Neonatal Abstinence Syndrome and Corresponding Pharmacotherapy Approaches from 2 University-affiliated Neonatal Intensive Care Units in Puerto Rico (2018-2020)

OBJECTIVE

Neonatal abstinence syndrome (NAS) is a set of drug withdrawal symptoms suffered by neonates exposed to drugs in utero. Several studies have widely described NAS incidence and treatment approach; however, little is known regarding the incidence and manifestations of this disease in Puerto Rico (PR). The principal aim of this study was to describe NAS incidence in the neonatal units of hospitals affiliated with the University of PR in terms of occurrence, clinical manifestations, and treatment approaches.

METHODS

Our study evaluated the medical records of NAS babies diagnosed from 2018 through 2020 at 2 hospitals affiliated with the University of PR Medical Sciences Campus. Descriptive and inferential statistics were employed to analyze trends.

RESULTS

We identified 12 neonates diagnosed with NAS, 5 with low birthweights (<2500 g); for a NAS incidence of 2 cases per 1000 admitted for the 3 years of recollected data. The urine toxicology results revealed that 9 had experienced intrauterine polydrug exposure. Phenobarbital loading dose were determined on the day of diagnosis (indicated by Finnegan score). The first manifestation of NAS symptoms varied: 8 neonates showed symptoms within 48 hours after birth, whereas 4 had withdrawal symptoms within 72-120 hours of their births. Differences between dosing practices and guidelines were observed, ranging from a 0.69% to a 25% difference during treatment initiation.

CONCLUSION

Further research on the incidence of NAS in PR (national level) is needed for a deeper understanding that we hope will lead to the development of enhanced treatment protocols in PR.

New insights into the role of VKORC1 polymorphisms for optimal warfarin dose selection in Caribbean Hispanic patients through an external validation of a population PK/PD model

Warfarin, an oral anticoagulant, has been used for decades to prevent thromboembolic events. The complex interplay between CYP2C9 and VKORC1 genotypes on warfarin PK and PD properties is not fully understood in special sub-groups of patients. This study aimed to externally validate a population pharmacokinetic/pharmacodynamic (PK/PD) model for the effect of warfarin on international normalized ratio (INR) and to evaluate optimal dosing strategies based on the selected covariates in Caribbean Hispanic patients. INR, and CYP2C9 and VKORC1 genotypes from 138 patients were used to develop a population PK/PD model in NONMEM. The structural definition of a previously published PD model for INR was implemented. A numerical evaluation of the parameter-covariate relationship was performed. Simulations were conducted to determine optimal dosing strategies for each genotype combinations, focusing on achieving therapeutic INR levels. Findings revealed elevated IC50 for G/G, G/A, and A/A VKORC1 haplotypes (11.76, 10.49, and 9.22 mg/L, respectively), in this population compared to previous reports. The model-guided dosing analysis recommended daily warfarin doses of 3-5 mg for most genotypes to maintain desired INR levels, although subjects with combination of CYP2C9 and VKORC1 genotypes * 2/* 2-, * 2/* 3- and * 2/* 5-A/A would require only 1 mg daily. This research underscores the potential of population PK/PD modeling to inform personalized warfarin dosing in populations typically underrepresented in clinical studies, potentially leading to improved treatment outcomes and patient safety. By integrating genetic factors and clinical data, this approach could pave the way for more effective and tailored anticoagulation therapy in diverse patient groups.

Implementing a Pharmacogenomic-driven Algorithm to Guide Antiplatelet Therapy among Caribbean Hispanics: A non-randomized prospective cohort study

Background

After percutaneous coronary intervention (PCI), clopidogrel resistant patients are at an increased risk of major adverse cardiovascular and cerebrovascular events (MACCEs). We aimed to assess whether genotype-guided selection of oral antiplatelet drugs using a clinical decision support (CDS) algorithm reduces the occurrence of these ischemic events and improves outcomes among Caribbean Hispanic patients from Puerto Rico, who are underrepresented in clinical pharmacogenomic (PGx)-guided implementation studies.

Methods

Individual platelet function testing (PRU) measures, CYP2C19*2 and PON1 rs662 genotypes, clinical and demographic data from 8 medical facilities were included. Patients were separated into standard of care (SoC) and genotype-guided groups (150 each). Risk scores were calculated based on a previously developed CDS risk prediction algorithm designed to make actionable treatment recommendations for each patient. Alternative therapy with ticagrelor was recommended for patients with a high risk score ≥2. Statistical associations between patient time free of MACCEs and predictor variables (i.e., treatment groups, risk scores) were tested in this population using Kaplan-Meier survival analyses and Cox proportional-hazards regression models.

Results

Median age of participants is 67 years; BMI: 27.8; 48% women; 14% smokers; 59% with type-2 diabetes mellitus (T2DM). Among patients with high-risk scores who were free from MACCE events 6 months after coronary stenting, genotype-driven guidance of antiplatelet therapy showed superiority over SoC in terms of reducing the incidence rate of atherothrombotic events.

Conclusions

The clinical utility of our PGx-driven CDS algorithm to reduce the incidence rate of MACCEs among post-PCI Caribbean Hispanic patients on clopidogrel was externally demonstrated.

Clinical Trial Registration Unique Identifier

NCT03419325.

Discovery of Ancestry-specific Variants Associated with Clopidogrel Response among Caribbean Hispanics

Background

High on-treatment platelet reactivity (HTPR) with clopidogrel is predictive of ischemic events in adults with coronary artery disease. Despite strong data suggesting HTPR varies with ethnicity, including clinical and genetic variables, no genome-wide association study (GWAS) of clopidogrel response has been performed among Caribbean Hispanics. This study aimed to identify genetic predictors of HTPR in a cohort of Caribbean Hispanic cardiovascular patients from Puerto Rico.

Methods

Local Ancestry inference (LAI) and traditional GWASs were performed on a cohort of 511 clopidogrel-treated patients, stratified based on their P2Y12 reaction units (PRU) into responders and non-responders (HTPR).

Results

The LAI GWAS identified variants within the CYP2C19 region associated with HTPR, predominantly driven by individuals of European ancestry and absent in those with native ancestry. Incorporating local ancestry adjustment notably enhanced our ability to detect associations. While no loci reached traditional GWAS significance, three variants showed suggestive significance at chromosomes 3, 14 and 22 (OSBPL10 rs1376606, DERL3 rs5030613, and RGS6 rs9323567). In addition, a variant in the UNC5C gene on chromosome 4 was associated with an increased risk of HTPR. These findings were not identified in other cohorts, highlighting the unique genetic landscape of Caribbean Hispanics.

Conclusion

This is the first GWAS of clopidogrel response in Hispanics, confirming the relevance of the CYP2C19 cluster, particularly among those with European ancestry, and also identifying novel markers in a diverse patient population. Further studies are warranted to replicate our findings in other diverse cohorts and meta-analyses.

Non-Random Enrichment of Single-Nucleotide Polymorphisms Associated with Clopidogrel Resistance within Risk Loci Linked to the Severity of Underlying Cardiovascular Diseases: The Role of Admixture

Cardiovascular disease (CVD) is one of the leading causes of death in Puerto Rico, where clopidogrel is commonly prescribed to prevent ischemic events. Genetic contributors to both a poor clopidogrel response and the severity of CVD have been identified mainly in Europeans. However, the non-random enrichment of single-nucleotide polymorphisms (SNPs) associated with clopidogrel resistance within risk loci linked to underlying CVDs, and the role of admixture, have yet to be tested. This study aimed to assess the possible interaction between genetic biomarkers linked to CVDs and those associated with clopidogrel resistance among admixed Caribbean Hispanics. We identified 50 SNPs significantly associated with CVDs in previous genome-wide association studies (GWASs). These SNPs were combined with another ten SNPs related to clopidogrel resistance in Caribbean Hispanics. We developed Python scripts to determine whether SNPs related to CVDs are in close proximity to those associated with the clopidogrel response. The average and individual local ancestry (LAI) within each locus were inferred, and 60 random SNPs with their corresponding LAIs were generated for enrichment estimation purposes. Our results showed no CVD-linked SNPs in close proximity to those associated with the clopidogrel response among Caribbean Hispanics. Consequently, no genetic loci with a dual predictive role for the risk of CVD severity and clopidogrel resistance were found in this population. Native American ancestry was the most enriched within the risk loci linked to CVDs in this population. The non-random enrichment of disease susceptibility loci with drug-response SNPs is a new frontier in Precision Medicine that needs further attention.

Local Ancestry-Informed Candidate Pathway Analysis of Warfarin Stable Dose in Latino Populations

Accuracy of warfarin dose prediction algorithms may be improved by including data from diverse populations in genetic studies of dose variability. Here, we surveyed single nucleotide polymorphisms in vitamin K-related genetic pathways for association with warfarin dose requirements in two admixed Latino populations in standard-principal component adjusted and contemporary-local ancestry adjusted regression models. A total of five variants from vitamin K-related genes/pathways were associated with warfarin dose in both cohorts (P < 0.0125) in standard models. Local ancestry-adjusted analysis unveiled 35 associated variants with absolute effects ranging from β = 9.04 ( ±2.23) to 39.18 ( ±10.89) per ancestral allele in the discovery cohort and β = 6.47 (± 2.02) to 17.82 (± 6.83) in the replication cohort. Importantly, we demonstrate the technical validity of the Tractor model in cohorts with admixed ancestry from three founder populations and bring attention to the technical hurdles obstructing the inclusion of diverse, especially admixed, populations in pharmacogenomic research.

N-Acetyl Cysteine and Glutathione in Health and Cancer-Pharmacogenomics, Research, and Clinical Practice: Hypothesis and Review

CONTEXT

Glutathione (GSH) is a major intracellular antioxidant capable of scavenging free radicals and detoxifying electrophiles from endogenous and exogenous sources via the free thiol group. GSH plays an important role in a multiple cellular process, including cell differentiation, proliferation, and apoptosis. Pharmacogenomics has demonstrated its important role as a key element in cellular health.

OBJECTIVE

The study intended to examine the benefits of using GSH pharmacogenomics as a therapy to prevent side effects and interactions with antineoplastic agents in the diagnosis and treatment of malignancies.

DESIGN

The research team performed a narrative review using the Google scholar and PubMed electronic databases.

CONCLUSIONS

In summary, the involvement of GSH in the carcinogenesis and drug resistance of tumor cells is clear and well understood, but further studies, aimed at understanding the GSH-driven molecular pathways, might be crucial to designing new therapeutic strategies to fight cancer progression, overcoming chemoresistance, using in combination with immunotherapies, and preventing or minimizing their negative side effects.

Experiences and Preferences of Opioid-Use-Disorder Patients Who Switched from Brand to Generic Buprenorphine/Naloxone Films: A Case Series

PURPOSE

Differences in the suppression of withdrawal symptoms have been observed in opioid-use-disorder (OUD) patients who were switched from Suboxone (the brand name of buprenorphine/naloxone sublingual films) to either 1 of 2 generic versions. These descriptive observations evidence the need to further assess the use of these generics and its impact on the adherence to and outcomes of OUD treatments. The objective of this case series was to describe patient and provider experiences, perceptions, and preferences when said patients were abruptly switched from Suboxone to one of the generic versions manufactured by Sandoz or Alvogen.

PATIENTS AND METHODS

A retrospective chart review of 24 Suboxone-maintained OUD patients from a single clinic who were forced to switch to a generic was performed to collect withdrawal and craving symptoms that occurred after the switch, as well as toxicology results and changes in dose (documented by the provider).

RESULTS

The medical records of 9 (37.5%) of the 24 patients showed that they were suffering from withdrawal symptoms and/or cravings, had had their doses adjusted, and/or had had a positive urine toxicology screen. All 9 subjects communicated a preference for the brand formulation over that of either of the generic versions; few expressed a preference for one generic formulation over the other. None of patients were able to switch back to the brand formulation, nor were any of them able to choose the generic that worked best for them. Insomnia, muscle pain, and gooseflesh skin were the most common withdrawal symptoms reported by the patients using the generics. Better outcomes were observed in patients who received a buprenorphine dose increase (2 mg) to suppress the withdrawal symptoms experienced while using the generics.

CONCLUSION

Our study serves as a reference to prescribers regarding approaches (eg, a small dose adjustment) that may potentially encourage OUD treatment adherence and even improve outcomes in patients who appear to be decompensating after the brand-to-generic switch.

Brand-to-Generic Substitution of Buprenorphine/Naloxone Sublingual Film in Puerto Rico: A Case Study

A 56-year-old patient with a 1-year history of stable maintenance treatment with Suboxone for opioid use disorder (OUD) was switched to a generic formulation in May of 2019. The patient reported experiencing-over the course of the following 3 months-withdrawal symptoms when switched to the Alvogen-produced generic formulation in May of 2019 and then to the Sandoz-produced version in July of that same year, she also was positive for fentanyl during that time. As a result, the buprenorphine dose was increased, and the patient was stable at this new dose using the generic versions. Blood levels pre- and post-change (not reported in previous case reports) showed maximum buprenorphine concentration being reached more quickly when the brand-name drug was used. Additionally, the area under the curve (AUC) values indicate that the generic formulation had higher exposures than the brand-name drug. Based on the clinical impact of the brand-to generic switch in this patient, further research in this area is warranted. In the meantime, clinicians should carefully monitor their patients so that, if warranted, dose adjustments can be made quickly and safely to minimize negatively impacting the OUD therapy outcomes of patients.

Efficacy of Rac and Cdc42 Inhibitor MBQ-167 in Triple-negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive form of breast cancer, with a high predisposition for locally invasive and metastatic cancer. With the objective to reduce cancer metastasis, we developed small molecule inhibitors to target the drivers of metastasis, the Rho GTPases Rac and Cdc42. Of these, MBQ-167 inhibits both Rac and Cdc42 with IC50s of 103 and 78 nmol/L, respectively; and consequently, inhibits p21-activated kinase (PAK) signaling, metastatic cancer cell proliferation, migration, and mammosphere growth; induces cell-cycle arrest and apoptosis; and decreases HER2-type mammary fatpad tumor growth and metastasis (Humphries-Bickley and colleagues, 2017). Herein, we used nuclear magnetic resonance to show that MBQ-167 directly interacts with Rac1 to displace specific amino acids, and consequently inhibits Rac.GTP loading and viability in TNBC cell lines. Phosphokinome arrays in the MDA-MB-231 human TNBC cells show that phosphorylation status of kinases independent of the Rac/Cdc42/PAK pathway are not significantly changed following 200 nmol/L MBQ-167 treatment. Western blotting shows that initial increases in phospho-c-Jun and phospho-CREB in response to MBQ-167 are not sustained with prolonged exposure, as also confirmed by a decrease in their transcriptional targets. MBQ-167 inhibits tumor growth, and spontaneous and experimental metastasis in immunocompromised (human TNBC) and immunocompetent (mouse TNBC) models. Moreover, per oral administration of MBQ-167 at 100 mg/kg body weight is not toxic to immunocompetent BALB/c mice and has a half-life of 4.6 hours in plasma. These results highlight the specificity, potency, and bioavailability of MBQ-167, and support its clinical potential as a TNBC therapeutic.

Machine Learning for Prediction of Stable Warfarin Dose in US Latinos and Latin Americans

Populations used to create warfarin dose prediction algorithms largely lacked participants reporting Hispanic or Latino ethnicity. While previous research suggests nonlinear modeling improves warfarin dose prediction, this research has mainly focused on populations with primarily European ancestry. We compare the accuracy of stable warfarin dose prediction using linear and nonlinear machine learning models in a large cohort enriched for US Latinos and Latin Americans (ULLA). Each model was tested using the same variables as published by the International Warfarin Pharmacogenetics Consortium (IWPC) and using an expanded set of variables including ethnicity and warfarin indication. We utilized a multiple linear regression model and three nonlinear regression models: Bayesian Additive Regression Trees, Multivariate Adaptive Regression Splines, and Support Vector Regression. We compared each model’s ability to predict stable warfarin dose within 20% of actual stable dose, confirming trained models in a 30% testing dataset with 100 rounds of resampling. In all patients (n = 7,030), inclusion of additional predictor variables led to a small but significant improvement in prediction of dose relative to the IWPC algorithm (47.8 versus 46.7% in IWPC, p = 1.43 × 10⁻¹⁵). Nonlinear models using IWPC variables did not significantly improve prediction of dose over the linear IWPC algorithm. In ULLA patients alone (n = 1,734), IWPC performed similarly to all other linear and nonlinear pharmacogenetic algorithms. Our results reinforce the validity of IWPC in a large, ethnically diverse population and suggest that additional variables that capture warfarin dose variability may improve warfarin dose prediction algorithms.

Pharmacogenomic polygenic risk score for clopidogrel responsiveness among Caribbean Hispanics: A candidate gene approach

This multicenter clinical study was aimed at conducting a targeted pharmacogenomic association analysis of residual on‐clopidogrel platelet reactivity in 474 Caribbean Hispanic patients. Platelet reactivity was measured using the VerifyNow P2Y12 assay and clopidogrel resistance was defined as P2Y12 reaction units (PRUs) greater than or equal to 208. Genotyping was performed using the whole‐genome Infinium MEGA BeadChip array. An ancestry‐adjusted, weighted polygenic risk score (wPGxRS) was developed to account for the effect of multiple variants on PRU and compared between clopidogrel responders and nonresponders. The mean PRU across the study cohort was 173.8 ± 68.5 and 33.5% of patients were defined as clopidogrel resistant. Multivariate linear regression showed that 19% of PRU variability was attributed to nine independent predictors, with CYP2C19*2 (rs4244285) accounting for ~ 7% of observed PRU variation (p < 0.001). PON1 rs662, ABCB1/MDR1 rs2032582, PEAR1 rs12041331 carrier status, and the interaction between African ancestry and rs12041331 carriers also predicted PRU among the participants (p ≤ 0.05). A clear gene‐dose effect was detected between PRU and CYP2C19*2 genotype, consistent with previous studies in European patient populations, as well as rs12777823. Importantly, a significant positive correlation was detected between our novel wPGxRS (4 variants) and PRU among the Hispanic patient population (r_p = 0.35, p < 0.001). Moreover, the wPGxRS discriminated between nonresponders and responders (p = 0.003), indicating that this multigene‐based score is a useful predictor of clopidogrel resistance among Caribbean Hispanics. Taken together, these results help close the gap of knowledge on clopidogrel pharmacogenomics and its potential clinical implementation in this under‐represented population.

Personalized health and the coronavirus vaccines-Do individual genetics matter?

Vaccines represent preventative interventions amenable to immunogenetic prediction of how human variability will influence their safety and efficacy. The genetic polymorphism among individuals within any population can render possible that the immunity elicited by a vaccine is variable in length and strength. The same immune challenge (virus and/or vaccine) could provoke partial, complete or even failed protection for some individuals treated under the same conditions. We review genetic variants and mechanistic relationships among chemokines, chemokine receptors, interleukins, interferons, interferon receptors, toll‐like receptors, histocompatibility antigens, various immunoglobulins and major histocompatibility complex antigens. These are the targets for variation among macrophages, dendritic cells, natural killer cells, T‐ and B‐lymphocytes, and complement. The technology platforms (mRNA, viral vectors, proteins) utilized to produce vaccines against SARS‐CoV‐2 infections may each trigger genetically distinct immune reactogenic profiles. With DNA biobanking and immunoprofiling of recipients, global COVID‐19 vaccinations could launch a new era of personalized healthcare.

PharmVar GeneFocus: CYP2C9

The Pharmacogene Variation Consortium (PharmVar) catalogues star (*) allele nomenclature for the polymorphic human CYP2C9 gene. Genetic variation within the CYP2C9 gene locus impacts the metabolism or bioactivation of many clinically important drugs, including nonsteroidal anti-inflammatory drugs, phenytoin, antidiabetic agents, and angiotensin receptor blockers. Variable CYP2C9 activity is of particular importance regarding efficacy and safety of warfarin and siponimod as indicated in their package inserts. This GeneFocus provides a comprehensive overview and summary of CYP2C9 and describes how haplotype information catalogued by PharmVar is utilized by the Pharmacogenomics Knowledgebase and the Clinical Pharmacogenetics Implementation Consortium.

Multi-site Investigation of Genetic Determinants of Warfarin Dose Variability in Latinos

We conducted a multi‐site investigation of genetic determinants of warfarin dose variability in Latinos from the U.S. and Brazil. Patients from four institutions in the United States (n = 411) and Brazil (n = 663) were genotyped for VKORC1 c.‐1639G> A, common CYP2C9 variants, CYP4F2*3, and NQO1*2. Multiple regression analysis was used in the U.S. cohort to test the association between warfarin dose and genotype, adjusting for clinical factors, with further testing in an independent cohort of Brazilians. In the U.S. cohort, VKORC1 and CYP2C9 variants were associated with lower warfarin dose (β = −0.29, P < 2.0 × 10⁻¹⁶; β = −0.21, P = 4.7 × 10⁻⁷, respectively) whereas CYP4F2 and NQO1 variants were associated with higher dose (β = 0.10, P = 2 × 10⁻⁴; β = 0.10, P = 0.01, respectively). Associations with VKORC1 (β = −0.14, P = 2.0 × 10⁻¹⁶), CYP2C9 (β = −0.07, P = 5.6 × 10⁻¹⁰), and CYP4F2 (β = 0.03, P = 3 × 10⁻³), but not NQO1*2 (β = 0.01, P = 0.30), were replicated in the Brazilians, explaining 43–46% of warfarin dose variability among the cohorts from the U.S. and Brazil, respectively. We identified genetic associations with warfarin dose requirements in the largest cohort of ancestrally diverse, warfarin‐treated Latinos from the United States and Brazil to date. We confirmed the association of variants in VKORC1, CYP2C9, and CYP4F2 with warfarin dose in Latinos from the United States and Brazil.

Assessment of the clinical utility of pharmacogenetic guidance in a comprehensive medication management service

INTRODUCTION

Pharmacists are poised to be the health care professionals best suited to provide medication-related consults and services based on a patient's genetics. Despite its potential benefits, the implementation of pharmacogenetic (PGx) testing into primary clinical settings has been slow among medically underserved populations. To our knowledge, this is the first time that PGx-driven recommendations have been incorporated into a Comprehensive Medication Management (CMM) service in a Hispanic population.

OBJECTIVES

The aim of this study is to evaluate the clinical utility of adding PGx guidance into pharmacist-driven CMM.

METHODS

This is a pre- and post-interventional design study. Patients were recruited from a psychologist's clinic. A total of 24 patients had a face-to-face interview with a pharmacist to complete a CMM, Personal Medication Record, and Medication-Related Action Plan (MAP) blind to PGx findings. Collected buccal DNA samples were genotyped using drug-metabolizing enzymes and transporters (DMET) Plus Array.

RESULTS

The pharmacist generated new MAPs for each patient based on PGx results. Genetic variants that could potentially affect the safety and effectiveness of at least one drug in the pharmacotherapy were identified in 96% of patients, for whom the pharmacist changed the initial recommendations. Polymorphisms in genes encoding for isoenzymes CYP2D6, CYP2C19, and CYP2C9 were identified in 83%, 52%, and 41% of patients, respectively. Pharmacists performing CMM identified 22 additional medication problems after PGx determinations. Moreover, they agreed with the clinical utility of PGx in the studied sample based on perceived value of adding PGx to traditional CMM and its utility in the decision-making process of pharmacists.

CONCLUSIONS

The study confirmed the critical role to be played by pharmacists in facilitating the clinical usage of relevant genetic information to optimize drug therapy decisions as well as their involvement on many levels of these multidisciplinary implementation efforts, including championing and leading PGx-guided CMM services.

Genotype-driven pharmacokinetic simulations of warfarin levels in Puerto Ricans

Objectives The inter-individual variability of warfarin dosing has been linked to genetic polymorphisms. This study was aimed at performing genotype-driven pharmacokinetic (PK) simulations to predict warfarin levels in Puerto Ricans. Methods Analysis of each individual dataset was performed by one-compartmental modeling using WinNonlin®v6.4. The k e of warfarin given a cytochrome P450 2C9 (CYP2C9) genotype ranged from 0.0189 to 0.0075 h-1. K a and V d parameters were taken from literature. Data from 128 subjects were divided into two groups (i.e., wild-types and carriers) and statistical analyses of PK parameters were performed by unpaired t-tests. Results In the carrier group (n=64), 53 subjects were single-carriers and 11 double-carriers (i.e., *2/*2, *2/*3, *2/*5, *3/*5, and *3/*8). The mean peak concentration (Cmax) was higher for wild-type (0.36±0.12 vs. 0.32±0.14 mg/L). Likewise, the average clearance (CL) parameter was faster among non-carriers (0.22±0.03 vs. 0.17±0.05 L/h; p=0.0001), with also lower area under the curve (AUC) when compared to carriers (20.43±6.97 vs. 24.78±11.26 h mg/L; p=0.025). Statistical analysis revealed a significant difference between groups with regard to AUC and CL, but not for Cmax. This can be explained by the variation of k e across different genotypes. Conclusions The results provided useful information for warfarin dosing predictions that take into consideration important individual PK and genotyping data.

Genotype-driven pharmacokinetic simulations of warfarin levels in Puerto Ricans

OBJECTIVES

The inter-individual variability of warfarin dosing has been linked to genetic polymorphisms. This study was aimed at performing genotype-driven pharmacokinetic (PK) simulations to predict warfarin levels in Puerto Ricans.

METHODS

Analysis of each individual dataset was performed by one-compartmental modeling using WinNonlin®v6.4. The k _e of warfarin given a cytochrome P450 2C9 (CYP2C9) genotype ranged from 0.0189 to 0.0075 h^-1. K _a and V _d parameters were taken from literature. Data from 128 subjects were divided into two groups (i.e., wild-types and carriers) and statistical analyses of PK parameters were performed by unpaired t-tests.

RESULTS

In the carrier group (n=64), 53 subjects were single-carriers and 11 double-carriers (i.e., *2/*2, *2/*3, *2/*5, *3/*5, and *3/*8). The mean peak concentration (Cmax) was higher for wild-type (0.36±0.12 vs. 0.32±0.14 mg/L). Likewise, the average clearance (CL) parameter was faster among non-carriers (0.22±0.03 vs. 0.17±0.05 L/h; p=0.0001), with also lower area under the curve (AUC) when compared to carriers (20.43±6.97 vs. 24.78±11.26 h mg/L; p=0.025). Statistical analysis revealed a significant difference between groups with regard to AUC and CL, but not for Cmax. This can be explained by the variation of k _e across different genotypes.

CONCLUSIONS

The results provided useful information for warfarin dosing predictions that take into consideration important individual PK and genotyping data.

Abstract 3020: Tumor pharmacokinetics of the metastatic cancer inhibitor MBQ-167 in mice

The Rho GTPases Rac and Cdc42 are potential targets against metastatic disease. Our group characterized the small molecule MBQ-167 as an effective dual Rac/Cdc42 inhibitor that reduces HER2 positive and triple negative tumor growth and metastasis in mice by ~90%. To continue validating this drug for FDA approval, we recently elucidated the plasma pharmacokinetics and the tissue distribution of MBQ-167 in mice (Maldonado et al., 2019). However, further studies are needed to characterize the tumor pharmacokinetics of MBQ-167 to determine drug exposure, time-to-peak, and the length of time that MBQ-167 remains in tumors after administration. The purpose of this study was to determine the tumor pharmacokinetics of MBQ-167 in a single dose input scheme (10 mg/kg BW) following intraperitoneal (IP) administration. Thirty-five female BALB/c mice (5 mice/group) were injected with 2.5 × 105 4T1 murine metastatic breast cancer cells at the mammary fat pad. After tumor establishment, a single dose of MBQ-167 (10 mg/kg BW) was administered via IP. Tumors were collected at 0.5, 1, 3, 6, 9,12, and 24 hours following drug administration. We used a validated bioanalytical method using supercritical fluid chromatography coupled with tandem mass spectrometry (SFC-MS/MS) to quantify MBQ-167 in tumors. Pharmacokinetic parameters were obtained by non-compartmental analysis using WinNolin® software. Pharmacokinetic analysis revealed that MBQ-167 has an elimination half-life (t1/2) of 8.64 hours in tumors, which is much longer than its half-life in plasma (2.17 hours), indicating preferential absorption and retention of this lipophilic small molecule in tumor tissues. The area under the curve (AUC0-t) was 4.39 %ID⋅hr/g with a maximum concentration (Cmax) of 1268.9 ng/g in tumors. Moreover, the time-to-peak concentration in tumors was 0.5 hours. Hence, this study supports the continued development of MBQ-167 as a potential anti-cancer therapeutic.

Citation Format: Maria Del Mar Maldonado, Ailed M. Cruz-Collazo, Luis D. Borrero-García, Gabriela T. Rosado-González, Jean F. Ruiz-Calderon, Jorge Duconge, Suranganie Dharmawardhane. Tumor pharmacokinetics of the metastatic cancer inhibitor MBQ-167 in mice [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3020.

Implementing a pharmacogenetic-driven algorithm to guide dual antiplatelet therapy (DAPT) in Caribbean Hispanics: protocol for a non-randomised clinical trial

INTRODUCTION

Minority populations in the USA are disproportionately affected by cardiovascular conditions. Reduced responsiveness to clopidogrel among carriers of CYP2C19 variants has been reported in patients with either coronary artery disease (CAD) or acute coronary syndrome (ACS) after the percutaneous coronary intervention (PCI). Previous studies have evaluated CYP2C19 genotyping-guided antiplatelet therapy in selected populations; however, this has yet to be tested among Hispanics. Given the paucity of clinical research on CYP2C19 and antiplatelet clinical outcomes in Hispanics, our study will test the safety and efficacy of a genetic-driven treatment algorithm to guide dual antiplatelet therapy (DAPT) in Caribbean Hispanics.

METHODS AND ANALYSIS

This is a multicentre, prospective, non-randomised clinical trial that proposes an assessment of pharmacogenomic-guided DAPT in post-PCI Caribbean Hispanic patients with ACS or CAD. We will recruit 250 patients to be compared with a matched non-concurrent cohort of 250 clopidogrel-treated patients (standard-of-care). Major adverse cardiovascular events (MACEs) such as all-cause death, myocardial infarction (MI), stroke, coronary revascularisation, stent thrombosis and bleedings over 6 months will be the study endpoints. Among the recruited, high-risk patients will be escalated to ticagrelor and low-risk patients will remain on clopidogrel. The primary objective is to determine whether genetic-guided therapy is superior to standard of care. The secondary objective will determine if clopidogrel treatment in low-risk patients is not associated with a higher rate of MACEs compared with escalated antiplatelet therapy in high-risk patients. Patients will be enrolled up to the group's completion.

ETHICS AND DISSEMINATION

Approval was obtained from the Institutional Review Board of the University of Puerto Rico Medical Sciences Campus (protocol # A4070417). The study will be carried out in compliance with the Declaration of Helsinki and International Conference on Harmonization Good Clinical Practice Guidelines. Findings will be published in a peer-reviewed journal and controlled access to experimental data will be available.

TRIAL REGISTRATION NUMBER

NCT03419325; Pre-results.

A review of the pharmacogenomics of buprenorphine for the treatment of opioid use disorder

As the opioid epidemic continues to grow across the United States, the number of patients requiring treatment for opioid use disorder continues to climb. Although medication-assisted treatment presents a highly effective tool that can help address this epidemic, its use has been limited. Nonetheless, with easier dosing protocols (compared to the more complex dosing required of methadone due to its long and variable half-life) and fewer prescribing limitations (may be prescribed outside the setting of federally approved clinics), the increase in buprenorphine use in the United States has been dramatic in recent years. Despite buprenorphine's demonstrated efficacy, patient-specific factors can alter the response to the medications, which may lead to treatment failure in some patients. Clinical characteristics (sex, concurrent medications, and mental health comorbidities) as well as social determinants of health (housing status, involvement with the criminal justice system, and socioeconomic status) may impact treatment outcomes. Furthermore, a growing body of data suggests that genetic variations can alter pharmacological effects and influence therapeutic response. This review will cover the available pharmacogenomic data for the use of buprenorphine in the management of opioid use disorders. Pharmacogenomic determinants that affect opioid receptors, the dopaminergic system, metabolism of buprenorphine, and adverse events are discussed. Although much of the existing data comes from observational studies, clinical research is ongoing. Nevertheless, the development of pharmacogenomic-guided strategies has the potential to reduce opioid misuse, improve clinical outcomes, and save healthcare resources.

PharmVar GeneFocus: CYP2C19

The Pharmacogene Variation Consortium (PharmVar) catalogues star (*) allele nomenclature for the polymorphic human CYP2C19 gene. CYP2C19 genetic variation impacts the metabolism of many drugs and has been associated with both efficacy and safety issues for several commonly prescribed medications. This GeneFocus provides a comprehensive overview and summary of CYP2C19 and describes how haplotype information catalogued by PharmVar is utilized by the Pharmacogenomics Knowledgebase and the Clinical Pharmacogenetics Implementation Consortium (CPIC).

Genetic Factors Influencing Warfarin Dose in Black-African Patients: A Systematic Review and Meta-Analysis

Warfarin is the most commonly used oral anticoagulant in sub-Saharan Africa. Dosing is challenging due to a narrow therapeutic index and high interindividual variability in dose requirements. To evaluate the genetic factors affecting warfarin dosing in black-Africans, we performed a meta-analysis of 48 studies (2,336 patients). Significant predictors for CYP2C9 and stable dose included rs1799853 (CYP2C9*2), rs1057910 (CYP2C9*3), rs28371686 (CYP2C9*5), rs9332131 (CYP2C9*6), and rs28371685 (CYP2C9*11) reducing dose by 6.8, 12.5, 13.4, 8.1, and 5.3 mg/week, respectively. VKORC1 variants rs9923231 (-1639G>A), rs9934438 (1173C>T), rs2359612 (2255C>T), rs8050894 (1542G>C), and rs2884737 (497T>G) decreased dose by 18.1, 21.6, 17.3, 11.7, and 19.6 mg/week, respectively, whereas rs7294 (3730G>A) increased dose by 6.9 mg/week. Finally, rs12777823 (CYP2C gene cluster) was associated with a dose reduction of 12.7 mg/week. Few studies were conducted in Africa, and patient numbers were small, highlighting the need for further work in black-Africans to evaluate genetic factors determining warfarin response.

Machine Learning Algorithm for Predicting Warfarin Dose in Caribbean Hispanics Using Pharmacogenetic Data

Despite some previous examples of successful application to the field of pharmacogenomics, the utility of machine learning (ML) techniques for warfarin dose predictions in Caribbean Hispanic patients has yet to be fully evaluated. This study compares seven ML methods to predict warfarin dosing in Caribbean Hispanics. This is a secondary analysis of genetic and non-genetic clinical data from 190 cardiovascular Hispanic patients. Seven ML algorithms were applied to the data. Data was divided into 80 and 20% to be used as training and test sets. ML algorithms were trained with the training set to obtain the models. Model performance was determined by computing the corresponding mean absolute error (MAE) and % patients whose predicted optimal dose were within ±20% of the actual stabilization dose, and then compared between groups of patients with “normal” (i.e., > 21 but <49 mg/week), low (i.e., ≤21 mg/week, “sensitive”), and high (i.e., ≥49 mg/week, “resistant”) dose requirements. Random forest regression (RFR) significantly outperform all other methods, with a MAE of 4.73 mg/week and 80.56% of cases within ±20% of the actual stabilization dose. Among those with “normal” dose requirements, RFR performance is also better than the rest of models (MAE = 2.91 mg/week). In the “sensitive” group, support vector regression (SVR) shows superiority over the others with lower MAE of 4.79 mg/week. Finally, multivariate adaptive splines (MARS) shows the best performance in the resistant group (MAE = 7.22 mg/week) and 66.7% of predictions within ±20%. Models generated by using RFR, MARS, and SVR algorithms showed significantly better predictions of weekly warfarin dosing in the studied cohorts than other algorithms. Better performance of the ML models for patients with “normal,” “sensitive,” and “resistant” to warfarin were obtained when compared to other populations and previous statistical models.

Pharmacokinetics of the Rac/Cdc42 Inhibitor MBQ-167 in Mice by Supercritical Fluid Chromatography-Tandem Mass Spectrometry

The Rho GTPases Rac and Cdc42 are potential targets against metastatic diseases. We characterized the small molecule MBQ-167 as an effective dual Rac/Cdc42 inhibitor that reduces HER2-type tumor growth and metastasis in mice by ∼90%. This study reports the pharmacokinetics and tissue distribution of MBQ-167 following intraperitoneal and oral single-dose administrations. We first developed and validated a bioanalytical method for the quantitation of MBQ-167 in mouse plasma and tissues by supercritical fluid chromatography coupled with electrospray ionization tandem mass spectrometry. MBQ-167 was rapidly distributed into the kidneys after intraperitoneal dosing, whereas oral administration resulted in higher distribution to lungs. The elimination half-lives were 2.17 and 2.6 h for the intraperitoneal and oral dosing, respectively. The relative bioavailability of MBQ-167 after oral administration was 35%. This investigation presents the first analysis of the pharmacokinetics of MBQ-167 and supports further preclinical evaluation of this drug as a potential anticancer therapeutic.

Low-frequency variants at the CYP2C9 locus among Puerto Rican patients on warfarin: in silico predictions of functionality and conservation

Aim: Perform in silico predictions of functional consequences of CYP2C9 variants identified by next-generation sequencing in Puerto Ricans. Methods: Identified low-frequency CYP2C9 variants (minor allele frequencies <2%) were evaluated using the Combined Annotation-Dependent Depletion (CADD v1.3) tools and molecular modeling/docking analysis to predict impact on CYP2C9 activity. Results: CYP2C9*5,*8,*9,*11,*12,*21 and a novel *61 induce conformational changes that affect the binding site of S-warfarin. Most of these deleterious variants occur at higher frequency among individuals with large African ancestry. Conclusion: The unfavorable distance of S-warfarin from heme group, and low-binding interactions due to these CYP2C9 variants, suggest major complications during warfarin therapy. This study contributes to the field by predicting functional alterations of rare CYP2C9 variants for the first time in Hispanics.

Ethnogeographic prevalence and implications of the 677C>T and 1298A>C MTHFR polymorphisms in US primary care populations

Aim: Variants of the MTHFR gene have been associated with a wide range of diseases. Materials & methods: The present study analyzed data from clinical genotyping of MTHFR 677C>T and 1298A>C in 1405 patients in urban primary care settings. Results: Striking differences in ethnogeographic frequencies of MTHFR polymorphisms were observed. African-Americans appear to be protected from MTHFR deficiency. Hispanics and Caucasians may be at elevated risk due to increased frequencies of 677C>T and 1298A>C, respectively. Conclusion: Individuals carrying mutations for both genes were rare and doubly homozygous mutants were absent, suggesting the TTcc is extremely rare in the greater population. The results suggest multilocus MTHFR genotyping may yield deeper insight into the ethnogeographic association between MTHFR variants and disease.

Solubility Determination and Correlation of Warfarin Sodium 2‑Propanol Solvate in Pure, Binary, and Ternary Solvent Mixtures

The solubility of warfarin sodium isopropanol solvate (WS·IPA), a widely used anticoagulant, was determined at temperatures ranging from 278.15 to 333.15 K in four pure solvents (acetone, ethanol, IPA, and water), five binary solvent mixtures (IPA + acetone, IPA + ethanol, IPA + water, IPA + heptane, and IPA + hexane), and five ternary solvent mixtures (IPA + acetone + heptane, IPA + acetone + hexane, IPA + ethanol + heptane, IPA + ethanol + hexane, and IPA + water + heptane) using the polythermal method. It was demonstrated that the solubility of WS·IPA increases with increasing temperature in the pure solvents and at constant solvent composition in the solvent mixtures. In addition, the solubility of WS·IPA in IPA increases with increasing content of acetone, ethanol, and water, which act as cosolvents, and decreases with increasing content of heptane and hexane, which act as antisolvents. The experimental solubility data of WS·IPA in pure solvents and binary and ternary solvent mixtures were correlated using the modified Apelblat and λh model equations. The correlated solubility data agree with the experimental data based on the relative deviation and the average relative deviation (ARD %) values. Thus, the correlated and experimentally derived solubility data of WS·IPA provide a pathway to engineer advanced pharmaceutical crystallization processes for WS·IPA.

Prevalence of pharmacogenomic variants affecting the efficacy of clopidogrel therapy in the Hispanic Community Health Study/Study of Latinos cohort

PURPOSE

Although clopidogrel is the most widely used oral P2Y12 receptor antagonist, up to 10% of acute coronary syndrome patients treated with clopidogrel will experience a recurrent myocardial infarction and 2-3% will experience stent thrombosis within 1 year. The purpose of this research is to describe the prevalence of pharmacogene variants associated with clopidogrel responsiveness (CYP2C19, B4GALT2, ABCB1, PON1, CES1 and P2RY12) in Hispanic/Latino patients of diverse backgrounds.

METHODS

Minor allele frequencies of nine variants from participants of Hispanic Community Health Study/Study of Latinos were compared between subpopulations as well as to continental ancestry references using z-test for independent proportions.

RESULTS

MAFs for six out of nine variants differed between Caribbean and Mainland subpopulations (p < 0.05). Compared with European reference group, MAFs of ABCB1, CES1 and PON1 were higher in Hispanic Community Health Study/Study of Latinos, whereas B4GALT2 and CYP2C19*2 and *17 were lower.

CONCLUSION

Significant differences in the prevalence of most pharmacogenomic variants related to clopidogrel response provide a foundation to better inform ongoing and future clinical studies of clopidogrel pharmacogenetics in the US Hispanic/Latino populations.

Abstract 4923: Pharmacokinetics of the metastatic cancer inhibitor MBQ-167 in mice

Metastasis is the principal cause of death for most cancer patients; however, effective treatment options are limited. The Rho GTPases Rac and Cdc42 are critical regulators of cancer cell migration and invasion; processes required for metastatic progression. Hence, targeting of these pivotal regulators is a rational approach for novel metastasis focused therapy design. We previously characterized the small molecule MBQ-167 as a novel Rac/Cdc42 inhibitor that inhibits mammary tumor growth and metastasis in immunocompromised mice by ~90%, which is ten times more potent than other currently available Rac inhibitors (Humphries-Bickley, et al., 2017). However, further studies are needed to determine the pharmacokinetic (PK) parameters of MBQ-167 in rodents to understand the mechanisms of drug distribution and elimination of this compound. The purpose of this study was to determine the pharmacokinetics and bioavailability of MBQ-167 in a single dose input scheme (10 mg/kg BW) following intraperitoneal (IP) and oral gavage (PO) administration. The drug was administered to BALB/c mice (4 mice/group) and plasma was collected at 0.5, 1, 3, 6, 9, and 12 hours after IP or PO administration. We developed and validated a bioanalytical method using supercritical fluid chromatography (SFC) coupled with electrospray ionization tandem mass spectrometry (MS/MS) for the detection of MBQ-167 in plasma. SFC-MS/MS was selected because it uses supercritical carbon dioxide (SCO2) as the mobile phase and offers advantages such as high sensitivity, increased resolution, and rapid analysis times. Pharmacokinetic parameters were obtained by mono-compartmental and bi-compartmental analysis for IP and PO dosing respectively using WinNolin® software, Version 7.0. Preliminary pharmacokinetic analysis revealed that the area under the curve (AUC0-∞) was 749 ng·hr/mL and 255 ng·hr/mL for IP and PO dosing respectively. The elimination half-life (t1/2) was 2.4 hours for IP dosing and the mean residence time (MRT) was 3.4 hours and 2.3 hours for the IP and PO dosing respectively. The maximum plasma drug concentration (Cmax) was 220 ng/mL after IP administration, compared to 127 ng/mL following PO administration. Furthermore, the time-to-peak for both administration routes was 30 minutes. The relative bioavailability of MBQ-167 after oral gavage administration was 34%. This study presents the first analysis of the pharmacokinetics of the Rac/Cdc42 inhibitor MBQ-167 in mice and it supports the continued development of this drug as a potential anti-cancer therapeutic.

Citation Format: Maria del Mar Maldonado, Linette Castillo-Pichardo, Joseph Bloom, Jorge Duconge, Jose F. Rodriguez-Orengo, Eliud Hernandez-O'Farrill, Cornelis Vlaar, Suranganie Dharmawardhane. Pharmacokinetics of the metastatic cancer inhibitor MBQ-167 in mice [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 4923.

Pharmacogenetic association study on clopidogrel response in Puerto Rican Hispanics with cardiovascular disease: a novel characterization of a Caribbean population

Introduction

High on-treatment platelet reactivity (HTPR) to clopidogrel imparts an increased risk for ischemic events in adults with coronary artery disease. Platelet reactivity varies with ethnicity and is influenced by both clinical and genetic variables; however, no clopidogrel pharmacogenetic studies with Puerto Rican patients have been reported. Therefore, we sought to identify clinical and genetic determinants of on-treatment platelet reactivity in a cohort of Puerto Rican patients with cardiovascular disease.

Methods

We performed a retrospective study of 111 patients on 75 mg/day maintenance dose of clopidogrel. Patients were allocated into 2 groups: Group I, without HTPR; and Group II, with HTPR. Platelet function was measured ex vivo using the VerifyNow® P2Y12 assay and HTPR was defined as P2Y12 reaction units (PRU) ≥230. Genotyping testing was performed using Taqman^® Genotyping Assays.

Results

The mean PRU across the cohort was 203±61 PRU (range 8–324), and 42 (38%) patients had HTPR. Multiple logistic regression showed that 27% of the total variation in PRU was explained by a history of diabetes mellitus, hematocrit, CYP2C19*2, and PON1 p.Q192R. Body mass index (odds ratio [OR]=1.15; 95% CI: 1.03–1.27), diabetes mellitus (OR=3.46; 95% CI: 1.05–11.43), hematocrit (OR=0.75; 95% CI: 0.65–0.87), and CYP2C19*2 (OR=4.44; 95% CI: 1.21–16.20) were the only independent predictors of HTPR.

Conclusion

Moreover, we propose a predictive model to determine PRU values as measured by VerifyNow P2Y12 assay for the Puerto Rican Hispanic population. This model has the potential to identify Hispanic patients at higher risk for adverse events on clopidogrel.

Clinical Relevant Polymorphisms Affecting Clopidogrel Pharmacokinetics and Pharmacodynamics: Insights from the Puerto Rico Newborn Screening Program

Background: Variations in several clopidogrel-pharmacogenes have been linked to clopidogrel response variability and clinical outcomes. We aimed to determine the frequency distribution of major polymorphisms on CYP2C19, PON1, ABCB1 and P2RY12 pharmacogenes in Puerto Ricans. Methods: This was a cross-sectional, population-based study of 200 unrelated "Guthrie" cards specimens from newborns registered in the Puerto Rican newborn screening program (PRNSP) between 2004 and 2014. Taqman® SNP assay techniques were used for genotyping. Results: Minor allele frequencies (MAF) were 46% for PON1 (rs662), 41% for ABCB1 (rs1045642), 14% for CYP2C19*17, 13% for CYP2C19*2, 12% for P2RY12-H2 and 0.3% for CYP2C19*4. No carriers of the CYP2C19*3 variants were detected. All alleles and genotype proportions were found to be in Hardy⁻Weinberg equilibrium (HWE). Overall, there were no significant differences between MAFs of these variants in Puerto Ricans and the general population (n = 453) of the 1000 Genome project, except when comparisons to each individual parental group were performed (i.e., Africans, Europeans and East-Asians; p < 0.05). As expected, the prevalence of these markers in Puerto Ricans most resembled those in the 181 subjects from reference populations of the Americas. Conclusions: These prevalence data provide a necessary groundwork for future clinical studies of clopidogrel pharmacogenetics in Caribbean Hispanics.

A comparative pharmacokinetic and pharmacodynamic study of two novel Cuban PEGylated rHuEPO versus MIRCERA® and ior®EPOCIM

CONTEXT

The recombinant human erythropoietin (rHuEPO) stimulates the erythropoiesis process. Because this glycoprotein has a short half-life, it needs to be administrated two to three times a week. One of the technics to solve this issue is the PEGgilation.

AIMS

To evaluate the pharmacokinetics (PK) and pharmacodynamics of two new branched PEGylated erythropoietins (i.e., an asymmetric 32 kDa-PEG₂-rHuEPO and a symmetric 40 kDa-PEG₂-rHuEPO molecule) compared to non-PEGylated ior^®EPOCIM and MIRCERA^®.

METHODS

Serum concentrations of both PEGylated and non-PEGylated erythropoietins were measured at various time points in order to determine PK parameters using non-compartmental analysis approach. The reticulocyte (%), erythrocyte count and hemoglobin levels were ascertained in order to compare the effect of these molecules after administrating a single intravenous dose (10 μg/kg) of each product in male New Zealand rabbits.

RESULTS

Both branched PEGylated erythropoietin forms exhibited half-lives that were significantly longer than ior^®EPOCIM (p<0.05), but not statistically different to MIRCERA^®. The mean elimination half-life increased from 4 h (ior^®EPOCIM) to 131 h for the 32 kDa-PEG₂-rHuEPO and 119 h for the 40 kDa-PEG₂-rHuEPO. Conversely, MIRCERA^® exhibits a half-life of 64 h. Both PEGylated erythropoietin products significantly enhanced the stimulating effect on reticulocytes and erythrocytes formation, as well as on hemoglobin levels, when compared to ior^®EPOCIM treatment up to 42 days post-dose.

CONCLUSIONS

The PEGylation strategy employed in this study is an effective method to modify the pharmacokinetics and pharmacodynamics of rHuEPO molecule achieving higher half-lives and, therefore, longer in vivo bioactivity. Both of the branched PEGylated-EPO forms tested are promising candidates for human testing.

Potential Usefulness of Clopidogrel Pharmacogenetics in Cerebral Endovascular Procedures and Carotid Artery Stenting

BACKGROUND

Previous reports have shown inadequate response to dual antiplatelet therapy (DAPT) with aspirin and clopidogrel in 5-30% of patients undergoing percutaneous coronary interventions (PCI), due mostly to clopidogrel resistance. This prevalence increases up to 66% in patients undergoing neurointerventional procedures. However, clinical significance of CYP2C19 genotypes in neurointerventional procedures or carotid artery stenting (CAS) is unknown.

OBJECTIVE

The purpose of this review is to update our current knowledge and understanding of the pharmacogenetic basis for poor clopidogrel responsiveness in patients undergoing CAS and endovascular interventions as well as to explore usefulness of genotyping to reduce the rate of procedure-related thrombosis that results in ischemic complications.

METHOD

A literature search for pharmacogenetic studies in cerebral endovascular interventions and CAS was conducted on three databases using a list of the most relevant pharmacogenetic biomarkers.

RESULTS

The review included 7 papers involving 3 genetic polymorphisms on CYP2C19 and 442 subjects. Patients harboring at least one loss-of-function CYP2C19 polymorphism (e.g., CYP2C19*2 and *3) are at an increased risk of thromboembolic complications such as stent thrombosis following neurointerventional procedures. Notably, patients who carry the gain-of-function CYP2C19*17 allele may have increased risk of ischemic events following endovascular treatment, independent of clopidogrel responsiveness.

CONCLUSION

Studies assessing the influence of CYP2C19 polymorphisms on high on-treatment platelet reactivity in CAS and cerebrovascular disease patients are still limited and need further validation in large multicenter studies. This review covers an important topic in the field of antiplatelet therapy for cerebral endovascular procedures and CAS.

Effect of cilostazol on platelet reactivity among patients with peripheral artery disease on clopidogrel therapy

BACKGROUND

Antiplatelet therapy with clopidogrel is recommended to reduce cardiovascular events in patients with peripheral artery disease (PAD); however, clopidogrel efficacy has not been adequately studied in this patient population. Therefore, we aimed to determine the effects of cilostazol therapy on platelet reactivity among PAD patients on clopidogrel.

METHODS

We performed a cross-sectional pilot study of 46 Puerto Rican patients diagnosed with PAD. The cohort was divided based on use of clopidogrel and cilostazol (n=24) or clopidogrel alone (n=22). Platelet function was measured ex vivo using the VerifyNow P2Y12 assay. Genomic DNA was extracted from peripheral blood samples using the QIAamp DNA Blood Midi Kit, which was subjected to candidate variant genotyping (CYP2C19, ABCB1, PON1 and P2RY12) using TaqMan quantitative polymerase chain reaction assays. All analyses were performed using SAS version 9.4 (SAS Institute).

RESULTS

Among all enrolled patients, 18 (39%) had high on-treatment platelet reactivity (HTPR). The mean platelet reactivity was 207±53 (range, 78-325) with higher P2Y12 reaction units in the non-cilostazol group, 224±45 vs. 191±55 on the cilostazol group (p=0.03). No significant differences were observed in the clinical or genetic variables between the two groups. A multiple regression analysis determined that history of diabetes mellitus (p=0.03), use of cilostazol (p=0.03) and hematocrit (p=0.02) were independent predictors of platelet reactivity.

CONCLUSIONS

In Puerto Rican PAD patients on clopidogrel therapy, history of diabetes mellitus, use of cilostazol and hematocrit are independent predictors of platelet reactivity. Adjunctive cilostazol therapy may enhance clopidogrel efficacy among PAD patients with HTPR.

Role of treatment-modifying MTHFR677C>T and 1298A>C polymorphisms in metformin-treated Puerto Rican patients with type-2 diabetes mellitus and peripheral neuropathy

BACKGROUND

The study was conducted to investigate potential association between MTHFR genotypes and diabetic peripheral neuropathy (DPN) in Puerto Ricans with type-2 diabetes mellitus (T2DM) treated with metformin. The prevalence of major MTHFR polymorphisms in this cohort was also ascertained.

METHODS

DNAs from 89 metformin-treated patients with T2DM and DPN were genotyped using the PCR-based RFLP assay for MTHFR677C>T and 1298A>C polymorphisms. Frequency distributions of these variants in the study cohort were compared to those reported for three reference populations (HapMap project) and controls (400 newborn specimens). Chi-square (or Fischer's exact) tests and odds ratios (OR) were used to assess association with DPN susceptibility risk (patients vs. controls) and biochemical markers (wild types vs. carriers).

RESULTS

Sixty-seven percent (67%) of participants carry at least one of these MTHFR polymorphisms. No deviations from Hardy-Weinberg equilibrium were detected. The genotype and allele frequencies showed statistically significant differences between participants and controls (p<0.0001 and p=0.03, respectively). Results suggest that 1298A>C but not 677C>T is associated with DPN susceptibility in this cohort (p=0.018). Different patterns of allelic dissimilarities are observed when comparing our cohort vs. the three parental ancestries. After sorting individuals by their carrier status, no significant associations were observed between these genetic variants (independently or combined) and any of the biochemical markers (HbA1c, folate, vitamin B12, homocysteine).

CONCLUSIONS

Prevalence of major MTHFR variants in Puerto Rican patients with T2DM is first time ever reported. The study provides further evidence on the use of this genetic marker as an independent risk factor for DPN.

Clinical determinants of clopidogrel responsiveness in a heterogeneous cohort of Puerto Rican Hispanics

BACKGROUND

Clopidogrel is by far the most prescribed platelet adenosine diphosphate (ADP) antagonist in Puerto Rico despite the advent of newer agents (prasugrel and ticagrelor). Given the paucity of data on clopidogrel responsiveness in Hispanics, we sought to determine the association between clinical characteristics and platelet reactivity in Puerto Rican patients on clopidogrel therapy.

STUDY POPULATION

A total of 100 Puerto Rican patients on clopidogrel therapy were enrolled and allocated into two groups: Group I, without high on-treatment platelet reactivity (HTPR); and Group II, with HTPR. Platelet function was measured ex vivo using the VerifyNow® P2Y12 assay.

RESULTS

The cohort was comprised of Hispanic patients with coronary artery disease (57%), peripheral artery disease (32%), carotid artery stenosis (7%), cerebral artery aneurysm (2%), and stroke (2%). Mean platelet reactivity was 200 ± 61 P2Y12 reaction units (PRUs) (range: 8-324), and 35% of patients had HTPR (PRUs ⩾ 230). Multivariable logistic regression analysis determined that diabetes mellitus (DM) [odds ratio (OR) = 3.27; 95% confidence interval (CI): 1.20-8.96], use of proton-pump inhibitors (PPIs) (OR = 3.60; 95% CI: 1.09-11.82), and calcium channel blockers (CCBs) (OR = 3.10; 95% CI: 1.09-8.83) were independent predictors of HTPR ( p < 0.05) after adjusting for other clinical variables.

CONCLUSIONS

In a sample of 100 Puerto Rican Hispanic patients on clopidogrel, 35% had HTPR. Furthermore, DM, PPIs and CCBs predicted HTPR. Clinical outcome data are needed to identify appropriate PRU thresholds for risk prediction in the Puerto Rican population.

Potential of a Pharmacogenetic-Guided Algorithm to Predict Optimal Warfarin Dosing in a High-Risk Hispanic Patient: Role of a Novel NQO1*2 Polymorphism

Deep abdominal vein thrombosis is extremely rare among thrombotic events secondary to the use of contraceptives. A case to illustrate the clinical utility of ethno-specific pharmacogenetic testing in warfarin management of a Hispanic patient is reported. A 37-year-old Hispanic Puerto Rican, non-gravid female with past medical history of abnormal uterine bleeding on hormonal contraceptive therapy was evaluated for abdominal pain. Physical exam was remarkable for unspecific diffuse abdominal tenderness, and general initial laboratory results-including coagulation parameters-were unremarkable. A contrast-enhanced computed tomography showed a massive thrombosis of the main portal, splenic, and superior mesenteric veins. On admission the patient was started on oral anticoagulation therapy with warfarin at 5 mg/day and low-molecular-weight heparin. The prediction of an effective warfarin dose of 7.5 mg/day, estimated by using a recently developed pharmacogenetic-guided algorithm for Caribbean Hispanics, coincided with the actual patient's warfarin dose to reach the international normalized ratio target. We speculate that the slow rise in patient's international normalized ratio observed on the initiation of warfarin therapy, the resulting high risk for thromboembolic events, and the required warfarin dose of 7.5 mg/day are attributable in some part to the presence of the NQO1*2 (g.559C>T, p.P187S) polymorphism, which seems to be significantly associated with resistance to warfarin in Hispanics. By adding genotyping results of this novel variant, the predictive model can inform clinicians better about the optimal warfarin dose in Caribbean Hispanics. The results highlight the potential for pharmacogenetic testing of warfarin to improve patient care.

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.

Pharmacogenetics of healthy volunteers in Puerto Rico

Puerto Ricans are a unique Hispanic population with European, Native American (Taino), and higher West African ancestral contributions than other non-Caribbean Hispanics. In admixed populations, such as Puerto Ricans, genetic variants can be found at different frequencies when compared to parental populations and uniquely combined and distributed. Therefore, in this review, we aimed to collect data from studies conducted in healthy Puerto Ricans and to report the frequencies of genetic polymorphisms with major relevance in drug response. Filtering for healthy volunteers or individuals, we performed a search of pharmacogenetic studies in academic literature databases without limiting the period of the results. The search was limited to Puerto Ricans living in the island, excluding those studies performed in mainland (United States). We found that the genetic markers impacting pharmacological therapy in the areas of cardiovascular, oncology, and neurology are the most frequently investigated. Coincidently, the top causes of mortality in the island are cardiovascular diseases, cancer, diabetes, Alzheimer's disease, and stroke. In addition, polymorphisms in genes that encode for members of the CYP450 family (CYP2C9, CYP2C19, and CYP2D6) are also available due to their relevance in the metabolism of drugs. The complex genetic background of Puerto Ricans is responsible for the divergence in the reported allele frequencies when compared to parental populations (Africans, East Asians, and Europeans). The importance of reporting the findings of pharmacogenetic studies conducted in Puerto Ricans is to identify genetic variants with potential utility among this genetically complex population and eventually move forward the adoption of personalized medicine in the island.

Pharmacogenetics of drug-metabolizing enzymes in US Hispanics

Although the Hispanic population is continuously growing in the United States, they are underrepresented in pharmacogenetic studies. This review addresses the need for compiling available pharmacogenetic data in US Hispanics, discussing the prevalence of clinically relevant polymorphisms in pharmacogenes encoding for drug-metabolizing enzymes. CYP3A5*3 (0.245-0.867) showed the largest frequency in a US Hispanic population. A higher prevalence of CYP2C9*3, CYP2C19*4, and UGT2B7 IVS1+985 A>G was observed in US Hispanic vs. non-Hispanic populations. We found interethnic and intraethnic variability in frequencies of genetic polymorphisms for metabolizing enzymes, which highlights the need to define the ancestries of participants in pharmacogenetic studies. New approaches should be integrated in experimental designs to gain knowledge about the clinical relevance of the unique combination of genetic variants occurring in this admixed population. Ethnic subgroups in the US Hispanic population may harbor variants that might be part of multiple causative loci or in linkage-disequilibrium with functional variants. Pharmacogenetic studies in Hispanics should not be limited to ascertain commonly studied polymorphisms that were originally identified in their parental populations. The success of the Personalized Medicine paradigm will depend on recognizing genetic diversity between and within US Hispanics and the uniqueness of their genetic backgrounds.