Abstract 5621: Single-walled carbon nanotubes for delivery of siRNA: Antitumor efficacy comparing formulated complexes in EGFR overexpressing A431 xenografts.
Authors: D. Lynn Kirkpatrick, Olga Gliko, Michelle Weiss, Iris Owusu, Anton Naumov
Journal: Cancer Research (2013)

Abstract siRNA has the potential to be a selective targeted cancer therapy but currently lacks an adequate delivery mechanism. Ensysce has been exploring the use of single-walled carbon nanotubes (SWCNT) as delivery vehicles for siRNA and has previously reported on the safety, in vitro and in vivo efficacy of this platform. We have determined that siRNA/SWCNT complexes are well tolerated, and can be administered in a multi-weekly intravenous (i.v.) dosing schedule over extended periods of time. The pharmacokinetics and distribution of the SWCNT in animals have been examined. The goal of the current study was to determine an optimal formulation of siRNA/SWCNT that provides maximal tumor accumulation and antitumor efficacy. siRNA/SWCNT complexes were formulated in aqueous solutions with PEG-lipid analogues and the circulation and tissue distribution were evaluated. All solutions prepared were examined by atomic force microscopy (AFM), dynamic light scattering (DLS) and for z-potential. siRNA payloads were quantified and siRNA/SWCNT complexes were examined for stability in serum and systemic efficacy. Solutions of siRNA/SWCNT formulated complexes were administered i.v. to C57Bl6 mice or to nu/nu mice bearing MiaPaCa human pancreatic or A431 human epidermoid carcinoma tumors. Mice were sacrificed at various times after i.v. administration. Blood and tissues were collected and SWCNT concentrations were determined by measuring near infrared fluorescence using NS2 Nanospectralizer. The presence and persistence of SWCNT in the tissues was determined. Animals bearing A431 xenografts were treated with SWCNT/siEGFR/PEG-lipid analogue complexes and tumor growth control was compared to that produced by erlotinib. Data to be presented will include details of the analytical characterization of the SWCNT, circulating half-life (t1/2) and tissue concentrations versus time of administration. Tumor and tissue SWCNT content were found to depend on the t1/2 of the formulation of preparations that were delivered. Microscopic examination of tumors indicated that SWCNT presence in tumor increased with the increasing t1/2. The siRNA target knockdown in tumor xenografts of up to 90% was observed with complexes comprised of a number of siRNA payloads including siKRAS, siEGFR and siTRX. Antitumor activity has also been demonstrated with complexes targeting one or two growth driving proteins. Formulations providing t1/2 of 13 hr for the circulating SWCNT were evaluated with siEGFR against A431 EGFR overexpressing cells, with the optimal formulation showing tumor growth delay of 16 to 20 days versus the free siRNA treated control. In summary, SWCNT offer a novel approach to deliver oligonucleotides safely and effectively and formulation of the complexes can offer a means to control the siRNA biodistribution. Citation Format: D. Lynn Kirkpatrick, Olga Gliko, Michelle Weiss, Iris Owusu, Anton Naumov. Single-walled carbon nanotubes for delivery of siRNA: Antitumor efficacy comparing formulated complexes in EGFR overexpressing A431 xenografts. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5621. doi:10.1158/1538-7445.AM2013-5621