Pharmacogenetics of Ranibizumab in patients with age-related macular degeneration
Introduction: The age-related macular degeneration (AMD) has become the leading cause of visual impairment in people over 65 years in Industrialized Countries. Clinically, the disease is characterized by the appearance of drusen - accumulation of hyaline material – and it may evolve in the hemorrhagic-exudative (wet) or atrophic (dry) types. The wet form is characterized by the proliferation of new blood vessels in the subretinal membrane; angiogenesis is promoted by numerous pro-angiogenic regulators among which the vascular endothelial growth factor (VEGF-A) plays a key role.
Aims of the study: The purpose of this study is to assess, for the first time, the association among some VEGF-A single nucleotide polymorphisms (SNPs) in patients and the efficacy of the anti-VEGF-A monoclonal antibody ranibizumab.
Patients and methods: Currently, forty-four patients were enrolled into the study. The patients have been diagnosed wet AMD, using fluorescein and indocyanine angiography and OCT (optical coherence tomography). The functional response after a complete treatment with ranibizumab, which includes the measurement of visual acuity (expressed by number of letters in tables ETDRS) and retinal sensitivity using the microperimetry (MP), was evaluated. DNaA was extracted by QIAamp DNA blood mini kit (Qiagen). Five SNPs on VEGFA gene were analyzed: 2578A/C, -1498C/T, -1154A/G, -634C/G, +936C/T; the allelic discrimination was performed in Real-Time PCR Taqman platform. The results were analyzed using the software GraphPad Prism (version 5.0, GraphPad Prism Software Inc., San Diego, CA, USA). The Hardy-Weinberg equilibrium and linkage disequilibrium tests between loci was calculated using Arlequin version 3.1 and PHASE. Results: The five SNPs of VEGF-A were in Hardy-Weinberg equilibrium. The SNPs of the promoter region were in linkage disequilibrium, whereas the +936C/T segregated independently of the others. In order to demonstrate the possible association between VEGF-A genotypes and clinical response, the data were analyzed with the chi-square test. Among the patients who had an overall functional response to therapy after ranibizumab, 68% carried the -2578AC/CC genotype, whereas among non-responders the genotype frequency was only 23% (P=0.0366). Similar results were observed in patients with the genotypes -1498CT/TT and -1154AG/AA.
Conclusion: In conclusion, after 6 months of therapy with Ranibizumab, an increased frequency of genotypes -2578AC/CC, -1498CT/TT and -1154AG/AA occurred in patients who had retinal functional response. A further enrollment of patients will be necessary to confirm these preliminary findings.
