CYP2D6#Ligands
{{Short description|Human liver enzyme}}
{{Use dmy dates|date=December 2023}}
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{{Infobox_gene}}
Cytochrome P450 2D6 (CYP2D6) is an enzyme that in humans is encoded by the CYP2D6 gene. CYP2D6 is primarily expressed in the liver. It is also highly expressed in areas of the central nervous system, including the substantia nigra.
CYP2D6, a member of the cytochrome P450 mixed-function oxidase system, is one of the most important enzymes involved in the metabolism of xenobiotics in the body. In particular, CYP2D6 is responsible for the metabolism and elimination of approximately 25% of clinically used drugs, via the addition or removal of certain functional groups – specifically, hydroxylation, demethylation, and dealkylation.{{cite journal | vauthors = Wang B, Yang LP, Zhang XZ, Huang SQ, Bartlam M, Zhou SF | title = New insights into the structural characteristics and functional relevance of the human cytochrome P450 2D6 enzyme | journal = Drug Metabolism Reviews | volume = 41 | issue = 4 | pages = 573–643 | year = 2009 | pmid = 19645588 | doi = 10.1080/03602530903118729 | s2cid = 41857580 }} CYP2D6 also activates some prodrugs. This enzyme also metabolizes several endogenous substances, such as N,N-Dimethyltryptamine, hydroxytryptamines, neurosteroids, and both m-tyramine and p-tyramine which CYP2D6 metabolizes into dopamine in the brain and liver.{{cite journal | vauthors = Wang X, Li J, Dong G, Yue J | title = The endogenous substrates of brain CYP2D | journal = European Journal of Pharmacology | volume = 724 | pages = 211–218 | date = February 2014 | pmid = 24374199 | doi = 10.1016/j.ejphar.2013.12.025 }}
{{cite journal |
vauthors = Good M, Joel Z, Benway T, Routledge C, Timmermann C, Erritzoe D, Weaver R, Allen G, Hughes C, Topping H, Bowman A, James E |
title = Pharmacokinetics of N,N-dimethyltryptamine in Humans | journal = European Journal of Drug Metabolism and Pharmaco Kinetics | doi = 10.1007/s13318-023-00822-y | date = 2023-04-22 |
volume = 48 |
issue = 3 |
pages = 311–327 | pmid = 37086340 | pmc = 10122081}}
Considerable variation exists in the efficiency and amount of CYP2D6 enzyme produced between individuals. Hence, for drugs that are metabolized by CYP2D6 (that is, are CYP2D6 substrates), certain individuals will eliminate these drugs quickly (ultrarapid metabolizers) while others slowly (poor metabolizers). If a drug is metabolized too quickly, it may decrease the drug's efficacy while if the drug is metabolized too slowly, toxicity may result. So, the dose of the drug may have to be adjusted to take into account of the speed at which it is metabolized by CYP2D6.{{cite journal | vauthors = Walko CM, McLeod H | title = Use of CYP2D6 genotyping in practice: tamoxifen dose adjustment | journal = Pharmacogenomics | volume = 13 | issue = 6 | pages = 691–697 | date = April 2012 | pmid = 22515611 | doi = 10.2217/pgs.12.27 }} Individuals who exhibit an ultrarapid metabolizer phenotype, metabolize prodrugs, such as codeine or tramadol, more rapidly, leading to higher than therapeutic levels.{{cite book|pmid=28520365 |date=2012 |title=Tramadol Therapy and CYP2D6 Genotype | vauthors = Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, Dean L, Kane M }}{{cite book|pmid=28520350 |date=2012 |title=Codeine Therapy and CYP2D6 Genotype | vauthors = Pratt VM, Scott SA, Pirmohamed M, Esquivel B, Kattman BL, Malheiro AJ, Dean L, Kane M }} A case study of the death of an infant breastfed by an ultrarapid metabolizer mother taking codeine impacted postnatal pain relief clinical practices, but was later debunked.{{cite journal | vauthors = Zipursky J, Juurlink DN | title = The Implausibility of Neonatal Opioid Toxicity from Breastfeeding | journal = Clinical Pharmacology and Therapeutics | volume = 108 | issue = 5 | pages = 964–970 | date = November 2020 | pmid = 32378749 | doi = 10.1002/cpt.1882 | s2cid = 218535295 }} These drugs may also cause serious toxicity in ultrarapid metabolizer patients when used to treat other post-operative pain, such as after tonsillectomy.{{cite journal | vauthors = Sadhasivam S, Myer CM | title = Preventing opioid-related deaths in children undergoing surgery | journal = Pain Medicine | volume = 13 | issue = 7 | pages = 982–3; author reply 984 | date = July 2012 | pmid = 22694279 | doi = 10.1111/j.1526-4637.2012.01419.x | doi-access = free }}{{cite journal | vauthors = Kelly LE, Rieder M, van den Anker J, Malkin B, Ross C, Neely MN, Carleton B, Hayden MR, Madadi P, Koren G | title = More codeine fatalities after tonsillectomy in North American children | journal = Pediatrics | volume = 129 | issue = 5 | pages = e1343–e1347 | date = May 2012 | pmid = 22492761 | doi = 10.1542/peds.2011-2538 | url = https://publications.aap.org/pediatrics/article-pdf/129/5/e1343/896222/peds_2011-2538.pdf | access-date = 2 February 2024 | url-status = live | s2cid = 14167063 | archive-url = https://web.archive.org/web/20240202144200/https://publications.aap.org/pediatrics/article-pdf/129/5/e1343/896222/peds_2011-2538.pdf | archive-date = 2 February 2024 }}{{cite journal | vauthors = Prows CA, Zhang X, Huth MM, Zhang K, Saldaña SN, Daraiseh NM, Esslinger HR, Freeman E, Greinwald JH, Martin LJ, Sadhasivam S | title = Codeine-related adverse drug reactions in children following tonsillectomy: a prospective study | journal = The Laryngoscope | volume = 124 | issue = 5 | pages = 1242–1250 | date = May 2014 | pmid = 24122716 | doi = 10.1002/lary.24455 | s2cid = 5326129 }} Other drugs may function as inhibitors of CYP2D6 activity or inducers of CYP2D6 enzyme expression that will lead to decreased or increased CYP2D6 activity respectively. If such a drug is taken at the same time as a second drug that is a CYP2D6 substrate, the first drug may affect the elimination rate of the second through what is known as a drug-drug interaction.{{cite journal | vauthors = Teh LK, Bertilsson L | title = Pharmacogenomics of CYP2D6: molecular genetics, interethnic differences and clinical importance | journal = Drug Metabolism and Pharmacokinetics | volume = 27 | issue = 1 | pages = 55–67 | year = 2012 | pmid = 22185816 | doi = 10.2133/dmpk.DMPK-11-RV-121 }}
Gene
The gene is located on chromosome 22q13.1. near two cytochrome P450 pseudogenes (CYP2D7P and CYP2D8P).{{cite journal | vauthors = Ahmad HI, Afzal G, Jamal A, Kiran S, Khan MA, Mehmood K, Kamran Z, Ahmed I, Ahmad S, Ahmad A, Hussain J, Almas S | title = In Silico Structural, Functional, and Phylogenetic Analysis of Cytochrome (CYPD) Protein Family | journal = BioMed Research International | volume = 2021 | pages = 5574789 | date = 2021 | pmid = 34046497 | pmc = 8128545 | doi = 10.1155/2021/5574789 | doi-access = free }} Among them, CYP2D7P originated from CYP2D6 in a stem lineage of great apes and humans,{{cite journal | vauthors = Wang H, Tompkins LM | title = CYP2B6: new insights into a historically overlooked cytochrome P450 isozyme | journal = Current Drug Metabolism | volume = 9 | issue = 7 | pages = 598–610 | date = September 2008 | pmid = 18781911 | pmc = 2605793 | doi = 10.2174/138920008785821710 }} the CYP2D8P originated from CYP2D6 in a stem lineage of Catarrhine and New World monkeys' stem lineage.{{cite journal | vauthors = Yasukochi Y, Satta Y | title = Evolution of the CYP2D gene cluster in humans and four non-human primates | journal = Genes & Genetic Systems | volume = 86 | issue = 2 | pages = 109–116 | date = 2011 | pmid = 21670550 | doi = 10.1266/ggs.86.109 | doi-access = free }} Alternatively spliced transcript variants encoding different isoforms have been found for this gene.{{cite web| title = Entrez Gene: CYP2D6 cytochrome P450, family 2, subfamily D, polypeptide 6| url = https://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=1565| access-date = 3 November 2017| archive-date = 8 March 2010| archive-url = https://web.archive.org/web/20100308050423/http://www.ncbi.nlm.nih.gov/sites/entrez?Db=gene&Cmd=ShowDetailView&TermToSearch=1565| url-status = live}}
Genotype/phenotype variability
CYP2D6 shows the largest phenotypical variability among the CYPs, largely due to genetic polymorphism. The genotype accounts for normal, reduced, and non-existent CYP2D6 function in subjects. Pharmacogenomic tests are now available to identify patients with variations in the CYP2D6 allele and have been shown to have widespread use in clinical practice.
The CYP2D6 function in any particular subject may be described as one of the following:{{cite journal | vauthors = Bertilsson L, Dahl ML, Dalén P, Al-Shurbaji A | title = Molecular genetics of CYP2D6: clinical relevance with focus on psychotropic drugs | journal = British Journal of Clinical Pharmacology | volume = 53 | issue = 2 | pages = 111–122 | date = February 2002 | pmid = 11851634 | pmc = 1874287 | doi = 10.1046/j.0306-5251.2001.01548.x }}
- poor metabolizer – little or no CYP2D6 function
- intermediate metabolizers – metabolize drugs at a rate somewhere between the poor and extensive metabolizers
- extensive metabolizer – normal CYP2D6 function
- ultrarapid metabolizer – multiple copies of the CYP2D6 gene are expressed, so greater-than-normal CYP2D6 function occurs
A patient's CYP2D6 phenotype is often clinically determined via the administration of debrisoquine (a selective CYP2D6 substrate) and subsequent plasma concentration assay of the debrisoquine metabolite (4-hydroxydebrisoquine).{{cite journal | vauthors = Llerena A, Dorado P, Peñas-Lledó EM | title = Pharmacogenetics of debrisoquine and its use as a marker for CYP2D6 hydroxylation capacity | journal = Pharmacogenomics | volume = 10 | issue = 1 | pages = 17–28 | date = January 2009 | pmid = 19102711 | doi = 10.2217/14622416.10.1.17 }}
The type of CYP2D6 function of an individual may influence the person's response to different doses of drugs that CYP2D6 metabolizes. The nature of the effect on the drug response depends not only on the type of CYP2D6 function, but also on the extent to which processing of the drug by CYP2D6 results in a chemical that has an effect that is similar, stronger, or weaker than the original drug, or no effect at all. For example, if CYP2D6 converts a drug that has a strong effect into a substance that has a weaker effect, then poor metabolizers (weak CYP2D6 function) will have an exaggerated response to the drug and stronger side-effects; conversely, if CYP2D6 converts a different drug into a substance that has a greater effect than its parent chemical, then ultrarapid metabolizers (strong CYP2D6 function) will have an exaggerated response to the drug and stronger side-effects.{{cite journal | vauthors = Lynch T, Price A | title = The effect of cytochrome P450 metabolism on drug response, interactions, and adverse effects | journal = American Family Physician | volume = 76 | issue = 3 | pages = 391–396 | date = August 2007 | pmid = 17708140 }} Information about how human genetic variation of CYP2D6 affects response to medications can be found in databases such PharmGKB,{{cite web |title=PharmGKB |url=https://www.pharmgkb.org/gene/PA128/prescribingInfo |access-date=3 October 2022 |website=PharmGKB |language=en |archive-date=3 October 2022 |archive-url=https://web.archive.org/web/20221003090823/https://www.pharmgkb.org/gene/PA128/prescribingInfo |url-status=live }} Clinical Pharmacogenetics Implementation Consortium (CPIC).{{cite web |title=CYP2D6 CPIC guidelines |url=https://cpicpgx.org/gene/cyp2d6/ |access-date=3 October 2022 |website=cpicpgx.org |language=en-US |archive-date=3 October 2022 |archive-url=https://web.archive.org/web/20221003084825/https://cpicpgx.org/gene/cyp2d6/ |url-status=live }}
Genetic basis of variability
The variability in metabolism is due to multiple different polymorphisms of the CYP2D6 allele, located on chromosome 22. Subjects possessing certain allelic variants will show normal, decreased, or no CYP2D6 function, depending on the allele. Pharmacogenomic tests are now available to identify patients with variations in the CYP2D6 allele and have been shown to have widespread use in clinical practice.{{cite journal | vauthors = Dinama O, Warren AM, Kulkarni J | title = The role of pharmacogenomic testing in psychiatry: Real world examples | journal = The Australian and New Zealand Journal of Psychiatry | volume = 48 | issue = 8 | pages = 778 | date = August 2014 | pmid = 24413808 | doi = 10.1177/0004867413520050 | s2cid = 206399446 }} The current known alleles of CYP2D6 and their clinical function can be found in databases such as PharmVar.{{Cite web |title=PharmVar |url=https://www.pharmvar.org/gene/CYP2D6 |access-date=2024-02-15 |website=www.pharmvar.org |archive-date=19 May 2020 |archive-url=https://web.archive.org/web/20200519021852/https://www.pharmvar.org/gene/CYP2D6 |url-status=live }}
Ethnic factors in variability
Ethnicity is a factor in the occurrence of CYP2D6 variability. The reduction of the liver cytochrome CYP2D6 enzyme occurs approximately in 7–10% in white populations, and is lower in most other ethnic groups such as Asians and African-Americans at 2% each. A complete lack of CYP2D6 enzyme activity, wherein the individual has two copies of the polymorphisms that result in no CYP2D6 activity at all, is said to be about 1-2% of the population.{{cite book|title=Pharmacology and the Nursing Process | vauthors = Lilley LL, Harrington S, Snyder JS, Swart B |publisher=Mosby Elsevier|year=2007|isbn=9780779699711|location=Toronto|pages=25}} The occurrence of CYP2D6 ultrarapid metabolizers appears to be greater among Middle Eastern and North African populations.{{cite journal | vauthors = McLellan RA, Oscarson M, Seidegård J, Evans DA, Ingelman-Sundberg M | title = Frequent occurrence of CYP2D6 gene duplication in Saudi Arabians | journal = Pharmacogenetics | volume = 7 | issue = 3 | pages = 187–191 | date = June 1997 | pmid = 9241658 | doi = 10.1097/00008571-199706000-00003 }}{{cite journal | vauthors = Owen RP, Sangkuhl K, Klein TE, Altman RB | title = Cytochrome P450 2D6 | journal = Pharmacogenetics and Genomics | volume = 19 | issue = 7 | pages = 559–562 | date = July 2009 | pmid = 19512959 | pmc = 4373606 | doi = 10.1097/FPC.0b013e32832e0e97 }} In Ethiopia, a particularly high percentage (30%) of the population are ultrametabolizers. As a result, the analgesic codeine is banned in Ethiopia due to the high rate of adverse events associated with ultrarapid metabolism of codeine in this population.{{cite journal | vauthors = Baker JL, Shriner D, Bentley AR, Rotimi CN | title = Pharmacogenomic implications of the evolutionary history of infectious diseases in Africa | journal = The Pharmacogenomics Journal | volume = 17 | issue = 2 | pages = 112–120 | date = March 2017 | pmid = 27779243 | pmc = 5380847 | doi = 10.1038/tpj.2016.78 }}
Caucasians with European descent predominantly (around 71%) have the functional group of CYP2D6 alleles, producing extensive metabolism, while functional alleles represent only around 50% of the allele frequency in populations of Asian descent.{{cite journal | vauthors = Bradford LD | title = CYP2D6 allele frequency in European Caucasians, Asians, Africans and their descendants | journal = Pharmacogenomics | volume = 3 | issue = 2 | pages = 229–243 | date = March 2002 | pmid = 11972444 | doi = 10.1517/14622416.3.2.229 }}
This variability is accounted for by the differences in the prevalence of various CYP2D6 alleles among the populations–approximately 10% of whites are intermediate metabolizers, due to decreased CYP2D6 function, because they appear to have the one (heterozygous) non-functional CYP2D6*4 allele,{{cite journal | vauthors = Droll K, Bruce-Mensah K, Otton SV, Gaedigk A, Sellers EM, Tyndale RF | title = Comparison of three CYP2D6 probe substrates and genotype in Ghanaians, Chinese and Caucasians | journal = Pharmacogenetics | volume = 8 | issue = 4 | pages = 325–333 | date = August 1998 | pmid = 9731719 | doi = 10.1097/00008571-199808000-00006 }} while approximately 50% of Asians possess the decreased functioning CYP2D6*10 allele.
Ligands
Following is a table of selected substrates, inducers and inhibitors of CYP2D6. Where classes of agents are listed, there may be exceptions within the class.
Inhibitors of CYP2D6 can be classified by their potency, such as:
- Strong inhibitor being one that causes at least a 5-fold increase in the plasma AUC values of sensitive substrates metabolized through CYP2D6, or more than 80% decrease in clearance thereof.
- Moderate inhibitor being one that causes at least a 2-fold increase in the plasma AUC values of sensitive substrates metabolized through CYP2D6, or 50-80% decrease in clearance thereof.
- Weak inhibitor being one that causes at least a 1.25-fold but less than 2-fold increase in the plasma AUC values of sensitive substrates metabolized through CYP2D6, or 20-50% decrease in clearance thereof.
=Dopamine biosynthesis=
{{Catecholamine and trace amine biosynthesis|caption=In humans, catecholamines and phenethylaminergic trace amines are derived from the amino acid phenylalanine. It is well established that dopamine is produced from L-tyrosine via L-dopa; however, recent evidence has shown that CYP2D6 is expressed in the human brain and catalyzes the biosynthesis of dopamine from L-tyrosine via p-tyramine. Similarly, CYP2D6 also metabolizes m-tyramine into dopamine.}}
References
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Further reading
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- {{cite journal | vauthors = Smith G, Stubbins MJ, Harries LW, Wolf CR | title = Molecular genetics of the human cytochrome P450 monooxygenase superfamily | journal = Xenobiotica; the Fate of Foreign Compounds in Biological Systems | volume = 28 | issue = 12 | pages = 1129–1165 | date = December 1998 | pmid = 9890157 | doi = 10.1080/004982598238868 }}
- {{cite journal | vauthors = Wolf CR, Smith G | title = Cytochrome P450 CYP2D6 | journal = IARC Scientific Publications | issue = 148 | pages = 209–229 | year = 1999 | pmid = 10493260 }}
- {{cite journal | vauthors = Ding X, Kaminsky LS | title = Human extrahepatic cytochromes P450: function in xenobiotic metabolism and tissue-selective chemical toxicity in the respiratory and gastrointestinal tracts | journal = Annual Review of Pharmacology and Toxicology | volume = 43 | pages = 149–173 | year = 2003 | pmid = 12171978 | doi = 10.1146/annurev.pharmtox.43.100901.140251 }}
- {{cite journal | vauthors = Lilienfeld S | title = Galantamine--a novel cholinergic drug with a unique dual mode of action for the treatment of patients with Alzheimer's disease | journal = CNS Drug Reviews | volume = 8 | issue = 2 | pages = 159–176 | year = 2006 | pmid = 12177686 | pmc = 6741688 | doi = 10.1111/j.1527-3458.2002.tb00221.x }}
- {{cite journal | vauthors = Yu AM, Idle JR, Gonzalez FJ | title = Polymorphic cytochrome P450 2D6: humanized mouse model and endogenous substrates | journal = Drug Metabolism Reviews | volume = 36 | issue = 2 | pages = 243–277 | date = May 2004 | pmid = 15237854 | doi = 10.1081/DMR-120034000 | url = https://zenodo.org/record/1236072 | access-date = 5 July 2019 | url-status = live | s2cid = 11330784 | archive-url = https://web.archive.org/web/20220629150042/https://zenodo.org/record/1236072 | archive-date = 29 June 2022 }}
- {{cite journal | vauthors = Abraham JE, Maranian MJ, Driver KE, Platte R, Kalmyrzaev B, Baynes C, Luccarini C, Shah M, Ingle S, Greenberg D, Earl HM, Dunning AM, Pharoah PD, Caldas C | title = CYP2D6 gene variants: association with breast cancer specific survival in a cohort of breast cancer patients from the United Kingdom treated with adjuvant tamoxifen | journal = Breast Cancer Research | volume = 12 | issue = 4 | pages = R64 | year = 2010 | pmid = 20731819 | pmc = 2949659 | doi = 10.1186/bcr2629 | doi-access = free }}
- {{cite journal | vauthors = Abraham JE, Maranian MJ, Driver KE, Platte R, Kalmyrzaev B, Baynes C, Luccarini C, Earl HM, Dunning AM, Pharoah PD, Caldas C | title = CYP2D6 gene variants and their association with breast cancer susceptibility | journal = Cancer Epidemiology, Biomarkers & Prevention | volume = 20 | issue = 6 | pages = 1255–1258 | date = June 2011 | pmid = 21527579 | doi = 10.1158/1055-9965.EPI-11-0321 | s2cid = 32846974 | doi-access = }}
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External links
- [http://medicine.iupui.edu/flockhart/2D6.htm#2D6sub Flockhart Lab Cyp2D6 Substrates Page] at IUPUI
- [https://web.archive.org/web/20081207081045/http://www.pharmgkb.org/search/annotatedGene/cyp2d6/index.jsp PharmGKB: Annotated PGx Gene Information for CYP2D6]
- [https://www.pharmvar.org/gene/CYP2D6 Pharmvar Gene:CYP2D6]
- {{UCSC gene info|CYP2D6}}
- {{PDBe-KB2|P10635|Cytochrome P450 2D6}}
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