The mammalian Target of Rapamycin (mTOR)-mediated signaling transduction pathway has been observed to be deregulated in a wide variety of cancer and metabolic diseases. Despite extensive clinical development efforts, the well-known allosteric mTOR inhibitor rapamycin and structurally related rapalogs have failed to show significant single-agent antitumor efficacy in most types of cancer. This limited clinical success may be due to the inability of the rapalogs to maintain a complete blockade mTOR-mediated signaling. Therefore, numerous efforts have been initiated to develop ATP-competitive mTOR inhibitors that would block both mTORC1 and mTORC2 complex activity. Here, we describe our experimental approaches to develop Torin1 using a medium throughput cell-based screening assay and structure-guided drug design.