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

Abstract

Introduction 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. Methods OPN-R3 aptamer was assessed for PK data in vivo with additional comparison of IV and SQ 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 three weeks after inoculation with MDA-MB231 cells and tumor size was evaluated. Results OPN-R3 PK data were: t1/2 7.76 hrs, Tmax 3 hrs, Cmax 13.2 mmol/L, MRT 9 hrs, AUC (0-t) 161.9 mmol-hr/L, Kd 57.2 nM. Half-life was higher when given IV versus SQ (E1/2 7.93 hrs vs 0.74 hrs). 2’ methylation of all available bases increased unmodified aptamer stability and affinity (t1/2 6.2 hrs, Kd 520 nM) but this did not improve on parent aptamer (t1/2 7.78 hours, Kd 18 nM). The aptamer remained extracellular. OPN-R3 caused regression of tumor to levels seen at 1 wk after tumor inoculation. Conclusions We show efficacy of OPN-R3 for reversing growth of breast cancer cells with adequate pharmacokinetic stability for clinical application.

Osteopontin neutralisation abrogates the liver progenitor cell response and fibrogenesis in mice

“…OPN-specific aptamers (which specifically neutralize circulating-extracellular OPN) or sham-aptamers (negative control with mutated active binding site) (34) were administered to mice by tail-vein injections (total of 4 injections per mouse), during the final week of dietary or chemical challenge. A 200ug dose of sham or OPN-aptamers (in 100ul of PBS) was used as this was the dose previously shown to exhibit efficacy in vivo (34, 35). All mice were sacrificed 24 hours after the final dose of aptamers.…”

Role of osteopontin in the pathophysiology of cancer

“…The approach of inhibiting endogenous OPN has been tested in the laboratory and animal setting using multiple approaches. This includes the use of anti-sense oligonucleotides (Shevde et al, 2006), aptamers (Talbot et al, 2011) and shRNA (Shevde et al, 2006; Pang et al, 2011). In each of the studies, abrogating the expression of OPN resulted in decreased proliferation and/or survival, malignant and/or metastatic potential.…”

Screening and Characterization of a Novel RNA Aptamer That Specifically Binds to Human Prostatic Acid Phosphatase and Human Prostate Cancer Cells

“…Aptamers can be easily conjugated to therapeutic molecules, such as drugs, carriers, toxins, and siRNAs Meng et al, 2012;Subramanian et al, 2012;Zhang et al, 2011). Moreover, aptamers can be conjugated with imaging probes for molecular imaging applications Song et al, 2013;Talbot et al, 2011;Zhang et al, 2012).…”