Multimeric RNA Aptamers for Glucose-Responsive Insulin Formulations

DESCRIPTION (provided by applicant): The landmark Diabetes Control and Complications Trial (DCCT) and the UK Prospective Diabetes Study (UKPDS), have clinically proven that tighter glycemic control, as measured by lower glycosylated hemoglobin A1c (HbA1c) levels, significantly reduces the incidence of diabetic complications. True glycemic control requires treatments that provide plasma glucose-regulated insulin replacement. SmartCells is addressing this need by offering SmartInsulinTM, a novel, minimally invasive, once-a-day injection that both senses and responds to altered serum glucose levels in a clinically relevant way. Unlike pump- and cell-based systems, SmartInsulin is a nanostructured material that self-assembles from two biomolecular building blocks: a glycosylated insulin-polymer conjugate (IPC) and a multivalent glucose-binding molecule (GBM). In order to replace potentially immunogenic, protein-based GBMs, we set out to evolve safer, non-immunogenic, synthetic GBMs constructed from nuclease-resistant, ribonucleic acid (RNA)-based aptamers under an NIH SBIR Phase I grant (DK072774-01). The result of that project has yielded a family of monoclonal, monomeric aptamers that bind glycogen-based IPCs and elute in the presence of glucose. Furthermore, the sequences have been tetramerized to not only enhance glycogen binding but also prepare the system to self assemble through glucose-responsive crosslinking of glycogen IPCs. Nevertheless, the binding affinities for these aptamers are too high to be physiologically relevant. The current two-year proposal seeks to mutagenize and evolve the existing pool to obtain multimeric aptamers with the same binding characteristics as our protein-based GBMs. We further seek to evaluate their ability to form SmartInsulin products, control diabetic rats in vivo, help minimize adverse injection site reaction, and minimize unwanted tissue accumulation under chronic dosing conditions.