Bevacizumab and Aflibercept Activate Platelets via FcγRIIa.

PURPOSE

To confirm the formation of a drug-growth factor complex and investigate the effects of three VEGF inhibitors in the activation of platelets.

METHODS

Growth factors and individual drugs were mixed and incubated. Scattered light intensity was measured by dynamic light scattering (DLS) to monitor the formation of drug-growth factor complex. Blood samples were obtained from 16 subjects (5 AMD patients and 11 healthy volunteers). Platelets obtained from the platelet-rich fraction by centrifugation were washed and resuspended in HEPES/Tyrode buffer. Platelet aggregability was assessed using a light transmission aggregometer in the presence of VEGF inhibitors and growth factors.

RESULTS

In DLS study, a mixture of bevacizumab and VEGF-A showed one peak with a relatively gentle slope, indicating a heterogeneous mixture of multimeric bevacizumab-VEGF-A complexes. In aggregation study, no detectable aggregation was observed in the presence of ranibizumab, while significant aggregation was observed in the presence of VEGF-A and bevacizumab in five cases (one AMD patient and four healthy volunteers), VEGF-B and aflibercept in two cases (two volunteers), and placental growth factor (PlGF) and aflibercept in one case (one volunteer). No aggregation was observed when FcγRIIa antibody was added beforehand.

CONCLUSIONS

A complex composed of bevacizumab or aflibercept, but not ranibizumab, and growth factors activates platelets via FcγRIIa.