An Overview of Concentrated Insulin Products

Structural basis of insulin fibrillation

Insulin is a hormone responsible for maintaining normal glucose levels by activating insulin receptor (IR) and is the primary treatment for diabetes. However, insulin is prone to unfolding and forming cross-β fibers. Fibrillation complicates insulin storage and therapeutic application. Molecular details of insulin fibrillation remain unclear, hindering efforts to prevent fibrillation process. Here, we characterized insulin fibrils using cryo-electron microscopy (cryo-EM), showing multiple forms that contain one or more of the protofilaments containing both the A and B chains of insulin linked by disulfide bonds. We solved the cryo-EM structure of one of the fibril forms composed of two protofilaments at 3.2-Å resolution, which reveals both the β sheet conformation of the protofilament and the packing interaction between them that underlie the fibrillation. On the basis of this structure, we designed several insulin mutants that display reduced fibrillation while maintaining native IR signaling activity. These designed insulin analogs may be developed into more effective therapeutics for type 1 diabetes.

The subtleties of insulin treatment in patients with lipodystrophy

In the treatment of Diabetes Mellitus (DM), which develops on the basis of insulin resistance in patients with lipodystrophy (LD) often require high doses of insulin. Traditionally in practice is to gradually increase the insulin doses to achieve blood glucose normalization. The fact that high insulin doses require a larger injection volume, which causes impairment in the absorption of insulin from the subcutaneous tissue to the circulation. In this article, we discussed the clinical approach to insulin practice in the treatment of DM in patients with LD and reviewed systematically the literature.

Amyloidogenesis via interfacial shear in a containerless biochemical reactor aboard the International Space Station

Fluid interfaces significantly influence the dynamics of protein solutions, effects that can be isolated by performing experiments in microgravity, greatly reducing the amount of solid boundaries present, allowing air-liquid interfaces to become dominant. This investigation examined the effects of protein concentration on interfacial shear-induced fibrillization of insulin in microgravity within a containerless biochemical reactor, the ring-sheared drop (RSD), aboard the international space station (ISS). Human insulin was used as a model amyloidogenic protein for studying protein kinetics with applications to in situ pharmaceutical production, tissue engineering, and diseases such as Alzheimer’s, Parkinson’s, infectious prions, and type 2 diabetes. Experiments investigated three main stages of amyloidogenesis: nucleation studied by seeding native solutions with fibril aggregates, fibrillization quantified using intrinsic fibrillization rate after fitting measured solution intensity to a sigmoidal function, and gelation observed by detection of solidification fronts. Results demonstrated that in surface-dominated amyloidogenic protein solutions: seeding with fibrils induces fibrillization of native protein, intrinsic fibrillization rate is independent of concentration, and that there is a minimum fibril concentration for gelation with gelation rate and rapidity of onset increasing monotonically with increasing protein concentration. These findings matched well with results of previous studies within ground-based analogs.

Effects of Shear Rate and Protein Concentration on Amyloidogenesis via Interfacial Shear

The influence of hydrodynamics on protein fibrillization kinetics is relevant to biophysics, biochemical reactors, medicine, and disease. This investigation focused on the effects of interfacial shear on the fibrillization kinetics of insulin. Human insulin served as a model protein for studying shear-induced fibrillization with relevance to amyloid diseases such as Alzheimer's, Parkinson's, prions, and type 2 diabetes. Insulin solutions at different protein concentrations were subjected to shear flows with prescribed interfacial angular velocities using a knife-edge (surface) viscometer (KEV) operating in a laminar axisymmetric flow regime where inertia is significant. Fibrillization kinetics were quantified using intrinsic fibrillization rate and times (onset, half, and end) determined through spectroscopic measurement of monomer extinction curves and fitting to a sigmoidal function. Additionally, the occurrence of gelation was determined through macroscopic imaging and transient fibril microstructure was captured using fluorescence microscopy. The results showed that increasing interfacial shear rate produced a monotonic increase in intrinsic fibrillization rate and a monotonic decrease in fibrillization time. Protein concentration did not significantly impact the intrinsic fibrillization rate or times; however, a minimum fibril concentration for gelation was found. Protein microstructure showed increasing aggregation and plaque/cluster formation with time.

Effect of Poly(trehalose methacrylate) Molecular Weight and Concentration on the Stability and Viscosity of Insulin

Instability to storage and shipping conditions and injection administration remain major challenges in treating chronic conditions with biopharmaceuticals. Herein, formulations of poly(trehalose methacrylate) (pTrMA) were successfully optimized to stabilize insulin without appreciably increasing viscosity. Polymers were synthesized (2,400 - 29,200 Da), and added to insulin at different concentrations. pTrMA maintained >95% intact insulin against 250 rpm at 37 °C for 3 hours with at least 10 mol. eq. of 5.0 kDa, 7.5 mol. eq. of 9.4 kDa, 5 mol. eq. of 12.8 kDa, 1 mol. eq. of 19.8 kDa, and 0.5 mol. eq. of 29.2 kDa polymers, compared to 13.1% of insulin alone. The lowest pTrMA concentration formulations were more viscous than insulin alone, but the highest viscosity, U-600 with 10 mol. eq. of 5 kDa pTrMA, was only 1.43 cP at 25 °C. This data demonstrates that pTrMA is a promising low viscosity additive to stabilize the diabetes therapeutic insulin.

CONCENTRATED INSULINS: CLINICAL UPDATE OF THERAPEUTIC OPTIONS

Improved glycemic control is associated with a reduced risk of diabetic complications. Optimal management of patients with type 2 diabetes includes nutritional therapy, physical activity, and pharmacotherapy for glycemic control. Most patients with type 2 diabetes are initially managed with oral antidiabetic agents, but as β-cell function declines and the disease progresses, insulin therapy is frequently needed to maintain glycemic control. Insulin therapy given with multidose insulin injection regimen or by continuous insulin infusion is needed for patients with type 1 diabetes to achieve control. Obesity and its associated insulin resistance contribute to greater insulin requirements in patients with both type 1 and type 2 diabetes to achieve glycemic control, creating a need for concentrated insulin. Concentrated insulin formulations can be prescribed as an alternative to 100 unit/mL insulin and provide the advantage of low injection volume, leading to less pain and possibly fewer insulin injections. This review includes a stepwise analysis of all currently available concentrated insulin products, analyzes the most up-to-date evidence, and presents this in combination with expert guidance and commentary in an effort to provide clinicians with a thorough overview of the characteristics and benefits of concentrated insulins in patients with type 1 and type 2 diabetes-instilling confidence when recommending, prescribing, and adjusting these medications. Abbreviations: A1C = glycated hemoglobin; β-cell = pancreatic betacell; BG = blood glucose; CI = confidence interval; CSII = continuous subcutaneous insulin infusion; MDI = multiple daily injections; NHANES = National Health and Nutrition Examination Survey; PD = pharmacodynamic; PK = pharmacokinetic; TDD = total daily dose; U100 = 100 units/mL; U200 = 200 units/mL; U300 = 300 units/mL; U500 = 500 units/mL; USD = United States dollars.

[Assessing nurses’ knowledge of insulin administration and the impact of the introduction of concentrated insulins.]

Insulin is a high-risk medication, and even slight changes in blood levels can lead to serious side effects or can even result in death. Error in administering drugs is one of the main causes of over- or under-dosing, and the recent introduction of concentrated insulins (CI) has increased this risk. We assessed nurses’ knowledge of these CI, their beliefs about the “insulin unit” (IU), and the impact that this knowledge had on the risk of making medication errors. A direct interview survey was conducted in eight departments of medicine and surgery in a university hospital. Sixty-eight nurses and midwives were interviewed. Twenty-six percent of them had already encountered a CI prescription and only 51.5 percent correctly defined the notion of IU. Only 18 percent responded correctly to a practical case of a CI prescription, whilst 35 percent multiplied the dose by two and 24 percent divided it by two. Sixty percent indicated that they regularly use a U-100 graduated insulin syringe to withdraw insulin from the pen. Insulin administration errors related to this misuse, which are very well documented in the literature, are linked to nurses’ lack of knowledge about the true definition of IU. These administration errors have increased with the introduction of concentrated insulins.

Understanding concentrated insulins: a systematic review of randomized controlled trials

OBJECTIVE

To compile, analyze, and summarize the literature on concentrated insulins (i.e. concentrations >100 units/mL) from randomized controlled trials and derive guidance on appropriate use of these agents.

METHODS

Searches were conducted in Medline, Embase, the Cochrane Central Register of Controlled Trials, Trialtrove (through April 2016) and ClinicalTrials.gov (through April 2017) for phase 1-4 clinical studies using concentrated insulins. Selected studies included multiple-arm, randomized controlled trials evaluating subcutaneously administered concentrated insulins. Trial registration numbers (selected studies) were searched in Medline, Embase and Google Scholar (through April 2017). Late-phase studies were graded using guidance from the Agency for Healthcare Research and Quality.

RESULTS

Thirty-eight completed trials (7900 participants) and 34 qualifying publications were identified. Four marketed concentrated insulins were evaluated: two long-acting basal (insulin glargine 300 units/mL and insulin degludec 200 units/mL [IDeg200]), one rapid-acting prandial (insulin lispro 200 units/mL [ILis200]), and one prandial/basal (human regular insulin 500 units/mL). Early-phase trials established bioequivalence for IDeg200 and ILis200 with the corresponding 100 units/mL formulations. Efficacy studies showed noninferior glycemic control between comparators for long-acting basal and prandial/basal products with generally low severe hypoglycemia. Six additional concentrated insulins with completed early-phase development were also identified.

CONCLUSION

Concentrated-insulin products demonstrated efficacious and safe outcomes in appropriate patients. Clinical findings (HbA1c and hypoglycemia) and methodology (initiation and titration), patient factors (insulin experience and dosing requirements) and treatment characteristics (bioequivalence, potency and device features) are important considerations. This overview of these and other factors provides essential information and guidance for using concentrated insulins in clinical practice.

Concentrated Insulins: A Review and Recommendations

For diabetes mellitus patients who require higher doses of insulin, pen-delivered concentrated insulins offer smaller volumes and potentially a lower risk of dosing errors.