High-resolution melting analysis of sequence variations in the cytidine deaminase gene (CDA) in patients with cancer treated with gemcitabine

A Phase Ib Open-Label, Dose-Escalation Study of NUC-1031 in Combination with Carboplatin for Recurrent Ovarian Cancer

PURPOSE

NUC-1031 is a first-in-class ProTide modification of gemcitabine. In PRO-002, NUC-1031 was combined with carboplatin in recurrent ovarian cancer.

PATIENTS AND METHODS

NUC-1031 was administered on days 1 and 8 with carboplatin on day 1 every 3 weeks for up to six cycles. Four dose cohorts of NUC-1031 (500, 625, and 750 mg/m²) with carboplatin (AUC4 or 5) were investigated. Primary endpoint was recommended phase II combination dose (RP2CD). Secondary endpoints included safety, investigator-assessed objective response rate (ORR), clinical benefit rate (CBR), progression-free survival (PFS), and pharmacokinetics.

RESULTS

A total of 25 women with recurrent ovarian cancer, a mean of 3.8 prior lines of chemotherapy, and a median platinum-free interval of 5 months (range: 7-451 days) were enrolled; 15 of 25 (60%) were platinum resistant, 9 (36%) were partially platinum sensitive, and 1 (4%) was platinum sensitive. Of the 23 who were response evaluable, there was 1 confirmed complete response (4%), 5 partial responses (17%), and 8 (35%) stable disease. The ORR was 26% and CBR was 74% across all doses and 100% in the RP2CD cohort. Median PFS was 27.1 weeks. NUC-1031 was stable in the plasma and rapidly generated high intracellular dFdCTP levels that were unaffected by carboplatin.

CONCLUSIONS

NUC-1031 combined with carboplatin is well tolerated in recurrent ovarian cancer. Highest efficacy was observed at the RP2CD of 500 mg/m² NUC-1031 on days 1 and 8 with AUC5 carboplatin day 1, every 3 weeks for six cycles. The ability to deliver carboplatin at AUC5 and the efficacy of this schedule even in patients with platinum-resistant disease makes this an attractive therapeutic combination.

Severe acute toxicity following gemcitabine administration: A report of four cases with cytidine deaminase polymorphisms evaluation

Gemcitabine (GCB) is a pyrimidine antimetabolite widely used in various solid tumors as a single agent or as a component of multidrug regimens. In the majority of patients, GCB is well tolerated, however life-threatening complications occasionally occur. The current report presents four cases of severe acute toxicity, which included two that were fatal, following administration of GCB alone or in combination with cisplatin. Of the four cases, in one, a Naranjo Adverse Drug Reaction Probability Score was definite, in two, probable and in one possible. To determine the potential causes of these toxicities, polymorphic variants of cytidine deaminase, the primary enzyme involved in the hepatic metabolism of GCB, were assessed. The homogeneous c.435TT variant was detected in one patient and a heterozygotic c.435CT variant in two, one of whom additionally harbored a heterozygotic c.79AC variant.

Pharmacokinetics and pharmacogenetics of Gemcitabine as a mainstay in adult and pediatric oncology: an EORTC-PAMM perspective

Gemcitabine is an antimetabolite ranking among the most prescribed anticancer drugs worldwide. This nucleoside analog exerts its antiproliferative action after tumoral conversion into active triphosphorylated nucleotides interfering with DNA synthesis and targeting ribonucleotide reductase. Gemcitabine is a mainstay for treating pancreatic and lung cancers, alone or in combination with several cytotoxic drugs (nab-paclitaxel, cisplatin and oxaliplatin), and is an option in a variety of other solid or hematological cancers. Several determinants of response have been identified with gemcitabine, i.e., membrane transporters, activating and inactivating enzymes at the tumor level, or Hedgehog signaling pathway. More recent studies have investigated how germinal genetic polymorphisms affecting cytidine deaminase, the enzyme responsible for the liver disposition of gemcitabine, could act as well as a marker for clinical outcome (i.e., toxicity, efficacy) at the bedside. Besides, constant efforts have been made to develop alternative chemical derivatives or encapsulated forms of gemcitabine, as an attempt to improve its metabolism and pharmacokinetics profile. Overall, gemcitabine is a drug paradigmatic for constant searches of the scientific community to improve its administration through the development of personalized medicine in oncology.

Polymorphisms in SLCO1B3 and NR1I2 as genetic determinants of hematotoxicity of carboplatin and paclitaxel combination

Aim: The goal of our study was to assess the impact of patients’ genetic background on their sensitivity to carboplatin/paclitaxel hematotoxicity. Patients & methods: Parameters describing sensitivity to neutropenia and to thrombocytopenia of 201 patients were extracted from a previous pharmacokinetic/pharmacodynamics analysis, in order to assess their association with 52 candidates SNPs in 18 genes. Results: Carriers of a T allele of SLCO1B3-rs4149117 were 19% less sensitive to thrombocytopenia than the homozygotes for the G allele (p = 0.00279). Carriers of two copies of the ATG haplotypes of NR1I2-rs1523130, rs3814055 and rs1523127 were 19% less sensitive to thrombocytopenia than those harboring other haplotypes (p = 0.025). Conclusion: Our results revealed the importance of SLCO1B3 and NR1I2 in the sensitivity to carboplatin/paclitaxel thrombocytopenia.

Role of cytidine deaminase in toxicity and efficacy of nucleosidic analogs

INTRODUCTION

Nucleosidic analogs such as pyrimidine and purine derivatives are mainstay in the field of treating cancers, both in adults and in children. All these drugs act as antimetabolite compounds, that is, they interfere with the ability of cancer cells to synthesize the nucleosides or the nucleotides necessary for proliferation and progression. As with most cytotoxics, maintaining patients in their therapeutic window is challenging, and predicting changes in drug exposure is critical to ensure an optimal efficacy/toxicity balance.

AREAS COVERED

Among the antimetabolites, a small but widely prescribed number of drugs (i.e., gemcitabine, capecitabine, cytarabine, azacytidine) share a same metabolic pattern driven by a liver enzyme, cytidine deaminase (CDA), coded by a gene displaying several genetic and epigenetic polymorphisms. Consequently, CDA activity is erratic, ranging from deficient to ultra-rapid deaminator patients, with subsequent impact on drug pharmacokinetics and pharmacodynamics eventually. This review provides an update on the variety of clinical studies and case-reports investigating on CDA status as a marker for clinical outcome in cancer patients treated with nucleosidic analogs.

EXPERT OPINION

Whereas sorting patients on the basis of their CDA genotype remains tricky because of unclear genotype-to-phenotype relationships, developing functional strategies (i.e., phenotype-based status determination) could help to use CDA status as a biomarker for developing adaptive dosing strategies with nucleosidic analogs.

The Impact of CDA A79C Gene Polymorphisms on the Response and Hematologic Toxicity in Gemcitabine-Treated Patients: A Meta-Analysis

Purpose

To investigate the impact of the cytidine deaminase (CDA) A79C polymorphism on both the response to gemcitabine in non-small cell lung cancer (NSCLC) patients and the risk of hematologic toxicities in patients bearing any kind of cancer taking gemcitabine.

Methods

The PubMed and Embase databases were searched from the first available article to January 2013. Eligible studies included clinical trials that contained the keywords “gemcitabine” or “cytidine deaminase” and information about response rate of NSCLC patients or hematologic toxicities in patients with any kind of cancer. Relative risk (RR) of different genotypes and 95% confidence intervals (CI) were calculated.

Results

A total of 7 articles (623 patients from 6 studies) were included. The results showed that patients with wild type CDA (AA and AC) had a significantly lower rate of severe anemia than the homozygote mutant type CC (RR=0.308; 95%CI, 0.113-0.021, p=0.021). However, the rate of severe neutropenia, thrombocytopenia, and the response rate were identical between different CDA genotypes.

Conclusion

The A79C CDA polymorphism did not show a significant impact on the response rate to gemcitabine in NSCLC patients, while the wild type CDA genotype was indeed correlated to a lower rate of incidence of severe anemia in patients taking gemcitabine.

CDA gene polymorphisms and enzyme activity: genotype–phenotype relationship in an Italian–Caucasian population

Aim: To assess the distribution of CDA activity from whole blood of 142 healthy subjects, determining its main predictors among genetic (six CDA SNPs) and physiological factors (age and gender). Moreover, we performed a kinetic study of the two CDA protein variants (Q27 and K27) determined by the rs2072671 SNP. Materials & methods: CDA activity was assessed by HPLC. Selected CDA SNPs were genotyped by PCR-based methods. Recombinant CDA protein variants (Q27 and K27) were expressed in an Escherichia coli strain SØ5201 and kinetic assays were performed. Results: The mean value of CDA activity was 0.051 ± 0.024 mU/mg and followed a normal distribution in the study population. Carriers of the CDA*2B (-451T/-92G/-31Del/79C/435C) haplotype displayed higher CDA activity compared with the others. CDA -451G>A, -92A>G and 79A>C (K27Q) SNPs displayed significant associations with CDA activity. The best predictive model of CDA activity included the variables gender and CDA 79A>C (K27Q). Cytidine is the preferential substrate for the variant Q27. Conclusion: We suggest the analysis of both CDA activity and CDA 79A>C (K27Q) SNP in future prospective trials with cytidine analogs, alone or in combination, in order to identify the best marker to secure the administration of these anticancer therapies.

Original submitted 22 October 2012; Revision submitted 11 March 2013

Determination of common genetic variants in cytidine deaminase (CDA) gene in Indian ethnic population

Cytidine deaminase (CDA) is the major enzyme involved in metabolism of gemcitabine, a pyrimidine analog widely used for chemotherapy of solid tumors. While only low amounts of administered gemcitabine undergo intracellular phosphorylation into active forms and involve in antineoplastic activities, majority of it is rapidly inactivated by CDA and excreted to avoid drug toxicity. Knowledge of the genetic polymorphisms mildly effecting cellular activity of the enzyme CDA is therefore crucial to understanding drug-induced toxicities associated with gemcitabine. Functional significance and allele frequencies for common SNPs including 79A>C (*2) and 208G>A (*3) have been reported in various ethnic populations including Caucasian, African, Korean and Japanese. However, such studies have not been reported in any Indian sub-population. In the present study, conventional polymerase chain reaction (PCR) based amplification using gene specific primers and Sanger sequencing were performed to identify CDA variants in 50 healthy individuals from Indian sub-population. Established common variant 79A>C known to reduce CDA activity was observed at a frequency of 0.14 in the study cohort. In addition to other known variants, one novel variant, c.325-209T>C was detected at a frequency of 0.06. Genetic variants in CDA gene and their frequencies established in our study hold value in pharmacogenetics.

Pharmacogenetics of chemotherapy efficacy in breast cancer

Large differences are observed in chemotherapy response between breast cancer patients, with a substantial part of this variability being explained by genetic factors. Polymorphisms in genes encoding drug-metabolizing enzymes, drug transporters and drug targets influence the pharmacokinetics and pharmacodynamics of these anticancer drugs, leading to differences in therapeutic efficacy. Pharmacogenetic investigations of breast cancer therapeutics focused on these candidate loci have been performed. This article summarizes the status of research to identify polymorphisms in genes that influence response to the chemotherapeutic agents used in breast cancer treatment and suggests future directions for this line of research. Understanding the genetic factors that predispose patients to poor treatment outcomes will help guide individualized therapeutic strategies to obtain maximal benefit.

CDA deficiency as a possible culprit for life-threatening toxicities after cytarabine plus 6-mercaptopurine therapy: pharmacogenetic investigations

We describe here the case of a 7-year old girl with lymphoma who developed life-threatening toxicities upon cytarabine plus mercaptopurine. Surprisingly, initial investigations on canonical thiopurine methyltransferase genetic polymorphism proved to be negative. We focused next on deregulations affecting the CDA gene implicated in the liver disposition of cytarabine. This patient was homozygous for both the 79A>C and the -31delC polymorphisms on the CDA gene and promoter, two genotypes with reported opposite effects on CDA phenotype. To determine the CDA status of this patient, additional functional testing was performed and eventually demonstrated that this patient was a poor metabolizer. This case demonstrates that besides affecting thiopurine methyltransferase, dysregulations with CDA should be screened to anticipate toxicities with the cytarabine plus mercaptopurine combination.

A common polymorphism in NR1H2 (LXRbeta) is associated with preeclampsia

Background

Preeclampsia is a frequent complication of pregnancy and a leading cause of perinatal mortality. Both genetic and environmental risk factors have been identified. Lipid metabolism, particularly cholesterol metabolism, is associated with this disease. Liver X receptors alpha (NR1H3, also known as LXRalpha) and beta (NR1H2, also known as LXRbeta) play a key role in lipid metabolism. They belong to the nuclear receptor superfamily and are activated by cholesterol derivatives. They have been implicated in preeclampsia because they modulate trophoblast invasion and regulate the expression of the endoglin (CD105) gene, a marker of preeclampsia. The aim of this study was to investigate associations between the NR1H3 and NR1H2 genes and preeclampsia.

Methods

We assessed associations between single nucleotide polymorphisms of NR1H3 (rs2279238 and rs7120118) and NR1H2 (rs35463555 and rs2695121) and the disease in 155 individuals with preeclampsia and 305 controls. Genotypes were determined by high-resolution melting analysis. We then used a logistic regression model to analyze the different alleles and genotypes for those polymorphisms as a function of case/control status.

Results

We found no association between NR1H3 SNPs and the disease, but the NR1H2 polymorphism rs2695121 was found to be strongly associated with preeclampsia (genotype C/C: adjusted odds ratio, 2.05; 95% CI, 1.04-4.05; p = 0.039 and genotype T/C: adjusted odds ratio, 1.85; 95% CI, 1.01-3.42; p = 0.049).

Conclusions

This study provides the first evidence of an association between the NR1H2 gene and preeclampsia, adding to our understanding of the links between cholesterol metabolism and this disease.

Rapid allele-specific PCR method for CDA 79A>C (K27Q) genotyping: a useful pharmacogenetic tool and world-wide polymorphism distribution

BACKGROUND

The CDA 79A>C (K27Q, rs2072671) functional SNP has recently shown a crucial role in the pharmacogenetics of cytidine-based anticancer drugs widely administered to different subsets of patients. Current gold standard in screening for the CDA rs2072671 is the sequence-based genotyping method. Here we developed a novel, rapid Allele-Specific PCR method for CDA rs2072671 genotyping.

METHODS

DNA was extracted from 324 healthy individuals from two different populations (Italian and Han Chinese). CDA rs2072671 genotyping was performed by Allele-Specific PCR. Sequencing was performed to validate the test results. Results obtained from population screening were compared to that already available in HapMap and in the literature.

RESULTS

Samples analyzed were successfully genotyped and the results were confirmed by sequencing. Genotype distribution does not differ significantly from that previously reported for each relative ethnic group. Also, the world-wide distribution of the CDA rs2072671 SNP is reported. A striking difference is present among the main ethnicities (p=1.715×10(-77)), with CDA*27Q allele showing the lowest frequency in African group (9.7%) and the highest in Caucasians (35.9%).

CONCLUSION

This Allele-Specific PCR method is a useful tool in pharmacogenetics research and a valid and reliable alternative for CDA rs2072671 screening where sequencing or Real-Time PCR is not available.

Integrating pharmacogenetics into gemcitabine dosing--time for a change?

Increasing the efficacy of anticancer agents and avoiding toxic effects is a critical issue in clinical oncology. Identifying biomarkers that predict clinical outcome would ensure improved patient care. Gemcitabine is widely used to treat various solid tumors as a single agent or in combination with other drugs. The therapeutic index of gemcitabine is narrow, and abnormal pharmacokinetics leading to changes in plasma exposure is a major cause of adverse effects. A number of biomarkers have been proposed to predict efficacy of gemcitabine, focusing on molecular determinants of response identified at the tumor level. Genetic and functional deregulations that affect the disposition of a drug could be the reason for life-threatening adverse effects or treatment failure. In particular, deregulation of cytidine deaminase, the enzyme responsible for detoxification of most nucleotide analogs, should be examined. Identifying and validating biomarkers for pharmacogenetic testing before administration of gemcitabine is a step towards personalized medicine.