title: Different Effects of Ranibizumab and Bevacizumab on Platelet Activation Profile.
abstract: OBJECTIVE
  The aim of the study was to evaluate the potential influence of ranibizumab and bevacizumab on platelet activation and aggregation, which are critical processes in the pathogenesis of arterial thromboembolic events (ATEs).
  
  
  METHODS
  For the assessment of platelet function, flow cytometry and aggregometry were employed. Platelets were isolated from healthy volunteers and exposed to ranibizumab (1 mg/ml and 150 ng/ml) and bevacizumab (2.5 mg/ml and 3 μg/ml) or their solvents for 10 and 30 min prior to the addition of TRAP (25 μM), PAR-4-AP (25 μM) or thrombin (0.02 U/ml). The surface expression of activated GP IIb/IIIa, P-selectin (CD62P) and platelet-bound stromal cell-derived factor-1 (SDF-1) was measured on resting (nonactivated) and activated platelets by flow cytometry. The platelet aggregation capacity was examined using light transmission aggregometry.
  
  
  RESULTS
  The expression of surface activation markers did not differ significantly between nonstimulated and TRAP-, PAR-4-AP- or thrombin-activated platelets after incubating with ranibizumab. However, GP IIb/IIIa, CD62P and SDF-1 were significantly downregulated in PAR-4-AP- and thrombin-activated platelets after exposure to bevacizumab 2.5 mg/ml. In addition, ranibizumab- and bevacizumab-FITC were significantly increased in all activated platelets. No significant differences were observed in the aggregation of activated platelets after incubation with ranibizumab or bevacizumab.
  
  
  CONCLUSIONS
  All ranibizumab concentrations as well as the bevacizumab concentration of 3 μg/ml had no influence on platelet activation and aggregation. Therefore, this in vitro study did not show any relationship between the exposition of activated platelets to ranibizumab or bevacizumab and the development of ATEs. However, the highest level of bevacizumab interfered with platelet activation, leading to downregulation of platelet activation markers. This observation might explain why the systemic treatment with high-dose bevacizumab could be associated with an increased risk of bleeding. Regarding the use of lower intravitreal dosages, further research should focus on the complex interactions between platelets and other cells, such as endothelial cells, which might stronger relate to a potentially increased risk of ATEs and depend on systemic vascular endothelial growth factor levels. Facing the different activation profiles, the diverse effects of the drugs on the cellular level have to be critically scrutinized for their clinical relevance.
authors: Center for Ophthalmology, Eberhard Karls University, Tx00FC;bingen, Germany.
authors: Bianka
authors: B
authors: Sobolewska
authors: Cornelia
authors: C
authors: Grimmel
authors: Aikaterini
authors: A
authors: Gatsiou
authors: Kateryna
authors: K
authors: Sopova
authors: Judith
authors: J
authors: Klein
authors: Tilo
authors: T
authors: Biedermann
authors: Konstantinos
authors: K
authors: Stellos
authors: Focke
authors: F
authors: Ziemssen
mesh_terms: D020533:Angiogenesis Inhibitors / Q000494:pharmacology*; D000068258:Bevacizumab / Q000494:pharmacology*; D001792:Blood Platelets / Q000187:drug effects* / Q000378:metabolism; D054377:Chemokine CXCL12 / Q000378:metabolism; D005434:Flow Cytometry; D006801:Humans; D019007:P-Selectin / Q000378:metabolism; D010446:Peptide Fragments / Q000494:pharmacology; D015539:Platelet Activation / Q000502:physiology*; D010974:Platelet Aggregation / Q000502:physiology; D019039:Platelet Glycoprotein GPIIb-IIIa Complex / Q000378:metabolism; D000069579:Ranibizumab / Q000494:pharmacology*; D018179:Receptors, Thrombin / Q000008:administration & dosage; D013917:Thrombin / Q000494:pharmacology; D042461:Vascular Endothelial Growth Factor A / Q000037:antagonists & inhibitors
chemical_list: D020533:Angiogenesis Inhibitors; C515255:CXCL12 protein, human; D054377:Chemokine CXCL12; D019007:P-Selectin; D010446:Peptide Fragments; D019039:Platelet Glycoprotein GPIIb-IIIa Complex; D018179:Receptors, Thrombin; C546937:SELP protein, human; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; C082835:thrombin receptor peptide (42-47); D000068258:Bevacizumab; D013917:Thrombin; C112908:protease-activated receptor 4; D000069579:Ranibizumab