Bevacizumab (Avastin) is used off-label for intravitreal anti-VEGF therapy. Compared to ranibizumab and aflibercept, which molecular property of bevacizumab accounts for its longer intravitreal half-life?
- A It is a full-length IgG1 monoclonal antibody — larger molecule with slower retinal clearance ✓
- B It is a Fab fragment with a smaller molecular weight
- C It binds all VEGF-A isoforms with higher affinity than aflibercept
- D It has a PEGylated structure that prolongs vitreous half-life
Correct answer: A. It is a full-length IgG1 monoclonal antibody — larger molecule with slower retinal clearance
Explanation
Bevacizumab is a full-length humanised IgG1 monoclonal antibody (MW ~148 kDa), whereas ranibizumab is a Fab fragment (MW ~48 kDa). The larger size of bevacizumab slows its clearance from the vitreous, giving it a longer intravitreal half-life (~10 days) compared to ranibizumab (~9 days, though pharmacokinetics are complex). Aflibercept is a fusion protein (VEGF trap) with higher VEGF affinity. PEGylation applies to brolucizumab and not bevacizumab.
Reference: Khurana Comprehensive Ophthalmology, 7th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.