(Reuters) - AstraZeneca Plc AZN.L said on Tuesday it would start a clinical trial of its cancer drug Calquence to assess its potential to control the exaggerated immune system response associated with COVID-19 infection in severely ill patients.

FILE PHOTO: The company logo for pharmaceutical company AstraZeneca is displayed on a screen on the floor at the New York Stock Exchange (NYSE) in New York, U.S., April 8, 2019. REUTERS/Brendan McDermid/File Photo

Calquence (acalabrutinib) belongs to a class of drugs called Bruton’s tyrosine kinase (BTK) inhibitors which can suppress autoimmune diseases. The drug, which is currently used to treat certain types of blood cancers, has already been approved for the treatment of adult patients with chronic lymphocytic leukaemia in the U.S. and several other countries.

Calquence competes with AbbVie Inc ABBV.N and Johnson & Johnson's JNJ.N established treatment Imbruvica as a treatment for chronic lymphocytic leukemia, one of the most common types of leukemia in adults.

The British drugmaker’s shares rose as much as 7.3% to 7642 pence by 0855 BST.

AstraZeneca’s announcement comes as drugmakers are having to pause clinical trials for other disease areas as they focus on testing potential treatments for the fast-spreading coronavirus.

Patients with severe symptoms including pneumonia are believed to suffer from an over reaction of the immune system known as cytokine storm and AstraZeneca aims to test whether Calquence, which suppresses certain elements of the immune system, can help control this immune response.

“Given the well documented role of the protein BTK in regulating inflammation, it is possible that inhibiting BTK with acalabrutinib could provide clinical benefit in patients with advanced COVID-19 lung disease,” said Louis Staudt, chief of the lymphoid malignancies branch at the National Cancer Institute.

The trial will evaluate the effectiveness and safety of adding the drug to best supportive care to reduce mortality and the need for assisted ventilation in patients with life-threatening COVID-19 symptoms, the drugmaker said.

It is expected to open for enrolment in the coming days in the U.S. and several countries in Europe, AstraZeneca said.

Earlier this month, AstraZeneca and its domestic rival GlaxoSmithKline PLC GSK.L agreed to set up a testing laboratory to aid in COVID-19 testing with Cambridge University.