce inflammatory pain — the rationale proposed by the TxGNN model.

Preclinical evidence lends modest biological plausibility: a 2012 mouse study (PMID 22249931) showed bosentan ameliorated collagen-induced arthritis (CIA), the most widely used preclinical RA model, by suppressing ET-system gene expression driven by TNF-α. Further animal work confirmed that endothelins modulate neutrophil recruitment and oedema in zymosan-induced arthritis (PMID 18515326), and that an IL-15 → IFN-γ → endothelin → prostaglandin cascade mediates articular hypernociception (PMID 16766656). However, no human randomised controlled trial in RA has been conducted, and RA already has a mature pipeline of biologic DMARDs (TNF inhibitors, IL-6 inhibitors, JAK inhibitors) as guideline-endorsed standard of care.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT06957002	Phase 2	Not Yet Recruiting	40	Bosentan + glucocorticoids vs glucocorticoids alone in Giant Cell Arteritis (GCA) over 12 months — Note: GCA is an autoimmune large-vessel vasculitis, not RA. Overlapping ET-1 pathobiology makes this informative for safety, but it cannot serve as efficacy evidence for RA.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
22249931	2012	Animal study (CIA model)	Inflammation Research	Bosentan ameliorated collagen-induced arthritis in mice; TNF-α upregulates ET-system genes in the joint, and dual ETA/ETB blockade reduces joint inflammation and damage — the strongest direct mechanistic evidence available
18515326	2008	Animal study	Journal of Leukocyte Biology	ET-1 elevated in RA synovium; ETA/ETB signalling drives neutrophil accumulation, oedema, and LTB4/TNF-α/CXCL-1 release in zymosan-induced arthritis model
16766656	2006	Animal study	PNAS	IL-15 → IFN-γ → endothelin → prostaglandin cascade mediates mechanical hypernociception in mice; dual ETA/ETB receptor antagonism suppressed this pathway — links ET-1 to RA pain pathophysiology
19969421	2010	Animal study	Pain	IL-17 drives articular hypernociception in antigen-induced arthritis; mechanistic overlap with the ET-1 joint pain sensitisation axis
20054770	2009	Case report	Kardiologia Polska	Child with Eisenmenger syndrome on bosentan subsequently diagnosed with juvenile RA; bosentan therapy continued without apparent exacerbation of RA — incidental co-existence with limited safety signal
24268012	2014	Review	Rheum Dis Clin North Am	PAH as complication of connective tissue diseases including RA; reviews ET-1 pathway and bosentan's role in CTD-PAH
16218473	2005	Review	Lupus	PAH as a complication of RA and other CTDs; ET-1 central to isolated pulmonary arteriopathy; bosentan discussed
19487226	2009	Review	Rheumatology (Oxford)	ET-1 role in vasculopathy and PAH secondary to SLE and Sjögren's syndrome; provides mechanistic context for endothelin axis in rheumatic disease
19851110	2010	Review	Current Opinion in Rheumatology	Broad review of rheumatic skin disease; contextualises autoimmune overlap and evolving treatment approaches
21165350	2010	Review	Canadian Respiratory Journal	Targeted PAH therapies (including bosentan) in CTD patients with and without interstitial lung disease; characterises bosentan's effect profile in the connective tissue disease setting

Singapore Market Information

No Singapore Health Sciences Authority (HSA) registrations were found for Bosentan. The drug is not currently marketed in Singapore.

For reference: Bosentan (Tracleer®) holds approved indications in the EU (EMA) and USA (FDA) for pulmonary arterial hypertension (WHO functional class II–III) and prevention of new digital ulcers in systemic sclerosis. Any future Singapore use would require HSA registration or special access pathways.

Safety Considerations

Please refer to the package insert for safety information.

Note for reviewers: Safety data (warnings, contraindications, drug interactions) were not available in this evidence pack. Bosentan is known to carry hepatotoxicity risk (requiring monthly LFT monitoring), is a potent teratogen (Category X), and is a CYP3A4/CYP2C9 inducer with clinically significant drug–drug interactions. These should be formally assessed before any clinical repurposing decision. TFDA package insert retrieval is recommended as the next step.

Conclusion and Next Steps

Decision: Hold

Rationale: Evidence for bosentan in rheumatoid arthritis rests entirely on preclinical animal models and mechanistic in vitro studies (L4). The only registered clinical trial (NCT06957002) targets Giant Cell Arteritis — not RA — and has not yet begun recruiting. With no human proof-of-concept data in RA, no Singapore market authorisation, and mature biologic DMARDs already available as standard of care, the risk-benefit case for repurposing has not been established.

To proceed, the following is needed:

A human proof-of-concept study (Phase 2 RCT) in active RA patients assessing ET-1 blockade on top of standard DMARDs, with synovial ET-1 levels as a biomarker endpoint
Full safety profile retrieval: TFDA or EMA package insert for hepatotoxicity warnings, teratogenicity risk, and drug–drug interaction profile (CYP3A4/2C9 interactions are particularly relevant in RA polypharmacy)
Mechanism of action data from DrugBank (DrugBank ID: DB00559) to formally document the ET-1 → TNF-α / synovitis mechanistic link
Comparative benefit–risk analysis against existing RA standard of care (methotrexate, bDMARDs, JAK inhibitors)
HSA regulatory pathway assessment for potential Singapore market entry
Note: Limited systemic sclerosis (TxGNN Rank 3, L2 evidence, EMA-approved in Europe) represents a more immediately actionable repurposing opportunity for this drug; a parallel report on that indication is recommended
Disclaimer

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