With each phase building on the results of the phase before, clinical trials are usually conducted in four phases (phase I-IV.)
Phase 0 – Does This Drug Behave In The Way It Is Supposed To?
- Unusual for trials involving cancer patients
- Small group, low dose (too small to treat cancer)
Phase I Trials – Is It Safe?
- Small studies (~15-20 people)
- Researchers are learning:
- Best way to administer treatment
- Highest dose possible without serious side effects
Phase II Trials – Does it Work?
- Looking at how effective the treatment is
- Slightly larger studies (~25-100 people)
- Start with the dose and method identified in phase I, monitor for benefits
- Benefits sought vary based on research goals
- If a certain percentage benefit and side effects remain acceptable, treatment may move on to phase III
Phase III Trials – Is it Better Than What We Have Now?
- The safety and effectiveness of the study drug is compared to current standard of care. Is the study drug better or different in some way than what we have now?
- Usually large numbers of participants (several hundred to several thousand)
- Participants across US and sometimes around world are included in these trials.
- This is the last step before the U.S. FDA considers approving it for use.
- Participants are still monitored closely for any serious side effects during their participation.
Phase IV Trials – Are There Any Other Uses or Benefits?
- Ongoing review of benefits and any long-term side effects
- Usually done after the drug is approved by U.S. FDA
- Less common than phase I-III
- Large studies (hundreds of thousands of people)