Naming of therapeutic MABs is set out under the International Non-proprietary Names (INN) monoclonal antibody nomenclature scheme. The final syllable or stem has, until 2022, been ‘-mab’, while the start of the name – the prefix – is random and used to provide a unique drug name.⁵

Syllables that appear between the prefix and stem, that is ‘substems’ or ‘infixes’, indicate the disease context or target class. In addition, older MAB drug names would include an infix indicating the animal species source of the antibody, but the use of these for new drugs has been discontinued.⁶

With around 880 registered INN names currently ending in ‘-mab’, a new protocol for naming MABs was agreed in November 2021. Instead of ending with ‘-mab’, new MABs will use one of four new stems which provide information about modifications to the immunoglobulin structure.^1,5,6

Three of the new endings are used for different groups of monospecific immunoglobulins while one has been designated for bi- and multi-specific immunoglobulins:⁵

In addition, the revised protocol list of infixes indicating the target class now comprises:⁵