Mesalazine

證據等級: L5

預測適應症: 7 個

Mesalazine: From Ulcerative Colitis to Rheumatoid Arthritis

One-Sentence Summary

Mesalazine (5-aminosalicylic acid, 5-ASA) is the pharmacologically active metabolite of sulfasalazine, primarily established as a first-line therapy for ulcerative colitis and inflammatory bowel disease. The TxGNN model predicts it may have therapeutic utility in Rheumatoid Arthritis (RA) — a disease for which its parent compound sulfasalazine was originally designed in the 1940s — with 6 clinical trials and 20 publications currently supporting this research direction. Notably, however, the dominant body of historical evidence suggests sulfapyridine (not mesalazine) is the primary DMARD-active moiety in sulfasalazine, making this repurposing hypothesis mechanistically plausible but requiring direct clinical validation.

Quick Overview

Item	Content
Original Indication	Ulcerative colitis / Inflammatory bowel disease
Predicted New Indication	Rheumatoid Arthritis
TxGNN Prediction Score	99.57%
Evidence Level	L3
India Market Status	✗ Not Marketed
Number of Registrations	0
Recommended Decision	Proceed with Guardrails

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data for Mesalazine is not formally available in this evidence pack. Based on known pharmacology, Mesalazine (5-ASA) is a salicylate-based anti-inflammatory agent that suppresses mucosal and systemic inflammation through multiple mechanisms: inhibition of the NF-κB signaling pathway (reducing TNF-α and IL-1β transcription), suppression of both COX and LOX branches of the arachidonic acid cascade (lowering PGE2 and LTB4 levels), and agonism of PPARγ (promoting resolution of inflammation and protection of extracellular matrix-producing cells). These are among the most conserved pathways in chronic inflammatory diseases.

The connection to rheumatoid arthritis is historically grounded. Sulfasalazine — the prodrug from which mesalazine is released by colonic bacterial azoreductases — was explicitly designed in the 1940s to treat rheumatoid polyarthritis, and only later found to be highly effective in IBD. Sulfasalazine remains a recognized DMARD for RA in international treatment guidelines today. Since mesalazine is a direct metabolite of sulfasalazine, and shares the NF-κB / COX-LOX anti-inflammatory axis relevant to synovial inflammation, the TxGNN model’s prediction of RA efficacy is pharmacologically coherent.

A critical nuance must be acknowledged: multiple clinical comparative studies (PMID 2860942, 1985; PMID 2877851, 1986; PMID 8535642, 1995) systematically investigated whether 5-ASA or sulfapyridine carries the antirheumatic activity in sulfasalazine, and the prevailing consensus favors sulfapyridine as the dominant DMARD-active component. In these trials, 5-ASA monotherapy demonstrated only a weak first-line anti-inflammatory effect in RA, significantly less than intact sulfasalazine. That said, in vitro evidence published in 2000 (PMID 10743803) shows that 5-ASA does modulate mRNA expression of IL-1β, TNF-α, and matrix metalloproteinases (MMP-1, MMP-3) in rheumatoid synovial fibroblasts — suggesting a direct mechanistic role at the tissue level that may not have been fully captured by systemic efficacy trials using standard oral dosing.

Clinical Trial Evidence

Trial Number	Phase	Status	Enrollment	Key Findings
NCT02930343	Phase 3	Terminated	136	Sulfasalazine vs. leflunomide-based combination DMARD therapy in RA patients failing MTX monotherapy; provides the most directly relevant class-level evidence, though study was terminated before completing primary endpoint
NCT00637780	Phase 4	Terminated	2	Steady-state pharmacokinetics of sulfasalazine delayed-release tablets in pediatric Juvenile Idiopathic Arthritis; very limited scientific value due to near-zero enrollment
NCT05580861	Phase 1/2	Recruiting	64	Sulfasalazine combined with standard AML induction therapy in patients ≥60; the mechanism here is xCT inhibition by intact sulfasalazine — not applicable to mesalazine (5-ASA does not inhibit xCT)
NCT06201793	Phase 2	Completed	46	Minocycline as adjunct to mesalamine in ulcerative colitis; study subject is minocycline, mesalamine is background therapy only — not applicable to RA repurposing
NCT03591770	Phase 4	Terminated	15	Shingrix vaccine immunogenicity and safety in UC patients on tofacitinib; not relevant to RA repurposing, terminated early
NCT00514982	Phase 2	Withdrawn	0	IBD therapy in Hermansky-Pudlak syndrome-associated colitis; withdrawn before any enrollment, no usable data

Note: No clinical trials directly studying Mesalazine (5-ASA) monotherapy in rheumatoid arthritis were identified. All arthritis-relevant trials test the parent compound sulfasalazine.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
7588084	1995	Systematic Review	Drugs	Comprehensive pharmacology and efficacy review of sulfasalazine as an established DMARD in RA; notes ongoing uncertainty regarding whether SP or 5-ASA carries the antirheumatic activity
2899645	1988	Prospective Clinical Study	J Rheumatol	12-week sulfasalazine treatment normalizes elevated activated lymphocytes and aberrant mitogen response in RA patients; in vitro lymphocyte inhibition study clarifies immunomodulatory mechanism
2860942	1985	Clinical Comparative Study	BMJ (Clin Res Ed)	Landmark study: sulphapyridine showed pronounced second-line DMARD effect in RA over 24 weeks; 5-aminosalicylic acid showed only a weak first-line effect — primary evidence questioning mesalazine as the active RA moiety
2877851	1986	Clinical Comparative Study	Drugs	30 active RA patients randomized to 5-ASA or sulphapyridine monotherapy for 6 months; sulphapyridine group showed significant improvement across clinical and biochemical parameters; 5-ASA group did not improve despite adequate plasma concentrations
8535642	1995	Review	Br J Rheumatol	Synthesizes evidence that sulphapyridine (not 5-ASA) is the primary antirheumatic moiety; notes ~30% of intact sulfasalazine absorbed unaltered may independently contribute
10743803	2000	In Vitro Mechanistic Study	J Rheumatol	5-ASA modulates steady-state mRNA of IL-1β, TNF-α, MMP-1, MMP-3, MMP-2 and TIMP in rheumatoid synovial fibroblasts — provides direct molecular evidence that mesalazine acts on RA-relevant tissue targets
17708602	2007	Review	World J Gastroenterol	Historical account documenting that sulfasalazine was originally designed to treat rheumatoid arthritis in the 1940s; pivotal context for understanding the RA–mesalazine connection
12235076	2002	Pharmacovigilance Study	Gut	Analysis of serious adverse reaction reports for sulfasalazine and mesalazine submitted to the UK Committee on Safety of Medicines; characterizes the comparative safety profiles of both compounds
41443863	2025	Case Report	Intern Med (Tokyo)	Important safety signal: mesalazine-induced colitis in a 76-year-old RA patient without prior IBD history who received sulfasalazine then mesalazine for RA; drug-induced lymphocyte stimulation test confirmed mesalazine hypersensitivity — paradoxical colitis risk in RA setting
16885699	2006	Review	J Clin Gastroenterol	Reviews mesalazine metabolism and pharmacokinetics; confirms sulfasalazine was initially developed for RA and that several 5-ASA formulations were created to avoid the sulfapyridine-related side effects of sulfasalazine

Safety Considerations

Drug Interactions (291 total interactions identified via DDInter):

Major interactions requiring close monitoring:

Cidofovir (Major): Risk of additive nephrotoxicity; avoid concurrent use
Human Botulinum Neurotoxin A/B Immune Globulin (Major): Requires careful monitoring if co-administered

Clinically significant moderate interactions:

NSAIDs (Ketorolac, Ibuprofen, Celecoxib, Bromfenac): Combination may increase gastrointestinal and renal adverse effects — particularly relevant in RA, where NSAIDs are frequently co-prescribed
Azathioprine: Commonly co-used in IBD and RA; mesalazine may inhibit thiopurine methyltransferase (TPMT), increasing azathioprine toxicity risk
Nephrotoxic antibiotics (Amikacin, Amikacin liposome, Capreomycin, Bacitracin, Amphotericin B and its formulations): Additive renal toxicity risk
Antidiabetics (Acetohexamide, Chlorpropamide): Moderate interaction, monitor glycemic control
Anticoagulants (Anisindione): Potential for altered anticoagulation effect
Cisplatin (Moderate): Additive nephrotoxicity concern
Acyclovir (Moderate): Renal clearance interaction

Please refer to the complete package insert for full warnings and contraindications, as detailed labeling data was not available for this review.

Conclusion and Next Steps

Decision: Proceed with Guardrails

Rationale: Sulfasalazine — the prodrug from which mesalazine is derived — is an established RA DMARD with decades of clinical use, providing strong historical and mechanistic grounding for this repurposing hypothesis. In vitro evidence confirms that mesalazine (5-ASA) directly modulates RA-relevant synovial tissue targets (cytokines, MMPs) via NF-κB and COX/LOX pathways. However, the critical limitation is that clinical comparative trials have consistently shown sulfapyridine — not 5-ASA — to be the dominant antirheumatic moiety in sulfasalazine, meaning mesalazine monotherapy in RA remains an untested hypothesis requiring purpose-designed clinical evidence.

To proceed, the following is needed:

Obtain full mechanism of action (MOA) documentation from DrugBank API (data gap DG002)
Obtain India/regional regulatory labeling (package insert) for complete warnings and contraindications (data gap DG001)
Design a dedicated Phase 2 pilot trial of oral mesalazine monotherapy in early or mild-to-moderate RA, with PK/PD endpoints establishing achievable systemic 5-ASA concentrations
Conduct pharmacokinetic modeling to determine whether oral mesalazine can achieve synovial tissue concentrations sufficient for the anti-inflammatory effects demonstrated in vitro
Assess TPMT genotype and azathioprine co-medication status in any RA patient population enrolled, given the DDI signal
Monitor for the paradoxical risk of mesalazine-induced colitis, as documented in the 2025 case report (PMID 41443863) in RA patients
Explore whether a systemic (non-enteric-coated) formulation would improve bioavailability and mechanistic reach beyond the colonic mucosa
Disclaimer

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