A Novel, Stable, Aqueous Glucagon Formulation Using Ferulic Acid as an Excipient

Abstract

Background: Commercial glucagon is unstable due to aggregation and degradation. In closed-loop studies, it must be reconstituted frequently. For use in a portable pump for 3 days, a more stable preparation is required. At alkaline pH, curcumin inhibited glucagon aggregation. However, curcumin is not sufficiently stable for long-term use. Here, we evaluated ferulic acid, a stable breakdown product of curcumin, for its ability to stabilize glucagon.Methods: Ferulic acid-formulated glucagon (FAFG), composed of ferulic acid, glucagon, L-methionine, polysorbate-80, and human serum albumin in glycine buffer at pH 9, was aged for 7 days at 37°C. Glucagon aggregation was assessed by transmission electron microscopy (TEM) and degradation by high-performance liquid chromatography (HPLC). A cell-based protein kinase A (PKA) assay was used to assess in vitro bioactivity. Pharmacodynamics (PD) of unaged FAFG, 7-day aged FAFG, and unaged synthetic glucagon was determined in octreotide-treated swine. Results:No fibrils were observed in TEM images of fresh or aged FAFG. Aged FAFG was 94% intact based on HPLC analysis and there was no loss of bioactivity. In the PD swine analysis, the rise over baseline of glucose with unaged FAFG, aged FAFG, and synthetic native glucagon (unmodified human sequence) was similar.Conclusions: After 7 days of aging at 37°C, an alkaline ferulic acid formulation of glucagon exhibited significantly less aggregation and degradation than that seen with native glucagon and was bioactive in vitro and in vivo. Thus, this formulation may be stable for 3-7 days in a portable pump for bihormonal closed-loop treatment of T1D.

Glucagon in artificial pancreas systems: Potential benefits and safety profile of future chronic use

“…Aggregated glucagon as a result of fibril formation not only loses its function in vivo but can also be cytotoxic at elevated concentrations . Several options are being investigated to find a stable formulation that is compatible with use in infusion pumps over several days including the use of alkaline solutions, glucagon analogues and excipients that stabilize glucagon at neutral pH . The safety profile of new formulations as they become available will also need to be tested according to their potential long‐term side effects.…”

Artificial Pancreas or Novel Beta-Cell Replacement Therapies: a Race for Optimal Glycemic Control?

“…Importantly, glucagon has a relatively short conservation time; in the trials with a bihormonal system, users had to replace the glucagon ampule at least every day [ 18 ••, 19 •]. This problem may be solved by the recent development of glucagon formulations with a longer conservation time [ 30 – 32 ]. In addition, a side effect of glucagon is nausea, as was shown in the study by El-Khatib, in which nausea increased tenfold in the intervention phase [ 19 •].…”

Development of glucose-responsive ‘smart’ insulin systems

“…These algorithms include such parameters as insulin potency, time since previous bolus dose, rate of increase of BGL, heart rate, and temperature to create closed-loop insulin delivery systems designed to maintain euglycemia during a variety of conditions: extent of exercise or activities of daily life (24*-26**), fluctuations in ambient temperature (27*), changes in diet (28, 29), variation in insulin sensitivity (30), and amount of insulin already on-board (31). To more effectively prevent or treat hypoglycemia, more complex pumps have been developed to independently provide either insulin or its counter-regulatory hormone glucagon (26, 32-34). This dual-hormone algorithm triggers SQ injection of a stabilized glucagon formulation based on trends in CGM readings predicting a hypoglycemic excursion.…”