A device system which automatically maintain blood glucose concentrations in the normal range by dosing insulin in response to continuously sensed glucose concentration data represents a modern attempt to mechanically simulate normal beta cell physiology and solve many of the problems associated with intensive insulin therapy today, including improving the quality of life for patients with diabetes and improving glucose control. The development of such a "closed loop" artificial pancreas algorithmically linking continuous glucose sensors with insulin infusion pumps is an active area of research. Most studies with experimental artificial pancreas (AP) systems which have used insulin only have shown that hypoglycemia requiring carbohydrate administrations has not been eliminated using multiple experimental algorithms. The insulin- only approach to the artificial pancreas does not fully mimic normal physiology in that there is no ability to abort impending hypoglycemia through the use of counter-regulatory hormones. The only way for such insulin only AP system to react to declining glucose concentrations is to reduce or stop infusing subcutaneous insulin. This will not guarantee prompt termination of insulin effect in part because of residual depots of insulin in the subcutaneous space. In normal physiology, pancreatic alpha cells secrete glucagon to counter the glucose lowering effect of insulin. One of these counter-regulatory hormones is glucagon, a 29 amino acid peptide which stimulates the conversion of glycogen stored in the liver into glucose (glycogenolysis). Recent closed loop insulin studies in which glucagon is also used algorithmically to prevent impeding hypoglycemia have shown excellent glucose control with very low rates of hypoglycemia. Glucagon in its currently marketed form however is chemically and physically unstable in solution and therefore not practical for clinical development in bi-hormonal artificial pancreas systems. Biodel scientist have prepared lab formulations of aqueous glucagon at pH 7 that remain stable in solution. In this application, Biodel proposes to optimize multiple pH 7 aqueous formulations of glucagon to provide a minimum of 18 month stability under refrigerated and if possible, room temperature (25C) conditions for long-term storage requirements. We will assess whether all current US Pharmacopeia (USP) compendia methods are applicable to these formulations and we will develop suitable methods if required. We will demonstrate biological activity in a swine model and we will demonstrate that our formulation is compatible with a marketed insulin pump system at elevated temperatures for at least 9 days.
The full benefits of intensive insulin therapy for patients with diabetes have yet to be realized in large part because it is extremely difficult to optimize continuously variable insulin dose requirements using current technology and because of the inability to eliminate hypoglycemia. The development of closed loop artificial pancreas systems is an active area of research which promises to address the first problem;however initial studies of insulin-only systems have not shown elimination of hypoglycemia. The addition of algorithmically delivered glucagon as part of a bi-hormonal closed loop system has been shown to result in very low hypoglycemia rates. However, currently marketed formulations of glucagon are chemically and physically unstable at high temperatures and are not likely to be practical for continuous infusion through insulin pumps. In this application, Biodel proposes a strategy to develop a stable glucagon formulation suitable for continuous pump delivery.