Research Project
9185181
Project Summary We seek to develop an ultra-stable ultra-fast insulin analog formulation for use in advanced ?smart? pumps in the treatment of diabetes mellitus. A commercially available insulin formulation that is stable at body temperature for at least 180 days and at room temperature for a year would respectively make practical (a) implantable intraperitoneal closed-loop pumps for the treatment of T1DM/T2DM and (b) pre-filled patch pumps for the treatment of T2DM. The economics of the latter market makes practical the development of a critical enabling technology for an implanted artificial pancreas (?AP?) device linked to a continuous glucose monitor. Ultra-fast pharmacokinetic/dynamic (PK/PD) promises to improve the safety and efficacy of the feedback algorithms employed in such closed-loop systems. The current barrier to the development of more stable insulin formulations is the temperature-dependent susceptibility of insulin to undergo fibrillation; such physical degradation leads to a pro-inflammatory amyloid. At body temperature fibrils can form in commercial insulin formulations in as little as one week on gentle agitation (as in a pump reservoir). Once fibrillation begins, a seeded nucleation-growth process promotes the rapid conversion of the native insulin molecules into amyloid; activity declines exponentially, making dosing inaccurate and leaving deposits that lead to catheter occlusion. To overcome this barrier, an innovative structural approach is proposed based on a single-chain insulin (SCI) platform that is fully potent and yet refractory to fibrillation and chemical degradation. Design of this platform is based on (i) recent crystallographic studies of how insulin interacts with its primary binding site in the insulin receptor (?Site 1?) and (ii) molecular models of insulin fibrils. In particular, we have discovered that a properly constructed 6-8 residue linker between the C-terminus of the B chain (ThrB30) and N-terminus of the A chain (GlyA1) can prevent fibril formation for >1 year on gentle agitation at 37 oC while preserving native biological activity. Such an SCI is stable both in a zinc-free monomeric formulation and in a zinc-based hexameric formulation, thus providing marked flexibility in choice of excipients for the simultaneous optimization of stability and rate of absorption (fast-ON). We will extend such optimization to engineer fast- OFF pharmacodynamics (PD) through modification of insulin?s ancillary receptor-binding surface, cognate to Site 2 in the fibronectin-homology domains of the receptor ?-subunit. An ultra-stable fast-ON/fast-OFF SCI formulation would provide a major advance in AP technology. We therefore propose to synthesize and characterize five such SCIs as candidate formulations. Dr. B.H. Frank (principal investigator) was co-inventor of Humalog? during his prior career at Eli Lilly. Thermalin Diabetes, LLC has an exclusive license to SCI-related IP, which is owned by CWRU.
