4-Letter Extensions on Biologics Names

Why do some of the new cancer drugs have extra letters at the end of their names? — Name withheld on request

Many of you may have noticed that newer biologic medications (such as monoclonal antibodies) have a 4-letter suffix at the end of their name (eg, caplacizumab-yhdp [Cablivi], which was approved earlier this year). You may also have noticed that these suffixes are also applied to the end of biosimilar medications.

Use of these suffixes is mandated by the US Food and Drug Administration (FDA) for new biologic medications including originator and biosimilar biologics. These suffixes are intended to make it easier for health care providers to distinguish between biologic medications made by different manufacturers (as in the case of trastuzumab, which as of this writing has 5 biosimilar products approved by the FDA, as well as the originator producer). By distinguishing between the different manufacturers, the FDA intends to be better able to monitor the safety of these products.

Of note, this new naming convention only applies to biologic medications, which is why you do not see this with every newly approved medication. Older biologic medications will not have the 4-letter suffix added, but will continue with their original names.