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}.
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.
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 Withdrawn means the drug was pulled from the market or from development.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.
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.
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.
- Mark JonesIncyte Corporation · 5 of 5 trials Phase 2+Ph3NCT03358472 · Pembrolizumab Plus Epacadostat, Pembrolizumab Monotherapy, and the EXTREME Regimen in Recurrent or Metastatic Head and Neck Squamous Cell Carcinoma (KEYNOTE-669/ECHO-304)brief
- Lance LeopoldIncyte Corporation · 3 of 3 trials Phase 2+Ph1/Ph2NCT01604889 · A Phase 1/2 Randomized, Blinded, Placebo Controlled Study of Ipilimumab in Combination With Epacadostat or Placebo in Subjects With Unresectable or Metastatic Melanomabrief
- Adam LuginbuhlSidney Kimmel Comprehensive Cancer Center at Thomas Jefferson University · 1 of 1 trials Phase 2+
- Chrisann KyiMemorial Sloan Kettering Cancer Center · 1 of 1 trials Phase 2+
- Diane HershockIncyte Corporation · 1 of 1 trials Phase 2+
- Dung LeThe Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins · 1 of 1 trials Phase 2+
- George A FisherStanford University · 1 of 1 trials Phase 2+
- Jacob SandsDana-Farber Cancer Institute · 1 of 1 trials Phase 2+
- James L GulleyNational Cancer Institute (NCI) · 1 of 1 trials Phase 2+
- Kevin O'HayerIncyte Corporation · 1 of 1 trials Phase 2+
- Lilian T GienNRG Oncology · 1 of 1 trials Phase 2+
- Mark CornfieldIncyte Corporation · 1 of 1 trials Phase 2+
- Milan ChhedaWashington University School of Medicine · 1 of 1 trials Phase 2+
- Moh'd KhusmanWashington University School of Medicine · 1 of 1 trials Phase 2+
- Ravi SalgiaCity of Hope Medical Center · 1 of 1 trials Phase 2+
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.
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 · EpacadostatNo 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.
- FDA pediatric target list: yes · IDO1 is on the list. Membership alone neither requires nor waives a pediatric study.Rule: Target is on FDA's Pediatric Molecular Target List (relevant targets). Source: FDA Pediatric Molecular Target List (Listed as February 2026 on the FDA Pediatric Oncology page; the file served is 9.7.22_the_relevant_molecular_target_list.xlsx, whose Summary of Changes sheet is headed 'SEPTEMBER 2022 UPDATE' (footnote date 2022-09-01)), 2026-11-11
- EU paediatric investigation plan: no · No EMA paediatric investigation plan decision names epacadostat, linrodostatRule: An EMA PIP decision (agreement, modification or waiver) lists the drug as its active substance, exact name. Source: EMA data download (dated snapshot), 2026-11-11
- EU orphan designation: no · No EU orphan designation names epacadostat, linrodostatRule: An EU orphan designation lists the drug as its active substance (exact name) or belongs to a medicine that does; withdrawn and expired designations are listed with their status. Source: EMA data download (dated snapshot), 2026-11-11
- Authorised in the EU: no · EMA lists no centrally authorised medicine of epacadostat, linrodostatRule: An EMA medicine record lists the drug as its active substance or INN, exact name; national-only authorisations are not in this file. Source: EMA data download (dated snapshot), 2026-11-11
- FDA orphan designation: not published · FDA's orphan designation database turns away automated requests, so this app does not read it; search it by hand at the linkRule: Would be: an FDA orphan designation names the drug. Source: FDA orphan designations search
- FDA pediatric oncology approval: no · FDA's table lists no pediatric approval of epacadostat, linrodostatRule: FDA's Pediatric Oncology Drug Approvals table names the drug. Source: FDA Pediatric Oncology Drug Approvals (content current as of 2026-03-03), 2026-11-11
- Registered studies open to children: yes · 1 interventional studies of epacadostat, linrodostat include patients under 18; 0 are recruiting, not yet recruiting or activeRule: The registry's age group includes Child (birth to 17 years), which also counts studies that set no minimum age. Source: ClinicalTrials.gov search, 2026-11-11
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.
| Drug | Type | Highest stage | Indications | Source records |
|---|---|---|---|---|
| EPACADOSTAT | Small molecule | approval | neoplasm, 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 more | Open Targets · ChEMBL |
| LINRODOSTAT | Small molecule | phase 3 | melanoma, head and neck squamous cell carcinoma, non-small cell lung carcinoma, gastric adenocarcinoma, renal cell carcinoma, gastric cancer, endometrial cancer, cancer, +4 more | Open Targets · ChEMBL |