(1S,2S)-Bortezomib is primarily used in the treatment of multiple myeloma and mantle cell lymphoma. It works by inhibiting the proteasome, a complex that breaks down proteins in cells. By blocking this process, it leads to the accumulation of unwanted proteins, causing cancer cells to die. This mechanism makes it particularly effective in targeting and killing cancerous cells while sparing normal cells to a greater extent. It is often administered intravenously or subcutaneously and is sometimes used in combination with other chemotherapy drugs to enhance its efficacy. Additionally, it is being researched for its potential in treating other types of cancers and autoimmune diseases, expanding its therapeutic applications.