The role of E3 ubiquitin ligase in multiple myeloma: potential for cereblon E3 ligase modulators in the treatment of relapsed/refractory disease

Introduction Insights into the mechanisms of protein homeostasis and proteasomal degradation have led to new strategies of redirecting the ubiquitin–proteasome system (UPS) to reduce or eliminate proteins or survival factors key to malignant pathobiology, multiple myeloma (MM) in particular. These strategies have enabled researchers to target proteins that were previously considered difficult to modulate by pharmacological means.Areas covered This review provides a brief overview of UPS biology, particularly the role of the CRL4CRBN E3 ubiquitin ligase complex, and summarizes current strategies for co-opting the UPS, including CELMoD compounds, SNIPERs, PROTACs, and degronimids. A detailed discussion is provided on lead CELMoD compounds iberdomide and mezigdomide, which are currently being evaluated in clinical trials in patients with MM.Expert opinion Since a high proportion of patients develop drug resistance, it is vital to have novel therapeutic agents for treating relapsed patients with MM more effectively. It is encouraging that the expanding pathophysiological insight into cellular signaling pathways in MM increasingly translates into the development of novel therapeutic agents such as targeted protein degraders. This holds promise for improving outcomes in MM and beyond.