Taylor, Cathy

TPS8116 Background: Eukaryotic translation initiation Factor 5A (eIF5A) has been implicated in the regulation of apoptosis and is the only known protein to be modified by hypusination. Hypusinated eIF5A is the predominant form of eIF5A in cancer cells. However, in its unhypusinated form, eIF5A is pro-apoptotic. SNS01-T, designed to treat myeloma, consists of two components: a plasmid DNA expressing eIF5AK50R (human eIF5A containing a lysine to arginine substitution at position 50) which remains pro-apoptotic because it cannot be hypusinated, and an siRNA against an untranslated region of native eIF5A mRNA. When these two components are combined with linear polyethyleneimine (PEI), the nucleic acids are condensed into nanoparticles for protection from degradation in the blood and enhanced delivery to tissues. The eIF5AK50R transgene is under the control of the B29 promoter and enhancer, which restricts expression to B cells. The mode of action of SNS01-T is to use an eIF5A-specific siRNA to deplete the pool of hypusinated eIF5A in myeloma cells while simultaneously adding pro-apoptotic eIF5AK50R. In vitro cell studies and in vivo xenograft studies have demonstrated the efficacy of this approach. Methods: Eligible patients are enrolled sequentially into four cohorts of increasingly higher doses. Each cohort will receive SNS01-T by intravenous infusion twice weekly for 6 consecutive weeks and then be observed every 4 weeks during a 24-week follow-up period. Eligible patients must have been diagnosed with multiple myeloma according to IMWG criteria, have measurable disease, have relapsed disease after two or more prior treatment regimens, have a life expectancy of at least 3 months, and not be eligible to receive any other standard therapy known to extend life expectancy. The primary objective is to evaluate the safety and tolerability of multiple escalating doses of SNS01-T. Secondary objectives include pharmacokinetics, immunogenicity studies, proinflammatory cytokine quantitation, and therapeutic efficacy. Two of the planned 15 patients have been enrolled. (Clinical Trials.gov Identifier: NCT01435720.)

Abstract Introduction: The eukaryotic translation initiation factor 5A (eIF5A) is the only known protein to be regulated by post-translational addition of a hypusine residue. Both hypusinated eIF5A and the enzyme that mediates eIF5A hypusination have been identified as markers of neoplastic growth and metastasis. However, recent studies have indicated that, in its unhypusinated form, eIF5A is pro-apoptotic and thus functionally distinct from hypusine-modified eIF5A. In vitro cell studies and in vivo xenograft studies have demonstrated that simultaneous suppression of eIF5A expression and overexpression of a non-hypusinable mutant of eIF5A potently induces apoptosis in multiple cancer cell types. SNS01 is a nanoparticle specifically designed for the treatment of multiple myeloma. SNS01 is comprised of three components: a DNA vector containing a B-cell-specific (B29) promoter driving expression of a pro-apoptotic mutant of eIF5A (eIF5AK50R) that cannot be hypusinated; an siRNA that targets the native hypusinated eIF5A that promotes growth of cancer cells; and a synthetic polymer called polyethylenimine (PEI). Methods: Ethidium-bromide agarose gel electrophoresis was used to detect heparin-mediated release of nucleic acids from nanoparticles. Dynamic light scattering (DLS) was used to assess the short-term stability of SNS01 by monitoring changes in size distribution, polydispersity, and zeta potential. In vitro biological activity of SNS01 was assessed using RT-qPCR to measure eIF5A and eIF5AK50R transgene expression as well as FACS detection of AnnexinV-FITC labeled apoptotic cells. Anti-tumoral activity of SNS01 was evaluated using a subcutaneous human myeloma model (KAS-6/1 cells) in SCID mice with twice-weekly intra-venous injections of SNS01. Results: SNS01 nanoparticles were found to be relatively stable for as long as 48 hours at room temperature with no significant loss in nucleic acid integrity. The nanoparticles had an average diameter of 146.2 nm, a polydispersity of 0.287 and an average zeta potential of 35.3+0.7 mV. These parameters were quite stable over 48 hours. SNS01 could also be frozen at − 80°C for at least one month with no observable loss in biological activity. Twice-weekly intra-venous injections into myeloma tumor-bearing mice of a frozen SNS01 preparation was found to have anti-tumoral activity comparable to freshly prepared SNS01 (frozen SNS01: 89 % tumor inhibition, p = 0.00158; SNS01: 84 % tumor inhibition, p = 0.00003). Conclusions: SNS01 is relatively stable at room temperature and was also found to be stable and biologically active following freezing. Citation Information: Mol Cancer Ther 2009;8(12 Suppl):A196.