Interethnic Variability in CYP2D6, CYP2C9, and CYP2C19 Genes and Predicted Drug Metabolism Phenotypes Among 6060 Ibero- and Native Americans: RIBEF-CEIBA Consortium Report on Population Pharmacogenomics.

Pharmacogenetic variation in Latin Americans is understudied, which sets a barrier for the goal of global precision medicine. The RIBEF-CEIBA Network Consortium was established to characterize interindividual and between population variations in CYP2D6, CYP2C9, and CYP2C19 drug metabolizing enzyme genotypes, which were subsequently utilized to catalog their "predicted drug metabolism phenotypes" across Native American and Ibero American populations. Importantly, we report in this study, a total of 6060 healthy individuals from Ibero-America who were classified according to their self-reported ancestry: 1395 Native Americans, 2571 Admixed Latin Americans, 96 Afro-Latin Americans, 287 white Latin Americans (from Cuba), 1537 Iberians, and 174 Argentinean Ashkenazi Jews. Moreover, Native Americans were grouped into North-, Central-, and South Amerindians (from Mexico, Costa Rica, and Peru, respectively). All subjects were studied for the most common and functional CYP2D6, CYP2C9, and CYP2C19 allelic variants, and grouped as genotype-predicted poor or ultrarapid metabolizer phenotypes (gPMs and gUMs, respectively). Native Americans showed differences from each ethnic group in at least two alleles of CYP2D6, CYP2C9, and CYP2C19. Native Americans had higher frequencies of wild-type alleles for all genes, and lower frequency of CYP2D6*41, CYP2C9*2, and CYP2C19*17 (p < 0.05). Native Americans also showed less CYP2C19 gUMs than the rest of the population sample. In addition, differences within Native Americans (mostly North vs. South) were also found. The interethnic differences described supports the need for population-specific personalized and precision medicine programs for Native Americans. To the best of our knowledge, this is the largest study carried out in Native Americans and other Ibero-American populations analyzing CYP2D6, CYP2C9, and CYP2C19 genetic polymorphisms. Population pharmacogenomics is a nascent field of global health and warrants further research and education.

CYP450 Genotype/Phenotype Concordance in Mexican Amerindian Indigenous Populations-Where to from Here for Global Precision Medicine?

Global precision medicine demands characterization of drug metabolism and phenotype variation in diverse populations, including the indigenous societies. A related question is the extent to which CYP450 drug metabolizing enzyme genotype and phenotype data are concordant and whether they can be used interchangeably. These issues are increasingly debated as precision medicine continues to expand as a popular research topic worldwide. We report here the first study in clinically relevant CYP450 drug metabolism phenotypes and genotypes in Mexican Amerindian indigenous subjects. In a large sample of 450 unrelated and medication free Mexican Amerindian indigenous healthy persons from four Mexican states (Chihuahua, Durango, Nayarit, and Sonora), we performed multiplexed phenotyping for the CYP1A2, CYP2C9, CYP2C19, CYP2D6, and CYP3A4 drug metabolizing enzymes using the CEIBA cocktail and genotyped the same pathways for functional polymorphic variation. Remarkable interindividual variability was found for the actual drug metabolizing capacity of all the enzymes analyzed, and, more specifically, the metabolic ratios calculated were significantly different across individuals with different number of active alleles for CYP2C9, CYP2C19, and CYP2D6. The drug metabolizing capacity "predicted" from the genotype determined was not in accordance with the actual capacity "measured" by phenotyping in several individuals for CYP2C9, CYP2C19, and CYP2D6. Consequently, a more extensive genotyping of the main CYP enzymes, including rare variants, together with the analysis of the actual drug metabolizing capacity using an appropriate phenotyping approach will add valuable information for accurate drug metabolism studies, especially useful in understudied populations such as Mexican Amerindians. In sum, this study demonstrates that current personalized medicine strategies based on "predicted" phenotype from genotyping of alleles with high frequency in European populations are not adequate for Mestizos and Native American populations.

Lessons from Cuba for Global Precision Medicine: CYP2D6 Genotype Is Not a Robust Predictor of CYP2D6 Ultrarapid Metabolism.

A long-standing question and dilemma in precision medicine is whether and to what extent genotyping or phenotyping drug metabolizing enzymes such as CYP2D6 can be used in real-life global clinical and societal settings. Although in an ideal world using both genotype and phenotype biomarkers are desirable, this is not always feasible for economic and practical reasons. Moreover, an additional barrier for clinical implementation of precision medicine is the lack of correlation between genotype and phenotype, considering that most of the current methods include only genotyping. Thus, the present study evaluated, using dextromethorphan as a phenotyping probe, the relationship between CYP2D6 phenotype and CYP2D6 genotype, especially for the ultrarapid metabolizer (UM) phenotype. We report in this study, to the best of our knowledge, the first comparative clinical pharmacogenomics study in a Cuban population sample (N = 174 healthy volunteers) and show that the CYP2D6 genotype is not a robust predictor of the CYP2D6 ultrarapid metabolizer (mUM) status in Cubans. Importantly, the ultrarapid CYP2D6 phenotype can result in a host of health outcomes, such as drug resistance associated with subtherapeutic drug concentrations, overexposure to active drug metabolites, and altered sensitivity to certain human diseases by virtue of altered metabolism of endogenous substrates of CYP2D6. Hence, phenotyping tests for CYP2D6 UMs appear to be a particular necessity for precision medicine in the Cuban population. Finally, in consideration of ethical and inclusive representation in global science, we recommend further precision medicine biomarker research and funding in support of neglected or understudied populations worldwide.

Pharmacogenetic research activity in Central America and the Caribbean: a systematic review.

AIM: The present review was aimed at analyzing the pharmacogenetic scientific activity in Central America and the Caribbean. MATERIALS & METHODS: A literature search for pharmacogenetic studies in each country of the region was conducted on three databases using a list of the most relevant pharmacogenetic biomarkers including 'phenotyping probe drugs' for major drug metabolizing enzymes. The review included 132 papers involving 47 biomarkers and 35,079 subjects (11,129 healthy volunteers and 23,950 patients). RESULTS: The country with the most intensive pharmacogenetic research was Costa Rica. The most studied medical therapeutic area was oncology, and the most investigated biomarkers were CYP2D6 and HLA-A/B. Conclusion: Research activity on pharmacogenetics in Central American and the Caribbean populations is limited or absent. Therefore, strategies to promote effective collaborations, and foster interregional initiatives and research efforts among countries from the region could help for the rational clinical implementation of pharmacogenetics and personalized medicine.

Relevance of the ancestry for the variability of the Drug-Metabolizing Enzymes CYP2C9, CYP2C19 and CYP2D6 polymorphisms in a multiethnic Costa Rican population / Relevancia de la ancestría para la variabilidad de polimorfismos de las enzimas metabolizadoras de fármacos CYP2C9, CYP2C19 y CYP2D6 en una población multiétnica de Costa Rica

Abstract:CYP2C9, CYP2C19 and CYP2D6 metabolize around 40 % of drugs and their genes vary across populations. The Costa Rican population has a trihybrid ancestry and its key geographic location turns it into a suitable scenario to evaluate interethnic differences across populations. This study aims to describe the diversity of CYP2C9, CYP2C19 and CYP2D6 polymorphisms in Costa Rican populations in the context of their ancestry. A total of 448 healthy individuals were included in the study: Bribri (n= 47), Cabécar (n= 27), Maleku (n= 16), Guaymí (n= 30), Huetar (n= 48), Chorotega (n= 41), Admixed/Mestizos from the Central Valley/Guanacaste (n= 189), and Afro-Caribbeans (n= 50) from Limón. CYP2C9 (alleles *2, *3, *6) and CYP2C19 (*2, *3, *4, *5, *17) genotypes were determined by Real-Time PCR. African, European and Native American ancestry were inferred using 87 ancestry informative markers. The frequency of the decreased activity allele CYP2C9*2 is lower in the self-reported Amerindian groups compared to the admixed population, and the highest frequencies of CYP2C19*2 (null activity) and the CYP2C19*17 (increased activity) were found in the self-reported AfroCaribbean population. Moreover, a frequency of 0.7 % CYP2C9 gPMs in the Admixed population and a variable frequency of CYP2C19 gUMs (0.0-32.6 %, more prevalent in Afro-Caribbeans) in Costa Rican populations, was found. Finally, the following alleles were positively correlated with genomic African ancestry and negatively correlated with genomic Native American ancestry: CYP2D6*5 (null activity), CYP2D6*17 (decreased activity), CYP2D6*29 (decreased activity) and CYP2C19*17 (increased activity). No correlation for CYP2C9 polymorphisms and genomic ancestry was found. Further studies assessing the CYP2C9 and CYP2C19 sequence in these populations, preferentially by sequencing these genes, are warranted. Rev. Biol. Trop. 64 (3): 1067-1076. Epub 2016 September 01.

ResumenCYP2C9, CYP2C19 y CYP2D6 metabolizan aproximadamente el 40 % de los fármacos y los genes que las codifican varían en las distintas poblaciones humanas. La población costarricense posee ancestría trihíbrida y su posición geográfica estratégica la convierten en un escenario idóneo para evaluar la variabilidad interétnica en sus poblaciones multiétnicas. El presente estudio tiene como objetivo describir la diversidad de los polimorfismos CYP2C9, CYP2C19 y CYP2D6 en las poblaciones costarricenses en el contexto de su ancestría. Un total de 448 individuos sanos fueron incluidos: Bribri (n= 47), Cabécar (n= 27), Maleku (n= 16), Guaymí (n= 30), Huetar (n= 48), Chorotega (n= 41), mestizos del Valle Central y Guanacaste (n= 189) y afrocaribeños de Limón (n= 50). Los genotipos CYP2C9 (alelos *2, *3, *6) y CYP2C19 (*2, *3, *4, *5 y *17) fueron determinados mediante PCR tiempo real. Las ancestrías africana, europea y nativa americana fueron inferidas usando 87 marcadores informativos de ancestría. La frecuencia del alelo de actividad disminuida CYP2C9*2 fue menor en los grupos autodefinidos de amerindios que en la población mestiza y las frecuencias más altas de CYP2C19*2 (actividad nula) y CYP2C19*17 (actividad incrementada) se encontraron en la población autodefinida afrocaribeña. Asimismo, se encontró una frecuencia de gPMs CYP2C9 de 0.7 % en la población mestiza y una frecuencia variable de gUMs CYP2C19 (0.0 a 32.6 %, más prevalente en afrocaribeños) en las poblaciones costarricenses. Por último, los siguientes alelos fueron positivamente correlacionados con la ancestría africana y negativamente con la ancestría nativa americana: CYP2D6*5 (actividad nula), CYP2D6*17, CYP2D6*29 (ambos de actividad disminuida) y CYP2C19*17 (actividad incrementada). No se encontró correlación entre los polimorfismos CYP2C9 y la ancestría. Se requieren estudios posteriores que evalúen la secuencia de CYP2C9 y CYP2C19 en estas poblaciones, preferiblemente mediante la secuenciación de estos genes.

Relevance of the ancestry for the variability of the Drug-Metabolizing Enzymes CYP2C9, CYP2C19 and CYP2D6 polymorphisms in a multiethnic Costa Rican population.

CYP2C9, CYP2C19 and CYP2D6 metabolize around 40% of drugs and their genes vary across populations. The Costa Rican population has a trihybrid ancestry and its key geographic location turns it into a suitable scenario to evaluate interethnic differences across populations. This study aims to describe the diversity of CYP2C9, CYP2C19 and CYP2D6 polymorphisms in Costa Rican populations in the context of their ancestry. A total of 448 healthy individuals were included in the study: Bribri (n= 47), Cabécar (n= 27), Maleku (n= 16), Guaymí (n= 30), Huetar (n= 48), Chorotega (n= 41), Admixed/Mestizos from the Central Valley/Guanacaste (n= 189), and Afro-Caribbeans (n= 50) from Limón. CYP2C9 (alleles *2, *3, *6) and CYP2C19 (*2, *3, *4, *5, *17) genotypes were determined by Real-Time PCR. African, European and Native American ancestry were inferred using 87 ancestry informative markers. The frequency of the decreased activity allele CYP2C9*2 is lower in the self-reported Amerindian groups compared to the admixed population, and the highest frequencies of CYP2C19*2 (null activity) and the CYP2C19*17 (increased activity) were found in the self-reported Afro-Caribbean population. Moreover, a frequency of 0.7 % CYP2C9 gPMs in the Admixed population and a variable frequency of CYP2C19 gUMs (0.0-32.6 %, more prevalent in Afro-Caribbeans) in Costa Rican populations, was found. Finally, the following alleles were positively correlated with genomic African ancestry and negatively correlated with genomic Native American ancestry: CYP2D6*5 (null activity), CYP2D6*17 (decreased activity), CYP2D6*29 (decreased activity) and CYP2C19*17 (increased activity). No correlation for CYP2C9 polymorphisms and genomic ancestry was found. Further studies assessing the CYP2C9 and CYP2C19 sequence in these populations, preferentially by sequencing these genes, are warranted.

Worldwide interethnic variability and geographical distribution of CYP2C9 genotypes and phenotypes.

INTRODUCTION: Notably differences in CYP2C9 allele frequencies among worldwide populations have been reported, with an interesting low frequency of the CYP2C9*2 allele in Amerindians compared with Admixed and European populations. AREAS COVERED: Literature was searched using the PubMed database and was focused on worldwide original research papers on CYP2C9 alleles and CYP2C9 phenotypes ("predicted" from CYP2C9 genotypes and "measured" metabolic phenotype with a probe drug) among healthy volunteers according to their ethnicity and geographical distribution. Seventy-eight original research articles including a total of 31,978 subjects were identified. EXPERT OPINION: CYP2C9*2 allele is the most frequent in Caucasian populations (average 14%), with the lowest frequencies for Africans (0.46%), East Asians (0.56%) and Native Americans (1.25%), which is in agreement with the hypothesis about the low prevalence in Amerindians. CYP2C9*3 shows the highest frequency among South Asians (11.7%), while CYP2C9*5 (1.56%) and *8 (4.70%) in African Americans. The predicted poor metabolizers (gPMs) were found overall in a low frequency, with the highest frequency detected for South Asians, in accordance with the CYP2C9*3 frequency in these populations. This study shows the worldwide variability in the CYP2C9 allele frequencies across different ethnic and geographic groups. Data about CYP2C9 "measured" metabolic phenotypes is still limited.

Pharmacogenetics in Central American healthy volunteers: interethnic variability.

Ethnicity is one of the major factors involved in interindividual variability to drug response. This study aims to describe the frequency of the most relevant pharmacogenetic biomarkers and metabolic phenotypes in Central American healthy volunteers and to determine its interethnic variability. Twenty-six original research articles on allelic, genotypes or metabolic phenotype frequencies were analyzed, in which a total number of 7611 Central American healthy volunteers were included (6118 were analyzed for genotype and 1799 for metabolic phenotype). No reports were available for population from Belize and Honduras. The CYP2D6*4 and *5 frequencies in Amerindian populations from Costa Rica have shown to be among the highest frequencies so far reported in the world. Furthermore, NAT2*5 and *6 presented higher frequencies in admixed populations than in Amerindians, but, inversely, the NAT2*7 was more frequent in Amerindians compared to an admixed population. Likewise, different patterns of distribution have been shown in HLA-A*02, *03 and HLA-B*07 among Native populations from Latin America. Reports on Central American populations were also found for the CYP2C19, LDLR, CYP2E1, MDR1, G6PD, TP53, CYP1A2, CYP3A4 and CYP3A5 biomarkers, but no data were available for the other 91 pharmacogenetic biomarkers revised in Central American populations. Differences in the frequency of some pharmacogenetic biomarkers and metabolic phenotypes were found, showing interethnic variability within Central American and with other Latin American populations.

Ethnic background and CYP2D6 genetic polymorphisms in Costa Ricans / Antecedentes étnicos y polimorfismo genético del CYP2D6 en los costarricenses

CYP2D6 differences have already been demonstrated within Latin American populations by the CEIBA.FP Consortium of the Ibero-American Network of Pharmacogenetics (RIBEF, as per the acronym in Spanish). However, within the population of Costa Rica, no research has been conducted until now, even though this population has a trihybrid component ancestry that represents an interesting condition. Thus, the present study was aimed to determine the frequency of Ultra-rapid Metabolizers (UMs) and Poor Metabolizers (PMs) in a Costa Rican population, as well as to determine whether there are differences in the CYP2D6-predicted phenotype frequencies among three Costa Rican groups with different ethnic backgrounds. Additionally, these frequencies of PMs and UMs obtained were compared with Ibero-American populations published data. Finally, we also aimed to describe allele frequencies among different Costa Rican ethnic groups. This research has been undertaken within the framework of the RIBEF CEIBA Consortium studies on Latin American populations. A total of 385 individuals were included in the study: 139 mestizos, 197 Amerindians, and 49 Afro-Caribbeans. CYP2D6 genotypes were determined by XL-PCR and Real-Time PCR. The CYP2D6 variant alleles *2, *3, *4, *5, *6, *10, *17, *29, *35 and *41 were also determined. For the entire Costa Rican population, the frequency of PMs and UMs was 6% and 6.5%, respectively. The percentage of UMs in the mestizo population was higher than in the Amerindian population. CYP2D6 UMs vary from 3.6% to 10.1% and PMs from 1.4% to 10.2% among three Costa Rican groups. The highest frequencies of UMs (10.1%) and PMs (10.2%) were found in the mestizo and Amerindian populations, respectively. In conclusion, the frequencies of UMs and PMs for CYP2D6 varied widely across the mestizo, Amerindian and Afro-Caribbean Costa Rican populations. Future research in this population should be oriented to identify new CYP2D6 variants through sequencing methods, as well as to determine CYP2D6 phenotype, in order to establish the phenotype-genotype relation. Finally, further studies involving genetic markers of ancestry are needed in the Costa Rican population.

El Consorcio de la Red Iberoamericana de Farmacogenética CEIBA.FP ha demostrado que existen diferencias en cuanto a CYP2D6 en las poblaciones latinoamericanas. Sin embargo, hasta ahora, se sabe poco de este gen de importancia farmacogenética en la población de Costa Rica, la cual tiene una ancestría trihíbrida. El presente estudio tiene como objetivos: determinar la frecuencia de los fenotipos extrapolados de CYP2D6 en una población costarricense y determinar si existen diferencias en cuanto a las frecuencias de metabolizadores lentos (PMs) y ultra-rápidos (UMs) entre tres grupos con distinto origen étnico. Adicionalmente, las frecuencias de PMs y UMs obtenidas en este estudio fueron comparadas con datos de poblaciones iberoamericanas. Por último, se pretende describir las frecuencias alélicas en los distintos grupos. En el estudio se incluyeron 385 muestras de individuos: 139 mestizos, 197 amerindios y 49 afro-caribeños. Los genotipos CYP2D6 fueron determinados por XL-PCR y PCR tiempo real. Se determinaron las variantes alélicas *2, *3, *4, *5, *6, *10, *17, *29, *35 y *41. Para la población total estudiada las frecuencia de PMs y UMs fueron respectivamente 6% y 6.5%. El porcentaje de individuos UMs fue mayor en la población mestiza que en la amerindia. La frecuencia de UMs varió de 3.6 a 10.1% y la de PMs de 1.4 a 10.1% en los grupos costarricenses. Las frecuencias más altas de UMs (10.1%) y de PMs (10.2%) se encontraron respectivamente en las poblaciones mestiza y amerindia. En conclusión, las frecuencias de UMs y PMs de CYP2D6 varían ampliamente en las poblaciones mestiza, amerindia y afro-caribeña de Costa Rica. Investigaciones futuras en la población de Costa Rica deberían orientarse a identificar nuevas variantes del CYP2D6 mediante métodos de secuenciación, así como a determi- nar el fenotipo de CYP2D6 con el objetivo de establecer la relación fenotipo-genotipo. Finalmente, es necesario realizar estudios adicionales que involucren marcadores genéticos de ancestría en la población costarricense.

Interethnic variability of CYP2D6 alleles and of predicted and measured metabolic phenotypes across world populations.

INTRODUCTION: The frequency of CYP2D6 alleles, related to either a lack of or increased enzymatic activity, which may lead to poor metabolism (PM) or ultrarapid metabolism (UM), can vary across ethnic groups and hence across geographic regions. AREAS COVERED: Worldwide original research papers on CYP2D6 allelic frequencies, metabolic phenotype frequencies measured with a probe drug, and/or genotype frequencies that studied > 50 healthy volunteers, were included in analyses to describe the distributions of alleles, phenotypes predicted from genotypes (predicted poor metabolizers [gPMs], predicted ultrarapid metabolizers [gUMs]) and metabolic phenotypes (mPMs, mUMs) across ethnic groups and geographic regions. The analysis included 44,572 individuals studied in 172 original research papers. EXPERT OPINION: As of today, Africa and Asia are under-represented in this area relative to the total number of their inhabitants, so that further studies in these regions are warranted. The CYP2D6*4 allele frequency was higher in Caucasians, CYP2D6*10 in East Asians, CYP2D6*41 and duplication/multiplication of active alleles in Middle Easterns, CYP2D6*17 in Black Africans and CYP2D6*29 in African Americans, than in other ethnic groups. Overall, gPMs and mPMs are more frequent among Caucasians, and gUMs among Middle Easterns and Ethiopians. However, mUMs could not be evaluated because only two studies were found presenting this information. Further studies including mUMs are thus warranted. There is a correspondence between gPMs and mPMs, but the few studies of mUMs meant that their relationship with gUMs could not be demonstrated. Finally, evolutionary aspects of the CYP2D6 allele distribution appear to support the Great Human Expansion model.

CYP2D6 gene polymorphisms and predicted phenotypes in eight indigenous groups from northwestern Mexico.

AIM: Polymorphisms in CYP2D6 impact the interindividual and interethnic variability of drug efficiency; therefore, we determined the CYP2D6 allele distribution in eight Amerindian groups from northwestern Mexico and compared them with the frequencies in Mexican Mestizos. MATERIALS & METHODS: A total of 508 Amerindians were studied. Genotyping of CYP2D6*5 and multiplication alleles was performed by long-range PCR, while CYP2D6*2, *3, *4, *6, *10, *17, *29, *35, *41 and copy number were evaluated by real-time PCR. RESULTS: The most frequent alleles were CYP2D6*2 (0.05-0.28), CYP2D6*4 (0.003-0.21) and multiplications (0.043-0.107). CYP2D6*5, *6, * 10 and *41 were not observed in the majority of Amerindians, and CYP2D6*3, *17, *35 and *29 were not detected. The poor metabolizer genotype ( *4/*5) was lower (0.2%) in Amerindians than in Mestizos (5%); conversely, the ultrarapid metabolizer genotype was higher (12.6%) in indigenous groups than in Mestizos (7%). CONCLUSION: Our data show a lower frequency of CYP2D6 inactive alleles and a higher frequency of duplication/multiplication of CYP2D6 active alleles in indigenous populations that in Mestizos. Original submitted 14 August 2013; Revision submitted 7 October 2013.

Ethnic background and CYP2D6 genetic polymorphisms in Costa Ricans.

CYP2D6 differences have already been demonstrated within Latin American populations by the CEIBA.FP Consortium of the Ibero-American Network of Pharmacogenetics (RIBEF, as per the acronym in Spanish). However, within the population of Costa Rica, no research has been conducted until now, even though this population has a trihybrid component ancestry that represents an interesting condition. Thus, the present study was aimed to determine the frequency of Ultra-rapid Metabolizers (UMs) and Poor Metabolizers (PMs) in a Costa Rican population, as well as to determine whether there are differences in the CYP2D6-predicted phenotype frequencies among three Costa Rican groups with different ethnic backgrounds. Additionally, these frequencies of PMs and UMs obtained were compared with Ibero-American populations published data. Finally, we also aimed to describe allele frequencies among different Costa Rican ethnic groups. This research has been undertaken within the framework of the RIBEF CEIBA Consortium studies on Latin American populations. A total of 385 individuals were included in the study: 139 mestizos, 197 Amerindians, and 49 Afro-Caribbeans. CYP2D6 genotypes were determined by XL-PCR and Real-Time PCR. The CYP2D6 variant alleles *2, *3, *4, *5, *6, *10, "17, *29, *35 and *41 were also determined. For the entire Costa Rican population, the frequency of PMs and UMs was 6% and 6.5%, respectively. The percentage of UMs in the mestizo population was higher than in the Amerindian population. CYP2D6 UMs vary from 3.6% to 10.1% and PMs from 1.4% to 10.2% among three Costa Rican groups. The highest frequencies of UMs (10.1%) and PMs (10.2%) were found in the mestizo and Amerindian populations, respectively. In conclusion, the frequencies of UMs and PMs for CYP2D6 varied widely across the mestizo, Amerindian and Afro-Caribbean Costa Rican populations. Future research in this population should be oriented to identify new CYP2D6 variants through sequencing methods, as well as to determine CYP2D6 phenotype, in order to establish the phenotype-genotype relation. Finally, further studies involving genetic markers of ancestry are needed in the Costa Rican population.

Evaluation of drug-metabolizing enzyme hydroxylation phenotypes in Hispanic populations: the CEIBA cocktail.

Interindividual differences in response to drug treatments are mainly caused by differences in drug metabolism, in which cytochrome P450 (CYP450) enzymes are involved. Genetic polymorphisms of these enzymes have a key role in this variability. However, environmental factors, endogenous metabolism and disease states also have a great influence on the actual drug metabolism rate (metabolic phenotype). Consequently, the genotype does not always correlate with the actual drug hydroxylation phenotype. In this sense, in vivo phenotyping strategies represent an alternative to evaluate the interindividual variability in drug metabolism. Therefore, the 'cocktail' approach is considered as an advantageous strategy to obtain actual and reliable information on several CYP activities in just one experiment. As reviewed, phenotyping studies on Latin-American populations, which comprise about 400 million people, are scarce, and only selective phenotyping methods were applied. Therefore, a novel cocktail approach is here proposed as a phenotyping tool to evaluate the relationship between genotype and phenotype of major CYP enzymes in Hispanic populations. This determination will allow adaptation of drug therapies to these populations and consequently to benefit from the application of pharmacogenetics in the reduction of drug adverse effects and in the improvement of therapeutic responses.

Characterization of CYP2D6 genotypes and metabolic profiles in the Portuguese population: pharmacogenetic implications.

AIM: CYP2D6 codes for a protein that is vastly involved in the metabolism of various substances. This gene is highly polymorphic, which influences the enzymatic activity and contributes to the huge variability in the enzyme hydroxylation capacity. Different metabolic profiles determine the processing of xenobiotics and endobiotics, thereby influencing disease risk, therapeutic efficacy and side effects, or toxicity of xenobiotics. The aim of this work was to characterize CYP2D6 polymorphisms and predict metabolic profiles in the Portuguese population. SUBJECTS & METHODS: The study comprised 300 Portuguese unrelated healthy adult volunteers. Genetic analysis included allelic discrimination and copy number determination with TaqMan® probes by real-time PCR and allele duplications of CYP2D6*1, CYP2D6*2, CYP2D6*4 and CYP2D6*10 were confirmed by long PCR and PCR-RFLP. RESULTS: The percentages of poor and ultrarapid metabolizers found in this Portuguese population were 6.3 and 4.7%, respectively. DISCUSSION & CONCLUSION: Compared with other studies, such as in Spaniards, the allelic frequencies observed were similar, with some exceptions, such as for CYP2D6*10, which is higher in the Portuguese population, and for CYP2D6*6 and duplication of *1 and *2, appearing in lower frequencies in the present study. These results allow the determination of the frequency of the most relevant CYP2D6 polymorphisms and the prediction of the enzyme metabolic activity, being of much importance for the CYP2D6 pharmacogenetics approach in the Portuguese population. The data presented here are significant for the study of genetic variability influencing CYP2D6 activity, to improve the effectiveness and safety of xenobiotics exposure, also can be used as a tool in clinical practice for the development of individualized pharmacotherapy.

Development of a HPLC method for the determination of losartan urinary metabolic ratio to be used for the determination of CYP2C9 hydroxylation phenotypes.

BACKGROUND: Losartan is metabolized to losartan carboxylic acid (E-3174) by the polymorphic cytochrome CYP2C9. The aim of the study was to develop a high-performance liquid chromatographic (HPLC) method with fluorescence detection for simultaneously measuring losartan and its metabolite E-3174 in urine to evaluate the losartan urinary metabolic ratio (MR: losartan/E-3174) for CYP2C9 phenotyping in humans. METHODS: The compounds were separated in a reversed-phase chromatographic column and detected by fluorescence at a wavelength of 250 nm for excitation and of 370 nm for emission. RESULTS: No analytical interferences with endogenous compounds were found, and the extraction recoveries were over 88%. Limits of quantification of 2 ng mL-1 for losartan and 5 ng mL-1 for E-3174 were achieved, as well as good reproducibility with coefficients of variation of <9% in all cases. Analyses with the present HPLC method show significant differences (p<0.05) in losartan MRs between the four CYP2C9 genotype groups in 13 Spanish healthy volunteers. CONCLUSIONS: The method developed is simple and affordable, as well as sensitive and reliable to calculate the MR. Therefore, it appears to be useful for CYP2C9 phenotyping using losartan as a drug test in populations, such as Hispanics with different allele combinations.

High-performance liquid chromatography method using ultraviolet detection for the quantification of aripiprazole and dehydroaripiprazole in psychiatric patients.

BACKGROUND: Aripiprazole (ARI) is an antipsychotic drug that is metabolized to dehydroaripiprazole (DARI) by CYP2D6. Because of the large interindividual variability in ARI and DARI plasma concentrations, therapeutic drug monitoring may be of use in psychiatric patients during treatment with ARI. The aim of the present study was to develop a simple and reliable method for the quantitative determination of ARI and DARI in plasma using liquid-liquid extraction and reverse-phase high-performance liquid chromatography (HPLC) with ultraviolet (UV) detection. The method was tested in psychiatric patients during regular treatment with ARI. METHODS: Separation was by the liquid-liquid method, and UV detection at 254 nm. Linear responses for ARI and DARI were obtained between 2 and 1000 ng/mL, and precision assays were lower than 10.4 for both analytes. RESULTS: Lower limit of quantification and detection were 1 and 0.38 ng/mL for ARI and 0.78 and 0.44 ng/mL for DARI, respectively. The method was successfully applied to plasma samples drawn from 22 patients with concentrations ranging between 2 and 189 ng/mL for ARI and between 11 and 359 ng/mL for DARI. CONCLUSIONS: The chromatographic method developed has been demonstrated to be sensitive and reliable for the measurement of ARI and DARI simultaneously in human plasma, and the present method represents an alternative procedure to evaluate plasma concentration in patients during treatment with ARI.