Clinical trials are commonly classified by phase, where the phase indicates the stage in which scientists conduct research. Each clinical trial phase has different goals and targets to reach before a potential new treatment or medical device can move forward.  

In this article series we discuss the different phases in clinical trials, while making a distinction between IP (Investigational Product) trials and MD (Medical Device) trials. 

This post focuses on the 4 phases for IP trials, also known as drug trials. Our CRO specialises in Phase II, III and IV studies.

The 4 Phases of clinical trials by Diagram Research

The 4 Phases For IP Trials

Each phase is designed to answer specific questions and all new pharmaceuticals/drugs have to pass through this sequence:

  • Phase I: Is the treatment safe?
  • Phase II: Does the treatment work?
  • Phase III: Is the treatment better than what’s already available?
  • Phase IV: What else do we need to know?

On average it takes 10-15 years for new treatments to cover all phases, to receive approval from the EMA and/or FDA and to become available for patients.

What is Phase I of a clinical trial?

Phase I of a clinical trial answers the question: Is the treatment safe? Also known as ‘first-in-men study’ or ‘first-in-human study’, Phase I consists of the first administration of a new drug to human subjects, usually a small group of healthy volunteers. 

Phase I’s main goal is to determine best and safest dose, to evaluate safety and to identify side effects. This is generally done by increasing dosage while observing tolerance and safety.

What is Phase II of a clinical trial?

Phase II of a clinical trial answers the question: Does the treatment work? It consists of a first administration in a small group of human subjects with a certain disease or condition. 

Phase 2a are the proof of concept studies and Phase 2b are the definite dose-finding studies. 

Phase II’s main goal is to test effectiveness (how well the drug works) and to further evaluate safety in a larger group of subjects.

Examples: CEL-02 and CELEBRATE

What is Phase III of a clinical trial?

Phase III of a clinical trial answers the question: Is the treatment better than what’s already available? Phase III clinical trials compare the safety and effectiveness of the new treatment against the current standard treatment.

This phase primarily consists of testing the final dosage in real world medical practice on its usability and effectiveness in a large group of subjects. Safety in the short and longer terms are observed. 

Phase III’s main goal is to confirm effectiveness, to monitor side effects, to compare to other treatments and to collect information. 

Example: EUROMAX and On-TIME 2

When phase III is completed successfully, the drug is submitted to the European Medicines Agency (EMA)and/or the Food and Drug Administration (FDA) for approval. Approval means that the new treatment is officially registered and therefore available for doctors to prescribe to their patients.

What is Phase IV of a clinical trial?

Phase IV is the final phase, also known as ‘post marketing surveillance trial’ or ‘drug monitoring trial’. Phase IV of a clinical trial answers the question: What else do we need to know? It consists of research after authorisation and is related to the indication area for which the product is authorised. 

Phase IV trials aren’t necessary for authorisation purposes, but gather additional information about long-term safety, efficacy and optimal use in large and diverse populations.

Phase IV’s main goal is to confirm effectiveness, to provide additional information after approval, including risk, benefits and best use.

Examples: Early BAMI

The 5 Phases For Medical Device Clinical Trials 

The approach to testing medical devices is fairly similar to testing drugs and is also divided into phases. In our next article we discuss the 5 stages for MD (Medical Device) trials.

Discover the trials Diagram Research executed earlier

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