What to know about granulocyte colony stimulating factor (G-CSF)

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A G-CSF is a drug that doctors prescribe for treating neutropenia. Neutropenia is a condition that causes a person’s white blood cell level to drop below normal.

White blood cells can drop in people with some types of cancer and those taking certain medications, such as chemotherapy.

People undergoing leukapheresis — a procedure that collects stem cells from the blood — may also require G-CSF treatment. G-CSF moves hematopoietic stem cells, which will go on to form blood cells, from the bone marrow into the bloodstream.

People who need to take G-CSF will receive a subcutaneous injection or intravenous infusion. Doctors administer subcutaneous injections under the skin, whereas intravenous infusions require injections directly into the vein over a period of time.

G-CSF drugs are a type of protein called glycoproteins. They target hematopoietic cells stored in the bone marrow. G-CSF promotes the growth and development of these cells into different types of blood cells, including white blood cells.

G-CSF is available as a biological medication called filgrastim (Neupogen) or as a biosimilar. There are three types of biosimilars:

• filgrastim-sndz (Zarxio)
• filgrastim-aafi (Nivestym)
• tbo-filgrastim (Granix)

Biosimilars are copies of biologic drugs, similar to how generic drugs are copies of brand name drugs.

Doctors can prescribe G-CSF drugs for different uses, although these vary depending on the specific drug.

Doctors prescribe Granix for people 1 month and older to lower the duration of severe neutropenia in people with certain types of cancer who are taking drugs that lower white blood cell levels.

Neupogen, Zarxio, and Nivestym have more extensive uses. Doctors can prescribe these drugs for:

• lowering the risk of neutropenia in people taking cancer drugs that lower white blood cell levels
• decreasing the risk and duration of complications of neutropenia in people with acute myeloid leukemia who are receiving chemotherapy
• reducing the duration of neutropenia and its complications in people with cancer undergoing bone marrow transplantation after chemotherapy
• moving hematopoietic stem cells from the bone marrow into the bloodstream for people who are undergoing leukapheresis
• reducing the risk and duration of complications of neutropenia in people with non-cancer-related neutropenia

Lastly, doctors can prescribe Neupogen to increase the survival of people who have exposure to large doses of radiation.

Doctors will monitor people receiving G-CSF for fever and check their level of white blood cells. These are two factors that researchers have tested when studying the efficacy of G-CSF.

Researchers studied the effect of Neupogen on people receiving chemotherapy treatments that destroy cells in the bone marrow. Treatment with Neupogen caused clinically significant reductions in the chances of getting an infection due to neutropenia.

There was also a decreased incidence of fever, as well as a rise in the person’s white blood cell count.

In clinical studies of the effectiveness of Granix, the drug was superior to placebo in reducing the duration of severe neutropenia.

Common side effects that people may experience when taking G-CSF include:

• fever
• pain
• rash
• cough
• difficulty breathing
• nosebleeds
• bone pain
• headaches
• anemia
• diarrhea
• hair loss
• changes in skin sensation

The manufacturers also warn of several health risks of using G-CSF drugs. These include:

• ruptured spleen, which causes significant blood loss and can be fatal
• acute respiratory distress syndrome, a lung condition that causes fluid to leak into the lungs
• serious allergic reactions, which can include anaphylactic shock
• sickle cell crisis, a condition that occurs in people with sickle cell disease, causing moderate-to-severe pain and swelling of the hands and feet
• glomerulonephritis, or inflammation of the glomeruli of the kidneys, which reduces the function of these organs and causes fluid buildup and hypertension
• myelodysplastic syndrome and acute myeloid leukemia, which are forms of blood cancer

Doctors must mention to patients the risks of G-CSF treatment causing abnormalities in chromosomes and cancer of the blood. They will also monitor people taking G-CSF treatments for signs and symptoms of myelodysplastic syndrome and acute myeloid leukemia.

These risks of G-CSF treatment may be more significant in people who have severe chronic neutropenia and those born with neutropenia.

Filgrastim is a biologic drug that comes in the form of a sterile solution for injection. The cost may depend on the purchasing pharmacy and whether the person has health insurance. As the drug is available in biosimilar forms, people can ask their pharmacist which biosimilar is cheapest.

The format of the drug may also influence the cost. Vials of medication that doctors extract with a syringe are typically not as expensive as pre-filled syringes.

Granulocyte colony stimulating factor (G-CSF) is a type of drug that doctors prescribe to manage neutropenia, which is the term for a lower-than-normal white blood cell count. People with neutropenia are at a higher risk of infection.

Some cancers and certain types of chemotherapy can destroy white blood cells. Sometimes, though, doctors do not know why a person’s white blood count drops below normal. G-CSF is effective in raising white blood cells and reducing the risk of infection, but it can also come with certain risks.