Targeting STAT3 with proteolysis targeting chimeras (PROTACs) and next generation antisense oligonucleotides.

Signal transducer and activator of transcription 3 (STAT3) has been recognized for its key role in the progression of cancer, where it is frequently upregulated or constitutively hyperactivated, contributing to tumor cell proliferation, survival, and migration, as well as angiogenesis and suppression of anti-tumor immunity. Given the ubiquity of dysregulated STAT3 activity in cancer, it has long been considered a highly attractive target for the development of anti-cancer therapies. Efforts to target STAT3, however, have proven to be especially challenging, perhaps owing to the fact that transcription factors lack targetable enzymatic activity and have historically been considered "undruggable". Small molecule inhibitors targeting STAT3 have been limited by insufficient selectivity and potency. More recently, therapeutic approaches that selectively target STAT3 protein for degradation have been developed, offering novel strategies that do not rely on inhibition of upstream pathways or direct competitive inhibition of the STAT3 protein. Here, we review these emerging approaches, including the development of STAT3 proteolysis targeting chimera (PROTAC) agents, as well as preclinical and clinical studies of chemically stabilized antisense molecules, such as the clinical agent AZD9150. These therapeutic strategies may robustly reduce the cellular activity of oncogenic STAT3 and overcome the historical limitations of less selective small molecules.