Pfizer’s antibody drug conjugate Besponsa has become the first to be approved by regulators in Europe to treat some adults with the rare, aggressive cancer acute lymphoblastic leukaemia (ALL).The decision allows the drug’s use for relapsed or refractory CD22-positive ALL in patients who have failed treatment with at least one tyrosine kinase inhibitor (TKI).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.Its clearance in Europe represents “an important milestone for patients, the oncology community and Pfizer,” said Andreas Penk, regional president, Pfizer Oncology.“This is the first approval for inotuzumab ozogamicin and provides patients in the EU, who are battling an especially hard-to-treat leukaemia, with a new treatment option beyond chemotherapy.”Around 760 people in the UK are diagnosed with ALL every year. For those with relapsed or refectory forms of the disease median overall survival is just three to six months, highlighting the urgent need for new treatment options.The goal of treatment in R/R ALL is to achieve complete remission without excessive toxicity so patients may proceed to additional therapeutic intervention, particularly stem cell transplant, which is the most recognised option to prolong patient survival, maintenance therapy or other therapy, the firm noted.Besponsa’s approval was based on data from the INO-VATE trial, which compared the drug to standard of care chemotherapy in 326 adult patients with relapsed or refractory CD22-positive ALL, and showed that it more than doubled complete remission rates.The co-primary endpoint of complete remission with incomplete haematologic recovery was achieved by 80.7 percent of patients treated with Pfizer's drug and 33.3 percent of those given the standard of care.However, last month the National Institute for Health and Care Excellence published draft guidelines barring the drug from the NHS’ routine commissioning stream, arguing that its survival benefit is “highly uncertain”.. Pfizer’s antibody drug conjugate Besponsa has become the first to be approved by regulators in Europe to treat some adults with the rare, aggressive cancer acute lymphoblastic leukaemia (ALL). The decision allows the drug’s use for relapsed or refractory CD22-positive ALL in patients who have. BESPONSA is a prescription medicine used to treat adults with relapsed or refractory B-cell acute lymphoblastic leukemia (ALL). It is not known if BESPONSA is safe and effective in children under 18 years of age..