Analysis of ocular fluid in patients with ranibizumab-recalcitrant neovascular age-related macular degeneration who have serum anti-ranibizumab antibodies.

Purpose: To evaluate whether anti-drug antibodies (ADAs) are present in the ocular fluid of patients with ranibizumab-recalcitrant neovascular age-related macular degeneration (nAMD).

Methods: Two serum ADA-positive ranibizumab-recalcitrant patients and two serum ADA-negative controls were recruited from patients with nAMD treated with ranibizumab monotherapy. Recalcitrance was defined as persistent fluid after ≥6 monthly ranibizumab injections. Serum and aqueous humor ADAs were detected by enzyme-linked immunosorbent assay and immunoprecipitation, respectively.

Results: Two of 156 ranibizumab-treated patients were ADA-positive. The patients received six and 14 ranibizumab injections, respectively, up to 4 weeks prior to blood collection. The serum ADA concentration was estimated to be approximately 50,000 ng/mL. Neutralizing ADAs were confirmed in both samples. A specific band was detected by immunoprecipitation only in ADA-positive samples, consistent with the results of enzyme-linked immunosorbent assay. Based on an assessment of the degree of sensitivity of commercially available anti-ranibizumab antibodies, it was estimated that the immunoprecipitation method could detect ADA levels >30 ng. Nevertheless, ADAs were not detected in the aqueous humor of either the experimental or control group.

Conclusion: In the aqueous humor, ADAs are either not present or are present at a lower concentration than that which can be detected by immunoprecipitation. This presumably reflects the fact that blood ADA is the product of systemic circulation clearance through anterior elimination of intravitreal ranibizumab. Based on our results, ADAs do not return to the eye in sufficient quantities to interfere with the action of ranibizumab in the vitreous cavity.