PubTator3

NCBI text-mined annotations on PubMed abstracts (and some PMC full text): genes, diseases, chemicals, species, variants, and cell lines, plus typed relations. Use it when the user wants entities in a paper or papers that mention a normalized entity (@CHEMICAL_remdesivir), not when they want a citation list.

Europe PMC has a separate Annotations API. PubMed search does not normalize "remdesivir" to a concept ID. PubTator3 APIs are not the old PubTator / CBBresearch endpoints.

All figures below verified 2026-09-10.

Base URL

https://www.ncbi.nlm.nih.gov/research/pubtator3-api

Docs: https://www.ncbi.nlm.nih.gov/research/pubtator3/api

Authentication

None.

Rate Limits

No more than 3 requests per second. Serialize. For bulk annotation dumps use the FTP site (https://ftp.ncbi.nlm.nih.gov/pub/lu/PubTator3/) rather than the API.

Key Endpoints

1. Resolve a mention to an entity ID

GET /entity/autocomplete/?query={text}&concept={type}&limit={n}

concept is optional (chemical, disease, gene, species, variant, cellline).

GET /entity/autocomplete/?query=remdesivir&limit=3

Returns a JSON array. First hit (verified):

{
  "_id": "@CHEMICAL_remdesivir",
  "biotype": "chemical",
  "db_id": "C000606551",
  "db": "ncbi_mesh",
  "name": "remdesivir"
}

Search with _id (@CHEMICAL_remdesivir), not the display name. Nearby synonyms (@CHEMICAL_GS_441524_triphosphate) are different entities.

2. Search papers by text, entity, or relation

GET /search/?text={query}&page={n}

text may be free text, an @TYPE_name entity ID, a boolean combination, or a relation:

@CHEMICAL_Doxorubicin AND @DISEASE_Neoplasms
relations:ANY|@CHEMICAL_Doxorubicin|@DISEASE_Neoplasms
relations:ANY|@CHEMICAL_Doxorubicin|DISEASE

GET /search/?text=@CHEMICAL_remdesivir

Verified: count 23295, page_size 10, current 1, total_pages 2330, results length 10. First result pmid is an integer (37711410); _id is a string. Page with page (1-based). There is no cursor.

Do not use this as a general PubMed replacement. Rank is entity-centric.

3. Export annotations for PMIDs

GET /publications/export/{format}?pmids={id,id}&full={true|false}

format is pubtator, biocxml, or biocjson. full=true (PMC full text) works only for biocxml / biocjson.

GET /publications/export/biocjson?pmids=29355051

The JSON is not a bare BioC document. It is:

{ "PubTator3": [ { "_id": "29355051|None", "id": "29355051", "passages": [...], "relations": [...] } ] }

Verified on PMID 29355051: one document, two passages, first passage has 5 annotations. An annotation looks like:

{
  "infons": {
    "type": "Species",
    "database": "ncbi_taxonomy",
    "normalized_id": 112863,
    "biotype": "species"
  },
  "text": "Lycium barbarum",
  "locations": [{"offset": 14, "length": 15}]
}

Read PubTator3[0].passages[].annotations. A 200 with "PubTator3": [] is "no documents," not a transport success you can ignore.

4. Related entities

GET /relations?e1={entityId}&type={relation}&e2={entity_type}

Relation types include treat, cause, interact, associate, positive_correlate, negative_correlate, prevent, inhibit, stimulate, drug_interact, cotreat, convert, and compare. e1 must be an autocomplete _id; type and e2 are optional. Related entity types include gene, disease, chemical, and variant.

Typical Workflow

1. Autocomplete the user's string → @CHEMICAL_… / @DISEASE_….
2. Search with that ID (and a relation if they asked "what does X treat?").
3. Export biocjson for the PMIDs you will report, and list the annotations.
4. For the paper itself (abstract, OA PDF), go to PubMed / Europe PMC / Unpaywall. PubTator full-text annotations cover a subset; check returned passages before claiming full-text coverage.

Failure Modes

Official sources reviewed 2026-09-30

• https://www.ncbi.nlm.nih.gov/research/pubtator3/api