Clinical Trials | Definitions




The World Health Organization (WHO) definition for a clinical trial is: "any research study that prospectively assigns human participants or groups of humans to one or more health-related interventions to evaluate the effects on health outcomes".

Clinical trial interventions include but are not restricted to:

  • experimental drugs
  • cells and other biological products
  • vaccines
  • medical devices
  • surgical and other medical treatments and procedures
  • psychotherapeutic and behavioural therapies
  • health service changes
  • preventive care strategies and
  • educational interventions

A clinical trial is mainly divided into 4 phases according to the development of a determined product or medical device:

  • Phase I: can be the very first administration in human being (first-dose-in-man studies). Phase I trials are necessary to learn more about safety and tolerability of a product/device and to investigate the pharmacokinetics and pharmacodynamics of a product. The subjects are generally healthy volunteers.
  • Phase II: based on the positive exit of the Phase I studies, the Phase II trials aim to investigate further the product/device safety/tolerability and effect in human at larger scale (more than 100 subjects) on healthy volunteers or patients
  • Phase III: those studies are conducted on patients at international level, to investigate the product/device effect at long-term, on a larger scale of patients
  • Phase IV: also called Post-Marketing Surveillance Trials, they are the observation of the product/device while already on the market.

A clinical trial can be sponsored by a pharmaceutical company for commercial ends or academic, i.e. not funded by a pharmaceutical company but by public-good agencies (usually universities or medical trusts) to advance medicine. They benefit patients and play an important role in the checks and balances that regulate commercially oriented clinical trials.



Clinical trial interventions include but are not restricted to:

  • For the development of new products or devices to be effective and safe for the human being: in fact, a computer simulation and animal testing can only tell about how a new treatment might work but cannot substitute testing in a living human body.
  • For testing and monitoring the effect of a product/device on a large number of people to ensure that any improvement due to the tested product occurs for many people and is not just a random effect for a one person.
  • To validate new products/devices becoming available in the shorter possible time helping people to live longer and to have less pain or disability.
  • To improve health care services by raising standards of treatment. Doctors and hospital staff involved in clinical trials are continually trained to provide best practice patient care.
  • To provide important information on the cost-effectiveness of a treatment, the clinical value of a diagnostic test and how a treatment improves quality of life