Experimental drug is a new or newly discovered drug (medicine) that is still being developed.
Marketed drug is a medicine that is already registered with the local regulatory authority (MCC) for use for specific diseases. This medicine has gone beyond the developmental stage and its quality, safety and effectiveness are already known. Marketed drugs are also referred to as licensed drugs or registered drugs.
Investigational product refers to a medicine/s, vaccine/s or medical device/s whose quality, safety and/or efficacy are being tested in a specific clinical trial. There may be more than one investigational product in a clinical trial. Investigational products may be registered or unregistered medicines, vaccines or medical devices. Other terms used are: study drug, study medicine, trial drug/medicine, and trial product.
A sponsor is an individual, company, institution or organisation which takes responsibility for the initiation, management, and financing of a clinical trial. Sponsors are usually manufacturers of pharmaceutical products, government, research institutions, World Health Organization (WHO), foreign governments, etc.
An investigator is a suitably qualified professional person who has the responsibility to design, conduct, analyse and/or report on a specific clinical trial. Investigators usually work as a team.
A leader of a team of investigators is called a Principal Investigator (PI). The PI is accountable to the sponsor and regulatory authority. An investigator may be a medical doctor, dentist, nurse, statistician, medical scientist, pharmacist, mental health professional, or a member of the paramedical professions, etc.
Placebo refers to a treatment known to be without effect; usually used to compare against a potential effective medicine, or vaccine, or medical device which is being subjected to a clinical trial.