Cleave Biosciences, the US biotechnology company, has announced that its lead drug candidate CB-5083 has been granted orphan drug designation by the US Food and Drug Administration (FDA). CB-5083 is a first-in-class oral inhibitor of p97, an enzyme involved in key aspects of protein homeostasis including non-proteasomal protein degradation. Efficient removal of protein is crucial for the growth and survival of myeloma cells but blocking protein degradation pathways is known to be an effective way of inducing cell death. CB-5083 is currently being investigated in a Phase I trial for relapsed and/or refractory myeloma patients who have had at least two prior lines of treatment including a proteasome inhibitor and an immunomodulatory drug. The new orphan drug status will help further support its development as a treatment for myeloma.