Use of Pharmacogenetics for Genes Associated with AMD
The authors of the following clinical trial sought to evaluate the pharmacogenetic relationship between genotypes of single nucleotide polymorphisms (SNPs) known to be associated with age-related macular degeneration (AMD) and response to treatment with ranibizumab (Lucentis, Genentech) or bevacizumab (Avastin, Genentech) for neovascular AMD.
They recruited 834 (73% of 1,149 patients participating in the Comparison of AMD Treatments Trials (CATT) through 43 CATT clinical centers and genotyped each patient for SNPs rs1061170 (CFH), rs10490924 (ARMS2), rs11200638 (HTRA1) and rs2230199 (C3) using TaqMan SNP genotyping assays (Applied Biosystems). The authors compared genotypic frequencies with clinical measures of response to therapy at one year, including mean visual acuity (VA), mean change in VA, 15-letter or more increase in VA, retinal thickness, mean change in total foveal thickness, presence of fluid on OCT, presence of leakage on fluorescein angiography (FA), mean change in lesion size and mean number of injections administered. They evaluated differences in response by genotype with tests of linear trend calculated from logistic regression models for categorical outcomes and linear regression models for continuous outcomes. To adjust for multiple comparisons, p≤0.01 was considered statistically significant.
The study authors did not identify any statistically significant differences in response by genotype for any of the clinical measures studied. Specifically, they found no high-risk alleles that predicted final VA or change in VA, the degree of anatomic response (fluid on OCT or FA, retinal thickness, change in total foveal thickness, change in lesion size) or the number of injections. Furthermore, a step-wise analysis failed to show a significant epistatic interaction among the variants analyzed; that is, response did not vary by the number of risk alleles present. The lack of association was similar whether patients were treated with ranibizumab or bevacizumab or whether they received monthly or pro re nata dosing.
In conclusion, although specific alleles for CFH, ARMS2, HTRA1 and C3 may predict the development of AMD, they did not predict response to anti-vascular endothelial growth factor therapy.