Adults with more than 12 months history of migraines were assigned randomly in a double-blinded study to receive treatment with experimental drug x or placebo. the primary efficacy measure was the reduction in the severity of the migraine attacks. enrollment was 1200 subjects. which clinical phase does this best describe?

Phase III.

Explanation:

Clinical trials may be defined as the data that are collected for the development and safety of the new drug. The clinical trial is divided into the four different phases.

The phase III of the clinical trial involves the blind study on the large number of the patients. This trail results in the proper development and the effect of the new drug. The drugs complete their trail testing and after this the drug requires the approval of FDA.

Thus, the correct answer is Phase III.