OncoSignal
Live from Open Targets Platform, fetched 2026-11-11 16:14 UTC. Every row links to its source record.

IDO1 indoleamine 2,3-dioxygenase 1

ENSG00000131203 · protein coding · Open Targets profile

Catalyzes the first and rate limiting step of the catabolism of the essential amino acid tryptophan along the kynurenine pathway (PubMed:17671174, PubMed:18026683). Involved in the peripheral immune tolerance, contributing to maintain homeostasis by preventing autoimmunity or immunopathology that would result from uncontrolled and overreacting immune responses (PubMed:25691885). Tryptophan shortage inhibits T lymphocytes division and accumulation of tryptophan catabolites induces T-cell apoptosis and differentiation of regulatory T-cells (PubMed:25691885). Acts as a suppressor of anti-tumor immunity (PubMed:14502282, PubMed:23103127, PubMed:25157255, PubMed:25691885). Limits the growth of intracellular pathogens by depriving tryptophan (PubMed:25691885). Protects the fetus from maternal immune rejection (PubMed:25691885). {ECO:0000269|PubMed:14502282, ECO:0000269|PubMed:17671174, ECO:0000269|PubMed:18026683, ECO:0000303|PubMed:23103127, ECO:0000303|PubMed:25157255, ECO:0000303|PubMed:25691885}.

1 of the 2 drugs recorded against IDO1 is approved, and 1 more reached Phase 3

Each band is a group of drugs. It runs from the kind of drug on the left to the furthest stage that drug has reached in any disease on the right. Thicker bands mean more drugs.

1 small molecule drug at Approved: EPACADOSTAT1 small molecule drug at Phase 3: LINRODOSTATSmall molecule 2Approved 1Phase 3 1

Approved bands are highlighted. Withdrawn means the drug was pulled from the market or from development. A combined phase counts as the later one (Phase 1/2 is shown as Phase 2). Hover a band for the drug names. Source: Open Targets Platform, fetched live.

IDO1: inherited and tumour-mutation evidence across 15 cancers

Each row is a cancer, strongest overall evidence first. The two dots show how strong the inherited (germline) and tumour-mutation (somatic) evidence is; the line between them is the gap.

Inherited (germline) variantsMutations in tumours (somatic)
00.250.50.751melanomamelanomahead and neck squamous cell carcinomahead and neck squamous cell carcinomanon-small cell lung carcinomanon-small cell lung carcinomaurothelial carcinomaurothelial carcinomarenal cell carcinomarenal cell carcinomaglioblastomaglioblastomahepatocellular carcinomahepatocellular carcinomaovarian cancerovarian canceracute myeloid leukemiaacute myeloid leukemiaovarian carcinomaovarian carcinomadiffuse large B-cell lymphomadiffuse large B-cell lymphomacentral nervous system cancercentral nervous system canceresophageal canceresophageal cancercolorectal carcinomacolorectal carcinomaurinary bladder carcinomaurinary bladder carcinoma

Scores run from 0 (no evidence) to 1 (strongest). A missing dot at 0 means Open Targets holds no evidence of that kind. Source: Open Targets Platform, fetched live.

Tractability

Small molecule
Advanced Clinical, Structure with Ligand, High-Quality Ligand, High-Quality Pocket, Druggable Family
PROTAC
Literature, Small Molecule Binder

gnomAD loss of function constraint: o/e 0.9026100039482117 (upper bound 1.1966999769210815). Low values mean loss of function is poorly tolerated, a safety flag for inhibition.

Who runs trials of these drugs

Principal investigators and study chairs on 28 registry trials, updated in the last three years, of the most advanced drugs against IDO1 (epacadostat, linrodostat), ranked by Phase 2+ trials. Live from ClinicalTrials.gov.

15 of 27 trials of drugs against IDO1 have sites only in United States

Registry trials of epacadostat, linrodostat updated in the last three years, counted by the country group of their listed sites. A trial with sites in several groups counts in each; 15 of 27 have all sites in one country.

Sites only in this groupSites here and elsewhere
United StatesUnited States: 15 trials with sites only hereUnited States: 12 trials with sites here and elsewhere27EuropeEurope: 0 trials with sites only hereEurope: 11 trials with sites here and elsewhere11JapanJapan: 0 trials with sites only hereJapan: 6 trials with sites here and elsewhere6OtherOther: 0 trials with sites only hereOther: 9 trials with sites here and elsewhere9

Site counts are not patients per country, and trials registered only outside ClinicalTrials.gov are not covered. Where sites are is a fact about the record, not a judgement of its quality. Europe is the EU and EEA, the UK and Switzerland. 1 trials list no sites and are left out. Source: ClinicalTrials.gov, fetched live.

36 trials of drugs against IDO1 were stopped early; 2 give no reason

Terminated, withdrawn and suspended interventional trials of epacadostat, linrodostat, newest update first, live from ClinicalTrials.gov. Each reason is quoted exactly as the registry gives it; we do not sort reasons into safety, efficacy or business. Dates are the last registry update. Showing the 25 most recent of 36.

  • terminated · 2026-10-19 · Thomas Jefferson University · matched by the registry's drug synonyms
    “Study was terminated early due to toxicity concerns by the Sponsor.”
  • terminated · 2026-07-29 · Edward Kim · matched by the registry's drug synonyms
    “Funding source decision to terminate study.”
  • withdrawn · 2026-05-29 · City of Hope Medical Center · Epacadostat
    “No patients enrolled”
  • terminated · 2026-04-21 · Incyte Corporation · Epacadostat
    “Further development of this compound with ipilimumab in the treatment of melanoma is no longer being pursued.”
  • terminated · 2026-04-20 · Incyte Corporation · Epacadostat
    “Study halted prematurely and will not resume; participants are no longer being examined or receiving intervention.”
  • terminated · 2025-10-30 · Incyte Corporation · epacadostat
    “Business Decision. No safety concerns contributed to this decision.”
  • terminated · 2025-10-21 · Incyte Corporation · Epacadostat
    “Study terminated by Sponsor”
  • terminated · 2024-06-11 · Columbia University · Epacadostat
    “Study ended prematurely at the request of the funding sponsor.”
  • terminated · 2023-06-01 · Bristol-Myers Squibb · matched by the registry's drug synonyms
    “Insufficient Enrollment”
  • terminated · 2023-05-09 · Chase Heaton, MD · Epacadostat
    “Treatment Ineffective”
  • withdrawn · 2022-03-08 · City of Hope Medical Center · Epacadostat
    “Safety concerns”
  • terminated · 2022-02-28 · Incyte Corporation · Epacadostat
    “A business decision made by Incyte after analysis of data from a sister study.”
  • terminated · 2021-08-26 · Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins · Epacadostat
    “Deprioritization of drug in this patient population”
  • terminated · 2021-07-22 · Incyte Biosciences International Sàrl · Epacadostat
    “The study was terminated due to emergent data from another study and unrelated to safety.”
  • terminated · 2021-03-22 · Bristol-Myers Squibb · matched by the registry's drug synonyms
    “The standard of care for the patient population changed and we were unable to accrue any longer.”
  • withdrawn · 2021-02-26 · Fondazione IRCCS Istituto Nazionale dei Tumori, Milano · Epacadostat
    “Regolatory National Agency (AIFA) not approved”
  • withdrawn · 2020-10-26 · Alain Algazi · Epacadostat
    “Feasibility”
  • terminated · 2020-07-02 · Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins · matched by the registry's drug synonyms
    “Funding/material support withdrawn”
  • terminated · 2020-05-21 · Incyte Corporation · Epacadostat
    “Study was terminated early based on emerging data with epacadostat and pembrolizumab.”
  • withdrawn · 2020-02-05 · Dana-Farber Cancer Institute · matched by the registry's drug synonyms
    “Slow accrual”
  • terminated · 2020-01-27 · University of Chicago · Epacadostat
    “Study stopped early due to investigator conflict of interest.”
  • withdrawn · 2019-12-20 · Incyte Corporation · Epacadostat
    “Study was cancelled prior to enrolling any patients.”
  • terminated · 2019-09-25 · Incyte Corporation · Epacadostat
    No reason given
  • terminated · 2019-06-13 · Incyte Corporation · Epacadostat
    “Study halted prematurely and will not resume; participants are no longer being examined or receiving intervention.”
  • withdrawn · 2019-05-30 · M.D. Anderson Cancer Center · Epacadostat
    “Incyte (supporter of the study) is no longer going to support the study.”
Paediatric incentives and obligations for IDO1's drugs

For epacadostat, linrodostat: what EMA and FDA publish about paediatric plans, orphan status and pediatric approvals, and how many registered studies take children. Each line is a yes, no or not published fact from the record linked under it; none of it is a forecast.

Rare pediatric disease voucher. FDA, content current as of 29 Apr 2026: “As of February 3, 2026, enactment of the Consolidated Appropriations Act, 2026, the rare pediatric disease PRV program will sunset after September 30, 2029. FDA may not award any PRVs under this program after September 30, 2029.” Voucher sale prices are not shown here; they appear only as company-reported news. FDA: Rare Pediatric Disease Designation and Priority Review Voucher Programs

All 2 drugs and clinical candidates as a table

Each drug, stage and indication links to its Open Targets record, where the trials and approvals behind it are listed. Salt forms (for example a mesylate) are listed as Open Targets records them, as separate entries.

DrugTypeHighest stageIndicationsSource records
EPACADOSTATSmall moleculeapprovalneoplasm, melanoma, renal cell carcinoma, head and neck squamous cell carcinoma, non-small cell lung carcinoma, urothelial carcinoma, primary peritoneal carcinoma, malignant epithelial tumor of ovary, +29 moreOpen Targets · ChEMBL
LINRODOSTATSmall moleculephase 3melanoma, head and neck squamous cell carcinoma, non-small cell lung carcinoma, gastric adenocarcinoma, renal cell carcinoma, gastric cancer, endometrial cancer, cancer, +4 moreOpen Targets · ChEMBL