Dutch pharmacogenetics working group (DPWG) guideline for the gene-drug interaction between UGT1A1 and irinotecan

The Dutch Pharmacogenetics Working Group (DPWG) aims to facilitate PGx implementation by developing evidence-based pharmacogenetics guidelines to optimize pharmacotherapy. This guideline describes the starting dose optimization of the anti-cancer drug irinotecan to decrease the risk of severe toxicity, such as (febrile) neutropenia or diarrhoea. Uridine diphosphate glucuronosyl transferase 1A1 (UGT1A1 encoded by the UGT1A1 gene) enzyme deficiency increases risk of irinotecan-induced toxicity. Gene variants leading to UGT1A1 enzyme deficiency (e.g. UGT1A1*6, *28 and *37) can be used to optimize an individual's starting dose thereby preventing carriers from toxicity. Homozygous or compound heterozygous carriers of these allele variants are defined as UGT1A1 poor metabolisers (PM). DPWG recommends a 70% starting dose in PM patients and no dose reduction in IM patients who start treatment with irinotecan. Based on the DPWG clinical implication score, UGT1A1 genotyping is considered "essential", indicating that UGT1A1 testing must be performed prior to initiating irinotecan treatment.

Pharmacovigilance of anti-cancer medicines: opportunities and challenges

INTRODUCTION

The foundations of pharmacovigilance are the monitoring of drug safety in real-world medicine, and identification of new adverse effects, unknown at the time of market approval. Cancer patients are prone to adverse drug reactions due to the complexity of the neoplastic disease and its treatment. Pharmacovigilance of anti-cancer medicines is further complicated because patients have comorbidities, as for elderly patients. It is even more challenging when complete safety and risk data for a drug are lacking, as may occur for new molecules or when it comes to drugs for children.

AREAS COVERED

This article introduces the field of pharmacovigilance of anti-cancer drugs, describing the various layers of complexity that make the recognition of adverse drug events in oncology particularly problematic, including the type of medicines, the phenomenon of underreporting and polypharmacy. Finally, it reviews new digital tools to help pharmacovigilance activities in oncology.

EXPERT OPINION

The authors outline some crucial challenges and opportunities that can be useful for pharmacovigilance to keep up with the times and follow the current technological and scientific progress. In addition to the evaluations made by researchers, it will, of course, be necessary to have an equality important concrete response from the institutions and regulatory bodies.

Genetic factors affecting drug disposition in Asian cancer patients

INTRODUCTION

In the era of genomic medicine, it is increasingly recognized that ethnogeographic differences in drug pharmacology exist between Asian and other populations. This is particularly pertinent to oncology, where drugs forming the backbone of chemotherapy often have narrow therapeutic windows and are frequently dosed close to maximally tolerable levels.

AREAS COVERED

At the population level, ancestry is important because historical-biogeographical confluences have shaped population genetics and pharmacoethnicity in the Asian race through allelic differentiation and interethnic differences in inheritance patterns of linkage disequilibrium. At the individual level, cis- and trans-acting germline polymorphisms and somatic mutations in genes encoding drug-metabolizing enzymes and transporters act in a multifactorial manner to determine drug disposition phenotype and clinical response in Asian cancer patients. A growing body of evidence also finds that complex genetic interactions and regulation, including a multiplicity of gene control mechanisms, are increasingly implicated in genotype-phenotype correlates than has hitherto been appreciated--potentially serving as the mechanistic links between hits in non-coding regions of genome-wide association studies and drug toxicity. Together, these genetic factors contribute to the clinical heterogeneity of drug disposition in Asian cancer patients.

EXPERT OPINION

This topic has broad relevance for the optimization and individualization of anticancer strategies in Asians.

Development of Pyrosequencing Method for Detection of UGT1A1 Polymorphisms in Thai Colorectal Cancers

BACKGROUND

UGT1A1 is a polymorphic enzyme that has been associated with irinotecan drug metabolisms. We developed a pyrosequencing method to detect allele frequency and genotype of UGT1A1 polymorphisms (UGT1A1*28 and UGT1A1*6) in Thai colorectal cancer patients.

METHOD

A pyrosequencing method was designed to determine UGT1A1 genetic polymorphisms including UGT1A1*28 (A[TA]7TAA) and UGT1A1*6 (211G>A) in 91 Thai colorectal cancers.

RESULT

Genotyping by the pyrosequencing technique was 100% concordant with capillary electrophoresis sequencing. The allele frequencies for UGT1A1 genetic polymorphisms were *1/*1 (54.95%), *1/*6 (13.19%), *1/*28 (25.27%), *28/*6 (4.40%), and *28/*28 (2.20%). No homozygous mutation UGT1A1*6 was found in our population.

CONCLUSIONS

We developed a rapid, reliable, more cost-effective, and simple assay to detect UGT1A1 genetic polymorphisms in routine practice before initiating irinotecan therapy. The UGT1A1*28 and UGT1A1*6 alleles were found to be similar in the Asian populations.

Pharmacovigilance in oncology: evaluation of current practice and future perspectives

RATIONALE, AIMS AND OBJECTIVES

Pharmacovigilance (PV), or drug safety monitoring, aims to improve patient safety through the detection and management of drug-related adverse reactions. It is implemented both by spontaneous reporting of adverse drug reactions (ADRs) and by careful detection of signals suggestive of drug toxicity. PV is an important clinical topic in clinical practice and pharmacotherapy, assuring the maintenance of a safe risk/benefit ratio throughout the commercial life cycle of a drug.

METHODS

We conducted a structured literature search on PubMed, Scopus, Cinahl and the Cochrane Library. We also performed manual searches in international databases of ADR individual reports to outline a structured profile on the topic. Our goal was to review key elements that affect safety monitoring of cancer drugs and their appropriate use, highlighting the strengths and weaknesses of PV in oncology.

RESULTS

This paper provides an understanding of the methodologies used by PV in current clinical practice and particularly in cancer drug therapy; a focus upon reporting of ADRs by health professionals and patients; and a focus upon methods used by PV to detect new signals of risk/harm related to medicines utilization.

CONCLUSION

To our knowledge, few articles focus upon the importance of PV and post-marketing surveillance of cancer drug therapies. Structured management of spontaneous reports of ADRs and data collection is essential to monitoring the safe use of drugs in this field in which pharmacotherapy is affected by high incidence of drug-related complications and by a narrow benefit/risk ratio.