Iressa (originally coded ZD1839) is a drug used in the treatment of certain types of cancer. Acting in a similar manner to erlotinib (marketed as Tarceva), iressa selectively targets the mutant proteins in malignant cells. It is marketed by AstraZeneca under the trade name Iressa.
Iressa inhibits the intracellular phosphorylation of numerous tyrosine kinases associated with transmembrane cell surface receptors, including the tyrosine kinases associated with the epidermal growth factor receptor (EGFR-TK). EGFR is expressed on the cell surface of many normal cells and cancer cells.
The acute toxicity of iressa up to 500 mg in clinical studies has been low. In non-clinical studies, a single dose of 12,000 mg/m2 (about 80 times the recommended clinical dose on a mg/m2 basis) was lethal to rats. Half this dose caused no mortality in mice. Symptoms of overdose include diarrhea and skin rash.