Poor Response to Bevacizumab Correlates With Higher IL-6 and IL-8 Aqueous Cytokines in AMD

To evaluate the effect of intravitreal bevacizumab on aqueous levels of a panel of 12 inflammatory cytokines in patients with neovascular age-related macular degeneration (nAMD) and correlate response to treatment, as measured by change in the central subfovea thickness (CST), with cytokine levels.

Thirty-three treatment-naïve patients with nAMD received a loading dose of intravitreal bevacizumab consisting of three injections at six weekly intervals. The aqueous samples prior to the first (baseline), second (week 6), and third (week 12) injections were analyzed for cytokine levels. Participants were subgrouped based on changes in CST on spectral-domain optical coherence tomography (SD-OCT) at 12 weeks. Group 1 included patients with a decrease in CST (responders; n = 27). Group 2 included patients who had no decrease in CST (poor responders; n = 6).

Aqueous IL-8 was the only cytokine to demonstrate a significant difference in levels between responders and poor responders, with higher interleukin-8 (IL-8) at week 12 in the poor responder group. Aqueous IL-6 and IL-8 levels showed a positive correlation with CST on SD-OCT (Spearman r = 0.45 and 0.55, respectively). There was a temporal increase overall in cytokine concentration accompanying bevacizumab treatment.

Aqueous IL-6 and IL-8 may be important markers of treatment response or poor response in nAMD. Future therapeutic strategies may include targeted treatment against both vascular endothelial cell growth factor (VEGF) and IL-6 and/or IL-8 in patients who do not respond to anti-VEGF treatment alone.