PD158780 is a pyridopyrimidine that is pyrido[3,4-d]pyrimidine-4,6-diamine in which the amino groups at positions 4 and 6 are substituted by a m-bromophenyl group and a methyl group, respectively. It is a potent, cell-permeable, reversible ATP-competitive inhibitor of EGFR tyrosine kinase activity [IC50 values of 0.008, 49 and 52 nM for EGFR, ErbB2 (HER2) and Erb4 (HER4)]. It does not inhibit FGF or PDGF-mediated tyrosine phosphorylation. Induces G1 cell cycle arrest in MCF10A cells and is antiproliferative in A431 human epidermal carcinoma cells. It has a role as an antineoplastic agent and an EC 2.7.10.1 (receptor protein-tyrosine kinase) inhibitor. It is a diamine, an aromatic amine, a member of bromobenzenes, a pyridopyrimidine and a secondary amino compound.