The Code Hidden in Every Drug Name

Every approved drug has two names: a brand name (like Keytruda or Humira) and a generic name (like pembrolizumab or adalimumab). The brand name is marketing. The generic name is a code.

It follows an international naming convention - the INN system, maintained by the World Health Organization - that encodes what the drug is directly into its name. The class. The mechanism. Often the target. Once you know the suffixes, you can read a drug name you've never seen before and immediately know what you're looking at.

A pharmacist in Brazil and a clinician in Japan reading the same generic name should both know what class of drug they're dealing with. That's the point of the system.

The suffix table

The WHO assigns standardized suffixes - called "stems" - to each drug class. The stem always appears at the end of the generic name. Here's what they mean:

That's most of what you need. See -mab at the end? Monoclonal antibody. -glutide? GLP-1 agonist - same class as Ozempic. -parvovec? Gene therapy delivered via an AAV viral vector.

You can do this with any drug. Pick one off a clinical trial listing, scan the suffix, and you already know more about it than most people reading the press release.

The bispecific problem

There's one place the system breaks down. Bispecific antibodies - molecules engineered to bind two different targets simultaneously - still use the -mab suffix. Because structurally, they are antibodies.

This means you can't tell a bispecific from a regular monoclonal antibody by name alone:

The only reliable way to identify bispecifics is from the FDA label text - it will say "bispecific antibody" in the mechanism of action section. The INN suffix alone won't tell you.

ADCs: two codes in one name

Antibody-drug conjugates have the most interesting naming. They carry two codes: the antibody backbone gets the -mab suffix, and the cytotoxic payload gets its own suffix.

Take trastuzumab deruxtecan (Enhertu). trastuzu-mab tells you it's a monoclonal antibody - specifically the same HER2-targeting antibody as Herceptin. -deruxtecan tells you it's carrying a topoisomerase I inhibitor payload. Together, they tell you: this is a targeted chemotherapy missile - an antibody that finds HER2-positive cancer cells and delivers a cytotoxic warhead directly to them.

If you see both an antibody suffix and a payload suffix in the same drug name, it's an ADC.

Try it yourself

Here are ten drugs. Before reading the answers, try decoding each one from the suffix alone:

The last one - venetoclax - is a small molecule BCL-2 inhibitor. Many small molecules have INN stems too (statins, -prils, -sartans), but venetoclax belongs to a newer class that doesn't have an established stem yet. When a drug name doesn't match any suffix in the table, check the mechanism of action.

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Where the system breaks

INN suffixes cover most biologics reliably, but there are gaps.

Clinical trial data has no labels. On ClinicalTrials.gov, drugs are listed by name only - no mechanism of action text. You have to rely entirely on the suffix. This means bispecifics get misclassified as regular mAbs in pipeline databases, and newer small molecule classes without established stems can't be classified at all.

New modalities outpace the naming system. The WHO periodically introduces new stems, but emerging classes like PROTACs (targeted protein degraders), RNA aptamers, and mRNA therapeutics don't yet have universally adopted INN stems. They fall into the "small molecule" or "unclassified" bucket by default.

Combination products create collisions. Fixed-dose combinations lead with the primary ingredient name. A combination of a small molecule and a peptide might trigger the peptide suffix rule even though the primary ingredient is a small molecule.

The cheat sheet

Bookmark this. Next time you see a drug name in a clinical trial listing, an SEC filing, or a press release, scan the last few letters:

The naming system isn't perfect, but it's remarkably powerful. Most people in pharma see drug names as opaque jargon. Now you can read them.