The Food and Drug Administration has approved Velcade to treat a type of cancer called multiple myeloma. Velcade should only be used in people who have already been treated with two other types of chemotherapy (drugs used to kill cancer cells), and whose cancer has still progressed on the most recent therapy. Velcade is a new type of cancer drug called a proteasome inhibitor. Proteasomes are enzymes found in cells, and play a role in regulating cell function and growth. Velcade blocks the activity of proteasomes. This blockade can lead to death of cancer cells.