Preclinical Activity of 4-Demethyl-4-cholesteryloxycarbonylpenclomedine in Melanoma

Temozolomide plays a role in treating melanoma refractory to immunomodulatory and mitogen-activated protein kinase-targeted approaches, but its efficacy is limited. 4-Demethyl-4-cholesteryloxycarbonylpenclomedine (DM-CHOC-PEN) is a polychlorinated pyridine cholesteryl carbonate. Its mechanism of action is considered to be via alkylation/adduct formation with N⁷-guanine. It demonstrated activity in intracranial implanted human glioma and breast cancer xenograft mouse models. The activity of DM-CHOC-PEN in melanoma models was assessed.

B-16 melanoma cells were exposed to DM-CHOC-PEN at different concentrations to assess proliferation and survival. B-16 cells were implanted subcutaneously into the flank of adult female C57BL mice which were then were treated with 200 mg/kg DM-CHOC-PEN intraperitoneally daily for 5 days in the setting of palpable subcutaneous tumor. Survival was compared to mice treated with temozolomide or saline. Five mice were treated per group.

In vitro, the respective half-maximal inhibitory concentrations of DM-CHOC-PEN and temozolomide were 0.5 and ≥3.0 μg/ml. Floating, heavily melanotic cells formed and these cells were separated, analyzed, and contained 10-90 ng DM-CHOC-PEN per 10⁵ cells. The improvement in survival of mice treated with DM-CHOC-PEN or temozolomide relative to saline controls was 142% and 78%, respectively.

Longer survival was seen with DM-CHOC-PEN in a C57BL murine model relative to temozolomide and saline-treated controls, supporting the development of clinical trials assessing the efficacy of DM-CHOC-PEN as treatment for metastatic melanoma.