Vitreous levels of bevacizumab and vascular endothelial growth factor-A in patients with choroidal neovascularization.
OBJECTIVE
To investigate the vitreous levels of bevacizumab and vascular endothelial growth factor-A (VEGF-A) after intravitreal injection of the drug in patients with choroidal neovascularization (CNV).


METHODS
Interventional case series.


METHODS
Eleven eyes of 11 patients with submacular hemorrhage and CNV due to age-related macular degeneration (n = 10) or angioid streaks (n = 1).


METHODS
All patients were treatment naïve except for a single dose of intravitreal injection of bevacizumab (1.25 mg/50 muL dose) and subsequent vitrectomy after various intervals (1-101 days) because of active and progressive lesion. Intravitreal free bevacizumab and VEGF-A levels were measured using enzyme-linked immunosorbent assay and microsphere-based immunoassay, respectively. Vitreous VEGF-A isoforms were analyzed by sodium dodecyl sulfate polyacrylamide gel electrophoresis and Western blotting.


METHODS
Intravitreal bevacizumab and VEGF-A levels were measured and pharmacokinetic parameters were calculated.


RESULTS
Pharmacokinetics of intravitreal bevacizumab followed a 2-compartment model with initial and terminal half-lives of 0.5 and 6.7 days, respectively. Bevacizumab could be detected in all cases, ranging from 2.63 ng/ml to 165 microg/ml. The peak concentration was observed on the second day after intravitreal bevacizumab injection. Vitreous free VEGF-A levels ranged from 0.2 to 33.9 pg/ml and showed a negative correlation with the bevacizumab concentration (P<0.001; r = -0.955) and a positive correlation with time (P<0.001; r = 0.964). However, the percentage expression of VEGF-A(165) exhibited a positive correlation with the bevacizumab concentration (P = 0.032, r = 0.645) and a negative correlation with time (P = 0.007, r = -0.755). A time-dependent increase was found for the percentage expression of VEGF-A(189) (P = 0.023, r = 0.673). Neither bevacizumab- nor time-related alterations were found for VEGF-A(121).


CONCLUSIONS
Based on pharmacokinetics, the interval of 6-7 weeks would be appropriate for efficacy, although clinical trials should guide dosing recommendations. Vitreous levels of free VEGF-A showed a negative correlation with the bevacizumab concentration, which confirmed the in vivo binding affinity of bevacizumab to VEGF-A. The analysis of the VEGF-A isoforms suggests differences of interaction between bevacizumab and individual VEGF-A isoforms.
Zhu
Qi
Q
Centre for Ophthalmology, Eberhard-Karls University, University Eye Hospital, Tübingen, Germany.
Ziemssen
Focke
F
Henke-Fahle
Sigrid
S
Tatar
Olcay
O
Szurman
Peter
P
Aisenbrey
Sabine
S
Schneiderhan-Marra
Nicole
N
Xu
Xun
X
Grisanti
Salvatore
S
D000368:Aged; D000369:Aged, 80 and over; D020533:Angiogenesis Inhibitors / Q000493:pharmacokinetics*; D000793:Angioid Streaks / Q000150:complications / Q000378:metabolism; D000911:Antibodies, Monoclonal / Q000493:pharmacokinetics*; D061067:Antibodies, Monoclonal, Humanized; D000068258:Bevacizumab; D015153:Blotting, Western; D020256:Choroidal Neovascularization / Q000188:drug therapy / Q000209:etiology / Q000378:metabolism*; D004591:Electrophoresis, Polyacrylamide Gel; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D006207:Half-Life; D006801:Humans; D007267:Injections; D008268:Macular Degeneration / Q000150:complications / Q000378:metabolism; D008297:Male; D008875:Middle Aged; D012166:Retinal Hemorrhage / Q000209:etiology / Q000378:metabolism; D042461:Vascular Endothelial Growth Factor A / Q000493:pharmacokinetics*; D014821:Vitrectomy; D014822:Vitreous Body / Q000378:metabolism*
D020533:Angiogenesis Inhibitors; D000911:Antibodies, Monoclonal; D061067:Antibodies, Monoclonal, Humanized; C467484:VEGFA protein, human; D042461:Vascular Endothelial Growth Factor A; D000068258:Bevacizumab