PBS-119

PBS-119 is a potent and selective small molecule inhibitor of the immunoproteasome, specifically targeting the **low molecular mass polypeptide 7 (LMP7)** subunit, also known as **proteasome subunit beta type-8 (PSMB8)**. Developed by **Pebble Biosciences**, the compound was designed to treat hematological malignancies, such as multiple myeloma, and potentially various autoimmune disorders. By selectively inhibiting the immunoproteasome over the constitutive proteasome, PBS-119 aims to induce apoptosis in malignant hematopoietic cells while minimizing the systemic toxicity often associated with non-selective proteasome inhibitors like bortezomib. The mechanism involves disrupting protein homeostasis and activating the unfolded protein response (UPR) pathway, leading to programmed cell death in cancer cells that are highly dependent on proteasome function.