molecules of the month

Tucatinib is the third approved HER2 kinase inhibitor (after lapatinib and neratinib), but differentiates itself due to its selectivity against the closely related EGFR, which is hypothesized to be a source of undesired side effects with prior inhibitors. Impressively, it’s also demonstrated activity in HER2+ breast cancers with brain metastases. Chemically, it’s got an interesting, uncommon oxazoline unit, and three pretty electron-rich aromatic rings which don’t seem to have prevented tucatinib’s administration as an oral BID drug. However the drug label does note hepatotoxicity as an uncommon adverse event contributing to ~8% of patients needing dose reductions and 1.5% discontinuing the drug.