[Anti-VEGF therapy for neovascular age-related macular degeneration: causes of incomplete response]

[New findings on pathogenetic mechanisms in the development of age-related macular degeneration]

Age-related macular degeneration (AMD) is a complex multifactorial disease that occurs due to disfunction and degeneration of retinal pigment epithelium (RPE) and choriocapillaris, as well as death of photoreceptors. The exact pathogenetic mechanism remains uncertain. The aging process is the main and the clearest risk factor of AMD. In the development of this condition, a special role belongs to the secretory phenotype of aging spreading from one cell to another and mediated by the secretion and release of growth factors, cytokines, chemokines, proteases, and other molecules. Another major contributor is oxidative stress caused by violations in the recirculation of vitamin A in the vision cycle and accompanied by accumulation of lipofuscin, which mediates the formation of iron-based oxidants that are toxic for mitochondria. Furthermore, prolonged oxidative stress and constant light exposure induce the development of inflammation in the retina. Accumulation of metabolic products and cellular defects with age can induce an inflammatory reaction that amplifies the damage. The inflammatory processes including innate immune response, activation of microglia and parainflammation that occur locally in the vascular membrane, pigment epithelium and neuroretina are very significant contributors to the age-related changes, their progression, and the development of advanced stages of AMD. Various growth factors play a special role in the development of choroidal neovascularization (CNV). Vascular endothelial growth factor A (VEGF-A) has traditionally been considered the main factor of neoangiogenesis and, consequently, the main therapeutic target, but in recent years various studies have determined the role of other factors - VEGF-B, C, D, PGF, Gal-1, angiopoietins. This article describes the main underlying mechanisms in the development of choroidal neovascularization including retinal aging, impaired metabolic activity, mitochondrial dysfunction, inflammatory reactions and genetic variations, as well as the role of various growth factors.

[Current view on the issue of insufficient effectiveness of anti-VEGF therapy for age-related macular degeneration]

Due to the significant medical and social importance of neovascular (wet) age-related macular degeneration (wAMD), increasing the effectiveness of anti-VEGF therapy used to treat this disease is one of the high-priority problems in modern retinology. This article focuses on pathobiological aspects and clinical manifestations of incomplete responses to anti-VEGF therapy of wAMD, considers the proposed ways to improve the terminology and classification of responses to therapy, as well as the assessment of its correctness and effectiveness of the treatment. It also discusses the available ways to optimize anti-VEGF therapy and define the criteria of its termination in cases when the treatment proves to be futile.