The US Food and Drug Administration has given approval for Pfizer’s Besponsa (inotuzumab ozogamicin) to treat adult patients with relapsed or refractory B-cell precursor acute lymphoblastic leukaemia (ALL).

B-cell precursor ALL is a type of cancer in which the bone marrow produces a large number of B-cell lymphocytes, an immature type of white blood cell.

Developed jointly by Pfizer and Celltech, now known as UCB, Besponsa is an antibody-drug conjugate (ADC) made up of a monoclonal antibody (mAb) targeting CD22, a cell-surface antigen expressed on cancer cells in almost all B-ALL patients linked to a cytotoxic agent.

Pfizer oncology global president Liz Barrett said: "The approval of Besponsa is an important step forward for adult patients with relapsed or refractory B-cell ALL, a rare disease that can be fatal within a matter of months if left untreated.

"Besponsa will help address a significant need for new treatment options in B-cell acute lymphoblastic leukaemia, and may help more patients reach stem cell transplant, which provides the best chance for long-term remission."

"The approval of Besponsa is an important step forward for adult patients with relapsed or refractory B-cell ALL, a rare disease that can be fatal within a matter of months if left untreated."

The FDA approval was based on data from a randomised, open-label, international, multi-centre Phase III INO-VATE ALL trial.

The safety and efficacy of the therapy were evaluated in 326 patients with relapsed or refractory B-cell ALL who had received one or two prior treatments.

Administered as a one-hour intravenous infusion, the drug binds to the CD22 antigen on B-cells and is internalised into the cell where the cytotoxic agent calicheamicin is released, causing cell death.

The treatment was reviewed and approved under the FDA’s breakthrough therapy designation and priority review programmes.