Dihydropyrimidine dehydrogenase and the efficacy and toxicity of 5-fluorouracil

Optimizing fluoropyrimidine therapy through dihydropyrimidine dehydrogenase polymorphism testing

Fluoropyrimidines (FP), including 5-fluorouracil and its prodrug capecitabine, are commonly employed in treating various solid tumors. Nonetheless, their use is frequently constrained by severe toxicities in 20%–30% of patients. Pharmacogenetic testing for dihydropyrimidine dehydrogenase (DPYD) deficiency, based on DPYD polymorphisms, has notably decreased severe adverse events, improving the safety of FP therapy. A recent D'Amato et al study evaluated the prevalence of DPYD polymorphisms and their effect on FP tolerability among Italian patients with gastrointestinal cancers. Although this study provided important insights into the significance of DPYD testing, its retrospective nature, inconsistency in testing DPYD variants, and lack of consideration for socioeconomic and confounding factors showed considerable limitations. Expanding the screening to include DPYD variants, addressing confounding biases through robust statistical analyses, and implementing prospective studies are critical next steps to strengthen the clinical evidence. Furthermore, the absence of a comprehensive cost-effectiveness analysis highlights the need for further financial assessments to advocate for broader implementation. We emphasized integrating DPYD-guided dosing, pre-treatment genetic counseling, and standardized testing procedures into clinical practice to improve patient outcomes and minimize treatment-related toxicities.

Pathological-microenvironment responsive injectable GelMA hydrogel with visualized biodegradation for pressure-assisted treatment of hypertrophic scars

Intralesional injection of 5-fluorouracil for the clinical treatment of hypertrophic scars (HS) remains challenging due to its short half-life, as well as the absence of evidence-based dosage and frequency injection guidelines. Herein, we developed a matrix metalloproteinases (MMPs)/reactive oxygen species (ROS)-responsive injectable prodrug hydrogel (GFP) that exhibits sustained drug release and fluorescence imaging capability, aiming to facilitate the optimization of injection dosage and frequency in HS treatment. The GFP hydrogel comprises gelatin methacryloyl and pendant methacryloyl-decorated tetrapeptide (PPPK) with 5-fluorouracil acetic acid/rhodamine B at the N-terminus. After intralesional injection and blue light irradiation, the crosslinked hydrogel in HS lesions exhibited long-term sustained drug release by consuming overexpressed MMPs and ROS, which could be visualized by fluorescence imaging to guide injection frequency for HS treatment. In addition, due to its exceptional swelling and mechanical properties, the GFP hydrogel exerts a certain pressure inside the HS tissues, functioning as an adjunctive therapy to inhibit HS. Our results demonstrate that the GFP hydrogel can promote fibroblast apoptosis, inhibit collagen synthesis, and remodel the microenvironment of HS. This study presents a promising visualized drug delivery platform that potentially guides the optimization of injection frequency and dosage in the treatment of HS.

Sex differences in toxicities and survival outcomes among Japanese patients with Stage III colorectal cancer receiving adjuvant fluoropyrimidine monotherapy: A pooled analysis of 4 randomized controlled trials (JCOG2310A)

BACKGROUND

Fluoropyrimidine remains the key agent of adjuvant chemotherapy for stage III colorectal cancer (CRC). Western studies have shown that female sex is a favorable prognostic factor after surgery, but it is also a risk factor for adverse events (AEs) during adjuvant chemotherapy with fluoropyrimidine. However, little is known about whether sex differences in treatment outcomes exist in this setting in the Asian population.

METHODS

Patients with stage III CRC who received adjuvant fluoropyrimidine monotherapy in 4 randomized controlled trials were analyzed. Incidences of AEs and survival outcomes were compared between female and male patients.

RESULTS

A total of 3170 patients (female, 1516; male, 1654) were included in this analysis. Compared with males, females were less likely to have a relative dose intensity (≥90 %: female 59.1 % vs. male 67.6 %), with a higher proportion of requiring dose reduction (28.8 % vs. 20.4 %) and a lower proportion of completing adjuvant chemotherapy (77.0 % vs. 81.7 %). Multivariable analyses demonstrated that female sex was associated with a higher incidence of grade 3-4 AEs (odds ratio 1.80 [95 % CI 1.51-2.14]). Female sex was identified as a favorable prognostic factor for overall survival (hazard ratio [HR]: 0.80 [0.65-0.97]) and relapse-free survival (HR: 0.73 [0.63-0.85]) in multivariable analyses. Female patients had fewer time-to recurrence (TTR) events than male patients (5-year TTR: 17.7 % vs. 22.3 %).

CONCLUSION

Sex had implications for the development of AEs and survival outcomes of Japanese patients with stage III CRC who received adjuvant fluoropyrimidine monotherapy.

Long-Term Outcomes of 5-Fluorouracil-Related Early-Onset Toxicities: A Retrospective Cohort Study

OBJECTIVES

We aimed to determine whether the occurrence of early-onset toxicities due to 5-fluorouracil (5-FU) in treatment-naive patients undergoing their first cycle of FOLFOX/FOLFIRINOX was associated with decreased overall survival, increased risk of treatment cessation, and hospitalization.

METHODS

This was a retrospective cohort study using patient information from community oncology practices. Patients who received their first dose of 5-FU from 1 January 2015 through 1 August 2023 were included. The occurrence of an early-onset 5-FU-related toxicity (during 5-FU infusion or up to 96 h after infusion completion) in the first cycle of FOLFOX/FOLFIRINOX was the explanatory variable. The primary endpoint was overall survival (OS); secondary endpoints included early treatment cessation and early hospital admission.

RESULTS

In total, 3988 patients were included; the median age was 62.9 years and 57.5% were male. Early-onset toxicities were observed in 19.1%, with vomiting, thrombocytopenia, and diarrhea being most common. Patients with early-onset toxicities had a median OS of 2.5 years [95% CI 2.2 to 2.9] compared with 5.3 years [95% CI 4.7 to 5.8] in patients without early-onset toxicities (p < 0.001). The occurrence of early-onset toxicities was associated with an adjusted hazard ratio of 1.61 [95% CI 1.44 to 1.80] and was also significantly associated with early treatment cessation (odds ratio [OR] 1.53, 95% CI 1.30 to 1.80) and early hospital admission (OR 8.69, 95% CI 3.45 to 24.18).

CONCLUSIONS

Early-onset toxicities related to 5-FU during the first cycle of FOLFOX/FOLFIRINOX treatment were associated with poor outcomes. Early recognition and prompt intervention are pertinent to improve outcomes in patients receiving fluoropyrimidine chemotherapy.

Can we identify patients carrying targeted deleterious DPYD variants with plasma uracil and dihydrouracil? A GPCO-RNPGx retrospective analysis

OBJECTIVES

Dihydropyrimidine dehydrogenase (DPD) deficiency is the main cause of severe fluoropyrimidine-related toxicities. The best strategy for identifying DPD-deficient patients is still not defined. The EMA recommends targeted DPYD genotyping or uracilemia (U) testing. We analyzed the concordance between both approaches.

METHODS

This study included 19,376 consecutive French patients with pre-treatment plasma U, UH2 and targeted DPYD genotyping (*2A, *13, D949V, *7) analyzed at Eurofins Biomnis (2015-2022).

RESULTS

Mean U was 9.9 ± 10.1 ng/mL (median 8.7, range 1.6-856). According to French recommendations, 7.3 % of patients were partially deficient (U 16-150 ng/mL) and 0.02 % completely deficient (U≥150 ng/mL). DPYD variant frequencies were *2A: 0.83 %, *13: 0.17 %, D949V: 1.16 %, *7: 0.05 % (2 homozygous patients with U at 22 and 856 ng/mL). Variant carriers exhibited higher U (median 13.8 vs. 8.6 ng/mL), and lower UH2/U (median 7.2 vs. 11.8) and UH2/U2 (median 0.54 vs. 1.37) relative to wild-type patients (p<0.00001). Sixty-six% of variant carriers exhibited uracilemia <16 ng/mL, challenging correct identification of DPD deficiency based on U. The sensitivity (% patients with a deficient phenotype among variant carriers) of U threshold at 16 ng/mL was 34 %. The best discriminant marker for identifying variant carriers was UH2/U2. UH2/U2<0.942 (29.7 % of patients) showed enhanced sensitivity (81 %) in identifying deleterious genotypes across different variants compared to 16 ng/mL U.

CONCLUSIONS

These results reaffirm the poor concordance between DPD phenotyping and genotyping, suggesting that both approaches may be complementary and that targeted DPYD genotyping is not sufficiently reliable to identify all patients with complete deficiency.

Increased potentiation of 5-fluorouracil induced thymidylate synthase inhibition by 5,10-methylenetetrahydrofolate (arfolitixorin) compared to leucovorin in patients with colorectal liver metastases; The Modelle-001 Trial

BACKGROUND

5-Fluorouracil (5-FU) is a cornerstone in treatment of colorectal cancer (CRC) and is usually combined with leucovorin (LV) to enhance the antitumour effect by increase thymidylate synthase (TS) inhibition, the key target enzyme for 5-FU. Arfolitixorin (Arfo) is an active form of the reduced folate, [6 R]-5,10-methylenetetrahydrofolate ([6 R]-MeTHF and in contrast to LV, does not need to be metabolized. The Modelle-001 was designed to explore whether a single intravenous bolus injection of Arfo as compared to LV, together with 5-FU increases the inhibition of TS, levels of folate concentrations and polyglutamylation in CRC liver metastases (CRLM) and liver parenchyma.

PATIENTS AND METHODS

Thirty patients with CRLM received either LV (60 mg/m2) or Arfo (30 mg/m2 or 120 mg/m2) in combination with 5-FU preoperatively. Levels of folates and and TS inhibition were measured.

RESULTS

Significantly higher MeTHF levels and higher TS inhibition were measured in the Arfo groups compared to LV60, and there was a difference in folate poly-glutamylation between the groups.

CONCLUSION

The Modelle-001 Trial demonstrated significantly higher levels of MeTHF in metastases following Arfo compared to LV. This resulted in a greater increase TS inhibition in metastases although not statistically significant.

Discovering novel germline genetic variants linked to severe fluoropyrimidine-related toxicity in- and outside DPYD

BACKGROUND

The Alpe-DPD study (NCT02324452) demonstrated that prospective genotyping and dose-individualization using four alleles in DPYD (DPYD*2A/rs3918290, c.1236G > A/rs75017182, c.2846A > T/rs67376798 and c.1679 T > G/rs56038477) can mitigate the risk of severe fluoropyrimidine toxicity. However, this could not prevent all toxicities. The goal of this study was to identify additional genetic variants, both inside and outside DPYD, that may contribute to fluoropyrimidine toxicity.

METHODS

Biospecimens and data from the Alpe-DPD study were used. Exon sequencing was performed to identify risk variants inside DPYD. In silico and in vitro analyses were used to classify DPYD variants. A genome-wide association study (GWAS) with severe fluoropyrimidine-related toxicity was performed to identify variants outside DPYD. Association with severe toxicity was assessed using matched-pair analyses for the exon sequencing and logistic, Cox, and ordinal regression analyses for GWAS.

RESULTS

Twenty-four non-synonymous, frameshift, and splice site DPYD variants were detected in ten of 986 patients. Seven of these variants (c.1670C > T, c.1913 T > C, c.1925 T > C, c.506delC, c.731A > C, c.1740 + 1G > T, c.763 - 2A > G) were predicted to be deleterious. The carriers of either of these variants showed a trend towards a 2.14-fold (95% CI, 0.41-11.3, P = 0.388) increased risk of severe toxicity compared to matched controls (N = 30). After GWAS of 942 patients, no individual single nucleotide polymorphisms achieved genome-wide significance (P ≤ 5 × 10-8), however, five variants were suggestive of association (P < 5 × 10-6) with severe toxicity.

CONCLUSIONS

Results from DPYD exon sequencing and GWAS analysis did not identify additional genetic variants associated with severe toxicity, which suggests that testing for single markers at a population level currently has limited clinical value. Identifying additional variants on an individual level is still promising to explain fluoropyrimidine-related severe toxicity. In addition, studies with larger samples sizes, in more diverse cohorts are needed to identify potential clinically relevant genetic variants related to severe fluoropyrimidine toxicity.

The role of DPYD and the effects of DPYD suppressor luteolin combined with 5-FU in pancreatic cancer

BACKGROUND

Despite advances in the treatment of cancer, pancreatic ductal adenocarcinoma (PDAC) remains highly lethal due to the lack of effective therapies. Our previous study showed that Luteolin (Lut), a flavonoid, suppressed pancreatocarcinogenesis and reduced the expression of dihydropyrimidine dehydrogenase (DPYD), an enzyme that degrades pyrimidines such as 5-fluorouracil (5-FU), in PDACs. In this study, we investigated the role of DPYD and evaluated the therapeutic potential of combining 5-FU with Lut in PDACs.

METHODS AND RESULTS

PDAC cells overexpressing DPYD showed increased proliferation, and invasiveness, adding to the resistance to 5-FU. The xenograft tumors of DPYD-overexpressing PDAC cells also exhibit enhanced growth and invasion compared to the control xenograft tumors. RNA-seq analysis of the DPYD-overexpressing PDAC xenograft tumors revealed an upregulation of genes associated with metallopeptidase activity-MMP9 and MEP1A. Furthermore, the overexpression of MEP1A in PDAC was associated with invasion. Next, we investigated the combined effects of Lut, a DPYD suppressor, and 5-FU on DPYD-overexpressing xenograft tumors and PDAC of Pdx1-Cre; LSL-KrasG12D/+; Trp53flox/flox(KPPC) mice. Neither single administration of 5-FU nor Lut showed significant inhibitory effects; however, the combined administration of 5-FU and Lut exhibited a significant tumor-suppressive effect in both the xenograft tumors and KPPC models.

CONCLUSION

We have elucidated that DPYD expression contributes to proliferation, invasiveness, and 5-FU resistance, in PDACs. The combination therapy of Lut and 5-FU holds the potential for enhanced efficacy against PDACs.

DPYD genetic polymorphisms in non-European patients with severe fluoropyrimidine-related toxicity: a systematic review

BACKGROUND

Pre-treatment DPYD screening is mandated in the UK and EU to reduce the risk of severe and potentially fatal fluoropyrimidine-related toxicity. Four DPYD gene variants which are more prominently found in Europeans are tested.

METHODS

Our systematic review in patients of non-European ancestry followed PRISMA guidelines to identify relevant articles up to April 2023. Published in silico functional predictions and in vitro functional data were also extracted. We also undertook in silico prediction for all DPYD variants identified.

RESULTS

In 32 studies, published between 1998 and 2022, 53 DPYD variants were evaluated in patients from 12 countries encompassing 5 ethnic groups: African American, East Asian, Latin American, Middle Eastern, and South Asian. One of the 4 common European DPYD variants, c.1905+1G>A, is also present in South Asian, East Asian and Middle Eastern patients with severe fluoropyrimidine-related toxicity. There seems to be relatively strong evidence for the c.557A>G variant, which is found in individuals of African ancestry, but is not currently included in the UK genotyping panel.

CONCLUSION

Extending UK pre-treatment DPYD screening to include variants that are present in some non-European ancestry groups will improve patient safety and reduce race and health inequalities in ethnically diverse societies.

Rapid detection of the irinotecan-related UGT1A1 & 5-fluorouracil related DPYD polymorphism by asymmetric polymerase chain reaction melting curve analysis

BACKGROUND

Determination of DPYD and UGT1A1 polymorphisms prior to 5-fluorouracil and irinotecan therapy is crucial for avoiding severe adverse drug effects. Hence, there is a pressing need for accurate and reliable genotyping methods for the most common DPYD and UGT1A1 polymorphisms. In this study, we introduce a novel polymerase chain reaction (PCR) melting curve analysis method for discriminating DPYD c.1236G > A, c.1679 T > G, c.2846A > T, IVS14 + 1G > A and UGT1A1*1, *28, *6 (G71R) genotypes.

METHODS

Following protocol optimization, this technique was employed to genotype 28 patients, recruited between March 2023 and October 2023, at the First Affiliated Hospital of Xiamen University. These patients included 20 with UGT1A1 *1/*1, 8 with UGT1A1 *1/*28, 4 with UGT1A1 *28/*28, 22 with UGT1A1*6 G/G, 6 with UGT1A1*6 G/A, 4 with UGT1A1*6 A/A, 27 with DPYD(c.1236) G/G, 3 with DPYD(c.1236) G/A, 2 with DPYD(c.1236) A/A, 27 with DPYD(c.1679) T/T, 2 with DPYD(c.1679) T/G, 3 with DPYD(c.1679) G/G, 28 with DPYD(c.2846A/T) A/A, 2 with DPYD(c.2846A/T) A/T, 2 with DPYD(c.2846A/T) T/T, 28 with DPYD(c.IVS14 + 1) G/G, 2 with DPYD(c.IVS14 + 1) G/G, and 2 with DPYD(c.IVS14 + 1) G/G, as well as 3 plasmid standards. Method accuracy was assessed by comparing results with those from Sanger sequencing or Multiplex quantitative PCR(qPCR). Intra- and inter-run precision of melting temperatures (Tms) were calculated to evaluate reliability, and sensitivity was assessed through limit of detection examination.

RESULTS

The new method accurately identified all genotypes and exhibited higher accuracy than Multiplex qPCR. Intra- and inter-run coefficients of variation for Tms were both ≤1.97 %, with standard deviations ≤0.95 °C. The limit of detection was 0.09 ng/μL of input genomic DNA.

CONCLUSION

Our developed PCR melting curve analysis offers accurate, reliable, rapid, simple, and cost-effective detection of DPYD and UGT1A1 polymorphisms. Its application can be easily extended to clinical laboratories equipped with a fluorescent PCR platform.

Different Drug Mobilities in Hydrophobic Cavities of Host-Guest Complexes between β-Cyclodextrin and 5-Fluorouracil at Different Stoichiometries: A Molecular Dynamics Study in Water

Cyclodextrins (CDs) are cyclic oligosaccharides able to form noncovalent water-soluble complexes useful in many different applications for the solubilization, delivery, and greater bioavailability of hydrophobic drugs. The complexation of 5-fluorouracil (5-FU) with natural or synthetic cyclodextrins permits the solubilization of this poorly soluble anticancer drug. In this theoretical work, the complexes between β-CD and 5-FU are investigated using molecular mechanics (MM) and molecular dynamics (MD) simulations in water. The inclusion complexes are formed thanks to the favorable intermolecular interactions between β-CD and 5-FU. Both 1:1 and 1:2 β-CD/5-FU stoichiometries are investigated, providing insight into their interaction geometries and stability over time in water. In the 1:2 β-CD/5-FU complexes, the intermolecular interactions affect the drug's mobility, suggesting a two-step release mechanism: a fast release for the more exposed and hydrated drug molecule, with greater freedom of movement near the β-CD rims, and a slow one for the less-hydrated and well-encapsulated and confined drug. MD simulations study the intermolecular interactions between drugs and specific carriers at the atomistic level, suggesting a possible release mechanism and highlighting the role of the impact of the drug concentration on the kinetics process in water. A comparison with experimental data in the literature provides further insights.

Lethal Capecitabine Toxicity in Patients With Complete Dihydropyrimidine Dehydrogenase Deficiency Due to Ultra-Rare DPYD Variants

A DPD deficiency should be considered in case of severe toxicity even in the absence of common risk variants in DPYD.

Common dihydropyrimidinase ( DPYS ) genetic variations do not predict fluoropyrimidine-related chemotherapy toxicity in a Canadian cohort

Known genetic variations in dihydropyrimidine dehydrogenase (gene name DPYD ) do not fully predict patients at risk for severe fluoropyrimidine-associated chemotherapy toxicity. Dihydropyrimidinase (gene name DPYS ), the second catabolic enzyme in fluoropyrimidine metabolism, has been noted as a potential determinant of variation in fluoropyrimidine metabolism and response. In this study, we genotyped for DPYS c.-1T>C (rs2959023), c.265-58T>C (rs2669429) and c.541C>T (rs36027551) in a Canadian cohort of 248 patients who were wild type for Clinical Pharmacogenetics Implementation Consortium recommended DPYD variants and had received a standard dose of fluoropyrimidine chemotherapy. None of our patients were found to carry the DPYS c.541C>T variant, while the minor allele frequencies were 63% and 54% for c.-1T>C and c.265-58T>C, respectively. There was no association between DPYS c.-1T>C wild type and heterozygote [odds ratio (OR) (95% confidence interval, CI) = 1.10 (0.51-2.40)] or homozygote variant carriers [OR (95% CI) = 1.22 (0.55-2.70)], or between DPYS c.265-58T>C wild-type patients and heterozygote [OR (95% CI) = 0.93 (0.48-1.80)] or homozygote variant carriers [OR (95% CI) = 0.76 (0.37-1.55)] in terms of fluoropyrimidine-associated toxicity. Therefore, in our cohort of mostly Caucasian Canadians, genetic variations in DPYS do not appear to be a significant contributor to severe fluoropyrimidine-associated toxicity.

Attenuation effect of a polysaccharide from large leaf yellow tea by activating autophagy

Chemotherapy, the most common class of anticancer drugs, is considerably limited owing to its adverse side effects. In this study, we aimed to evaluate the protective effect and mechanism of action of large-leaf yellow tea polysaccharides (ULYTP-1, 1.29 × 104 Da) against chemotherapeutic 5-fluorouracil (5-Fu). Structural characterisation revealed that ULYTP-1 was a β-galactopyranouronic acid. Furthermore, ULYTP-1 promoted autolysosome formation, activating autophagy and reducing the oxidative stress and inflammation caused by 5-Fu. Our in vivo study of 4 T1 tumour-bearing mice revealed that ULYTP-1 also attenuated 5-Fu toxicity through modulation of the gut microbiota. Moreover, ULYTP-1 effectively protected immune organs and the liver from 5-Fu toxicity, while promoting its tumour-inhibitory properties. The current findings provide a new strategy for optimising chemotherapy regimens in the clinic.

A novel large intragenic DPYD deletion causing dihydropyrimidine dehydrogenase deficiency: a case report

BACKGROUND

Dihydropyrimidine dehydrogenase (DPD), is the initial and rate-limiting enzyme in the catabolic pathway of pyrimidines. Deleterious variants in the DPYD gene cause DPD deficiency, a rare autosomal recessive disorder. The clinical spectrum of affected individuals is wide ranging from asymptomatic to severely affected patients presenting with intellectual disability, motor retardation, developmental delay and seizures. DPD is also important as the main enzyme in the catabolism of 5-fluorouracil (5-FU) which is extensively used as a chemotherapeutic agent. Even in the absence of clinical symptoms, individuals with either complete or partial DPD deficiency face a high risk of severe and even fatal fluoropyrimidine-associated toxicity. The identification of causative genetic variants in DPYD is therefore gaining increasing attention due to their potential use as predictive markers of fluoropyrimidine toxicity.

METHODS

A male infant patient displaying biochemical features of DPD deficiency was investigated by clinical exome sequencing. Bioinformatics tools were used for data analysis and results were confirmed by MLPA and Sanger sequencing.

RESULTS

A novel intragenic deletion of 71.2 kb in the DPYD gene was identified in homozygosity. The deletion, DPYD(NM_000110.4):c.850 + 23455_1128 + 8811del, eliminates exons 9 and 10 and may have resulted from a non-homologous end-joining event, as suggested by in silico analysis.

CONCLUSIONS

The study expands the spectrum of DPYD variants associated with DPD deficiency. Furthermore, it raises the concern that patients at risk for fluoropyrimidine toxicity due to DPYD deletions could be missed during pre-treatment genetic testing for the currently recommended single nucleotide polymorphisms.

Dihydropyrimidine dehydrogenase gene variants for predicting grade 4-5 fluoropyrimidine-induced toxicity: FUSAFE individual patient data meta-analysis

BACKGROUND

Dihydropyrimidine dehydrogenase (DPD) deficiency is the main known cause of life-threatening fluoropyrimidine (FP)-induced toxicities. We conducted a meta-analysis on individual patient data to assess the contribution of deleterious DPYD variants *2A/D949V/*13/HapB3 (recommended by EMA) and clinical factors, for predicting G4-5 toxicity.

METHODS

Study eligibility criteria included recruitment of Caucasian patients without DPD-based FP-dose adjustment. Main endpoint was 12-week haematological or digestive G4-5 toxicity. The value of DPYD variants *2A/p.D949V/*13 merged, HapB3, and MIR27A rs895819 was evaluated using multivariable logistic models (AUC).

RESULTS

Among 25 eligible studies, complete clinical variables and primary endpoint were available in 15 studies (8733 patients). Twelve-week G4-5 toxicity prevalence was 7.3% (641 events). The clinical model included age, sex, body mass index, schedule of FP-administration, concomitant anticancer drugs. Adding *2A/p.D949V/*13 variants (at least one allele, prevalence 2.2%, OR 9.5 [95%CI 6.7-13.5]) significantly improved the model (p < 0.0001). The addition of HapB3 (prevalence 4.0%, 98.6% heterozygous), in spite of significant association with toxicity (OR 1.8 [95%CI 1.2-2.7]), did not improve the model. MIR27A rs895819 was not associated with toxicity, irrespective of DPYD variants.

CONCLUSIONS

FUSAFE meta-analysis highlights the major relevance of DPYD *2A/p.D949V/*13 combined with clinical variables to identify patients at risk of very severe FP-related toxicity.

3D multi-cell-type liver organoids: A new model of non-alcoholic fatty liver disease for drug safety assessments

The development of in vitro models that recapitulate critical liver functions is essential for accurate assessments of drug toxicity. Although liver organoids can be used for drug discovery and toxicology, they are limited by (i) the lack of expression and activity of xenobiotic-metabolizing enzymes, and (ii) the difficulty of mimicking non-alcoholic fatty liver disease (NAFLD, which influences the expression of these enzymes) in vitro. Here, we generated three-dimensional multi-cell-type liver organoids (hereafter "HML organoids") from HepaRG cells, primary human macrophages, and hepatic-stellate-cell-derived LX-2 cells. We also developed an NAFLD model by culturing HML organoids for 9 days with a mixture of stearic and oleic acids. The exposed organoids showed typical features of steatosis and expressed fibrosis markers. We subsequently used HML and NAFLD-HML organoids to model drug-induced liver injury. By estimating the IC50 and benchmark doses, we were able to improve the in vitro detection of drugs likely to be toxic in fatty livers. Thus, HML and NAFLD-HML organoids exhibited most of the liver's functions and are relevant in vitro models of drug metabolism, drug toxicity, and adverse drug event in NAFLD.

Survival of Patients With Cancer With DPYD Variant Alleles and Dose-Individualized Fluoropyrimidine Therapy-A Matched-Pair Analysis

PURPOSE

DPYD-guided fluoropyrimidine dosing improves patient safety in carriers of DPYD variant alleles. However, the impact on treatment outcome in these patients is largely unknown. Therefore, progression-free survival (PFS) and overall survival (OS) were compared between DPYD variant carriers treated with a reduced dose and DPYD wild-type controls receiving a full fluoropyrimidine dose in a retrospective matched-pair survival analysis.

METHODS

Data from a prospective multicenter study (ClinicalTrials.gov identifier: NCT02324452) in which DPYD variant carriers received a 25% (c.1236G>A and c.2846A>T) or 50% (DPYD*2A and c.1679T>G) reduced dose and data from DPYD variant carriers treated with a similarly reduced dose of fluoropyrimidines identified during routine clinical care were obtained. Each DPYD variant carrier was matched to three DPYD wild-type controls treated with a standard dose. Survival analyses were performed using Kaplan-Meier estimates and Cox regression.

RESULTS

In total, 156 DPYD variant carriers and 775 DPYD wild-type controls were available for analysis. Sixty-one c.1236G>A, 25 DPYD*2A, 13 c.2846A>T, and-when pooled-93 DPYD variant carriers could each be matched to three unique DPYD wild-type controls. For pooled DPYD variant carriers, PFS (hazard ratio [HR], 1.23; 95% CI, 1.00 to 1.51; P = .053) and OS (HR, 0.95; 95% CI, 0.75 to 1.51; P = .698) were not negatively affected by DPYD-guided dose individualization. In the subgroup analyses, a shorter PFS (HR, 1.43; 95% CI, 1.10 to 1.86; P = .007) was found in c.1236G>A variant carriers, whereas no differences were found for DPYD*2A and c.2846A>T carriers.

CONCLUSION

In this exploratory analysis, DPYD-guided fluoropyrimidine dosing does not negatively affect PFS and OS in pooled DPYD variant carriers. Close monitoring with early dose modifications based on toxicity is recommended, especially for c.1236G>A carriers receiving a reduced starting dose.

Implementation of pharmacogenetic testing in oncology: DPYD-guided dosing to prevent fluoropyrimidine toxicity in British Columbia

Background: Fluoropyrimidine toxicity is often due to variations in the gene (DPYD) encoding dihydropyrimidine dehydrogenase (DPD). DPYD genotyping can be used to adjust doses to reduce the likelihood of fluoropyrimidine toxicity while maintaining therapeutically effective drug levels. Methods: A multiplex QPCR assay was locally developed to allow genotyping for six DPYD variants. The test was offered prospectively for all patients starting on fluoropyrimidines at the BC Cancer Centre in Vancouver and then across B.C., Canada as well as retrospectively for patients suspected to have had an adverse reaction to therapy. Dose adjustments were made for variant carriers. The incidence of toxicity in the first three cycles was compared between DPYD variant allele carriers and non-variant carriers. Subsequent to an initial implementation phase, this test was made available province-wide. Results: In 9 months, 186 patients were tested and 14 were found to be heterozygous variant carriers. Fluoropyrimidine-related toxicity was higher in DPYD variant carriers. Of 127 non-variant carriers who have completed chemotherapy, 18 (14%) experienced severe (grade ≥3, Common Terminology Criteria for Adverse Events version 5.0). Of note, 22% (3 patients) of the variant carriers experienced severe toxicity even after DPYD-guided dose reductions. For one of these carriers who experienced severe thrombocytopenia within the first week, DPYD testing likely prevented lethal toxicity. In DPYD variant carriers who tolerate reduced doses, a later 25% increase led to chemotherapy discontinuation. As a result, a recommendation was made to clinicians based on available literature and expert opinion specifying that variant carriers who tolerated two cycles without toxicity can have a dose escalation of only 10%. Conclusion: DPYD-guided dose reductions were a feasible and acceptable method of preventing severe toxicity in DPYD variant carriers. Even with dose reductions, there were variant carriers who still experienced severe fluoropyrimidine toxicity, highlighting the importance of adhering to guideline-recommended dose reductions. Following the completion of the pilot phase of this study, DPYD genotyping was made available province-wide in British Columbia.

Oral uracil-tegafur compared with intravenous chemotherapy as adjuvant therapy for resected early-stage non-small cell lung cancer patients

BACKGROUND

Studies comparing the effectiveness of either adjuvant oral uracil-tegafur (UFT) or intravenous chemotherapy on early-stage (stage I and II) non-small cell lung cancer (NSCLC) patients treated with complete surgical treatment remain limited.

METHODS

From January 2011 to December 2017, patients with early-stage NSCLC (defined as tumor size >3 cm without mediastinal lymph node involvement or any distant metastasis) receiving either adjuvant oral UFT or intravenous chemotherapy after surgical resection were identified from the Taiwan Cancer Registry. Overall survival (OS) and relapse-free survival (RFS) were the primary and secondary outcomes, respectively. Propensity matching was used for controlling confounders.

RESULTS

A total of 840 patients receiving adjuvant therapy after surgery (including 595 oral UFT and 245 intravenous chemotherapy) were enrolled. Before matching, patients using oral UFT had significantly longer OS (HR: 0.69, 95% CI: 0.49-0.98, p = 0.0387) and RFS (HR: 0.79, 95% CI: 0.61-0.97, p = 0.0392) than those with intravenous chemotherapy. A matched cohort of 352 patients was created using 1:1 propensity score-matching. In the Cox regression analysis, the UFT and the matched chemotherapy groups had similar OS (HR: 0.80, 95% CI: 0.48-1.32, p = 0.3753) and RFS (HR: 0.98, 95% CI: 0.72-1.34, p = 0.9149). Among subgroup analysis, oral UFT use was associated with longer RFS among the subgroups of non-drinker (HR: 0.66, 95% CI: 0.34-0.99, p = 0.0478) and patients with stage IB disease (HR: 0.67, 95% CI: 0.42-0.97, p = 0.0341).

CONCLUSIONS

This population-based study in the real-world setting of Taiwan demonstrates comparable effectiveness between oral UFT and intravenous chemotherapy in terms of clinical outcomes for early-stage NSCLC patients after surgery.

Physiologically Based Pharmacokinetic Modeling for Prediction of 5-FU Pharmacokinetics in Cancer Patients with Hepatic Impairment After 5-FU and Capecitabine Administration

PURPOSE

5-fluorouracil (5-FU) and its prodrug capecitabine are commonly prescribed anti-tumor medications. We aimed to establish physiologically based pharmacokinetic (PBPK) models of capecitabine-metabolites and 5-FU-metabolites to describe their pharmacokinetics in tumor and plasma of cancer patients with liver impairment.

METHODS

Models including the cancer compartment were developed in PK-Sim® and MoBi® and evaluated by R programming language with 25 oral capecitabine and 18 intravenous 5-FU studies for cancer patients with and without liver impairment.

RESULTS

The PBPK models were constructed successfully as most simulated Cmax and AUClast were within two-fold error of observed values. The simulated alterations of tumor 5-FU Cmax and AUClast in cancer patients with severe liver injury compared with normal liver function were 1.956 and 3.676 after oral administration of capecitabine, but no significant alteration was observed after intravenous injection of 5-FU. Besides, 5-FU concentration in tumor tissue increases with higher tumor blood flow but not tumor size. Sensitivity analysis revealed that dihydropyrimidine dehydrogenase (DPD) and other metabolic enzymes' activity, capecitabine intestinal permeability and plasma protein scale factor played a vital role in tumor and plasma 5-FU pharmacokinetics.

CONCLUSIONS

PBPK model prediction suggests no dosage adaption of capecitabine or 5-FU is required for cancer patients with hepatic impairment but it would be reduced when the toxic reaction is observed. Furthermore, tumor blood flow rate rather than tumor size is critical for 5-FU concentration in tumor. In summary, these models could predict pharmacokinetics of 5-FU in tumor in cancer patients with varying characteristics in different scenarios.

Colorectal cancer and therapy response: a focus on the main mechanisms involved

Introduction

The latest GLOBOCAN 2021 reports that colorectal cancer (CRC) is the second leading cause of cancer-related death worldwide. Most CRC cases are sporadic and associated with several risk factors, including lifestyle habits, gut dysbiosis, chronic inflammation, and oxidative stress.

Aim

To summarize the biology of CRC and discuss current therapeutic interventions designed to counteract CRC development and to overcome chemoresistance.

Methods

Literature searches were conducted using PubMed and focusing the attention on the keywords such as "Current treatment of CRC" or "chemoresistance and CRC" or "oxidative stress and CRC" or "novel drug delivery approaches in cancer" or "immunotherapy in CRC" or "gut microbiota in CRC" or "systematic review and meta-analysis of randomized controlled trials" or "CSCs and CRC". The citations included in the search ranged from September 1988 to December 2022. An additional search was carried out using the clinical trial database.

Results

Rounds of adjuvant therapies, including radiotherapy, chemotherapy, and immunotherapy are commonly planned to reduce cancer recurrence after surgery (stage II and stage III CRC patients) and to improve overall survival (stage IV). 5-fluorouracil-based chemotherapy in combination with other cytotoxic drugs, is the mainstay to treat CRC. However, the onset of the inherent or acquired resistance and the presence of chemoresistant cancer stem cells drastically reduce the efficacy. On the other hand, the genetic-molecular heterogeneity of CRC often precludes also the efficacy of new therapeutic approaches such as immunotherapies. Therefore, the CRC complexity made of natural or acquired multidrug resistance has made it necessary the search for new druggable targets and new delivery systems.

Conclusion

Further knowledge of the underlying CRC mechanisms and a comprehensive overview of current therapeutic opportunities can provide the basis for identifying pharmacological and biological barriers that render therapies ineffective and for identifying new potential biomarkers and therapeutic targets for advanced and aggressive CRC.

Potential therapeutic effects of different mouthwashes for alleviation and treatment of oral complications of 5-fluorouracil-based chemotherapy in patients with colon cancer

OBJECTIVE

The primary endpoint of the present study was to assess the potential therapeutic effects of three different mouthwashes for alleviation and treatment of oral complications (OCs). The secondary endpoint was to assess patients' perceptions and daily functional activities after therapy of OCs in patients with colon cancer receiving 5-fluorouracil (5-FU)-based chemotherapy regimens.

METHODS

A prospective, randomised controlled study carried out on 90 patients with colon cancer eligible for 5-FU-based chemotherapy regimens at the oncology centre, Istanbul, Turkey. Patients were randomly randomised into three groups (30 patients in each group) and received a single mouthwash. The first group (group A) received benzydamine at a dose of 15 mL; the second group (group B) received sodium bicarbonate at a dose of 1.2-2.4 g in 240 mL of water; and the third group (group C) received glutamine suspension 10 g. Patients were assessed for the occurrence of oral complications based on the WHO scale for oral mucosa evaluation and National Cancer Institute Common Terminology Criteria for Adverse Events version 4.0. Oral pain was assessed using a visual analogue scale alongside assessment of patients' perceptions and daily functional activities based on the Rotterdam Symptom Checklist.

RESULTS

A total of 119 oral complications were reported, including mouth dryness (n=56, 47.1%), oral mucositis (n=31, 26.1%) and oral pain (n=32, 26.8%). At the end of the study, patients of group A and group B significantly suffered from mouth dryness (p=0.0001), oral mucositis (p=0.029) and oral pain (p=0.039) compared with patients in group C. Although there was no significant change, group C patients showed a slight improvement in psychological discomfort, activity levels and quality of life at the end of the study.

CONCLUSION

The present study showed that benzydamine and sodium bicarbonate mouthwashes were significantly less effective for the alleviation and treatment of oral complications compared with glutamine among patients with colon cancer receiving 5-FU-based chemotherapy regimens.

Case report: 5-Fluorouracil treatment in patient with an important partial DPD deficiency

Esophageal cancer is a cancer with poor prognosis and the standard 1^st line treatment for metastatic or recurrent EC is systemic chemotherapy with doublet chemotherapy based on platinum and 5-fluorouracil (5-FU). However, 5-FU could be a source of severe treatment-related toxicities due to deficiency of dihydropyrimidine dehydrogenase (DPD). In this case report, a 74-year-old man with metastatic esophageal cancer was found to have partial DPD deficiency based on uracilemia measurements (about 90 ng/mL). Despite this, 5-FU was safely administered thanks to therapeutic drug monitoring (TDM). The case report highlights the importance of TDM in administering 5-FU to patients with partial DPD deficiency, as it allows individualized dosing and prevents severe toxicity.

Recurrent cardiotoxicity in a fluoropyrimidine treated cancer patient - case report and practical recommendations

Fluoropyrimidines remain some of the most used chemotherapeutics, despite the appearance in the therapeutic arsenal of targeted therapy and immunotherapy. Fluropyrimidines related cardiotoxicity is an undesirable adverse event and affects almost 20% of patients. The mechanisms of fluoropyrimidine toxicity are closely related to deficient allelic variants of DPYD, but considering the low penetrance and interindividual variability, not all adverse reactions are explained by their presence. In this case, we report a patient with recurrent fluoropyrimidine toxicity without a deficient allelic variant and how this case was managed by the oncologist and cardiologist, considering the need to use fluoropyrimidine in the treatment.

Ten-year experience with pharmacogenetic testing for DPYD in a national cancer center in Italy: Lessons learned on the path to implementation

Background: Awareness about the importance of implementing DPYD pharmacogenetics in clinical practice to prevent severe side effects related to the use of fluoropyrimidines has been raised over the years. Since 2012 at the National Cancer Institute, CRO-Aviano (Italy), a diagnostic DPYD genotyping service was set up. Purpose: This study aims to describe the evolution of DPYD diagnostic activity at our center over the last 10 years as a case example of a successful introduction of pharmacogenetic testing in clinical practice. Methods: Data related to the diagnostic activity of in-and out-patients referred to our service between January 2012 and December 2022 were retrieved from the hospital database. Results: DPYD diagnostic activity at our center has greatly evolved over the years, shifting gradually from a post-toxicity to a pre-treatment approach. Development of pharmacogenetic guidelines by national and international consortia, genotyping, and IT technology evolution have impacted DPYD testing uptake in the clinics. Our participation in a large prospective implementation study (Ubiquitous Pharmacogenomics) increased health practitioners' and patients' awareness of pharmacogenetic matters and provided additional standardized infrastructures for genotyping and reporting. Nationwide test reimbursement together with recommendations by regulatory agencies in Europe and Italy in 2020 definitely changed the clinical practice guidelines of fluoropyrimidines prescription. A dramatic increase in the number of pre-treatment DPYD genotyping and in the coverage of new fluoropyrimidine prescriptions was noticed by the last year of observation (2022). Conclusion: The long path to a successful DPYD testing implementation in the clinical practice of a National Cancer Center in Italy demonstrated that the development of pharmacogenetic guidelines and genotyping infrastructure standardization as well as capillary training and education activity for all the potential stakeholders are fundamental. However, only national health politics of test reimbursement and clear recommendations by drug regulatory agencies will definitely move the field forward.

Current diagnostic and clinical issues of screening for dihydropyrimidine dehydrogenase deficiency

Fluoropyrimidine drugs (FP) are the backbone of many chemotherapy protocols for treating solid tumours. The rate-limiting step of fluoropyrimidine catabolism is dihydropyrimidine dehydrogenase (DPD), and deficiency in DPD activity can result in severe and even fatal toxicity. In this review, we survey the evidence-based pharmacogenetics and therapeutic recommendations regarding DPYD (the gene encoding DPD) genotyping and DPD phenotyping to prevent toxicity and optimize dosing adaptation before FP administration. The French experience of mandatory DPD-deficiency screening prior to initiating FP is discussed.

Quantitative impact of pre-analytical process on plasma uracil when testing for dihydropyrimidine dehydrogenase deficiency

AIMS

Determining dihydropyrimidine dehydrogenase (DPD) activity by measuring patient's uracil (U) plasma concentration is mandatory before fluoropyrimidine (FP) administration in France. In this study, we aimed to refine the pre-analytical recommendations for determining U and dihydrouracil (UH₂ ) concentrations, as they are essential in reliable DPD-deficiency testing.

METHODS

U and UH₂ concentrations were collected from 14 hospital laboratories. Stability in whole blood and plasma after centrifugation, the type of anticoagulant and long-term plasma storage were evaluated. The variation induced by time and temperature was calculated and compared to an acceptability range of ±20%. Inter-occasion variability (IOV) of U and UH₂ was assessed in 573 patients double sampled for DPD-deficiency testing.

RESULTS

Storage of blood samples before centrifugation at room temperature (RT) should not exceed 1 h, whereas cold (+4°C) storage maintains the stability of uracil after 5 hours. For patients correctly double sampled, IOV of U reached 22.4% for U (SD = 17.9%, range = 0-99%). Notably, 17% of them were assigned with a different phenotype (normal or DPD-deficient) based on the analysis of their two samples. For those having at least one non-compliant sample, this percentage increased up to 33.8%. The moment of blood collection did not affect the DPD phenotyping result.

CONCLUSION

Caution should be taken when interpreting U concentrations if the time before centrifugation exceeds 1 hour at RT, since it rises significantly afterwards. Not respecting the pre-analytical conditions for DPD phenotyping increases the risk of DPD status misclassification.

Functional Characterization of 12 Dihydropyrimidinase Allelic Variants in Japanese Individuals for the Prediction of 5-Fluorouracil Treatment-Related Toxicity

The drug 5-fluorouracil (5-FU) is the first-choice chemotherapeutic agent against advanced-stage cancers. However, 10% to 30% of treated patients experience grade 3 to 4 toxicity. The deficiency of dihydropyrimidinase (DHPase), which catalyzes the second step of the 5-FU degradation pathway, is correlated with the risk of developing toxicity. Thus, genetic polymorphisms within DPYS, the DHPase-encoding gene, could potentially serve as predictors of severe 5-FU-related toxicity. We identified 12 novel DPYS variants in 3554 Japanese individuals, but the effects of these mutations on function remain unknown. In the current study, we performed in vitro enzymatic analyses of the 12 newly identified DHPase variants. Dihydrouracil or dihydro-5-FU hydrolytic ring-opening kinetic parameters, Km and Vmax , and intrinsic clearance (CLint = Vmax /Km ) of the wild-type DHPase and eight variants were measured. Five of these variants (R118Q, H295R, T418I, Y448H, and T513A) showed significantly reduced CLint compared with that in the wild-type. The parameters for the remaining four variants (V59F, D81H, T136M, and R490H) could not be determined as dihydrouracil and dihydro-5-FU hydrolytic ring-opening activity was undetectable. We also determined DHPase variant protein stability using cycloheximide and bortezomib. The mechanism underlying the observed changes in the kinetic parameters was clarified using blue-native polyacrylamide gel electrophoresis and three-dimensional structural modeling. The results suggested that the decrease or loss of DHPase enzymatic activity was due to reduced stability and oligomerization of DHPase variant proteins. Our findings support the use of DPYS polymorphisms as novel pharmacogenomic markers for predicting severe 5-FU-related toxicity in the Japanese population. SIGNIFICANCE STATEMENT: DHPase contributes to the degradation of 5-fluorouracil, and genetic polymorphisms that cause decreased activity of DHPase can cause severe toxicity. In this study, we performed functional analysis of 12 DHPase variants in the Japanese population and identified 9 genetic polymorphisms that cause reduced DHPase function. In addition, we found that the ability to oligomerize and the conformation of the active site are important for the enzymatic activity of DHPase.

Renal impairment and abnormal liver function tests in pre-therapeutic phenotype-based DPD deficiency screening using uracilemia: a comprehensive population-based study in 1138 patients

Background

Dihydropyrimidine dehydrogenase (DPD) deficiency screening is a pre-therapeutic standard to prevent severe fluoropyrimidine-related toxicity. Although several screening methods exist, the accuracy of their results remains debatable. In France, the uracilemia measurement is considered the standard in DPD deficiency screening. The objective of this study was to describe the hyperuracilemia (⩾16 ng/mL) rate and investigate the influence of hepatic and renal impairment in uracilemia measurements since the guidelines were implemented.

Patients and methods

Using a cohort of 1138 patients screened between 18 October 2018 and 18 October 2021, basic demographic characteristics, date of blood sampling, and potential biological confounders including liver function tests [aspartate aminotransaminase (AST), alanine aminotransaminase (ALT), gamma-glutamyl transferase (γGT), alkaline phosphatase (ALP), and bilirubin] and estimated glomerular filtration rate (eGFR) were collected. The second same-patient uracilemia analysis was also performed. Temporal change was graphically represented while potential confounders were stratified to show linearity when suspected.

Results

Hyperuracilemia was diagnosed in 12.7% (n = 150) samples with 6.7%, 5.4%, 0.5%, and 0.08% between 16 and 20 ng/mL, 20 and 50 ng/mL, 50 and 150 ng/mL, and >150 ng/mL, respectively. The median uracilemia concentration was 9.4 ng/mL (range: 1.2 and 172.3 ng/mL) and the monthly hyperuracilemia rate decreased steadily from >30% to around 9%. Older age, normalized AST, γGT, ALP results, bilirubin levels, and decreased eGFR were linearly associated with higher plasma uracil concentrations (all p < 0.001). In the adjusted multivariate linear model, AST, eGFR, and ALP remained associated with uracilemia (p < 0.05). When measured twice in 39 patients, the median uracilemia rate of change was -2.5%, which subsequently changed the diagnosis in nine patients (23.1%).

Conclusions

Better respect of pre-analytical conditions may explain the steady decrease in monthly hyperuracilemia rates over the 3 years. Elevated AST, ALP levels, and reduced eGFR could induce a false increase in uracilemia and second uracilemia measurements modified the first DPD deficiency diagnosis in almost 25% of the patients.

Identification of DPYD variants and estimation of uracil and dihydrouracil in a healthy Indian population

Aim: This study aimed to identify DPYD variants and the related but previously unexplored phenotype (plasma uracil, dihydrouracil [DHU], and the DHU-to-uracil ratio) in a healthy adult Indian population. Methods: Healthy adult volunteers (n = 100) had their uracil and DHU levels measured and were genotyped for selected variants. Results: Among the nine variants studied, c.1906-14763G>A and c.85T>C were the most prevalent. Participants with any of the variants except for c.85T>C and c.1627A>G had a significantly lower DHU-to-uracil ratio and those with c.1905+1G>A variant had significantly increased uracil concentration compared with wild type. Conclusion: Participants with five variants were identified as having altered phenotypic measures, and 40% of the intermediate metabolizers had their phenotype in the terminal population percentiles.

The cancer chemotherapeutic 5-fluorouracil is a potent Fusobacterium nucleatum inhibitor and its activity is modified by intratumoral microbiota

Fusobacterium nucleatum (Fn) is a dominant bacterial species in colorectal cancer (CRC) tissue that is associated with cancer progression and poorer patient prognosis. Following a small-molecule inhibitor screen of 1,846 bioactive compounds against a Fn CRC isolate, we find that 15% of inhibitors are antineoplastic agents including fluoropyrimidines. Validation of these findings reveals that 5-fluorouracil (5-FU), a first-line CRC chemotherapeutic, is a potent inhibitor of Fn CRC isolates. We also identify members of the intratumoral microbiota, including Escherichia coli, that are resistant to 5-FU. Further, CRC E. coli isolates can modify 5-FU and relieve 5-FU toxicity toward otherwise-sensitive Fn and human CRC epithelial cells. Lastly, we demonstrate that ex vivo patient CRC tumor microbiota undergo community disruption after 5-FU exposure and have the potential to deplete 5-FU levels, reducing local drug efficacy. Together, these observations argue for further investigation into the role of the CRC intratumoral microbiota in patient response to chemotherapy.

Dihydropyrimidine Dehydrogenase-Mediated Resistance to 5-Fluorouracil: Mechanistic Investigation and Solution

5-Fluorouracil (5-FU) is one of the most widely used chemotherapeutics for the treatment of cancers associated with the aerodigestive tract, breast, and colorectal system. The efficacy of 5-FU is majorly affected by dihydropyrimidine dehydrogenase (DPD) as it degrades more than 80% of administered 5-FU into an inactive metabolite, dihydrofluorouracil. Herein we discuss the molecular mechanism of this inactivation by analyzing the interaction pattern and electrostatic complementarity of the DPD-5-FU complex. The basis of DPD overexpression in cancer cell lines due to significantly distinct levels of the miRNAs (miR-134, miR-27b, and miR-27a) compared to normal cells has also been outlined. Additionally, some kinases including sphingosine kinase 2 (SphK2) have been reported to correlate with DPD expression. Currently, to address this problem various strategies are reported in the literature, including 5-FU analogues (bypass the DPD-mediated inactivation), DPD downregulators (regulate the DPD expression levels in tumors), inhibitors (as promising adjuvants), and formulation development loaded with 5-FU (liposomes, nanoparticles, nanogels, etc.), which are briefly discussed in this Review.

Impact of Guidelines Regarding Dihydropyrimidine Dehydrogenase (DPD) Deficiency Screening Using Uracil-Based Phenotyping on the Reduction of Severe Side Effect of 5-Fluorouracil-Based Chemotherapy: A Propension Score Analysis

Dihydropyrimidine dehydrogenase (DPD) deficiency is associated with severe fluoropyrimidines-induced toxicity. As of September 2018, French recommendations call for screening for DPD deficiency by plasma uracil quantification prior to all fluoropyrimidine-based chemotherapy. A dose reduction of fluoropyrimidine is recommended when uracil concentration is equal to or greater than 16 ng/mL. This matched retrospective study assessed the impact of DPD screening on the reduction of severe side effects and on the management of DPD-deficient patients. Using a propensity score, we balanced the factors influencing 5-Fluorouracil (5-FU) toxicity. Then, the severity scores (G3 and G4 severity as well as their frequency) of patients who did not benefit from DPD screening were compared with those of patients who benefited from DPD screening for each treatment cycle (from 1 to 4). Among 349 screened patients, 198 treated patients were included. Among them, 31 (15.7%) had DPD deficiency (median uracilemia 19.8 ng/mL (range: 16.1−172.3)). The median toxicity severity score was higher in the unscreened group for each treatment cycle (0 vs. 1, p < 0.001 at each cycle from 1 to 4) as well as the cumulative score during all courses of treatment (p = 0.028). DPD-deficient patients received a significantly lower dose of 5-FU (p < 0.001). This study suggests that pretherapeutic plasmatic uracil assessment, along with 5-FU dosage adjustment, may be beneficial in reducing 5-FU toxicity in real-life patients.

Systematic identification of intron retention associated variants from massive publicly available transcriptome sequencing data

Many disease-associated genomic variants disrupt gene function through abnormal splicing. With the advancement of genomic medicine, identifying disease-associated splicing associated variants has become more important than ever. Most bioinformatics approaches to detect splicing associated variants require both genome and transcriptomic data. However, there are not many datasets where both of them are available. In this study, we develop a methodology to detect genomic variants that cause splicing changes (more specifically, intron retention), using transcriptome sequencing data alone. After evaluating its sensitivity and precision, we apply it to 230,988 transcriptome sequencing data from the publicly available repository and identified 27,049 intron retention associated variants (IRAVs). In addition, by exploring positional relationships with variants registered in existing disease databases, we extract 3,000 putative disease-associated IRAVs, which range from cancer drivers to variants linked with autosomal recessive disorders. The in-silico screening framework demonstrates the possibility of near-automatically acquiring medical knowledge, making the most of massively accumulated publicly available sequencing data. Collections of IRAVs identified in this study are available through IRAVDB ( https://iravdb.io/ ).

Cost-effectiveness of DPYD Genotyping Prior to Fluoropyrimidine-based Adjuvant Chemotherapy for Colon Cancer

BACKGROUND

Adjuvant fluoropyrimidine-based chemotherapy substantially reduces recurrence and mortality after resection of stage 3 colon cancer. While standard doses of 5-fluorouracil and capecitabine are safe for most patients, the risk of severe toxicity is increased for the approximately 6% of patients with dihydropyimidine dehydrogenase (DPD) deficiency caused by pathogenic DPYD gene variants. Pre-treatment screening for pathogenic DPYD gene variants reduces severe toxicity but has not been widely adopted in the United States.

METHODS

We conducted a cost-effectiveness analysis of DPYD genotyping prior to fluoropyrimidine-based adjuvant chemotherapy for stage 3 colon cancer, covering the c.1129-5923C>G (HapB3), c.1679T>G (*13), c.1905+1G>A (*2A), and c.2846A>T gene variants. We used a Markov model with a 5-year horizon, taking a United States healthcare perspective. Simulated patients with pathogenic DPYD gene variants received reduced-dose fluoropyrimidine chemotherapy. The primary outcome was the incremental cost-effectiveness ratio (ICER) for DPYD genotyping.

RESULTS

Compared with no screening for DPD deficiency, DPYD genotyping increased per-patient costs by $78 and improved survival by 0.0038 quality-adjusted life years (QALYs), leading to an ICER of $20,506/QALY. In 1-way sensitivity analyses, The ICER exceeded $50,000 per QALY when the cost of the DPYD genotyping assay was greater than $286. In probabilistic sensitivity analysis using a willingness-to-pay threshold of $50,000/QALY DPYD genotyping was preferred to no screening in 96.2% of iterations.

CONCLUSION

Among patients receiving adjuvant chemotherapy for stage 3 colon cancer, screening for DPD deficiency with DPYD genotyping is a cost-effective strategy for preventing infrequent but severe and sometimes fatal toxicities of fluoropyrimidine chemotherapy.

Genotype-based chemotherapy for patients with gastrointestinal tumors: focus on oxaliplatin, irinotecan, and fluoropyrimidines

This review aimed to summarize the pharmacogenetic studies of the most commonly used drugs in the chemotherapy of gastrointestinal (GI) tumors: oxaliplatin, irinotecan, and fluoropyrimidines. So far, it has not been possible to develop an effective genotype-based approach for oxaliplatin. More and more evidence is emerging in favor of the fact that the choice of a dose of fluorouracil based on pharmacogenetic testing according to DPYD*2A, can be not only effective but also cost-effective. Additional, well-planned trials of the UGT1A1 genotype-based approach to irinotecan therapy are predicted to reduce adverse drug events in people with the UGT1A1*28/*28 genotypes and improve treatment efficacy in the rest of the patients, which might be cost-effective.

Bladder-sparing (chemo)radiotherapy in elderly patients with muscle-invasive bladder cancer: a retrospective cohort study

BACKGROUND

Organ-sparing treatment for muscle-invasive bladder cancer by maximal transurethral removal of the tumor (TURB) followed by chemoradiation (CRT) has shown promising results in recent studies, and is therefore considered to be an acceptable alternative for the standard of radical cystectomy (RC) in selected patients. We report on outcomes in a single-center, retrospective CRT cohort in comparison to a RC and radiotherapy only (RT) cohort.

PATIENTS AND METHODS

The patient population included n = 84 CRT patients, n = 93 RC patients, and n = 95 RT patients. Primary endpoints were local control (LC) up to 2 years and overall survival (OS) up to 5 years. Cox regression was performed to determine risk factors for LC and OS in the CRT group. Acute genito-urinary (GU) and gastro-intestinal (GI) toxicity were scored with CTCAE version 4 for the RT and CRT cohort. Logistic regression was used to determine risk factors for toxicity. We followed the EQUATOR guidelines for reporting, using the STROBE checklist for observational research.

RESULTS

Baseline characteristics were different between the treatment groups with in particular worse comorbidity scores and higher age in the RT cohort. The CRT schedule was completed by 96% of the patients. LC at 2 years was 83.4% (90% CI 76.0-90.8) for CRT vs. 70.9% (62.2-79.6) for RC and 67.0% (56.8-77.2) for RT. OS at 5 years was 48.9% (38.4-59.4) for CRT vs. 46.6% (36.4-56.8) for RC, and 27.6% (19.4-35.8) for RT. High T stage was significantly associated with worse LC and OS in the CRT group. GU/GI toxicity grade ≥2 occurred in 43 (48.3%) RT patients and 38 (45.2%) CRT patients.

CONCLUSIONS

The organ-preserving strategy with CRT was feasible and tolerable in this patient population, and the achieved LC and OS were satisfactory in comparison to the RC cohort and literature.

Prescription Advice Based on Data of Drug-Drug-Gene Interaction of Patients with Polypharmacy

Purpose

Pharmacogenetic counselling is a complex task and requires the efforts of an interdisciplinary team, which cannot be implemented in most cases. Therefore, simple rules could help to minimize the risk of medications incompatible with each other or with frequent genetic variants.

Patients and Methods

One hundred and eighty-four multi-morbid Caucasian patients suffering from side effects or inefficient therapy were enrolled and genotyped. Their medication was analyzed by a team of specialists using Drug-PIN^® (medication support system) and individual recommendations for 34 drug classes were generated.

Results

In each of the critical drug classes, 50% of the drugs cannot be recommended to be prescribed in typical drug cocktails. PPIs and SSRI/SNRIs represent the most critical drug classes without showing a single favorable drug. Among the well-tolerated drugs (not recommended for less than 5% of the patients) are metamizole, celecoxib, olmesartan and famotidine. For each drug class, a ranking of active ingredients according to their suitability is presented.

Conclusion

Genotyping and its profound analysis are not available in many settings today. The consideration of frequent alterations of metabolic elimination routes and drug–drug–gene interactions by using simple rankings can help to avoid many incompatibilities, side effects and inefficient therapies.

Investigation of DPYD, MTHFR and TYMS polymorphisms on 5-fluorouracil related toxicities in colorectal cancer

Aim: To investigate the association of DPYD, MTHFR and TYMS polymorphisms on 5-fluorouracil (5-FU) related toxicities and patient survival. Materials & methods: A total of 103 colorectal cancer patients prescribed 5-FU were included in the study. Genotyping was conducted for several DPYD, MTHFR and TYMS polymorphisms using a microarray analyzer. Results: DPYD 496A>G polymorphism was found to be significantly associated with 5-FU related grade 0-2, but not severe toxicities (p = 0.02). Furthermore, patients with DPYD 85TC and CC genotypes had longer progression and overall survival times compared to TT genotypes in our study group (log rank = 6.60, p = 0.01 and log rank = 4.40, p = 0.04, respectively). Conclusion: According to our results, DPYD 496AG and GG genotypes might be protective against severe adverse events compared to the AA genotype. Another DPYD polymorphism, 85T>C, may be useful in colorectal cancer prognosis. Further studies for both polymorphisms should be conducted in larger populations to achieve accurate results.

Inborn errors of purine and pyrimidine metabolism: A guide to diagnosis

Inborn errors of purine and pyrimidine (P/P) metabolism are under-reported and rarely mentioned in the general literature or in clinical practice, as well as in reviews dedicated to other inborn errors of metabolism (IEMs). However, their diagnosis is important because genetic counseling can be provided and, in some cases, specific treatment exists that may slow or even reverse clinical signs. The purpose of this review is to provide a practical guideline on the suspicion and investigation of inborn errors of P/P metabolism. Failure of a physician to recognize the presence of these disorders may be devastating for affected infants and children because of its permanent effects in the patient, and for their parents because of implications for future offspring. Diagnosis is crucial because genetic counseling can be provided and, in some cases, specific treatment can be offered that may slow or even reverse clinical symptoms. This review highlights the risk factors in the history, the important examination findings, and the appropriate biochemical investigation of the child. Herein we describe the approach to the diagnosis of P/P disorders and emphasize clinical situations in which physicians should consider these diseases as diagnostic possibilities.

Modern developments in germline pharmacogenomics for oncology prescribing

The integration of genomic data into personalized treatment planning has revolutionized oncology care. Despite this, patients with cancer remain vulnerable to high rates of adverse drug events and medication inefficacy, affecting prognosis and quality of life. Pharmacogenomics is a field seeking to identify germline genetic variants that contribute to an individual's unique drug response. Although there is widespread integration of genomic information in oncology, somatic platforms, rather than germline biomarkers, have dominated the attention of cancer providers. Patients with cancer potentially stand to benefit from improved integration of both somatic and germline genomic information, especially because the latter may complement treatment planning by informing toxicity risk for drugs with treatment-limiting tolerabilities and narrow therapeutic indices. Although certain germline pharmacogenes, such as TPMT, UGT1A1, and DPYD, have been recognized for decades, recent attention has illuminated modern potential dosing implications for a whole new set of anticancer agents, including targeted therapies and antibody-drug conjugates, as well as the discovery of additional genetic variants and newly relevant pharmacogenes. Some of this information has risen to the level of directing clinical action, with US Food and Drug Administration label guidance and recommendations by international societies and governing bodies. This review is focused on key new pharmacogenomic evidence and oncology-specific dosing recommendations. Personalized oncology care through integrated pharmacogenomics represents a unique multidisciplinary collaboration between oncologists, laboratory science, bioinformatics, pharmacists, clinical pharmacologists, and genetic counselors, among others. The authors posit that expanded consideration of germline genetic information can further transform the safe and effective practice of oncology in 2022 and beyond.

β-Ureidopropionase deficiency due to novel and rare UPB1 mutations affecting pre-mRNA splicing and protein structural integrity and catalytic activity

β-Ureidopropionase is the third enzyme of the pyrimidine degradation pathway and catalyses the conversion of N-carbamyl-β-alanine and N-carbamyl-β-aminoisobutyric acid to β-alanine and β-aminoisobutyric acid, ammonia and CO₂. To date, only a limited number of genetically confirmed patients with a complete β-ureidopropionase deficiency have been reported. Here, we report on the clinical, biochemical and molecular findings of 10 newly identified β-ureidopropionase deficient individuals. Patients presented mainly with neurological abnormalities and markedly elevated levels of N-carbamyl-β-alanine and N-carbamyl-β-aminoisobutyric acid in urine. Analysis of UPB1, encoding β-ureidopropionase, showed 5 novel missense variants and two novel splice-site variants. Functional expression of the UPB1 variants in mammalian cells showed that recombinant ß-ureidopropionase carrying the p.Ala120Ser, p.Thr129Met, p.Ser300Leu and p.Asn345Ile variant yielded no or significantly decreased β-ureidopropionase activity. Analysis of the crystal structure of human ß-ureidopropionase indicated that the point mutations affect substrate binding or prevent the proper subunit association to larger oligomers and thus a fully functional β-ureidopropionase. A minigene approach showed that the intronic variants c.[364 + 6 T > G] and c.[916 + 1_916 + 2dup] led to skipping of exon 3 and 8, respectively, in the process of UPB1 pre-mRNA splicing. The c.[899C > T] (p.Ser300Leu) variant was identified in two unrelated Swedish β-ureidopropionase patients, indicating that β-ureidopropionase deficiency may be more common than anticipated.

Importance of Rare DPYD Genetic Polymorphisms for 5-Fluorouracil Therapy in the Japanese Population

Dihydropyrimidine dehydrogenase (DPD), encoded by the DPYD gene, is the rate-limiting enzyme in 5-fluorouracil (5-FU) degradation. In Caucasians, four DPYD risk variants are recognized to be responsible for interindividual variations in the development of 5-FU toxicity. However, these risk variants have not been identified in Asian populations. Recently, 41 DPYD allelic variants, including 15 novel single nucleotide variants, were identified in 3,554 Japanese individuals by analyzing their whole-genome sequences; however, the effects of these variants on DPD enzymatic activity remain unknown. In the present study, an in vitro analysis was performed on 41 DPD allelic variants and three DPD risk variants to elucidate the changes in enzymatic activity. Wild-type and 44 DPD-variant proteins were heterologously expressed in 293FT cells. DPD expression levels and dimerization of DPD were determined by immunoblotting after SDS-PAGE and blue native PAGE, respectively. The enzymatic activity of DPD was evaluated by quantification of dihydro-5-FU, a metabolite of 5-FU, using high-performance liquid chromatography-tandem mass spectrometry. Moreover, we used 3D simulation modeling to analyze the effect of amino acid substitutions on the conformation of DPD. Among the 41 DPD variants, seven exhibited drastically decreased intrinsic clearance (CL_int) compared to the wild-type protein. Moreover, R353C and G926V exhibited no enzymatic activity, and the band patterns observed in the immunoblots after blue native PAGE indicated that DPD dimerization is required for its enzymatic activity. Our data suggest that these variants may contribute to the significant inter-individual variability observed in the pharmacokinetics and pharmacodynamics of 5-FU. In our study, nine DPD variants exhibited drastically decreased or no enzymatic activity due to dimerization inhibition or conformational changes in each domain. Especially, the rare DPYD variants, although at very low frequencies, may serve as important pharmacogenomic markers associated with the severe 5-FU toxicity in Japanese population.

Evaluation of the Tasso-SST® capillary blood microsampling device for the measurement of endogenous uracil levels

BACKGROUND

Uracil (U) plasma or serum levels can be used as surrogates of dihydropyrimidine dehydrogenase (DPD) activity, which is strongly related to the occurrence of severe or fatal toxicity after administration of fluoropyrimidines (FP) chemotherapy. Obtaining blood plasma or serum for U measurement usually requires a phlebotomy procedure by a qualified professional. An alternative to conventional blood drawn is the use of the Tasso-SST® device, which allows the collection of a small blood volume from skin capillaries. This study aimed to implement a sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) assay for the determination of U in small serum samples and to compare U concentrations measured in venous plasma, obtained after phlebotomy, and serum obtained with the Tasso-SST® device.

METHODS

Fifty microliter samples were prepared through simple protein precipitation with trichloroacetic acid. Chromatographic separation was performed with a porous graphitic carbon stationary phase and mass spectrometric detection used positive electrospray ionization. The assay was validated according to international guidelines.

RESULTS

The linear range of the assay was 5-250 ng/mL. Measurement accuracy was in the range of 98.8-108.2%, inter-assay precision was 4.3-7.3%, and intra-assay precision was 3.4-6.1%. The average matrix effect was -6.42%. The extraction yield was 95-103.3%. U concentrations measured in serum obtained with the Tasso-SST® device and venous blood plasma were highly correlated (rs = 0.910, P < 0.0001), and no systematic or proportional bias between U levels measured in both matrices was found.

CONCLUSIONS

The use of blood microsampling with the Tasso-SST® device is a useful alternative for the measurement of U and the identification of patients with DPD deficiency.

Diagnosis and management of 5-fluorouracil (5-FU)-induced acute leukoencephalopathy: lessons learnt from a single-Centre case series

Background

The administration of 5-fluorouracil (5FU) in the treatment of gastrointestinal (GI) malignancies is associated with common side effects such as mucositis, diarrhoea, and myelosuppression, which are easily managed with supportive measures and dose adjustments. Cardiotoxicity and neurotoxicity are rare but reversible side effects of 5-FU and are treated with withdrawal of the drug and conservative measures. The presenting symptoms of 5-FU-induced leukoencephalopathy are often confusing and pose a diagnostic dilemma in routine clinical practice.

Methods

We report a series of five patients with GI malignancies who developed 5-FU-induced leukoencephalopathy.

Results

All (n = 5) had Naranjo scores of 6–7, predictive of 5-FU-related adverse effects, with clinical and radiological findings suggestive of 5-FU-induced encephalopathy as described in prior literature. The median time to onset of symptoms from initiation of 5FU was 3 days (range: 2–4 days). All patients improved after conservative management with complete neurological recovery.

Conclusion

Prompt recognition of this rare yet severe adverse effect of 5-FU-based chemotherapy aids early withdrawal of the offending agent (5-FU) and timely initiation of supportive measures and helps plan alternative oncological interventions.

Dihydropyrimidine Dehydrogenase Deficiency and Implementation of Upfront DPYD Genotyping

Fluoropyrimidines (FP; 5-fluorouracil, capecitabine, and tegafur) are a commonly prescribed class of antimetabolite chemotherapies, used for various solid organ malignancies in over 2 million patients globally per annum. Dihydropyrimidine dehydrogenase (DPD), encoded by the DPYD gene, is the critical enzyme implicated in FP metabolism. DPYD variant genotypes can result in decreased DPD production, leading to the development of severe toxicities resulting in hospitalization, intensive care admission, and even death. Management of toxicity incurs financial burden on both patients and healthcare systems alike. Upfront DPYD genotyping to identify variant carriers allows an opportunity to identify patients who are at high risk to suffer from serious toxicities and allow prospective dose adjustment of FP treatment. This approach has been shown to reduce patient morbidity, as well as improve the cost-effectiveness of managing FP treatment. Upfront DPYD genotyping has been recently endorsed by several countries in Europe and the United Kingdom. This review summarizes current knowledge about DPD deficiency and upfront DPYD genotyping, including clinical and cost-effectiveness outcomes, with the intent of supporting implementation of an upfront DPYD genotyping service with individualized dose-personalization.

DPYD polymorphisms c.496A>G, c.2194G>A and c.85T>C and risk of severe adverse drug reactions in patients treated with fluoropyrimidine-based protocols

AIMS

Cancer patients with reduced dihydropyrimidine dehydrogenase (DPD) activity are at increased risk of severe fluoropyrimidine (FP)-related adverse events (AE). Guidelines recommend FP dosing adjusted to genotype-predicted DPD activity based on four DPYD variants (rs3918290, rs55886062, rs67376798 and rs56038477). We evaluated the relationship between three further DPYD polymorphisms: c.496A>G (rs2297595), *6 c.2194G>A (rs1801160) and *9A c.85T>C (rs1801265) and the risk of severe AEs.

METHODS

Consecutive FP-treated adult patients were genotyped for "standard" and tested DPYD variants, and for UGT1A1*28 if irinotecan was included, and were monitored for the occurrence of grade ≥3 (National Cancer Institute Common Terminology Criteria) vs. grade 0-2 AEs. For each of the tested polymorphisms, variant allele carriers were matched to respective wild type controls (optimal full matching combined with exact matching, in respect to: age, sex, type of cancer, type of FP, DPYD activity score, use of irinotecan/UGT1A1, adjuvant therapy, radiotherapy, biological therapy and genotype on the remaining two tested polymorphisms).

RESULTS

Of the 503 included patients (82.3% colorectal cancer), 283 (56.3%) developed grade ≥3 AEs, mostly diarrhoea and neutropenia. Odds of grade ≥3 AEs were higher in c.496A>G variant carriers (n = 127) than in controls (n = 376) [OR = 5.20 (95% CI 1.88-14.3), Bayesian OR = 5.24 (95% CrI 3.06-9.12)]. Odds tended to be higher in c.2194G>A variant carriers (n = 58) than in controls (n = 432) [OR = 1.88 (0.95-3.73), Bayesian OR = 1.90 (1.03-3.56)]. c.85T>C did not appear associated with grade ≥3 AEs (206 variant carriers vs. 284 controls).

CONCLUSION

DPYD c.496A>G and possibly c.2194G>A variants might need to be considered for inclusion in the DPYD genotyping panel.

Application of Micro-Engineered Kidney, Liver, and Respiratory System Models to Accelerate Preclinical Drug Testing and Development

Developing novel drug formulations and progressing them to the clinical environment relies on preclinical in vitro studies and animal tests to evaluate efficacy and toxicity. However, these current techniques have failed to accurately predict the clinical success of new therapies with a high degree of certainty. The main reason for this failure is that conventional in vitro tissue models lack numerous physiological characteristics of human organs, such as biomechanical forces and biofluid flow. Moreover, animal models often fail to recapitulate the physiology, anatomy, and mechanisms of disease development in human. These shortfalls often lead to failure in drug development, with substantial time and money spent. To tackle this issue, organ-on-chip technology offers realistic in vitro human organ models that mimic the physiology of tissues, including biomechanical forces, stress, strain, cellular heterogeneity, and the interaction between multiple tissues and their simultaneous responses to a therapy. For the latter, complex networks of multiple-organ models are constructed together, known as multiple-organs-on-chip. Numerous studies have demonstrated successful application of organ-on-chips for drug testing, with results comparable to clinical outcomes. This review will summarize and critically evaluate these studies, with a focus on kidney, liver, and respiratory system-on-chip models, and will discuss their progress in their application as a preclinical drug-testing platform to determine in vitro drug toxicology, metabolism, and transport. Further, the advances in the design of these models for improving preclinical drug testing as well as the opportunities for future work will be discussed.

The Value of Pharmacogenetics to Reduce Drug-Related Toxicity in Cancer Patients

Many anticancer drugs cause adverse drug reactions (ADRs) that negatively impact safety and reduce quality of life. The typical narrow therapeutic range and exposure-response relationships described for anticancer drugs make precision dosing critical to ensure safe and effective drug exposure. Germline mutations in pharmacogenes contribute to inter-patient variability in pharmacokinetics and pharmacodynamics of anticancer drugs. Patients carrying reduced-activity or loss-of-function alleles are at increased risk for ADRs. Pretreatment genotyping offers a proactive approach to identify these high-risk patients, administer an individualized dose, and minimize the risk of ADRs. In the field of oncology, the most well-studied gene-drug pairs for which pharmacogenetic dosing recommendations have been published to improve safety are DPYD-fluoropyrimidines, TPMT/NUDT15-thiopurines, and UGT1A1-irinotecan. Despite the presence of these guidelines, the scientific evidence showing the benefits of pharmacogenetic testing (e.g., improved safety and cost-effectiveness) and the development of efficient multi-gene genotyping panels, routine pretreatment testing for these gene-drug pairs has not been implemented widely in the clinic. Important considerations required for widespread clinical implementation include pharmacogenetic education of physicians, availability or allocation of institutional resources to build an efficient clinical infrastructure, international standardization of guidelines, uniform adoption of guidelines by regulatory agencies leading to genotyping requirements in drug labels, and development of cohesive reimbursement policies for pretreatment genotyping. Without clinical implementation, the potential of pharmacogenetics to improve patient safety remains unfulfilled.