---
title: "Search ClinicalTrials.gov - every registered US (and many..."
method: GET
path: "/api/clinical/trial-search"
tags: ["clinical"]
---

# Search ClinicalTrials.gov - every registered US (and many...

`GET /api/clinical/trial-search`

## Request

- Base URL: `https://2s.io`
- URL: `https://2s.io/api/clinical/trial-search`
- Auth: API key in header `PAYMENT-SIGNATURE`

Search ClinicalTrials.gov — every registered US (and many international) clinical study (~500k trials). Free-text query matches title + condition + intervention; or direct lookup by NCT ID. Optional filters: recruitment status, lead sponsor, phase (PHASE1..PHASE4), country. Each record includes NCT ID, brief + official title, status, phases, study type, conditions list, interventions (with type + name), enrollment count + type, key dates (start / primary completion / completion / first posted / last update), lead sponsor + class (INDUSTRY/NIH/OTHER), hasResults flag, brief summary, and canonical clinicaltrials.gov URL. Public-domain NIH NLM data.

## Query parameters

- `query` string
- `nctId` string
- `status` 'RECRUITING' | 'ACTIVE_NOT_RECRUITING' | 'COMPLETED' | 'TERMINATED' | 'WITHDRAWN' | 'NOT_YET_RECRUITING' | 'SUSPENDED'
- `sponsor` string
- `phase` string
- `country` string
- `pageSize` integer
- `pageToken` string
- `trial` 1

## Other responses

- `200` (unresolved $ref)
- `400`: Invalid request — not charged. error.code: BAD_REQUEST or INVALID_PARAM (parameter validation; error.details.issues lists each problem), MALFORMED_JSON, or a request-specific code. Other client errors: 405 METHOD_NOT_ALLOWED (wrong verb; see the Allow header), 413 PAYLOAD_TOO_LARGE.
- `402`: Payment required. Body is the x402 PaymentRequirements envelope with a multi-network accepts array; the per-call price is in accepts[].amount (and on the operation as x-2s-price). Sign for whichever rail you hold USDC on (EIP-3009 for Base, partial SPL transfer for Solana) and retry with the PAYMENT-SIGNATURE header (X-PAYMENT also accepted for v1 clients). Also PAYMENT_SETTLE_FAILED (error envelope) when a verified payment failed to settle: error.details.chargeStatus is "not_charged" (retry with a fresh payment) or "unknown" (the authorization may still settle before its deadline — check it before retrying).
- `429`: Too many requests — RATE_LIMITED: our per-IP / per-payer limiter. Not charged; retry after Retry-After.
- `5XX`: Server-side failure. 500 INTERNAL: unexpected error; quote error.errorId (also the X-2s-Error-Id header). 502 UPSTREAM_UNAVAILABLE (or another UPSTREAM_* code): the data provider failed — composite endpoints refuse unbilled when every source fails. 503 SERVICE_PAUSED: endpoint paused by the operator kill switch, retry after Retry-After; 503 SPEND_CAP: daily upstream budget exhausted. 504 UPSTREAM_TIMEOUT. Not charged.

---

[API](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api.md) · [All operations](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/llms.txt) · [OpenAPI document](https://skmtc.dev/2s-io/apis/2s-the-most-everything-api/revisions/da4c5caf686e?raw)