title: Investigation of the Physico-Chemical Properties that Enable Co-Formulation of Basal Insulin Degludec with Fast-Acting Insulin Aspart.
abstract: OBJECTIVE
  To study the self-association states of insulin degludec and insulin aspart alone and combined in pharmaceutical formulation and under conditions simulating the subcutaneous depot.
  
  
  METHODS
  Formulations were made of 0.6 mM degludec at 3 and 5 Zn/6 insulin monomers, and 0.6 mM aspart (2 Zn/6 insulin monomers). Self-association was assessed using size-exclusion chromatography (SEC) monitored by UV and orthogonal reverse-phase chromatography.
  
  
  RESULTS
  Simulating pharmaceutical formulation, degludec eluted as dihexamers, whereas aspart eluted as hexamers and monomers. Combining degludec at low zinc with aspart increased dihexamer content, indicating hybrid hexamer formation. At high zinc concentration, however, there was no evidence of this. Simulating the subcutaneous depot by removing preservative, degludec eluted as multihexamers and aspart as monomers. Aspart was incorporated into the multihexamer structures when combined with degludec at low zinc, but there was no such interaction with high-zinc degludec. SEC using progressively diluted concentrations of phenol and m-cresol showed that dissociation of aspart into monomers occurs before the formation of degludec multihexamers.
  
  
  CONCLUSIONS
  Insulins degludec and aspart can be combined without forming hybrid hexamers, but this combinability is dependent on zinc and preservative concentration, and requires that degludec is fully dihexameric before addition of aspart.
authors.affiliation: Diabetes Formulation, Biophysics and Structure, Novo Nordisk A/S, Novo Nordisk Park D6.1126, DK-2760, Maalov, Denmark, svh@novonordisk.com.
authors.forename: Svend
authors.initials: S
authors.lastname: Havelund
authors.forename: Ulla
authors.initials: U
authors.lastname: Ribel
authors.forename: František
authors.initials: F
authors.lastname: Hubálek
authors.forename: Thomas
authors.initials: T
authors.lastname: Hoeg-Jensen
authors.forename: Per-Olof
authors.initials: PO
authors.lastname: Wahlund
authors.forename: Ib
authors.initials: I
authors.lastname: Jonassen
mesh_terms: D002626:Chemistry, Pharmaceutical; D002850:Chromatography, Gel; D056148:Chromatography, Reverse-Phase; D004338:Drug Combinations; D000067493:Dynamic Light Scattering; D007004:Hypoglycemic Agents / Q000008:administration & dosage / Q000737:chemistry* / Q000378:metabolism; D007279:Injections, Subcutaneous; D061267:Insulin Aspart / Q000737:chemistry* / Q000378:metabolism; D049528:Insulin, Long-Acting / Q000008:administration & dosage / Q000737:chemistry* / Q000378:metabolism; D008954:Models, Biological; D011310:Preservatives, Pharmaceutical / Q000737:chemistry
chemical_list: D004338:Drug Combinations; D007004:Hypoglycemic Agents; D049528:Insulin, Long-Acting; D011310:Preservatives, Pharmaceutical; C578220:insulin degludec, insulin aspart drug combination; C571886:insulin degludec; D061267:Insulin Aspart