Clinical applications of CYP genotyping in psychiatry

Genetic testing for CYP2D6 and CYP2C19 suggests improved outcome for antidepressant and antipsychotic medication

Individuals carrying genetic variants that result in non-extensive CYP2D6 and CYP2C19 enzyme activity seem to be more prone to non-response and side-effects of psychotropic medications. Therefore, tailoring prescriptions using genetic information may improve patient outcomes. This study examined treatment outcome in psychiatric care after CYP2D6 and CYP2C19 genetic information was provided to patients and physicians. CYP2D6 and CYP2C19 genotyping, assessment of side effects and medical histories were obtained from 80 subjects who were prescribed either antidepressant or antipsychotic medications. Our measure of outcome was mainly physicians' opinions however UKU side effects scores were also used. For CYP2D6, we calculated an activity score based on genotype and psychiatric medications. Correlation analysis was performed for CYP2D6 activity scores and UKU scores. Overall, we received supportive responses from physicians who enrolled patients in our study. Notably, while almost every fourth physician reported improvement in patient outcome, not a single physician indicated that their patient's symptoms worsened after they had used a pharmacogenetic report to guide treatment. We did not observe statistically significant differences in side effects. Overall, our results suggest improved patient outcome following pharmacogenetic testing; nonetheless, more research is required to assess the exact benefit of pharmacogenetics in clinical practice.

Personalizing dosing of risperidone, paliperidone and clozapine using therapeutic drug monitoring and pharmacogenetics

By combining knowledge of pharmacogenetics, therapeutic drug monitoring (TDM) and drug-drug interactions (DDIs) the author developed a model for personalizing antipsychotic dosing, which is applied to risperidone, 9-hydroxyrisperidone or paliperidone, and clozapine. Drugs are approved using an average dose for an ideal average patient, but pharmacologists have described outliers: genetic poor metabolizers (PMs) and ultrarapid metabolizers (UMs). Environmental and personal variables can also make patients behave as PMs or UMs. Drug clearance is represented by the concentration-to-dose (C/D) ratio under steady-state and trough conditions. A very low C/D ratio indicates a UM, while a very high C/D ratio indicates a PM. Total risperidone C/D ratio for the oral formulation is around 7 ng/ml per mg/day and can be influenced by CYP2D6 polymorphism, DDIs with inducers and inhibitors, and renal function. Oral paliperidone has low availability; its C/D ratio is around 4.1 ng/ml per mg/d and can be influenced by inducers and renal impairment. Once-a-month long-acting paliperidone provides a C/D ratio around 7.7 ng/ml per mg/day at steady state, which is expected to be in the 8th month (before the 9th injection). TDM is particularly important for long-acting paliperidone formulations that may accumulate once steady state is reached (after years for the 3- and 6-month formulations). In the US, clozapine C/D ratios typically range from 0.6 (male smokers) to 1.2 (female non-smokers) ng/ml per mg/day. East Asians' clozapine C/D ratios appear to be twice as high. Inhibitors (including fluvoxamine and oral contraceptives) and inflammation can also increase clozapine C/D ratios. This article is part of the issue entitled 'Special Issue on Antipsychotics'.

Drug-Drug Interactions in Prostate Cancer Treatment

Polypharmacy is associated with an increased risk of drug-drug interactions (DDIs), which can cause serious and debilitating drug-induced adverse events. With a steadily aging population and associated increasing multimorbidity and polypharmacy, the potential for DDIs becomes considerably important. Prostate cancer (PCa) is the most common cancer in men and occurs mostly in elderly men in the Western world. Therefore, the aim of this review is to give an overview of DDIs in PCa therapy to better understand pharmacodynamic and pharm kinetic side effects as well as their interactions with other medications. Last, we explore potential future strategies, which might help to optimize treatment and reduce adverse events patients with polypharmacy and PCa.

Clozapine Metabolism in East Asians and Caucasians: A Pilot Exploration of the Prevalence of Poor Metabolizers and a Systematic Review

PURPOSE/BACKGROUND

In clozapine therapeutic drug monitoring (TDM) studies, Chinese reached the same concentrations using half the dosage Caucasians use. Defining clozapine poor metabolizers (PMs) requires stratification by ethnicity, smoking, and sex.

METHODS/PROCEDURES

After sex and smoking stratification in 129 Chinese inpatients (mean, 8.8 TDM samples per patient), we explored the association between the total concentration-dose (C/D) ratio and CYP1A2 (*1C, *1F, and *7) and CYP2C19 alleles (*2 and *3). A systematic literature review identified 22 clozapine TDM prior studies (13 in Caucasians and 7 in East Asians).

FINDINGS/RESULTS

In our Chinese sample, the mean total clozapine C/D ratio (ng/mL per mg/d) was 1.96 for 22 male smokers, 2.07 for 5 female smokers, 2.47 for 36 male nonsmokers, and 2.95 for 66 female nonsmokers. CYP1A2 *1C had no significant effects, and CYP1A2 *1F had small effects. Five clozapine PMs (4%) needed low clozapine doses of 75 to 115 mg/d to get therapeutic concentrations. Using the same methodology in a published Italian sample, we found 5 PMs (3.3% of 152). In the systematic review, the clozapine C/D ratio (ng/mL per mg/d) was higher when comparing: (1) weighted mean values of 1.57 in 876 East Asians versus 1.07 in 1147 Caucasians and (2) ranks of 8 East Asians versus 13 Caucasian samples (P < 0.001).

IMPLICATIONS/CONCLUSIONS

Future TDM studies need to further explore the frequency of clozapine PMs after sex and smoking stratification in East Asian and Caucasian patients. Compared with Caucasians, East Asians appear to have a clinically relevant decrease in clozapine clearance.

Schizophrenia: recent advances in LC-MS/MS methods to determine antipsychotic drugs in biological samples

Schizophrenia is one of the most debilitating and costly illnesses worldwide. First-generation antipsychotics such as chlorpromazine and haloperidol succeeded in controlling the positive symptoms of schizophrenia, but had significant extrapyramidal effects that led to the search for new agents and the release of second-generation (or atypical) antipsychotics. These drugs had a lower risk of adverse motor symptoms. Therapeutic drug monitoring has become a useful tool to optimize schizophrenia treatment and HPLC-MS/MS has been considered the primary technique to monitor antipsychotics. This review comprises three sections: schizophrenia pathophysiology and treatment; recent advances in LC-MS/MS methods designed to measure levels of antipsychotics and their metabolites in plasma samples (selectivity, matrix effect and sensitivity); and the importance of therapeutic drug monitoring.

The Impact of Pharmacogenomics in Personalized Medicine

Recent advances in Pharmacogenomics have made it possible to understand the reasons behind the different response of a drug. Discovery of genetic variants and its association with the varying response of drug provide the basis for recommending a drug and its dose to an individual patient. Genetic makeup-based prescription, design, and implementation of therapy not only improve the outcome of treatments but also reduce the risk of toxicity and other adverse effects. A better understanding of individual variations and their effect on drug response, metabolism excretion, and toxicity will replace the trial-and-error approach of treatment. Evidence of the clinical utility of pharmacogenetics testing is only available for a few medications, and FDA labels only require pharmacogenetics testing for a small number of drugs. Although there is a great promise, there are not many examples where Pharmacogenomics impacts clinical utility. Some genetic variants related to different diseases have been reported, and many have not been studied yet. The information related to the outcome of treatment with a particular drug and a genetic variant can be used to release a warning/label for the use of that drug. There are many limitations in the way of implementing the goal of personalized medicine. Future advances in the field of genomics, diagnosis approaches, data analysis, clinical decision-making, and sustainable business model for personalization of therapy can speed up the individualization of therapy based on genetic makeup.

Association of CYP2D6 polymorphisms and extrapyramidal symptoms in schizophrenia patients receiving risperidone: a retrospective study

Background

Risperidone is mainly metabolized by cytochrome P450 (CYP) 2D6 in the liver. The gene encoding CYP2D6 is highly polymorphic. The average steady-state plasma concentration of risperidone active moiety is higher in the CYP2D6 intermediate metabolizers (IMs) compared with that in the extensive metabolizers (EMs). An association between drug-induced extrapyramidal symptoms scale (DIEPSS) score and CYP2D6 polymorphisms has not been reported to date. This study investigates the association of CYP2D6 polymorphisms with the severity of extrapyramidal symptoms in schizophrenia patients receiving risperidone therapy.

Methods

Schizophrenia patients undergoing risperidone treatment were recruited for the study in the Kobe University Hospital. We evaluated extrapyramidal symptoms of schizophrenia using the DIEPSS. CYP2D6*10 and CYP2D6*14 were analyzed using TaqMan® assays, and CYP2D6*5 was analyzed using the long-PCR method. Patients with CYP2D6*1/*5, *1/*14, *5/*10, *10/*10, and *10/*14 were classified as IMs, and patients with CYP2D6*1/*1 and *1/*10 were classified as EMs. Patients with CYP2D6*5/*5, *5/*14, and *14/*14 were classified as poor metabolizers (PMs).

Results

A total of 22 patients were included in the study. No patients were classified as PMs. The dose of risperidone (mg/day) was not significantly different between EMs (n = 15) and IMs (n = 7) (median with the interquartile range: 4.0 (2.0-6.0) vs. 4.0 (2.0-7.0) mg, p = 0.31). The age and disease duration of schizophrenia were not significantly different between the EMs and IMs. The DIEPSS score in the IMs was significantly higher than that in the EMs (median with the interquartile range: 5.0 (3.5-6.5) vs. 0.0 (0.0-3.0), p < 0.001). The multiple regression analysis showed that CYP2D6 IMs is a significant risk factor for the DIEPSS (p < 0.05).

Conclusion

Special attentions should be paid to the onset of extrapyramidal symptoms in schizophrenia patients identified as CYP2D6 IM undergoing risperidone therapy.

The Effect of Body Weight Changes on Total Plasma Clozapine Concentrations Determined by Applying a Statistical Model to the Data From a Double-Blind Trial

PURPOSE/BACKGROUND

Some therapeutic drug monitoring studies suggest that increased weight is associated with small increases in clozapine concentrations. The goal of this study was to reanalyze a US double-blind study using a sophisticated statistical model to test whether weight gains from baseline or increases in percentage of body fat from baseline, computed from a published equation, are associated with increased total plasma clozapine concentrations after controlling for the effects of smoking and sex.

METHODS/PROCEDURES

Using data from a multidosage randomized double-blind US clozapine trial previously published, a random intercept linear model of steady-state total plasma clozapine concentrations was fitted to 424 concentrations from 47 patients.

FINDINGS/RESULTS

After adjusting for sex and smoking, (1) a 1-kg gain in body weight during clozapine treatment was significantly associated with a 1.4% increase in total plasma clozapine concentrations (95% confidence interval = 0.55 to 2.3) and (2) a 1-point increase in percentage of body fat during clozapine treatment was significantly associated with a 5.4% increase in total clozapine concentration (2.5 to 8.3) in females and 1.4% (-1.1 to 4.0) in males.

IMPLICATIONS/CONCLUSIONS

As hypothesized, weight increases during clozapine treatment, which probably reflect increases in fat tissue, were associated with increases in total plasma concentrations. Pending further replication in other samples, it seems likely that clozapine may deposit in body fat and that this may decrease clozapine clearance. This change may be small in most patients but may be clinically relevant in females with major gains in body fat.

High Doses of Drugs Extensively Metabolized by CYP3A4 Were Needed to Reach Therapeutic Concentrations in Two Patients Taking Inducers

INTRODUCTION

In the last 20 years of clinical practice, the senior author has identified these 2 rare cases in which the patients needed extremely high doses of drugs metabolized by CYP3A4 to reach and maintain serum therapeutic concentrations.

METHODS

The high metabolic ability of these 2 patients was demonstrated by the low concentration-to-dose ratios (C/D ratios) of several drugs metabolized by CYP3A4.

RESULTS

Case 1 was characterized by a history of high carbamazepine doses (up to 2,000mg/day) and needed 170 mg/day of diazepam in 2 days to cooperate with dental cleaning. The high activity of the CYP3A4 isoenzyme was manifested by fast metabolism for quetiapine and diazepam, which took more than 1 year to normalize after the inducer, phenytoin, was stopped. Case 2 was also very sensitive to CYP3A4 inducers as indicated by very low C/D ratios for carbamazepine, risperidone and paliperidone. The carbamazepine (2,800 mg/day) and risperidone (20 mg/day) dosages for this second patient are the highest doses ever seen for these drugs by the senior author. Risperidone induction appeared to last for many months and metabolism was definitively normal 3 years after stopping carbamazepine. On the other hand, olanzapine C/D ratios were normal for induction.

CONCLUSIONS

The literature has never described similar cases of very high doses of drugs metabolized by CYP3A4. We speculate that these 2 patients may have unusual genetic profiles at the nuclear receptor levels; these receptors regulate induction of drugs.

CYP2D6 genotypes in revolving door patients with bipolar disorders: A case series

RATIONALE

In psychiatric disorders, interindividual differences in cytochrome P450 (CYP)2D6 (CYP2D6) enzymatic activity could be responsible of adverse drug reactions (ADRs) and therapeutic failures (TFs) for CYP2D6-metabolized drugs, contributing to the periodical hospital readmissions of the revolving door (RD) condition.

PATIENT CONCERNS

We investigated CYP2D6 genotypes in a controlled series of 5 consecutive RD patients with Bipolar Disorder (BD).

DIAGNOSES

Psychiatric patients affected by Bipolar Disorder.

INTERVENTIONS

We defined TFs as a difference at the Brief Psychiatric Rating Scale score ΔBPRS < 25% at each 1-week of stable treatment, and ADRs as the onset of extrapyramidal symptoms and/or metabolic impairment with weight gain.

OUTCOMES

At 3 months, a mean number of 2.75 ± 1.26 ADR and a mean ΔBPRS score of 16.07 ± 0.05% were observed. At 6 months of follow-up, compared to the only patient without BD (ΔBPRS < 32.10%), BD patients (n = 4) showed TFs (ΔBPRS < 25%). CYP2D6 genotyping revealed intermediate metabolizer phenotypes for BD patients and an extensive metabolizer phenotype for the patient without BD. In BD patients, the ratio of drugs maintained/discontinued for TFs or ADRs was 1.75 for non-CYP2D6 versus 0.33 for CYP2D6 interacting drugs, while the proportion of ADR:TF was 0:4 versus 6:3.

LESSONS

Our findings may suggest that CYP2D6 clinically relevant genotypes may be involved in the unwanted outcomes observed in RD patients with BD.

A Prospective Study to Evaluate the Effect of CYP2D6 Polymorphism on Plasma level of Risperidone and its Metabolite in North Indian Patients with Schizophrenia

BACKGROUND

Risperidone is one of commonly utilized antipsychotic in clinical practice. Various metabolizing enzymes effect the plasma levels of risperidone and its active metabolite and thus its clinical efficacy. So, we attempted to evaluate the relationship between CYP2D6*10 (rs1065852) and CYP2D6*4 (rs3892097) gene polymorphism and the plasma concentration of risperidone and its metabolite in patients with schizophrenia.

METHODOLOGY

It was a 12-week prospective study carried out in patients diagnosed with schizophrenia. The dose of risperidone was increased weekly by 1 mg and rating of psychopathology was done using Positive and Negative Syndrome Scale (PANSS). Quantification of plasma level of risperidone and 9-hydroxyrisperidone was carried out at week 6 and 12 of treatment. The *4 and *10 alleles of CYP2D6 were genotyped and their effect on metabolism of risperidone was assessed.

RESULTS

The number of CYP2D6*4 alleles affected the plasma levels of risperidone, 9-hydroxyrisperidone at 6 weeks of treatment but not at 12 weeks. On the other hand, the number of mutated alleles for CYP2D6*10 influenced the dose corrected plasma concentration of risperidone and active moiety at 12 weeks of treatment. The ratio of plasma concentration of risperidone and 9-hydroxyrisperidone was more than one in all study participants, thus, suggesting that they were poor metabolizers of risperidone.

CONCLUSION

The polymorphism of CYP2D6*10 affects the steady state plasma concentration of risperidone in Indian patients with schizophrenia.

Two cases of high serum clozapine concentrations occurring during inflammation in Chinese patients

Objective Serious infections or inflammations have been associated with serum clozapine concentration increases and sometimes with clozapine toxicity. Method These two cases describe Chinese patients (Case 1: a 57-year-old female nonsmoker with severe dermatitis and Case 2: a 47-year-old male nonsmoker with influenza and secondary infection). Results In both cases, the Drug Interaction Probability Scale established the presence of a probable drug-drug interaction. In both cases, the clozapine and the total clozapine concentration-to-dose ratios followed a temporal pattern (normal-high-normal), consistent with an inhibition of clozapine metabolism during peak inflammation. In the first case, the total clozapine concentration-to-dose ratio (8 with no/low inflammation: median of 3.10 and 2 at peak inflammation: median of 3.90) provided a significant difference (P = 0.044). In the second patient, because of the smaller sample size and reduced statistical power (4 with no infection: a median of 1.59 and 2 at peak infection: 3.46), the increase did not reach significance (P = 0.13). In the first case, the median baseline clozapine concentration-to-dose ratio increased by a factor of 1.45 from 2.00 to a peak of 2.89. To compensate for the inhibition of clozapine metabolism, the dose correction factor was 0.69 (1/1.45) or a decrease in dose of approximately one-third. In the second case, the median baseline clozapine concentration-to-dose ratio increased by a factor of 2.56 from 1.15 to a peak of 2.94. Conclusion This provided a dose correction factor of 0.40 (1/2.56) or approximately half the dose, similar to published cases in Caucasians with serious respiratory infections.

Pharmacoresistant Severe Mental Health Disorders in Children and Adolescents: Functional Abnormalities of Cytochrome P450 2D6

BACKGROUND

Severe mental health disorders in children and adolescents represent a major public health problem. Despite adequate drug treatment, some patients develop pharmacoresistant disease. As a consequence, physicians are confronted with prescribing challenges, prolonged hospitalization and increased risk of adverse events, thus aggravating short-, medium-, and long-term prognosis. The majority of psychotropic treatments, particularly antipsychotics and antidepressants, are metabolized at hepatic level by cytochrome P450 (CYP), particularly by CYP3A4 and CYP2D6. Several CYP2D6 genetic polymorphisms are described to be associated with ultrarapid (UM) or poor drug metabolism (PM), inducing clinical resistance and/or adverse events, and might therefore be related to pharmacoresistant severe mental health disease.

CASE PRESENTATION

A total of nine pharmacoresistant patients (four females, five males) aged 11-16 (mean 14.1) years have been genotyped for CYP2D6 between January, 2015 and April, 2016. Patients were diagnosed with schizophrenia (n = 5), autism spectrum disorders (n = 2), intellectual disability with challenging behavior (n = 2), oppositional defiant disorder (n = 1), and post-traumatic stress and borderline personality disorders (n = 1). They had a treatment history with on average 6.1 (3-9) psychotropic, 5 (3-7) antipsychotic, and 3.4 (2-5) CYP2D6-metabolized antipsychotic and antidepressant molecules. Five patients (56%) presented functional anomalies of the CYP2D6 gene: three patients were UM metabolizers with gene duplication and two patients were PM with *4/*41 and *3/*4 polymorphisms.

CONCLUSION

Functional anomalies of CYP2D6 concerned more than half of our pediatric inpatient sample with pharmacoresistant disease. However, our case reports are limited by the low sample size. Nevertheless, knowledge of individual metabolism and in particular CYP2D6 genotyping should be considered for clinical workup and therapy adjustment in resistant patients in child and adolescent psychiatry and might permit better treatment outcome, increased treatment adherence and diminished adverse events.

ABCB1 and CYP2D6 polymorphisms and treatment response of psychotic patients in a naturalistic setting

OBJECTIVES

The aim of our study was to examine the association between ABCB1 polymorphisms G2677T/A (rs2032582) and C3435T (rs1045642) and common CYP2D6 variants, with the response to antipsychotic treatment of psychotic patients, in a naturalistic setting, in Greece.

METHODS

One hundred patients suffering from schizophrenia and other psychotic disorders were included in the study. Dosages were normalized to chlorpromazine equivalents. Response following 1 month of treatment was assessed as either a continuous variable, using the distribution of the corrected Positive and Negative Syndrome Scale percent change, or as a dichotomous variable defined as the number of patients scoring ≥30% from the corrected baseline Positive and Negative Syndrome Scale score. Genotyping was achieved with established polymerase chain reaction-restriction fragment length polymorphism methods.

RESULTS

With response treated as a continuous variable, the homozygous recessive rs2032582 genotypes (TT) who were simultaneously carriers of a loss-of-function CYP2D6 allele (*4 or *5) responded significantly worse than the rest of the patients. Comparison of genotype frequencies revealed a statistically significant association of the above combination. No significant association between chlorpromazine equivalents and the tested genotypes was detected.

CONCLUSION

We have detected a possible interaction between ABCB1 and CYP2D6 in affecting response of psychotic patients to drug treatment, in a naturalistic setting.

The Group of Treatment Resistant Schizophrenias. Heterogeneity in Treatment Resistant Schizophrenia (TRS)

Schizophrenia is composed of a heterogeneous group of patient segments. Our current notion of the heterogeneity in schizophrenia is based on patients presenting with diverse disease symptom phenotypes, risk factors, structural and functional neuropathology, and a mixed range of expressed response to treatment. It is important for clinicians to recognize the various clinical presentations of resistance to treatment in schizophrenia and to understand how heterogeneity across treatment resistant patient segments may potentially inform new strategies for the development of effective treatments for Treatment Resistant Schizophrenia (TRS). The heterogeneity of schizophrenia may be reduced by parsing patient segments based on whether patients demonstrate an adequate or inadequate response to treatment. In our current concept of TRS, TRS is defined as non-response to at least two adequate trials of antipsychotic medication and is estimated to affect about 30% of all patients with schizophrenia. In this narrative review, the author discusses that the demonstration of inadequate response to antipsychotic drugs (APDs) may infer that some TRS patients may be suffering from a non-dopamine pathophysiology since D2 receptor antagonist-based treatment is ineffective. Preliminary neurobiological findings may further support the pathophysiologic distinction of TRS from that of general schizophrenia. Investigation of the basis for heterogeneity in TRS through the systematic investigation of relevant "clusters" of similarly at risk individuals may hopefully bring us closer to realize a precision medicine approach for developing effective therapies for TRS patient segments.

Effect of Polymorphisms on the Pharmacokinetics, Pharmacodynamics and Safety of Sertraline in Healthy Volunteers

Sertraline is a selective serotonin reuptake inhibitor widely metabolized in the liver by cytochrome P450 (CYP) enzymes. Besides, it is a P-glycoprotein substrate. Moreover, serotonin transporters and serotonin receptors are involved in its efficacy and safety. The aim of this study was to evaluate the role of polymorphisms of metabolizing enzymes, transporters and receptors on the pharmacokinetics, pharmacodynamics and tolerability of sertraline in healthy volunteers. Forty-six healthy volunteers (24 men and 22 women) receiving a 100-mg single oral dose of sertraline were genotyped for 17 genetic variants of CYP enzymes (CYP2B6, CYP2C9, CYP2C19, CYP2D6), ATP-binding cassette subfamily B member 1 (ABCB1), solute carrier family 6 member 4 (SLC6A4), 5-hydroxytryptamine receptor 2A (HTR2A) and 5-hydroxytryptamine receptor 2C (HTR2C) genes. Pharmacokinetic and pharmacodynamic parameters were similar in men and women. Polymorphisms in CYP2C19 and CYP2B6 genes influenced sertraline pharmacokinetics, with a greater effect of CYP2C19. Individuals carrying defective alleles for CYP2C19 and CYP2B6 showed higher area under the curve (AUC) and half-life (T_1/2 ). Moreover, CYP2C19*17 was related to a decreased AUC and T_1/2 . No significant effect was found for polymorphisms in CYP2C9, CYP2D6 and ABCB1 on sertraline pharmacokinetics. Sertraline had a small heart rate-lowering effect, directly related to maximum concentration (C_max ) and the presence of ABCB1 minor alleles. Sertraline had no significant effect on blood pressure and QTc. There was a tendency to present more adverse drug reactions in women and individuals with higher AUC of sertraline, such as CYP2C19 intermediate metabolizers and CYP2B6 G516T T/T individuals.

Point-of-care companion diagnostic tests for personalizing psychiatric medications: fulfilling an unmet clinical need

Over the last decade stable isotope-labeled substrates have been used as probes for rapid, point-of-care, non-invasive and user-friendly phenotype breath tests to evaluate activity of drug metabolizing enzymes. These diagnostic breath tests can potentially be used as companion diagnostics by physicians to personalize medications, especially psychiatric drugs with narrow therapeutic windows, to monitor the progress of disease severity, medication efficacy and to study in vivo the pharmacokinetics of xenobiotics. Several genotype tests have been approved by the FDA over the last 15 years for both cytochrome P450 2D6 and 2C19 enzymes, however they have not been cleared for use in personalizing medications since they fall woefully short in identifying all non-responders to drugs, especially for the CYP450 enzymes. CYP2D6 and CYP2C19 are among the most extensively studied drug metabolizing enzymes, involved in the metabolism of approximately 30% of FDA-approved drugs in clinical use, associated with large individual differences in medication efficacy or tolerability essentially due to phenoconversion. The development and commercialization via FDA approval of the non-invasive, rapid (<60 min), in vivo, phenotype diagnostic breath tests to evaluate polymorphic CYP2D6 and CYP2C19 enzyme activity by measuring exhaled ¹³CO₂ as a biomarker in breath will effectively resolve the currently unmet clinical need for individualized psychiatric drug therapy. Clinicians could personalize treatment options for patients based on the CYP2D6 and CYP2C19 phenotype by selecting the optimal medication at the right initial and subsequent maintenance dose for the desired clinical outcome (i.e. greatest efficacy and minimal side effects).

Paroxetine versus Venlafaxine and Escitalopram in Korean Patients with Major Depressive Disorder: A Randomized, Rater-blinded, Six-week Study

Objective

The purpose of this study was to compare the efficacy and safety of escitalopram, paroxetine and venlafaxine in Korean patients with major depressive disorder (MDD).

Methods

A total of 449 Korean MDD patients were recruited in a six-week, randomized, rater-blinded, active-controlled trial and were evenly randomized to paroxetine, venlafaxine, or escitalopram treatment.

Results

When comparing the mean difference for the Montgomery-Åsberg Depression Rating Scale (MADRS) and the Hamilton Depression Rating Scale (HDRS) total scores during six weeks, paroxetine (−6.4±0.4, and −5.4±0.4, respectively) was found to be significantly superior to escitalopram (−3.7±0.5 and −3.1±0.4, respectively). Venlafaxine had a significantly lower MADRS total score (−5.4±0.4) than escitalopram. When adjusting baseline variables, the response, according to the MADRS and HDRS scores, in the paroxetine group was greater than that for the escitalopram group (odds ratio [OR]=2.43, 95% confidence interval [CI]=1.42–4.16 for MADRS; and OR=2.32, 95% CI=1.35–3.97 for HDRS) and the venlafaxine group (OR=1.94, 95% CI=1.17–3.21 for MADRS; and OR=1.71, 95% CI=1.03–2.83 for HDRS). Despite that the overall tolerability was high and similar among the three groups, a total of 268 subjects (59.7%) prematurely discontinued treatment, representing the main limitation of the present study.

Conclusion

Although a low study completion rate limits generalizability, our findings suggest that paroxetine might be superior to escitalopram in Korean MDD patients. Further studies should be conducted to draw a definite conclusion.

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.

The predictive value of ABCB1, ABCG2, CYP3A4/5 and CYP2D6 polymorphisms for risperidone and aripiprazole plasma concentrations and the occurrence of adverse drug reactions

We investigated in ninety Caucasian pediatric patients the impact of the main polymorphisms occurring in CYP3A, CYP2D6, ABCB1 and ABCG2 genes on second-generation antipsychotics plasma concentrations, and their association with the occurrence of adverse drug reactions. Patients with the CA/AA ABCG2 genotype had a statistically significant lower risperidone plasma concentration/dose ratio (Ct/ds) (P-value: 0.007) and an higher estimated marginal probability of developing metabolism and nutrition disorders as compared to the ABCG2 c.421 non-CA/AA genotypes (P-value: 0.008). Multivariate analysis revealed that the ABCG2 c.421 CA/AA genotype was found associated to a higher hazard (P-value: 0.004) of developing adverse drug reactions classified as metabolism and nutrition disorders. The ABCB1 2677TT/3435TT genotype had a statistically significant lower aripiprazole Ct/ds if compared with patients with others ABCB1 genotypes (P-value: 0.026). Information obtained on ABCB1 and ABCG2 gene variants may result useful to tailor treatments with these drugs in Caucasian pediatric patients.

Intuitive pharmacogenetic dosing of risperidone according to CYP2D6 phenotype extrapolated from genotype in a cohort of first episode psychosis patients

Risperidone (R) is the most prescribed antipsychotic drug for patients with a first episode of psychosis (FEP). In a naturalistic cohort of chronic psychiatric inpatients, we demonstrated that clinicians adjust R dosage by CYP2D6 activity, despite being blinded to the genotype, which we described as an "intuitive pharmacogenetic" process. The aim of the present study is to replicate our previous findings of intuitive pharmacogenetic in a cohort of FEP patients using CYP2D6 phenotype extrapolated from genotypes. 70 FEP patients, under baseline treatment with R monotherapy were genotyped using the iPLEX® ADME PGx multiplex panel and TaqMan® Genotyping and Copy Number Assays. Plasma concentrations of R and its metabolite, 9-hydroxyrisperidone (9-OH), were determined. The predictive properties of those variables associated with R dosage were tested using a multiple linear regression model as well as regression trees. Significant differences in the mean daily dosage of R among CYP2D6 phenotypes were observed (Kruskal-Wallis test p=0.02): PM (4.00±2.3mg/mL), IM (4.56±2.44), EM (6.22±4.0mg/day) and UM (10.20±4.91mg/day). However, non-significant differences were observed in the R/9-OH ratio or in the Concentration/Dose ratio. Regression tree provided better estimations of R dosage than the multiple linear regression model (MAE=0.958 and R²=0.871). We confirm the "intuitive pharmacogenetic" dosing of R according to the CYP2D6 phenotype in a FEP cohort. The results presented provides a rationale for the clinical use of CYP2D6 genotyping in personalized medicine.

Clozapine-induced myocarditis may be associated with rapid titration: A case report verified with autopsy

Clozapine-induced myocarditis is a poorly understood, rare, potentially fatal adverse drug reaction with absolute risks ranging from 7 to 34 per 1000 in Australia and 0.07-0.6 per 1000 in other countries. Hypersensitivity reactions have been postulated including some cases probably associated with rapid titrations. This case describes a 50-year-old African-American man with schizoaffective disorder, naïve to clozapine, who probably died from clozapine-induced myocarditis. He was started on 25 mg/day of clozapine and received 1625 mg over 14 days, prior to his death on day 15. The autopsy found predominantly lymphocytic infiltrate of the perivascular soft tissue and myocardium of the ventricles, with occasional eosinophils. Using the Liverpool ADR Causality Assessment Tool, it was deemed probable that the patient's death was secondary to myocarditis. The patient had fulminant death with no obvious changes in vital signs. Neither C-reactive protein nor troponin was measured, but it is unlikely that the results would have arrived in time to prevent the patient's death. Age, rapid titration, and concomitant use of valproate contributed to this case, which was probably an idiosyncratic adverse drug reaction associated with rapid titration. Lamotrigine-induced Stevens-Johnson syndrome also appears to be an idiosyncratic adverse drug reaction associated with rapid titration, but its incidence has been remarkably reduced since the recommended starting lamotrigine dose was reduced and corrected by the effect of inhibitors such as valproate. Similarly, clozapine-induced myocarditis incidence probably can be reduced with the use of slow titrations, including even slower titrations for patients with lower ability to metabolize clozapine, such as those taking valproate.

Possible Oxcarbazepine Inductive Effects on Aripiprazole Metabolism: A Case Report

Oxcarbazepine is a cytochrome P450 (CYP) 3A4 inducer, which is structurally similar to carbamazepine. Although lacking Food and Drug Administration approval, oxcarbazepine is sometimes prescribed to treat aggressive behavior in youth with autism spectrum disorder (ASD). These youths may also be taking second-generation antipsychotics, some of which are substrates of the CYP3A4 metabolic pathway. The combination of these medications may result in decreased serum antipsychotic concentrations, potentially reducing effectiveness. A limited number of reports are available which discuss reduced atypical antipsychotic concentrations secondary to oxcarbazepine CYP3A4 induction. We report a young boy taking oxcarbazepine (1200 mg/d) who presented with an unexpectedly low serum aripiprazole concentration. Utilizing therapeutic drug monitoring, pharmacogenetic testing, and a tool to evaluate drug-drug interactions, we estimate that oxcarbazepine possibly reduced his serum aripiprazole concentration by 68%. Our report is important, as it is the first to describe a drug-drug interaction between oxcarbazepine and aripiprazole. This report should encourage the completion of in vitro and clinical studies and the publication of case reports describing the possible inductive effects of oxcarbazepine on atypical antipsychotics (including cariprazine, lurasidone, quetiapine, aripiprazole, brexpiprazole, iloperidone, and risperidone) mediated by induction of the CYP3A4 metabolic pathway.

Should a routine genotyping of CYP2D6 and CYP2C19 genetic polymorphisms be recommended to predict venlafaxine efficacy in depressed patients treated in psychiatric settings?

AIM

The antidepressant venlafaxine (VEN) is metabolized by CYP2D6 and CYP2C19. The aim of this study was to assess the relevance of generalizing to daily practice the genotyping of CYP2D6 and CYP2C19 to predict VEN efficacy in depressed patients treated in psychiatric settings.

PATIENTS & METHODS

This study was nested in a naturalistic cohort, with 206 patients requiring a new antidepressant treatment and genotyped for CYP2D6 *3, *4, *5 del, *6, *2xN, *10, *41 and CYP2C19 *2, *3, *4, *5, *17 alleles.

RESULTS

CYP2D6 and CYP2C19 phenotypes were associated neither with the Hamilton depression rating scale score improvement, nor with response and remission.

CONCLUSION

Routine CYP2D6 and CYP2C19 genotyping cannot be recommended to predict VEN efficacy in depressed patients treated in psychiatry settings.

Pharmacogenetic testing revisited: 5' nuclease real-time polymerase chain reaction test panels for genotyping CYP2D6 and CYP2C19

Due to their involvement in the metabolization of commonly prescribed psychopharmaceutical drugs, the cytochrome oxidase genes CYP2D6 and CYP2C19 are extensive targets for pharmacogenetic testing. The existence of common allelic variants allows the prediction of a metabolic phenotype based on a genotype result, hereby supplying a clinical tool for optimizing prescription and minimizing adverse effects. In this study, we present the development of two 5' nuclease real-time polymerase chain reaction (PCR) test panels, capable of detecting eight of the most clinically relevant alleles of the CYP2D6 gene (*2, *3, *4, *6, *9, *10, 17, *41) and the three most common nonfunctional alleles of CYP2C19 (*2, *3, *4). The assays have been thoroughly validated using a large collection of reference samples, by parallel testing and by DNA sequencing. The reanalysis of reference samples provided the calculation of the frequency of the CYP2D6*4K allele in a population, not previously reported. Furthermore, original test results from CYP2D6*41, generated based on the presence of the 2850T and the lack of the -1584G single-nucleotide polymorphism (SNP), were compared with genotyping based on the current acknowledged founder SNP 2988G of this allele. These results indicate that up to 17.7% of the patients originally tested as carriers of the CYP2D6*41 allele may have had an incorrect phenotypic result assigned. The two 5' nuclease real-time PCR test panels have subsequently been optimized for use in the clinical laboratory, using a standard real-time PCR instrument and software.

The Art of Pharmacotherapy: Reflections on Pharmacophobia

PURPOSE/BACKGROUND

This commentary deals with the neglected issue of the art of psychopharmacology by recounting the authors' journeys.

METHODS/PROCEDURES

First, a model of medical science situated within the history of medicine is described including (1) a limitation of the mathematical model of science, (2) the distinction between mechanistic science and mathematical science, (3) how this distinction is applied to medicine, and (4) how this distinction is applied to explain pharmacology to psychiatrists. Second, the neglected art of psychopharmacology is addressed by explaining (1) where the art of psychopharmacotherapy was hiding in the first author's psychopharmacology research, (2) how the Health Belief Model was applied to the art of medicine, (3) how the second author became interested in the Health Belief Model, and (4) his studies introducing the Health Belief Model in psychopharmacology. The authors' collaboration led to: (1) study of the effect of pharmacophobia on poor adherence and (2) reflection on the limits of the art of psychopharmacology.

FINDINGS/RESULTS

Low adherence was found in 45% (116/258) of psychiatric patients with pharmacophobia versus 22% (149/682) in those with no pharmacophobia, providing an odds ratio of 2.9 (95% confidence interval, 2.2-4.0) and an adjusted odds ratio of 2.5 (95% confidence interval, 1.8-3.5) after adjusting for other variables contributing to poor adherence.

IMPLICATIONS/CONCLUSIONS

Different cognitive patterns in different patients may contribute to poor adherence. Specific interventions targeting these varying cognitive styles may be needed in different patients to improve drug adherence.

In vitro analysis of factors influencing CYP1A2 expression as potential determinants of interindividual variation

Individual differences in drug metabolism contribute to interindividual variation that characterizes responses to drugs and risk in exposure to foreign chemicals. Large individual differences are found in expression levels of CYP1A2, a major drug-metabolizing enzyme. Underlying causes for this variation are not well understood. Several factors, including tobacco smoking, consumption of cruciferous vegetables, and sex, have been associated with modulating CYP1A2 expression. To understand factors regulating expression of CYP1A2 in establishing a causal relationship, this study examined effects of cigarette smoke condensate (CSC), indole-3-carbinol (I3C), and 17β-estradiol (estradiol) on CYP1A2 expression in in vitro systems using human liver and lung cells. Treatment with CSC (2-25 μg/mL) significantly increased levels of CYP1A2 in six cell lines examined, in a concentration- and time-dependent manner. Fold changes in expression levels relative to controls varied among cell lines. CYP1A2 enzymatic activity also increased with CSC exposure. Treatment of H1299 and HepB3 cells with dietary agent I3C (50 and 100 μmol/L) increased CYP1A2 expression. In human cell lines H1299 and H1395, treatment with estradiol (10 and 100 nmol/L) significantly reduced expression of CYP1A2. Using ChIP assays, effects of CSC on histone modifications were analyzed. Increases in H3K4me3 and H4K16ac were observed at several segments in the CYP1A2 gene, whereas H3K27me3 decreased, following CSC treatment. These results suggest that CYP1A2 expression is affected epigenetically by CSC. Additional studies will be needed to further establish regulatory mechanisms underlying effects of various environmental, dietary, and endogenous factors on CYP1A2 expression in better predicting individual variation.

Potential Mechanisms of Hematological Adverse Drug Reactions in Patients Receiving Clozapine in Combination With Proton Pump Inhibitors

Clozapine is a second-generation antipsychotic which has proven efficacy in treating the symptoms of schizophrenia. Although clozapine therapy is associated with a number of adverse drug reactions, it is frequently used. One of the most common adverse drug reactions is gastroesophageal reflux disease which is an indication for treatment with proton pump inhibitors (PPIs). Coadministration of clozapine and PPIs increases the risk of hematological adverse drug reactions, including neutropenia and agranulocytosis. The mechanism in idiosyncratic agranulocytosis is not dose related and involves either a direct toxic or an immune-allergic effect. It is suspected that the clozapine metabolites nitrenium ion and N-desmethylclozapine may cause apoptosis or impair growth of granulocytes. Formation of N-desmethylclozapine is correlated with activity of the cytochrome P450 enzymes 1A2 and 3A4 (CYP1A2 and CYP3A4). Nitrenium ion is produced by the flavin-containing monooxygenase system of leukocytes. A drug interaction between clozapine and a PPI is a consequence of the induction of common metabolic pathways either by the PPI or clozapine. Findings to date suggest that indirect induction of flavin-containing monooxygenase by omeprazole through the aryl hydrocarbon receptor increases the expression of the enzyme mRNA and in the long term may cause the increase in activity. Moreover, induction of CYP1A2, especially by omeprazole and lansoprazole, may increase the serum concentration of N-desmethylclozapine, which can accumulate in lymphocytes and may achieve toxic levels. Another hypothesis that may explain hematological adverse drug reactions is competitive inhibition of CYP2C19, which may contribute to increased serum concentrations of toxic metabolites.

Personalized medicine in psychiatry

BACKGROUND

Personalized medicine is a model in which a patient's unique clinical, genetic, and environmental characteristics are the basis for treatment and prevention. Aim, method, and results: This review aims to describe the current tools, phenomenological features, clinical risk factors, and biomarkers used to provide personalized medicine. Furthermore, this study describes the target areas in which they can be applied including diagnostics, treatment selection and response, assessment of risk of side-effects, and prevention.

DISCUSSION AND CONCLUSION

Personalized medicine in psychiatry is challenged by the current taxonomy, where the diagnostic categories are broad and great biological heterogeneity exists within each category. There is, thus, a gap between the current advanced research prospects and clinical practice, and the current taxonomy is, thus, a poor basis for biological research. The discussion proposes possible solutions to narrow this gap and to move psychiatric research forward towards personalized medicine.

Genetic variation in the human cytochrome P450 supergene family

OBJECTIVES

Single nucleotide variations (SNVs) in the cytochrome P450 (CYP) gene family are a primary cause of interindividual differences in therapeutic effects and adverse reactions to drugs. However, we still lack important information on the extent of CYP polymorphisms at the population level. Here, we developed a comprehensive data set of SNVs in all 57 human CYP genes by integrating data from two extensive population sequencing projects and analyzed the distribution of SNVs in different subpopulations.

MATERIALS AND METHODS

CYP genetic variants derived from the NHLBI and 1000 Genomes project were classified by variant type, frequency, and ethnic origins. The genetic variability of CYP genes was normalized on the basis of nonlinear regression and the total number of genetic variations was estimated by the derived formulas.

RESULTS

In total, we detected 6165 SNVs, of which many were novel. The vast majority (83.2%) of all SNVs in coding regions were very rare (minor allele frequency <0.1%). On the basis of the regression analysis, the total number of genetic variations in human CYP genes was calculated to be 3.4 × 10 and 4.8 × 10 for a population size of one million in Europeans and Africans, respectively.

CONCLUSION

Our results suggest that the variant spectrum of human CYP genes is extensive and only a fraction of SNVs has been characterized to date. Moreover, the multitude of very rare novel sequence variants indicates that the commonly used SNV platforms are not satisfactory for determining the true genotype, which is critical information for personalized treatment with drugs influenced by CYP polymorphisms.

Two Sudden and Unexpected Deaths of Patients with Schizophrenia Associated with Intramuscular Injections of Antipsychotics and Practice Guidelines to Limit the Use of High Doses of Intramuscular Antipsychotics

Intravenous haloperidol has been associated with torsades de pointes (TdP). These two sudden deaths were probable adverse drug reactions (ADRs) following intramuscular (IM) antipsychotics. The autopsies described lack of heart pathology and were highly compatible with the possibility of TdP in the absence of risk factors other than the accumulation of antipsychotics with a high serum peak after the last injection, leading to death within hours. The first case was a 27-year-old African-American male with schizophrenia but no medical issues. His death was probably caused by repeated IM haloperidol injections of 10 mg (totaling 35 mg in 2 days). The second case involves a 42-year-old African-American female with metabolic syndrome. Her probable cause of death was the last ziprasidone IM injection of 20 mg in addition to (1) three extra haloperidol doses (2 hours before the ziprasidone injection, 5 mg oral haloperidol; approximately 21 hours earlier, 5 mg oral haloperidol; and 2 days prior, one 10 mg IM haloperidol injection), (2) 10 mg/day of scheduled oral haloperidol for 6 days before death, and (3) a long-acting paliperidone injection of 156 mg 18 days before death. The study of haloperidol glucuronidation and its impairment in some African-Americans is urgently recommended.

CYP2D6 *6/*6 genotype and drug interactions as cause of haloperidol-induced extrapyramidal symptoms

A 66-year-old male Caucasian, received 1 mg of haloperidol orally and rapidly developed severe iatrogenic extrapyramidal symptoms. Treatment was immediately discontinued, and the side effects resolved. Haloperidol is mainly metabolized by Phase I CYP2D6 and to the lesser extent by CYP3A4 and by Phase II UGT2B7 enzymes. Genotyping was performed revealing CYP2D6*6/*6, CYP3A4*1/*1, and UGT2B7 -161 C/T genotypes, implicating poor, extensive and intermediate metabolism, respectively. Of the CYPs, haloperidol is metabolized by CYP2D6 and CYP3A4 primarily. It was the introduction of ciprofloxacin which was a trigger for the development of adverse drug reaction due to inhibition of CYP3A4, which was in presented patient main metabolic pathway for haloperidol since he was CYP2D6 poor metabolizer. Presented case report highlights the importance of genotyping. Pharmacogenetics testing should be considered when drug toxicity is suspected, polymorphic metabolic pathways used and drugs concomitantly applied.

Pharmacogenetics of Cytochrome P450 Enzymes in American Indian and Caucasian Children Admitted to a Psychiatric Hospital

OBJECTIVE

The cytochrome P450 (CYP450) enzyme system metabolizes many psychiatric medications. We compare frequencies of alleles and phenotypes for CYP2D6, CYP2C9, and CYP2C19 in American Indian (AI) and Caucasian youth treated at a psychiatric hospital in the Northwestern United States.

METHODS

A retrospective chart review evaluated CYP450 pharmacogenetic (PGx) data from the Shodair Children's Hospital Clinical Genetic Laboratory between 2006 and 2014. CYP2D6 genotyping was performed using the xTAG® CYP2D6 Kit (Luminex, Austin, TX). CYP2C9 and CYP2C19 genotyping was performed by laboratory-developed assays using allele-specific quantitative polymerase chain reaction (qPCR) and/or melt-curve analysis.

RESULTS

A total of 123 AIs and 688 Caucasians met criteria for inclusion. The overall prevalence of CYP2D6 poor metabolizers was 8.3% (95% Confidence Interval [CI] 6.1%, 10.4%), 9.3% in Caucasians (95% CI 7.1%, 11.5%), and 2.4% in AIs (95% CI 0%, 5.2%). The overall prevalence of CYP2D6 ultrarapid metabolizers was 1.6% (95% CI 0.7%, 2.5%), 1.6% in the Caucasians (95% CI 0.7%, 2.5%), and 1.6% in AIs (95% CI 0%, 3.9%). The overall prevalence of CYP2C9 poor metabolizers was 3% (95% CI 1.7%, 4.2%), 3.2% in Caucasians (95% CI 1.8%, 4.6%), and 1.8% in AIs (95% CI 0%, 4.2%). The overall prevalence of CYP2C19 poor metabolizers was 2.5% (95% CI 1.3%, 3.6%), 2.9% in Caucasians (95% CI 1.6%, 4.2%), and 0% in AIs. The overall prevalence of CYP2C19 ultrarapid metabolizers was 1.5% (95% CI 0.6%, 2.4%), 1.6% in Caucasians (95% CI 0.6%, 2.6%), and 0.9% in AIs (95% CI 0%, 2.6%).

CONCLUSIONS

This study is the first to identify differences in polymorphism frequencies of the CYP450 system in AIs and Caucasian youth admitted to a psychiatric hospital. Our findings warrant further study of these populations to determine if these differences are generalizable to the larger population of Caucasian and AI/Alaska Native youth in the Northwestern United States.

Possible biomarkers modulating haloperidol efficacy and/or tolerability

Haloperidol (HP) is widely used in the treatment of several forms of psychosis. Despite of its efficacy, HP use is a cause of concern for the elevated risk of adverse drug reactions. adverse drug reactions risk and HP efficacy greatly vary across subjects, indicating the involvement of several factors in HP mechanism of action. The use of biomarkers that could monitor or even predict HP treatment impact would be of extreme importance. We reviewed the elements that could potentially be used as peripheral biomarkers of HP effectiveness. Although a validated biomarker still does not exist, we underlined the several potential findings (e.g., about cytokines, HP metabolites and genotypic biomarkers) which could pave the way for future research on HP biomarkers.