A couple of months ago I highlighted some very encouraging early work on the novel agent PF299804, an "irreversible pan-HER tyrosine kinase inhibitor".

In my last post, I described the novel oral agent PF299804 (PF299), an irreversible "pan-HER" inhibitor not only of the epidermal growth factor receptor but of other members of the human epithelial growth factor receptor (HER) family.

We've received several questions about agents that might be helpful for patients who have already responded to inhibitors of the epidermal growth factor receptor (EGFR) like Tarceva (erlotinib) and Iressa (gefitinib) and then demonstrate progression. These latter agents are reversible inhibitors of of the tyrosine kinase domain (signalling portion inside the cell) of the EGFR molecule, meaning that they attach to and periodically detach from the receptor.