The Food and Drug Administration (FDA) released a draft guidance for industry, Bispecific Antibody Development Programs, in April 2019. This guidance is intended to provide developers and manufacturers with the FDA’s most current thinking regarding development programs of bispecific antibodies broadly.
Bispecific antibodies are antibodies that recognize and bind to two different targets (i.e., antigens or epitopes) on a cell’s surface. These are distinct from non-bispecific antibodies (i.e., monoclonal antibodies), which can only recognize and bind to a single target on a cell’s surface. The FDA notes that there are two categories of bispecific antibodies: those that align two distinct cells (e.g., a single antibody brings two cells in close proximity to each other to facilitate a function) and those that do not align two distinct cells. Bispecific antibodies require genetic engineering to create two distinct binding domains within the antibody, giving it the ability to bind to two distinct targets on a cell. Therapeutically, the FDA notes that bispecific antibodies could be used to attack multiple disease-causing molecules with a single drug, reducing the need for a multi-drug combination regimen.
The guidance suggests that considerations of bispecific antibody development include if the antibody antigens require simultaneous engagement, the antibody’s binding affinity to both its intended target and unintended targets, and how binding multiple targets will affect its binding affinity. The FDA then provides more specific recommendations for developing these products. Some considerations include to note the pharmacologic profiles and toxicology of the antibodies, to fully understand potential immune responses, and a reminder to test the bispecific antibody against not only a control or placebo but also a monospecific antibody during clinical trials.