Efficacy and safety of abatacept to treat active birdshot uveitis: a prospective open label interventional proof-of-concept trial.

Background/aims: Birdshot uveitis (BU) is a chronic autoimmune posterior uveitis, mostly affecting middle-aged Caucasians. There is a strong association with HLA-A29 and T-cell activation. Safety and efficacy of abatacept, an inhibitor of T-cell costimulation, is tested in active BU.

Methods: Fifteen patients with active BU were treated with monotherapy of weekly subcutaneous injections of abatacept 125 mg/mL. Time-to-treatment failure was evaluated as a primary outcome. The secondary objective was to evaluate the utility of different outcome measures to monitor disease activity. Safety was evaluated by adverse event reporting and serial blood analyses.

Results: At the year-1 endpoint, there was significant improvement in vitreous haze grade (p=0.0014), central choroidal thickness (CCT) (p=0.0011), Fluorescein Angiography (FA) Score (p=0.0014), Indocyanine Green Angiography (ICGA) Score (p<0.001) and total dual FA-ICGA Score (p<0.001). Best corrected visual acuity (BCVA) (p=0.8354) and central retinal thickness (CRT) (p=0.3549) did not change significantly. There were no serious adverse events reported. In total, 4 out of 15 patients left the trial during year 1 of whom 2 experienced treatment failure.

Conclusions: Abatacept is very efficacious to treat both retinal vasculitis and choroiditis in patients with BU and is well tolerated. BCVA and CRT are inadequate to monitor disease activity. On the other hand, CCT is a promising non-invasive tool to detect treatment response in early active BU and dual FA-ICGA Score is very helpful to evaluate retinal vasculitis and choroiditis quantitatively.

Trial Registration Number: NCT03871361.