{"entity":{"id":"oprm1","kind":"target","name":"Mu-opioid receptor","aka":[],"tldr":"The mu-opioid receptor is the target of morphine and the other strong opioids that control most severe cancer pain; the same receptor in the gut causes opioid constipation, which methylnaltrexone and naloxegol relieve by blocking it outside the brain.","summary":"Mu-opioid receptors in the spinal cord and brain mediate the pain relief of morphine, oxycodone, fentanyl and methadone, which remain the mainstay of the WHO analgesic ladder for moderate to severe cancer pain. The same receptors in the intestinal wall slow gut movement, so opioid-induced constipation affects most patients on long-term opioids; peripherally acting antagonists such as methylnaltrexone, naloxegol and naldemedine block gut receptors without reaching the brain, and methylnaltrexone is approved specifically for opioid-induced constipation in advanced illness. Whether opioids influence tumour growth or recurrence through receptors on cancer cells is an open research question.","asOf":"2026-09-04","wikipedia":"https://en.wikipedia.org/wiki/Μ-opioid_receptor","links":[{"label":"UniProt P35372: OPRM1","url":"https://www.uniprot.org/uniprotkb/P35372/entry"},{"label":"HGNC:8156 OPRM1","url":"https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:8156"},{"label":"ChEMBL target CHEMBL233","url":"https://www.ebi.ac.uk/chembl/explore/target/CHEMBL233"}],"tags":["chembl-gap"],"related":[],"cancers":[],"sections":[],"technologies":[],"targets":[],"drugs":["methylnaltrexone"],"companies":[],"institutions":[],"pathways":[],"terms":["palliative-care"],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"symbol":"OPRM1","role":[],"sources":[],"specificity":"tumour-associated","distribution":"not-established","specificityNote":"Tumour-associated overexpression: HPA finds the RNA tissue enhanced in normal brain, testis, so the tumour and the normal tissue it comes from share the target and the medicine relies on the difference in level. HPA OPRM1: RNA tissue enhanced (brain 4 nTPM, testis 3 nTPM); high antibody staining in 1 normal tissue. Distribution: no corpus cancer carries a prevalence row, threshold or catalogue link for it; Open Targets associates it with 0 specific cancer types at or above 0.5. (Rule 7 of scripts/fetch-target-specificity.ts.)","specificitySources":[{"label":"Human Protein Atlas OPRM1 tissue","url":"https://www.proteinatlas.org/ENSG00000112038-OPRM1/tissue","note":"RNA tissue and blood lineage specificity, normal tissue antibody staining (version 25.1, CC BY-SA 3.0)"},{"label":"Human Protein Atlas OPRM1 pathology","url":"https://www.proteinatlas.org/ENSG00000112038-OPRM1/pathology","note":"patients per staining level per cancer type (version 25.1, CC BY-SA 3.0)"},{"label":"Open Targets ENSG00000112038 associations","url":"https://platform.opentargets.org/target/ENSG00000112038/associations","note":"cancer associations at or above 0.5 (CC0)"}],"hgnc":"HGNC:8156","ensembl":"ENSG00000112038","uniprot":"P35372","entrez":"4988","firstDescribed":1994,"firstDescribedBasis":"sequence","firstDescribedNote":"Earliest sequence paper UniProt cites for the protein: Wang J.-B. et al, FEBS Lett, 1994, \"Human mu opiate receptor. cDNA and genomic clones, pharmacologic characterization and chromosomal assignment\".","firstDescribedSource":"https://pubmed.ncbi.nlm.nih.gov/7905839/","biology":"A Gi-coupled G-protein-coupled receptor that closes calcium channels and opens potassium channels in neurons, reducing neurotransmitter release; densely expressed in dorsal horn, periaqueductal grey and enteric neurons.","whereFound":["Central and enteric nervous system","Expressed on some tumour cells; significance under study"],"targetClass":"other","prevalence":[{"cancerId":"metastatic-cancer","pct":"host","measure":"Host target: mu-opioid receptor in pain pathways and gut. Not a tumour alteration, so no prevalence applies; the drug acts on normal tissue or on symptoms."}]},"route":"/targets/oprm1/","neighbours":{"drug":[{"id":"fentanyl","kind":"drug","name":"Fentanyl (transmucosal, for breakthrough cancer pain)","route":"/drugs/fentanyl/"},{"id":"methylnaltrexone","kind":"drug","name":"Methylnaltrexone","route":"/drugs/methylnaltrexone/"}],"technology":[{"id":"palliative-care","kind":"technology","name":"Early integrated palliative care","route":"/technologies/palliative-care/"}]}}