Patrick Couvreur

siRNA nanoformulation against the Ret/PTC1 junction oncogene is efficient in an in vivo model of papillary thyroid carcinoma

Delivery is a very important concern for therapeutic applications of siRNA. In this study, we have used chitosan-coated poly(isobutylcyanoacrylate) nanoparticles to deliver siRNA with a complementary sequence to the fusion oncogene ret/PTC1. By screening the mRNA junction we have selected a potent siRNA sequence able to inhibit this oncogene in a model of Papillary Thyroid Carcinoma cells. This siRNA sequence has then been validated by a shRNA approach using the same sequence. Furthermore, the high ret/PTC1 inhibition has triggered a phenotypic reversion of the transformed cells. We have designed well-defined chitosan decorated nanoparticles and succeeded to reduce their size. They have allowed to protect ret/PTC1 siRNA from in vivo degradation and leading to significant tumour growth inhibition after intratumoral administration.

Abstract 5671: Enhanced activity of pre-activated oxazaphosphorine prodrugs designed for drug delivery strategy: influence of the length of the engrafted group.

Proceedings: AACR 104th Annual Meeting 2013; Apr 6-10, 2013; Washington, DC Oxazaphosphorines are alkylating antineoplasic agents used in the treatment of cancer and have demonstrated activity against various tumor types, such as soft tissue sarcomas or lymphomas. Oxazaphosphorines are non-toxic prodrugs that require cytochrome P450 (CYP) bioactivation. In the case of Ifosfamide (IFO), the bioactivation produces the 4-OH-IFO, which after ring opening liberates the active nitrogen mustard displaying DNA cross-links. Associated toxicities of IFO are due to 1) acrolein, an urotoxic metabolite concomitantly generated with the nitrogen mustard and 2) chloroacetaldehyde, a neuro and nephrotoxic metabolite obtained by oxidation of the side chains (Kerbusch et al., 2001). To circumvent these toxicities, we have designed pre-activated oxazaphosphorines through electrochemical oxidation and binding of various moieties such as O-alkyl groups and S-alkyl groups. IFO is activated by oxidation of position 4 with labile moieties leading to pre-activated cytotoxic entities. We observed physical-chemical characteristics leading to nano-assemblies depending on the length of the linked moieties, which could bring tissue specificity for drug delivery purposes. Some of these pre-activated prodrugs may be constitutive of drug delivery systems, such as nanoparticules, aiming to address alkylating moieties to their target. We present here the use of different length moieties, from C1 (methoxy) to C30 (Squalenoyl, SQ) with intermediate length of C5 (Pentoxy) and C10 (Geranioxy and DimethylOctanoxy). These compounds are pre-activated formulation of IFO with C4-oxidation allowing to by-pass the CYP activation with direct release of 4-OH-IFO and then the alkylating mustard. Some of them, SQ-(O)-IFO, SQ-(S)-IFO and Geranioxy-IFO are able to self-assembly leading to nanoparticules. The length and nature of the engrafted moieties allow the study of the parameters that lead the kinetics of liberation of the activated compound. The nanoparticules have been fully characterized with a mean diameter of 182 nm for SQ-(O)-IFO and SQ-(S)-IFO and 130 nm for Geranioxy-IFO. The cytotoxic activity of SQ-(O)-IFO and SQ-(S)-IFO has been studied in vitro on a panel of 15 human and murine cancer lines (RMS-1, RD, TC71, A673, SK-N-MC, UW 479, Lan-5, SAOS-2, IGR-OV1, MCF-7(MDR), A549, M109, KB 3.1, B16F10, MiaPaCa-2). The cytotoxic activity of Pentoxy-IFO, Geranioxy-IFO and DimethylOctanoxy-IFO has been studied in vitro on a panel of 2 human cancer lines (A673 and RMS-1). All IFO derivatives present high in vitro activity while IFO has no activity on these cells. This proves the pre-activated property of these new compounds and the lack of CYP activation requirements. Their therapeutic activity is currently studied in vivo on human Ewing sarcoma TC71 and human Lung cancer A549 xenografts in mice after i.v. administration. These compounds are now patented. Citation Format: Charles Skarbek, Hubert Chapuis, Lea Lesueur, Michael Rivard, Thierry Martens, Didier Desmaele, Estelle Daudigeos-Dubus, Jean-Remi Bertrand, Alain Deroussent, Gilles Vassal, Patrick Couvreur, Angelo Paci. Enhanced activity of pre-activated oxazaphosphorine prodrugs designed for drug delivery strategy: influence of the length of the engrafted group. [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 5671. doi:10.1158/1538-7445.AM2013-5671