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.


 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).


 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 EC50) 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.
C
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).


 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. 
LC-MS/MS
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).



cell-protein kinase A-based fluorescent bioassay