Pharmacogenetic labyrinth of neovascular age-related macular degeneration therapy: how to escape and move forward?

Genotypes of SNPs of key genes regulate susceptibility and drug sensitivity to neovascular AMD in the human population

OBJECTIVE

To compare the genetic characteristics of the normal control group to those of neovascular age-related macular degeneration (AMD) patients and to detect single-nucleotide polymorphisms (SNPs) related to the pathogenesis of neovascular AMD and the sensitivity to anti-VEGF drug, combercept.

METHOD

This is a prospective case-controlled study. A total of 104 neovascular AMD patients were treated with combercept and 106 normal subjects were served as the control group. SNPs associated with neovascular AMD and disease susceptibility and drug sensitivity were analysed.

RESULTS

Significant differences existed between neovascular AMD patients and normal subjects among genotypes of the SNPs of two genes, ARMS2 (rs10490924 T) and HTRA 1 (rs11200638 A). The T alleles in rs1065489 of CFH and the rs2230205 of C3 significantly promoted neovascular AMD in males while having no significant effect in females. Six SNPs of five genes, including C3 (rs2250656 G), CFB (rs2072633 G), CFH (rs2274700 A, rs3766405 T), KDR (rs6828477 A) and FZD 4 (rs10898563 T), had significant impact in reducing neovascular AMD. Two SNPs of the CFH gene (rs2274700 A and rs3766405 T) and one SNP of the CFB gene, rs2072633 G, were statistically significantly associated with good response to combercept. Conversely, the other two SNPs of the CFH gene, rs1065489 T and rs3753396 G, and the rs7412 T of the APOE gene were associated with a relatively poor patient response to drug action. Two sets of SNPs of CFB have a combined positive effect on disease. The two SNPs of CFH (rs1065489 T and rs3753396 G) and the combination of the two SNPs of CFH and rs7412T of APOE have negative effects on the drug effectiveness.

CONCLUSIONS

These genotype differences facilitate the selection of individualised treatment options towards obtaining the most efficacious clinical treatment. These findings need to be validated by studies with different ethnic populations and/or larger samples.

Diabetic macular oedema: clinical risk factors and emerging genetic influences

Diabetic macular oedema is the major cause of visual impairment in type 1 and type 2 diabetes. As type 2 diabetes becomes more prevalent worldwide, the prevalence of diabetic macular oedema is also expected to rise. Current management of diabetic macular oedema is challenging, expensive and not optimal in a subset of patients. Therefore, it is important to increase our understanding of the risk factors involved and develop preventative strategies. While clinical risk factors for diabetic macular oedema have been identified, few studies have addressed potential genetic risk factors. Epidemiology and family studies suggest genetic influences are of importance. In this review, we summarise known clinical risk factors, as well as discuss the small number of genetic studies that have been performed for diabetic macular oedema.

IL-8 and VEGFR-2 polymorphisms modulate long-term functional response to intravitreal ranibizumab in exudative age-related macular degeneration

AIM

To investigate possible associations between VEGFR-2 and IL-8 gene SNPs and 1-year response to intravitreal ranibizumab for exudative age-related macular degeneration.

MATERIALS & METHODS

Sixty-four eyes underwent a loading phase of three monthly intravitreal injections of ranibizumab 0.5 mg/0.05 ml followed by Pro Re Nata retreatment. VEGFR-2 rs2071559 (-604 A/G) and IL-8 rs4073 (-251 A/T) were analyzed.

RESULTS

Ranibizumab was significantly more effective as measured by visual acuity in patients harboring the IL-8 rs4073 TT genotype (p = 0.045), whereas patients carrying the VEGFR-2 rs2071559 CC genotype revealed better functional response as measured by mean retinal sensitivity (p = 0.034).

CONCLUSION

IL-8 rs4073 and VEGFR-2 rs2071559 genotypes may represent important molecular determinants to modulate final outcomes in neovascular age-related macular degeneration patients.

Complement pathway biomarkers and age-related macular degeneration

In the age-related macular degeneration (AMD) 'inflammation model', local inflammation plus complement activation contributes to the pathogenesis and progression of the disease. Multiple genetic associations have now been established correlating the risk of development or progression of AMD. Stratifying patients by their AMD genetic profile may facilitate future AMD therapeutic trials resulting in meaningful clinical trial end points with smaller sample sizes and study duration.

Aflibercept administration in neovascular age-related macular degeneration refractory to previous anti-vascular endothelial growth factor drugs: a critical review and new possible approaches to move forward

PURPOSE

The recent introduction of anti-VEGF drugs has widely changed the prognosis of exudative age-related macular degeneration (AMD), even if a variable percentage of patients showed an insufficient response. Aflibercept is a new anti-VEGF drug approved by FDA for the treatment of exudative AMD with a wider binding capacity than either bevacizumab or ranibizumab. Therefore, the purposes were as follows: (i) to report anatomical and functional outcomes of switching from bevacizumab/ranibizumab to aflibercept previously described in the scientific literature, (ii) to hypothesize the possible pathophysiological mechanisms of the resistance and tachyphylaxis to anti-VEGF drugs, and (iii) to suggest possible clinical actions to increase the chances of success for such difficult cases.

METHODS

We reviewed the available scientific literature in Medline, Cochrane database, Current Contents, PubMed, and cross-referencing from identified articles, regarding the treatment of exudative AMD patients refractory to bevacizumab and/or ranibizumab and switched to aflibercept monotherapy. We included in this review all the cases in which the diagnosis of refractory or resistant exudative AMD was properly made, and the results of at least one aflibercept injection were described.

FINDINGS

We reported the outcomes of 21 papers for a total of 1066 eyes affected by exudative AMD resistant to previous anti-VEGF drug injections and switched to aflibercept. Enrolled reports were divided into two groups: 5 prospective reports and 16 retrospective reports. All the reported papers conclude their analysis, stating that switching from bevacizumab/ranibizumab to aflibercept injections can improve outcomes successfully in refractory neovascular AMD patients.

IMPLICATIONS

Analysis of the papers reported in this review demonstrates that switching from bevacizumab/ranibizumab to aflibercept injections can improve outcomes successfully in refractory neovascular AMD patients. The mechanism for these effects is not yet completely understood.

Pharmacogenomics of response to anti-VEGF therapy in exudative age-related macular degeneration

PURPOSE

To determine whether there is an association between response to intravitreal anti-vascular endothelial growth factor agents and genotype in patients with neovascular age-related macular degeneration.

METHODS

Analysis of the current literature evaluating pharmacogenetics of treatment response in patients with neovascular age-related macular degeneration.

RESULTS

Studies have demonstrated associations between various genotypes and response to intravitreal anti-vascular endothelial growth factor agents. Lower-risk genotypes of the CFH, ARMS2, HTRA1, and VEGF-A genes may be associated with improved visual outcomes. Additionally, frequency of injections may be associated with certain genotypes.

CONCLUSION

Genetic background may influence an individual's response to treatment of neovascular age-related macular degeneration. Further studies to investigate biologic pathways of neovascular age-related macular degeneration and gene products that are directly involved might lead to better understanding of contribution of various genes to treatment response.