Abstract 4335: Nanoformulations of PARP inhibitors Olaparib and Talazoparib for targeted cancer therapy

Introduction: Poly(ADP-ribose) Polymerase (PARP) plays an important role in a number of DNA repair pathways. PARP inhibitors (PARPi) such as Olaparib and Talazoparib exploit the concept of synthetic lethality by selectively targeting cancer cells with defective DNA repair pathways. These drugs are currently only available in oral form which results in limited bioavailability, poor tumor accumulation, and systemic toxicity. Here we report the development of novel nanoformulations of Olaparib and Talazoparib to allow intravenous or intraperitoneal delivery, providing greater bioavailability and tumor accumulation, while limiting systemic toxicities. Methods: Nanoparticle formulations of Olaparib and Talazoparib were synthesized and tested in vitro and in vivo. Short-and long-term dose response with a panel of ovarian cancer cell lines were conducted. These cell lines include KURAMOCHI, SKOV3, OVSAHO, JHOS2, PA1, COV318, 403 and 404, derived from BRCA2-/-, PTEN-/-, TP53mut mice, and 4306 and 4412, developed from conditional LSL-K-rasG12D/+, PTENloxP/loxP mice. Radiosensitization with NanoOlaparib was tested in the radiation resistant prostate cancer cell line FK01, derived from Ptenpc-/-;Trp53pc-/- mice. In vivo, NanoOlaparib was tested in an IP spread model using 404 cells. Animals were treated IP with NanoOlaparib alone, and in combination with cisplatin. Radiosensitization with NanoOlaparib in vivo was tested in a xenograft model using FK01 cells to mimic castration resistant prostate cancer. Animals were treated biweekly with NanoOlaparib before and after radiation treatment. Results: The murine cell lines 403 and 404 were highly sensitive to this treatment due to the mutations in BRCA2, PTEN, and TP53. 4412 and 4306 showed comparable sensitivity, suggesting that a PTEN deletion confers similar sensitivity to PARP inhibitors as a BRCA2 deletion. PA1 demonstrated high sensitivity to NanoOlaparib which may be attributed to genetic instability. NanoTalazoparib is more potent than NanoOlaparib, resulting in a similar relationship in cell line sensitivity with overall lower IC50’s. Strong synergistic radiosensitization was observed in FK01 cells with NanoOlaparib. Bioluminescence imaging illustrated that NanoOlaparib administered IP daily resulted in a greater inhibition of tumor growth than those treated with oral Olaparib daily. The FK01 xenografts are highly radioresistant with little difference between untreated and radiation only animals. NanoOlaparib delays tumor growth, while the combination of radiation and NanoOlaparib clearly shrinks tumors. Conclusions: Robust nanoparticle formulations of NanoTalazoparib and NanoOlaparib have been successfully developed for in vitro and in vivo studies. These results show that NanoOlaparib and NanoTalazoparib amplify the therapeutic efficacy of PARP inhibition and imply a very promising role for the nanoformulation in ovarian and prostate cancers. Citation Format: Paige Baldwin, Anders Ohman, Jeremy Thong, Shifalika Tangutoori, Anne van de Ven, Rajiv Kumar, Daniela Dinulescu, Srinivas Sridhar. Nanoformulations of PARP inhibitors Olaparib and Talazoparib for targeted cancer therapy. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4335.