Open Targets Platform API

Base URLs

GraphQL API (primary, recommended):

https://api.platform.opentargets.org/api/v4/graphql

Important: The GraphQL endpoint requires HTTP POST with Content-Type: application/json. WebFetch (GET-only) will not work — use curl via shell instead:

curl -s -X POST -H "Content-Type: application/json" \\
  -d '{"query":"{ target(ensemblId: \\"ENSG00000157764\\") { approvedSymbol approvedName } }"}' \\
  https://api.platform.opentargets.org/api/v4/graphql

REST API (simpler queries):

https://api.platform.opentargets.org/api/v4

Authentication

No API key required. All endpoints are public.

GraphQL API

All GraphQL queries are sent as POST requests to the GraphQL endpoint.

POST https://api.platform.opentargets.org/api/v4/graphql
Content-Type: application/json

{
  "query": "...",
  "variables": { ... }
}

1. Target information (by Ensembl Gene ID)

query TargetInfo($ensemblId: String!) {
  target(ensemblId: $ensemblId) {
    id
    approvedSymbol
    approvedName
    biotype
    proteinIds {
      id
      source
    }
    tractability {
      label
      modality
      value
    }
    safetyLiabilities {
      event
      effects {
        direction
        dosing
      }
    }
    pathways {
      pathway
      pathwayId
    }
    functionDescriptions
    subcellularLocations {
      location
    }
  }
}

Variables: { "ensemblId": "ENSG00000141510" }

Example as URL (GET also supported for simple queries):

https://api.platform.opentargets.org/api/v4/graphql?query={target(ensemblId:"ENSG00000141510"){id approvedSymbol approvedName biotype functionDescriptions}}

---

2. Disease information (by EFO ID)

query DiseaseInfo($efoId: String!) {
  disease(efoId: $efoId) {
    id
    name
    description
    therapeuticAreas {
      id
      name
    }
    synonyms {
      terms
    }
  }
}

Variables: { "efoId": "EFO_0000311" } (cancer)

Example as URL:

https://api.platform.opentargets.org/api/v4/graphql?query={disease(efoId:"EFO_0000311"){id name description therapeuticAreas{id name}}}

---

3. Target-Disease associations

query Associations($ensemblId: String!, $page: Pagination!) {
  target(ensemblId: $ensemblId) {
    approvedSymbol
    associatedDiseases(page: $page) {
      count
      rows {
        disease {
          id
          name
        }
        score
        datasourceScores {
          id
          score
        }
      }
    }
  }
}

Variables:

{
  "ensemblId": "ENSG00000141510",
  "page": { "index": 0, "size": 10 }
}

Example as URL:

https://api.platform.opentargets.org/api/v4/graphql?query={target(ensemblId:"ENSG00000141510"){approvedSymbol associatedDiseases(page:{index:0,size:5}){count rows{disease{id name}score}}}}

---

4. Disease-Target associations (from disease side)

query DiseaseAssociations($efoId: String!, $page: Pagination!) {
  disease(efoId: $efoId) {
    name
    associatedTargets(page: $page) {
      count
      rows {
        target {
          id
          approvedSymbol
        }
        score
        datasourceScores {
          id
          score
        }
      }
    }
  }
}

Variables:

{
  "efoId": "EFO_0000311",
  "page": { "index": 0, "size": 10 }
}

---

5. Evidence for a target-disease pair

query Evidence($ensemblId: String!, $efoId: String!, $size: Int!) {
  disease(efoId: $efoId) {
    evidences(ensemblIds: [$ensemblId], size: $size) {
      count
      rows {
        id
        score
        datasourceId
        datatypeId
        literature
        diseaseFromSource
        targetFromSourceId
        resourceScore
        urls {
          niceName
          url
        }
      }
    }
  }
}

Variables:

{
  "ensemblId": "ENSG00000141510",
  "efoId": "EFO_0000311",
  "size": 10
}

---

6. Drug/molecule information

query DrugInfo($chemblId: String!) {
  drug(chemblId: $chemblId) {
    id
    name
    drugType
    maximumClinicalTrialPhase
    hasBeenWithdrawn
    mechanismsOfAction {
      rows {
        mechanismOfAction
        targets {
          id
          approvedSymbol
        }
      }
    }
    indications {
      rows {
        disease {
          id
          name
        }
        maxPhaseForIndication
      }
    }
    linkedDiseases {
      count
      rows {
        id
        name
      }
    }
    linkedTargets {
      count
      rows {
        id
        approvedSymbol
      }
    }
  }
}

Variables: { "chemblId": "CHEMBL25" } (aspirin)

Example as URL:

https://api.platform.opentargets.org/api/v4/graphql?query={drug(chemblId:"CHEMBL25"){id name drugType maximumClinicalTrialPhase mechanismsOfAction{rows{mechanismOfAction targets{id approvedSymbol}}}}}

---

7. Search across targets, diseases, and drugs

query Search($queryString: String!, $entityNames: [String!], $page: Pagination!) {
  search(queryString: $queryString, entityNames: $entityNames, page: $page) {
    total
    hits {
      id
      entity
      name
      description
      score
    }
  }
}

Variables:

{
  "queryString": "BRAF melanoma",
  "entityNames": ["target", "disease", "drug"],
  "page": { "index": 0, "size": 10 }
}

Example as URL:

https://api.platform.opentargets.org/api/v4/graphql?query={search(queryString:"BRAF",entityNames:["target"],page:{index:0,size:5}){total hits{id entity name description}}}

---

8. Known drugs for a target

query KnownDrugs($ensemblId: String!, $size: Int!) {
  target(ensemblId: $ensemblId) {
    approvedSymbol
    knownDrugs(size: $size) {
      count
      rows {
        drug {
          id
          name
          drugType
          maximumClinicalTrialPhase
        }
        disease {
          id
          name
        }
        phase
        status
        mechanismOfAction
        urls {
          niceName
          url
        }
      }
    }
  }
}

Variables:

{
  "ensemblId": "ENSG00000157764",
  "size": 10
}

(ENSG00000157764 = BRAF)

---

9. Tractability (druggability)

Included in the target query (see endpoint 1 above). Modalities include:

• SM (small molecule)
• AB (antibody)
• PR (PROTAC)
• OC (other clinical)

---

REST API Endpoints

These are simpler alternatives for common operations.

Search

GET /api/v4/search?q={query}&page=0&size=10

Example:

https://api.platform.opentargets.org/api/v4/search?q=TP53&size=5

Response:

{
  "total": 15,
  "data": [
    {
      "id": "ENSG00000141510",
      "entity": "target",
      "name": "TP53",
      "description": "Cellular tumor antigen p53",
      "score": 142.5
    }
  ]
}

---

Key Identifiers

Datasource IDs (for filtering evidence)

• ot_genetics_portal -- Open Targets Genetics
• eva -- ClinVar (via EVA)
• cancer_gene_census -- COSMIC Cancer Gene Census
• chembl -- ChEMBL (clinical trials)
• europepmc -- Literature mining
• expression_atlas -- Expression Atlas
• gene2phenotype -- Gene2Phenotype
• genomics_england -- Genomics England PanelApp
• intogen -- IntOGen (cancer drivers)
• ot_crispr -- Open Targets CRISPR screens
• progeny -- PROGENy (pathway activity)
• reactome -- Reactome pathways
• slapenrich -- SLAPenrich
• sysbio -- Systems biology
• uniprot_literature -- UniProt literature

Pagination

GraphQL uses page: { index: Int, size: Int } (0-based index). REST uses page and size query parameters.

Rate Limits

• No API key required.
• Fair-use rate limiting applies. No hard published limit.
• For bulk data, use the Open Targets data downloads (Parquet files on GCS/FTP) rather than API.
• Respect HTTP 429 and Retry-After headers.

Error Format

GraphQL errors:

{
  "errors": [
    {
      "message": "Variable '$ensemblId' expected value of type 'String!' but got: null",
      "locations": [{"line": 1, "column": 7}]
    }
  ]
}

REST errors return appropriate HTTP status codes with JSON error bodies.

Tips

• Use the GraphQL API for maximum flexibility -- request only the fields you need.
• The GET method for GraphQL works for simple queries but POST is required for complex ones with variables.
• Combine target + disease queries to get association scores with evidence breakdown.
• Use datasourceScores in association queries to see which evidence sources contribute most.
• The Open Targets Platform web UI at https://platform.opentargets.org has a GraphQL playground for testing queries.