Stability of Commercially Available Glucagon Formulation for Dual-Hormone Artificial Pancreas Clinical Use

Background: Available glucagon formulations are approved for immediate use after reconstitution for severe hypoglycemia emergency treatment. However, they are used in dual-hormone artificial pancreas (insulin and glucagon) studies through subcutaneous infusion pumps over 24 h. Chemical and physical stability of such glucagon use have not been reported in a comprehensive manner. Materials and Methods: Recombinant Glucagon DNA (Eli Lilly) was used. Compatibility and sterility of glucagon delivery through subcutaneous pump systems were verified. Glucagon degradation through liquid chromatography with tandem mass spectrometry (LC-MS/MS), fibrillation using intrinsic tryptophan fluorescence shift, and bioactivity through a cell-protein kinase A-based fluorescent bioassay were assessed over a range of different physical conditions (temperature, movement, and air bubbles). Results: Subcutaneous infusion pump systems administered glucagon in sterile conditions and with comparable accuracy to insulin delivery; mean absolute relative difference of actual versus expected weights were 1.2% ± 1.1% for glucagon and 1.1% ± 0.5% for insulin ( P = 0.9). In comparison to freshly reconstituted samples, glucagon analyzed through LC-MS/MS was intact at 93.0% ± 7.0% after 24 h ( P = 0.42) and 83.04% ± 6.0% after 48 h ( P = 0.02) of incubation in pumps at 32°C. Peak wavelengths for Trp fluorescence did not differ from samples exposed to air bubbles or movement whether incubated (in infusion sets for 24 h at 32°) immediately or 24- and 48-h poststorage at 4°C ( P = 0.10, 0.70 and 0.80, respectively) and no significant differences in bioactivity (shifts in EC 50 ) were found for the same conditions ( P = 0.13, 0.83, and 0.63). Conclusion: Available glucagon formulations are chemically and physically stable, as well as compatible with delivery through subcutaneous infusion pumps over 24 h and can be used in long-term clinical trials.