Belinostat is primarily used in the treatment of relapsed or refractory peripheral T-cell lymphoma (PTCL), a rare and aggressive type of non-Hodgkin lymphoma. It functions as a histone deacetylase (HDAC) inhibitor, which helps to regulate gene expression and induce cancer cell death. By blocking HDAC enzymes, belinostat promotes the acetylation of histones, leading to the activation of tumor suppressor genes and inhibition of cancer cell proliferation. It is administered intravenously and is often considered when other treatment options have failed. The drug is particularly valued for its ability to target cancer cells while minimizing damage to healthy cells, though it may still cause side effects such as nausea, fatigue, and low blood cell counts. Its use is typically guided by oncologists in specialized cancer treatment centers.