SPOP-IN-6b is a small molecule inhibitor targeting the interaction between SPOP and its substrate proteins in the ubiquitin-proteasome system. It is primarily used in cancer research, especially in prostate and endometrial cancers where SPOP mutations are common. By disrupting the binding of SPOP to oncogenic substrates, SPOP-IN-6b helps stabilize tumor suppressor proteins that would otherwise be degraded, thereby promoting cancer cell death. It serves as a valuable tool compound for studying SPOP-dependent signaling pathways and has shown potential in restoring normal SPOP function in mutant cancer cells. Its application is mainly confined to preclinical research, aiding in the development of targeted protein degradation therapies and understanding the mechanistic role of SPOP in tumorigenesis.