The 4 phases and discovery timelines of Clinical Trials

Broadly speaking, clinical trials follow a consistent process that includes four different phases. Each phase is crucial to uncovering the best possible results of any given study, and as such, is designed to ensure rigour and reliability in the results. The phases contain different numbers of participants, and all serve individual purposes. Let’s take a look at the step by step process of a clinical trial.

Safety is paramount

It must first be noted that safety is emphasised at every step of the process. If a trial does not have a safe or positive outcome in the first phase of the trial, it will be discontinued. This guideline is followed for each phase of clinical trials.  

Phase 0

Before even reaching the first official phase of a trial, a clinical trial has a ‘Phase 0/Pilot Phase’. Just like at any stage of the process, the researchers must obtain permission from relevant health authorities before proceeding. Once permission is granted, clinical trials can begin. During Phase 0, the treatment is tested on a very limited number of healthy humans. This stage can give an indication of optimal dose size and see how the body responds to the drug. If the treatment is deemed safe for use during this phase, it can proceed to phase 1.

Phase 1 clinical trials

Phase 1 clinical trials use a small number of participants (~20-80). This is a foundational phase in the clinical trial process, as the purpose is to find out how the treatment affects the body. Ultimately, the purpose of Phase 1 clinical trials is to identify a safe dose range and determine side effects. Additionally, this stage aims to establish the best method to administer the new treatment.

Phase 2 clinical trials

Phase 2 clinical trials are conducted on a larger scale, and are slightly more technical. In this stage, there is a larger number of participants, and the trials are designed to determine whether the treatment has the intended or desired effect on the disease whilst continuing to monitor safety.

Some Phase 2 clinical trials are conducted with randomised participants, and others with targeted kinds of patients and participants, based on age, gender, pregnancy status and other considerations. Often these trials involve hundreds of patients who have the disease in question. This stage of the process can take months or even a number of years to complete. This phase establishes dosing requirements and the efficacy of the treatment when applied at that dosage.

Phase 3 clinical trials

Phase 3 clinical trials involve a still larger group of participants- several hundred to thousands. This stage uses only randomised participants and is designed to compare the new treatment to an existing treatment.

The ultimate purpose of Phase 3 clinical trials is to establish and confirm the safety and efficacy of the new treatment. This stage can involve thousands of participants, and the studies sometimes take years to complete. Again, there are two subsections in this phase. Phase 3 is designed to obtain approval for the drug from relevant authorities and seeks to find and establish further safety data around the new treatment.

Whilst this stage is the most important when it comes to actually proving the efficacy of a new treatment, it is not the end of the process.

Phase 4 clinical trials

Phase 4 clinical trials serve the purpose of monitoring the effectiveness of the new treatment after approval and collecting information about any adverse effects associated with long-term and widespread use. It is sometimes known as the surveillance stage of clinical trials. This part of the process usually involves thousands of participants and can be a years-long process. The potential use of the treatment in different conditions may also be explored alone or in combination with other therapies. 

Success Rates

The success rates of each phase of a clinical trial, and indeed the entire process, vary based on a number of factors. 

The Medicines Australia 2021 Fact Book states that, on average, the cost of bringing a new medicine to market is approximately US$2.6 billion, and it can take between 10 to 15 years to complete the process. 

There is a very thorough process that excludes any ineffective potential treatments. Whilst this means a large portion of clinical trials does not yield a new treatment for an illness or disease, each clinical trial teaches us something. At the most basic level, we always find out whether a new treatment is viable or we can rule one out. As such, each study emphasises the importance of clinical trials. 

At White Coats Foundation, we provide access to credible resources and information to help guide people’s journey in understanding clinical trials and consumer and community involvement in research.

You can also take a look at the list of Australian clinical trial sites on our resources page.

White Coats Foundation 

White Coats is a Not for Profit Australian-based charity.  The Foundation was established in recognition of the need to raise awareness about the role of clinical trials in advancing medical science and healthcare. We are providing information about clinical trials through our Webinar Series and Our Blogs. We also provide access to credible resources and information to help guide people’s journey in understanding clinical trials and consumer and community involvement in research.

Please note: White Coats blogs are informational only and do not constitute advice. Please contact your relevant healthcare professional for advice on clinical trials for you.

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