A new class of biological medications known as bispecific antibodies may offer hope for hard to treat cancers by using a different mechanism of action than other available treatments. One bispecific antibody called blinatumomab is approved for use in acute lymphoblastic leukemia when other treatments have failed.
Bispecific antibodies have two binding sites, or arms, on the drug molecule. One arm connects to tumor cells and the other connects to T-cells in the immune system. This creates a link that allows the T-cells to destroy the cancer cells, essentially delivering the payload to the target site. Linking T-cells directly to cancer cells increases the ability of the body’s own immune system to fight cancers. Tumor cells, especially those in blood cancers, often avoid contact with T-cells and can grow unchecked, so this new mechanism of action can attack those cancer cells that have avoided treatment with other therapies.
There are challenges to applying this new therapy, however. Blinatumomab is administered as a 28 day continuous infusion followed by a 14 day treatment free interval. This is repeated for 9 cycles, which requires hospitalization initially and medical supervision throughout the course of therapy. Severe side effects have occurred including neurological effects like convulsions, tremors, confusion, and balance disorders. Some patients have experienced an infusion reaction called cytokine release syndrome (CRS) which can be life threatening. Future research and drug development is focused on reducing the risk of CRS and other toxicities, simplifying drug administration, and increasing efficacy against tumors.