Phases of trial

Before a treatment enters the various phases of clinical trials, several preclinical studies are done to find out whether the treatment has the expected effect and whether it is safe. These studies usually involve animals or cells grown in a laboratory dish. Preclinical studies are an important part of making sure it is ethical and safe to test a treatment on people. 

Sometimes, a very small amount of the treatment will be tested in humans for the first time before clinical trials, to help researchers plan what to measure during trials. 

Read more about safety in trials

Phase 1 and phase 2 trials are sometimes referred to as ‘early phase trials’. Early phase trials are the first steps a clinical trial goes through. People who take part in these trials might be some of the first people to receive a new treatment.

These trials tend to recruit in small numbers and focus on whether a new treatment is safe. Phase 2 trials may also evaluate the correct dose and early signs of whether the medication works. See phase 1 and phase 2 clinical trials below. 

We support a specialist network of CF early phase centres and trials coordinators in the UK through the Clinical Trials Accelerator Platform (CTAP). Read one of our CTAP early phase trial coordinators talking about her role. 

A small study, less than 30 people. Looks at whether a trial treatment is safe or has side effects.

Duration: 1 month

Participants: 10 – 20

Purpose of this phase: Is it safe? How does the body process it? What are the side effects?

An example: A study that measures the safety and tolerability of a new modulator drug to restore CFTR function. For example, the VX-121 study. 

A larger study. Looks at how well a treatment works and how much should be taken in one dose.

Duration: 3 – 12 months

Participants: Up to 100

Purpose of this phase: Is it safe? How well is it working? How much should be taken?

An example: A study that measures the effectiveness of nebulized nitric oxide to treat lung infection. For example, the NOMAB study. 

Much bigger, possibly hundreds of participants. Tests a new treatment against standard existing treatment and looks at whether the benefits outweigh the risks. 

Duration: 6 – 24 months   

Participants: 100 – 300    

Purpose of this phase: Is it safe?  How well is it working? Does the benefit outweigh the risk?

An example: A study that compares taking antibiotics intravenously to orally to treat a lung function. For example, the TORPEDO-CF trial. 

NICE review and approval

If successful, an application is submitted to NICE. Application is reviewed before being approved and finally made available to public

Further assessment and monitoring of a treatment after it has become available to the public (licensed). This also typically involves hundreds of people and will look at whether the treatment is safe, has any rare side effects, and whether it is cost effective and works better than other existing treatments.

Duration: 6 – 24 months

Participants: 100 – 300

Purpose of this phase: Does it still appear to be safe? Are there rare side effects? Cost effectiveness compared to other treatments.

An example: A study that investigates whether a treatment that makes mucus easier to clear can be stopped for people taking triple combination modulator drugs (e.g. Kaftrio™). For example, CF STORM trial.