Clinical Trial Search API: Trials by condition, sponsor, intervention or status as flat records — ClinicalTrials.gov

Name: Clinical Trial Search API: Trials by condition, sponsor, intervention or status as flat records — ClinicalTrials.gov
Creator: AnswerPool
License: https://www.usa.gov/government-works

Trials by condition, sponsor, intervention or status as flat records: phase, status, sponsor, enrollment and dates. Skips the registry's nested protocol modules. Free.

Free — no key, no signup, rate-limited to 60 calls per minute per client.

How do you call it?

GET /v1/trials/search — product id trials_search. Over MCP, call answerpool_get with product_id=trials_search.

curl "https://answerpool.io/v1/trials/search?condition=melanoma"

Live call: https://answerpool.io/v1/trials/search?condition=melanoma · JSON sample: /v1/samples/trials_search

What does the answer look like?

A representative response, the same static sample served at /v1/samples/trials_search.

`as_of`	2026-09-03T16:00:00Z
`query.query.cond`	melanoma
`count`	1
`source`	Source: National Library of Medicine (ClinicalTrials.gov)
`refresh_after`	2026-09-18T00:00:00.000Z

`trials`

nct_id	title	status	phases	study_type	lead_sponsor	enrollment	start_date	completion_date	conditions	url
NCT06131398	A Study of AMG 355 Alone and in Combination With Pembrolizumab	COMPLETED	PHASE1	INTERVENTIONAL	Amgen	120	2024-03-07	2026-02-01	Advanced Solid Tumors	https://clinicaltrials.gov/study/NCT06131398

The same sample as raw JSON

{
 "as_of": "2026-09-03T16:00:00Z",
 "query": {
  "query.cond": "melanoma"
 },
 "count": 1,
 "trials": [
  {
   "nct_id": "NCT06131398",
   "title": "A Study of AMG 355 Alone and in Combination With Pembrolizumab",
   "status": "COMPLETED",
   "phases": [
    "PHASE1"
   ],
   "study_type": "INTERVENTIONAL",
   "lead_sponsor": "Amgen",
   "enrollment": 120,
   "start_date": "2024-03-07",
   "completion_date": "2026-02-01",
   "conditions": [
    "Advanced Solid Tumors"
   ],
   "url": "https://clinicaltrials.gov/study/NCT06131398"
  }
 ],
 "source": "Source: National Library of Medicine (ClinicalTrials.gov)",
 "refresh_after": "2026-09-18T00:00:00.000Z"
}

How fresh is it, and where does the data come from?

The fastest source behind this answer can change daily, so every response carries a refresh_after timestamp — right now it would be 2026-09-18T00:00:00.000Z. Schedule the next call on that value rather than on a guess.

ClinicalTrials.gov (NIH National Library of Medicine) (US federal public domain) — upstream: https://clinicaltrials.gov/api/v2

Method version 0.1.0 · serving cache 1 day · every response carries a result_id you can resolve at /v1/provenance.

When should you use it?

You need the trials themselves in a flat, reasoned-over shape.

What you skip building

protocolSection nesting
per-module field digging

When should you not use it?

The pipeline shape across many trials — /v1/trials/pipeline.

Where else can you find this?

Catalog entry (JSON, free)
OpenAPI schema — input and output types, prices, the 402 flow
llms.txt — every product in one plain-text document