Aflibercept is a 115 kDa fusion protein. It consists of an IgG backbone fused to extracellular VEGF receptor sequences of the human VEGFR1 and VEGFR2. As a soluble decoy receptor, it binds VEGF-A with a greater affinity than its natural receptors. In an experimental model, aflibercept’s equilibrium disassociation constant (Kd, inversely related to binding affinity) for VEGF-A165 was 0.49 pM, compared with 9.33 pM and 88.8 pM for experimental native VEGFR1 and VEGFR2, respectively. Aflibercept’s high affinity for VEGF prevents the subsequent binding and activation of native VEGF receptors. Reduced VEGF activity leads to decreased angiogenesis and vascular permeability. Inhibition of PIGF and VEGF-B may also aid the treatment of angiogenic conditions. PIGF has been associated with angiogenesis and can be elevated in multiple conditions, such as wet AMD. VEGF-B overexpression has been connected with the breakdown of the blood-retinal barrier and retinal angiogenesis. Thus, inhibition of VEGF-A, VEGF-B, and PIGF may all contribute to the efficacy of aflibercept. Aflibercept has a unique binding action and binds to both sides of the VEGF dimer, forming an inert 1:1 complex called a VEGF trap. Additionally, aflibercept is the only drug in its class that binds to PIGF-2.
