ClinicalTrials.gov is the largest public registry of clinical studies. Here is how to search it on the official site and through its API, where those tools stop, and how ClinicaLister tracks every registered trial field by field so you hear about changes instead of re-running searches.
ClinicalTrials.gov is the U.S. government registry of clinical studies, run by the National Library of Medicine. Sponsors register interventional and observational studies from around the world, and for many trials U.S. law requires registration and results reporting. Each study gets an NCT number (for example NCT06885736) that stays with it for life.
A record describes the study's design, conditions, interventions, eligibility criteria, sponsor and collaborators, locations and contacts, recruitment status, key dates and, where posted, results. Sponsors update their own records, so status, enrollment and dates change over the life of a trial.
It is the reference source for anyone tracking a therapeutic area: competitive intelligence teams following rival pipelines, medical affairs and MSLs following investigators and sites, and clinical operations teams benchmarking enrollment and timelines.
There are two official ways in: the search form on the website, and the free REST API (version 2) for bulk or automated pulls.
On clinicaltrials.gov, enter a condition or disease (for example "obesity") and, under more filters, an intervention or treatment ("tirzepatide"). The site expands many terms with synonyms, so check a few results to make sure the matches are what you meant.
Use the filters for recruitment status (Recruiting, Active not recruiting, Completed, Terminated…), study phase, study type, sponsor and location. Location search supports a distance from a city or address.
Each record shows the current registration and any posted results. The record's change history lists earlier versions so you can compare what a sponsor changed between two dates — one study at a time.
Search results can be downloaded (CSV and other formats) with the columns you choose, which is enough for a one-off landscape snapshot.
Call https://clinicaltrials.gov/api/v2/studies with parameters such as query.cond=obesity, query.intr=tirzepatide and filter.overallStatus=RECRUITING. No API key is needed. Add fields= to trim the response, countTotal=true for the total, and follow nextPageToken to page through — each page returns at most 1,000 studies. Single records come from /api/v2/studies/{NCT ID}.
ClinicaLister syncs ClinicalTrials.gov every 6 hours and records what changed between syncs, field by field, across 77 tracked fields — status, dates, enrollment, arms, outcomes, sponsors. The history starts on July 31, 2025. You see it for every trial you follow; on the Investigator plan and above, your AI assistant can query changes across the whole registry.
Changes to the trials you follow appear in the Monitoring view, classified by severity, so a suspended trial or a delayed completion date stands out. Saved queries keep adding newly matching trials and email you when they find new ones; they never silently drop a trial you follow.
Trial conditions are mapped to MONDO disease concepts, so a search for lung cancer includes NSCLC, SCLC and other subtypes without listing synonyms by hand.
Interventions are linked to FDA and EMA drug records, substances (UNII) and FDA device submissions, each link with a confidence score and its provenance. Where a study is also in the EU CTIS registry, the records are cross-referenced.
The ClinicaLister MCP server lets Claude and other assistants query the same trial data, change history and links in plain language — no API pipeline to build or maintain.
Explore a portfolio in 44 interactive charts, a site map and a configurable table, then export it — including an agent-ready workbook of cross-linked sheets.
600,000+
ClinicalTrials.gov studies
77
fields tracked for changes
Every 6 h
refresh from the official API
Jul 31, 2025
start of the change history
500,000+
trials mapped to MONDO diseases
401,000+
verified molecule–trial links
Counts measured on the ClinicaLister platform database, August–September 2026. ClinicaLister holds the full ClinicalTrials.gov registry. The change history records differences between our own syncs since July 31, 2025; it does not import ClinicalTrials.gov's earlier record versions.
Yes. The website and the API v2 are free and need no account or API key. ClinicaLister is a paid layer on top that adds change tracking, alerts and links to regulatory data.
The registry publishes updates about daily; sponsors change their own records at any time. ClinicaLister syncs every 6 hours, so a published change reaches your Monitoring view the same day.
On ClinicalTrials.gov you can compare versions of one record at a time. ClinicaLister records field-level changes since July 31, 2025, so you can review changes across everything you follow at once — for example every trial that pushed back its primary completion date this month.
It is the official REST API at clinicaltrials.gov/api/v2. The /studies endpoint takes query parameters such as query.cond, query.intr and filter.overallStatus, returns JSON or CSV, and pages through results with a token, up to 1,000 studies per page. It returns the current version of each record only.
Yes. Studies from many countries are registered there, but not every trial is. European trials authorised under the EU Clinical Trials Regulation are registered in CTIS, which ClinicaLister cross-references where a trial appears in both.
See every change to the trials you follow, in one place
Built for the Competitive Intelligence Analyst. See it in the product: Searching Trials. All data sources