Phases of a Clinical Trial

What does Phase I, II or III mean? 

Phase I
The primary goal of Phase I is to test the safety of an active ingredient. Before this type of trial begins, a sort of “initial hurdle”, all the data which has been collected through experiments in test tubes, on cell cultures and on animals is compiled and extensively evaluated. Only once this “initial hurdle” has been overcome and the results of the evaluation suggest that the new active ingredient is probably both safe and beneficial to patients is a test schedule drawn up and a Phase I Study arranged.

In addition to safety information, this first phase of testing is used to gather preliminary information on the dosage and pharmacological properties of the medication (how it is dispersed and metabolised within the body, for example). Phase 1 studies are usually carried out on healthy volunteers – with the exception of active ingredients used in the treatment of particularly serious illnesses, such as cancer or HIV.

Phase II
Once the results of Phase I have confirmed the safety of a particular medicine, Phase II of clinical development can begin. The aim of this phase is to research the medicine’s therapeutic effectiveness and to develop an optimum dosage schedule. A comprehensive Phase II study may involve up to 100 patients.

Phase III
If Phase II trials provide clear indications of a drug’s therapeutic effectiveness, the third phase of clinical trials begins. The new drug’s therapeutic benefits are evaluated on a larger group of volunteers (often several hundred) in a statistically meaningful form. If a proven form of treatment already exists for this particular disease profile, the new active ingredient is tested and evaluated in comparison with this form of therapy. Phase III studies often involve several clinics in different countries.

Approval and Follow-Up Studies
The data from the trial can be used to apply for approval for the drug from the relevant authorities. Even once this approval has been obtained, additional studies are often carried out to learn more about the medication, such as how it can be used in combination with other forms of treatment, for example.