Clinical trials are research studies involving people. They
compare a new or different type of treatment or prevention – the
‘intervention’ - with the best treatment
or prevention currently available – the
‘control’. Clinical trials may use a
‘placebo’ when no standard treatment or prevention
is available.
No matter how promising a new drug, treatment or prevention may
appear during tests in a laboratory, it must go through clinical
trials before its benefits and risks can really be known.
Trials aim to find out if the interventions:
- Are safe
- Have side effects
- Work better than the treatment or prevention
used currently
- Help people feel better
It is now widely agreed that a properly run clinical trial is
the best way to assess whether a treatment or prevention is, or is
not, safe and effective. Evidence from clinical trials is essential
to support an authorisation to market a treatment or prevention. In
the UK authorisation is controlled by a government authority known
as the Medicines and Healthcare products
Regulatory Agency (MHRA).
Different phases of trials
New drugs go through a number of different phases of trials, and
the same principles apply to prevention interventions:
- Phase I trials aim to test the safety of a
new treatment. They look at side effects of a treatment, measuring
the amount of drug absorbed (if possible) to work out the
‘tolerated dose’. Phase I trials involve only a small number of
people, who are often healthy volunteers and are usually quite
intensive in terms of frequent visits.
- Phase II trials test the new treatment in
increasingly larger groups of people who usually have the disease
for which the treatment is to be used, or are at risk of acquiring
it. In this phase, researchers are hoping to get a sense of how
well the treatment or prevention might work. The size varies
considerably from less than one hundred people to a thousand or
more.
Treatments only move into a phase III clinical trial if the
intervention is safe in phases I and II and there is a reasonable
chance of effectiveness.