Molecular glues are expected to have better pharmacological properties than PROTACs (Figure ). In contrast to PROTACs, they are much smaller thus more easily abide by Lipinski's rule of five for drug conformity, which suggests upper limit of molecular properties expected to enhance the probability for good oral bioavailability. Because of their smaller size, they are expected to have higher membrane permeability and better cellular uptake, and in general are less likely than PROTACs to pose a significant challenge for penetration of the blood-brain barrier -an important requirement for treating central nervous system (CNS) disorders. Small molecule glues have also been shown able to reprogram the binding partners of scaffolding proteins or to enhance the endogenous interaction between two proteins. On the other hand, though, an important advantage of PROTACs is their versatility -they allow for modular design to rapidly connect one enzyme with many targets. Thus, PROTACs are relatively easy to design and the target proteins are predictable. In order to shed light on the advances in targeted protein degradation research, here we examine the publication landscape and analyze the relevant data from the CAS Content Collection , and thoroughly review both molecular glue drug candidates in targeted protein degradation through E3 ligase recruitment and the development of molecular glues in medicinal chemistry and drug discovery.