A long-acting, recombinant analog of the endogenous human granulocyte colony-stimulating factor (G-CSF) with hematopoietic activity. Similar to G-CSF, long-acting G-CSF analog SPI-2012 binds to and activates specific cell surface receptors and stimulates neutrophil progenitor proliferation and differentiation, as well as selected neutrophil functions. Therefore, this agent may decrease the duration and incidence of chemotherapy-induced neutropenia. The long-acting G-CSF analog SPI-2012 extends the half-life of G-CSF, allowing for administration once every 3 weeks.