Phase II Clinical Trial
The second stage of clinical testing, evaluating preliminary efficacy in 100-300 patients with the target condition while continuing to assess safety. Phase II may be divided into Phase IIa (proof of concept) and Phase IIb (dose-ranging). Many compounds fail at this stage.
Technical Context
Phase IIa (proof of concept) typically enrols 20-100 patients to determine whether the drug produces the expected pharmacological effect in the target disease. Phase IIb (dose-ranging) enrols 100-300 patients across multiple dose groups to identify the optimal dose(s) for Phase III. For GLP-1 RAs, Phase II endpoints typically include HbA1c change, fasting plasma glucose, body weight change, and tolerability at each dose level. The dose selection decision between Phase II and Phase III is critical — choosing too low a dose risks insufficient efficacy, while too high risks excessive side effects and trial failure. Adaptive Phase II designs can modify dose groups based on interim results, improving efficiency.