How is a compound studied?

From the laboratory to people

Research on a compound usually moves through stages. It is first studied in the laboratory, with cells or tissues (in vitro studies), and in animal models (in vivo studies). This is known as the preclinical phase.

If the results justify it, it may move on to clinical trials in people, which are organised in phases. Broadly, phase 1 explores safety in small groups, phase 2 looks for first signs of effect and phase 3 compares the compound with an existing treatment or a placebo in larger groups. A health authority then reviews the evidence before authorising a specific use, and monitoring continues after authorisation.

What each stage answers

An in vitro result can show a possible mechanism, but it does not demonstrate an effect in a whole organism. An animal result is a lead, but it often does not carry over to people.

Only well-designed clinical trials can estimate effects and risks in humans, and even then their conclusions are limited to the population, dose and context that were studied.

Research and authorisation status

Not every compound is at the same stage. Some only have preclinical studies; others have trials in people; others are authorised for a specific use in certain countries. That status can change over time and differs from country to country.

The sheets in the BESTLA catalogue describe published lines of research. They do not indicate that a compound is authorised and are not instructions for use.

How to recognise the type of evidence

When you read a claim about a compound, it helps to identify where it comes from:

• In vitro: cells or tissues in the laboratory.
• In vivo in animals: animal models.
• Observational in people: what happens is recorded without assigning interventions.
• Randomised clinical trial: participants are randomly assigned to different groups.
• Systematic review: gathers and appraises, in an orderly way, all available studies on a question.