Palifosfamide

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.

Preclinical activity of palifosfamide lysine (ZIO-201) in pediatric sarcomas including oxazaphosphorine-resistant osteosarcoma.[Pubmed:19224214]

Cancer Chemother Pharmacol. 2009 Sep;64(4):733-40.

PURPOSE: Oxazaphosphorines, such as ifosfamide (IFA), are frequently used in the treatment of pediatric sarcomas. They are pro-drugs and undergo hepatic metabolism into the active moiety and potentially toxic by-products such as acrolein and chloracetaldehyde, which may cause hemorrhagic cystitis and encephalopathy, respectively. In addition, resistance to oxazaphosphorines can be mediated by overexpression of enzymes involved in their catabolism. Isophosphoramide mustard (IPM, Palifosfamide) is the active moiety of IFA. In the current study, the activity of Palifosfamide lysine (ZIO-201), a stable form of Palifosfamide, was evaluated in a panel of sarcoma cell lines and tumor xenografts including oxazaphosphorine-resistant xenografts. METHODS: The cytotoxic effect of Palifosfamide lysine was studied in osteosarcoma (OS), Ewing's sarcoma (ES) and rhabdomyosarcoma (RMS) cell lines using the MTT assay. In vivo, the maximum tolerated dose (MTD) of Palifosfamide lysine was determined in SCID mice based on a 3-day intravenous (IV) administration schedule. The effect on tumor growth and event-free survival was assessed at the MTD in all three sarcoma xenografts. In OS, cyclophosphamide (CPA)-resistant and -sensitive xenografts (OS31 and OS33, respectively) were evaluated for Palifosfamide lysine activity. ALDH1A1 and ALDH3A1 gene expression data for the OS xenografts were mined from the Pediatric Preclinical Testing Program gene expression data. ALDH3A1 enzyme levels were compared between the CPA-resistant and -sensitive xenografts. RESULTS: Palifosfamide lysine was cytotoxic against all the cell lines tested with the IC(50) ranging from 0.5 to 1.5 microg/ml except for OS222, which had an IC(50) of 7 microg/ml. The IV MTD of Palifosfamide lysine in mice was 100 mg/kg per day for three consecutive days. Tumor growth inhibition was seen in both OS31 and OS33 xenografts and the RMS xenograft resulting in a significant difference in event-free survival between the control and the treated groups. Differential gene expression of ALDH3A1 but not ALDH1A1 was noted in the OS31 xenograft. This was confirmed by RT-PCR and the ALDH3A1 enzyme assay. ALDH3A1 enzyme activity was measured at 100 mIU/mg of protein in OS31 xenograft but no significant activity was seen in the OS33 xenograft. CONCLUSIONS: We conclude that Palifosfamide lysine has broad activity in a panel of sarcoma cell lines. It inhibits tumor growth in OS and RMS xenografts. Furthermore, it is active against the CPA-resistant, ALDH3A1 overexpressing, OS xenograft suggesting that it might have the potential of overcoming this resistance mechanism against oxazaphosphorines and may be an active agent in resistant/relapsed sarcomas in patients.

PICASSO III: A Phase III, Placebo-Controlled Study of Doxorubicin With or Without Palifosfamide in Patients With Metastatic Soft Tissue Sarcoma.[Pubmed:27621408]

J Clin Oncol. 2016 Nov 10;34(32):3898-3905.

Purpose Palifosfamide is the active metabolite of ifosfamide and does not require prodrug activation, thereby avoiding the generation of toxic metabolites. The PICASSO III trial compared doxorubicin plus Palifosfamide with doxorubicin plus placebo in patients who had received no prior systemic therapy for metastatic soft tissue sarcoma. Patients and Methods Patients were randomly assigned 1:1 to receive doxorubicin 75 mg/m(2) intravenously day 1 plus Palifosfamide 150 mg/m(2)/d intravenously days 1 to 3 or doxorubicin plus placebo once every 21 days for up to six cycles. The primary end point was progression-free survival (PFS) by independent radiologic review. Results In all, 447 patients were randomly assigned to receive doxorubicin plus Palifosfamide (n = 226) or doxorubicin plus placebo (n = 221). Median PFS was 6.0 months for doxorubicin plus Palifosfamide and 5.2 months for doxorubicin plus placebo (hazard ratio, 0.86; 95% CI, 0.68 to 1.08; P = .19). Median overall survival was 15.9 months for doxorubicin plus Palifosfamide and 16.9 months for doxorubicin plus placebo (hazard ratio, 1.05; 95% CI, 0.79 to 1.39; P = .74). There was a higher incidence of grade 3 to 4 adverse events in the doxorubicin plus Palifosfamide arm (63.6% v 50.9%) including a higher rate of febrile neutropenia (21.4% v 12.6%). Conclusion No significant difference in PFS was observed in patients receiving doxorubicin plus Palifosfamide compared with those receiving doxorubicin plus placebo. The observed median PFS and overall survival in this large, international study can serve as a benchmark for future studies of doxorubicin in metastatic soft tissue sarcoma.

Anticancer activity of stabilized palifosfamide in vivo: schedule effects, oral bioavailability, and enhanced activity with docetaxel and doxorubicin.[Pubmed:22027537]

Anticancer Drugs. 2012 Feb;23(2):173-84.

Palifosfamide, the DNA-alkylating metabolite of ifosfamide (IFOS), has been synthesized as a stabilized tris or lysine salt and found to have preclinical and clinical antitumor activity. Stabilized Palifosfamide overcomes limitations of IFOS because of patient-to-patient variability in response resulting from variable prodrug activation, resistance and toxicities of metabolic byproducts, acrolein and chloroacetaldehyde. Palifosfamide represents an effective alternative to IFOS and other DNA-alkylating prodrugs. The antitumor activities of stabilized Palifosfamide were investigated in vivo. Dose response, route and schedule of administration, and interaction with docetaxel or doxorubicin were investigated in NCr-nu/nu mice bearing established orthotopic mammary MX-1 tumor xenografts. Oral activity was investigated in P388-1 leukemia in CD2F1 mice. Oral and intraperitoneal bioavailabilities were compared in Sprague-Dawley rats. Stabilized Palifosfamide administered by optimized regimens suppressed MX-1 tumor growth (P<0.05) by greater than 80% with 17% complete antitumor responses and up to three-fold increase in time to three tumor doublings over controls. Median survival in the P388-1 (P<0.001) model was increased by 9 days over controls. Oral bioavailability in rats was 48-73% of parenteral administration, and antitumor activity in mice was equivalent by both routes. Treatment with Palifosfamide-tris combined with docetaxel or doxorubicin at optimal regimens resulted in complete tumor regression in 62-75% of mice. These studies support investigation of stabilized Palifosfamide in human cancers by parenteral or oral administration as a single agent and in combination with other approved drugs. The potential for clinical translation of the cooperative interaction of Palifosfamide-tris with doxorubicin by intravenous administration is supported by results from a recent randomized Phase-II study in unresectable or metastatic soft-tissue sarcoma.

Palifosfamide, a bifunctional alkylator for the treatment of sarcomas.[Pubmed:20024846]

IDrugs. 2010 Jan;13(1):38-48.

Ifosfamide is a chemotherapeutic prodrug used in the treatment of several tumor entities, including bone and soft-tissue sarcoma. However, the application of high-dose ifosfamide is not feasible because of severe side effects caused by metabolites. The active metabolite isophosphoramide mustard is not suitable for administration because of chemical instability. ZIOPHARM Oncology Inc, under license from Dekk-Tec Inc, is developing Palifosfamide, a formulation of isophosphoramide mustard with tris(hydroxymethyl)aminomethane salt-stabilization (Palifosfamide-tris) and previously with lysine-stabilization (Palifosfamide-lys). Preclinical studies and phase I and I/II clinical trials demonstrated that Palifosfamide-tris had an antitumor efficiency comparable or superior to that of ifosfamide. Patients treated with Palifosfamide-tris did not display any of the neurotoxic or nephrotoxic side effects associated with ifosfamide. At the time of publication, data from phase II trials were being evaluated and phase III trials were being planned. Palifosfamide-tris is expected to be a safer and less toxic alternative to ifosfamide; however, considering other new approaches under investigation for tumors such as sarcoma, such as molecular-based treatment strategies, it is unclear what position Palifosfamide-tris might occupy on the market.