The quaternary structure of insulin glargine and glulisine under formulation conditions

The quaternary structures of insulin glargine and glulisine under formulation conditions and upon dilution using placebo or water were investigated using synchrotron small-angle X-ray scattering. Our results revealed that insulin glulisine in Apidra® is predominantly hexameric in solution with significant fractions of dodecamers and monomers. Upon dilution with placebo, this equilibrium shifts towards monomers. Insulin glargine in Lantus® and Toujeo® is present in a stable hexamer/dimer equilibrium, which is hardly affected by dilution with water down to 1 mg/ml insulin concentration. The results provide exclusive insight into the quaternary structure and thus the association/dissociation properties of the two insulin analogues in marketed formulations. [Display omitted] •In marketed formulations, insulin glulisine and glargine do not appear to consist of pure hexamers.•Insulin glulisine is present as hexamers with significant fractions of monomers and dodecamers under formulation conditions.•Dilution studies reveal a dissociation of the hexamers and dodecamers into monomers for insulin glulisine.•Insulin glargine in Lantus and Toujeo demonstrates a hexamer-dimer equilibrium, which is maintained upon dilution with water.