Molecular and pharmacological characterization of insulin icodec: a new basal insulin analog designed for once-weekly dosing

Abstract

Introduction: Insulin icodec is a novel, long-acting insulin analog designed to cover basal insulin requirements with once-weekly subcutaneous administration. Here we describe the molecular engineering and the biological and pharmacological properties of insulin icodec.

Research design and methods: A number of in vitro assays measuring receptor binding, intracellular signaling as well as cellular metabolic and mitogenic responses were used to characterize the biological properties of insulin icodec. To evaluate the pharmacological properties of insulin icodec in individuals with type 2 diabetes, a randomized, double-blind, double-dummy, active-controlled, multiple-dose, dose escalation trial was conducted.

Results: The long half-life of insulin icodec was achieved by introducing modifications to the insulin molecule aiming to obtain a safe, albumin-bound circulating depot of insulin icodec, providing protracted insulin action and clearance. Addition of a C20 fatty diacid-containing side chain imparts strong, reversible albumin binding, while three amino acid substitutions (A14E, B16H and B25H) provide molecular stability and contribute to attenuating insulin receptor (IR) binding and clearance, further prolonging the half-life. In vitro cell-based studies showed that insulin icodec activates the same dose-dependent IR-mediated signaling and metabolic responses as native human insulin (HI). The affinity of insulin icodec for the insulin-like growth factor-1 receptor was proportionately lower than its binding to the IR, and the in vitro mitogenic effect of insulin icodec in various human cells was low relative to HI. The clinical pharmacology trial in people with type 2 diabetes showed that insulin icodec was well tolerated and has pharmacokinetic/pharmacodynamic properties that are suited for once-weekly dosing, with a mean half-life of 196 hours and close to even distribution of glucose-lowering effect over the entire dosing interval of 1 week.

Conclusions: The molecular modifications introduced into insulin icodec provide a novel basal insulin with biological and pharmacokinetic/pharmacodynamic properties suitable for once-weekly dosing.

Trial registration number: NCT02964104.

Keywords: diabetes mellitus; experimental; insulin; pharmacokinetics; pharmacology.

Figure 1

Schematic depiction and biological properties of insulin icodec. (A) Insulin icodec structure showing changes to the human insulin amino acid sequence and chemical modification attached to the lysine in position B29 of insulin. Insulin substitutions relative to human insulin are shown in blue and bold (TyrA14Glu, TyrB16His and PheB25His). (B) Displacement curves for binding to solubilized hIR (n=4). (C) Displacement curves for binding to solubilized hIGF-1R (n=4). (D) Phosphorylation of the IR downstream signaling molecule AKT in CHO-hIR cells (n=3). (E) Accumulation of glycogen in rat hepatocytes (n=7). Error bars show SEM. Lines show the non-linear fit. AKT, protein kinase B; AU, arbitrary units; CHO-hIR, Chinese Hamster Ovary cells overexpressing hIR; γ-Glu, γ-glutamic acid; hIGF-1R, human insulin-like growth factor-1 receptor; hIR, human insulin receptor; HSA, human serum albumin; IR, insulin receptor; OEG, oligoethylene glycol.

Figure 2

Pharmacokinetic and pharmacodynamic properties of insulin icodec in individuals with type 2 diabetes. (A) Model-predicted serum insulin icodec trough concentration during initiation of once-weekly dosing. The dashed line indicates the threshold for clinical steady state of serum insulin icodec and the shaded area indicates serum insulin icodec concentrations considered as clinical steady state. Circles indicate individual values (n=38). (B) Mean observed total serum insulin icodec concentration (the vast majority being albumin-bound) during week 5 of once-weekly dosing. Error bars show standard error of the mean (n=38). Insulin icodec once-weekly doses correspond to 0.29, 0.48 and 0.57 U/kg/day anticipating equipotency to once-daily basal insulin. (C) Model-predicted distribution of glucose-lowering effect of insulin icodec within a dosing interval at steady state. Dotted line represents equal distribution across 7 days. All three dose levels are combined. Data are arithmetic mean (n=32). AUC, area under the curve; GIR, glucose infusion rate.

Figure 3

Schematic depiction of build-up to steady state and mechanism of action of insulin icodec. (A) Distribution of insulin icodec (light blue) bound to albumin (grey) in the different compartments over time from initiation of once-weekly dosing. Chart 1: distribution of insulin icodec after the first injection, with the majority of insulin icodec in the subcutis and a small proportion absorbed into the blood. Chart 2: day 7, prior to the second injection, showing that there is still insulin icodec distributed prior to the next injection. Charts 3–4: showing the gradual build-up of insulin icodec exposure towards steady state. (B) Conceptual model showing glucose-lowering effect over time from initiation of once-weekly dosing of insulin icodec and once-daily dosing of insulin glargine U100 (at comparable dose levels). Blue curve: insulin icodec; grey curve: insulin glargine U100. Orange labels refer to charts 1–4 in panel A. AU, arbitrary units.