Provided are bifunctional small molecules of Formula (I): or pharmaceutically acceptable salts thereof, wherein M represents a small organic molecule which binds, covalently or non-covalently, a kinase, such as Her3 protein kinase; L1 represents a linker; and RH represents a hydrophobic group. An example of a compound of Formula (I) is a compound of Formula (II): Also provided are pharmaceutical compositions comprising a compound of Formula (I) or (II) and methods of using such compounds for treating proliferative diseases.