Query clinicaltrials.gov:

• Get total number of subjects for some sponsor, location, and study status.
• Get number of studies for some sponsor, location, study type, and study status.

See the documentation:

• https://www.clinicaltrials.gov/api/
• https://www.clinicaltrials.gov/api/gui/ref/crosswalks

Example query as URL:

https://www.clinicaltrials.gov/api/query/field_values?expr=SEARCH%5BLocation%5D%28AREA%5BLocationFacility%5DNIH+Clinical+Center%29&field=EnrollmentCount&fmt=json

Equivalent to: SEARCH[Location](AREA[LocationFacility]NIH Clinical Center)

Query Field Values:

• Name of the sponsor: LeadSponsorName (e.g. "NINDS")
• Study status: OverallStatus (e.g. "Completed")
• Facility name: LocationFacility (e.g. "NIH Clinical Center")
• Study type: StudyType (e.g. "Interventional", "Observational")

Field:

• Number of Participants Analyzed: EnrollmentCount