In neutropenia, typically observed after receiving chemotherapy, several PEGylated forms of granulocyte colony-stimulating factor (G-CSF) are used, including Neulasta (pegfilgrastim), Stimufend (pegfilgrastim-fpgk), Fylnetra (pegfilgrastim-pbbk), and Ziextenzo (pegfilgrastim-bmez) improving the production of white blood cells. This evidence concerns the gene CSF3 and neutropenia.