Pharmacokinetics and pharmacodynamics of a new formulation of an investigational drug most likely refers to which clinical phase of a study in humans?

The correct answer is - Phase I.

Explanation:

Clinical phase are group of stages in which scientists or researchers  conduct various experiments with a health intervention to get enough evidence for a process to use as a medical treatment. Clinical research is conducted on medical devices, drug candidates, and vaccine candidates.

In the phase I, in this phase intervention takes place in human subjects. These subject usually observed until several half-lives of the drug have passed. This phase is designed to assess the tolerability, pharmacokinetics, safety (pharmacovigilance), and pharmacodynamics of a drug