Pharmacogenetic of antirheumatic treatments: clinical implications

The Genetic Contribution to Drug Response in Spondyloarthritis: A Systematic Literature Review

Objective: Spondyloarthritis (SpA) are a group of diseases with a high heritability, whose pathogenesis is strongly determined by an interplay between genetic and environmental factor. Therefore, the aim of our study was to determine whether genetic variants could also influence response to therapy in SpA. Methods: A systematic literature review (SLR) was conducted in PubMed and Web of Science core collection, without publication-year restrictions (Last search 8th April 2021). The search strategy was formulated according to the PEO format (Population, Exposure, Outcome) for observational studies. The population was adult (≥18 years) patients with SpA. The exposure was inheritable genetic variations of any gene involved in the disease pathogenesis/drug metabolism. The outcome was response to the drug, both as dichotomous (response yes/no) and as continuous outcomes. Exclusion criteria were: (1) languages other than English, (2) case series, case reports, editorials, and reviews, (3) studies reporting genetic contribution to drug response only limited to extra-musculoskeletal features of SpA, (4) epigenetic modifications. Quality of the included study was independently assessed by two authors. Results: After deduplication, 393 references were screened by two authors, which led to the final inclusion of 26 articles, pertinent with the research question, that were considered for qualitative synthesis. Among these, 10 cohort, one cross-sectional, and five case-control studies were considered of at least good quality according to Newcastle-Ottawa Scale (NOS). In studies about TNF-blockers therapy: (1) polymorphisms of the TNF receptor superfamily 1A/1B (TNFRSF1A/1B) genes were most frequently able to predict response, (2) -238 and -308 polymorphisms of TNFα gene were studied with conflicting results, (3) TNFα polymorphism rs1799724, rs1799964, -857, -1,013, +489 predicted drug response in non-adjusted analysis, (4) PDE3A rs3794271 had a linear relationship with DAS28 reduction after anti-TNFα therapy. DHFR polymorphism +35,289 was able to predict response to methotrexate. Conclusions: Our SLR highlighted the existence of a genetic component in determining drug response. However, further studies are warranted to better define quantify it.

Association of interleukin 1 receptor antagonist intron 2 variable number of tandem repeats polymorphism with vitiligo susceptibility in Gujarat population

Background

Vitiligo is a multifactorial, polygenic, autoimmune skin disorder caused by selective destruction of melanocytes. Interleukin 1 receptor antagonist intron 2 polymorphism was found to be associated with various autoimmune disorders.

Aims

We aimed to investigate the association of interleukin 1 receptor antagonist intron 2 variable number of tandem repeats polymorphism (rs2234663) with vitiligo to assess interleukin 1 receptor antagonist transcript levels and to perform possible genotype-phenotype correlation.

Methods

Three hundred and seven vitiligo patients and 316 controls were enrolled in the study, genotyping of interleukin 1 receptor antagonist rs2234663 was performed by polymerase chain reaction, and relative gene expression of interleukin 1 receptor antagonist was carried out in peripheral blood mononuclear cells from patients (n = 36) and controls (n = 36) by real-time-PCR.

Results

A significant difference was observed in the frequency of interleukin 1 receptor antagonist *A (1/2) genotype among patients with active and stable vitiligo (P = 0.0172). Interleukin 1 receptor antagonist*A (2/2) genotype and allele frequencies were significantly different between SV patients and controls (P = 0.0246 and P = 0.0046, respectively). Significant difference was also observed for interleukin 1 receptor antagonist*A2 (allele) in active and stable vitiligo patients (P = 0.0060). However, other comparisons did not show any significant difference in genotype and allele frequencies. Moreover, interleukin 1 receptor antagonist*A (3/2) genotype was observed only in patients whereas interleukin 1 receptor antagonist*A (5/2) was observed only in controls. Gene expression analysis showed no significant difference in interleukin 1 receptor antagonist transcript levels in patients compared to controls (P = 0.5962). Interestingly, genotype-phenotype correlation analysis revealed that individuals with IL1RN*A (2/2) exhibited higher interleukin 1 receptor antagonist expression compared to other major genotypes interleukin 1 receptor antagonist*A (1/2) (P = 0.01) and interleukin 1 receptor antagonist*A (1/1) (P = 0.03).

Limitations

More case-control studies on interleukin 1 receptor antagonist rs2234663 polymorphism and gene expression from different ethnic populations are required to explore the impact of interleukin 1 receptor antagonist in vitiligo susceptibility.

Conclusion

Interleukin 1 receptor antagonist*A2 might be a risk factor for progressive vitiligo.