Methods of inhibiting a receptor tyrosine kinase in a subject in need thereof. Methods of inhibiting the growth of a tumor cell in a subject in need thereof. Methods of treating pancreatic cancer in a subject in need of treatment for pancreatic cancer. Methods of treating HER2 positive breast cancer in a subject in need of treatment for HER2 positive breast cancer. Methods of treating drug resistant non-small cell lung cancer in a subject in need of treatment for drug resistant non-small cell lung cancer. Each of these methods can include administering to the subject an effective amount of a compound of formula (I) or a pharmaceutically acceptable salt thereof.
