Clinical trials

Learning about cancer and cancer treatment is a continuous process. Every new idea and development in treatment needs to be tested in a way that is scientifically reliable. This is done by testing the treatments in controlled trials.

A clinical trial is essentially medical research study which normally involves patients but sometimes healthy people who act as a control.

Clinical trials for blood cancers are mainly carried out to test new treatments, answer questions and find better ways to screen, diagnose, prevent, or treat a particular blood cancer , as well as look at new ways of using existing treatments.

Clinical trials are essential to provide the evidence that a treatment works. Without clinical trials, new treatments for diseases and conditions would not be discovered.  Some clinical trials help to determine if a new treatment is safe and can improve the health of patients.  Other trials compare a new therapy to an existing one to find out which is better at treating or preventing a disease.

Phases of clinical trials

Pharmaceutical clinical trials are commonly classified into four 
phases, and the drug-development process will normally proceed 
through all four stages over many years.

If the drug successfully 
passes through the Phases I, II, and III, it will usually be approved 
for use in the general population. Before clinical trials on drugs start, extensive pre-clinical studies are conducted.

Phase I

Phase I trials usually last for between a few months and 1–3 years. They often involve having quite a lot of blood tests or other investigations done.

Phase I trials are the first-stage of testing in human subjects. Normally a small group of healthy volunteers will be selected (20 – 40 people). This phase includes trials designed to answer questions such as: is the drug safe for humans? What are the side effects? How much of the drug do you need to give? Does it have any effect on cancer?

These trials are almost always conducted in hospital, where full-time medical staff can observe the subject. The  subject is usually observed until the medical staff can be certain that the entire trial drug has been excreted from the body. Phase I trials also normally include dose-ranging studies so that doses for clinical use can be refined. Many drugs don’t get past phase I. Phase I trials are often only for people who have disease that is not responding to standard therapies. This is because it is not ethical to give someone an unknown treatment unless there are no other suitable treatments available.

Phase II

Once the initial safety of the therapy has been confirmed in Phase I trials, Phase II trials are performed on larger groups of people (20 – 300) and are designed to assess clinical efficacy of the therapy; as well as to continue Phase I assessments in a larger group of volunteers and patients. If a new drug fails during its development process it most commonly fails during Phase II trials.  Failure is normally due to the discovery of poor efficacy or intolerable side-effects.

Phase II trials are not always about testing a new drug. Sometimes phase II trials will test an existing drug administered in a different way or at a different dose – or they might want to test it in people with a different type or stage of cancer.

Phase III

Phase III studies are randomised controlled trials on large patient groups (300–3,000 or more depending upon the condition) and are aimed at being the definitive assessment of the effectiveness of the therapy, in comparison with current ‘Gold Standard’ treatment.

Phase III trials are the most expensive, time-consuming and difficult trials to design and run; especially in therapies for chronic conditions. Once a drug has proven satisfactory in Phase III trials, the trial results are usually combined into a large document containing a comprehensive description of the methods and results of human and animal studies, manufacturing procedures, formulation details, and shelf life.

Good phase II or III trial results are required before a drug gets a licence. A licence means that a drug can be marketed as a treatment for a particular condition. Drugs usually have to go through a few phase III trials before they become accepted as standard therapy.

Phase IV

Phase IV clinical trials are done after a treatment has been shown to be effective and after it has been licensed. They are usually carried out by drug companies to find out more about a treatment and side effects.

Phase IV trials involve the safety surveillance (pharmacovigilance) and ongoing technical support of a drug after it receives permission to be sold. The safety surveillance is designed to detect any rare or long-term adverse effects over a much larger patient population and longer time period than was possible during the Phase I-III clinical trials. Harmful effects discovered by Phase IV trials may result in a drug being no longer sold, or restricted to certain uses.

Due to the evolving nature of clinical trials, we are unable to keep up-to-date information about clinical trials on our website:

To find out further clinical trial information, we would recommend the following websites:

Cancer Research UK


Clinical Research Network

Leukaemia Care videos about clinical trials

CLL trials

Video: Dr Guy Pratt discusses the FLAIR trial

Video: Deborah Sims and John Seymour discuss the MURANO trial