How long does it take for a new drug to go through clinical trials? | Cancer Research UK
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How long does it take for a new drug to go through clinical trials?

This page tells you about the process of testing and approving new drugs. There is information about


What clinical trials are

All new drugs and treatments have to be thoroughly tested before they are licensed and available for patients. It takes time for a new drug to go through the various stages of testing. This process is often called from the bench to the bedside. A new drug is first studied in the laboratory. If the drug looks promising, it is carefully studied in people. Studies that involve people are called clinical trials. Clinical trials in cancer look at

  • Risks and causes - how genetics, lifestyle and other factors can increase cancer risk
  • Preventing cancer using drugs, vitamins, or changes in lifestyle, including diet
  • Screening for people at higher than average risk, or for the general population
  • Diagnosing cancer with new tests or scans
  • Treatments with new drugs or combinations of drugs, new ways of giving treatment or new types of treatment
  • Controlling symptoms with new drugs or complementary therapies

New drugs are only prescribed and used as part of standard treatment for cancer after they have gone through clinical trials.


Why we need clinical trials

We need clinical trials to find out whether a new treatment

  • Is safe
  • Has side effects
  • Works better than the treatments already in use
  • Helps you feel better

Researchers have to find all these things out before a drug can be licensed. There is more information about clinical trials in our research and trials section.


The phases of clinical trials

There are 3 main phases of clinical trials. All new drugs have to go through the phases before they can be licensed and prescribed for patients

  • Phase 1 trials recruit a small number of patients (up to about 30) to try to find out about drug side effects and the best dose to give
  • Phase 2 trials recruit more patients (up to about 50) and look at how well the drug works for particular types of cancer
  • Phase 3 trials are much bigger (100s or even 1000s of patients), and compare new treatments to the standard treatments to see which is better

Although many drugs or products start life in phase 1 trials, they don’t all get as far as phase 3 trials and the licensing process.

There are also phase 4 trials. These are carried out after a drug has a license. They aim to find out more about the longer term risks and benefits. And they also want to find out how well the drug works when it is used more widely. There is information about the drug licensing process in our questions and answers section – choose trials and research from the dropdown menu. We also have more information about phases of trials.


The time a drug takes to go through clinical trials

There is no typical length of time this takes. 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 and depends on many factors, such as

The type of cancer

Clinical trials for rarer cancers often take longer to recruit. This because there are fewer patients available to take part. Several different countries may need to collaborate to recruit enough patients. So this can make the trial take longer to organise and set up. But an international trial will recruit more quickly and so is likely be quicker in the long run. 

The type of treatment

Trials are easier to run that use standard ways of giving treatment. These standard ways include giving a drug by mouth (as tablets) or through a vein (by drip). If a trial uses standard delivery methods, more hospitals are likely to be able to take part. But some new treatments need special equipment or specially trained staff, and have to take place in specialised centres. So it may take longer to recruit the number of patients they need for the trial.

The number of patients needed

Trials are designed to look at various things. The research team may want to find out if a new treatment is better than current treatment. Or if it is no worse than the current treatment. They also need to find out how much better the new drug works. The number of patients in the trial has to be enough to be able to find these things out. The results, or data, are looked at statistically (called statistical analysis). If the trial doesn’t recruit enough patients, the results may not be reliable.

The length of treatment

It is quicker to get results about treatment that is a single dose or short course, compared to a drug that you take for months or even years.

The follow up period

The research teams follow the progress of all patients in clinical trials for some time after treatment. This is to see how well the treatment works over a longer period, and to find out more about long term side effects.

Follow up periods can range from a few months to over 10 years, depending on the type of treatment and the group of patients tested. For example, new treatments for advanced cancer might prolong life by a few months so the results are available relatively quickly. On the other hand, a trial looking at whether a new treatment is better at stopping cancer coming back will need follow up for several years. Those looking at preventing cancer take longer still.

Any problems with the new drug

There may be problems with new drugs that the researchers won't know about until they run the trials. There could be unexpected side effects or reactions to treatment. Or there may be difficulties in delivering the treatment to patients. All of these factors can lengthen the trial period.


Further information about clinical trials

We have more information about clinical trials including what to expect if you take part in one. You can find details of current UK clinical trials for cancer on our searchable clinical trials database. All the information is written in plain English.

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Updated: 9 October 2013