Comprehensive pharmacogenetic analysis of irinotecan neutropenia and pharmacokinetics

Parallel Toxicities: A Comparative Analysis of Chemotherapy-Induced Neutropenia and Alopecia

Chemotherapy-induced neutropenia (CIN) and chemotherapy-induced alopecia (CIA) are significant toxicities affecting cancer patients. CIN is a potentially fatal complication of chemotherapy caused by myelosuppression and increased infection susceptibility, while CIA, although not fatal, severely affects treatment adherence and mental health. This study provides a comprehensive comparative analysis of CIN and CIA, focusing on patient, disease, treatment, and genetic risk factors. Key risk factors for CIN and CIA include age, poor performance status, body mass index (BMI), laboratory abnormalities, and pre-existing comorbidities. Both toxicities were significantly associated with breast cancer patients, although CIN patients were more likely to have hematological cancer, and CIA patients were more likely to have solid tumors. Notably, anthracyclines, alkylators, and taxanes frequently induce both toxicities, although their timelines and clinical implications differed. There was no clear overlap between genetic predispositions and toxicities beyond single-nucleotide polymorphisms (SNPs) in the ABCB1 gene. This is the first study to directly compare CIN and CIA, offering insights into personalized oncology care. Understanding the risk factors implicated in the development of CIN and CIA will enable physicians to manage patient outcomes.

AI-Driven Discovery of Highly Specific and Efficacious hCES2A Inhibitors for Ameliorating Irinotecan-Triggered Gut Toxicity

The anticancer agent irinotecan often induces severe delayed-onset diarrhea, inhibiting human carboxylesterase 2A (hCES2A) can significantly alleviate irinotecan-triggered gut toxicity (ITGT). This work presents an efficient workflow for de novo design and developing novel efficacious hCES2A inhibitors. A well-training machine learning model identified scaffold-14 as a lead compound, while compound 14n was developed as a novel time-dependent hCES2A inhibitor (IC50 = 0.04 nM) following three rounds of structural optimization. The covalent binding modes and inactivation mechanisms of 14n were elucidated by nanoLC-MS/MS-based chemoproteomics and covalent docking simulations. Notably, 14n showed excellent selectivity, good cell-membrane permeability, favorable drug-like properties, and potent inhibition on intracellular hCES2A. In vivo tests demonstrated that 14n was orally active, showing favorable safety profiles and impressive ameliorative effects on ITGT in tumor-bearing mice. Collectively, this work showcases a high-efficient AI-driven strategy for developing novel efficacious hCES2A inhibitors, while 14n emerges as a promising candidate for alleviating ITGT.

Pharmacogenomics in Solid Tumors: A Comprehensive Review of Genetic Variability and Its Clinical Implications

Pharmacogenomics, the study of how genetic variations influence drug response, has become integral to cancer treatment as personalized medicine evolves. This review aims to explore key pharmacogenomic biomarkers relevant to cancer therapy and their clinical implications, providing an updated and comprehensive perspective on how genetic variations impact drug metabolism, efficacy, and toxicity in oncology. Genetic heterogeneity among oncology patients significantly impacts drug efficacy and toxicity, emphasizing the importance of incorporating pharmacogenomic testing into clinical practice. Genes such as CYP2D6, DPYD, UGT1A1, TPMT, EGFR, KRAS, and BRCA1/2 play pivotal roles in influencing the metabolism, efficacy, and adverse effects of various chemotherapeutic agents, targeted therapies, and immunotherapies. For example, CYP2D6 polymorphisms affect tamoxifen metabolism in breast cancer, while DPYD variants can result in severe toxicities in patients receiving fluoropyrimidines. Mutations in EGFR and KRAS have significant implications for the use of targeted therapies in lung and colorectal cancers, respectively. Additionally, BRCA1/2 mutations predict the efficacy of PARP inhibitors in breast and ovarian cancer. Ongoing research in polygenic risk scores, liquid biopsies, gene-drug interaction networks, and immunogenomics promises to further refine pharmacogenomic applications, improving patient outcomes and reducing treatment-related adverse events. This review also discusses the challenges and future directions in pharmacogenomics, including the integration of computational models and CRISPR-based gene editing to better understand gene-drug interactions and resistance mechanisms. The clinical implementation of pharmacogenomics has the potential to optimize cancer treatment by tailoring therapies to an individual's genetic profile, ultimately enhancing therapeutic efficacy and minimizing toxicity.

Prodrugs in Oncology: Bioactivation and Impact on Therapeutic Efficacy and Toxicity

A prodrug is a molecule that lacks pharmacological activity, but upon enzymatic bioactivation, it can generate a therapeutically active molecule. The primary reason behind the design of a prodrug is to help circumvent challenges associated with the physicochemical properties of a drug molecule, such as solubility, absorption, distribution, and instability. Chemotherapy has been at the forefront of cancer treatment for over 70 years due to its ability to target rapidly proliferating tumor cells. However, a major concern with conventional chemotherapy is the lack of selectivity and its associated side toxicity, which can severely impact patients' quality of life. In oncology, prodrugs have been explored to enhance the bioavailability, improve efficacy, and minimize systemic toxicity of chemotherapeutic agents. Prodrugs activated by enzymes unique to a tumor microenvironment can significantly increase targeted delivery of chemotherapeutic drugs. This review aims to highlight commonly used chemotherapeutic prodrugs, including both alkylating and non-alkylating agents, and discuss their clinical relevance, mechanisms of bioactivation, and toxicity concerns.

Identification of UDP-glucuronosyltransferase (UGT) isoforms involved in the metabolism of Chlorophenols (CPs)

Chlorophenols (CPs) are a group of pollutants that pose a great threat to the environment, they are widely used in industrial and agricultural wastes, pesticides, herbicides, textiles, pharmaceuticals and plastics. Among CPs, pentachlorophenol was listed as one of the persistent organic pollutants (POPs) by the Stockholm convention. This study aims to identify the UDP-glucosyltransferase (UGT) isoforms involved in the metabolic elimination of CPs. CPs' mono-glucuronide was detected in the human liver microsomes (HLMs) incubation mixture with co-factor uridine-diphosphate glucuronic acid (UDPGA). HLMs-catalyzed glucuronidation metabolism reaction equations followed Michaelis-Menten or substrate inhibition type. Recombinant enzymes and chemical reagents inhibition experiments were utilized to phenotype the main UGT isoforms involved in the glucuronidation of CPs. UGT1A6 might be the major enzyme in the glucuronidation of mono-chlorophenol isomer. UGT1A1, UGT1A6, UGT1A9, UGT2B4 and UGT2B7 were the most important five UGT isoforms for metabolizing the di-chlorophenol and tri-chlorophenol isomers. UGT1A1 and UGT1A3 were the most important UGT isoforms in the catalysis of tetra-chlorophenol and pentachlorophenol isomers. Species differences were investigated using rat liver microsomes (RLMs), pig liver microsomes (PLMs), dog liver microsomes (DLMs), and monkey liver microsomes (MyLMs). All these results were helpful for elucidating the metabolic elimination and toxicity of CPs.

Model-Based Prediction of Irinotecan-Induced Grade 4 Neutropenia in Cancer Patients: Influence of Incorporating Germline Genetic Factors in the Model

Neutropenia is the major dose-limiting toxicity of irinotecan-based therapy. The objective of this study was to assess whether inclusion of germline genetic variants into a population pharmacokinetic/pharmacodynamic model can improve prediction of irinotecan-induced grade 4 neutropenia and identify novel variants of clinical value. A semimechanistic population pharmacokinetic/pharmacodynamic model was used to predict neutrophil response over time in 197 patients receiving irinotecan. Covariate analysis was performed for demographic/clinical factors and 4,781 genetic variants in 84 drug response- and toxicity-related genes to identify covariates associated with neutrophil response. We evaluated the predictive value of the model for grade 4 neutropenia reflecting different clinical scenarios of available data on identified demographic/clinical covariates, baseline and post-treatment absolute neutrophil counts (ANCs), individual pharmacokinetics, and germline genetic variation. Adding 8 genetic identified covariates (rs10929302 (UGT1A1), rs1042482 (DPYD), rs2859101 (HLA-DQB3), rs61754806 (NR3C1), rs9266271 (HLA-B), rs7294 (VKORC1), rs1051713 (ALOX5), and ABCB1 rare variant burden) to a model using only baseline ANCs improved prediction of irinotecan-induced grade 4 neutropenia from area under the receiver operating characteristic curve (AUC-ROC) of 50-64% (95% confidence interval (CI), 54-74%). Individual pharmacokinetics further improved the prediction to 74% (95% CI, 64-84%). When weekly ANC was available, the identified covariates and individual pharmacokinetics yielded no additional contribution to the prediction. The model including only ANCs at baseline and at week 1 achieved an AUC-ROC of 78% (95% CI, 69-88%). Germline DNA genetic variants may contribute to the prediction of irinotecan-induced grade 4 neutropenia when incorporated into a population pharmacokinetic/pharmacodynamic model. This approach is generalizable to drugs that induce neutropenia and ultimately allows for personalized intervention to enhance patient safety.

UGT1A1 genotype-guided irinotecan dosing during neoadjuvant chemoradiotherapy for locally advanced rectal cancer: A prospective analysis of SN-38 concentration

Irinotecan plays a crucial role in the neoadjuvant chemoradiotherapy (nCRT) of rectal cancer, but its optimal dosing is still unclear. In this study, we included 101 eligible patients with the UGT1A1*28 genotype of UGT1A1*1*1 (74.3%) and UGT1A1*1*28 (25.7%) and UGT1A1*6 genotypes of GG (63.4%), GA (32.7%), and AA (3.9%). All patients received preoperative radiotherapy (50 Gy/25 fractions) with concurrent irinotecan (UGT1A1*1*1: 80 mg/m2 ; UGT1A1*1*28: 65 mg/m2 ) and capecitabine (CapIri). SN-38 concentrations were measured at 1.5, 24, and 49 h post-administration. Patients were divided into four groups (Q1-Q4) based on the SN-38 concentration. The complete-response (CR) rate was the primary endpoint. The analysis demonstrated that the 49 h SN-38 concentration was relatively optimal for predicting efficacy and toxicity. The Q4 group had a significantly higher CR rate than the Q1 group (p = .019), but also higher rates of adverse events (p = .009). We screened the recommended 49 h SN-38, with a 0.5-1.0 ng/mL concentration range. We also validated the correlation between UGT1A1*6 polymorphism and SN-38 concentration, along with the clinical efficacy of irinotecan. In conclusion, our study identified the relatively optimal timepoint and concentration range for monitoring SN38 concentrations and revealed the clinical significance of UGT1A1*6 and UGT1A1*28 polymorphisms in guiding irinotecan administration, offering meaningful insights for personalised irinotecan dosing.

UGT1A1 Testing in Breast Cancer: should it become routine practice in patients treated with antibody-drug conjugates?

The use of genetic testing to personalize therapeutic strategies in cancer is rapidly evolving and thus changing the landscape of treatment of oncologic patients. The UGT1A1 gene is an important component for the metabolism and glucoronidation of certain drugs, including irinotecan and sacituzumab govitecan (SG); therefore, various UGT1A1 polymorphisms leading to decreased function of the UGT1A1 enzyme may lead to increased risk of treatment-related side effects. Testing for UGT1A1 polymorphism is not routinely adopted in clinical practice; that is due to the lack of concise studies and recommendations concerning the clinical relevance of this test and its impact on the quality of life of cancer patients. The knowledge regarding UGT1A1 polymorphism and its clinical relevance will be reviewed in this article, as well as the published literature on the association between UGT1A1 polymorphism and the toxicity risk of irinotecan as well as sacituzumab govitecan. The current recommendations and guidelines on UGT1A1 testing will be discussed in detail in the hopes of providing guidance to oncologists in their clinical practice.

Role of MRPs transporters in pharmacokinetics and intestinal toxicity of irinotecan

To identify additional genetic markers contributing to variability in CPT-11 disposition and toxicity, we assessed impact of the multiple drug-resistant transporters 1, 2, and 3 (MRP1, MRP2, and MRP3) on the intestinal toxicity, pharmacokinetics, tissue distribution and biliary excretion of CPT-11 using a knockout mouse model. Mrp1/3 knockout had minor impact on intestinal toxicity of CPT-11, tissue distribution, biliary excretion, and PK parameter of its active metabolites SN38. Conversely, Mrp2-/- mice, with low carboxylesterase activity, displayed insensitivity to CPT-11 toxicity due to reduced intestinal exposure to SN38. In PK studies, Mrp1/2 knockout significantly increased the AUC of CPT-11 compared to their AUC in FVB mice. However, the AUC of SN38 in Mrp2 -/- mice was decreased by 3.25-fold. Mrp3 knockout only slightly increased SN38 plasma exposure. Lastly, Mrp2/3 knockout increased biliary excretion amount of CPT-11 by 67.2% and 48.5% compared to wild-type mice, respectively. Consequently, Mrp1/3 deficiency didn't change SN38 tissue distribution. Finally, correlation analysis demonstrated that tissue exposure to SN38 was better correlated with toxicity than plasma AUC of SN38. Mrp1/2/3 deficiency showed a minor impact on PK, biliary excretion, distribution and intestinal exposure of SN38, and as a result, did not affect the intestinal toxicity of CPT-11.

Cost-utility analysis and cross-country comparison of pharmacogenomics-guided treatment in colorectal cancer patients participating in the U-PGx PREPARE study

OBJECTIVES

A cost-utility analysis was conducted to evaluate pharmacogenomic (PGx)-guided treatment compared to the standard-of-care intervention among patients diagnosed with colorectal cancer (CRC) in Italy.

METHODS

Data derived from a prospective, open-label, block randomized clinical trial, as a part of the largest PGx study worldwide (355 patients in both arms) were used. Mortality was used as the primary health outcome to estimate life years (LYs) gained in treatment arms within a survival analysis context. PGx-guided treatment was based on established drug-gene interactions between capecitabine, 5-fluorouracil and irinotecan with DPYD and/or UGT1A1 genomic variants. Utility values for the calculation of Quality Adjusted Life Year (QALY) was based on Visual Analog Scale (VAS) score. Missing data were imputed via the Multiple Imputation method and linear interpolation, when possible, while censored cost data were corrected via the Replace-From-The-Right algorithm. The Incremental Cost-Effectiveness Ratio (ICER) was calculated for QALYs. Raw data were bootstrapped 5000 times in order to produce 95% Confidence Intervals based on non-parametric percentile method and to construct a cost-effectiveness acceptability curve. Cost differences for study groups were investigated via a generalized linear regression model analysis. Total therapy cost per patient reflected all resources expended in the management of any adverse events, including medications, diagnostics tests, devices, surgeries, the utilization of intensive care units, and wards.

RESULTS

The total cost of the study arm was estimated at €380 (∼ US$416; 95%CI: 195-596) compared to €565 (∼ US$655; 95%CI: 340-724) of control arm while the mean survival in study arm was estimated at 1.58 (+0.25) LYs vs 1.50 (+0.26) (Log Rank test, X2 = 4.219, df=1, p-value=0.04). No statistically significant difference was found in QALYs. ICER was estimated at €13418 (∼ US$14695) per QALY, while the acceptability curve indicated that when the willingness-to-pay was under €5000 (∼ US$5476), the probability of PGx being cost-effective overcame 70%. The most frequent adverse drug event in both groups was neutropenia of severity grade 3 and 4, accounting for 82.6% of total events in the study arm and 65.0% in the control arm. Apart from study arm, smoking status, Body-Mass-Index and Cumulative Actionability were also significant predictors of total cost. Subgroup analysis conducted in actionable patients (7.9% of total patients) indicated that PGx-guided treatment was a dominant option over its comparator with a probability greater than 92%. In addition, a critical literature review was conducted, and these findings are in line with those reported in other European countries.

CONCLUSION

PGx-guided treatment strategy may represent a cost-saving option compared to the existing conventional therapeutic approach for colorectal cancer patient management in the National Health Service of Italy.

Irinotecan-Induced Toxicity: A Pharmacogenetic Study Beyond UGT1A1

BACKGROUND AND OBJECTIVE

Side effects of irinotecan treatment can be dose limiting and may impair quality of life. In this study, we investigated the correlation between single nucleotide polymorphisms (SNPs) in genes encoding enzymes involved in the irinotecan metabolism and transport, outside UGT1A1, and irinotecan-related toxicity. We focused on carboxylesterases, which are involved in formation of the active metabolite SN-38 and on drug transporters.

METHODS

Patients who provided written informed consent at the Erasmus Medical Center Cancer Institute to the Code Geno study (local protocol: MEC02-1002) or the IRI28-study (NTR-6612) were enrolled in the study and were genotyped for 15 SNPs in the genes CES1, CES2, SLCO1B1, ABCB1, ABCC2, and ABCG2.

RESULTS

From 299 evaluable patients, 86 patients (28.8%) developed severe irinotecan-related toxicity. A significantly higher risk of toxicity was seen in ABCG2 c.421C>A variant allele carriers (P = 0.030, OR 1.88, 95% CI 1.06-3.34). Higher age was associated with all grade diarrhea (P = 0.041, OR 1.03, 95% CI 1.00-1.06). In addition, CES1 c.1165-41C>T and CES1 n.95346T>C variant allele carriers had a lower risk of all-grade thrombocytopenia (P = 0.024, OR 0.42, 95% CI 0.20-0.90 and P = 0.018, OR 0.23, 95% CI 0.08-0.79, respectively).

CONCLUSION

Our study indicates that ABCG2 and CES1 SNPs might be used as predictive markers for irinotecan-induced toxicity.

UGT1A1 genotype-guided dosing of irinotecan: time to prioritize patient safety

Tweetable abstract Pretreatment UGT1A1 genotyping and a 70% irinotecan dose intensity in poor metabolizers is safe, feasible, cost-effective and essential for safe irinotecan treatment in cancer patients. It is time to update guidelines to swiftly enable the implementation of UGT1A1 genotype-guided irinotecan dosing in routine oncology care.

Recent advances in SN-38 drug delivery system

DNA topoisomerase I plays a key role in lubricatingthe wheels of DNA replication or RNA transcription through breaking and reconnecting DNA single-strand. It is widely known that camptothecin and its derivatives (CPTs) have inhibitory effects on topoisomerases I, and have obtained some clinical benefits in cancer treatment. The potent cytotoxicity makes 7-ethyl-10-hydroxycamptothecin (SN-38) become a brilliant star among these derivatives. However, some undesirable physical and chemical properties of this compound, including poor solubility and stability, seriously hinder its effective delivery to tumor sites. In recent years, strategies to alleviate these defects have aroused extensive research interest. By focusing on the loading mechanism, basic nanodrug delivery systems with SN-38 loaded, like nanoparticles, liposomes and micelles, are demonstrated here. Additionally, functionalized nanodrug delivery systems of SN-38 including prodrug and active targeted nanodrug delivery systems and delivery systems designed to overcome drug resistance are also reviewed. At last, challenges for future research in formulation development and clinical translation of SN-38 drug delivery system are discussed.

Novel disulfide bond bridged 7-ethyl-10-hydroxyl camptothecin-undecanoic acid conjugate/human serum albumin nanoparticles for breast cancer therapy

7-Ethyl-10-hydroxyl camptothecin (SN38), a semisynthetic derivative of camptothecin, exhibited extreme pharmacological activities in treating a range of cancers. However, its poor aqueous solubility and low stability hinder its clinical applications. Hence, a redox-responsive SN38 prodrug encapsulated human serum albumin (HSA) nanoparticle is developed to realize its potential in the clinic. First, a disulfide bond bridged 7-ethyl-10-hydroxyl camptothecin-undecanoic acid conjugate (SN38-SS-COOH) was synthesized and characterized structurally. After that, SN38-SS-COOH/HSA nanoparticles (SNH NPs) were prepared by the desolvation method. The SNH NPs with a feed molar ratio of 9 : 1 of SN38-SS-COOH : HSA showed a spherical structure with a diameter range of approximately 120-150 nm revealed by dynamic light scattering (DLS) and transmission electron microscopy (TEM). Fluorescence quenching confirmed the formation of SNH NP complexes by dual hydrophobic force and electrostatic interaction. The SNH NPs have a high drug loading of 10.44% and an encapsulation efficiency of 89.59% with good stability. Moreover, the redox responsiveness was validated by glutathione (GSH)-triggered accelerated release of parent drug SN38. In an in vivo pharmacokinetic study, the SNH NPs exhibited a significantly prolonged circulation time (t_1/2, 3.77-fold) compared with free SN38. Finally, the in vivo antitumor efficacy and systemic toxicity of SNH NPs in a breast xenograft model were thoroughly evaluated. The inhibition rate of tumor growth induced by the SNH NPs reached 70.1%, while only 50.1% was achieved for irinotecan at an equivalent SN38 dosage of 10 mg kg^-1. More importantly, the SNH NPs achieved a higher level of tumor growth inhibition (85.3%) by increasing the dosage to 60 mg kg^-1 SN38 without obvious adverse effects. Taken together, the use of redox-responsive SN38 prodrug/HSA NPs could be a promising strategy to deliver highly active SN38 for breast cancer chemotherapy.

Association Between ABCG2, ABCB1, ABCC2 Efflux Transporter Single-Nucleotide Variants and Irinotecan Adverse Effects in Patients With Colorectal Cancer: A Real-Life Study

Among patients treated with irinotecan, homozygous carriers of the UGT1A1*28 allele are at increased risk for neutropenia, but UGT1A1 genotype alone does not account for irinotecan-induced toxicity. Our aim was to study the association between single-nucleotide variants in genes encoding for efflux transporters of irinotecan (ABCG2, ABCB1, and ABCC2) and toxicity in real life. The source population was a cohort of patients with colorectal cancer (CRC) in Northern Israel, who had undergone genome-wide association study. From the source population we chose the patients with CRC prescribed irinotecan, and a comparative cohort of patients with CRC treated with other anticancer systemic therapies. Using Clalit Health Services electronic medical records (including laboratory results) we ascertained hematological and gastrointestinal adverse effects and mortality, within 90 days of the first dose, as a composite outcome. There were 601 patients with CRC who received irinotecan, and 756 patients with CRC treated with other anticancer regimens. The minor allele in rs2231142 (ABCG2) was associated with lower incidence of the composite outcome (odds ratio (OR) = 0.54 (0.33, 0.91); P = 0.02) in irinotecan-treated patients with CRC, but not in patients with CRC treated with other regimens. ABCB1 rs1045642 and ABCC2 rs3740066 were not associated with the composite outcome. In a sensitivity analysis, adjusted for UGT1A1 status and for possible demographic and clinical confounders, adjusted OR was 0.56 (0.33, 0.94) for the association between rs2231142 (ABCG2) and the composite outcome. In conclusion, we describe a novel association between the minor allele of rs2231142 in the efflux transporter gene ABCG2 and protection against severe side effects in CRC patients treating with irinotecan.

Disulfide Bond-Based SN38 Prodrug Nanoassemblies with High Drug Loading and Reduction-Triggered Drug Release for Pancreatic Cancer Therapy

Purpose

Chemotherapy is a significant and effective therapeutic strategy that is frequently utilized in the treatment of cancer. Small molecular prodrug-based nanoassemblies (SMPDNAs) combine the benefits of both prodrugs and nanomedicine into a single nanoassembly with high drug loading, increased stability, and improved biocompatibility.

Methods

In this study, a disulfide bond inserted 7-ethyl-10-hydroxycamptothecin (SN38) prodrug was rationally designed and then used to prepare nanoassemblies (SNSS NAs) that were selectively activated by rich glutathione (GSH) in the tumor site. The characterization of SNSS NAs and the in vitro and in vivo evaluation of their antitumor effect on a pancreatic cancer model were performed.

Results

In vitro findings demonstrated that SNSS NAs exhibited GSH-induced SN38 release and cytotoxicity. SNSS NAs have demonstrated a passive targeting effect on tumor tissues, a superior antitumor effect compared to irinotecan (CPT-11), and satisfactory biocompatibility with double dosage treatment.

Conclusion

The SNSS NAs developed in this study provide a new method for the preparation of SN38-based nano-delivery systems with improved antitumor effect and biosafety.

Serum metabolic traits reveal therapeutic toxicities and responses of neoadjuvant chemoradiotherapy in patients with rectal cancer

Neoadjuvant chemoradiotherapy (nCRT) has become the standard treatment for patients with locally advanced rectal cancer (LARC). Therapeutic efficacy of nCRT is significantly affected by treatment-induced diarrhea and hematologic toxicities. Metabolic alternations in cancer therapy are key determinants to therapeutic toxicities and responses, but exploration in large-scale clinical studies remains limited. Here, we analyze 743 serum samples from 165 LARC patients recruited in a phase III clinical study using untargeted metabolomics and identify responsive metabolic traits over the course of nCRT. Pre-therapeutic serum metabolites successfully predict the chances of diarrhea and hematologic toxicities during nCRT. Particularly, levels of acyl carnitines are linked to sex disparity in nCRT-induced diarrhea. Finally, we show that differences in phenylalanine metabolism and essential amino acid metabolism may underlie distinct therapeutic responses of nCRT. This study illustrates the metabolic dynamics over the course of nCRT and provides potential to guide personalized nCRT treatment using responsive metabolic traits.

A Systematic Review of Polygenic Models for Predicting Drug Outcomes

Polygenic models have emerged as promising prediction tools for the prediction of complex traits. Currently, the majority of polygenic models are developed in the context of predicting disease risk, but polygenic models may also prove useful in predicting drug outcomes. This study sought to understand how polygenic models incorporating pharmacogenetic variants are being used in the prediction of drug outcomes. A systematic review was conducted with the aim of gaining insights into the methods used to construct polygenic models, as well as their performance in drug outcome prediction. The search uncovered 89 papers that incorporated pharmacogenetic variants in the development of polygenic models. It was found that the most common polygenic models were constructed for drug dosing predictions in anticoagulant therapies (n = 27). While nearly all studies found a significant association with their polygenic model and the investigated drug outcome (93.3%), less than half (47.2%) compared the performance of the polygenic model against clinical predictors, and even fewer (40.4%) sought to validate model predictions in an independent cohort. Additionally, the heterogeneity of reported performance measures makes the comparison of models across studies challenging. These findings highlight key considerations for future work in developing polygenic models in pharmacogenomic research.

Model-Based Prediction of Irinotecan-Induced Grade 4 Neutropenia in Advanced Cancer Patients: Influence of Demographic and Clinical Factors

Severe neutropenia is the major dose-liming toxicity of irinotecan-based chemotherapy. The objective was to assess to what extent a population pharmacokinetic/pharmacodynamic model including patient-specific demographic/clinical characteristics, individual pharmacokinetics, and absolute neutrophil counts (ANCs) can predict irinotecan-induced grade 4 neutropenia. A semimechanistic population pharmacokinetic/pharmacodynamic model was developed to describe neutrophil response over time in 197 patients with cancer receiving irinotecan. For covariate analysis, sex, race, age, pretreatment total bilirubin, and body surface area were evaluated to identify significant covariates on system-related parameters (mean transit time (MTT) and ɣ) and sensitivity to neutropenia effects of irinotecan and SN-38 (SLOPE). The model-based simulation was performed to assess the contribution of the identified covariates, individual pharmacokinetics, and baseline ANC alone or with incremental addition of weekly ANC up to 3 weeks on predicting irinotecan-induced grade 4 neutropenia. The time course of neutrophil response was described using the model assuming that irinotecan and SN-38 have toxic effects on bone marrow proliferating cells. Sex and pretreatment total bilirubin explained 10.5% of interindividual variability in MTT. No covariates were identified for SLOPE and γ. Incorporating sex and pretreatment total bilirubin (area under the receiver operating characteristic curve (AUC-ROC): 50%, 95% CI 50-50%) or with the addition of individual pharmacokinetics (AUC-ROC: 62%, 95% CI 53-71%) in the model did not result in accurate prediction of grade 4 neutropenia. However, incorporating ANC only at baseline and week 1 in the model achieved a good prediction (AUC-ROC: 78%, 95% CI 69-88%). These results demonstrate the potential applicability of a model-based approach to predict irinotecan-induced neutropenia, which ultimately allows for personalized intervention to maximize treatment outcomes.

Characterization of SN38-resistant T47D breast cancer cell sublines overexpressing BCRP, MRP1, MRP2, MRP3, and MRP4

Background

Although several novel resistant breast cancer cell lines have been established, only a few resistant breast cancer cell lines overexpress breast cancer resistance proteins (BCRP). The aim of this study was to establish new resistant breast cancer cell lines overexpressing BCRP using SN38 (7-ethyl-10-hydroxycamptothecin), an active metabolite of irinotecan and was to discover genes and mechanisms associated with multidrug resistance.

Methods

SN38-resistant T47D breast cancer cell sublines were selected from the wild-type T47D cells by gradually increasing SN38 concentration. The sensitivity of the cells to anti-cancer drugs was assessed by 3-(4,5-methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide (MTT) assay. Expression profiles of the resistance-related transporters were examined using RT-qPCR, and western blot analysis. Intracellular fluorescent dye accumulation in the resistant cells was determined using flow cytometry.

Results

The SN38-resistant T47D breast cancer cell sublines T47D/SN120 and T47D/SN150 were established after long-term exposure (more than 16 months) of wild-type T47D cells to 120 nM and 150 nM SN38, respectively. T47D/SN120 and T47D/SN150 cells were more resistant to SN38 (14.5 and 59.1 times, respectively), irinotecan (1.5 and 3.7 times, respectively), and topotecan (4.9 and 12 times, respectively), than the wild-type parental cells. Both T47D/SN120 and T47D/SN150 sublines were cross-resistant to various anti-cancer drugs. These resistant sublines overexpressed mRNAs of MRP1, MRP2, MRP3, MRP4, and BCRP. The DNA methylase inhibitor 5-aza-2′-deoxycytidine and the histone deacetylase inhibitor trichostatin A increased the expression levels of BCRP, MRP1, MRP2, MRP3, and MRP4 transcripts in T47D/WT cells. Fluorescent dye accumulation was found to be lower in T47D/SN120 and T47D/SN150 cells, compared to that in T47D/WT cells. However, treatment with known chemosensitizers increased the intracellular fluorescent dye accumulation and sensitivity of anti-tumor agents.

Conclusion

T47D/SN120 and T47D/SN150 cells overexpressed MRP1, MRP2, MRP3, MRP4, and BCRP, which might be due to the suppression of epigenetic gene silencing via DNA hypermethylation and histone deacetylation. Although these resistant cells present a higher resistance to various anti-cancer drugs than their parental wild-type cells, multidrug resistance was overcome by treatment with chemosensitizers. These SN38 resistant T47D breast cancer cell sublines expressing resistance proteins can be useful for the development of new chemosensitizers.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12885-022-09446-y.

Pharmacogenetic Profiling in High-Risk Soft Tissue Sarcomas Treated with Neoadjuvant Chemotherapy

Neoadjuvant chemotherapy based on anthracyclines and ifosfamide for high-risk soft tissue sarcomas (STS) of the extremities and trunk is a controversial treatment option. There are substantial interindividual differences in clinical outcomes in patients treated with neoadjuvant chemotherapy. The aim of this study was to evaluate, as biomarkers, polymorphisms in genes encoding drug-metabolizing enzymes, drug transporters, or drug targets and their association with toxicity and survival in STS patients treated with neoadjuvant chemotherapy. We analysed variants in genes involved in anthracycline metabolism (ABCB1, ABCC2, NQO1, CBR3, and SLC22A16) and in ifosfamide catabolism (ALDH1A1) in 79 treated patients. Two genes showed significant association after adjusted multivariate analysis: ABCC2 and ALDH1A1. In patients treated with anthracyclines, ABCC2 rs3740066 was associated with risk of febrile neutropenia (p = 0.031), and with decreased overall survival (OS) (p = 0.024). ABCC2 rs2273697 was associated with recurrence-free survival (RFS) (p = 0.024). In patients treated with ifosfamide, ALDH1A1 rs3764435 was associated with RFS (p = 0.046). Our pharmacogenetic study shows for the first time that variants in genes regulating the metabolism of neoadjuvant chemotherapy may be helpful to predict toxicity and survival benefit in high-risk STS treated with neoadjuvant chemotherapy. Further validation studies are needed to establish their clinical utility.

Characteristics and Clinical Implication of UGT1A1 Heterozygous Mutation in Tumor

BACKGROUND

The literature recommends that reduced dosage of CPT-11 should be applied in patients with UGT1A1 homozygous mutations, but the impact of UGT1A1 heterozygous mutations on the adverse reactions of CPT-11 is still not fully clear.

METHODS

A total of 107 patients with UGT1A1 heterozygous mutation or wild-type, who were treated with CPT-11 from January 2018 to September 2021 in Peking University Third Hospital, were retrospectively enrolled. The adverse reaction spectra of patients with UGT1A1*6 and UGT1A1*28 mutations were analyzed. Adverse reactions were evaluated according to National Cancer Institute Common Terminology Criteria for Adverse Events (NCI-CTCAE) 5.0. The efficacy was evaluated according to Response Evaluation Criteria in Solid Tumors (RECIST) 1.1. The genotypes of UGT1A1*6 and UGT1A1*28 were detected by digital fluorescence molecular hybridization.

RESULTS

There were 43 patients with UGT1A1*6 heterozygous mutation, 26 patients with UGT1A1*28 heterozygous mutation, 8 patients with UGT1A1*6 and UGT1A1*28 double heterozygous mutations, 61 patients with heterozygous mutation at any gene locus of UGT1A1*6 and UGT1A1*28. Logistic regression analysis showed that the presence or absence of vomiting (P=0.013) and mucositis (P=0.005) was significantly correlated with heterozygous mutation of UGT1A1*28, and the severity of vomiting (P<0.001) and neutropenia (P=0.021) were significantly correlated with heterozygous mutation of UGT1A1*6. In colorectal cancer, UGT1A1*6 was significantly correlated to diarrhea (P=0.005), and the other adverse reactions spectrum was similar to that of the whole patient cohort, and efficacy and prognosis were similar between patients with different genotypes and patients treated with reduced CPT-11 dosage or not.

CONCLUSIONS

In clinical use, heterozygous mutations of UGT1A1*6 and UGT1A1*28 are related to the risk and severity of vomiting, diarrhea, neutropenia and mucositis in patients with Pan-tumor and colorectal cancer post CPT-11 therpy. In colorectal cancer, UGT1A1*6 is significantly related to diarrhea post CPT-11 use, efficacy and prognosis is not affected by various genotypes or CPT-11 dosage reduction.

Impact of UGT1A1 Polymorphisms on Febrile Neutropenia in Pancreatic Cancer Patients Receiving FOLFIRINOX: A Single-Center Cohort Study

FOLFIRINOX (oxaliplatin, leucovorin, irinotecan, and 5-fluorouracil) is a first-line chemotherapy for metastatic pancreatic cancer (PC). Chemotherapy-induced neutropenia is one of the most serious adverse events associated with advanced PC. Although UGT1A1 polymorphisms are associated with the metabolism of irinotecan, their role as surrogate markers for FOLFIRINOX-induced neutropenia has not been confirmed. We investigated risk factors for FN-in particular, UGT1A1 polymorphisms-in PC patients receiving FOLFIRINOX, using a single-center cohort registry. To investigate the association between UGT1A1 polymorphisms and FN, we divided patients into three groups based on the predicted UGT1A1 phenotype: extensive metabolizer (EM) vs. intermediate metabolizer (IM) vs. poor metabolizer (PM). A total of 154 patients (FN group (n = 31) vs. non-FN group (n = 123)) receiving first-line FOLFIRINOX were identified between December 2017 and July 2020. The Cox regression analysis showed that female sex (HR: 2.20; p = 0.031), Eastern Cooperative Oncology Group performance status = 1 (HR: 2.83; p = 0.008), UGT1A1 IM (HR: 4.30; p = 0.004), and UGT1A1 PM (HR: 4.03; p = 0.028) were statistically significant risk factors for FN. We propose that UGT1A1 is the strongest predictive factor for FN and that this gene should be screened prior to the administration of chemotherapy.

Implementing Pre-Therapeutic UGT1A1 Genotyping in Clinical Practice: A Real-Life Study

Current guidelines recommend pre-therapeutic UGT1A1 genotyping to guide irinotecan dosing, but the usefulness of this approach remains to be clarified. In 247 patients with advanced gastrointestinal cancers undergoing irinotecan-based chemotherapy, we prospectively performed UGT1A1*28 genotyping and we analyzed the incidence of severe neutropenia according to genotype-guided dose reductions. Overall, 28 (11.3%) and 92 (37.2%) patients were homozygous or heterozygous UGT1A1*28 carriers, respectively. Grade ≥ 3 neutropenia was reported in 39% of homozygous patients receiving an upfront dose reduction of irinotecan (median 40%, range 22–58%), in 20% of heterozygous or wild-type patients receiving full dose (OR_{vs*28/*28 genotype} = 0.38; 95% CI: 0.14–1.03; p = 0.058), and in 15.3% of those receiving a reduced dose for clinical reasons (OR _{vs*28/*28 genotype} = 0.28, 95% IC: 0.12–0.67; p = 0.004). Occurrence of severe neutropenia was inversely associated with dose reduction in UGT1A1*28 homozygous carriers (OR_{x10 unit} = 0.62, 95% CI: 0.27–1.40, p = 0.249) and UGT1A1 heterozygous or wild-type patients (OR_{x10 unit} = 0.87, 95% CI: 0.59–1.28, p = 0.478). Incidence of severe neutropenia was related to irinotecan doses and UGT1A1 polymorphisms. Upfront irinotecan dose reductions do not reduce the burden of grade ≥ 3 neutropenia in UGT1A1*28 homozygous carriers.

UGT1A1 genotype-guided dosing of irinotecan: A prospective safety and cost analysis in poor metaboliser patients

AIM

To determine the safety, feasibility, pharmacokinetics, and cost of UGT1A1 genotype-guided dosing of irinotecan.

PATIENTS AND METHODS

In this prospective, multicentre, non-randomised study, patients intended for treatment with irinotecan were pre-therapeutically genotyped for UGT1A1∗28 and UGT1A1∗93. Homozygous variant carriers (UGT1A1 poor metabolisers; PMs) received an initial 30% dose reduction. The primary endpoint was incidence of febrile neutropenia in the first two cycles of treatment. Toxicity in UGT1A1 PMs was compared to a historical cohort of UGT1A1 PMs treated with full dose therapy, and to UGT1A1 non-PMs treated with full dose therapy in the current study. Secondary endpoints were pharmacokinetics, feasibility, and costs.

RESULTS

Of the 350 evaluable patients, 31 (8.9%) patients were UGT1A1 PM and received a median 30% dose reduction. The incidence of febrile neutropenia in this group was 6.5% compared to 24% in historical UGT1A1 PMs (P = 0.04) and was comparable to the incidence in UGT1A1 non-PMs treated with full dose therapy. Systemic exposure of SN-38 of reduced dosing in UGT1A1 PMs was still slightly higher compared to a standard-dosed irinotecan patient cohort (difference: +32%). Cost analysis showed that genotype-guided dosing was cost-saving with a cost reduction of €183 per patient.

CONCLUSION

UGT1A1 genotype-guided dosing significantly reduces the incidence of febrile neutropenia in UGT1A1 PM patients treated with irinotecan, results in a therapeutically effective systemic drug exposure, and is cost-saving. Therefore, UGT1A1 genotype-guided dosing of irinotecan should be considered standard of care in order to improve individual patient safety.

A nanotherapeutic strategy to overcome chemoresistance to irinotecan/7-ethyl-10-hydroxy-camptothecin in colorectal cancer

Clinical development of 7-ethyl-10‑hydroxy-camptothecin (SN38), the active metabolite of irinotecan (CPT-11), is hindered by its insolubility and poor stability. Another obstacle is that tumors could become resistant to SN38/CPT-11 through multiple mechanisms involving breast cancer resistance protein (BCRP). Herein one of the most potent and selective BCRP inhibitors, Ko143, is encapsulated into a recently constructed prodrug PEG-S-S-SN38 displaying a high and fixed drug loading, multiple intratumoral stimuli (oxidative stress, GSH and esterase)-responsive drug release and significant in vitro and in vivo superiorities over CPT-11. The obtained "combo" for simultaneous delivery of SN38 and Ko143, named as BI@PEG-SN38, has a high SN38 loading efficacy (14.85 wt.%) and a good Ko143 encapsulation efficacy (3.79%). Through generating panels of human colorectal cancer models expressing altered levels of BCRP via lentiviral transfection and CRISPR-Cas9, characteristics of different drug formulations are carefully evaluated. Impressively, BI@PEG-SN38 nanoparticles effectively reverse chemoresistance to CPT-11 (resistance index dropping from ∼274.00-456.00 to ∼1.70-4.68) and PEG-S-S-SN38 (resistance index dropping from ∼5.83-14.00 to ∼1.70-4.68) in three BCRP-overexpressing cancer cell lines. More importantly, reversal of BCRP-mediated chemoresistance to CPT-11 (P values lower than 0.001-0.0001) and PEG-S-S-SN38 (P values lower than 0.01-0.001) by BI@PEG-SN38 nanoparticles are further confirmed with two panels of colorectal cancer xenograft models in vivo. As the first nano-formulation of Ko143 and the first systemic co-delivery vehicle of SN38/CPT-11 and a BCRP inhibitor, BI@PEG-SN38 provides a new approach for resolving the bottlenecks for clinical translation of SN38 and numerous "chemosensitizers" like Ko143, and exhibits promising applicability in precision cancer medicine. STATEMENT OF SIGNIFICANCE: To resolve the bottlenecks in clinical application of anticancer agents SN38/CPT-11 and the most potent breast cancer resistant protein (BCRP) inhibitor Ko143, a "combo" nanotherapeutic simultaneously delivering SN38 and Ko143 was constructed and named as BI@PEG-SN38. By generating panels of colorectal cancer models, we demonstrate that BI@PEG-SN38 nanoparticles effectively and selectively reversed BCRP-mediated tumor resistance to SN38/CPT-11 in vitro and in vivo. As the first nano-formulation of Ko143 and the first systemic co-delivery vehicle of SN38/CPT-11 and a BCRP inhibitor, BI@PEG-SN38 provides a new strategy for clinical development of SN38 and numerous "chemosensitizers", and exhibits promising applicability in precision cancer medicine. Panels of cancer cell lines established here provides a useful platform for BCRP- and cancer-related research and technology development.

All You Need to Know About UGT1A1 Genetic Testing for Patients Treated With Irinotecan: A Practitioner-Friendly Guide

Irinotecan is an anticancer agent widely used for the treatment of solid tumors, including colorectal and pancreatic cancers. Severe neutropenia and diarrhea are common dose-limiting toxicities of irinotecan-based therapy, and UGT1A1 polymorphisms are one of the major risk factors of these toxicities. In 2005, the US Food and Drug Administration revised the drug label to indicate that patients with UGT1A1*28 homozygous genotype should receive a decreased dose of irinotecan. However, UGT1A1*28 testing is not routinely used in the clinic, and specific reasons include lack of access to concise information on this wide issue as well as mixed recommendations by regulatory and professional entities. To assist oncologists in assessing whether and when to use UGT1A1 genetic testing in patients receiving irinotecan-based therapies, this article provided (1) essential knowledge of UGT1A1 polymorphisms; (2) an update on the impact of UGT1A1 polymorphisms on efficacy and toxicity of contemporary irinotecan-based regimens; (3) dosing adjustments based upon the UGT1A1 genotypes, and (4) recommendations from currently available guidelines from the US and international scientific consortia and major oncology societies.

Integration of DNA sequencing with population pharmacokinetics to improve the prediction of irinotecan exposure in cancer patients

BACKGROUND

Irinotecan (CPT-11) is an anticancer agent widely used to treat adult solid tumours. Large interindividual variability in the clearance of irinotecan and SN-38, its active and toxic metabolite, results in highly unpredictable toxicity.

METHODS

In 217 cancer patients treated with intravenous irinotecan single agent or in combination, germline DNA was used to interrogate the variation in 84 genes by next-generation sequencing. A stepwise analytical framework including a population pharmacokinetic model with SNP- and gene-based testing was used to identify demographic/clinical/genetic factors that influence the clearance of irinotecan and SN-38.

RESULTS

Irinotecan clearance was influenced by rs4149057 in SLCO1B1, body surface area, and co-administration of 5-fluorouracil/leucovorin/bevacizumab. SN-38 clearance was influenced by rs887829 in UGT1A1, pre-treatment total bilirubin, and EGFR rare variant burden. Within each UGT1A1 genotype group, elevated pre-treatment total bilirubin and/or presence of at least one rare variant in EGFR resulted in significantly lower SN-38 clearance. The model reduced the interindividual variability in irinotecan clearance from 38 to 34% and SN-38 clearance from 49 to 32%.

CONCLUSIONS

This new model significantly reduced the interindividual variability in the clearance of irinotecan and SN-38. New genetic factors of variability in clearance have been identified.

Dimeric Artesunate-Phosphatidylcholine-Based Liposomes for Irinotecan Delivery as a Combination Therapy Approach

In this work, dimeric artesunate-phosphatidylcholine conjugate (dARTPC)-based liposomes encapsulated with irinotecan (Ir) were developed for anticancer combination therapy. First, dARTPC featured with unique amphipathic properties formed liposomes by classical thin-film methods. After that, Ir was encapsulated into dARTPC-based liposomes (Ir/dARTPC-LP) by the triethylammonium sucrose octasulfate gradient method. Physicochemical characterization indicated that Ir/dARTPC-LP had a mean size of around 140 nm and a negative ζ potential of approximately -30 mV. Most noticeably, liposomes displayed an encapsulation efficiency of greater than 98% with a controllable drug loading of 4-22%. The in vitro release of dihydroartemisinin (DHA) and Ir from Ir/dARTPC-LP was investigated by dialysis in different media. It was found that effective release of both DHA (65.42%) and Ir (77.28%) in a weakly acidic medium (pH 5.0) after 48 h was achieved in comparison to very slow release under a neutral environment (DHA 9.90% and Ir 8.72%), indicating the controllable release of both drugs. Confocal laser scanning microscopy confirmed the improved cellular internalization of Ir/dARTPC-LP. The cytotoxicity of Ir/dARTPC-LP was evaluated in the MCF-7, A549, and HepG2 cell lines. The results showed that Ir/dARTPC-LP had significant synergistic efficacy in the loss of cell growth. In vivo anticancer evaluation was performed using a 4T1 xenograft tumor model. Ir/dARTPC-LP had a high tumor inhibition rate of 62.7% without significant toxicity in comparison with the injection of Ir solution. Taken together, dARTPC encapsulated with Ir has great potential for anticancer combination therapy.

Elucidating the role of pharmacogenetics in irinotecan efficacy and adverse events in metastatic colorectal cancer patients

INTRODUCTION

Irinotecan is a cytotoxic agent that is widely used in the treatment of several types of solid tumors. However, although it is generally well tolerated, approximately 20% to 35% of patients develop severe toxicity, particularly delayed-type diarrhea and neutropenia. As the incidence of such toxicities is often associated with the UGT1A1 *28/*28, *6/*28 and *6/*6 genotypes, individualized dosing could reduce these adverse events. Furthermore, prospective trials have shown that patients harboring the UGT1A1 *1/*1 and *1/*28 genotypes can tolerate higher doses of irinotecan, which may in turn impact on a better outcome. Upfront UGT1A1 genotyping could therefore be a usefulness strategy in order to individualize irinotecan dosing, but consensus on the recommended dose based on the UGT1A1 genotype is still lacking.

AREAS COVERED

This review summarizes the results of the main pharmacogenetic studies focused on irinotecan. We provide an overview of current evidence and recommendations for individualized dosing of irinotecan in metastatic colorectal cancer patients.

EXPERT OPINION

Implementation of UGT1A1*28 and UGT1A1*6 genotyping in clinical practice is a first step toward personalizing irinotecan therapy. This approach is likely to improve patient care and reduce healthcare costs. Future large and prospective studies will help to clarify the clinical value of other genetic markers in irinotecan treatment personalization.

Evaluation of pharmacogenomics and hepatic nuclear imaging-related covariates by population pharmacokinetic models of irinotecan and its metabolites

BACKGROUND

Body surface area (BSA)-based dosing of irinotecan (IR) does not account for its pharmacokinetic (PK) and pharmacodynamic (PD) variabilities. Functional hepatic nuclear imaging (HNI) and excretory/metabolic/PD pharmacogenomics have shown correlations with IR disposition and toxicity/efficacy. This study reports the development of a nonlinear mixed-effect population model to identify pharmacogenomic and HNI-related covariates that impact on IR disposition to support dosage optimization.

METHODS

Patients had advanced colorectal cancer treated with IR combination therapy. Baseline blood was analysed by Affymetrix DMET™ Plus Array and, for PD, single nucleotide polymorphisms (SNPs) by Sanger sequencing. For HNI, patients underwent ^99mTc-IDA hepatic imaging, and data was analysed for hepatic extraction/excretion parameters. Blood was taken for IR and metabolite (SN38, SN38G) analysis on day 1 cycle 1. Population modelling utilised NONMEM version 7.2.0, with structural PK models developed for each moiety. Covariates include patient demographics, HNI parameters and pharmacogenomic variants.

RESULTS

Analysis included (i) PK data: 32 patients; (ii) pharmacogenomic data: 31 patients: 750 DMET and 22 PD variants; and (iii) HNI data: 32 patients. On initial analysis, overall five SNPs were identified as significant covariates for CL_SN38. Only UGT1A3_c.31 T > C and ABCB1_c.3435C > T were included in the final model, whereby CL_SN38 reduced from 76.8 to 55.1%.

CONCLUSION

The identified UGT1A3_c.31 T > C and ABCB1_c.3435C > T variants, from wild type to homozygous, were included in the final model for SN38 clearance.

Impact of UGT1A1 genotype on the efficacy and safety of irinotecan-based chemotherapy in metastatic colorectal cancer

The phase III AXEPT study showed the noninferiority of modified capecitabine plus irinotecan (mXELIRI) with or without bevacizumab relative to fluorouracil, leucovorin, and irinotecan (FOLFIRI) with or without bevacizumab as a second‐line treatment for metastatic colorectal cancer. We evaluated the associations between the UGT1A1 genotype linked to adverse events—caused by irinotecan—and the efficacy and safety of mXELIRI and FOLFIRI. The UGT1A1 genotype was prospectively determined and patients were categorized into three groups according to WT (*1/*1), single heterozygous (SH; *28/*1 or *6/*1), and double heterozygous or homozygous (DHH; *28/*28, *6/*6, or *28/*6). Overall survival (OS), progression‐free survival, response rate, and safety were assessed. The UGT1A1 genotype was available in all 650 randomized patients (WT, 309 [47.5%]; SH, 291 [44.8%]; DHH, 50 [7.7%]). The median OS was 15.9, 17.7, and 10.6 months in the WT, SH, and DHH groups, respectively, with an adjusted hazard ratio (HR) of 1.53 (95% confidence interval [CI], 1.12‐2.09; P = .008) for DHH vs WT or SH. The median OS in the mXELIRI and FOLFIRI arms was 18.1 vs 14.3 months (HR 0.80; 95% CI, 0.62‐1.03) in the WT group, 16.3 vs 18.3 months (HR 1.04; 95% CI, 0.79‐1.36) in the SH group, and 13.0 vs 9.1 months (HR 0.71; 95% CI, 0.39‐1.31) in the DHH group, respectively. Modified capecitabine plus irinotecan with or without bevacizumab could be a standard second‐line chemotherapy in terms of efficacy and safety regardless of the UGT1A1 genotype.

A UGT1A1 variant is associated with serum total bilirubin levels, which are causal for hypertension in African-ancestry individuals

Serum bilirubin is associated with several clinical outcomes, including hypertension, type 2 diabetes (T2D), and drug metabolism. Here, we describe findings from our genome-wide association studies (GWAS) of serum (TBIL) using a generalized linear mixed model in West Africans (n = 1127), with adjustment for age, sex, body mass index, T2D, significant principal components of population structure, and cryptic relatedness. Genome-wide conditional analysis and CAVIARBF were used to fine map significant loci. The causal effect of TBIL on hypertension was assessed by Mendelian randomization (MR) using the GWAS findings as instrumental variables (IVs) in African Americans (n = 3,067). The SNP rs887829 (UGT1A1) was significantly associated with TBIL levels (effect allele (T) frequency = 0.49, β (SE) = 0.59 (0.04), p = 9.13 × 10^-54). Genome-wide conditional analysis and regional fine mapping pointed to rs887829 as a possible causal variant with a posterior inclusion probability of 0.99. The T allele of rs887829 is associated with lower hepatic expression of UGT1A1. Using rs887829 as an IV, two-stage least-squares MR showed a causal effect of bilirubin on hypertension (β = -0.76, 95% CI [-1.52, -0.01], p = 0.0459). Our finding confirms that UGT1A1 influences bilirubin levels. Notably, lower TBIL is causally associated with the increased risk of hypertension.

Minimal contribution of the hepatic uptake transporter OATP1B1 to the inter-individual variability in SN-38 pharmacokinetics in cancer patients without severe renal failure

PURPOSE

SN-38, a pharmacologically active metabolite of irinotecan, is taken up into hepatocytes by organic anion transporting polypeptide (OATP) 1B1. The effects of functional OATP1B1 521T>C on the pharmacokinetics of SN-38 remain controversial. Here, we prospectively examined the effects of OATP1B1 function on the area under the plasma total or unbound concentration-time curve (tAUC or uAUC) of SN-38 by assessing OATP1B1 521T>C and the plasma levels of endogenous OATP1B1 substrates, coproporphyrin (CP)-I and III, in cancer patients treated with irinotecan.

METHODS

We enrolled cancer patients who were treated with an irinotecan-containing regimen and did not have severe renal failure. The total and unbound concentrations of SN-38 in the plasma were measured by high-performance liquid chromatography. AUC values were calculated and normalized to the actual irinotecan dose (AUC/dose). The OATP1B1 521T>C was analyzed by direct sequencing. Concentrations of the endogenous substrates in plasma before irinotecan treatment (baseline) were determined by liquid chromatography with tandem mass spectrometry.

RESULTS

Twenty-two patients with a median estimated glomerular filtration rate of 74.8 mL/min (range 32.6-99.6) were examined. Both tAUC/dose and uAUC/dose were associated with the grade of neutropenia; however, they were not associated with OATP1B1 521T>C or baseline CP-I and III levels. It is worth noting that these baseline concentrations were significantly higher in patients with OATP1B1 521C, supporting functional changes in OATP1B1.

CONCLUSION

The contribution of OATP1B1 activity to inter-patient variability in the systemic exposure to SN-38 is likely minimal in patients without severe renal failure.

Pharmacometrics-Based Considerations for the Design of a Pharmacogenomic Clinical Trial Assessing Irinotecan Safety

PURPOSE

Pharmacometric models provide useful tools to aid the rational design of clinical trials. This study evaluates study design-, drug-, and patient-related features as well as analysis methods for their influence on the power to demonstrate a benefit of pharmacogenomics (PGx)-based dosing regarding myelotoxicity.

METHODS

Two pharmacokinetic and one myelosuppression model were assembled to predict concentrations of irinotecan and its metabolite SN-38 given different UGT1A1 genotypes (poor metabolizers: CLSN-38: -36%) and neutropenia following conventional versus PGx-based dosing (350 versus 245 mg/m2 (-30%)). Study power was assessed given diverse scenarios (n = 50-400 patients/arm, parallel/crossover, varying magnitude of CLSN-38, exposure-response relationship, inter-individual variability) and using model-based data analysis versus conventional statistical testing.

RESULTS

The magnitude of CLSN-38 reduction in poor metabolizers and the myelosuppressive potency of SN-38 markedly influenced the power to show a difference in grade 4 neutropenia (<0.5·109 cells/L) after PGx-based versus standard dosing. To achieve >80% power with traditional statistical analysis (χ2/McNemar's test, α = 0.05), 220/100 patients per treatment arm/sequence (parallel/crossover study) were required. The model-based analysis resulted in considerably smaller total sample sizes (n = 100/15 given parallel/crossover design) to obtain the same statistical power.

CONCLUSIONS

The presented findings may help to avoid unfeasible trials and to rationalize the design of pharmacogenetic studies.

Pharmacogenomics and functional imaging to predict irinotecan pharmacokinetics and pharmacodynamics: the predict IR study

PURPOSE

Irinotecan (IR) displays significant PK/PD variability. This study evaluated functional hepatic imaging (HNI) and extensive pharmacogenomics (PGs) to explore associations with IR PK and PD (toxicity and response).

METHODS

Eligible patients (pts) suitable for Irinotecan-based therapy. At baseline: (i) PGs: blood analyzed by the Affymetrix-DMET™-Plus-Array (1936 variants: 1931 single nucleotide polymorphisms [SNPs] and 5 copy number variants in 225 genes, including 47 phase I, 80 phase II enzymes, and membrane transporters) and Sanger sequencing (variants in HNF1A, Topo-1, XRCC1, PARP1, TDP, CDC45L, NKFB1, and MTHFR), (ii) HNI: pts given IV 250 MBq-^99mTc-IDA, data derived for hepatic extraction/excretion parameters (CL_HNI, T_1/2-HNI, 1hRET, HEF, T_d1/2). In cycle 1, blood was taken for IR analysis and PK parameters were derived by non-compartmental methods. Associations were evaluated between HNI and PGs, with IR PK, toxicity, objective response rate (ORR) and progression-free survival (PFS).

RESULTS

N = 31 pts. The two most significant associations between PK and PD with gene variants or HNI parameters (P < 0.05) included: (1) PK: SN38-Metabolic Ratio with CL_HNI, 1hRET, (2) Grade 3+ diarrhea with SLC22A2 (rs 316019), GSTM5 (rs 1296954), (3) Grade 3+ neutropenia with CL_HNI, 1hRET, SLC22A2 (rs 316019), CYP4F2 (rs2074900) (4) ORR with ALDH2 (rs 886205), MTHFR (rs 1801133). (5) PFS with T_1/2-HNI, XDH (rs 207440), and ABCB11 (rs 4148777).

CONCLUSIONS

Exploratory associations were observed between Irinotecan PK/PD with hepatic functional imaging and extensive pharmacogenomics. Further work is required to confirm and validate these findings in a larger cohort of patients.

AUSTRALIAN NEW ZEALAND CLINICAL TRIALS REGISTRY (ANZCTR) NUMBER

ACTRN12610000897066, Date registered: 21/10/2010.

Integrated chromatin and transcriptomic profiling of patient-derived colon cancer organoids identifies personalized drug targets to overcome oxaliplatin resistance

Colorectal cancer is a leading cause of cancer deaths. Most colorectal cancer patients eventually develop chemoresistance to the current standard-of-care therapies. Here, we used patient-derived colorectal cancer organoids to demonstrate that resistant tumor cells undergo significant chromatin changes in response to oxaliplatin treatment. Integrated transcriptomic and chromatin accessibility analyses using ATAC-Seq and RNA-Seq identified a group of genes associated with significantly increased chromatin accessibility and upregulated gene expression. CRISPR/Cas9 silencing of fibroblast growth factor receptor 1 (FGFR1) and oxytocin receptor (OXTR) helped overcome oxaliplatin resistance. Similarly, treatment with oxaliplatin in combination with an FGFR1 inhibitor (PD166866) or an antagonist of OXTR (L-368,899) suppressed chemoresistant organoids. However, oxaliplatin treatment did not activate either FGFR1 or OXTR expression in another resistant organoid, suggesting that chromatin accessibility changes are patient-specific. The use of patient-derived cancer organoids in combination with transcriptomic and chromatin profiling may lead to precision treatments to overcome chemoresistance in colorectal cancer.

ABCB1, ABCG2, ABCC1, ABCC2, and ABCC3 drug transporter polymorphisms and their impact on drug bioavailability: what is our current understanding?

INTRODUCTION

Interindividual differences in drug response are a frequent clinical challenge partly due to variation in pharmacokinetics. ATP-binding cassette (ABC) transporters are crucial determinants of drug disposition. They are subject of gene regulation and drug-interaction; however, it is still under debate to which extend genetic variants in these transporters contribute to interindividual variability of a wide range of drugs.

AREAS COVERED

This review discusses the current literature on the impact of genetic variants in ABCB1, ABCG2 as well as ABCC1, ABCC2, and ABCC3 on pharmacokinetics and drug response. The aim was to evaluate if results from recent studies would increase the evidence for potential clinically relevant pharmacogenetic effects.

EXPERT OPINION

Although enormous efforts have been made to investigate effects of ABC transporter genotypes on drug pharmacokinetics and response, the majority of studies showed only weak if any associations. Despite few unique results, studies mostly failed to confirm earlier findings or still remained inconsistent. The impact of genetic variants on drug bioavailability is only minor and other factors regulating the transporter expression and function seem to be more critical. In our opinion, the findings on the so far investigated genetic variants in ABC efflux transporters are not suitable as predictive biomarkers.

The Road so Far in Colorectal Cancer Pharmacogenomics: Are We Closer to Individualised Treatment?

In recent decades, survival rates in colorectal cancer have improved greatly due to pharmacological treatment. However, many patients end up developing adverse drug reactions that can be severe or even life threatening, and that affect their quality of life. These remain a limitation, as they may force dose reduction or treatment discontinuation, diminishing treatment efficacy. From candidate gene approaches to genome-wide analysis, pharmacogenomic knowledge has advanced greatly, yet there is still huge and unexploited potential in the use of novel technologies such as next-generation sequencing strategies. This review summarises the road of colorectal cancer pharmacogenomics so far, presents considerations and directions to be taken for further works and discusses the path towards implementation into clinical practice.

Pharmacogenomic Assessment of Patients with Colorectal Cancer and Potential Treatments

Evolving intensiveness of colorectal cancer (CRC) treatment, including chemotherapeutics and targeted agents associations, in adjuvant and metastatic CRC (MCRC) settings, increased overall survival (OS) with individual variability of toxicity. Pharmacogenomic guidelines recommended pre-treatment identification of at-risk patients suggesting dose adjustment of fluoropyrimidines based on dihydropyrimidine dehydrogenase (DPYD), and irinotecan on UDP glucuronosyl-transferase 1 family polypeptide A1 (UGT1A1) genetic variants, but they are poorly applied in clinical practice. This review highlighted clinically validated pharmacogenetic markers, to underline the need of their implementation in the multidisciplinary molecular board for individual CRC patients in clinical practice. Five clinically relevant DPYD variants with different prevalence impair enzymatic effectiveness and significantly increase toxicity: c.1236 G>A (c.1129–5923 C>G, HapB3), 4.1–4.8%; c.1679 T>G (DPYD*13), c.1905+1G>A (DPYD*2A), c.2846 A>T, c.2194 A>T (DPYD*6) 1% each. c.1679T>G and c.1905+1G>A are most deleterious on DPD effectiveness, moderately reduced in c.1236/HapB3 and c.2846A>T. Cumulatively, these variants explain approximately half of the estimated 10–15% fluoropyrimidine-related gastrointestinal and hematological toxicities due to DPD. Prevalent UGT1A1 gene [TA]₇TAA promoter allelic variant UGT1A1*28, characterized by an extra TA repeat, is associated with low transcriptional and reduced enzymatic effectiveness, decreased SN38 active irinotecan metabolite glucuronidation, vs wild-type UGT1A1*1 [A(TA)6TAA]. Homozygote UGT1A1*28 alleles patients are exposed to higher hematological and gastrointestinal toxicities, even more than heterozygote, at >150 mg/m² dose. Dose reduction is recommended for homozygote variant. Wild-type UGT1A1*28 alleles patients could tolerate increased doses, potentially affecting favorable outcomes. Implementation of up-front evaluation of the five validated DPYD variants and UGT1A1*28 in the multidisciplinary molecular tumor board, also including CRC genetic characterization, addresses potential treatments with fluoropyrimidines and irinotecan associations at proper doses and schedules, particularly for early CRC, MCRC patients fit for intensive regimens or unfit for conventional regimens, requiring treatment modulations, and also for patients who experience severe, unexpected toxicities. Integration of individual evaluation of toxicity syndromes (TS), specifically limiting TS (LTS), an innovative indicator of toxicity burden in individual patients, may be useful to better evaluate relationships between pharmacogenomic analyses with safety profiles and clinical outcomes.

Irinotecan-Still an Important Player in Cancer Chemotherapy: A Comprehensive Overview

Irinotecan has been used in the treatment of various malignancies for many years. Still, the knowledge regarding this drug is expanding. The pharmacogenetics of the drug is the crucial component of response to irinotecan. Furthermore, new formulations of the drug are introduced in order to better deliver the drug and avoid potentially life-threatening side effects. Here, we give a comprehensive overview on irinotecan’s molecular mode of action, metabolism, pharmacogenetics, and toxicity. Moreover, this article features clinically used combinations of the drug with other anticancer agents and introduces novel formulations of drugs (e.g., liposomal formulations, dendrimers, and nanoparticles). It also outlines crucial mechanisms of tumor cells’ resistance to the active metabolite, ethyl-10-hydroxy-camptothecin (SN-38). We are sure that the article will constitute an important source of information for both new researchers in the field of irinotecan chemotherapy and professionals or clinicians who are interested in the topic.

ABCB1 Genetic Variants as Predictors of Irinotecan-Induced Severe Gastrointestinal Toxicity in Metastatic Colorectal Cancer Patients

Irinotecan is widely used in the treatment of metastatic colorectal cancer (mCRC) despite its severe toxicities. Toxicity is often associated with the UGT1A1*28/*28 genotype. An explanation for idiopathic toxicity beyond the UGT1A1 biomarker, however, remains a major concern for clinicians. One of the main irinotecan transporters is P-glycoprotein (P-gp), which is a hepatic efflux pump encoded by ABCB1. P-gp is involved in the biliary excretion of irinotecan and its active metabolite SN-38. We aimed to assess whether functional variants in ABCB1 also contribute to identifying patients at risk of toxicity. A cohort of 308 mCRC patients treated with irinotecan-based regimens were genotyped for polymorphisms in ABCB1 (rs1128503, rs2032582, and rs1045642). The effect of these variants and their haplotypes on irinotecan-induced severe toxicity (diarrhea, neutropenia, asthenia, nausea, and mucositis) was assessed. After adjusting for the relevant clinical and pathological parameters in the multivariate analysis, we found rs1128503 was significantly associated with severe diarrhea and mucositis (P=0.014 and P=0.002, respectively). Additionally, rs2032582 was associated with severe mucositis (P<0.001). Our results show that rs1128503 genotyping could help to predict severe gastrointestinal toxicity induced by irinotecan.

Optimal Sampling Strategies for Irinotecan (CPT-11) and its Active Metabolite (SN-38) in Cancer Patients

Irinotecan (CPT-11) is an anticancer agent widely used in the treatment of a variety of adult solid tumors. The objective of this study was to develop an optimal sampling strategy model that accurately estimates pharmacokinetic parameters of CPT-11 and its active metabolite, SN-38. This study included 221 patients with advanced solid tumors or lymphoma receiving CPT-11 single or combination therapy with 5-fluorouracil (5-FU)/leucovorin (LV) (FOLFIRI) plus bevacizumab from 4 separate clinical trials. Population pharmacokinetic analysis of CPT-11 and SN-38 was performed by non-linear mixed effects modeling. The optimal sampling strategy model was developed using D-optimality with expected distribution approach. The pharmacokinetic profiles of CPT-11 and SN-38 were best described by a 3- and 2-compartment model, respectively, with first-order elimination. Body surface area and co-administration with 5-FU/LV plus bevacizumab were significant covariates (p < 0.01) for volumes of the central compartment of CPT-11 and SN-38, and clearance of CPT-11. Pre-treatment total bilirubin and co-administration with 5-FU/LV and bevacizumab were significant covariates (p < 0.01) for clearance of SN-38. Accurate and precise predictive performance (r² > 0.99, -2 < bias (%ME) < 0, precision (% RMSE) < 12) of both CPT-11 and SN-38 was achieved using: (i) 6 fixed sampling times collected at 1.5, 3.5, 4, 5.75, 22, 23.5 hours post-infusion; or (ii) 1 fixed time and 2 sampling windows collected at 1.5, [3-5.75], [22-23.5] hours post-infusion. The present study demonstrates that an optimal sampling design with three blood samples achieves accurate and precise pharmacokinetic parameter estimates for both CPT-11 and SN-38.

Enzyme and Transporter Kinetics for CPT-11 (Irinotecan) and SN-38: An Insight on Tumor Tissue Compartment Pharmacokinetics Using PBPK

BACKGROUND

Computational tools are becoming more and more powerful and comprehensive as compared to past decades in facilitating pharmaceutical, pharmacological and clinical practice. Anticancer agents are used either as monotherapy or in combination therapy to treat malignant conditions of the body. A single antineoplastic agent may be used in different types of malignancies at different doses according to the stage of the disease.

OBJECTIVE

To study the behavior of CPT-11 (Irinotecan) and its metabolite SN-38 in tumor tissue compartment through the Whole Body-Physiologically Pharmacokinetics (WB-PBPK) and to determine the activity of metabolic enzymes and transporters participating in the disposition of CPT-11 and SN-38 working in their physiological environment inside the human body.

METHODS

Whole body PBPK approach is used to determine the activity of different metabolic enzymes and transporters involved in the disposition of CPT-11 and its active metabolite, SN-38. The concentrations and pharmacokinetic parameters of the parent compound and its metabolite administered at clinically applicable dose via the intravenous route in the tumor tissue are predicted using this approach.

RESULTS

The activity rate constants of metabolic enzymes and transporters of CPT-11 are derived at their natural anatomic locations. Concentration-time curves of CPT-11 and SN-38 with their 5th to 95th percentage range are achieved at the tumor tissue level. Mean tumor tissue pharmacokinetics of both compounds are determined in a population of 100 individuals.

CONCLUSION

Tumor tissue concentration-time curves of CPT-11 and SN-38 can be determined via PBPK modeling. Rate constants of enzymes and transporters can be shown for healthy and tumor bearing individuals. The results will throw light on the effective concentration of active compound at its target tissue at the clinically applied IV dose.

Individualization of Irinotecan Treatment: A Review of Pharmacokinetics, Pharmacodynamics, and Pharmacogenetics

Since its clinical introduction in 1998, the topoisomerase I inhibitor irinotecan has been widely used in the treatment of solid tumors, including colorectal, pancreatic, and lung cancer. Irinotecan therapy is characterized by several dose-limiting toxicities and large interindividual pharmacokinetic variability. Irinotecan has a highly complex metabolism, including hydrolyzation by carboxylesterases to its active metabolite SN-38, which is 100- to 1000-fold more active compared with irinotecan itself. Several phase I and II enzymes, including cytochrome P450 (CYP) 3A4 and uridine diphosphate glucuronosyltransferase (UGT) 1A, are involved in the formation of inactive metabolites, making its metabolism prone to environmental and genetic influences. Genetic variants in the DNA of these enzymes and transporters could predict a part of the drug-related toxicity and efficacy of treatment, which has been shown in retrospective and prospective trials and meta-analyses. Patient characteristics, lifestyle and comedication also influence irinotecan pharmacokinetics. Other factors, including dietary restriction, are currently being studied. Meanwhile, a more tailored approach to prevent excessive toxicity and optimize efficacy is warranted. This review provides an updated overview on today’s literature on irinotecan pharmacokinetics, pharmacodynamics, and pharmacogenetics.

Combination of germline variations associated with survival of folinic acid, fluorouracil and irinotecan-treated metastatic colorectal cancer patients

Aim: Germline variants could modify survival of metastatic colorectal cancer patients (mCRC). Patients & methods: The association of 285 haplotype-tagging SNPs in 11 candidate genes and overall survival (OS) was tested in two cohorts totalizing 417 FOLFIRI-treated mCRC. Gene expression was investigated in vitro and in public datasets. Results: In the combined cohort, CES1 rs9921399T>C was associated with prolonged OS (hazard ratio [HR] = 0.40) whereas ABCC1 rs17501011G>A (HR = 2.08) and UGT1 rs1113193G>A (HR = 2.12) were associated with shorter OS (p ≤ 0.005). A combined effect of these polymorphisms was observed with HR of 1.98-2.97 (p < 0.05). The ABCC1 rs17501011A variant reduced reporter-gene activity (p < 0.05) whereas ABCC1 tumor expression was associated with shorter survival (p ≤ 0.013). Conclusion: We identified a combination of genetic determinants that could predict mCRC survival.

High Potency of SN-38-Loaded Bovine Serum Albumin Nanoparticles Against Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) is an aggressive type of breast cancer with a worse prognosis than other types. There are currently no specific approved treatments for TNBC. Albumin is a promising biomimetic material that may be fabricated into nanoparticles to possibly exert passive effects on targeted tumors. Irinotecan has been extensively used in clinical settings, although a high dosage is required due to its low efficiency of conversion into the active metabolite SN-38, also known as 7-ethyl-10-hydroxy-camptothecin. The aim of this work was to optimize SN-38-loaded bovine serum albumin nanoparticles (sBSANPs) and evaluate their potency against TNBC. The sBSANPs were characterized by a small size of about 134-264 nm, a negative charge of -37 to -40 mV, an entrapment efficiency of 59-71%, and a particle yield of 65-86%. The cytotoxicity assays using sBSANPs showed a higher potency specifically against both MDA-MB-468 and MDA-MB-231 cells (ER-, PR-, HER2-) compared to MCF-7 (ER+, PR+, HER2-), and exhibited an extremely low IC₅₀ at the nanomolar levels (2.01-6.82 nM). The release profiles indicated that SN-38 presented an initial burst release within 12 h, and sBSANPs had a slow release pattern. Flow cytometry results showed that the fluorescence intensity of sBSANPs was significantly higher than that of the control group. The confocal images also confirmed that sBSANPs were taken up by MDA-MB-468 cells. Moreover, we found that a larger BSANP size resulted in an increased hemolytic effect. In vivo animal studies demonstrated that loading of SN-38 into bovine serum albumin nanoparticles could minimize the initial concentration without extending the elimination half-life, but significantly minimized the Cmax (p < 0.001) as compared with irinotecan treatment.