Cereblon (CRBN)

Class

Cereblon E3 ubiquitin ligase modulator (molecular glue degrader)

Pathway

CRBN-based targeted protein degradation, the same mechanistic family as IMiDs (thalidomide/lenalidomide/pomalidomide) and next-generation CELMoDs

Cereblon (CRBN) is the substrate-recognition subunit of a large multi-protein machine, the CRL4 E3 ubiquitin ligase complex, whose normal job is to select proteins for tagging with ubiquitin, a small protein mark that directs them to the proteasome for destruction. Certain small molecules, known as molecular glue degraders, bind a pocket on CRBN and reshape its surface so that it recognizes and recruits proteins it would not normally bind, called neosubstrates, marking them for degradation. This differs fundamentally from classical drugs that simply block a protein's activity: it eliminates the protein entirely, including forms that are otherwise difficult to inhibit directly. The founding members of this drug family, the immunomodulatory imide drugs, and newer chemically optimized successors (CELMoDs) exploit this glue mechanism to remove transcription factors and other regulatory proteins important in blood cell development and immune signaling. Because the degradation event is catalytic rather than stoichiometric, one drug molecule can direct destruction of many target protein copies, allowing potent effects at low exposure. This mechanism is broadly relevant in hematologic malignancies and in immune-modulation contexts where selective removal of specific regulatory proteins can reshape cell behavior.