Pharmacogenetics of anticancer monoclonal antibodies.

Pharmacogenetics is the study of therapeutic and adverse responses to drugs based on an individual's genetic background. Monoclonal antibodies (mAbs) are a rapidly evolving field in cancer therapy, however a number of newly developed and highly effective mAbs (e.g., anti-CTLA-4 and anti-PD-1) possess pharmacogenomic profiles that remain largely undefined. Since the first chemotherapeutic mAb Rituximab was approved in 1997 by the US Food and Drug Administration for cancer treatment, a broad number of other mAbs have been successfully developed and implemented into oncological practice. Nowadays, mAbs are considered as one of the most promising new approaches for cancer treatment. The efficacy of mAb treatment can however be significantly affected by genetic background, where genes responsible for antibody presentation and metabolism, for example, can seriously affect patient outcome. This review will focus on current anticancer mAb treatments, patient genetics that shape their efficacy, and the molecular pathways that bridge the two.

ABCB1 and ABCC1 single-nucleotide polymorphisms in patients treated with clozapine.

Clozapine (CZ) has superior efficacy to other antipsychotic agents in the treatment of schizophrenia and has been extensively used in clinical practice. ATP-binding cassette (ABC) transporter proteins are responsible for the distribution of various molecules as well as drugs across extracellular and intracellular membranes, including the blood-brain barrier. Genetic variations in these proteins can account for differences in treatment response. We investigated the influence of ABCB1 rs1045642 and ABCC1 rs212090 single-nucleotide polymorphisms (SNPs) on CZ serum level, clinical outcome, and changes in body mass index (BMI) in the first year of CZ treatment. These polymorphisms influenced baseline BMI in males (p=0.009 and 0.054, B1 and C1, respectively), changes in BMI in males after 3 (p=0.026, ABCB1) and 12 months (p=0.022, ABCC1) of CZ treatment, and level of diastolic pressure (p=0.002 and 0.051, respectively). The combination of ABCB1 + ABCC1 homozygote SNPs was associated with increased CZ and norclozapine serum levels (p=0.054 and 0.010, respectively). ABC transporter SNPs could be potential biomarkers for CZ-induced weight gain and cardiovascular complications. Further pharmacogenetic research is warranted to help clinicians with their treatment decision, including concomitant use of drugs and prevention of side effects.

CYP2C19*17 protects against metabolic complications of clozapine treatment.

OBJECTIVES: Clozapine (CZ) is the most effective drug for managing treatment-resistant schizophrenic disorders. Its use has been limited due to adverse effects, which include weight gain and new-onset diabetes, but the incidence of these varies between patients. METHODS: We investigated 187 Clozapine Clinic patients (of whom 137 consented for genotyping) for the presence of CYP2C19*17 and its association with CZ and norclozapine (NCZ) levels, and clinical outcomes. RESULTS: Thirty-nine percent of genotyped patients were carriers of the CYP2C 19*17 polymorphism. This group demonstrated significantly higher NCZ serum levels, and significantly lower fasting glucose (5.66 ± 1.19 vs 6.72 ± 3.01 mmol/l, P = 0.009) and Hb1Ac (35.36 ± 4.78 vs 49.40 ± 20.60 mmol/mol, P = 0.006) levels compared to non-carriers of this polymorphism. CZ-treated patients with CYP2C19*17/*17 had a significantly lower prevalence of diabetes as well as a higher likelihood of clinical improvement of their schizophrenia, compared to those without this polymorphism (P = 0.012 and P = 0.031, respectively). CONCLUSIONS: Our data suggest that CYP2C19*17 ultra-rapid-metaboliser status is a protective factor against the development of diabetes during clozapine treatment, and increases the likelihood of improvement in schizophrenia. The role of NCZ in treatment response and side effects, including metabolic syndrome, warrants further pharmacogenetic, pharmacokinetic and pharmacodynamic studies.

Ultrarapid clozapine metabolism and CYP2D6 gene duplication in a patient with schizophrenia.

An optimal clozapine serum level is required for both optimization of clinical response and minimization of troublesome or some of the life-threatening side effects. Serum levels can be influenced by comedication that can cause phenoconversion. When norclozapine/clozapine serum levels and ratios are consistently and significantly lower/higher than expected and there are no concomitant drugs that could account for these findings, further investigation of the genetic variants of CYP1A2, 2D6 and 3A4 are warranted.

Higher than expected clozapine serum level and clozapine/norclozapine ratio due to CYP450 gene polymorphisms.

AIMS: We investigated a case of the unexpectedly high clozapine/norclozapine serum levels in a non-smoker, female patient. METHOD: The RFLP genotype method was used for the loss-of-function CYP450 gene polymorphisms detection. RESULTS: The genotype revealed the presence of CYP2D6*41/*41, rs28371725, NM_000106.5:c.985+39G>A and CYP1A2*1/*1D rs35694136, NM_000761.4:c.-1635delT. CONCLUSION: An appropriate clozapine serum level is required for both optimization of clinical response and avoidance of troublesome, or even life-threatening side effects. Although not the only factor, genetic polymorphisms responsible for the metabolism of clozapine play an important role towards such goals. Pharmacogenetic tests can guide dose adjustment in order to obtain an optimum serum level, which can lead to a better therapeutic response and minimization of harmful side effects.

Cases of adverse reaction to psychotropic drugs and possible association with pharmacogenetics.

Thousands of samples for pharmacogenetic tests have been analysed in our laboratory since its establishment. In this article we describe some of the most interesting cases of CYP poor metabolisers associated with adverse reactions to psychotropic drugs. Prevention of disease/illness, including Adverse Drug Reaction (ADR), is an aim of modern medicine. Scientific data supports the fact that evaluation of drug toxicology includes several factors, one of which is genetic variations in pharmacodynamics and pharmacokinetics of drug pathways. These variations are only a part of toxicity evaluation, however, even if it would help to prevent only a small percentage of patients from suffering adverse drug reactions, especially life threatening ADRs, pharmacogenetic testing should play a significant role in any modern psychopharmacologic practice. Medical practitioners should also consider the use of other medications or alternative dosing strategies for drugs in patients identified as altered metabolisers. This will promise not only better and safer treatments for patients, but also potentially lowering overall healthcare costs.

CYP2D6 genotyping by liquid chromatography-electrospray ionization mass spectrometry.

Genetic polymorphisms can significantly affect the enzyme activity of the drug metabolizing enzyme Cytochrome P450 2D6 (CYP2D6; OMIM 124030). Accordingly, CYP2D6 genotyping is considered as a valid approach to predict the individual CYP2D6 metabolizing status. We introduce ion-pair reversed-phase high-performance liquid chromatography-electrospray ionization mass spectrometry (ICEMS) as method for the characterization of single base variants, small deletions, and insertions in the CYP2D6 gene. A two-step polymerase chain reaction (PCR) was developed for the simultaneous amplification of nine polymorphic regions within the CYP2D6 gene. Cleanup, separation, and denaturation of PCR amplicons were achieved by high-performance liquid chromatography. High-performance molecular mass measurements provided nucleotide composition profiles that principally enable the resolution of 37 reported CYP2D6 alleles. The developed assay was applied to the genotyping of 93 unrelated Austrian individuals. For validation, a selected number of samples and polymorphic sites were retyped by alternative genotyping technologies. The PCR-ICEMS assay turned out to be an accurate, robust, and cost-effective CYP2D6 genotyping strategy.

Pharmacogenetics and gender association with psychotic episodes on nortriptyline lower doses: patient cases.

The variation in individual responses to psychotropic drug treatment remains a critical problem in the management of psychotic disorders. Although most patients will experience remission, some patients may develop drug-induced adverse effects that may range from troublesome to life threatening. Antidepressants are freely prescribed by general practitioners, and there should be constant awareness in the medical community about possible serious side effects. We describe two cases of adverse drug reactions on low dosage treatment that led to extreme psychotic episodes as examples of the potential for dangerous side effects. The patients developed adverse reactions on the normal recommended dosage of nortriptyline, a tricyclics antidepressant (TCA). Both were females, with no history of antidepressant treatment, unsocial behaviour, nor any family history of psychosis, but both experienced severe psychiatric symptoms. Pharmacogenetic tests can easily be performed and interpreted according to the likelihood of adverse reactions and should be included in toxicity interpretation.

Warfarin toxicity and individual variability-clinical case.

Warfarin is a widely used anticoagulant in the treatment and prevention of thrombosis, in the treatment for chronic atrial fibrillation, mechanical valves, pulmonary embolism, and dilated cardiomyopathy. It is tasteless and colorless, was used as a poison, and is still marketed as a pesticide against rats and mice. Several long-acting warfarin derivatives-superwarfarin anticoagulants-such as brodifacoum, diphenadione, chlorophacinone, bromadiolone, are used as pesticides and can produce profound and prolonged anticoagulation. Several factors increase the risk of warfarin toxicity. However, polymorphisms in cytochrome P450 genes and drug interactions account for most of the risk for toxicity complications. Each person is unique in their degree of susceptibility to toxic agents. The toxicity interpretation and the health risk of most toxic substances are a subject of uncertainty. Genetically determined low metabolic capacity in an individual can dramatically alter the toxin and metabolite levels from those normally expected, which is crucial for drugs with a narrow therapeutic index, like warfarin. Personalized approaches in interpretation have the potential to remove some of the scientific uncertainties in toxicity cases.

Cytochrome P450 loss-of-function polymorphism genotyping on the Agilent Bioanalyzer and clinical application.

Responses to toxins and drugs, even to standard medical drug treatment regimens, can vary significantly between individuals. Similar dosages can have divergent results due to polymorphisms in the genes that code for the enzymes responsible for the metabolism of drugs. The focus of this report is to describe our exploration of the personalized medicine approach for patient care at Sydney West Area Health Service. We would like to demonstrate the importance of this approach as it is the subject of debate in the medical and scientific community. The critical points in this debate are the cost of testing, laboratory space required and clinical application. We have shown that a simple approach and instruments like the Agilent Bioanalyzer could be cost effective for laboratory operation. The Agilent Bioanalyzer (Agilent Technologies, CA, USA) can be used for proteins, DNA and cell studies. Hence, reduced cost of instruments, laboratory space requirements, maintenance and operational costs are great advantages of this technology, especially for development and research laboratories.

High-performance liquid chromatographic determination of arecoline in human saliva.

Arecoline (methyl-1,2,5,6-tetrahydro-1-methyl nicotinate) is an alkaloid found in the areca catechu nut which is a major component of the 'betel quid' chewed by a large proporation of the population in India, South Asia and the South Pacific islands. It is commonly associated with the development of oral leukoplakia, oral submucous fibrosis and oral cancer. We have developed a new ion-pairing reversed-phase high-performance liquid chromatographic (HPLC) method for the determination of arecoline in saliva, using arecaidine (1,2,5,6-tetrahydro-1-methylnicotinic acid) as an internal standard. The optimal wavelength was established using UV absorbance scans. It was showed that 215 nm is the optimal wavelength to maximise the signal in detecting arecoline in the mobile phase. Arecoline was extracted from saliva with hexane-isoamyl alcohol (1%) and reconstituted with mobile phase for HPLC analysis. The developed method is an easy and reliable method of determining arecoline concentrations in saliva. Sensitivity, specificity, precision, accuracy and reproducibility of the method were demonstrated to be satisfactory for measuring the arecoline level.