Shruti Senthilkumar
Cystoid macular oedema (CMO) is one of the leading causes of visual loss in non-infectious uveitis (NIU) and frequently resists conventional treatment, including corticosteroids, disease-modifying antirheumatic drugs (DMARDs), and tumour necrosis factor-alpha (TNF-α) inhibitors. Central to its pathophysiology is cytokine-driven disruption of the blood–retinal barrier (BRB). Interleukin-6 (IL-6) is a key mediator. Via JAK–STAT3 signalling, it upregulates VEGF-A in Müller glial cells and retinal pigment epithelium, driving transcellular fluid leakage. It concurrently destabilises endothelial tight junctions through downregulation of occludin and claudin-5, compounding paracellular permeability (1,2,11).
This dual mechanism partly accounts for the inadequacy of anti-TNF-α therapy in IL-6-driven disease. Tocilizumab (TCZ) is a recombinant humanised monoclonal antibody that blocks membrane-bound and soluble IL-6 receptor (IL-6R), neutralising classical and trans-signalling pathways. This breadth of mechanistic effect underpins the rationale for its use in refractory uveitic CMO.
Observational clinical evidence shows promise for its use. Adán et al. reported a reduction in central foveal thickness (CFT) from 602 to 294 µm alongside meaningful BCVA gains with IV TCZ (8 mg/kg every four weeks) over six months (3), and Calvo-Río et al. found complete CMO resolution in 56% of 25 patients at one year, with a mean BCVA improvement of 0.15 logMAR (4).
The most informative comparative data come from Leclercq et al., whose 204-patient French Uveitis Network study demonstrated a twofold higher rate of complete CMO resolution with TCZ over anti-TNF-α agents in biologic-experienced patients (OR 2.0; 95% CI 1.3–3.0) (5). A 2025 meta-analysis pooling 13 studies (n = 374) reported 93.2% CMO resolution and a mean CFT reduction of 143.6 µm, with a 13.1% adverse event rate suggesting reasonable tolerability (7). Response appears most reliable in Behçet’s disease and JIA-associated uveitis, where IL-6 dysregulation is an established pathogenic driver. In idiopathic, HLA-B27-associated, and sarcoid subtypes, the evidence is thinner and largely anecdotal (6,14). This variation in response by aetiology has direct implications for patient selection that pooled analyses tend to obscure.
Route of administration is a practically important consideration that the literature has not fully resolved. The bulk of published experience — and the most striking outcomes — derive from intravenous TCZ at 8 mg/kg every four weeks, a regimen that delivers higher and more reproducible peak serum concentrations than subcutaneous (SC) dosing. Calvo-Río et al. observed that patients relapsing on SC TCZ could often achieve control after switching to the intravenous formulation, pointing to a meaningful dose-response relationship (12).
For patients in whom systemic immunosuppression is not feasible, intravitreal TCZ offers an alternative route. Early data show anatomical improvement with acceptable local tolerability, though the evidence remains at case-series level (13). Against this backdrop, the APTITUDE phase II trial — the only randomised evidence available — achieved a 33% response rate at 12 weeks in a paediatric JIA-associated uveitis cohort treated with SC TCZ (8). This fell short of its efficacy threshold, but the paediatric population, subcutaneous route, and short follow-up all limit direct extrapolation to adult intravenous practice.
The safety profile of TCZ deserves particular attention in patients who are already immunosuppressed. IL-6R blockade carries recognised class risks – neutropenia, thrombocytopenia, hepatic transaminase elevation, hyperlipidaemia, C-reactive protein suppression, and blunting of the febrile response.
In a patient on concurrent corticosteroids and DMARDs, this can render serious infections clinically silent. Gastrointestinal perforation, though uncommon, is a further recognised risk when TCZ is co-prescribed with NSAIDs or corticosteroids. Haematological, hepatic, and lipid monitoring at baseline, four to eight weeks after starting treatment, and three-monthly thereafter is recommended in line with EULAR biological DMARD guidance (15).
Several important limitations temper enthusiasm for the available evidence. The observational nature of most data (Levels III–IV) introduces inherent selection bias, and the high CMO resolution rates – notably the 93.2% figure from the meta-analysis – almost certainly reflect survival-selection: patients enrolled in case series tend to be those who tolerated and persisted with therapy.
Functional outcomes beyond mean BCVA change, including contrast sensitivity and patient-reported measures, are largely absent from the literature, leaving the real-world visual benefit incompletely characterised. Relapse on withdrawal is well documented, raising unresolved questions about treatment duration and discontinuation strategy (9,10). TCZ is not formally licensed for uveitic CMO in most jurisdictions and should be regarded as off-label therapy.
Adequately powered randomised trials are needed, not only to establish efficacy more robustly but to position TCZ relative to the emerging agents now entering this space. These include: IL-17 inhibitors such as secukinumab, which are particularly relevant in HLA-B27-associated disease; IL-23 inhibitors such as risankizumab, targeting the Th17 axis; and JAK–STAT inhibitors such as upadacitinib for broader cytokine suppression (16). In the meantime, TCZ is best reserved for patients in whom corticosteroids, conventional DMARDs, and at least one anti-TNF-α agent have failed, with careful safety monitoring throughout.
References
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