5. Example - Growth factors

Growth factors are proteins made in the body that control the growth and development of cells. Growth factors will typically increase the rate of cell division and may also affect the function of cells and cause them to move to areas of the body where they are needed.

Therapeutic growth factors are most commonly used to treat patients with low numbers of certain blood cells, for example low white blood cells (neutropenia), red blood cells (anaemia) and platelets (thrombocytopenia). Growth factors act specifically by binding to matching receptors on the outside of cells. Therefore, general side effects should be limited to immune reactions, such as injection site reactions.

Granulocyte-colony stimulating factor

White blood cells are an important part of the immune system, being involved in fighting infections and other diseases. Granulocyte-colony stimulating factor (G-CSF) is made naturally in the body and maintains the number of white blood cells at normal levels by stimulating their production. Some chemotherapy medicines used to treat patients with cancer cause the levels of white blood cells to drop to dangerously low levels, increasing the chance of infection. Treatment with additional G-CSF helps to prevent this side effect by increasing white blood cell counts.

Chemotherapy is given in cycles, commonly four weeks in duration. G-CSF is given at the same time as chemotherapy and is administered for as long as white blood cell counts are expected to be low. It is available in two different formulations: one that is administered daily and one that is administered just once per chemotherapy cycle.

The benefit of additional G-CSF in patients treated with chemotherapy is that it helps to prevent infections in people who are already seriously ill from their disease. Such infections can be life-threatening and can also lead to the full dose of chemotherapy not being received.

The most common side effect of additional G-CSF is bone or muscle pain, which can be severe in some cases but can usually be controlled with standard painkillers. Other side effects include nausea or vomiting, and rash at the injection site.