Tbo-filgrastim is a prescription medication used to in adults with certain types of cancer who are taking chemotherapy medicines that cause a severe decrease in the production of neutrophils in the bone marrow. Neutrophils are a type of white blood cell. Tbo-filgrastim belongs to a group of drugs called colony stimulating factors, which work by  stimulating the cells to grow and divide into white blood cells to decrease the duration of severe neutropenia (low level of neutrophils in the blood).