Infliximab Tissue Concentrations in Patients With Stable Ulcerative Colitis Are Correlated With More Durable Infliximab-associated Disease Remission.

BACKGROUND: We aimed to determine the correlation between tissue and plasma infliximab concentrations in an outpatient ulcerative colitis (UC) cohort based on histologic disease activity in addition to their relationship with long-term clinical outcomes. We assessed intraparticipant variability in infliximab concentrations between adjacent intestinal samples and the correlation between disease activity and tumor necrosis factor-α (TNF-α). METHODS: A prospective cohort study was conducted in participants with UC receiving infliximab. Blood and 2 sigmoid colon biopsies were obtained at the index colonoscopy for infliximab and TNF-α quantification. Histological disease activity was assessed. Participants were followed for 2 years for the occurrence of hospitalization, surgery, disease relapse, and infliximab discontinuation. RESULTS: A positive correlation was observed between mean plasma and uninflamed tissue infliximab concentrations only (Rs = 0.75, P = .0071). Lower mean tissue infliximab concentrations correlated with a shorter time to disease relapse vs those with higher mean tissue concentrations (Rs = 0.77, P = .032). This was not seen when using plasma infliximab concentrations. Additionally, no significant intraparticipant variability of infliximab concentrations was observed for all participants independent of disease activity. Neither plasma nor tissue TNF-α correlated with disease activity. CONCLUSIONS: These findings support data generated in patients with Crohn's disease: plasma infliximab concentrations are reflective of infliximab exposure in tissue in the UC patient in remission, but not for those with active disease. Increasing tissue concentrations in the noninflamed tissues may improve durability of infliximab. Neither plasma nor tissue TNF-α appear to correlate with UC disease activity. Larger follow-up studies would be of benefit.

Plasma infliximab concentrations are reflective of infliximab exposure in tissue in the UC patient in remission, but not for those with active disease. Increasing tissue concentrations in the noninflamed tissues may improve durability of infliximab.

Low-Dose Methotrexate and Serious Adverse Events Among Older Adults With Chronic Kidney Disease.

Importance: Low-dose methotrexate is used to treat rheumatoid arthritis and psoriasis. Due to its kidney elimination, better evidence is needed to inform its safety in adults with chronic kidney disease (CKD). Objectives: To compare the 90-day risk of serious adverse events among adults with CKD who started low-dose methotrexate vs those who started hydroxychloroquine and to compare the risk of serious adverse events among adults with CKD starting 2 distinct doses of methotrexate vs those starting hydroxychloroquine. Design, Setting, and Participants: This retrospective, population-based, new-user cohort study was conducted in Ontario, Canada (2008-2021) using linked administrative health care data. Adults aged 66 years or older with CKD (defined as an estimated glomerular filtration rate [eGFR] <60 mL/min/1.73 m2 but not receiving dialysis) who started low-dose methotrexate (n = 2309) were matched 1:1 with those who started hydroxychloroquine. Exposure: Low-dose methotrexate (5-35 mg/wk) vs hydroxychloroquine (200-400 mg/d). Main Outcome and Measure: The primary outcome was a composite of serious adverse events: a hospital visit with myelosuppression, sepsis, pneumotoxic effects, or hepatotoxic effects within 90 days of starting the study drug. Prespecified subgroup analyses were conducted by eGFR category. Propensity score matching was used to balance comparison groups on indicators of baseline health. Risk ratios (RRs) were obtained using modified Poisson regression, and risk differences (RDs) using binomial regression. Results: In a propensity score-matched cohort of 4618 adults with CKD (3192 [69%] women; median [IQR] age, 76 [71-82] years), the primary outcome was higher in patients who started low-dose methotrexate vs those who started hydroxychloroquine (82 of 2309 [3.55%] vs 40 of 2309 [1.73%]; RR, 2.05 (95% CI, 1.42-2.96); RD, 1.82% [95% CI, 0.91%-2.73%]). In subgroup analysis, the risks increased progressively at lower eGFR (eg, eGFR <45 mL/min/1.73 m2: RR, 2.79 [95% CI, 1.51-5.13]). In the secondary comparison with hydroxychloroquine, methotrexate users at 15 to 35 mg/wk had a higher risk of the primary outcome. Conclusions and Relevance: In this cohort of 4618 older patients with CKD, the 90-day risk of serious adverse events was higher among those who started low-dose methotrexate than those who started hydroxychloroquine. If verified, these risks should be balanced against the benefits of low-dose methotrexate use.

Adverse events with quetiapine and clarithromycin coprescription: A population-based retrospective cohort study.

Background and Aims: Quetiapine is an atypical antipsychotic predominantly metabolized by the cytochrome P450 3A4 (CYP3A4) enzyme. We studied the risk of adverse events following coprescription of clarithromycin (a strong CYP3A4 inhibitor) versus azithromycin (not a CYP3A4 inhibitor) in quetiapine users. Materials and Methods: This was a population-based retrospective cohort study from 2004 to 2020 in Ontario, Canada in adult quetiapine users newly co-prescribed clarithromycin (n = 16,909) or azithromycin (n = 25,267). The primary outcome was the composite of hospital encounters with encephalopathy (defined as a diagnosis of delirium, disorientation, transient alteration of awareness, transient ischemic attack, or unspecified dementia), a fall, or a fracture within 30 days of new coprescription. Secondary outcomes were individual components of the composite outcome, hospital encounter with computed tomography (CT) head scan, and all-cause mortality. Results: Coprescription of clarithromycin versus azithromycin with quetiapine was associated with a higher risk of the primary composite outcome (365 of 16,909 clarithromycin users [2.2%] vs. 309 of 16,929 azithromycin users [1.8%]; absolute risk increase, 0.34% [95% confidence interval, CI, 0.04-0.63]; relative risk [RR], 1.19 [95% CI, 1.02-1.38]). This was primarily driven by an increase in fragility fractures (78 of 16,909 clarithromycin users [0.5%] vs. 45 of 16,923 azithromycin users [0.3%]; absolute risk increase, 0.20% [95% CI, 0.07-0.32]; RR, 1.74 [95% CI, 1.21-2.52]). Hospital encounters with a CT head scan were higher in clarithromycin users (220 of 16,909 [1.3%] vs. 175 of 16,923 azithromycin users [1.0%]; absolute risk increase, 0.27% [95% CI, 0.04-0.50]; RR, 1.26 [95% CI, 1.04-1.54]), but there was no difference in hospital encounters with encephalopathy, falls, or all-cause mortality between macrolide groups. Conclusion: Among adults taking quetiapine, concurrent use of clarithromycin compared with azithromycin was associated with a small but statistically greater 30-day risk of a hospital encounter for encephalopathy, falls, or fracture, which was predominantly related to a higher rate of fragility fractures.

Thiopurine Methyltransferase Intermediate Metabolizer Status and Thiopurine-Associated Toxicity During Maintenance Therapy in Childhood Acute Lymphoblastic Leukemia.

Mercaptopurine is a cornerstone of maintenance chemotherapy in childhood acute lymphoblastic leukemia (ALL). Its cytotoxic effects are mediated by 6-thioguanine nucleotides (TGNs) incorporation into lymphocyte DNA. Thiopurine methyltransferase (TPMT) inactivates mercaptopurine, and deficiency resulting from genetic variants increases TGN exposure and hematopoietic toxicity. Although mercaptopurine-dose reduction reduces toxicity risk without compromising relapse rate in patients with TPMT deficiency, dosing recommendations for those with moderately reduced activity (intermediate metabolizer (IM)) are less clear and their clinical impacts have yet to be established. This cohort study assessed the effect of TPMT IM status on mercaptopurine-associated toxicity and TGN blood exposure in pediatric patients with ALL initiated on standard dose mercaptopurine. Of 88 patients studied (mean age 4.8 years), 10 (11.4%) were TPMT IM, and all had undergone ≥ 3 cycles of maintenance therapy (80% completed). A larger proportion of TPMT IM than normal metabolizers (NM) had febrile neutropenia (FN) during the first two cycles of maintenance, reaching significance in the second cycle (57% vs. 15%, respectively; odds ratio = 7.33, P < 0.05). Compared to NM, FN events occurred more frequently and with prolonged duration in IM in cycles 1 and 2 (adjusted P < 0.05). IM had a 2.46-fold increased hazard ratio for FN, and about twofold higher TGN level than NM (P < 0.05). Myelotoxicity was more common in IM than NM (86% vs. 42%, respectively) during cycle 2 (odds ratio = 8.2, P < 0.05). TPMT IM initiated at a standard mercaptopurine dose are at greater risk for FN during early cycles of maintenance therapy, thus our findings support genotype-guided dose adjustment to reduce toxicity.

DPYD Exon 4 Deletion Associated with Fluoropyrimidine Toxicity and Importance of Copy Number Variation.

Fluoropyrimidine chemotherapy is associated with interpatient variability in toxicity. A major contributor to unpredictable and severe toxicity relates to single nucleotide variation (SNV) in dihydropyrimidine dehydrogenase (DPYD), the rate-limiting fluoropyrimidine metabolizing enzyme. In addition to SNVs, a study of Finnish patients suggested that a DPYD exon 4 deletion was observed in their population. To better understand the potential generalizability of such findings, we investigated the presence of this exon 4 deletion in our Canadian patient population, using a TaqMan assay. We selected 125 patients who experienced severe fluoropyrimidine-associated toxicity, and 125 matched controls. One patient in the severe toxicity group harbored a haploid DPYD exon 4 deletion, and required a 35% dose reduction after their first fluoropyrimidine treatment cycle due to toxicity and required an additional 30% dose reduction before tolerating treatment. The predicted allele frequency was 0.2% in our cohort, much lower than the 2.4% previously reported. We also carried out a literature review of copy number variation (CNV) in the DPYD gene, beyond fluoropyrimidine toxicity and show that various types of CNV in DPYD are present in the population. Taken together, our findings suggest that CNV in DPYD may be an underappreciated determinant of DPYD-mediated fluoropyrimidine toxicity.

Impact of organic anion transporting polypeptide, P-glycoprotein, and breast cancer resistance protein transporters on observed tamoxifen and endoxifen concentration and adverse effects.

OBJECTIVE: Drug transporters are important determinants of drug disposition and response. Tamoxifen is an antiestrogen for breast cancer therapy known for adverse drug reactions (ADRs). In this study, the involvement of OATP transporters in tamoxifen and endoxifen transport was studied in vitro while the impact of single nucleotide variation (SNV) in OATP and efflux transporters P-glycoprotein ( ABCB1 ) and Breast Cancer Resistance Protein ( ABCG2 ) on ADRs during tamoxifen therapy were assessed. METHODS: Patients receiving tamoxifen for breast cancer, who were CYP2D6 normal metabolizers were enrolled ( n = 296). Patients completed a survey that captured ADRs and a blood sample was collected. Tamoxifen and endoxifen plasma concentration were measured, while DNA was genotyped for SNVs in ABCB1, ABCG2, SLCO1A2, SLCO1B1 , and SLCO2B1 . HEK293T cells were used to determine the extent of OATP-mediated transport of tamoxifen and endoxifen. RESULTS: Common SNVs of ABCB1, ABCG2, SLCO1A2 , and SLCO1B1 were not associated with tamoxifen or endoxifen concentration. However, tamoxifen concentration was significantly higher in carriers of SLCO2B1 c.935G>A (129.8 ng/mL) compared to wildtype (114.9 ng/mL; P = 0.036). Interestingly, subjects who carried SLCO1A2 c.38A>G reported significantly less dizziness ( P = 0.016). In-vitro analysis demonstrated increased cellular accumulation of tamoxifen in cells overexpressing OATP1A2 and 1B1, but endoxifen uptake was not effected in OATP overexpressing cells. CONCLUSIONS: We showed that OATP1A2 , a transporter known to be expressed at the blood-brain barrier, is capable of tamoxifen transport. Additionally, OATP1A2 c.38A>G was associated with reduced ADRs. Taken together, our findings suggest genetic variation in OATP transporters may be an important predictor of tamoxifen ADRs.

Fluoropyrimidine-associated toxicity and DPYD variants c.85T>C, c.496A>G, and c.1236G>A: impact of haplotype.

Dihydropyrimidine dehydrogenase (DPYD) is the rate-limiting step in fluoropyrimidines metabolism. Currently, genotype-guided fluoropyrimidine dosing is recommended for four DPYD single nucleotide variants (SNVs). However, the clinical impact of additional DPYD SNVs on fluoropyrimidine-related toxicity remains controversial. We assessed common DPYD SNVs c.85T>C, and c.496A>G which are often in linkage disequilibrium with c.1236G>A, a variant currently recommended for DPYD genotyping, in a retrospective cohort of cancer patients who had received fluoropyrimidines (N = 1371). When assessing individual SNVs, during the total chemotherapy treatment period, a significant increased risk of severe grade ≥ 3 toxicity was seen in carriers of c.496A>G (OR = 1.38, 95% CI 1.01-1.88, p = 0.0405) after adjusting for age, sex and treatment drug (capecitabine or 5-Fluorouracil). No association with fluoropyrimidine-related toxicity was seen in patients given standard dosing among those carrying one allele of DPYD c.1236G>A (OR = 1.19, 95% CI 0.59-2.27, p = 0.6147) or c.85T>C (OR = 1.04, 95% CI 0.80-1.62, p = 0.7536). Haplotype analysis confirmed a high linkage disequilibrium of these three variants. Toxicity was not significantly increased in haplotypes containing only one of c.85T>C or c.496A>G or c.1236G>A alleles. However, the haplotype containing both c.85T>C and c.496A>G alleles, which had a predicted frequency of 7.1%, was associated with an increased risk of fluoropyrimidine toxicity (OR = 1.57, 95% CI 1.15-2.13, p = 0.0041). This study suggests DPYD haplotype structure may help explain previous conflicting studies concerning the impact of these variants. Our findings suggest patients with both DPYD c.85T>C and c.496A>G variants have a significant increased risk for toxicity and may potentially benefit from genotype-guided fluoropyrimidine dosing.

High oncostatin M predicts lack of clinical remission for patients with inflammatory bowel disease on tumor necrosis factor α antagonists.

The interleukin-6 family cytokine, oncostatin-M (OSM) has been associated with response to tumor necrosis factor-α antagonists (anti-TNFs) in small cohorts of patients with inflammatory bowel disease (IBD). We aimed to evaluate the association between plasma OSM concentrations and response to anti-TNFs (infliximab and adalimumab) in both ulcerative colitis (UC) and Crohn's disease (CD). A retrospective cohort study was conducted in patients with IBD with a history of anti-TNF exposure. Blood samples, collected prior to anti-TNF exposure, were analyzed by enzyme-linked immunosorbent assay for the presence and quantity of OSM. Clinical remission was assessed at 1-year post anti-TNF exposure in addition to the occurrence of surgery, hospitalization, corticosteroid use, and adverse drug events. Lastly the threshold OSM plasma concentration associated with anti-TNF non-response was assessed by receiver operator characteristic (ROC) curve analysis. Patients with IBD (CD, n = 82; UC, n = 40) were assessed. In both UC and CD, mean pre-treatment OSM concentrations were significantly lower in those who achieved clinical remission at 1-year (p < 0.0001). A threshold plasma OSM concentration of 168.7 pg/ml and 233.6 pg/ml respectively separated those who achieved clinical remission at 1-year on an anti-TNF from those who did not in CD and UC respectively (CD: area under the receiver operator characteristic curve, AUROC = 0.880, 95% CI 0.79-0.96; UC: AUROC = 0.938, 95% CI 0.87-1.00). High OSM concentrations were associated with anti-TNF discontinuation and use of rescue steroids in CD and UC. High pre-treatment OSM concentrations identify IBD patients at-risk of anti-TNF non-response at 1-year as well as other deleterious clinical outcomes.

Association of Sex With Stroke and Bleeding Risk of Apixaban and Rivaroxaban in Elderly Atrial Fibrillation Patients Using Propensity Score Weights.

BACKGROUND: Evidence from clinical trials suggests a differential effect of sex on the effectiveness and safety of direct oral anticoagulants (DOACs) 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; age ≥ 66 years) with AF starting apixaban or rivaroxaban treatment in Ontario, Canada. Patients were followed for 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 (RRs) were estimated for major hemorrhage, ischemic stroke/systemic embolism/transient ischemic attack (hereafter stroke), myocardial infarction, and all-cause mortality, with males as a reference. RESULTS: Females were older, had higher predicted stroke risk (based on CHADS2 score), and had fewer comorbidities than did males. Males had a higher prevalence of coronary artery disease, diabetes, and cancer, and similar predicted bleeding risk (based on HAS-BLED score). After weighting, baseline characteristics were well balanced. The 90-day risks for hemorrhage (RR 0.96; 95% confidence interval [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 myocardial infarction (RR 0.66; 95% CI 0.52-0.84; P = 0.0008), and for all-cause mortality (RR 0.76; 95% CI 0.67-0.87; P < 0.0001). 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.

CONTEXTE: Les données probantes issues des essais cliniques donnent à penser que l'efficacité et l'innocuité des anticoagulants oraux directs (AOD) utilisés pour la prophylaxie des accidents vasculaires cérébraux (AVC) dans un contexte de fibrillation auriculaire (FA) varient selon le sexe du patient. MÉTHODOLOGIE: Cette étude de cohorte populationnelle a examiné l'effet indépendant du sexe sur l'hémorragie et l'AVC ischémique chez 23 884 patients (55 % de femmes; âge ≥ 66 ans) atteints de FA ayant amorcé un traitement par l'apixaban ou le rivaroxaban en Ontario (Canada). Les patients ont été suivis pendant 90 jours après avoir reçu une ordonnance d'AOD. Le sexe féminin constituant l'exposition d'intérêt, les différences quant aux caractéristiques initiales ont été réparties de façon équilibrée entre les sexes au moyen d'une pondération par probabilité inverse reposant sur le score de propension. La régression de Poisson modifiée avec pondération a servi à estimer les rapports de risques (RR) d'hémorragie majeure, d'AVC ischémique/d'embolie systémique/d'accident ischémique transitoire (ci-après AVC), d'infarctus du myocarde et de mortalité toutes causes confondues, les hommes formant la population de référence. RÉSULTATS: Les femmes étaient plus âgées, présentaient un risque prévu d'AVC plus élevé (d'après le score CHADS2) et présentaient moins de maladies concomitantes que les hommes. Les hommes présentaient une prévalence plus élevée de coronaropathie, de diabète et de cancer, et un risque prévu d'hémorragie similaire (compte tenu du score HAS-BLED). Après la pondération, la répartition des caractéristiques initiales des patients était bien équilibrée. Le risque d'hémorragie (RR : 0,96; intervalle de confiance [IC] à 95 % : 0,80-1,15; P = 0,69) et d'AVC (RR : 1,01; IC à 95 % : 0,86-1,19; P = 0,94) sur 90 jours était similaire pour les deux sexes, et il en était de même lorsque chaque AOD a été évalué séparément en fonction du schéma posologique. Par rapport aux hommes, les femmes présentaient un risque plus faible d'infarctus du myocarde (RR : 0,66; IC à 95 % : 0,52-0,84; P = 0,0008) et de mortalité toutes causes confondues (RR : 0,76; IC à 95 % : 0,67-0,87; P < 0,0001). CONCLUSIONS: Nos résultats ne laissent présumer aucune association entre le sexe et le risque d'hémorragie ou d'AVC ischémique sur une période de 90 jours chez les patients âgés atteints de FA à qui l'apixaban ou le rivaroxaban sont prescrits.

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

BACKGROUND: 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. METHODS: 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 RESULTS: 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 < 0.0001), while more men were exposed to prednisone for IBD management (73.5% vs. 67.4%; p = 0.04). Immunomodulator use was higher in men with CD versus women (86.6% vs. 78.3%; p = 0.008) and of those exposed, women more commonly experienced ADRs (29.5% vs. 21.2%; p = 0.01). Though no sex-related difference was identified, age was a predictor of biologic exposure in women with CD and men with UC, with those > 55 being less likely to receive biologics. CONCLUSIONS: 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.

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

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.

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

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.

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

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.

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

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.

Genetic variation in the farnesoid X-receptor predicts Crohn's disease severity in female patients.

The farnesoid X receptor (FXR) is implicated in Crohn's disease (CD) pathogenesis. It is unclear how genetic variation in FXR impacts CD severity versus genetic variation in nuclear receptors such as pregnane X receptor (PXR) and the multi-drug resistance protein 1 (MDR1, ABCB1). To evaluate FXR-1G > T as a genomic biomarker of severity in CD and propose a plausible molecular mechanism. A retrospective study (n = 542) was conducted in a Canadian cohort of CD patients. Genotypic analysis (FXR-1G > T, MDR1 3435C > T and PXR -25385C > T) as well as determination of the FXR downstream product, fibroblast growth factor (FGF) 19 was performed. Primary outcomes included risk and time to first CD-related surgery. The effect of estrogen on wild type and variant FXR activity was assessed in HepG2 cells. The FXR-1GT genotype was associated with the risk of (odds ratio, OR = 3.34, 95% CI = 1.58-7.05, p = 0.002) and earlier progression to surgery (hazard ratio, HR = 3.00, 95% CI = 1.86-4.83, p < 0.0001) in CD. Female carriers of the FXR-1GT genotype had the greatest risk of surgery (OR = 14.87 95% CI = 4.22-52.38, p < 0.0001) and early progression to surgery (HR = 6.28, 95% CI = 3.62-10.90, p < 0.0001). Women carriers of FXR-1GT polymorphism had a three-fold lower FGF19 plasma concentration versus women with FXR-1GG genotype (p < 0.0001). In HepG2 cells cotransfected with estrogen receptor (ER) and FXR, presence of estradiol further attenuated variant FXR activity. MDR1 and PXR genotypes were not associated with surgical risk. Unlike MDR1 and PXR, FXR-1GT genetic variation is associated with earlier and more frequent surgery in women with CD. This may be through ER-mediated attenuation of FXR activation.

Genetic and clinical predictors of arthralgia during letrozole or anastrozole therapy in breast cancer patients.

PURPOSE: Female patients with breast cancer frequently develop arthralgia when treated with aromatase inhibitors (AI). Although the mechanism of AI-induced arthralgia is unknown, potential biomarkers have been identified. The purpose of this study was to investigate the clinical and genetic predictors of AI-induced arthralgia in a prospective cohort of patients with estrogen receptor-positive breast cancer. METHODS: One hundred and ninety-six patients were enrolled at initiation of AI therapy with either letrozole or anastrozole. Patients completed two validated self-report questionnaires assessing pain, stiffness, and physical function at baseline, and repeated the questionnaires at two and at six months after the initiation of treatment with an AI. Germline DNA of all patients was genotyped for seven single-nucleotide polymorphisms (SNPs) previously identified by genetic screens and genome-wide association studies as associated with AI-induced arthralgia. RESULTS: More than 50% of the study group experienced arthralgia symptoms. Genetic analysis revealed that four SNPs, in CYP19A1 (rs4775936) and ESR1 (rs9322336, rs2234693, rs9340799), were associated with the development of arthralgia (adjusted P = 0.016, 0.018, 0.017, 0.047). High body mass index (BMI) was also associated with the development of arthralgia symptoms (adjusted P = 0.001). Patients prescribed letrozole were significantly more likely to develop arthralgia than patients on anastrozole (P = 0.018), and also more likely to discontinue AI therapy due to arthralgia. The CYP19A1 (rs4775936) SNP was significantly associated with discontinuation of therapy due to intolerable arthralgia. CONCLUSIONS: Our results suggested that BMI and AI drug (letrozole versus anastrozole) were clinical predictors of arthralgia, while genetic variants rs4775936, rs9322336, rs2234693, and rs9340799 were genetic predictors of AI-induced arthralgia. Significantly, rs4775936 was also a predictor of discontinuation of therapy.

In Vitro Functional Characterization and in Silico Prediction of Rare Genetic Variation in the Bile Acid and Drug Transporter, Na+-Taurocholate Cotransporting Polypeptide (NTCP, SLC10A1).

Na+-taurocholate cotransporting polypeptide (NTCP, SLC10A1) is a key hepatic uptake transporter for bile acids and drugs and is the main functional receptor for hepatitis B and D viruses. Next-generation sequencing has revealed that a large number of rare SLC10A1 variants exist in the population. Little data exist regarding head-to-head comparison of in silico algorithms to predict functional effects of pharmacogenetic variants when compared to direct in vitro functional assessment. This study aimed at characterizing rare SLC10A1 variants in vitro and to assess the performance of seven in silico algorithms to predict the observed functional impacts. Thirty-five previously uncharacterized, rare, missense SLC10A1 variants were transiently expressed in human embryonic kidney 293 type T (HEK293T) cells. NCTP protein expression as well as uptake of substrates taurocholic acid (TCA) and rosuvastatin were assessed. Substrate-specific effects were observed for NTCP G191R, with TCA and rosuvastatin transport observed at 89 and 8% of wild-type (WT) uptake, respectively. Significantly reduced transport of TCA and rosuvastatin was observed for 19 variants (p < 0.05), with seven variants displaying decreased protein expression and marked reduction in transport of both substrates (0-13% of WT uptake, p < 0.0001). Performance of in silico algorithms to predict in vitro uptake, assessed using the area under the receiver operating characteristic curves (AUCROC), ranged from 0.69 to 0.97 and 0.72 to 0.84 for TCA and rosuvastatin uptake, respectively. In conclusion, we identified rare variants with significantly reduced NTCP expression and function. We demonstrated that no algorithm performed robustly enough to replace functional study in vitro, particularly given the broad substrate specificity of many pharmacogenes.

Attenuation of bile acid-mediated FXR and PXR activation in patients with Crohn's disease.

Bile acids are endogenous ligands of nuclear receptors pregnane X (PXR) and farnesoid X (FXR). PXR and FXR regulate pathways that are impaired in inflammatory bowel disease (IBD). Decreases in PXR and FXR activity are documented in IBD; however reasons for this are unknown. We aimed to assess the effect of Crohn's disease (CD) on the plasma bile acid composition in vivo and the resultant impact on PXR and FXR activation. A cross-sectional study evaluated the plasma concentrations of 12 bile acids in addition to 4ß-hydroxycholesterol (4ßOHC), an in vivo probe of the PXR target-gene cytochrome 3A4 (CYP3A4) and the FXR target-gene, fibroblast growth factor (FGF) 19 in individuals with (n = 74) and without (n = 71) CD. An in vitro model was used to assess the impact of CD-specific changes in the plasma bile acid composition on PXR and FXR activation. Decreases in glycochenodeoxycholic acid, taurocholic acid and lithocholic acid were seen in CD with increases in glycodeoxycholic acid and glycocholic acid relative to the total plasma bile acid profile. In vitro, increasing concentrations of bile acids applied in the same ratio as seen in the study cohorts resulted in decreased activation of both PXR and FXR in the CD model. In vivo, plasma 4ßOHC (CD = 18.68 ng/ml ± 13.02 ng/ml, non-CD = 46.38 ng/ml ± 40.70 ng/ml, p ≤ 0.0001) and FGF19 (CD = 0.276 pg/L ± 0.189 pg/L, non-CD = 0.485 pg/L ± 0.42 pg/L, p = 0.0002) concentrations were lower in CD versus controls. Ultimately, CD-specific changes in the plasma bile acid composition lead to reduced activation of FXR and PXR target genes in vitro and in vivo.