What are the phases of a clinical trial?

Phase

Purpose

Time

Preclinical

Assessing the safety and biological activity using animal models in the laboratory

No participants

3- 6 years

Phase 1

Determining which dose is safe, how often if should be given and the best form of treatment 

Few participants

1-2 years

Phase 2

Assessing the effectiveness of the treatment, its side effects and tolerance levels

More participants

2-4 years

Phase 3

Determine whether the new treatment works better than an alternative current standard treatment

Most participants - often 100+

3-5
years

Phase 4

Phase 4 studies are done once the drug or treatment is available on the market. They usually involve new participants are done to gather long term safety information on the new treatment. 

2-5 years