Abstract B219: 4-Demethyl-4-cholesteryloxycarbonylpenclomedine (DM-CHOC-PEN) and 4-hydroperoxyifosfamide (HOOI) as binary therapy for melanoma.

Introduction: 4-Demethyl-4-cholesteryloxycarbonyl-penclomedine (DM-CHOC-PEN) is a polychlorinated pyridine cholesteryl carbonate, which is in Phase I clinical trials in patients with advanced cancer - IND 68,876. DM-CHOC-PEN is active vs. intracranially (IC) implanted human xenograft models - U251 and D54 glioblastoma and MX-1 breast cancer and recently found to be active vs. B-16 melanoma - 142% ILS. DM-CHOC-PEN9s MOA is via alkylation of DNA @ N7 - guanine, as well as converting melanoma cells into a melanotic Go phase with cell death. Not all cells were converted into Go phase and senescence, thus the interest in designing a binary drug approach for DM-CHOC-PEN, as an improvement in treatment for melanoma. A number of agents are cytotoxic vs. B-16 cells in vitro and in vivo; however, 4-hydroperoxyifosfamide (HOOI), which is converted to isophosphoramide mustard (IPM) in vivo, demonstrated the best %ILS. The latter drug has been chosen as a companion with DM-CHOC-PEN in the present binary drug study vs. B-16 mouse melanoma. Methods: B-16 melanoma cells were cultured using RPMI media with 10% FBS and pen/strep @ 37° C in a CO2 incubator. Drugs were added to the cells in a growth phase and removed after 8–12 h. Adult female C57BL mice in groups of 5–6 mice were implanted subcutaneously (SC) with B-16 mouse melanoma (106 cells) and when SC nodules were palpable the mice were dosed IP daily (200 mg/kg) for 5-days with DM-CHOC-PEN followed by HOOI administered IP @ varying doses and daily/weekly schedules and monitored daily until death. Mice with SC B-16 melanoma were dosed with single agents - DM-CHOC-PEN, HOOI, cis-platinum and temozolamide, which were used as controls. Tumor tissue was extracted with dichloromethane, and assayed per HPLC and NMR. Results: In vitro, DM-CHOC-PEN and HOOI, as single agents, had IC50 of 0.5 and 0.8 μg/mL vs. B-16 melanoma cells, resp. Mice bearing SC B-16 melanoma treated with DM-CHOC-PEN (200 mg/kg/d × 5d, IP) alone vs. saline controls demonstrated %ILS of 142%; thus supporting the in vitro observations. In vivo in the B-16 melanoma model, cis-platinum as a single agent had a %ILS = 0%, but for HOOI it was 85%. In 2-drug studies, DM-CHOC-PEN plus cis-platinum together (in theoretical therapeutic ranges) were too toxic in combination, however, the %ILS for DM-CHOC-PEN plus HOOI was 173%. Tumor tissue was removed within 2-days of treating mice with DM-CHOC-PEN, extracted and revealed 75 μg/g tumor tissue of DM-PEN, a metabolite. Discussion: HOOI is a S-phase alkylating agent that is an appropriate 2nd agent to kill cells escaping from the DM-CHOC-PEN - induced Go phase induction. To date, the best treatment regimen was DM-CHOC-PEN (200 mg/kg/d × 5d) followed by HOOI (90 mg/d × 3d) - %ILS = 173. The finding that melanoma tissue extracts resulted in μg of DM-PEN (the metabolite) is in agreement with the pharmacokinetic findings observed for DM-CHOC-PEN in rats and humans, which will be reviewed. The binary drug combination will be reviewed with the FDA. Supported in part by: NCI SBIR grants - R43/44CA85021. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2011 Nov 12-16; San Francisco, CA. Philadelphia (PA): AACR; Mol Cancer Ther 2011;10(11 Suppl):Abstract nr B219.