Phase 1b/2a Open-Label, Multiple-Dose, Dose-Escalation Study To Evaluate The Safety and Tolerability Of Intravenous Infusion Of SNS01-T In Patients With Relapsed Or Refractory Multiple Myeloma, Mantle Cell Lymphoma, Or Diffuse Large B Cell Lymphoma

Eukaryotic translation initiation factor 5A (eIF5A) has been implicated in the regulation of cell proliferation, apoptosis, and inflammation, and is the only known protein to be modified by hypusination. Hypusinated eIF5A, the predominant form of eIF5A in cancer cells, is involved in cell survival and activation of inflammatory pathways. In contrast, accumulation of the unhypusinated form of eIF5A is associated with apoptosis and mutants of eIF5A that cannot be hypusinated (e.g. eIF5A_K50R) are pro-apoptotic. SNS01-T was designed to treat B-cell cancers and consists of two active components: a plasmid DNA expressing the pro-apoptotic eIF5A_K50R under the control of a B cell-specific promoter, 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 cellular delivery. The mode of action of SNS01-T is siRNA-mediated inhibition of hypusinated eIF5A and simultaneous over-expression of pro-apoptotic eIF5A_K50R to induce cell death. In vitro cell studies and in vivo xenograft studies have demonstrated the efficacy of this approach.

The safety and tolerability of intravenous administration of SNS01-T is being investigated in a first-in-human Phase1b/2a study in patients with relapsed or refractory multiple myeloma (MM), mantle cell lymphoma (MCL) or diffuse large B cell lymphoma (DLBCL). Eligible patients are being enrolled sequentially into four cohorts at increasing doses. Each patient receives an intravenous infusion of SNS01-T twice weekly for 6 consecutive weeks. Eligible patients must have been diagnosed with MM according to IMWG criteria, or with MCL or DLBCL with histologic confirmation. Patients also must have measurable disease, have relapsed or refractory 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 analysis of pharmacokinetics, immunogenicity, pro-inflammatory cytokines, and therapeutic efficacy.

The required 3 patients per cohort have completed the dosing schedule in cohorts 1 and 2 from a total of 10 patients enrolled (9 patients with MM and 1 with DLBCL). Of the ten patients enrolled, four completed the full treatment period, two did not complete dosing but were evaluable for safety, and four (three in cohort 1 and one in cohort 2) discontinued treatment after fewer than 8 doses and were not evaluable. There were no drug-related serious adverse events or dose limiting toxicities in either cohort 1 or 2.

In cohort 1 (0.0125 mg/kg SNS01-T), two of three evaluable patients did not progress on treatment and were considered stable at week 3 and week 6, the end of the dosing regimen. The third patient progressed after receiving 10 of the 12 doses and was evaluable for safety.

In cohort 2 (0.05 mg/kg), 3 patients (2 with MM and 1 with DLBCL) were evaluable for safety. Stabilization of serum monoclonal protein levels was observed in one MM patient of cohort 2. Two patients (1 with MM and 1 with DLBCL) progressed after receiving 8 of the 12 doses and were evaluable for safety.

Results from ongoing pharmacokinetic studies, immunogenicity studies, and quantification of pro-inflammatory cytokines will be discussed. The planned dose levels for the third and fourth groups are 0.2 and 0.375 mg/kg, respectively. The results to date of this first-in-human clinical trial indicate that SNS01-T can be administered safely and the MTD has not yet been reached (Clinical Trials.gov Identifier: NCT01435720).