Abstract 3222: Pre-clinical toxicology and pharmacology of 4-hydroperoxyifosfamide (4-HOOI) and L-lysine salt

Abstract

Abstract HOOI is a hydroperoxy-derivative of ifosfamide (IFOS) and a pro-drug of isophosphoramide mustard (IPM) [the active metabolite of IFOS] – a bi-functional alkylator that cross-links with G/C DNA base sequences resulting in irreparable inter-strand DNA cross-linking and cell death. HOOI has been an unstable laboratory curiosity for years; however, HOOI.L-lysine is a stable salt complex that has allowed the development of HOOI for clinical trials. HOOI spontaneously releases acrolein and chloroacetaldehyde in situ in cancer cells not extracellular in the general circulation (as does IFOS) and has not been associated with cystitis, renal tubular necrosis and/or CNS toxicity. HOOI has been screened in 20+ human xenograft tumor and murine tumor models and has significantly improved %ILS in intracranially implanted human xenografts – MX-1, U251; ZR-75-1 and in P399/CPA leukemia vs. IFOS and IPM. The U251 data (%ILS – 84+) is impressive considering – BCNU produced a 72% ILS. The ZR-75-1 breast cancer had a %ILS – 83. Bone marrow failure was the DLT in mice – LD10 100 mg/kg (for M/F). Dogs (M/F) were treated with 10, 15, 20 and 30 mg/kg. For both sexes, the LD10 was calculated to be 17.2, while the LD50 was calculated to be 17.3 mg/kg. PK values in dogs revealed the following profile for groups dosed with 30 mg/kg: AUC0- t = 1.53 (mg h/L), T1/2α = 0.93 (h), T1/2β = 6.1 (h) & CL = 19.5 (L/ h) [a two compartment model]. The AUC was linear for the 10 and 30 mg/kg doses. HOOI did not generate any detectable plasma chloroacetaldehyde vs. IFOS (2.12 µg/mL from 400 mg/kg) and 25% of the acrolein generated by the MTD of CPA & IFOS. No convulsions, neuropathies or renal dysfunction were observed in either specie. Unlike IFOS/IPM, HOOI is lipophilic, activated intracellular (with < extracellular acrolein and no chloroacetaldehyde released); no IFOS/IPM-associated CNS or GU toxicity was noted. HOOI may increase the safety and efficacy margins of this class of alkylators in advanced CPA- and IFOS-resistant cancers and broaden the target-range (CNS-gliomas). The L-lysine salt stability supports developing HOOI for clinical trials. Supported by grant R44 CA094566 from the NCI/SBIR program. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3222. doi:10.1158/1538-7445.AM2011-3222