Palifosfamide is the active moiety of ifosfamide (IFA) [1].IFA is alkylating agents which are active against a variety of pediatric sarcomas such as rhabdomyosarcoma (RMS), Ewing’s sarcoma (ES), osteosarcoma (OS) and other undifferentiated soft tissue sarcomas [1].In human OS cell lines SaOS-2, OS229 and OS230, Palifosfamide lysine has broad activity with IC50 ranging from 2.25 to 6.75 μM. While OS222 had the IC50 of 31.5 μM [1].In CB17 female SCID mice, palifosfamide lysine (100 mg/kg) administered intravenously for three consecutive days, the mean weight loss was less than 15% and complete recovery to baseline within 4 weeks of treatment. While, doses higher than 100 mg/kg for three consecutive days lead to either greater than 20% loss of body weight or death. In NCr-nu/nu mice bearing established orthotopic mammary MX-1 tumor xenografts, palifosfamide suppressed MX-1 tumor growth by greater than 80% with 17% complete antitumor responses [2]. References:[1]. Hingorani P, Zhang W, Piperdi S, et al. Preclinical activity of palifosfamide lysine (ZIO-201) in pediatric sarcomas including oxazaphosphorine-resistant osteosarcoma. Cancer Chemother Pharmacol, 2009, 64(4): 733-740. [2]. Jones B, Komarnitsky P, Miller GT, et al. Anticancer activity of stabilized palifosfamide in vivo: schedule effects, oral bioavailability, and enhanced activity with docetaxel and doxorubicin. Anticancer Drugs, 2012, 23(2): 173-184.