Phase I dose-escalation study of ALN-VSP02, a novel RNAi therapeutic for solid tumors with liver involvement.

Abstract

3025 Background: ALN-VSP02 is a RNA interference (RNAi) therapeutic comprised of lipid nanoparticle-formulated small interfering RNAs (siRNAs) targeting the expression of vascular endothelial growth factor (VEGF)-A and kinesin spindle protein (KSP). Methods: A multi-center, open label, phase I dose-escalation trial of ALN-VSP02 administered as a 15-minute iv infusion q2 wks was initiated in patients (pts) with advanced solid tumors and at least one measurable liver lesion. Main objectives included evaluation of safety/tolerability and assessment of PK/PD. Results: Thirty-one pts were enrolled across 7 dose levels (0.1-1.5 mg/kg); median age 57 yrs, all with multiple prior therapies. A total of 140 doses were administered, mean of 4.5 (range 1-17). Treatment was generally well-tolerated, with no dose-dependent trends in clinical or laboratory adverse events. One on-study death (liver failure in a pt with near complete replacement of the liver by tumor) deemed possibly related to treatment occurred at 0.7 mg/kg. Low-grade acute infusion reactions occurred in 10% of pts and were managed with slowing of infusion. Dose-limiting toxicities at doses >0.7 mg/kg included 1 episode each of reversible grade 3 thrombocytopenia (1.25 mg/kg) and hypokalemia (1.5 mg/kg). Plasma PK showed dose-proportional AUC and Cmax. Post-treatment biopsies from 10 pts (7 liver and 3 extrahepatic tumors) showed pharmacologically relevant concentrations (0.3-142 ng/g tissue) of both siRNAs. Molecular evidence of RNAi-mediated VEGF mRNA cleavage was shown in liver (n=2 at 0.4 mg/kg) and in an extrahepatic tumor (ovarian cancer at 1.25 mg/kg) through use of the 5’ RACE assay on tumor biopsies. Additional evidence for an anti-VEGF effect with ALN-VSP02 included a decrease in Ktrans of at least 40% by DCE-MRI in 56% of evaluable pts. Among 27 pts evaluable for response, 8.3% (1 of 12) at doses ≤ 0.4 mg/kg had stable disease (SD) for at least 2 mo compared to 46.6% (7/15) with SD (n=6) or PR (n=1, endometrial cancer with liver metastases) at doses ≥ 0.7 mg/kg. Conclusions: ALN-VSP02 is well-tolerated and has antitumor activity. Pharmacodynamic data are consistent with an anti-VEGF effect, and 1.25 mg/kg q2wks is the recommended phase II dose.