How long does a new drug take to go through clinical trials?

There are many factors that affect how long it takes for a drug to be licensed. It might take 10 to 15 years to complete all 3 phases of clinical trials, but this varies.

Drug testing and licensing
Factors that affect how long trials take

Drug testing and licensing

All new drugs and treatments have to be thoroughly tested before they are licensed and available for patients.

A new drug is first studied in the laboratory Open a glossary item . If it looks promising, it is carefully studied in people. It may be then licensed if the trial shows that it works well and doesn’t cause too many side effects. You may hear this process called ‘from bench to bedside’.

There is no typical length of time for a drug to be tested and approved. It might take 10 to 15 years or more to complete all 3 phases of clinical trials before the licensing stage. But this time span varies a lot.

There are many factors that affect how long it takes for a drug to be licensed.

Factors that affect how long trials take

There are many factors that can affect how long a trial will take, including:

the type of cancer
the type of treatment
the type of trial
the number of patients needed
the follow up period
problems with the new treatment

Type of cancer

Clinical trials for rarer cancers can take longer because there are fewer patients available to take part. Research teams from several different countries may need to work together so there are enough patients. This can mean the trial takes longer to organise and set up. International trials can often recruit people more quickly and so might be quicker in the long run.

It is often easier for find people to take part in trials for more common cancers.

Type of treatment

Trials that use new methods of giving treatment, such as a new way to give radiotherapy for example, may take longer to set up and run. This is because the research teams need specialist equipment and training. These trials may only run in a small number of hospitals.

How long treatment takes can also affect the results. It is likely to be quicker to get results for a trial looking at a short course of treatment compared to treatments lasting months or years.

Type of trial

Some trials look at treatments to prevent cancer or ways of screening for cancer. Screening means testing for cancer in people who don’t have any signs or symptoms.

People who join screening or prevention trials haven’t been diagnosed with cancer. The research team will often want to follow them for many years to see who develops cancer and who doesn’t.

Researchers might look at people who have a high risk of developing cancer. For example, to see if:

a medicine can help prevent cancer
a test can diagnose cancer earlier

These trials often take a long time to get results compared to cancer treatment trials. It can take years to see a clear difference in the number of people in the different groups who go on to develop cancer.

Number of patients needed

Experts in statistics look at what the research team want to find out and the design of the trial. They then work out how many patients need to take part in the trial. If there aren’t enough patients taking part, the results may not be reliable.

Follow up period

Research teams look at how well people are doing for a period of time after they have treatment. This is called follow up. Researchers do this to see how well the treatment works over time and if there are any long term side effects.

Follow up periods can last from a few months to over 10 years. This depends on the type of treatment and the group of patients. Trials looking at cancer screening or prevention might have longer follow up.

Problems with the new treatment

Sometimes, new drugs or treatments can cause unexpected problems. For example, people might have severe side effects. Or there may be difficulties in giving the treatment to patients. These issues could mean the trial takes longer to complete.

References

Clinical trials for medicines: apply for authorisation in the UK
Medicines and Healthcare products Regulatory Agency
GOV.UK website, last updated 27 August 2024
Accessed July 2025