Prevalence of the DPYD variant (Y186C) in Brazilian individuals of African ancestry

The Frequency of DPYD c.557A>G in the Dominican Population and Its Association with African Ancestry

Background/Objectives: Genetic polymorphism of the dihydropyrimidine dehydrogenase gene (DPYD) is responsible for the variability found in the metabolism of fluoropyrimidines such as 5-fluorouracil (5-FU), capecitabine, or tegafur. The DPYD genotype is linked to variability in enzyme activity, 5-FU elimination, and toxicity. Approximately 10-40% of patients treated with fluoropyrimidines develop severe toxicity. The interethnic variability of DPYD gene variants in Afro-Latin Americans is poorly studied, thereby establishing a barrier to the implementation of personalized medicine in these populations. Therefore, the present study aims to analyze the frequency of DPYD variants with clinical relevance in the Dominican population and their association with genomic ancestry components. Methods: For this study, 196 healthy volunteers from the Dominican Republic were genotyped for DPYD variants by qPCR, and individual genomic ancestry analysis was performed in 178 individuals using 90 informative ancestry markers. Data from the 1000 Genomes project were also retrieved for comparison and increased statistical power. Results and Conclusions: The c.557A>G variant (decreased dihydropyrimidine dehydrogenase function) presented a frequency of 2.6% in the Dominican population. Moreover, the frequency of this variant is positively associated with African ancestry (r2 = 0.67, p = 1 × 10-7), which implies that individuals with high levels of African ancestry are more likely to present this variant. HapB3 is completely absent in Dominican, Mexican, Peruvian, Bangladeshi, and all East Asian and African populations, which probably makes its analysis dispensable in these populations. The implementation of pharmacogenetics in oncology, specifically DPYD, in populations of Afro-Latin American ancestry should include c.557A>G, to be able to carry out the safe and effective treatment of patients treated with fluoropyrimidines.

Frequency of DPYD gene variants and phenotype inference in a Southern Brazilian population

Fluoropyrimidines are chemotherapy drugs that may cause severe adverse events, and their metabolism occurs by dihydropyrimidine deydrogenase (DPD), coded by DPYD. Variants in the DPYD were associated to a greater risk of toxicity. Our aim was to determine the frequency of the most relevant DPYD alleles according to CPIC guidelines (DPYD*2A-rs3918290, DPYD*13-rs55886062, rs67376798, and HapB3-rs75017182) in a sample of 800 healthy Southern Brazilians. Frequencies for rs3918290, rs75017182, and rs67376798 were 0.25%, 1.06%, and 0.38%, respectively. No rs55886062 allele was detected. In total, 3.4% of individuals were classified as intermediate metabolizers. Frequencies for rs3918290, rs55886062, and rs67376798 were similar to those found in non-Finnish Europeans; however, rs75017182 was less frequent when compared to non-Finnish Europeans, but more frequent than in Africans and East Asians. rs3918290 and rs67376798 also presented higher frequency when compared to Africans. The Latino population was the only one that did not differ from our sample in any variant analyzed. The frequencies for all the other populations (non-Finnish European, African, South Asian, and East Asian) presented differences from our sample in at least one variant. rs115232898 was not analyzed in the present study. Cost-effective studies should be performed to evaluate the implementation of these tests in the clinical practice in the Southern Brazil.

Implementation of a pharmacogenomic program in a Brazilian public institution

This narrative review describes implementation, current status and perspectives of a pharmacogenomic (PGx) program at the Brazilian National Cancer Institute (INCA), targeting the cancer chemotherapeutic drugs – fluoropyrimidines, irinotecan and thiopurines. This initiative, designed as a research project, was supported by a grant from the Brazilian Ministry of Health. A dedicated task force developed standard operational procedures from recruitment of patients to creating PGx reports with dosing recommendations, which were successfully applied to test 100 gastrointestinal cancer INCA outpatients and 162 acute lymphoblastic leukemia pediatric patients from INCA and seven other hospitals. The program has been subsequently expanded to include gastrointestinal cancer patients from three additional cancer treatment centers. We anticipate implementation of routine pre-emptive PGx testing at INCA but acknowledge challenges associated with this transition, such as continuous financing support, availability of trained personnel, adoption of the PGx-informed prescription by the clinical staff and, ultimately, evidence of cost–effectiveness.