We 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.

The 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.

OPN-R3 PK data were: t_1/2 7.76 hours, T_max 3 hours, C_max 13.2 mmol/L, mean residence time 9 hours, AUC (0–t) 161.9 mmol/hr/L, and K_d 57.2 nmol/L. The half-life was higher when given intravenously versus subcutaneously (E_1/2 7.93 vs 0.74 hours). The 2′ methylation of all available bases increased unmodified aptamer stability and affinity (t_1/2 6.2 hours; K_d 520 nmol/L), but this did not improve on parent aptamer (t_1/2 7.78 hours, K_d 18 nmol/L). The aptamer remained extracellular. OPN-R3 caused regression of tumor to levels seen at 1 week after tumor inoculation.

We show the efficacy of OPN-R3 for reversing growth of breast cancer cells with adequate PK stability for clinical application.