US regulators wave through Pfizer’s leukaemia drug

The US Food and Drug Administration has approved Pfizer’s Besponsa, the first and only CD22-directed antibody-drug conjugate indicated to treat relapsed or refractory B-cell precursor acute lymphoblastic leukaemia (ALL). B-cell precursor ALL is a rapidly progressing type of cancer in which the bone marrow makes too many B-cell lymphocytes, an immature type of white blood cell. According to estimates by the National Cancer Institute, around 5,970 people in the US will be diagnosed with ALL this year and around 1,440 will die from the disease. Besponsa (inotuzumab ozogamicin) consists of a monoclonal antibody targeting CD22, a cell surface antigen expressed on around 90 percent of B-cell malignancies, linked to a cytotoxic agent. When the drug binds to CD22 on malignant B-cells it is taken into the cell, where the cytotoxic agent calicheamicin is released to destroy it.