The Polymorphic Nuclear Factor NFIB Regulates Hepatic CYP2D6 Expression and Influences Risperidone Metabolism in Psychiatric Patients

The genetic background for interindividual variability of the polymorphic CYP2D6 enzyme activity remains incompletely understood and the role of NFIB genetic polymorphism for this variability was evaluated in this translational study. We investigated the effect of NFIB expression in vitro using 3D liver spheroids, Huh7 cells, and the influence of the NFIB polymorphism on metabolism of risperidone in patients in vivo. We found that NFIB regulates several important pharmacogenes, including CYP2D6. NFIB inhibited CYP2D6 gene expression in Huh7 cells and NFIB expression in livers was predominantly nuclear and reduced at the mRNA and protein level in carriers of the NFIB rs28379954 T>C allele. Based on 604 risperidone treated patients genotyped for CYP2D6 and NFIB, we found that the rate of risperidone hydroxylation was elevated in NFIB rs28379954 T>C carriers among CYP2D6 normal metabolizers, resulting in a similar rate of drug metabolism to what is observed in CYP2D6 ultrarapid metabolizers, with no such effect observed in CYP2D6 poor metabolizers lacking functional enzyme. The results indicate that NFIB constitutes a novel nuclear factor in the regulation of cytochrome P450 genes, and that its polymorphism is a predictor for the rate of CYP2D6 dependent drug metabolism in vivo

Impact of NFIB and CYP1A variants on clozapine serum concentration—A retrospective naturalistic cohort study on 526 patients with known smoking habits

Clinical response of clozapine is closely associated with serum concentration. Although tobacco smoking is the key environmental factor underlying interindividual variability in clozapine metabolism, recent genome-wide studies suggest that CYP1A and NFIB genetic variants may also be of significant importance, but their quantitative impact is unclear. We investigated the effects of the rs2472297 C>T (CYP1A) and rs28379954 T>C (NFIB) polymorphisms on serum concentrations in smokers and nonsmokers. The study retrospectively included 526 patients with known smoking habits (63.7% smokers) from a therapeutic drug monitoring service in Norway. Clozapine dose-adjusted concentrations (C/D) and patient proportions with subtherapeutic levels (<1070 nmol/L) were compared between CYP1A/NFIB variant allele carriers and homozygous wild-type carriers (noncarriers), in both smokers and nonsmokers. Clozapine C/D was reduced in patients carrying CYP1A-T and NFIB-C variants versus noncarriers, both among smokers (−48%; p < 0.0001) and nonsmokers (−35%; p = 0.028). Patients who smoke carrying CYP1A-T and NFIB-C variants had a 66% reduction in clozapine C/D versus nonsmoking noncarriers (p < 0.0001). The patient proportion with subtherapeutic levels was 2.9-fold higher in patients who smoke carrying NFIB-C and CYP1A-T variants versus nonsmoking noncarriers (p < 0.0001). In conclusion, CYP1A and NFIB variants have significant and additive impact on clozapine dose requirements for reaching target serum concentrations. Patients who smoke carrying the studied CYP1A and NFIB variants, comprising 2.5% of the study population, may need threefold higher doses to prevent risk of clozapine undertreatment. The results suggest that pre-emptive genotyping of NFIB and CYP1A may be utilized to guide clozapine dosing and improve clinical outcomes in patients with treatment-resistant schizophrenia. © 2022 The Authors. Clinical and Translational Science published by Wiley Periodicals LLC on behalf of American Society for Clinical Pharmacology and Therapeutics

Polygenic overlap with body-mass index improves prediction of treatment-resistant schizophrenia

Treatment resistant schizophrenia (TRS) is characterized by repeated treatment failure with antipsychotics. A recent genome-wide association study (GWAS) of TRS showed a polygenic architecture, but no significant loci were identified. Clozapine is shown to be the superior drug in terms of clinical effect in TRS; at the same time it has a serious side effect profile, including weight gain. Here, we sought to increase power for genetic discovery and improve polygenic prediction of TRS, by leveraging genetic overlap with Body Mass Index (BMI). We analysed GWAS summary statistics for TRS and BMI applying the conditional false discovery rate (cFDR) framework. We observed cross-trait polygenic enrichment for TRS conditioned on associations with BMI. Leveraging this cross-trait enrichment, we identified 2 novel loci for TRS at cFDR <0.01, suggesting a role of MAP2K1 and ZDBF2. Further, polygenic prediction based on the cFDR analysis explained more variance in TRS when compared to the standard TRS GWAS. These findings highlight putative molecular pathways which may distinguish TRS patients from treatment responsive patients. Moreover, these findings confirm that shared genetic mechanisms influence both TRS and BMI and provide new insights into the biological underpinnings of metabolic dysfunction and antipsychotic treatment.publishedVersio

Regulation of legumain in human cells

The studies presented in this thesis aimed to investigate the regulation of the cysteine protease legumain in various human cells (paper I-IV), effects of statins (paper II and III) and a legumain-cleavable colchicine prodrug (paper IV). Legumain is the only known asparaginyl endoprotease and shows high structural similarities to the caspases. Legumain is reported to participate in extracellular matrix degradation by processing of pro-matrix metalloprotase-2, fibronectin, cathepsin B and L. The subcellular localization of legumain is thought to be mainly lysosomal, and dysregulation of legumain is suggested to be of consequence for proteolytic degradation and tissue remodeling. High legumain expression is correlated with cancer progression and malignancy as well as atherosclerotic plaque rupture, and pharmacological intervention targeting legumain may be useful. In the present work, legumain and/or cystatin E/M over-expressing HEK293 cells were established, and used to study regulation, subcellular localization and interplay of legumain and cystatin E/M (paper I). Legumain over-expressing HEK293 cells secreted prolegumain that was able to be internalized and subsequently activated intracellularly (paper I). Cystatin E/M (the most potent endogenous inhibitor of legumain) was also secreted and internalized, and thus able to regulate legumain activity both intra- and extracellularly (paper I). Macrophages are key regulators in cancer and atherosclerosis. In paper II, legumain expression, activity and secretion were highly up-regulated during monocyte-to-macrophage differentiation (paper II). Interestingly, 90 % of the legumain produced in M-CSF-stimulated macrophages was secreted as prolegumain, and surprisingly legumain was detected in human sera (paper II). Secreted legumain points to extracellular functions, and quantification may have diagnostic or prognostic value. Statins (HMG-CoA reductase inhibitors) have so-called pleiotropic effects beyond lowering the serum cholesterol level. These drugs are generally well tolerated, although skeletal muscle side effects are known, especially by simvastatin. In monocytes from patients treated with atorvastatin, legumain mRNA is shown to be down-regulated. Herein, statins were shown to inhibited legumain activity, expression, processing and secretion in various human cells types, such as macrophages (paper II), myotubes (paper III), and in legumain over-expressing HEK293 cells (Fig. 8), probably by interfering with the intracellular vesicular trafficking or by increasing the pH of the lysosomes (paper III). Legumain inhibition may contribute to the pleiotropic effects of statins. A novel pharmacological strategy is to construct a prodrug of a cytotoxic drug conjugated with a legumain-cleavable peptide (Ala-Ala-Asn), which upon cleavage by legumain becomes cytotoxic to legumain over-expressing cancer cells and tissues. In paper IV, a novel legumain-cleavable colchicine prodrug (Suc-Ala-Ala-Asn-Valcolchicine) were synthesized and showed cell-specific toxicity towards cells expressing active legumain (legumain over-expressing HEK293 cells and HCT116 colorectal cancer cell). In conclusion, the studies presented in this thesis have contributed to new knowledge about regulation of the cysteine protease legumain. It has demonstrated that regulation of legumain occur both extra- and intracellular by cystatin E/M. Pharmacological inhibition of legumain by statins or by utilizing legumain to release cytotoxic colchicine from a legumaincleavable prodrug may be of therapeutic value in preventing morbidity and mortality in cancer and atherosclerosis

Impact of age and CYP2D6 genotype on exposure of zuclopenthixol in patients using long-acting injectable versus oral formulation-an observational study including 2044 patients

Purpose Zuclopenthixol is an antipsychotic available as oral and long-acting injectable (LAI) formulations. The aim of this study was to investigate the effect of age on zuclopenthixol exposure during oral and LAI administrations without and with adjustment for CYP2D6 genotype. Methods Data on serum concentrations of zuclopenthixol and CYP2D6 genotype (available for 28.2% of the population) from patients using oral or LAI zuclopenthixol were included retrospectively from a therapeutic drug monitoring service during the period 2005–2019. As a measure of exposure, dose-adjusted serum concentration (C/D ratio) was used. Based on age, patients were grouped to older (≥ 65 years) or younger (18–64 years). Linear mixed model analyses without and with adjustment for CYP2D6 genotype were used. Results Serum concentrations of zuclopenthixol from 1145 (14.1% older) and 899 patients (24.6% older) in the LAI and oral groups were included, respectively. Compared with younger patients, older patients had a higher C/D ratio of zuclopenthixol for LAI (+ 25–33%, p < 0.001) and oral formulation (+ 25–29%, p ≤ 0.003) without and with adjustment for CYP2D6 genotype. The doses were lower in older versus younger patients (oral: − 30%; LAI: − 20%; p < 0.001). Compared with the younger LAI users without reduced CYP2D6 function, a higher C/D ratio was observed in the older LAI users with reduced CYP2D6 function (+ 104%, p < 0.001). Conclusion The present study showed that zuclopenthixol exposure increases in older patients and that the older LAI users with reduced CYP2D6 function are exposed to high serum concentrations. Also, the present study showed that similar dose reductions are required for oral and LAI users

Undetectable or subtherapeutic serum levels of antipsychotic drugs preceding switch to clozapine

Abstract Adequate antipsychotic treatment intensity is required for defining treatment-resistant schizophrenia (TRS) and justifying clozapine treatment. We investigated the occurrence of undetectable or subtherapeutic serum levels of oral antipsychotics preceding switch to clozapine as an endpoint of TRS. For patients starting clozapine, 12-month retrospective reviews of antipsychotic serum concentration measurements were performed in a Norwegian therapeutic drug monitoring (TDM) database from 2005 to 2017. Undetectable levels in high-sensitive analytical assays defined ‘no drug use’, while levels &lt;50% of the lower reference range defined ‘subtherapeutic use’. Similar data were collected for patients switching to long-acting injectable (LAI) antipsychotics, as a reference of ‘no or subtherapeutic drug use’. Nineteen of 353 patients initiating clozapine (5.4%) had a recent history of undetectable antipsychotic drug levels compared to 91 of 1048 (8.7%) initiating LAI. Another 19 patients starting clozapine (5.4%) had recent events of subtherapeutic levels. In conclusion, the present retrospective study may indicate that every 10th patient starting clozapine has a recent history of undetectable or subtherapeutic serum levels of oral antipsychotics. The clinical implications of the present study for the assessment of TRS should be investigated prospectively in further studies

Absolute and Dose-Adjusted Serum Concentrations of Clozapine in Patients Switching vs. Maintaining Treatment: An Observational Study of 1979 Patients

Background Clozapine is an effective drug for the management of schizophrenia that has not responded to other agents, but some patients experience insufficient or adverse effects and discontinue treatment. Objective We investigated a potential association between clozapine serum concentrations and switching to other antipsychotics in a large real-world patient population from a therapeutic drug monitoring service. Methods Absolute and dose-adjusted serum concentrations (concentration-to-dose ratios [C/D ratios]) of clozapine during dosing between 100 and 1000 mg/day were measured in 1979 Norwegian patients during the period 2005–2019. These variables were compared in patients switching to other antipsychotic drugs versus maintaining clozapine treatment using linear mixed models. Smoking habits were known for 49% of the patients. To prevent potential nonadherence affecting clozapine switching, only patients with serum concentrations above 50% of the lower reference range were included. Results In total, 190 patients (9.6%) switched from clozapine to another antipsychotic drug during the study period, whereas the remaining patients were not detected as switchers and were interpreted as maintaining treatment. Patients switching treatment had 23.5% lower absolute concentrations (954 vs. 1245 nmol/L; p < 0.001) and 15.7% lower daily doses (305 vs. 362 mg/day; p < 0.001) of clozapine than did nonswitchers, making the clozapine C/D ratio 9.7% lower in switchers than in nonswitchers after correcting for smoking habits (2.80 vs. 3.10 nmol/L/mg/day; p = 0.032). Conclusions The present study suggests that decreased absolute and dose-adjusted serum concentrations of clozapine were associated with clozapine discontinuation. The significantly reduced clozapine concentrations regardless of prescribed dose in switchers versus nonswitchers may indicate a pharmacokinetic mechanism underlying the risk of clozapine discontinuation

Metabolite Profiling of Clozapine in Patients Switching Versus Maintaining Treatment: A Retrospective Pilot Study

Purpose/Background Pharmacokinetics may be of relevance for the risk of clozapine discontinuation. We compared metabolite profiles, accounting for smoking habits, in patients switching versus maintaining clozapine treatment at therapeutic concentrations. Methods/Procedures Adult patients with clozapine serum levels above 1070 nmol/L (350 ng/mL) were retrospectively included from a Norwegian therapeutic drug monitoring service during 2018–2020. Inclusion criteria were (1) known smoking habits, (2) blood sample drawn within 10 to 30 hours after last clozapine intake, and (3) detectable levels of N-desmethylclozapine, clozapine-N-oxide, clozapine-5N-glucuronide, or clozapine-N+-glucuronide. Patients comedicated with cytochrome P450 enzyme inducers, inhibitors, or valproic acid were excluded. The high-resolution mass spectrometry assay enabled detection of 21 clozapine metabolites. Metabolite profiles were compared between patients switching treatment (switchers), measured as clozapine being replaced by another antipsychotic drug in blood samples, versus maintaining clozapine treatment (nonswitchers) during the study period. Findings/Results Of the 84 patients fulfilling the study criteria, 7 patients (8.3%) were identified as clozapine switchers. After correcting for smoking habits, the clozapine-5N-glucuronide/clozapine ratio was 69% lower (P < 0.001), while the clozapine-N+-glucuronide/clozapine-5N-glucuronide ratio was 143% higher (P = 0.026), respectively, in switchers versus nonswitchers. The other metabolite ratios did not significantly differ between switchers and nonswitchers. Implications/Conclusions The present study found a significantly reduced 5N-glucuronidation phenotype in patients switching from clozapine at therapeutic serum concentrations (>1070 nmol/L) to other antipsychotic drugs. This may indicate that glucuronidation, as a potential detoxification mechanism, is related to clozapine tolerability. However, the causality of this observation needs to be investigated in future studies with larger patient populations