Oprozomib (ONX 0912) is an investigational proteasome inhibitor primarily developed for the treatment of multiple myeloma, a blood cancer affecting plasma cells in the bone marrow. It functions by blocking the proteasome, a cellular complex responsible for protein degradation, resulting in the buildup of damaged or misfolded proteins. This process induces apoptosis, especially in rapidly dividing cancer cells that depend heavily on proteasomal activity for survival. Oprozomib is targeted at patients with relapsed or refractory multiple myeloma who have not responded to prior therapies. Administered orally, it provides a patient-friendly option compared to intravenous alternatives like bortezomib. Ongoing clinical trials evaluate its effectiveness as monotherapy and in combination regimens with other antineoplastic agents, demonstrating potential to enhance progression-free survival. As a second-generation proteasome inhibitor, oprozomib advances precision oncology for hematologic malignancies.