Phase III Clinical Trial
The most extensive stage of clinical testing, definitively confirming efficacy and safety in 300-3,000+ patients through randomised controlled trials. Phase III results are the basis for regulatory approval applications. The STEP (semaglutide) and SURMOUNT (tirzepatide) programmes are prominent examples.
Technical Context
Phase III characteristics: randomised, controlled (placebo and/or active comparator), double-blind, multicentre (often multinational), adequately powered (typically 80-90% power), pre-specified primary and secondary endpoints, intention-to-treat primary analysis, and pre-registered protocol. Regulatory agencies typically require two adequate and well-controlled pivotal trials (or one very large trial with robust results). GLP-1 RA Phase III programmes have been among the largest in metabolic medicine: the SUSTAIN programme (semaglutide for diabetes, 8 Phase III trials), STEP programme (semaglutide for weight, 5 Phase III trials), SURPASS programme (tirzepatide for diabetes, 5 Phase III trials), and SURMOUNT programme (tirzepatide for weight, 4 Phase III trials).