Chloroquine

證據等級: L5

預測適應症: 10 個

Chloroquine: From Malaria to RF-Positive Polyarticular Juvenile Idiopathic Arthritis

One-Sentence Summary

Chloroquine is a well-established antimalarial agent with secondary immunomodulatory properties, historically used for malaria, rheumatoid arthritis, and systemic lupus erythematosus. The TxGNN model’s highest-ranked prediction is its potential efficacy in rheumatoid factor-positive polyarticular juvenile idiopathic arthritis (RF+ polyJIA), with no registered clinical trials and 2 publications providing indirect supporting evidence, primarily through mechanistic analogy with its sister drug hydroxychloroquine. Across all 10 predicted indications in this report, osteoarthritis (rank 5) emerges as the most clinically actionable finding, backed by a completed Phase 4 direct Chloroquine trial and a systematic review.

Quick Overview

Item	Content
Original Indication	Malaria; rheumatoid arthritis; systemic lupus erythematosus (not currently registered in South Africa)
Predicted New Indication (Rank 1)	RF-Positive Polyarticular Juvenile Idiopathic Arthritis
TxGNN Prediction Score	99.41%
Evidence Level	L4 — preclinical / mechanistic studies only
South Africa Market Status	Not marketed
Number of SAHPRA Registrations	0
Recommended Decision	Hold

Why is This Prediction Reasonable?

Currently, detailed mechanism of action data is not available from the structured evidence pack. Based on established pharmacological knowledge, Chloroquine is a 4-aminoquinoline that alkalinises lysosomal pH, blocking antigen processing and MHC class II-mediated antigen presentation to autoreactive T cells. It additionally suppresses innate immune signalling by antagonising Toll-like receptors TLR7 and TLR9 in B cells and plasmacytoid dendritic cells, reducing downstream production of the pro-inflammatory cytokines TNF-α, IL-6, and IL-1β. It also inhibits phospholipase A2 and the NLRP3 inflammasome, broadening its anti-inflammatory reach.

RF-positive polyarticular JIA shares important pathobiological features with adult seropositive rheumatoid arthritis, including B-cell activation, rheumatoid factor production, and immune complex-mediated joint inflammation. These mechanisms are directly targeted by Chloroquine’s immunomodulatory profile: TLR7/9 antagonism interrupts B-cell activation driving RF production, while lysosomal inhibition reduces antigen presentation that sustains autoreactive T-cell responses. The immune complex deposition characteristic of the RF+ subtype further aligns with the drug’s mechanism of action.

Chloroquine’s sister compound hydroxychloroquine (HCQ) has been used safely in children with chronic inflammatory diseases including JIA over a 12-year observational period (PMID 33548956), and a 1996 case series documented that addition of HCQ arrested methotrexate-induced accelerated nodulosis specifically in two RF+ polyarticular JRA patients (PMID 8627446). While this constitutes indirect class evidence rather than Chloroquine-specific data, the mechanistic overlap is sufficient to justify further investigation. Direct Chloroquine clinical data in RF+ polyJIA remains entirely absent, limiting the evidence base to Level 4.

Clinical Trial Evidence

Currently no related clinical trials registered for Chloroquine in rheumatoid factor-positive polyarticular juvenile idiopathic arthritis.

Literature Evidence

PMID	Year	Type	Journal	Key Findings
24334641	2014	Prospective Cohort	The Journal of Rheumatology	Long-term real-world leflunomide experience in JIA (n not specified); provides treatment landscape context for refractory polyarticular JIA subtypes
8627446	1996	Case Series	The Journal of Pediatrics	Two RF+ polyarticular-onset JRA patients developed accelerated nodulosis on methotrexate; nodules arrested by addition of hydroxychloroquine in one patient, suggesting antimalarial class activity specifically in this subtype

South Africa Market Information

Chloroquine is not registered with SAHPRA and is not commercially marketed in South Africa. No registration records were identified. Prescribers wishing to access this drug would require Section 21 (unregistered medicine) authorisation from SAHPRA prior to use.

Contextually relevant: A case report (PMID 32386648) describes a 48-year-old South African woman with seropositive rheumatoid arthritis treated with Chloroquine 150 mg four times per week combined with methotrexate 30 mg weekly at a South African centre, with well-controlled symptoms over several years. This confirms the drug has been clinically used in South Africa despite its unregistered status. Hydroxychloroquine — the closely related sister compound — may have separate registration status and could represent a more accessible alternative with a better-characterised ophthalmological safety profile.

Safety Considerations

Please refer to the SAHPRA-approved Professional Information (PI) for safety information. As Chloroquine is unregistered in South Africa, consult the WHO Model Formulary or the manufacturer’s prescribing information from a jurisdiction where it is registered. Report any adverse drug reactions to SAHPRA at www.sahpra.org.za.

The following clinically important safety signals are identified from literature included in this evidence pack:

Cardiac toxicity (serious): Third-degree atrioventricular block documented in a patient on long-term Chloroquine for juvenile chronic arthritis (PMID 9523387); a separate case reports a rheumatoid nodule in the interventricular septum causing complete heart block in a patient on Chloroquine 200 mg daily (PMID 15222243). Baseline ECG and periodic cardiac monitoring are advised.
QTc prolongation: Chloroquine carries a recognised QT interval prolongation risk (PMID 18078640); avoid concurrent use with other QT-prolonging agents and check for pre-existing conduction abnormalities.
Retinal toxicity: Dose-dependent and cumulative; Chloroquine carries a higher retinal toxicity burden than hydroxychloroquine at standard antirheumatic doses. Annual ophthalmological review including fundoscopy is required.
Toxic myopathy: HCQ-induced toxic myopathy causing diaphragmatic weakness and respiratory failure requiring prolonged mechanical ventilation was reported in a JIA patient (PMID 32787461); Chloroquine shares this risk.

All Predicted Indications: Summary Overview

The TxGNN model identified 10 candidate indications for Chloroquine repurposing. The table below summarises findings across all predictions to support prioritisation decisions:

Rank	Indication	TxGNN Score	Evidence Level	Clinical Trials	Publications	Decision
1	RF+ Polyarticular Juvenile Idiopathic Arthritis	99.41%	L4	0	2	Hold
2	Rheumatoid Nodulosis	99.33%	L4	1 (indirect)	15	Hold
3	Juvenile Chronic Polyarthritis	99.32%	L3	0	20	Research Question
4	Juvenile Idiopathic Arthritis	99.22%	L3	1 (indirect)	20	Research Question
5	Osteoarthritis	98.66%	L2	5 (1 direct CQ trial)	20	Proceed with Guardrails
6	Pseudoachondroplasia	98.33%	L5	0	0	Hold
7	Folliculitis Decalvans	98.21%	L4	0	1	Hold
8	Smouldering Systemic Mastocytosis	98.05%	L5	0	0	Hold
9	Telogen Effluvium	98.04%	L5	0	0	Hold
10	Alopecia Antibody Deficiency	98.02%	L5	0	0	Hold

Highlighted Finding: Osteoarthritis (Rank 5 — Strongest Evidence)

Although ranked 5th by TxGNN prediction score, osteoarthritis represents the most clinically actionable repurposing opportunity with Level 2 evidence, including a completed Phase 4 trial that directly tested Chloroquine in knee osteoarthritis.

Mechanistic rationale: Chloroquine inhibits the NLRP3 inflammasome, NF-κB, and TLR4 signalling pathways, reducing IL-1β, IL-6, and TNF-α-mediated expression of cartilage-degrading enzymes (MMP-3/13, ADAMTS-5). Lysosomal alkalinisation also modulates macrophage polarisation and autophagy — pathways increasingly implicated in age- and trauma-related OA (PMID 41035432, 2026). Inhibition of phospholipase A2 reduces arachidonic acid metabolites that contribute to synovial inflammation. The 2025 experimental study (PMID 40701030) directly demonstrates Chloroquine’s anti-inflammatory cellular mechanisms, supporting biological plausibility.

Clinical Trial Evidence (Osteoarthritis)

Trial Number	Phase	Status	Enrollment	Key Findings
NCT00805519	Phase 4	Completed	230	Direct CQ evidence — Prednisolone + Chloroquine add-on to glucosamine/chondroitin in knee OA; primary efficacy and safety study; highest relevance (Grade A)
NCT01645176	Phase 2	Completed	21	Hydroxychloroquine + Atorvastatin for inflammation and pain in knee OA; indirect class evidence for antimalarial agents
NCT01148043	Phase 3	Completed	200	Pharmacological treatment in OA; HCQ arm evaluated for hand OA — full results required to confirm CQ applicability
NCT06768294	Phase 2	Not Yet Recruiting	32	Baricitinib (JAK inhibitor) in calcium pyrophosphate deposition disease (CPPD); related crystal arthropathy, provides mechanistic context
NCT03975790	N/A	Completed	479	Observational study of tofacitinib + MTX in RA; indirect disease management background only

Literature Evidence (Osteoarthritis — Selected)

PMID	Year	Type	Journal	Key Findings
33882635	2022	Systematic Review & Meta-analysis	Korean J Internal Medicine	Efficacy and safety of HCQ in OA evaluated across RCTs; foundational evidence synthesis for the antimalarial class in OA
35000374	2022	RCT / Clinical Trial	Korean J Internal Medicine	HCQ efficacy in knee OA; direct comparator evidence for the antimalarial class
34215704	2021	RCT (OA-TREAT)	RMD Open	Randomised double-blind multicentre trial of HCQ in inflammatory and erosive hand OA; most rigorous design for class evaluation
26246395	2015	Narrative Review	Inflammopharmacology	Comprehensive pharmacology review of HCQ and CQ in SLE, RA, and OA; explicitly covers both compounds and OA evidence
40701030	2025	Experimental (in vivo)	Cellular Immunology	Chloroquine (not HCQ) ameliorates autoimmune encephalomyelitis by inhibiting T-cell differentiation and pDC accumulation; directly demonstrates CQ immunomodulatory mechanism
41035432	2026	Experimental (in vivo)	Bioactive Materials	Senescent macrophage remodelling in OA synovium alleviates joint damage; mechanistic rationale for CQ lysosomal effects in macrophage-driven OA pathology
25348033	2014	RCT Protocol	Trials	OA-TREAT study protocol — HCQ in inflammatory erosive hand OA; describes outcome measures relevant to CQ trials
18078640	2007	Safety Study	Clin Exp Rheumatology	Chloroquine and QTc interval in rheumatological patients — essential safety reference for OA use
15918998	2005	Review	Current Rheumatology Reports	Calcium-containing crystals and OA; clinical implications for crystal-related OA pathology that CQ lysosomal effects may address
12954956	2003	Review	Postgraduate Medical Journal	Intra-articular therapy in OA; treatment landscape context

Conclusion and Next Steps

Primary Prediction — RF+ Polyarticular JIA

Decision: Hold

Rationale: The TxGNN model’s top-ranked prediction (RF+ polyarticular JIA, score 99.41%) is mechanistically plausible given Chloroquine’s immunomodulatory profile against B-cell-driven autoimmune inflammation. However, no clinical trials and only 2 indirectly relevant publications exist, Chloroquine is unregistered in South Africa, and all key safety and MOA data fields remain outstanding. This combination of evidence gaps and regulatory barriers prevents clinical advancement at this stage.

To proceed, the following is needed:

Full MOA documentation from DrugBank to complete mechanistic analysis
Systematic literature search specifically targeting Chloroquine (not HCQ) in RF+ polyJIA
SAHPRA Section 21 authorisation application if clinical use is being considered
Evaluation of hydroxychloroquine as a more accessible, better-characterised registered alternative
Paediatric dosing data and weight-based safety thresholds for South African children
Ophthalmological and cardiac monitoring protocol development prior to any trial initiation

Most Actionable Finding — Osteoarthritis (Rank 5)

Decision: Proceed with Guardrails

Rationale: A completed Phase 4 trial (NCT00805519, n=230) directly tested Chloroquine add-on therapy in knee OA, and a systematic review with meta-analysis (PMID 33882635) supports the antimalarial class in OA. This evidence base meets Level 2 criteria. In the South African context, where access to biologic agents is often limited by cost (as documented in PMID 32386648), Chloroquine’s low cost and oral administration make it a pragmatically attractive candidate for OA patients who have not responded to standard analgesics.