Monoclonal Antibody Nomenclature: Understanding the Changes

Monoclonal antibodies (mAbs) are biologic medicines that bind to specific antigens with high specificity. The targets for these proteins are varied and include cancer cells, inflammatory mediators, and pathogens. Their use has grown considerably over the past few years with an expanding range of indications.

It is important to identify medicines that fall into this category as mAbs often have specific requirements for storage, administration, and monitoring. Currently, these medicines can be easily identified by the suffix -mab. However, this suffix has been discontinued and mAbs named after 2021 will no longer end in -mab.

Naming conventions

Biological medicines supplied in Australia are identified using the Australian Approved Biological Name. This name is invariably an international non-proprietary name (INN), supplied by the INN committee of the World Health Organization (WHO). In the absence of an INN, an appropriate name is agreed between the sponsor of the new medicine and the Therapeutic Goods Administration (TGA) during the medicine registration process.

Monoclonal antibody names follow a structured naming convention established by the WHO. The original system, introduced in 1991, assigned all mAbs the suffix –mab (e.g. adalimumab, infliximab). However, a large number of mAbs with increasing structural complexity have been developed since then which has led to various revisions of the nomenclature system.

Original naming pattern: Prefix + Target Substem + Source Substem + Suffix

1. Prefix

• Unique and arbitrary
• Helps distinguish between drugs

2. Target Substem

Indicates what the antibody targets:

• -tu-: tumour (e.g., cancer therapies)
• -li-: immune system (e.g., inflammatory diseases)
• -vi-: viral targets

3. Source Substem

Historically indicated how “human” the antibody is:

• -o-: murine (mouse)
• -xi-: chimeric
• -zu-: humanized
• -u-: fully human

4. Suffix

• -mab: identifies the drug as a monoclonal antibody

Example: Adalimumab

• ada- (prefix)
• -li- (immune system target)
• -u- (fully human)
• -mab (monoclonal antibody)

This tells us that adalimumab is a fully human monoclonal antibody targeting the immune system.

Recent Changes to Nomenclature

In recent years, the WHO has simplified mAb naming by removing the source substem (e.g., -xi-, -zu-). This change reflects advances in biotechnology and reduces confusion, as most modern antibodies are highly humanised regardless of classification.

While mAbs have previously shared the common suffix -mab, this naming system has become unsustainable. With over 800 mAbs already named using “-mab”, it has become increasingly harder to create distinct, recognisable, and clinically meaningful names. Secondly, the structural diversity of this drug class has also increased (e.g., fragments, bispecific antibodies, engineered constructs), making the single suffix overly simplistic.

In response, the WHO formally revised the INN system in 2021, eliminating the universal “-mab” suffix for new agents. Medicines named prior to 2021 retain their original names..

The New Naming System

Under the updated INN scheme, monoclonal antibody-based therapies are now grouped into four categories, each with a unique suffix that reflects structure and function:

1. -tug → Unmodified immunoglobulins

• Full-length antibodies with no engineered changes in constant regions
• Structurally closest to naturally occurring antibodies

2. -bart → Engineered (artificial) immunoglobulins

• Full-length antibodies with intentional modifications (e.g., altered Fc function, glycoengineering)

3. -mig → Multispecific antibodies

• Includes bispecific or multispecific constructs
• Designed to bind multiple targets simultaneously

4. -ment → Antibody fragments

• Includes partial antibodies or fragments lacking full Fc regions
• Often used for improved tissue penetration or specific targeting

These four suffixes will be used in place of the suffix mab for all mAbs approved after 2021.

There are also some new infixes which denote the target, as shown in the updated list below:

• ami – serum amyloid protein (SAP)/amyloidosis
• ba – bacterial
• ci – cardiovascular
• de – endocrine
• eni – enzyme inhibition
• fung- fungal
• gro – skeletal muscle mass related growth factors & receptors
• ki – cytokine & cytokine receptor (formerly: interleukin)
• ler – immunomodulating allergen
• pru – immunomodulating immunosuppressive
• sto – immunomodulating immunostimulatory
• ne – neural
• os – bone
• ta – tumour
• toxa – toxin
• vet – veterinary use
• vi – viral

While the infix can provide an idea of how the drug works, it is important to remember that this is assigned according to the proposed mechanism of action at the time of naming. The mechanism of action may not be completely understood at that time and may vary by indication.

The new naming structure follows the pattern of: Prefix + infix + suffix

• Prefix: unique, arbitrary (chosen by pharmaceutical company for distinctiveness)
• Infix: may indicate therapeutic target
• Suffix: indicates structural class

The pipeline for biologics is rapidly expanding. Many investigational therapies already use the new naming scheme. For example, etentamig is currently being evaluated in phase 3 clinical trials for the treatment of relapsed or refractory multiple myeloma.

Understanding the new naming conventions helps to avoid confusion once these drugs reach clinical practice.

Conclusion

The shift away from the “-mab” suffix reflects the evolution of mAb therapies, which have emerged as a diverse and complex class of medicines.

While the naming changes occurred in 2021, the average clinical development time for mAbs is around six to nine years. As a result, the full impact of this naming system is only beginning to emerge and will become increasingly relevant in clinical practice as new therapies are approved.