PURPOSE: PARP inhibitor therapy for ovarian cancer exploits the concept of synthetic lethality by taking advantage of defects in DNA damage repair pathways. Currently Olaparib is the only FDA-approved PARP inhibitor and is available as an oral dosage, which has plenty of advantages, but requires the drug to undergo first pass metabolism, inactivating a significant fraction of the dose. We have developed a nanoparticle delivery system to allow for local delivery of Olaparib directly to the intraperitoneal cavity.

METHODS: NanoOlaparib was characterized in vitro in regards to size, charge, drug loading and release before testing on a panel of ovarian cancer cell lines, including KURAMOCHI, SKOV3, OVSAHO, JHOS2, PA1, COV318, 403 and 404, derived from tumors of Brca2-/-, Pten-/-, Tp53-/- mice, and 4306 and 4412, developed from conditional KrasLSL-G12D/+, Pten-/- mice, to elucidate sensitivity profiles and ensure comparable activity to the free drug. 404 cells, derived from Brca2-/-, Tp53-/-, Pten-/- genetically engineered mouse models, were utilized to develop an IP spread xenograft model to test NanoOlaparib in vivo. Animals were treated with NanoOlaparib or oral Olaparib daily for 4 weeks. Tumor burden was monitored weekly via bioluminescence imaging.

RESULTS: NanoOlaparib shows comparable efficacy in vitro to free Olaparib. The murine cell lines were the most sensitive to the treatment regardless of BRCA status, suggesting that Pten deletions are just as susceptible to PARP inhibitor therapy as the BRCA mutations. The average fold change in bioluminescence for NanoOlaparib decreased, while it increased for oral Olaparib. The oral Olaparib animals had widely varied responses, with some animals' tumors shrinking and others never responding. All NanoOlaparib tumors shrank initially, however, severe toxicity was noted after 3 weeks of treatment.

CONCLUSIONS: NanoOlaparib toxicity in vivo was observed with daily dosing likely due to the sustained release of the drug in comparison to the much more rapid clearance of the oral drug. While the NanoOlaparib was toxic, it provided a much more uniform response to the treatment than the oral Olaparib. It is clear that because this strategy provides 100% of the dose to the disease site with a sustained delivery it is no longer necessary to administer daily. This suggests that NanoOlaparib changes the pharmacokinetics to allow for a lower dose to be administered. A modified dosing regime is to be tested with the goal of lowering the toxicity while still maintaining therapeutic efficacy.

Citation Format: Paige Baldwin, Anders Ohman, Daniela Dinulescu, Srinivas Sridhar. NANOOLAPARIB: AN INTRAPERITONEAL PARP INHIBITOR THERAPY FOR OVARIAN CANCER [abstract]. In: Proceedings of the 11th Biennial Ovarian Cancer Research Symposium; Sep 12-13, 2016; Seattle, WA. Philadelphia (PA): AACR; Clin Cancer Res 2017;23(11 Suppl):Abstract nr NTOC-080.