Pharmacogenetic Factors of Clozapine-Induced Metabolic Syn-drome

(1) Introduction: Despite modern therapies, approximately 20-30% of patients with schizophrenia re-main resistant to psychopharmacotherapy. Clozapine is the only antipsychotic with proven efficacy for treat-ment resistance in schizophrenia (TRS). The most common adverse drug reaction (ADR) during clozapine ad-ministration are metabolic disturbances, particularly metabolic syndrome (MS). Because MS leads to a twofold increase in mortality from cardiovascular disease and a 1.5-fold increase in mortality from all causes, and clozap-ine is often the only treatment option for TRS, it is critical to monitor and management metabolic abnormalities. The high interindividual differences in the development of clozapine-induced MS suggest that genetic factors may play an important role. (2) Purpose: The aim of this study was to identify relevant single nucleotide poly-morphisms (SNPs) of candidate genes for clozapine-induced MS, because based on these data, a genetic risk panel can be constructed to assess the likelihood of developing clozapine-induced MS in patients with schizo-phrenia. (3) Materials and Methods: We searched for full-text publications in PubMed, Web of Science, Springer, Google Scholar, and electronic libraries in English and Russian, available from inception to 30 October 2023. Keywords were the following: metabolic disturbances, clozapine, metabolic syndrome, schizophrenia, genes, adverse drug reactions, antipsychotics, pharmacogenetics, genetic biomarker, single nucleotide variant, poly-morphism, association, variation, and metabolic syndrome genes. (4) Results: we included 6 naturalistic cross-sectional open-label trials, included patients with schizophrenia, schizoaffective, schizophreniform disorder or psychotic disorder, who were treated with first and second generations antipsychotics, among which there was also clozapine and 1 meta-analysis which reviewed association between HTR2C gene polymorphisms and anti-psychotic-induced MS in schizophrenia patients. According to the results of our scoping review the carriage of SNPs in the studied candidate genes associated with clozapine-induced MS are the following: 1) CYP1A2 gene: genotype AA of rs762551 (NG_008431.2:g.32035C>A); 2) CYP2C19 gene: CYP2C19*2 polymorphism; 3) HTR2C gene: genotype CC of rs518147 (NM_000868.2:c.-697G>C), minor allele C of rs1414334 (NG_012082.3:g.324497C>G), genotype CC of rs518147 (NM_000868.2:c.-697G>C), genotype GG of rs12836771 (NG_012082.3:g.71829A>G); 4) LEP gene: genotypes AG and GG of rs7799039 (NG_044977.1:g.475G>A); 5) LEPR gene: genotypes AG and GG of rs1137101 (NG_015831.2:g.177266A>G). (4) Conclusions: Uncovering the genetic biomarkers of clozapine-induced MS may provide a key to developing a strategy for the personalized prevention and treatment of this ADRs of clozapine in patients with schizophrenia spectrum disorders in real clinical prac-tice.