“If a new treatment is found to be reasonably safe in phase I clinical trials, it can then be tested in phase II clinical trial to find out if it works.
During this trial, the investigational medicinal product is tested for efficacy (and safety).
These trials are designed to evaluate the drug’s efficacy in people with the disease or condition being studied and to determine the common short-term adverse effects and risks associated with the drug.
Phase 2 trials aim to find out:
- if the new treatment works well enough to be tested in a larger phase 3 trial
- more about side effects and how to manage them
- more about the best dose to use
Phase 2 trials are usually larger than phase 1 and are performed on larger groups (50–300).
They are designed to assess how well the drug works, as well as to continue Phase I safety assessments in a larger group of volunteers and patients.
Phase II studies are sometimes divided into Phase IIA and Phase IIB.
- Phase IIA studies are usually pilot studies designed to demonstrate clinical efficacy or biological activity (‘proof of concept’ studies)
- Phase IIB studies look to find the optimum dose at which the drug shows biological activity with minimal side-effects (‘definite dose-finding’ studies).
Some trials combine Phase I and Phase II, and test both efficacy and toxicity.”