Winston W Huh, Daniela Egas-Bejar, Peter M AndersonDivision of Pediatrics, The Children's Cancer Hospital of the University of Texas MD Anderson Cancer Center, Houston, TX, USAAbstract: New treatments are needed to improve the clinical outcome for patients with osteosarcoma. Liposomal muramyl tripeptide phosphatidylethanolamine (mifamurtide) is a synthetic peptidoglycan component packaged in multilamellar liposomes. Mifamurtide has been demonstrated to induce recruitment and activation of macrophages and monocytes of the host innate immune system, which leads to antitumoricidal activity. Early clinical trials have demonstrated the safety and tolerability of mifamurtide combined with chemotherapy, and one major study has demonstrated an overall survival benefit in patients with newly diagnosed nonmetastatic osteosarcoma. This review summarizes the mechanism of action, clinical results, and the optimal biologic dose, and raises potential questions for future development of mifamurtide.Keywords: osteosarcoma, childhood cancer, adolescent, sarcoma, immunotherapy, bone