Indications: Filgrastim-sndz (Zarxio) is a leukocyte growth factor indicated to decrease incidence of and shorten duration of infections, fevers, and neutropenia in patients undergoing certain types of chemotherapy and patients with certain forms of neutropenia. It is also approved to mobilize autologous hematopoiec progenitor cells into the peripheral blood for collection by leukapheresis.

Dosing: Filgrastim-sndz injections come in two doses of single-use prefilled syringes, 300 mcg/0.5 mL and 480 mcg/0.8 mL. The starting dose is 5mcg/kg/day for patients with cancer receiving myelosuppressive chemotherapy or induction and consolidation chemotherapy for AML, and patients with cyclic or idiopathic neutropenia. The starting dose is 6 mcg/kg for patients with congenital neutropenia. The starting dose is 10 mcg/kg/day for patients with cancer undergoing bone marrow transplantation or patients undergoing autologous peripheral blood progenitor cell collection.

Pharmacokinetics: Filgrastim-sndz exhibits nonlinear pharmacokinetics. Following subcutaneous administration, peak concentrations occur within 2 to 8 hours. After intravenous administration, the elimination half-life was approximately 3.5 hours. Continuous 24-hour intravenous infusion over 11 to 20 days produced a steady state, with no evidence of drug accumulation.

Side Effects/Risks: The most common adverse reactions include pyrexia, pain, rash, cough, dyspnea, epistaxis, bone pain, anemia, diarrhea, and headache. Warnings include fatal splenic rupture, acute respiratory distress syndrome (ARDS), serious allergic reactions including anaphylaxis, and fatal sickle cell crises.

More information: Filgrastim-sndz is the first biosimilar product to earn FDA approval in the United States. It is approved as biosimilar to Neupogen (filgrastim), but not as an interchangeable product.

Source: Highlights of prescribing information: Zarxio (filgrastim-sndz). U.S. Food & Drug Administration web site. http://www.accessdata.fda.gov/drugsatfda_docs/label/2015/125553lbl.pdf. Revised March 2015. Accessed March 13, 2015.