Abstract 3722: Efficacy of irreversible electroporation in combination with liposome-nvp-bez235 for head and neck cancer

Abstract Introduction: Irreversible electroporation (IRE) is an emerging, minimally invasive ablation technique with the advantage of not being affected by heat sink effect and the ability of ablation in close vicinity of major blood vessels. One limitation is local recurrence at the original ablated site. We hypothesize that combining IRE with a chemotherapeutic drug could prevent recurrence. NVP-BEZ235 (BEZ) is a dual PI3K/mTOR inhibitor that has shown promise for treating advanced solid malignancies, including sensitizing head and neck squamous cell carcinoma to radiotherapy. However, clinical trials revealed low bioavailability and high toxicity due to high dose oral administration over a long period of time. Thus, we formulated a liposomal BEZ (L-BEZ) and studied its antitumor effect in combination with IRE and compared the results with orally delivered BEZ (oral-BEZ). Methods: IRE was performed using ECM 830 (BTX Harvard Apparatus) at various field strengths. BEZ was loaded into liposome (L-BEZ) by hydration-sonication method. The in vitro and in vivo efficacy was tested against head and neck cancer cell line, HN5 cells and in nude mice bearing HN5 xenografts (n=4/group). Mice were divided into control (no treatment), IRE (2500 V/cm for 99 pulses), IRE + L-BEZ (IRE at 2500 V/cm for 99 pulses and 7 doses of L-BEZ) and IRE + oral-BEZ (IRE at 2500 V/cm for 99 pulses and 21 doses of oral-BEZ) groups. Tumor size was monitored for 60 days. Results: The hydrodynamic volume of NVP-BEZ ranged from 100-500nm. Maximum drug loading was achieved at 2.7mg/mL of BEZ. Electroporation disrupted nanoparticle's integrity even at the lowest tested field strength (250 V/cm) and released BEZ. At the highest field strength (2500 V/cm), approximately 5% of cells survived with IRE, while cells electroporated at 500 V/cm increased cell viability (114%) as compared to the untreated group (100 %). Combination of electroporation and L-BEZ significantly decreased cell viability at 500 V/cm (p<0.05). In vivo, IRE + L-BEZ suppressed tumor growth the longest, as compared with control (no treatment), IRE, and IRE + oral-BEZ. It was also the only group that resulted in no palpable tumor from day 30 to day 60. Survival studies show a significant difference between IRE + L-BEZ and the other groups. IRE + L-BEZ group had 100% animal survival on day 60. IRE + oral-BEZ had 50%, while IRE and control groups had 0% animal survival, on day 60. Also, the total administered BEZ amount in IRE + L-BEZ group was only 6.6% of that in IRE + oral-BEZ group. Conclusion: Incomplete electroporation increases the viability of surviving cells both in vitro and in vivo. Co-delivery of L-BEZ enhances the antitumor efficacy of IRE alone. L-BEZ also decreases BEZ exposure compared to oral-BEZ. Thus, L-BEZ in combination with IRE potentially ensures complete eradication of surviving cells left after IRE. Citation Format: Li Tian, Lucas Wang, Yang Qiao, Saisree Ravi, Ashley Chang, Thomas Alexander Rogers, Linfeng Lu, Adam D. Melancon, Marites Pasuelo Melancon. Efficacy of irreversible electroporation in combination with liposome-nvp-bez235 for head and neck cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2018; 2018 Apr 14-18; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2018;78(13 Suppl):Abstract nr 3722.