The theory of FBDD believes that the active pockets of many drug targets are composed of multiple subactive cavities. The fragments of the active compound obtained by HTS often cannot bind well to the subactive cavities of the target protein. The optimization of the product often affects the entire molecule, and even changes the binding position to the target, leading to loss of activity. The FBDD method connects the fragments that specifically bind to each subactive cavity of the target protein with suitable linkers to assemble them into compounds with high activity. Therefore, drugs designed by the FBDD method often have the characteristics of high activity and high selectivity.