Clinical Pharmacology · MU Sofia

11. Clinical Drug Trials - Phase 3: Design, target population, aims.

Explains phase III trials as the large, multi-centre, randomised, double-blind studies that confirm a drug's efficacy and extend its safety profile before licensing. Covers the typical target population and size, the aims including comparison with placebo or an active comparator, and the design options of superiority, non-inferiority or equivalence with sample size and endpoints. Ends with the limits of phase III, including the rule of three for detecting rare reactions and why phase IV follows.

Inside: 5 sections · 15 flashcards · 2 min

Topic 11 of 30 in the MU Sofia syllabus for Clinical Pharmacology (Medicine, Year 5). The free AceMed note covers it in 5 sections, about 261 words (2 min of reading), with 15 flashcards.

In this note

  1. Introduction
  2. Target population
  3. Aims
  4. Design
  5. Limits of phase III

Introduction

Phase III (therapeutic confirmation) is the large trial that proves the drug works and is safe enough to be licensed. Its results are the core of the application for marketing authorisation.

Target population

  • Usually several hundred to about 3,000 patients (more for common diseases or rare outcomes), with broader inclusion criteria than phase II, closer to the patients who will use the drug.
  • Always multi-centre, often multinational.

Aims

  1. Confirm efficacy, usually against placebo or, increasingly, against the standard treatment (active comparator).
  2. Extend the safety profile: adverse reactions occurring in about 1 in 100 to 1 in 1,000, interactions, effects in subgroups (elderly, renal impairment).
  3. Establish the overall benefit–risk ratio and the dose, indications and warnings that will go into the SmPC.

Design

  • Randomised, double-blind, controlled (placebo or active comparator), parallel groups.
  • Superiority, non-inferiority or equivalence design, defined in advance with a calculated sample size (statistical power).
  • Clinically relevant primary endpoint (e.g. mortality, stroke, exacerbations) or validated surrogate; secondary endpoints; analysis by intention to treat.
  • Duration from months to years for chronic diseases.
  • Usually two adequate, well-controlled phase III trials ("pivotal trials") support approval.

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