Regional distribution of clomipramine and desmethylclomipramine in rat brain and peripheral organs on chronic clomipramine administration

Haplotype phasing of CYP2D6: an allelic ratio method using Agena MassARRAY data

Pharmacogenomics aims to use the genetic information of an individual to personalize drug prescribing. There is evidence that pharmacogenomic testing before prescription may prevent adverse drug reactions, increase efficacy, and reduce cost of treatment. CYP2D6 is a key pharmacogene of relevance to multiple therapeutic areas. Indeed, there are prescribing guidelines available for medications based on CYP2D6 enzyme activity as deduced from CYP2D6 genetic data. The Agena MassARRAY system is a cost-effective method of detecting genetic variation that has been clinically applied to other genes. However, its clinical application to CYP2D6 has to date been limited by weaknesses such as the inability to determine which haplotype was present in more than one copy for individuals with more than two copies of the CYP2D6 gene. We report application of a new protocol for CYP2D6 haplotype phasing of data generated from the Agena MassARRAY system. For samples with more than two copies of the CYP2D6 gene for which the prior consensus data specified which one was present in more than one copy, our protocol was able to conduct CYP2D6 haplotype phasing resulting in 100% concordance with the prior data. In addition, for three reference samples known to have more than two copies of CYP2D6 but for which the exact number of CYP2D6 genes was unknown, our protocol was able to resolve the number for two out of the three of these, and estimate the likely number for the third. Finally, we demonstrate that our method is applicable to CYP2D6 hybrid tandem configurations.

The Anti-inflammatory Effect of the Tricyclic Antidepressant Clomipramine and Its High Penetration in the Brain Might Be Useful to Prevent the Psychiatric Consequences of SARS-CoV-2 Infection

At the time of writing (December 2020), coronavirus disease 2019 (COVID-19) has already caused more than one million deaths worldwide, and therefore, it is imperative to find effective treatments. The “cytokine storm” induced by Severe Acute Respiratory Syndrome-Coronavirus type 2 (SARS-CoV-2) is a good target to prevent disease worsening, as indicated by the results obtained with tocilizumab and dexamethasone. SARS-CoV-2 can also invade the brain and cause neuro-inflammation with dramatic neurological manifestations, such as viral encephalitis. This could lead to potentially incapacitating long-term consequences, such as the development of psychiatric disorders, as previously observed with SARS-CoV. Several pathways/mechanisms could explain the link between viral infection and development of psychiatric diseases, especially neuro-inflammation induced by SARS-CoV-2. Therefore, it is important to find molecules with anti-inflammatory properties that penetrate easily into the brain. For instance, some antidepressants have anti-inflammatory action and pass easily through the blood brain barrier. Among them, clomipramine has shown very strong anti-inflammatory properties in vitro, in vivo (animal models) and human studies, especially in the brain. The aim of this review is to discuss the potential application of clomipramine to prevent post-infectious mental complications. Repositioning and testing antidepressants for COVID-19 management could help to reduce peripheral and especially central inflammation and to prevent the acute and particularly the long-term consequences of SARS-CoV-2 infection.

How Can Drug Metabolism and Transporter Genetics Inform Psychotropic Prescribing?

Many genetic variants in drug metabolizing enzymes and transporters have been shown to be relevant for treating psychiatric disorders. Associations are strong enough to feature on drug labels and for prescribing guidelines based on such data. A range of commercial tests are available; however, there is variability in included genetic variants, methodology, and interpretation. We herein provide relevant background for understanding clinical associations with specific variants, other factors that are relevant to consider when interpreting such data (such as age, gender, drug-drug interactions), and summarize the data relevant to clinical utility of pharmacogenetic testing in psychiatry and the available prescribing guidelines. We also highlight areas for future research focus in this field.

Pharmacogenomics of Antidepressant and Antipsychotic Treatment: How Far Have We Got and Where Are We Going?

In recent decades, very few new psychiatric drugs have entered the market. Thus, improvement in the use of antidepressant and antipsychotic therapy has to focus mainly on enhanced and more personalized treatment with the currently available drugs. One important aspect of such individualization is emphasizing interindividual differences in genes relevant to treatment, an area that can be termed neuropsychopharmacogenomics. Here, we review previous efforts to identify such critical genetic variants and summarize the results obtained to date. We conclude that most clinically relevant genetic variation is connected to phase I drug metabolism, in particular to genetic polymorphism of CYP2C19 and CYP2D6. To further improve individualized pharmacotherapy, there is a need to take both common and rare relevant mutations into consideration; we discuss the present and future possibilities of using whole genome sequencing to identify patient-specific genetic variation relevant to treatment in psychiatry. Translation of pharmacogenomic knowledge into clinical practice can be considered for specific drugs, but this requires education of clinicians, instructive guidelines, as well as full attention to polypharmacy and other clinically relevant factors. Recent large patient studies (n > 1,000) have replicated previous findings and produced robust evidence warranting the clinical utility of relevant genetic biomarkers. To further judge the clinical and financial benefits of preemptive genotyping in psychiatry, large prospective randomized trials are needed to quantify the value of genetic-based patient stratification in neuropsychopharmacotherapy and to demonstrate the cost-effectiveness of such interventions.

Evaluation of drugs for potential repurposing against COVID-19 using a tier-based scoring system

BACKGROUND

As the coronavirus disease 2019 (COVID-19) pandemic grows daily, we remain with no prophylactic and only minimal therapeutic interventions to prevent or ameliorate severe acute respiratory syndrome Coronavirus 2 (SARS-CoV-2). Prior to SARS-CoV-2 emergence, high throughput screens utilizing clinically developed drugs identified compounds with in vitro inhibitory effect on human coronaviruses that may have potential for repurposing as treatment options for COVID-19. However, caution should be applied to repurposing of these drugs when they are taken out of context of human pharmacokinetic parameters associated with normal therapeutic use.

METHODS

Our aim was to provide a tier-based scoring system to interrogate this data set and match each drug with its human pharmacokinetic criteria, such as route of administration, therapeutic plasma levels and half-life, tissue distribution and safety.

RESULTS

Our analysis excluded most previously identified drugs but identified members of four drug classes (antimalarial amino-quinolones, selective estrogen receptor modulators [SERMs], low potency tricyclic antipsychotics and tricyclic antidepressants) as potential drug candidates for COVID-19. Two of them, the tricyclic antipsychotics and tricyclic antidepressants were further excluded based on a high adverse event profile.

CONCLUSIONS

In summary, our findings using a new pharmacokinetic-based scoring system supports efficacy testing of only a minority of candidates against SARS-CoV-2 infection.

In Vitro and In Vivo Pipeline for Validation of Disease-Modifying Effects of Systems Biology-Derived Network Treatments for Traumatic Brain Injury-Lessons Learned

We developed a pipeline for the discovery of transcriptomics-derived disease-modifying therapies and used it to validate treatments in vitro and in vivo that could be repurposed for TBI treatment. Desmethylclomipramine, ionomycin, sirolimus and trimipramine, identified by in silico LINCS analysis as candidate treatments modulating the TBI-induced transcriptomics networks, were tested in neuron-BV2 microglial co-cultures, using tumour necrosis factor α as a monitoring biomarker for neuroinflammation, nitrite for nitric oxide-mediated neurotoxicity and microtubule associated protein 2-based immunostaining for neuronal survival. Based on (a) therapeutic time window in silico, (b) blood-brain barrier penetration and water solubility, (c) anti-inflammatory and neuroprotective effects in vitro (p < 0.05) and (d) target engagement of Nrf2 target genes (p < 0.05), desmethylclomipramine was validated in a lateral fluid-percussion model of TBI in rats. Despite the favourable in silico and in vitro outcomes, in vivo assessment of clomipramine, which metabolizes to desmethylclomipramine, failed to demonstrate favourable effects on motor and memory tests. In fact, clomipramine treatment worsened the composite neuroscore (p < 0.05). Weight loss (p < 0.05) and prolonged upregulation of plasma cytokines (p < 0.05) may have contributed to the worsened somatomotor outcome. Our pipeline provides a rational stepwise procedure for evaluating favourable and unfavourable effects of systems-biology discovered compounds that modulate post-TBI transcriptomics.

The tricyclic antidepressant clomipramine inhibits neuronal autophagic flux

Antidepressants are commonly prescribed psychotropic substances for the symptomatic treatment of mood disorders. Their primary mechanism of action is the modulation of neurotransmission and the consequent accumulation of monoamines, such as serotonin and noradrenaline. However, antidepressants have additional molecular targets that, through multiple signaling cascades, may ultimately alter essential cellular processes. In this regard, it was previously demonstrated that clomipramine, a widely used FDA-approved tricyclic antidepressant, interferes with the autophagic flux and severely compromises the viability of tumorigenic cells upon cytotoxic stress. Consistent with this line of evidence, we report here that clomipramine undermines autophagosome formation and cargo degradation in primary dissociated neurons. A similar pattern was observed in the frontal cortex and liver of treated mice, as well as in the nematode Caenorhabditis elegans exposed to clomipramine. Together, our findings indicate that clomipramine may negatively regulate the autophagic flux in various tissues, with potential metabolic and functional implications for the homeostatic maintenance of differentiated cells.

Intravenous lipid emulsion therapy for acute clomipramine intoxication in rats

Aim

In this study, to assess the utility of lipid emulsion (ILE) therapy as a treatment option for overdoses of lipophilic drugs, we examined the detoxification effect of ILE therapy in rats that were administered overdoses of the tricyclic antidepressant clomipramine hydrochloride (CMI).

Methods

Female Wistar rats were orally administered 50 mg/kg CMI five times in 2‐h intervals to examine whether intralipos accelerated the elimination of CMI in the peripheral blood. Rats were divided into the intralipos (i.v. 2 g/kg intralipos) and placebo (i.v. saline) groups. The concentrations of CMI and desmethylclomipramine (DMCMI), a metabolite of CMI, in blood were measured over time by high‐performance liquid chromatography. We then gave the animals 100 mg/kg CMI orally to examine whether intralipos could inhibit the distribution of CMI. The CMI and DMCMI concentrations in peripheral blood, liver, and brain were measured 60 min after intralipos administration.

Results

The blood concentration of CMI was significantly higher in the intralipos group than in the placebo group at 60 and 120 min. After a single administration of 100 mg/kg CMI, the ratio of the concentration of CMI in liver/serum was significantly lower in the intralipos group than in the placebo group. We also found a significantly faster elimination rate for CMI in peripheral blood in the intralipos group than in the placebo group.

Conclusion

The distribution of CMI from blood to tissue was suppressed by intralipos. Therefore, ILE therapy is a promising candidate for the treatment of overdoses of lipophilic drugs.

In vivo studies of effects of antidepressants on parotid salivary secretion in the rat

Tricyclic antidepressants (TCA) are well-known xerogenic drugs, while antidepressants such as selective serotonin reuptake inhibitors (SSRI) are considered less xerogenic. The antimuscarinic effect of the TCAs has been considered to be the principal mechanism causing a dry mouth. Although the muscarinic receptor is commonly targeted by xerogenic pharmaceuticals, the salivation reflex arc may be affected at other levels as well. We currently wondered whether or not antidepressants exert an inhibition of the salivary reflex not only at the glandular level but at a central level as well. In this study, the effects of a TCA (clomipramine), a SSRI (citalopram) and a serotonin-noradrenaline reuptake inhibitor (SNRI; venlafaxine) were examined on reflex- (0.5M citric acid applied on the tongue) and methacholine-evoked salivary secretion. While all three compounds inhibited citric acid-evoked secretion (-40 to -60% at 5mg/kg i.v. of the antidepressants), only clomipramine inhibited methacholine-evoked secretion (-30% at 5mg/kg i.v.). On the contrary, both citalopram and venlafaxine increased the methacholine-evoked secretion (+44 to 49%). This was particularly obvious for the salivary protein output (>200%). In the presence of α- and β-adrenoceptor antagonists, the citalopram- and venlafaxine-induced increases were reduced. Thus, antidepressants irrespective of type may exert xerogenic effects by inhibiting the salivary reflex in the central nervous system. However, while TCAs may also hamper the secretory response by antimuscarinic effects, the SSRI and the SNRI groups of pharmaceuticals seem to lack this additional xerogenic mechanism indicating a better therapeutic profile and better opportunities for pharmacological treatment of drug-induced xerostomia.

Association of tardive dyskinesia with variation in CYP2D6: Is there a role for active metabolites?

BACKGROUND

The aim of this study was to examine whether there was an association between tardive dyskinesia (TD) and number of functional CYP2D6 genes.

METHODS

A Caucasian sample of 70 patients was recruited in 1996-1997 from South London and Maudsley National Health Service (NHS) Foundation Trust, UK. Subjects had a DSM-IIIR diagnosis of schizophrenia and were treated with typical antipsychotics at doses equivalent to at least 100 mg chlorpromazine daily for at least 12 months prior to assessment. All patients were genotyped for CYP2D6 alleles*3-5, *41, and for amplifications of the gene.

RESULTS

There were 13 patients with TD. The mean (standard deviation (SD)) years of duration of antipsychotic treatment in TD-positive was 15.8 (7.9) vs TD-negative 11.1 (7.4) (p=0.04). Increased odds of experiencing TD were associated with increased ability to metabolize CYP2D6, as measured by genotypic category (odds ratio (OR)=4.2), increasing duration in treatment (OR=1.0), and having drug-induced Parkinsonism (OR=9.7).

DISCUSSION

We found a significant association between CYP2D6 genotypic category and TD with the direction of effect being an increase in the number of functional CYP2D6 genes being associated with an increased risk of TD. This is the first study to examine the association between TD and CYP2D6 in Caucasians with this number of genotypic categories. In the future, metabolomics may be utilized in the discovery of biomarkers and novel drug targets.

Therapeutic drug monitoring for drugs used in the treatment of substance-related disorders: literature review using a therapeutic drug monitoring appropriateness rating scale

BACKGROUND

The efficacy of drugs for the treatment of substance-related disorders is moderate at best. Therapeutic drug monitoring (TDM) could be an instrument to improve outcomes. Because TDM for most of those drugs is not established, the authors reviewed the literature and built a rating scale to detect the potential added value of TDM for these pharmacologic agents.

METHODS

A literature search was performed for acamprosate, bupropion, buprenorphine, clomethiazole, disulfiram, methadone, naltrexone, and varenicline. The rating scale included 22 items and was divided in five categories: efficacy, toxicity, pharmacokinetics, patient characteristics, and cost-effectiveness. Three reference substances with established TDM were similarly assessed for comparison: clozapine, lithium, and nortriptyline. The three reference substances achieved scores of 15, 12, and 14 points, respectively.

RESULTS

Drugs for treatment of substance-related disorders achieved 3 to 17 points, 17 for methadone, 11 for buprenorphine, 10 for disulfiram, also 10 for naltrexone for the indication opioid-dependence and 9 for the indication alcohol dependence as well as bupropion, 7 points for acamprosate, 6 points for clomethiazole, and 3 for varenicline.

CONCLUSIONS

It is concluded that systematic evaluation of drug- and patient-related variables with the new rating scale can estimate the appropriateness of TDM. Because their rating revealed similar scores as the three reference drugs, it is proposed that TDM should be established for bupropion, buprenorphine, disulfiram or a metabolite, methadone, and naltrexone. An objective rating of drug- and patient-related characteristics could help laboratories focus their method development on the most likely drugs to require TDM along with a thorough drug use evaluation.

NET occupancy by clomipramine and its active metabolite, desmethylclomipramine, in non-human primates in vivo

RATIONALE

Norepinephrine transporter (NET) is one of the key targets for antidepressants such as combined serotonin and norepinephrine reuptake inhibitors as well as some of the tricyclic antidepressants. Clomipramine, a tricyclic antidepressant, has been reported to have an active metabolite, desmethylclomipramine, which has high affinity for NET in vitro. However, the NET occupancy of clomipramine and desmethylclomipramine has not fully been evaluated in vivo.

OBJECTIVES

In this positron emission tomography (PET) study, we investigate NET occupancy by clomipramine and desmethylclomipramine, respectively, in non-human primates with a selective radioligand for NET, (S,S)-[(18)F]FMeNER-D(2).

METHODS

PET measurements were performed with (S,S)-[(18)F]FMeNER-D(2) at baseline and after the intravenous administration of clomipramine and desmethylclomipramine, respectively. NET binding was calculated with the simplified reference tissue model using the caudate as reference region. NET occupancy was calculated as the difference in NET binding between the baseline and pretreatment condition. The relationship between NET occupancy and dose/plasma concentration was evaluated using hyperbolic functions.

RESULTS

NET occupancy by both clomipramine and desmethylclomipramine increased in a dose and plasma concentration-dependent manner. The mean Kd values, expressed as the dose or plasma concentration at which 50% of NET was occupied, were 0.44 mg/kg and 24.5 ng/ml for clomipramine and 0.11 mg/kg and 4.4 ng/ml for desmethylclomipramine.

CONCLUSIONS

Not only desmethylclomipramine but also clomipramine was demonstrated to occupy NET in the non-human primate in vivo. It can thus be assumed that NET occupancy during clinical treatment with clomipramine is a combined effect of unchanged clomipramine and its main metabolite desmethylclomipramine.