Irinogenetics: how many stars are there in the sky?

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.

Use of Personalized Biomarkers in Metastatic Colorectal Cancer and the Impact of AI

Colorectal cancer is a major cause of cancer-related death worldwide and is correlated with genetic and epigenetic alterations in the colonic epithelium. Genetic changes play a major role in the pathophysiology of colorectal cancer through the development of gene mutations, but recent research has shown an important role for epigenetic alterations. In this review, we try to describe the current knowledge about epigenetic alterations, including DNA methylation and histone modifications, as well as the role of non-coding RNAs as epigenetic regulators and the prognostic and predictive biomarkers in metastatic colorectal disease that can allow increases in the effectiveness of treatments. Additionally, the intestinal microbiota’s composition can be an important biomarker for the response to strategies based on the immunotherapy of CRC. The identification of biomarkers in mCRC can be enhanced by developing artificial intelligence programs. We present the actual models that implement AI technology as a bridge connecting ncRNAs with tumors and conducted some experiments to improve the quality of the model used as well as the speed of the model that provides answers to users. In order to carry out this task, we implemented six algorithms: the naive Bayes classifier, the random forest classifier, the decision tree classifier, gradient boosted trees, logistic regression and SVM.

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.

Pharmacogenetics and breast cancer management: current status and perspectives

INTRODUCTION

Breast cancer has benefited from a number of innovative therapeutics over the last decade. Cytotoxics, hormone therapy, targeted therapies and biologics can now be given to ensure optimal management of patients. As life expectancy of breast cancer patients has been significantly stretched and that several lines of treatment are now made available, determining the best drug or drug combinations to be primarily given and the best dosing and scheduling for each patient is critical for ensuring an optimal toxicity/efficacy balance.

AREAS COVERED

Defining patient's characteristics at the tumor level (pharmacogenomics) and the constitutional level (pharmacogenetics) is a rising trend in oncology. This review covers the latest strategies based upon the search of relevant biomarkers for efficacy, resistance and toxicity to be undertaken at the bedside to shift towards precision medicine in breast cancer patients.

EXPERT OPINION

In the expanding era of bioguided medicine, identifying relevant and clinically validated biomarkers from the plethora of published material remains an uneasy task. Sorting the variety of genetic and molecular markers that have been investigated over the last decade on their level of evidence and addressing the issue of drug exposure should help to improve the management of breast cancer therapy.

OATP1B1 and tumour OATP1B3 modulate exposure, toxicity, and survival after irinotecan-based chemotherapy

Background:

Treatment of advanced and metastatic colorectal cancer with irinotecan is hampered by severe toxicities. The active metabolite of irinotecan, SN-38, is a known substrate of drug-metabolising enzymes, including UGT1A1, as well as OATP and ABC drug transporters.

Methods:

Blood samples (n=127) and tumour tissue (n=30) were obtained from advanced cancer patients treated with irinotecan-based regimens for pharmacogenetic and drug level analysis and transporter expression. Clinical variables, toxicity, and outcomes data were collected.

Results:

SLCO1B1 521C was significantly associated with increased SN-38 exposure (P<0.001), which was additive with UGT1A1*28. ABCC5 (rs562) carriers had significantly reduced SN-38 glucuronide and APC metabolite levels. Reduced risk of neutropenia and diarrhoea was associated with ABCC2–24C/T (odds ratio (OR)=0.22, 0.06–0.85) and CES1 (rs2244613; OR=0.29, 0.09–0.89), respectively. Progression-free survival (PFS) was significantly longer in SLCO1B1 388G/G patients and reduced in ABCC2–24T/T and UGT1A1*28 carriers. Notably, higher OATP1B3 tumour expression was associated with reduced PFS.

Conclusions:

Clarifying the association of host genetic variation in OATP and ABC transporters to SN-38 exposure, toxicity and PFS provides rationale for personalising irinotecan-based chemotherapy. Our findings suggest that OATP polymorphisms and expression in tumour tissue may serve as important new biomarkers.

XELIRI compared with FOLFIRI as a second-line treatment in patients with metastatic colorectal cancer

The aim of this study was to compare the efficacy, safety and survival rate of a treatment regimen comprising capecitabine plus irinotecan (XELIRI) to those of a standard regimen comprising leucovorin, fluorouracil and irinotecan (FOLFIRI), to determine the correlation among the inherited genetic variations in UGT1A1, UGT1A7 and UGT1A9. A total of 84 consecutive patients with histologically confirmed metastatic colorectal cancer (mCRC) were included in the study. All patients were treated with FOLFIRI or XELIRI. The median progression-free survival time was 4.4 months for FOLFIRI and 5.7 months for XELIRI (hazard ratio=1.35; 95% confidence interval, 0.83-2.21; P=0.22). When compared with FOLFIRI (6.34%), XELIRI was associated with lower rates of severe toxicity (3.29) (P=0.026) and similar disease control rates (69.57% for FOLFIRI and 61.11% for XELIRI; P=0.49). In total, 17 single nucleotide polymorphisms were identified, five of which revealed an association with grade 3/4 neutropenia, including UGT1A7*4; however, UGT1A1*28 and UGT1A1*6, which have been previously reported, were not significant. Additionally, H2 haplotypes, which include UGT1A9*22, and H5 and H7 haplotypes, which include UGT1A7*2, UGT1A7*3 and UGT1A7*4, were associated with a higher risk of severe neutropenia. In conclusion, XELIRI is an effective treatment regimen with acceptable response rates and tolerability for mCRC patients as a second-line treatment. Furthermore, inherited genetic variations in UGT1A1, UGT1A7 and UGT1A9 are associated with grade 3/4 neutropenia.

Pregnane X Receptor (PXR) expression in colorectal cancer cells restricts irinotecan chemosensitivity through enhanced SN-38 glucuronidation

Background

Clinical efficacy of chemotherapy in colorectal cancer is subjected to broad inter-individual variations leading to the inability to predict outcome and toxicity. The topoisomerase I inhibitor irinotecan (CPT-11) is worldwide approved for the treatment of metastatic colorectal cancer and undergoes extensive peripheral and tumoral metabolism. PXR is a xenoreceptor activated by many drugs and environmental compounds regulating the expression of drug metabolism and transport genes in detoxification organs such as liver and gastrointestinal tract. Considering the metabolic pathway of irinotecan and the tissue distribution of Pregnane × Receptor (PXR), we hypothesized that PXR could play a key role in colon cancer cell response to irinotecan.

Results

PXR mRNA expression was quantified by RT-quantitative PCR in a panel of 14 colon tumor samples and their matched normal tissues. PXR expression was modulated in human colorectal cancer cells LS174T, SW480 and SW620 by transfection and siRNA strategies. Cellular response to irinotecan and its active metabolic SN38 was assessed by cell viability assays, HPLC metabolic profiles and mRNA quantification of PXR target genes. We showed that PXR was strongly expressed in colon tumor samples and displayed a great variability of expression. Expression of hPXR in human colorectal cancer cells led to a marked chemoresistance to the active metabolite SN38 correlated with PXR expression level. Metabolic profiles of SN38 showed a strong enhancement of SN38 glucuronidation to the inactive SN38G metabolite in PXR-expressing cells, correlated with an increase of UDPglucuronosyl transferases UGT1A1, UGT1A9 and UGT1A10 mRNAs. Inhibition of PXR expression by lentivirus-mediated shRNA, led to SN38 chemoresistance reversion concomitantly to a decrease of UGT1A1 expression and SN38 glucuronidation. Similarly, PXR mRNA expression levels correlated to UGT1A subfamily expression in human colon tumor biopsies.

Conclusion

Our results demonstrate that tumoral metabolism of SN38 is affected by PXR and point to potential therapeutic significance of PXR quantification in the prediction of irinotecan response. Furthermore, our observations are pharmacologically relevant since many patients suffering from cancer diseases are often exposed to co-medications, food additives or herbal supplements able to activate PXR. A substantial part of the variability observed among patients might be caused by such interactions

A CYP3A4 phenotype-based dosing algorithm for individualized treatment of irinotecan

PURPOSE

Irinotecan, the prodrug of SN-38, is extensively metabolized by cytochrome P450-3A4 (CYP3A4). A randomized trial was done to assess the utility of an algorithm for individualized irinotecan dose calculation based on a priori CYP3A4 activity measurements by the midazolam clearance test.

EXPERIMENTAL DESIGN

Patients were randomized to receive irinotecan at a conventional dose level of 350 mg/m(2) (group A) or doses based on an equation consisting of midazolam clearance, gamma-glutamyl-transferase, and height (group B). Pharmacokinetics and toxicities were obtained during the first treatment course.

RESULTS

Demographics of 40 evaluable cancer patients were balanced between both groups, including UGT1A1*28 genotype and smoking status. The absolute dose of irinotecan ranged from 480 to 800 mg in group A and 380 to 1,060 mg in group B. The mean absolute dose and area under the curve of irinotecan and SN-38 were not significantly different in either group (P > 0.18). In group B, the interindividual variability in the area under the curve of irinotecan and SN-38 was reduced by 19% and 25%, respectively (P > 0.22). Compared with group A, the incidence of grades 3 to 4 neutropenia was >4-fold lower in group B (45 versus 10%; P = 0.013). The incidence of grades 3 to 4 diarrhea was equal in both groups (10%).

CONCLUSIONS

Incorporation of CYP3A4 phenotyping in dose calculation resulted in an improved predictability of the pharmacokinetic and toxicity profile of irinotecan, thereby lowering the incidence of severe neutropenia. In combination with UGT1A1*28 genotyping, CYP3A4 phenotype determination should be explored further as a strategy for the individualization of irinotecan treatment.