The study, involving researchers in the Hope Clinical Trials Facility at Leicester’s Hospitals and the University of Leicester, consisted of one hundred and twenty participants over eleven sites.

Patients took a combination of venetoclax (an oral inhibitor of BCL2) with obinutuzumab (an intravenous CD20 monoclonal antibody). They were given either venetoclax or obinutuzumab first, then after safety and dose determination was compared, the patients had a combination of the two treatments over six cycles, followed by venetoclax on its own until disease progression or for a fixed time of one year.

Ultimately, 95% of those treated were found to have a complete remission rate, meaning there were no signs of the leukaemia in the blood or in scans, and the patients had no symptoms.

Dr Harriet Walker, a Cancer Research UK clinical trials fellow and associate professor at the University of Leicester who worked on the study, said: "Chemotherapy is currently the first treatment for CLL. However, it is not always suitable in older patients and those that have other health issues. In addition, some people develop CLL that becomes resistant to chemotherapy.

"While the data from this study are preliminary, the novel combination is now being assessed in other studies worldwide, as it will be important to understand its success rate in larger cohorts and in more circumstances. However, we are hopeful that it will become a therapeutic option that will allow us to more effectively treat patients with CLL."

CLL is a type of cancer in which the bone marrow inside the bones makes too many lymphocytes, which then take up too much space in the bone marrow, so there is not enough room for making normal red blood cells and platelets. It is the most common form of adult chronic leukaemia.