{"entity":{"id":"htr3a","kind":"target","name":"5-HT3 receptor (HTR3A)","aka":[],"tldr":"The serotonin receptor on the gut's vagus nerve endings and in the brainstem vomiting centre that chemotherapy triggers. Ondansetron and palonosetron block it, the foundation of modern anti-sickness treatment.","summary":"Chemotherapy damages enterochromaffin cells in the gut lining, releasing serotonin that activates 5-HT3 receptors on vagal afferents and in the area postrema to provoke acute vomiting. 5-HT3 antagonists, first ondansetron in 1991 and later granisetron and the long-acting palonosetron, block this pathway and transformed the experience of cisplatin-based and anthracycline-based chemotherapy. They are combined with an NK1 antagonist and dexamethasone for highly emetogenic regimens; constipation, headache and QT prolongation are the main side effects.","asOf":"2026-09-04","wikipedia":"https://en.wikipedia.org/wiki/5-HT3_receptor","links":[{"label":"UniProt P46098: HTR3A","url":"https://www.uniprot.org/uniprotkb/P46098/entry"}],"tags":[],"related":["tacr1"],"cancers":[],"sections":[],"technologies":[],"targets":[],"drugs":["ondansetron","palonosetron","granisetron","dolasetron"],"companies":[],"institutions":[],"pathways":[],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":[],"symbol":"HTR3A","role":[],"sources":[],"specificity":"tumour-associated","distribution":"not-established","specificityNote":"Tumour-associated overexpression: HPA finds the RNA cancer enhanced in cancer (Ovary Serous Cystadenocarcinoma (TCGA)) and group enriched in normal brain, intestine, lymphoid tissue, pancreas, so the tumour and the normal tissue it comes from share the target and the medicine relies on the difference in level. HPA HTR3A: RNA group enriched (brain 2 nTPM, intestine 2 nTPM, lymphoid tissue 8 nTPM); blood lineage group enriched (B-cells 14 nTPM, dendritic cells 12 nTPM); no normal tissue stained high. 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 HTR3A tissue","url":"https://www.proteinatlas.org/ENSG00000166736-HTR3A/tissue","note":"RNA tissue and blood lineage specificity, normal tissue antibody staining (version 25.1, CC BY-SA 3.0)"},{"label":"Human Protein Atlas HTR3A pathology","url":"https://www.proteinatlas.org/ENSG00000166736-HTR3A/pathology","note":"patients per staining level per cancer type (version 25.1, CC BY-SA 3.0)"},{"label":"Open Targets ENSG00000166736 associations","url":"https://platform.opentargets.org/target/ENSG00000166736/associations","note":"cancer associations at or above 0.5 (CC0)"}],"hgnc":"HGNC:5297","ensembl":"ENSG00000166736","uniprot":"P46098","entrez":"3359","firstDescribed":1995,"firstDescribedBasis":"sequence","firstDescribedNote":"Earliest sequence paper UniProt cites for the protein: Miyake et al, Mol. Pharmacol, 1995, \"Molecular cloning of human 5-hydroxytryptamine3 receptor: heterogeneity in distribution and function among species\".","firstDescribedSource":"https://pubmed.ncbi.nlm.nih.gov/7565620/","biology":"Ligand-gated ion channel for serotonin on vagal afferents and in the brainstem chemoreceptor trigger zone; blocked by setron antiemetics.","whereFound":["Supportive care: prevention of chemotherapy-induced nausea and vomiting"],"targetClass":"other","prevalence":[{"cancerId":"metastatic-cancer","pct":"host","measure":"Host target: serotonin receptor on gut vagal endings and the vomiting centre. Not a tumour alteration, so no prevalence applies; the drug acts on normal tissue or on symptoms."}]},"route":"/targets/htr3a/","neighbours":{"target":[{"id":"cnr1","kind":"target","name":"Cannabinoid receptor 1","route":"/targets/cnr1/"},{"id":"tacr1","kind":"target","name":"NK1 receptor (TACR1)","route":"/targets/tacr1/"}],"drug":[{"id":"dolasetron","kind":"drug","name":"Dolasetron","route":"/drugs/dolasetron/"},{"id":"granisetron","kind":"drug","name":"Granisetron","route":"/drugs/granisetron/"},{"id":"ondansetron","kind":"drug","name":"Ondansetron","route":"/drugs/ondansetron/"},{"id":"palonosetron","kind":"drug","name":"Palonosetron","route":"/drugs/palonosetron/"}]}}