Pharmacokinetic characterization of an RNA aptamer against osteopontin and demonstration of in vivo efficacy in reversing growth of human breast cancer cells

BackgroundWe report pharmacokinetic (PK) data, evaluation of modifications for increased stability, evaluation for cellular uptake, and mediation of regression of breast cancer for the aptamer OPN-R3.MethodsThe OPN-R3 aptamer was assessed for PK data in vivo with additional comparison of IV and subcutaneous dosing. Five aptamer variants were generated by differential 2′-O-methylation for comparison with parent. OPN-R3-Cy3 was incubated with MDA-MB231 cells and cellular uptake evaluated under confocal microscopy. Mice were treated with OPN-R3, mutant, or saline 3 weeks after inoculation with MDA-MB231 cells and tumor size was evaluated.ResultsOPN-R3 PK data were: t1/2 7.76 hours, Tmax 3 hours, Cmax 13.2 mmol/L, mean residence time 9 hours, AUC (0–t) 161.9 mmol/hr/L, and Kd 57.2 nmol/L. The half-life was higher when given intravenously versus subcutaneously (E1/2 7.93 vs 0.74 hours). The 2′ methylation of all available bases increased unmodified aptamer stability and affinity (t1/2 6.2 hours; Kd 520 nmol/L), but this did not improve on parent aptamer (t1/2 7.78 hours, Kd 18 nmol/L). The aptamer remained extracellular. OPN-R3 caused regression of tumor to levels seen at 1 week after tumor inoculation.ConclusionWe show the efficacy of OPN-R3 for reversing growth of breast cancer cells with adequate PK stability for clinical application.