These drugs were found to be cytotoxic only in multiple myeloma cells expressing CRBN (Lopez-Girona et al., 2012; Zhu et al., 2011), and it was subsequently discovered that they act by targeting essential β-hairpin-containing neosubstrates for CRBN-dependent proteasomal degradation (Jan et al., 2021). Here, CRBN is linked to plasma cell myeloma.