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Guidelines on the Use of International Nonproprietary Names (INNs) for Pharmaceutical Substances
(1997; 41 pages) View the PDF document
Table of Contents
Open this folder and view contents1. General introduction
Open this folder and view contents2. Elements in the INN system
Open this folder and view contents3. Principles for selection of INNs
View the document4. Protection of INNs
Open this folder and view contents5. How to apply for an INN
View the document6. References for supporting material
View the documentAnnex 1: Background information on the INN programme
View the documentAnnex 2: General principles for guidance in devising international nonproprietary names for pharmaceutical substances
View the documentAnnex 3: List of common stems used in the selection of INNs
View the documentAnnex 4: Specific groups of biological compounds
View the documentAnnex 5: WHA46.19 - Nonproprietary names for pharmaceutical substances
View the documentAnnex 6: Procedure for the selection of international nonproprietary names for pharmaceutical substances
View the documentAnnex 7: Applications for INNs through national authorities (addresses)
View the documentAnnex 8: INN request form

Annex 4: Specific groups of biological compounds

Peptides, glycopeptides, proteins and glycoproteins (general approach)

The INN experts have adopted the following general scheme for the naming of peptides/proteins:

1. selection of a stem for the main compound, e.g. -poetin (for erythropoietin derivatives), -irudin (for hirudin derivatives), -cog (for blood coagulation factors);

2. designation of subgroups by expanding the stem, e.g. -eptacog, -octacog;

3. selection of a random prefix for compounds with differences in aminoacid sequence;

In addition for glycosylated compounds:

4. selection of a Greek letter spelt out as a second part of a two-word name for glycosylated compounds with identical amino acid sequence and different glycosylation pattern.

Blood coagulation factors

The following stems, infixes and suffixes, have been selected up to date for recombinant blood coagulation factors:

blood coagulation factors: -cog


factor VII:



factor VIII:



factor IX:


A prefix will be necessary if the amino acid sequence does not match that of the naturally occurring material. In accordance with the general policy, alfa, beta, etc., will be added for the glycoproteins. When the additional statement “activated” is needed, i.e. for the blood coagulation factor Vila, it should be spelt out in full and added in parenthesis after the name.

Colony stimulating factors

A general stem for all colony stimulating factors was selected and substems for the various categories were designated:

colony stimulating factors: -stim


combination of two different types of colony stimulating factors:



granulocyte colony stimulating factor (G-CSF) type substances:



granulocyte macrophage colony stimulating factor (GM-CSF) type substances:



macrophage stimulating factor (M-CSF) type substances:



interleukin-3 analogues and derivatives:



The common stems for enzymes, in general, is -ase. Substems are referring to the origin of the substances, e.g. tissue plasminogen activator and urokinase-type plasminogen activators.

enzymes: -ase


enzyme with superoxide dismutase activity:



tissue-type plasminogen activators:



urokinase-type plasminogen activators:


Further examples of enzymes may be found in WHO/PHARM S/NOM 15


In the case of erythropoietins it was decided to select epoetin together with a Greek letter to differentiate between compounds of the same amino acid sequence as human erythropoietin which vary in the glycosylation pattern. INNs with different amino acid sequence will be named using the -poetin stem and a random prefix.

erythropoietin type blood factors: -poetin

Growth factors

The general stem assigned for growth factors is -ermin. Substems allow distinction between the various types of growth factors, for example epidermal growth factors, fibrinoblast growth factors and insulin-like growth factors.

When selecting a name for tumor necrosis factors (TNF) these were also classified as growth factors.

growth factors: -ermin


epidermal growth factors:



fibrinoblast growth factors:



tumor necrosis factors (TNF):



platelet-derived growth factor:



insulin-like growth factors:



transforming growth factor:


Growth hormones

The characteristic stem for this group of compounds is the prefix som-. For substances other than human, suffixes are added to indicate the species specificity of the structure are as follows:

growth hormones: som-


bovine-type substances:



porcine-type substances:



salmon-type substances:


Hirudin analogues

Hirudin is a well-established name for an anticoagulant isolated from medicinal leeches. Hirudin analogues are non-glycosylated polypeptides produced by recombinant biotechnology. The stem -irudin will be used for hirudin compounds, a random prefix will allow to differentiate for different amino acid sequences.

hirudin analogues: -irudin

Hormone release stimulating peptides

The common stem selected for hormone release stimulating peptides is -relin. INNs for hormone-release inhibiting peptides should include the stem -relix.

hormone-release stimulating peptides: -relin


growth hormone release stimulating peptides:



thyrotropin releasing hormone analogues:


hormone-release inhibiting peptides: -relix


The first general stem selected for interleukins was -leukin, which was derived from the name interleukin assigned by the International Union of Biochemistry (IUB) - International Union of Pure and Applied Chemistry (IUPAC) - Joint Commission on Biochemical Nomenclature (JCBN). Randomly assigned prefixes should distinguish between the different compounds.

Based on the needs for naming further interleukins, the following stem system was accepted for recombinant interleukins:


INN stem













receptor antagonist:




It was agreed to publish the INNs for glycosylated interleukins with alfa, beta, etc, in accordance with the general policy for naming glycosylated proteins.

Pituitary hormones

The name selected by the IUPAC-IUB have, to date, been chosen for compounds with identical amino acid sequence as the naturally occurring human hormone. Addition of a Greek letter as second name will allow to differentiate for different glycosylation pattern for compounds produced by biotechnology.

The following scheme is at present in use:

pituitary hormones: -tropin


follicle stimulating hormones:



luteinizing hormones:


Monoclonal antibodies

The following scheme for common stems has been developed for naming monoclonal antibodies:

I. General stem:


II. Sub-stems for source of product:






















The distinction between chimeric and humanized antibodies is as follows:

A chimeric antibody is one that contains contiguous foreign-derived amino acids comprising the entire variable region of both heavy and light chains linked to heavy and light constant regions of human origin.

A humanized antibody has heavy (H) and light (L) chain variable (V) regions, consisting of the amino acids comprising the complementarity-determining region (CDR) segments (and possibly frameword residues) from foreign antibodies inserted appropriately among variable regions framework segments of human-derived amino acid residues, linked to H and L constant regions of human origin.

III. Sub-stems for disease or target group:











infectious lesions



























Whenever there is a problem in pronunciation, the final letter of the sub-stems for diseases or targets may be deleted, e.g. -co(l)-, vi(r), li(m), etc.

IV. Prefix:


The prefix should be random, e.g. the only requirement is to contribute to a euphonious and distinctive name.

IV. Second word:


If the product is radiolabelled or conjugated to another chemical, such as a toxin, identification of this conjugate is accomplished by use of a separate, second word or acceptable chemical designation. For monoclonals conjugated to a toxin, the tox- stem must be included as part of the name selected for the toxin.


If the monoclonal antibody is used as a carrier for a radioisotope, the latter will be listed first in the INN, e.g. technetium (99mTc) pintumomab.


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