How long a new drug takes to go through clinical trials

This page is about the things that can affect how long it takes for a new drug to go through clinical trials. There is information about

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. 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 it takes 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

The type of cancer

Clinical trials for rarer cancers often 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.

Researchers running clinical trials for more common cancers are generally able to find enough people to take part more easily.

The 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 extra training.  These trials may only be able to run in a small number of hospitals compared to trials using standard ways of giving treatment.  

How long treatment takes can also affect the results. It is likely to be quicker to get results for a trial looking at a single dose or short course of treatment. This is in comparison to a treatment that lasts for months or even years.

The 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.

In people who have a high risk of developing cancer, they may then compare the different trial groups to see if a particular treatment can help prevent cancer. Or whether a test can help to diagnose it early.

These trials often take a long time to get results compared to 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.

The 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. 

The follow up period

As part of a trial, research teams look at how well people are doing for some time after they have treatment. This is to see how well the treatment works over a longer period of time. And to find out more about long term side effects.

Follow up periods can range from a few months to more than 10 years. This depends on the type of treatment and the group of patients. Follow up might be longer for a trial looking at screening or prevention.

Any problems with the new treatment

There may be problems with new drugs or treatments that the researchers don't know about until they run the trials. There could be unexpected side effects or reactions to treatment. Or there may be difficulties in giving the treatment to patients.

Problems with the new treatment may mean the trial takes longer to complete.

Related information

We have information about 

Find a clinical trial

Clinical trial results

Understanding statistics in cancer research


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Please note - unless we state otherwise in the summary, you need to talk to your doctor about joining a trial.

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