Insulin aspart

In plain language

Insulin aspart is another fast-acting insulin analogue, made by Novo Nordisk and sold as NovoLog (NovoRapid). Like lispro it is injected right before a meal.

Scientists changed one amino acid in the middle of the B chain, replacing an asparagine with an aspartic acid. This small change also stops insulin molecules from pairing up, so it absorbs quickly after injection.

For students

Insulin aspart is human insulin with AsnB3 replaced by Asp (about 5,832 Da), a single negative-charge substitution that blocks dimer formation and speeds subcutaneous absorption (onset ~10-20 minutes, peak 1-3 hours, duration 3-5 hours).

Novo Nordisk later formulated a faster version, Fiasp, adding niacinamide (vitamin B3) and L-arginine to speed the initial absorption further, allowing dosing at the start of a meal. Aspart is a workhorse prandial insulin in pumps and multiple-injection regimens worldwide.

For researchers and instructors

Biochemistry. The B3 substitution sits at the dimer interface; introducing a negative charge at a hydrophobic contact point weakens self-association while leaving receptor-binding residues untouched.

Pharmacology. Absorption profile is similar to lispro; Fiasp's excipients roughly double early absorption rates in the first 30-60 minutes.

Human evidence. Registration trials demonstrated equivalent glycemic control with less postprandial hyperglycemia versus regular insulin; pump trials (including continuous glucose monitoring studies) support its use in closed-loop systems.

Teaching point. Shows that single-point mutations at aggregation interfaces, not the receptor-binding face, are enough to redesign insulin kinetics.