erlotinib
Meaning of erlotinib: A daily tablet that switches off a growth signal on the cancer cell surface, working best where one specific mutation is present.
Definition of erlotinib
Erlotinib is a targeted cancer drug taken as a tablet that blocks the epidermal growth factor receptor, a switch on the cell surface instructing cells to grow and divide. It is used in non-small cell lung cancer, particularly where the tumor carries an activating change in that receptor, and in advanced pancreatic cancer alongside gemcitabine.
What does it block?
The epidermal growth factor receptor spans the cell membrane. Outside the cell it waits for a growth signal to arrive. Inside, it carries an enzyme region called a kinase, which switches on when the signal is received and passes the instruction inward by attaching phosphate groups to other proteins. Erlotinib slots into the pocket where that enzyme normally binds its fuel molecule, so the switch cannot fire and the instruction to grow never reaches the nucleus.
Why does the mutation matter so much?
Some lung tumors carry a change in the gene for this receptor that leaves the switch permanently on. Those tumors come to depend on the signal entirely, a state described as oncogene addiction, and blocking it collapses the whole arrangement.
| Tumor | Typical response |
|---|---|
| Activating receptor mutation present | Marked and often rapid shrinkage |
| No such mutation | Modest benefit at best |
Testing tumor tissue for that mutation before starting is therefore standard in non-small cell lung cancer, and the result decides whether this class of drug is worth using at all.
Why does it stop working?
Response is usually measured in months rather than years. A tumor is a mixed population, and cells carrying a further change that restores the growth signal are gradually selected for. The commonest escape route is a second mutation in the same gene that prevents the drug from binding. Others switch to an alternative growth pathway altogether. Repeat testing when the disease progresses shows which route has been taken, and later drugs in the class were designed specifically against the commonest one.
What side effects does it cause?
The same receptor is abundant in skin and in the lining of the gut, so blocking it produces a characteristic acne-like rash across the face and upper body along with frequent loose stools. The rash is not an allergy, and its appearance is associated with a better response. Dry skin, inflamed nail folds and sore eyes occur. In pancreatic cancer the drug adds only a small amount to chemotherapy, which is why its use there is limited. Rare but serious inflammation of the lungs is the effect that receives the closest attention.
Also known as
Used in a sentence
Erlotinib was started after tumor testing confirmed an activating receptor mutation.
Good to know
Benefit depends heavily on whether the tumor carries an activating mutation in the epidermal growth factor receptor, so tissue testing normally precedes treatment.