Guide on monoclonal antibody naming

There is a naming system for monoclonal antibody naming that consists of 3 elements. Each name consists of a first, middle, and last element, also referred to as prefix, infix, and suffix. Recently, the WHO introduced changes in monoclonal antibodies nomenclature that affect the naming of the infix and suffix. The recent nomenclature of monoclonal antibodies (mAbs) will not change the names of mAbs already on the market but will have an impact on the naming of new drugs. We use the word drug intentionally since it also applies to artificially engineered antibodies and antibody fragments.

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What is the new naming scheme for antibodies?

Let’s start with the recent changes in the nomenclature of monoclonal antibodies. All monoclonal antibodies before December 2021 have the -mab suffix, to indicate the type of antibody. The biggest change in the new nomenclature is this suffix, that now provides more information on the antibody (Ab) or antibody fragment. With over 880 monoclonal antibodies in clinical use today, they form the largest group of biological products. In recent years, more and more antibody fragments and antibody derivatives are being developed, increasing the need for further segmentation of the -mab group. Good to know already, the suffix mab will no longer be used. Instead, one of the new suffixes in the monoclonal antibody naming scheme will be chosen.

Monoclonal antibody naming scheme for replacing the word -mab

The distinction in names in the current monoclonal antibody naming convention is divided into four groups. What is the suffix for antibody nomenclature? As stated earlier, current drugs on the market will keep the mab suffix. For new drugs, the mab nomenclature will cease to exist and will be replaced by -tug, -bart, -mig, or -ment. We will explain each of the replacements in the next paragraphs.

Group 1: -tug antibodies

Tug stands for Unmodified Immunoglobulin. Immunoglobulins are another name for antibodies. This suffix is added to monoclonal antibodies that:

are unmodified;
are monospecific;
are of full length;
have unmodified Fc regions (Fragment crystallizable region);
are allelic;
are glycoengineered without mutation;
have C-terminal lysine deletion without other mutations on the Fc domain.

Group 2: -bart antibodies

Bart is short for antiBody fragment ARTificial, meaning artificially engineered. An antibody drug with a name ending with -bart, is a full-length monospecific immunoglobulin. But to use the -bart suffix, all or any of the following requirements should be met.

has engineered constant domains;
is changed anywhere in the hinge region;
has changes in glycosylation sites;
is an unnatural mixed allelic variant;
has modified complement binding (Neonatal Fc Receptor (FcRn), Fc gamma receptor).

Group 3: -mig antibodies

Mig stands for Multi-ImmunoGlobulins, indicating that these are bi- or multispecific Abs, and therefore very different from -bart or -tug Abs. Criteria to fall under this monoclonal antibody nomenclature are:

the antibody needs to contain two antigen binding domains created by protein engineering;
does not have to be a full-length antibody but can also be a fragment or extended antibody.

Please note: this monoclonal antibodies naming convention is not used for fusions with anything else than variable domains.

Group 4: -ment antibodies

The -ment suffix indicates that the drug is an antibody fragMENT. This suffix is added to monospecific antibodies, since bi- or multispecific antibodies fall under the third group. The -ment suffix is added to compounds derived from the variable domain of antibodies.

Infix in monoclonal antibody naming changes January 2022

The suffix has changed completely, but there are also some minor changes on the infix regarding the target substem as of January 2022. The complete list can be found in the mab monoclonal antibody nomenclature chart at the end of this article. Below we only indicate the changes in the infix.

-ki- will be used for antibodies targeting cytokine (receptor), this was formerly interleukin
-ler- indicates allergen
-sto- indicates immunostimulatory
-pru- indicates immunosuppressive

Antibody naming convention changes over the years

The International Nonproprietary Names (INN) nomenclature convention has changed over the years. It is valuable to know the recent changes, as existing names of antibody drugs already on the market have remained the same. To quickly obtain information on an existing antibody drug, it is still relevant to know the meaning of monoclonal antibody naming from before the changes. The most important changes are listed below.

Species infix (used until 2017)

Infixes A and B are a code that indicates the target and origin of antibody. The first letter before the suffix (infix B) indicates the nature (species) of the antibody. Infix B was used until 2017. For reference, you find the complete list of species in monoclonal antibody naming below, with the note that this is no longer in use.

A = rAt
E = hamstEr
I = prImate
O = mOuse
U = hUman
XI = chimeric (part human/part foreign)
ZU = hUmaniZed (a humanized antibody uses only the receptor of mice, the rest is human)

Combinations of origin:

XIZU = Chimeric/Humanized hybrid
AXO = Rat/Mouse hybrid
VET = Veterinary use*

*VET is still being used today, but as a target infix, placed pre-stem (pre-suffix).

Example change of naming convention for mAbs

Rituximab is a chimeric antibody against tumors. Chimeric, as you can see it has -xi- in the name. If this drug were named today, it would not have -xi-, nor would it have -mab. Also -tu- is no longer used to indicate the target tumor, this has been replaced by -ta-. So, what would be the name of Rituximab today?

Rituximab would become Ritatug if it had been named after January 2022.

Monoclonal antibody naming: target infix

There have been many small changes in the target substem (infix). When conducting research on antibody naming, there are a few things to consider. First of all, up to 2017 the last letter of a target infix could be omitted if this resulted in a name that would have been difficult to pronounce. For example, target cardiovascular could be written as -cir- or -ci-. In the naming convention from 2017 this became outdated. Secondly, some substems became deprecated over the years. You can find them in the list below.

All outdated target substems for mAbs (from 2022 and before)

-anibi- angiogenesis (inhibitor)
-les- inflammatory lesions
-li(m)- / -l(i)- immunomodulating, has been replaced by subclasses:

-ler- allergen
-pru- immunosuppressive
-sto- immunostimulatory

-mul- musculoskeletal system

Tumor code for monoclonal antibody naming

Up to 2009, there was a division in tumor type. Between 2009 and 2017 different types were accommodated in one substem; -t(u)-. From 2017 and onwards -t(u) has been replaced with -ta-. For reference, the outdated tumor substems with their meaning are listed below.

Co(l) colonic tumor
go(t) testicular tumor
go(v) ovarian tumor
ma(r) mammary tumor
me(l) melanoma
pr(o) prostate tumor
tu(m) miscellaneous tumor

Why was tumor type in monoclonal antibody naming removed?

As we at TRACER can tell from our clinical trial experience, novel drugs often target various tumor types. When drafting the clinical trial design, we will discuss this with the drug developer. Namely, by including multiple indications in the Phase 0 clinical trial, the effect of a compound on multiple tumor types can be measured. A Phase 0 clinical trial, which is the first-in-human trial, comes before Phase I. Phase 0 trials are conducted on patients that have various types of cancer. This is a huge advantage over Phase I, which is conducted on healthy volunteers. Phase 0 provides efficacy data in relation to indication that you can later use in Phase 2.

Benefits of Phase 0 clinical trials conducted by TRACER

There are many benefits of choosing Phase 0 over Phase 1, to name a few:

Decrease time and resources spent on preclinical drug development.
Skip large animal models.
Start the clinical trial process from GLP material.
Increase chances of success in subsequent clinical trials.
Obtain visual PK/BD data on a cellular level by molecular imaging during your clinical trial.

Are you a drug developer and would you like to obtain more information on Phase 0? Contact us today. Send an e-mail to info@tracercro.com or schedule your meeting.

Monoclonal antibody nomenclature chart (2021)

As per the guidelines in the new INN nomenclature for monoclonal antibodies, monoclonal antibodies drug names consist of: [random name] [target infix] [group code].

The first part is a random name and can be chosen by the pharmaceutical company or drug developer. For more on this, read the next paragraph on prefix guidelines. The other parts of the name are listed below in the monoclonal antibody nomenclature chart (2021)

Prefix	Infix	Infix (target) meaning	Suffix	Suffix (mAb group) meaning
Chosen by company	ami	serum amyloid protein (SAP)/amyloidosis (pre-substem)	tug	unmodified Ab
	ba	bacterial	bart	artificial Ab
	ci	cardiovascular	mig	bi- or multispecific Ab
	de	endocrine	ment	Ab fragment
	eni	enzyme inhibition
	fung	fungal
	gro	skeletal muscle mass related growth factors and receptors (pre-substem)
	ki	cytokine and cytokine receptor
	ler	immunomodulating allergen
	pru	immunomodulating immunosuppressive
	sto	immunomodulating immunostimulatory
	ne	neural (nervous system)
	os	bone
	ta	tumor
	toxa	toxin
	vet*	veterinary use (pre-stem)
	vi	viral

*the term -vet- is used as a second infix, for instance -ta-vet- meaning tumor target for veterinary use.

Download mAb Nomenclature (PDF)

Good to know: drug name prefix

The prefix should contain two syllables and should not conflict with existing names. Only the Roman alphabet is used, without the letters Y, H, K, J, and W since they are not used globally. Promotional text or company references are prohibited. Referring to a medical indication should be avoided since the drug might work on other indications as well.

For example, as a drug developer in the US multiple names can be submitted to the USAN Council. USAN stands for United States Adopted Names and this council reviews the names for pharmaceutical products. If the USAN Council does not approve any of the names, it can suggest a name. After submission and approval of the name by the World Health Organization (WHO), the name is submitted to the INN register. Please note that countries can have their own naming registers, for example, Denominazione Comune Italiana (DCIT), British Approved Name (BAN), Australian Approved Name (AAN), and Japanese Accepted Name (JAN).

For Dutch pharmaceutical products, the nomenclature can be found here: https://english.cbg-meb.nl/documents/policy-documents/2023/01/01/meb-13-nomenclature-of-pharmaceutical-products

PAB suffix antibodies

You sometimes see a drug name ending on -pab. What does pab mean? In INN guidelines there is no suffix -pab. This is because -pab is used for a polyclonal mix of recombinant antibodies. Pab stands for Polyclonal antibody. An example Rozrolimupab, spelled out consists of prefix rozo-, has target -lim- (immunomodulating), -u- stands for human, and -pab indicates that it is a polyclonal antibody.

Invented name (brand name drug)

A drug has a generic name, as regulated by INN guidelines, but can also have a brand name. For brand name drugs or invented names, it is not allowed to end the name with a letter combination from the official INN scheme. For instance, names ending in -mab are not allowed, since it is used as a drug name for monoclonal antibodies according to INN. Keep in mind that in addition to the suffix mab drugs, there are more groups. An overview can be downloaded in pdf: https://cdn.who.int/media/docs/default-source/international-nonproprietary-names-(inn)/stembook-2018.pdf

Good to know when naming your drug: It is wise to evaluate a chosen name in different languages to avoid confusion. If you are a drug developer determining a name, be aware that using capital(s) in the middle of a word or writing the name or a part of the name in capital is not recommended.

FAQ antibody nomenclature

You now know that the monoclonal antibodies suffix and infix are determined by strict guidelines. Below are some frequently asked questions on the subject of monoclonal antibody naming and drug naming in general.

How do monoclonal antibodies get named?

The infix and suffix for monoclonal antibodies are based on guidelines for the INN, combined with a chosen prefix. Apart from this, there is a tradename that the pharmaceutical company gives to the drug. How are monoclonal antibodies named? There are three levels of naming, the first is already heavily discussed for antibodies in this article. It is the name registered to the INN. Another is the tradename or brand name. But before any of those names are given, there is a study name. This is mostly a few letters like PF, for example, indicating Pfizer, followed by some numbers to provide a unique name.

What is the benefit of the monoclonal antibodies nomenclature?

The generic name is given to ensure a drug is identifiable everywhere in the world. This name comes from the World Health Organization (WHO) INN. This name is also a coded description for professionals to obtain information about the drug. When considering mab suffix medication, the generic name already provides information on the indication. It also prevents confusion when a drug is available under more than one trade name.

A good example is the Nimotuzumab brand name. Nimotuzumab can also be found in:
TheraCIM® h-R3, Theraloc®, CIMAher® (Cuba), BIOMAb-EGFR®, Tai Xin Sheng® (Chinese trade name), OSAG 101 (trial number), YMB 1000 and more.

What does the drug suffix mAb mean?

The suffix mAb stands for monoclonal antibody. Keep in mind that often parts of the infix are mistaken as suffixes. For instance, people are questioning, why do drug names end in Umab? Or what does Zumab mean? To explain quickly; -u-mab means human monoclonal antibody, while -zu-mab means humanized antibody. The new INN regulations are better to understand, both the infix for origin as -mab suffix is removed.

What is the suffix for antibody nomenclature?

What is the suffix for most monoclonal antibodies? Now and in the near future the most mAbs on the market will use the mab prefix. For new drugs coming to the market, the new nomenclature will be used. Drug developers send in the name of the drug earlier than approval for market, so even FDA-approved monoclonal antibodies in 2023 can still have the mab suffix.