Recent topics in IMiDs and cereblon

Immunomodulatory drugs (IMiDs) are a new class of anticancer compounds that are derived from thalidomide. Lenalidomide and pomalidomide are well-known IMiDs, and they have already been approved by FDA for the treatment of several diseases, including multiple myeloma. Cereblon (CRBN) is a common primary target for IMiDs. It works as a substrate receptor of CRL4. Accumulating evidence has shown that the substrate specificity of CRL4^CRBN is altered by ligands such as IMiDs. Recently, novel CRBN-binding compounds have been developed and are called "cereblon modulators". Among these, CC-122 and CC-220 are currently under clinical development for the treatment of diffuse large B-cell lymphoma and systemic lupus erythematosus, respectively. Another new cereblon modulator CC-885 is shown to induce degradation of the translation termination factor GSPT1, resulting in an antiproliferative effect in acute myeloid leukemia. Structural analyses have revealed that CC-885 provides an interaction hotspot between CRBN and GSPT1. On the other hand, several groups have been investigating linker-based approaches for targeted protein degradation via CRBN. Several proteins, such as BRD4 and BCR-ABL, have been successfully degraded by CRL4^CRBN using these technologies. In this review, we introduce recent topics in CRBN and its binding compounds.