Rapid discovery of drug target engagement by isothermal shift assay

Identifying protein targets directly bound by drug molecules within living systems remains challenging. Here we present the isothermal shift assay, iTSA, for rapid identification of drug targets. Compared with thermal proteome profiling, a prevailing method for target engagement, iTSA offers a simplified workflow, 4-fold higher throughput, and multiplexed experimental designs with higher replication. We demonstrate application of iTSA to identify targets for several kinase inhibitors in lysates and living cells.