Showing papers by "Richard B. Kim published in 2021"

Impact of pretreatment dihydropyrimidine dehydrogenase genotype-guided fluoropyrimidine dosing on chemotherapy associated adverse events

Abstract: Consensus guidelines exist for genotype-guided fluoropyrimidine dosing based on variation in the gene dihydropyrimidine dehydrogenase (DPYD). However, these guidelines have not been widely implemented in North America and most studies of pretreatment DPYD screening have been conducted in Europe. Given regional differences in treatment practices and rates of adverse events (AEs), we investigated the impact of pretreatment DPYD genotyping on AEs in a Canadian context. Patients referred for DPYD genotyping prior to fluoropyrimidine treatment were enrolled from December 2013 through November 2019 and followed until completion of fluoropyrimidine treatment. Patients were genotyped for DPYD c.1905+1G>A, c.2846A>T, c.1679T>G, and c.1236G>A. Genotype-guided dosing recommendations were informed by Clinical Pharmacogenetics Implementation Consortium guidelines. The primary outcome was the proportion of patients who experienced a severe fluoropyrimidine-related AE (grade ≥3, Common Terminology Criteria for Adverse Events version 5.0). Secondary outcomes included early severe AEs, severe AEs by toxicity category, discontinuation of fluoropyrimidine treatment due to AEs, and fluoropyrimidine-related death. Among 1394 patients, mean (SD) age was 64 (12) years, 764 (54.8%) were men, and 47 (3.4%) were DPYD variant carriers treated with dose reduction. Eleven variant carriers (23%) and 418 (31.0%) noncarriers experienced a severe fluoropyrimidine-related AE (p = 0.265). Six carriers (15%) and 284 noncarriers (21.1%) experienced early severe fluoropyrimidine-related AEs (p = 0.167). DPYD variant carriers treated with genotype-guided dosing did not experience an increased risk for severe AEs. Our data support a role for DPYD genotyping in the use of fluoropyrimidines in North America.

High infliximab trough concentrations are associated with sustained histologic remission in inflammatory bowel disease: a prospective cohort study.

Abstract: The threshold concentration of infliximab during maintenance therapy has not been well-defined in relation to histologic remission. The aim of the study is to dentify the maintenance-phase infliximab concentration associated with histologic remission in inflammatory bowel disease patients (IBD). A prospective cohort study was carried out in 104 IBD patients seen at a tertiary care centre in London, Canada. Infliximab trough concentrations were collected during the maintenance phase of treatment and compared between participants with and without evidence of histologic remission. Participants were additionally evaluated for sustained histologic remission, and relapse to active disease. Participants in histologic remission attained higher mean concentrations of infliximab during the maintenance phase (10.34 ± 0.69 μg/ml) compared to those with persistent disease activity (6.23 ± 0.67 μg/ml, p-value < 0.0001). Additionally, during the maintenance phase, sustained histologic remission was also associated with a higher mean concentration of infliximab (10.81 ± 5.46 μg/ml) compared to those who relapsed to active disease (5.68 ± 3.70, p < 0.001). Overall, participants with a mean infliximab trough concentration greater than 8ug/ml were more likely to have histologic remission (area under the receiver operating characteristic curve, AUROC = 0.72, 95%CI = 0.65–0.84, p < 0.0001) and sustained histologic remission (AUC = 0.77, 95%CI = 0.63–0.91, p = 0.002). Maintenance-phase infliximab trough concentrations greater than 8 μg/ml, which is higher than the currently recommended target concentration, are highly associated with histologic remission and sustained histologic remission.

Pretreatment HLADQA1-HLADRB1 Testing for the Prevention of Azathioprine-Induced Pancreatitis in Inflammatory Bowel Disease: A Prospective Cohort Study

Abstract: Introduction Azathioprine-induced pancreatitis is an idiosyncratic and unpredictable response, occurring in up to 7% of azathioprine-exposed patients with inflammatory bowel disease (IBD). The haplotype HLADQA1-HLADRB1*07:01A>C is strongly associated with azathioprine-induced pancreatitis in IBD. We aimed to evaluate whether pretreatment HLADQA1-HLADRB1*07:01A>C screening will reduce the risk of azathioprine-induced pancreatitis. Methods Participants with IBD were screened for HLADQA1-HLADRB1*07:01A>C, and participants with a variant genotype were excluded from azathioprine treatment. Wild-type participants were started on azathioprine and followed for 3 months. The incidence of pancreatitis was compared with unscreened historical controls. Results HLADQA1-HLADRB1*07:01A>C screening resulted in an 11-fold reduction in the incidence of azathioprine-induced pancreatitis (n = 1/328 or 0.30% vs n = 13/373 or 3.4%). In propensity score-matched cohorts (age and sex), HLA DQA1-HLADRB1*07:01A>C screening was significantly associated with a reduction in the incidence of AZA-induced pancreatitis independent of weight, glucocorticoid exposure, and smoking status (adjusted odds ratio = 0.075, 95% confidence interval = 0.01-0.58, P = 0.01). Up to 45% (n = 271/599) of participants were excluded from azathioprine therapy based on the haplotype in the HLADQA1-HLADRB1*07:01A>C-screened cohort. Discussion HLADQA1-HLADRB1*07:01A>C screening reduced the risk of azathioprine-induced pancreatitis; however, using this strategy to guide the use of azathioprine therapy in IBD may eliminate a large proportion of patients from being eligible for treatment with azathioprine. In regions where there is access to other IBD therapies, and given the short-term and long-term toxicities associated with azathioprine, HLADQA1-HLADRB1*07:01A>C-screening may be a clinically relevant strategy for enhancing the safe use of azathioprine in IBD. In addition, cost-effectiveness analyses are needed to further solidify the utility of HLADQA1-HLADRB1*07:01A>C screening in IBD populations.

Pharmacogenomic-based personalized medicine: Multistakeholder perspectives on implementational drivers and barriers in the Canadian healthcare system.

Abstract: Pharmacogenomics (PGx)-based personalized medicine (PM) is increasingly utilized to guide treatment decisions for many drug-disease combinations. Notably, London Health Sciences Centre (LHSC) has pioneered a PGx program that has become a staple for London-based specialists. Although implementational studies have been conducted in other jurisdictions, the Canadian healthcare system is understudied. Herein, the multistakeholder perspectives on implementational drivers and barriers are elucidated. Using a mixed-method qualitative model, key stakeholders, and patients from LHSC's PGx-based PM clinic were interviewed and surveyed, respectively. Interview transcripts were thematically analyzed in a stepwise process of customer profiling, value mapping, and business model canvasing. Value for LHSC located specialist users of PGx was driven by the quick turnaround time, independence of the PGx clinic, and the quality of information. Engagement of external specialists was only limited by access and awareness, whereas other healthcare nonusers were limited by education and applicability. The major determinant of successful adoption at novel sites were institutional champions. Patients valued and approved of the service, expressed a general willingness to pay, but often traveled far to receive genotyping. This paper discusses the critical pillars of education, awareness, advocacy, and efficiency required to address implementation barriers to healthcare service innovation in Canada. Further adoption of PGx practices into Canadian hospitals is an important factor for advancing system-level changes in care delivery, patient experiences, and outcomes. The findings in this paper can help inform efforts to advance clinical PGx practices, but also the potential adoption and implementation of other innovative healthcare service solutions.

A Comparative Analysis of Drug Therapy, Disease Phenotype, and Health Care Outcomes for Men and Women with Inflammatory Bowel Disease

Abstract: Sex and gender refer to biological and social differences between men and women. While well-evaluated in other disciplines, their roles in inflammatory bowel disease (IBD) are not well-defined. This study aimed to characterize differences in healthcare outcomes in men and women with IBD. A retrospective single-centre cohort study was conducted to evaluate differences between men and women receiving care for Crohn’s disease (CD) and ulcerative colitis (UC) at the Western University Personalized Medicine Clinic from March 2012 to September 2019. The primary endpoint was the proportion of IBD drugs used for all drug classes. Additional outcomes in healthcare utilization and disease phenotype were assessed. Student's t test and Fisher's exact test were used to assess differences A total of 1015 participants were included (CD = 656; UC = 359). In UC and CD, 47.9% and 59.0% were women, respectively. Overall, women were more likely prescribed budesonide than men (23.6% vs. 13.4%; p 55 being less likely to receive biologics. These findings highlight differences in disease course and treatment approaches between men and women with IBD and support the consideration of sex and gender when researching disease outcomes.

Understanding value in a healthcare setting: An application of the business model canvas:

Abstract: The business model canvas is a popular tool used to develop value-driven business models. Specific emphasis is placed on understanding what customers value and providing users with steps on how to ...

Organic Anion Transporting Polypeptide 2B1 (OATP2B1) Genetic Variants: In Vitro Functional Characterization and Association With Circulating Concentrations of Endogenous Substrates.

Abstract: Organic anion transporting polypeptide 2B1 (OATP2B1, gene SLCO2B1) is an uptake transporter that is thought to determine drug disposition and in particular, the oral absorption of medications. At present, the clinical relevance of SLCO2B1 genetic variation on pharmacokinetics is poorly understood. We sought to determine the functional activity of 5 of the most common missense OATP2B1 variants (c.76_84del, c.601G>A, c.917G>A, c.935G>A, and c.1457C>T) and a predicted dysfunctional variant (c.332G>A) in vitro. Furthermore, we measured the basal plasma concentrations of endogenous OATP2B1 substrates, namely estrone sulfate, dehydroepiandrosterone sulfate (DHEAS), pregnenolone sulfate, coproporphyrin I (CPI), and CPIII, and assessed their relationships with SLCO2B1 genotypes in 93 healthy participants. Compared to reference OATP2B1, the transport activities of the c.332G>A, c.601G>A and c.1457C>T variants were reduced among the substrates examined (estrone sulfate, DHEAS, CPI, CPIII and rosuvastatin), although there were substrate-dependent effects. Lower transport function of OATP2B1 variants could be explained by diminished cell surface expression. Other OATP2B1 variants (c.76-84del, c.917G>A and c.935G>A) had similar activity to the reference transporter. In the clinical cohort, the SLCO2B1 c.935G>A allele was associated with both higher plasma CPI (42%) and CPIII (31%) concentrations, while SLCO2B1 c.917G>A was linked to lower plasma CPIII by 28% after accounting for the effects of age, sex, and SLCO1B1 genotypes. No association was observed between SLCO2B1 variant alleles and estrone sulfate or DHEAS plasma concentrations, however 45% higher plasma pregnenolone sulfate level was associated with SLCO2B1 c.1457C>T. Taken together, we found that the impacts of OATP2B1 variants on transport activities in vitro were not fully aligned with their associations to plasma concentrations of endogenous substrates in vivo. Additional studies are required to determine whether circulating endogenous substrates reflect OATP2B1 activity.

Association of sex with stroke and bleeding risk of apixaban and rivaroxaban in elderly atrial fibrillation patients using propensity score weights

Abstract: Background Evidence from clinical trials suggests a differential effect of sex on the effectiveness and safety of direct oral anticoagulants (DOAC) for stroke prophylaxis in atrial fibrillation (AF). Methods This population-based cohort study examined the independent effect of sex on hemorrhage and ischemic stroke in 23,884 patients (55% females; ≥66 years) with AF starting apixaban or rivaroxaban treatment in Ontario, Canada. Patients were followed 90 days after their DOAC prescription. Using female sex as the exposure of interest, differences in baseline characteristics were balanced between sexes using inverse probability weights based on propensity scores. Applying weighted modified Poisson regression, risk ratios (RR) were estimated for major hemorrhage, ischemic stroke/systemic embolism/transient ischemic attack (thereafter stroke), myocardial infarction (MI), and all-cause mortality, with males as reference. Results Females were older, had higher predicted stroke risk (CHADS2) and fewer comorbidities than males. Males had a higher prevalence of coronary artery disease, diabetes, and cancer, and similar predicted bleeding risk (HAS-BLED). After weighting, baseline characteristics were well balanced. The 90-day risks for hemorrhage (RR 0.96; 95% CI 0.80-1.15; p=0.69) and stroke (RR 1.01; 95% CI 0.86-1.19; p=0.94) were similar between sexes which remained true when assessing each DOAC separately by dosing regimen. Compared to males, females had a lower risk for MI (RR 0.66; 95% CI 0.52-0.84; p=0.0008), and all-cause mortality (RR 0.76; 95% CI 0.67-0.87; p Conclusions Our findings do not suggest an association of sex with the 90-day risk of hemorrhage or ischemic stroke in older AF patients prescribed apixaban or rivaroxaban.

Pharmacokinetics of a once-daily tacrolimus formulation in first nations and caucasian liver transplant recipients

Abstract: Patient ethnicity may influence the pharmacokinetics (PK) of tacrolimus. Because the Canadian First Nations (FN) constitute a large and increasing segment of the liver transplant population, we undertook to determine whether PK differences exist for a once-daily, extended release formulation of tacrolimus (Advagraf) in FN compared to Caucasian (CAUC) liver transplant recipients. Following achievement of a steady state with Advagraf, blood samples were drawn at 0, 1, 2, 4, 6, 8 and 24 hours for whole blood tacrolimus levels by commercial immunoassay and CYP3A4 and CYP3A5 allele analyses were performed by polymerase chain reactions. Nineteen subjects participated in the study (7 FN and 12 CAUC). The FN cohort had significantly higher AUC (214 ± 48 versus 168 ± 25, P < 0.05), Cmax (16.7 ± 4.4 ng/ml versus 11.3 ± 1.7 ng/ml, P < 0.05), Cmin (6.1 ± 1.0 ng/ml versus 4.7 ± 0.5 ng/ml, P < 0.05) and shorter Tmax (1.6 ± 0.2 hours versus 2.8 ± 0.3 hours, P < 0.05) values than CAUCs. CYP3A4 genotypes were C/C in both cohorts, while the CYP3A5 *1/*3 allele was present in 2/5 FN and 0/9 CAUC. The results of this study indicate that once-daily, extended release Advagraf results in higher blood tacrolimus levels and shorter times to Cmax in FN compared to CAUC liver transplant recipients.