SapC-DOPS nanovesicles for Treating Glioblastoma Multiforme

DESCRIPTION (provided by applicant): Our goal is to develop a new molecular entity with a novel mechanism of action for targeting and eliminating glioblastoma multiforme (GBM, high grade glioma), a deadly and invasive brain tumor with no effective treatment. Of the 12,000 patients expected to be diagnosed with GBM this year, most will succumb within the first year. Clearly, there is an urgent demand for an efficacious anti-glioma drug. To address this need, we are developing a new class of therapeutic proteolipid nanovesicle that can target and destroy glioma tumors. Composed of the small lysosomal, sphingolipid activator protein saposin C (SapC, 80 aa) and the phospholipid dioleoylphosphatidylserine (DOPS); the stable 200 nm SapC-DOPS nanovesicles have unusually high affinity for phosphatidylserine-enriched membrane surfaces that occur widely in many types of tumor cells and tumor neovasculature. In a mechanism consistent with activation of sphingolipid protein function, SapC- DOPS also appears to selectively induce tumor cells to undergo apoptosis. In Phase I of this proposal, we demonstrated the feasibility of using SapC-DOPS nanovesicles to target and kill intracranial gliomas in mouse models. Injections of SapC-DOPS in mice with orthotopically implanted gliomas resulted in dose-dependent improvement in survival. Specific targeting of SapC-DOPS to the tumor mass was demonstrated using fluorescently-tagged nanovesicles in live animal imaging experiments. We also showed that saposin C protein, in specific association with DOPS is essential for targeting. Anticancer activity of SapC-DOPS was confirmed in a second orthotopic glioma model, derived from an aggressive and invasive glioma line. Pilot toxicity data indicated SapC-DOPS to be relatively nontoxic with no evidence of behavioral abnormalities or pathological lesions. Our objective in Phase II proposal is to identify and select optimized SapC-DOPS formulations and treatment methods suitable for advancing toward planned human testing. The specific aims of Phase II are: (1) optimize protein expression and purification, and develop clinically suitable formulation; (2) conduct preclinical pharmacokinetics, stability, and brain and tissue distribution analysis in animal models to determine in vivo disposition of the nanovesicles; and (3) carry out toxicity studies in two animal models to assess safety, towards filing of the IND. Upon the completion of these studies, we expect to have compelling evidence to progress clinical development of SapC-DOPS nanovesicles as a potent new anti-cancer therapeutic (during SBIR Phase III). This research is innovative because SapC-DOPS nanovesicles offer a unique approach for slowing tumor growth and eliminating deep-seated brain tumors. Ultimately, we expect to adapt our technology for targeting different types of tumors and for developing tumor-targeted diagnostics. PUBLIC HEALTH RELEVANCE: We are developing a new molecular entitity for treating glioblastoma multiforme, a deadly form of brain tumor that kills over 90% of afflicted patients. Current standards of treatment, consisting of surgery, radiation, and chemotherapy, have not been effective in significantly reducing morbidity. Our strategy involves using new proteolipid nanovesicles that can penetrate the tumors and selectively destroy malignant cells without harming normal cells. Success in the proposed animal models will enable us to test the product in humans.