Besponsa (inotuzumab ozogamicin, previously CMC-544) is an approved therapy developed by Pfizer to treat adults with B-cell precursor acute lymphoblastic leukemia (ALL) whose disease has relapsed or who did not respond to standard therapy.

How Besponsa works

ALL is a type of blood and bone marrow cancer characterized by abnormally high production and survival of immune cell precursors in bone marrow. These cancerous cells fail to fully develop and can overcrowd the bone marrow, stopping production of white blood cells and other immune cells.

The cancerous cells can spread throughout the body, forming tumors. In around 90 percent of ALL cases, the cancerous cells express a protein called CD22.

Besponsa is an antibody-drug conjugate (ADC). The antibody, or protein designed to bind to a specific target, interacts with CD22 found on the surface of ALL cancer cells. This interaction causes the cell to absorb Besponsa. The drug, calicheamicin, which is conjugated to the antibody part of the dru, can then break the DNA once inside the cell, killing it.

This mechanism lets Besponsa kill ALL cancer cells in a targeted manner, reducing damage to other tissues.

Besponsa in clinical trials

The European Commission (EC) approved Besponsa on June 30, 2017. The U.S. Food and Drug Administration (FDA) did likewise on Aug. 17, 2017.

These approvals were largely based on positive results seen in a Phase 3 trial (NCT01564784) called INO-VATE ALL. This was a randomized, open-label, multicenter study comparing the efficacy and safety of Besponsa to chemotherapy in 326 patients with CD22-positive ALL.

Of patients on Besponsa, 81 percent had complete remission, compared to only 29 percent of patients on chemotherapy, according to results published in the New England Journal of MedicineFurthermore, Besponsa maintained remission for longer (a median of 4.6 months) than chemotherapy (3.1 months). There was also an increase in the median overall survival by 1.5 months, but this difference was not significant.

Other information

The most common side effects caused by Besponsa are infection, fatigue, bleeding, fever, nausea, headache, abdominal pain and jaundice.

Patients also face an increased risk of problems related to blood cell deficiencies. These include low platelet count, which may cause excessive bleeding, as well as low white blood cell count, which may increase the risk of infection, and anemia or low levels of red blood cells, leading to decreased ability to carry oxygen.

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