Peptides and proteins have a tendency to adhere to glass and plastic surfaces. This may at low concentration impact the actual amount in solution. To minimize this unspecific adherence, adding detergents or inert proteins like e.g., ovalbumin or other serum albumins to the solution can minimize this phenomenon. In case albumins are added to peptide/protein solutions, ensure that the albumins are free of any proteases, but be aware that it will affect the apparent potency and affinity in in vitro assays in case a fatty acid is attached to the compound.
Recommended procedure for in vitro studies: dissolve the entire content of the vial by adding 4 mL 30 mM HEPES buffer pH 8. Gently rotate the vial until all content is dissolved. Avoid harsh shaking or stirring of the solution. Keep the stock solution at 4C overnight and make the desired number of aliquots (use low protein binding vials) of the stocks. Snap freeze the aliquots in liquid nitrogen and store them at minus 20C. When thawed, the stock solution should be stable for up to three weeks at 4C.
Recommended procedure for in vivo studies: NNC0123-0327 and human insulin (NNC0121-0308) can be dosed in vivo in a zinc-free and phenol/m-cresol-free formulation vehicle. For NNC0123-0327 it may contain 8mM sodium phosphate, 240mM glycerol, pH 7.4 and for human insulin it may contain 10mM sodium phosphate, 140mM sodium chloride, pH 7.4. For both compounds, consider adding 0.007% polysorbate 20 if concentrations are so low that adsorption to vials may affect the concentration. If insulin oligomeric/multimeric properties are of interest, zinc and phenol/m-cresol can be added. Zinc is typically added as zinc acetate between 0 and 6 moles/mole of insulin analogue. The resulting tonicity should be recalculated. Formulations should be used fresh but can be stored for up to one week refrigerated.