What are Clinical Trials?

About clinical trials

A clinical trial is the process by which a new medication is tested, to understand how well it works and to assess its safety profile. Before a treatment is made available to the general public, it must go through the three clinical trial phases to ensure that the benefits of the treatment outweigh the potential risks, prior to potential approval for use by national regulatory agencies (such as the FDA in the United States, the EMA for much of Europe and the MHRA in the UK).

People who take part in clinical trials are volunteers who are either healthy or have the illness or disease the medication is intended to treat.

Phases of clinical trials

Phase I trials

This is the first time a new drug or treatment is tested in people who are either healthy or have the disease the drug is intended to treat. A small group of people receives the treatment to evaluate its safety, find an appropriate dose, and identify any side effects.

Phase II trials

In this phase, the drug or treatment is given to a larger group of people to study its effectiveness and continue to monitor for potential side effects. Dosages may also change at this stage, while safety continues to be evaluated.

Phase III trials

This phase involves an even larger number of people with the disease the drug is intended to treat. Researchers demonstrate how well the drug works, monitor side effects, compare it to existing treatments, and gather information to ensure it can be used safely1. In this phase, the treatment may also be studied in combination with other treatments to determine the risk/benefit profile and whether this could provide additional benefit to people with the disease.

These are the three main clinical trial phases, although sometimes they can be combined – such as in a Phase 1/2 trial. There is also a fourth phase (Phase IV) that is generally conducted after a treatment has been approved.

Once a clinical trial has gathered sufficient evidence supporting the use of a treatment in people living with a disease, a submission can be made to regulatory agencies for the approval of a new medicine.

Adaptive trials

Adaptive design in clinical trials allows changes to be made to the study as it progresses, without losing accuracy or reliability. The goal is to make trials more flexible, efficient, and more responsive to data that emerges during the course of a trial.

A benefit of adaptive trials is that potential changes to the trial protocol – such as moving patients into a subsequent phase – are pre-approved by regulatory agencies and ethics committees.

Adjustments, such as changing treatments or doses, can be planned in advance, making it easier to respond to unexpected events. Importantly, the integrity of the trial results is preserved.

Adaptive designs can also help identify unsuccessful treatments earlier, allowing trials to end sooner if the drug is not working sufficiently. This means fewer people are exposed to ineffective treatments or unnecessarily high doses. At the same time, pharmaceutical companies can save resources by stopping unsuccessful trials sooner and shifting their focus to more promising treatments that are in development.

Why participate in a clinical trial

Participating in a clinical trial may offer people the chance to:

  • Access a new treatment that is only available in the trial.
  • Have close monitoring of a health condition.
  • Take an active role in managing their healthcare.
  • Help advance research that could benefit future patients.

However, clinical trials also come with risks, which will be explained by a patient’s physician before they decide to join a trial. These risks may include:

  • Possible side effects.
  • Costs that may not be covered by the trial or insurance.
  • Frequent or long medical visits that could take time away from family or work.

Immunocore’s clinical trials

For general information on Immunocore clinical trials, including trials currently open for enrollment, please visit our clinical trials page.

For individuals living in the US, you can visit our clinical trials microsite for full details of our Phase 3 trials.

1 https://www.fda.gov/patients/drug-development-process/step-3-clinical-research#Clinical_Research_Phase_Studies


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DOP: April 2026