NEO212: A NOVEL TEMOZOLOMIDE-PERILLYL ALCOHOL CONJUGATE EXHIBITS SUPERIOR ACTIVITY AGAINST TEMOZOLOMIDE RESISTANT GLIOMAS AND INTRACRANIAL TRIPLE NEGATIVE BREAST CANCER METASTASIS

Abstract

BACKGROUND: Although the alkylating agent temozolomide (TMZ) has become the standard of care in the treatment of malignant gliomas, its overall efficacy is still limited by development of drug resistance, limited blood brain barrier (BBB) penetrance, and myelotoxicity. Recently, we have synthesized a TMZ analog where the monoterpene perillyl alcohol (POH) is covalently linked to TMZ via an amide bond. This new compound (NEO212) has been tested in two situations: TMZ resistant gliomas and breast cancer intracranial metastasis. METHODS: Glioma cell lines (U251TR, LN229TR2, T98G) determined to be TMZ resistant based on base excision repair (BER) pathway, mismatch repair (MMR) deficiency, or overexpression of O6 methyl-guanine-DNA methyltransferase (MGMT) were evaluated in-vitro. In vivo experiments were performed using intracranial implant of luciferase labeled TMZ resistant cell lines. Triple negative breast cancer lines were tested, and implanted intracranially for in-vivo model. NEO212 was administered in both cases using subcutaneous injection using 10 day treatment, 7 day rest cycles. RESULTS: NEO212, at equimolar concentrations to TMZ, was more cytotoxic to TMZ resistant cells, and did not have significant toxicity on normal astrocytes and brain endothelial cells. NEO212 induced cell death appeared to be independent of the mechanism of DNA repair resistance. In vivo experiments using intracranial implant of luciferase labeled TMZ resistant cell lines demonstrated that NEO212 crossed the BBB, reduced intracranial growth, and increased animal survival significantly compared to TMZ, without significant toxicity (including bone marrow). NEO212 was also effective in TMZ resistant breast cancer lines. In an intracranial mouse tumor model with triple-negative breast cancer, NEO212 revealed considerably greater therapeutic efficacy than TMZ, where a single cycle of treatment (10 days) extended median survival benefit from 6 days (in the case of TMZ) to 28 days, with good tolerance. CONCLUSIONS: NEO212 appears to be a promising well tolerated new agent with similar mechanism of cytotoxicity to TMZ. Its increased potency is most likely multi-factorial: 1) increased DNA damage, involving a broader scope of DNA repair mechanisms. 2) linkage with POH, resulting in longer biological half-life and greater opportunity for placement of cytotoxic DNA lesions. 3) increased lipophilicity, allowing for better penetration of the BBB, and possibly cell membrane. Preliminary results demonstrate that it can safely be administered systemically; more detailed toxicity studies are currently underway. SECONDARY CATEGORY: Tumor Biology.