{"entity":{"id":"ido1","kind":"target","name":"IDO1","aka":["IDO","INDO","indoleamine 2,3-dioxygenase 1"],"tldr":"IDO1 is an enzyme tumours use to burn up tryptophan, starving T cells and producing by-products that switch them off. Epacadostat blocked it but its programme ended in failure; the IO102-IO103 vaccine instead teaches T cells to attack the IDO1-expressing cells themselves.","summary":"IDO1 (chromosome 8p11.21) catalyses the first, rate-limiting step of tryptophan catabolism along the kynurenine pathway; the tryptophan shortage stops T lymphocytes dividing and the catabolites induce T-cell apoptosis and regulatory T-cell differentiation, so the enzyme maintains peripheral tolerance, protects the fetus from maternal rejection, limits intracellular pathogens and suppresses anti-tumour immunity (UniProt P14902). In OnCo, IDO1 is the target of epacadostat, a selective reversible enzyme inhibitor recorded as a negative programme in melanoma, and one of the two antigens (with PD-L1) of the IO102-IO103 peptide vaccine in phase 3 for melanoma and head and neck cancer.","asOf":"2026-09-22","links":[{"label":"HGNC HGNC:6059","url":"https://www.genenames.org/data/gene-symbol-report/#!/hgnc_id/HGNC:6059"},{"label":"UniProt P14902","url":"https://www.uniprot.org/uniprotkb/P14902/entry"},{"label":"NCBI Gene 3620","url":"https://www.ncbi.nlm.nih.gov/gene/3620"}],"tags":["wave5-target"],"related":["pdl1"],"cancers":["melanoma","head-and-neck"],"sections":[],"technologies":["checkpoint-inhibitor"],"targets":[],"drugs":["epacadostat","io102-io103"],"companies":[],"institutions":[],"pathways":["nutrient-competition-tme","immune-desert-exclusion","cancer-immunity-cycle"],"terms":[],"trials":[],"people":[],"bottlenecks":[],"keyPapers":[],"journals":[],"dependsOn":[],"notes":["Prevalence not recorded in this wave: HGNC and UniProt carry no positivity rates and no other source was consulted."],"provenance":{"editedBy":"OnCo content wave 5 (HGNC REST, UniProt REST, corpus drug and pathway records)","editedOn":"2026-09-22"},"symbol":"IDO1","hgnc":"HGNC:6059","ensembl":"ENSG00000131203","uniprot":"P14902","entrez":"3620","biology":"The two corpus approaches differ in kind: epacadostat blocked the enzyme's chemistry, while IO102-IO103 raises T cells against cells that express IDO1 or PD-L1 in the tumour microenvironment, turning the suppressive cells themselves into targets.","whereFound":["Tumour cells and myeloid cells of the tumour microenvironment","Melanoma and head and neck cancer (IO102-IO103); melanoma (epacadostat)"],"targetClass":"enzyme","prevalence":[]},"route":"/targets/ido1/","neighbours":{"target":[{"id":"pdl1","kind":"target","name":"PD-L1","route":"/targets/pdl1/"}],"cancer":[{"id":"head-and-neck","kind":"cancer","name":"Head and neck squamous cell carcinoma","route":"/cancers/head-and-neck/"},{"id":"melanoma","kind":"cancer","name":"Melanoma","route":"/cancers/melanoma/"}],"technology":[{"id":"checkpoint-inhibitor","kind":"technology","name":"Immune checkpoint inhibitors","route":"/technologies/checkpoint-inhibitor/"}],"drug":[{"id":"epacadostat","kind":"drug","name":"Epacadostat","route":"/drugs/epacadostat/"},{"id":"io102-io103","kind":"drug","name":"IO102-IO103","route":"/drugs/io102-io103/"}],"pathway":[{"id":"immune-desert-exclusion","kind":"pathway","name":"Cold tumours: immune deserts and exclusion","route":"/pathways/immune-desert-exclusion/"},{"id":"nutrient-competition-tme","kind":"pathway","name":"Nutrient competition & metabolic immunosuppression","route":"/pathways/nutrient-competition-tme/"},{"id":"cancer-immunity-cycle","kind":"pathway","name":"The cancer-immunity cycle","route":"/pathways/cancer-immunity-cycle/"}]}}