Insulin degludec (Tresiba) has an ultra-long duration of action (~42 hours) compared to insulin glargine (~24 hours). The structural basis for this extended duration is:
- A Insulin degludec has a modified A-chain with extra disulfide bonds that resist proteolytic degradation in subcutaneous tissue
- B Insulin degludec is formulated at alkaline pH which precipitates into microcrystals in subcutaneous tissue that dissolve very slowly
- C Insulin degludec uses PEGylation technology to increase molecular weight and prolong absorption similar to biologic drugs
- D Insulin degludec contains a fatty diacid chain on Lys B29, enabling it to form multi-hexameric depots at the injection site and slow albumin-mediated transport ✓
Explanation
Insulin degludec has a C16 fatty diacid (hexadecandioic acid) attached to lysine at B29. In the multidose vial, zinc and phenol keep it in dihexamers. Upon injection into subcutaneous tissue, phenol diffuses away, zinc-mediated dihexamers self-assemble into very long chains of multihexamers (~6-mer to 100-mer chains). These slowly disaggregate into monomers that bind albumin for transport. The multi-hexamer depot formation and albumin binding together produce a half-life of ~25 hours and duration of action of ~42 hours with extremely flat and predictable peakless pharmacokinetics, reducing nocturnal hypoglycaemia.
Reference: KD Tripathi, Essentials of Medical Pharmacology, 8th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.