Insulin analogs in the treatment of type II diabetes and future perspectives

The discovery of insulin by Banting and Best marked 100 years in 2021, and it was a life-saving treatment modality for type II diabetes mellitus (T2DM). Insulin is a natural hormone that has been used extensively in T2DM patients since its discovery. Currently, insulin analogs are also available in different formulations for T2DM management, overcoming the limitations of human insulin with better safety and side effect profiles. The insulin analogs like the rapid-acting analogs (Aspart, lispro, glulisine), the long-acting basal analogs (Glargine, detemir), the ultra-long acting (Insulin degludec), and the premixed insulin analog formulations (75% Neutral protamine lispro, 25% lispro; 50% neutral protamine lispro, 50% lispro; 70% protamine aspart, 30% aspart) have been prepared through genetic engineering while preserving the basic insulin profile. A large number of studies have demonstrated their clinical effects on glycated hemoglobin test (HbA1c) in achieving glycemic control and thereby lowering the microvascular and macrovascular complications of T2DM with less traditional side effects of regular human insulin, mainly the risk of hypoglycemia, postprandial glycemic excursions, and weight gain. This review explores the currently available insulin analogs, their clinical implications, pharmacokinetics (PK), pharmacodynamics (PD), safety profile, and cost-effectiveness. We also discuss the future developments in the management of T2DM, especially the scientific advancements surrounding the novel insulin formulations, including the biosimilar insulin, and the innovative insulin delivery methods, such as oral and inhaled insulin.

Recent Advances in Insulin Therapy

Insulin therapy has advanced remarkably over the past few decades. Ultra-rapid-acting and ultra-long-acting insulin analogs are now commercially available. Many additional insulin formulations are in development. This review outlines recent advances in insulin therapy and novel therapies in development.

Investigation of factors that cause insulin precipitation and/or amyloid formation in insulin formulations

Background

Multiple daily subcutaneous injections (MDSIs) are mainly used for formulating an insulin therapy for diabetic patients; however, they also cause insulin-derived amyloidosis (IDA) and lead to poor glycemic control. In addition, for the continuous subcutaneous insulin infusion system (CSII), precipitation frequently causes catheter occlusion and, if the precipitate in the formulations is amyloid, the injection of the insoluble amyloid into the subcutaneous tissue leads to IDA. The aim of this study was to conduct in vitro experiments and present a situation where insulin formulations cause precipitation and amyloid formation.

Methods

Humulin®R and NovoRapid® were used as model formulations for MDSIs and CSII, respectively. The generation of the precipitation was evaluated by measuring turbidity, and amyloid formation was evaluated by using Thioflavin T. Humulin®R was mixed with saline buffer solutions and glucose solutions to evaluate the effect of dilution. In addition, we created an experimental system to consider the effect of the time course of condition changes, and investigated the effects of insulin concentration, m-cresol existence, and pH change on the generation of the precipitate and amyloid in the formulation.

Results

In both the original and diluted formulations, physical stimulation resulted in the formation of a precipitate, which in most cases was an amyloid. The amyloid was likely to be formed at a near neutral pH. On the contrary, although a precipitate formed when the pH was decreased to near the isoelectric point, this precipitate was not an amyloid. Further decreases in pH resulted in the formation of amyloids, suggesting that both the positive and negative charged states of insulin tended to form amyloids. The formulation additive m-cresol suppressed amyloid formation. When additives were removed from the formulation, the amyloid-containing gel was formed in the field of substance exchange.

Conclusions

To consider changes in conditions that may occur for insulin formulations, the relationship between the formation of precipitates and amyloids was demonstrated in vitro by using insulin formulations. From the in vitro study, m-cresol was shown to have an inhibitory effect on amyloid formation.

New Injectable Agents for the Treatment of Type 2 Diabetes Part 1 - Injectable Insulins

The United States Food and Drug Administration has recently approved several new insulin products and new formulations of existing insulin products. These new products may provide advantages over older products, such as a lower risk of nocturnal hypoglycemia and ease of dosing; however, they are costly. The first of 2 articles in a series, this review will describe the potential advantages and disadvantages of these new insulin products.

A Real-World Anti-Diabetes Medication Cost Comparison Between Premixed Insulin Analogs and Long-Acting Insulin Analogs in Chinese Patients with Type 2 Diabetes: A Retrospective Database Analysis

INTRODUCTION

To assess and compare per-day anti-diabetic medication costs for Chinese type-2 diabetes mellitus (T2DM) insulin-naïve patients between those who initiated premixed insulin analogs ("premixed group") and those who initiated long-acting insulin analogs ("long-acting group").

METHODS

Data were obtained from an electronic medical record database between 2010.01.01 and 2015.06.30 covering medical encounter records from all general hospitals in a district from Shanghai, China. Insulin-naïve T2DM patients who were aged ≥ 18 years, treated with an oral anti-diabetic drug (OAD) only during the baseline period (3 months prior to insulin initiation), and initiated premixed or long-acting insulin analogs were included. Patients were followed until index insulin discontinuation or 12 months after initiation, whichever came first. The t test and generalized linear models adjusting for propensity score (PS) (including baseline demographics, number of OAD classes, comorbidities, costs, and healthcare resource utilization) were used to examine the differences between the two insulin groups.

RESULTS

A total of 570 and 185 patients were identified for the premixed and long-acting groups, with mean (SD) ages of 63.0 (12.8) and 61.1 (11.9) (P = 0.08) and male proportions of 47.4% and 51.4% (P = 0.35), respectively. During the baseline period, 19.3% of the premixed users had T2DM-related hospitalizations, while the rate was 12.4% in the long-acting group (P = 0.03). The mean number of T2DM-related outpatient visits was 0.98 and 1.23 for the premixed and long-acting groups, respectively (P = 0.07). During the follow-up period, the per-day insulin dose averaged 31.7 and 15.3 international units (IU) for the premixed and long-acting groups, respectively. Compared with the patients on premixed insulin, the mean per-day cost for patients on long-acting insulin was 37.3% higher [15.3 vs 11.2 Chinese yuan (RMB); mean difference (MD) (95% CI): 4.2 (3.2, 5.1)] for the overall anti-diabetes medication, 81.3% higher [3.3 vs 1.8 RMB; MD (95% CI): 1.5 (0.8, 2.2)] for OAD, and 28.6% higher [12.0 vs 9.3 RMB; MD (95% CI): 2.7 (2.1, 3.3)] for insulin. The results were consistent after adjusting for the PS.

CONCLUSION

Among Chinese T2DM insulin-naïve patients, those who initiated premixed insulin had a lower per-day antidiabetic medication cost than those who initiated long-acting insulin.

FUNDING

Lilly Suzhou Pharmaceutical Co. Ltd, China.

Pharmacodynamics and pharmacokinetics of insulin aspart assessed by use of the isoglycemic clamp method in healthy cats

The objective of this study was to determine the pharmacodynamics (PD) and pharmacokinetics (PK) of insulin aspart in healthy cats following intramuscular (IM) and subcutaneous (SC) injection. Eight healthy, purpose-bred cats were used in a randomized, crossover study design. Each cat had 2 isoglycemic clamps performed, one after receiving 0.25 IU/kg of insulin aspart by IM injection and one after receiving the same dose by SC injection. The two isoglycemic clamps were performed on different days, at least 48 h apart. The blood glucose, plasma endogenous insulin, and plasma insulin aspart concentrations were measured and the glucose infusion rate (GIR) was recorded during the clamp. The GIR over time was used to create a time-action curve for each clamp which was used to describe the PD of insulin aspart. Data that are normally distributed are reported as mean ± SD, while data that are not normally distributed are reported as median (25-75 percentile). When compared to the PD data that have been reported for regular insulin in healthy cats, insulin aspart had a more rapid onset (IM: 10 min [10-21.25 min], SC: 12.5 min [10-18.75 min]) and shorter duration of action (IM: 182.5 ± 34.33 min, SC: 159.38 ± 41.87 min). The onset of action (P = 0.795), time to peak action (P = 0.499), duration of action (P = 0.301), and total metabolic effect (P = 0.603) did not differ with route of administration; however, SC administration did result in a higher maximum plasma insulin aspart concentration (IM: 1,265.17 pmol/L [999.69-1,433.89 pmol/L], SC: 3,278.19 pmol/L [2,485.29-4,132.01 pmol/L], P = 0.000) and larger area under the insulin aspart vs time curve (IM: 82,662 ± 30,565 pmol/L, SC: 135,060 ± 39,026 pmol/L, P = 0.010). Insulin aspart has a rapid onset of action and short duration of effect in healthy cats when administered by IM and SC injection. Although it cannot be assumed that the PD and PK of insulin aspart will be the same in cats with diabetic ketoacidosis (DKA), our data support further investigation into the use of SC insulin aspart as an alternative to regular insulin for the treatment of DKA in cats.

Different impacts of acylated and non-acylated long-acting insulin analogs on neural functions in vitro and in vivo

AIMS

Centrally administered insulin improves cognitive functions in patients with Alzheimer's disease; however, it remains unknown whether long-acting insulin analogs exert more pronounced effects than insulin. In the present study, we directly compared the effects of insulin and its analogs on neural functions in vitro and in vivo.

METHODS

Cultured rat cerebral cortical neurons were treated with insulin, insulin glargine U100 (Gla), insulin detemir (Det), or insulin degludec (Deg). Moreover, these drugs were intracerebroventricularly administered to mice. Their efficacies were evaluated by biochemical and behavioral analyses.

RESULTS

In cultured neurons, insulin, Gla, and Det increased phosphorylation of Akt and enhanced gene expression of brain-derived neurotrophic factor to a similar extent, although Deg was less effective. The effects of Det and Deg, but not insulin and Gla were suppressed by addition of albumin. When the drug was centrally administered, the increasing effects of insulin on the Akt phosphorylation were comparable to those of Gla but greater than those of Det in hippocampus and cerebral cortex of diabetic db/db and non-diabetic db/m+ mice. Moreover, insulin and Gla enhanced memory functions in Y-maze test and suppressed depression-like behavior in forced swim test in normal mice to a similar extent, and these effects were more potent than those of Det.

CONCLUSIONS

Insulin and Gla have greater impacts on central nervous system than insulin analogs with high albumin sensitivity, such as Det and Deg. These pharmacological profiles should be taken into account for developing an insulin-based therapy to treat Alzheimer's disease.

Clinical effects, cardiovascular and renal outcomes associated with rapid-acting insulin analogs among individuals with type 2 diabetes: a nation-wide observational cohort study

Background

Rapid-acting insulin analogs (RAIs) have not been examined for long-term safety in randomized clinical trials. We performed a nationwide longitudinal cohort study among individuals with type 2 diabetes (T2DM) to address cardiovascular safety and mortality among users of lispro, aspart and glulisine insulins.

Methods

We used four national registers, following patients previously not treated with RAI but with continuous use of RAIs in 2005-2014 up to 6.4 years, to examine HbA1c and weight, and the occurrence of severe hyperglycemia or hypoglycemia, renal failure, cardiovascular events or death. The treatment groups were compared using a weighted Cox proportional hazards model.

Results

We included 17,620 patients, mean age slightly higher than 60 years, diabetes duration 9.9–11.7 years, mean BMI 30.5 kg/m², HbA1c around 70 mmol/mol (8.6% NGSP), and 40.9–54.0% of the patients exhibiting eGFR <60 ml/min/1.73 m² in the three groups. Around 95% of the patients also used another insulin, and 24.2–24.7% had a history of cardiovascular disease (CVD).

Mean HbA1c and weight levels were stable and similar. Incidence rates of death were 234.4, 284.9 and 156.7 per 1000 person-years among users of lispro, aspart, and glulisine; incidence rates of all cardiovascular events were 668.4, 622.4, and 699.5 per 1000 person-years, respectively.

There were no differences in mortality, CVD, renal failure or severe hypoglycemia or hyperglycemia, although a lower mortality risk in patients on glulisine compared with aspart, and lower risk of stroke in users of glulisine was suggested. The risk of severe hyperglycemia was higher with lispro than aspart, and lower of severe hypoglycemia than aspart or glulisine among the older age group.

Conclusions

Overall, there do not appear to be any major important differences in effects on hypoglycemia, hyperglycemia, weight or long-term safety between the three available RAIs among insulin-naive individuals with T2DM in clinical practice.

Administration of Biosimilar Insulin Analogs: Role of Devices

With the expiration of patent protection for several originator insulin analog molecules, the availability of insulin analog copies is set to increase. Many regulatory authorities have developed, and continue to refine, guidelines for the approval of biosimilar insulin analogs. Aspects such as the structure, pharmacokinetics and pharmacodynamics, efficacy, safety, and immunogenicity of biosimilar insulin analogs are extensively addressed in these guidelines, but how the biosimilar insulin analog is administered to people with diabetes is not usually a topic. The aim of this article is to highlight that the delivery device-drug combination is of particular importance. Regulatory, legal, and practical aspects of the delivery device, be it a syringe, pen, or pump, have to be considered in the context of biosimilar insulin analogs. Although the safety and efficacy of biosimilar insulin analogs per se are of primary importance for physicians and people with diabetes, functions and features of the devices used for administration also require attention from a practical point of view. Unfortunately, although there are several clinical studies investigating the technical aspects of and patient preference for the originator insulin analog pens, there are currently very little published data for nonoriginator or biosimilar insulin analog pens. In addition, it is not known if it is safe to assume that a biosimilar insulin analog cartridge is compatible with an existing originator insulin analog pen. We believe that there is a need for more discussion on the role of devices for administration of biosimilar insulin analogs.

Long-acting insulin analog detemir displays reduced effects on adipocyte differentiation of human subcutaneous and visceral adipose stem cells

BACKGROUND AND AIMS

Since treatment with insulin detemir results in a lower weight gain compared to human insulin, we investigated whether detemir is associated with lower ability to promote adipogenesis and/or lipogenesis in human adipose stem cells (ASC).

METHODS AND RESULTS

Human ASC isolated from both the subcutaneous and visceral adipose tissues were differentiated for 30 days in the presence of human insulin or insulin detemir. Nile Red and Oil-Red-O staining were used to quantify the rate of ASC conversion to adipocytes and lipid accumulation, respectively. mRNA expression levels of early genes, including Fos and Cebpb, as well as of lipogenic and adipogenic genes, were measured at various phases of differentiation by qRT-PCR. Activation of insulin signaling was assessed by immunoblotting. ASC isolated from subcutaneous and visceral adipose tissue were less differentiated when exposed to insulin detemir compared to human insulin, showing lower rates of adipocyte conversion, reduced triglyceride accumulation, and impaired expression of late-phase adipocyte marker genes, such as Pparg2, Slc2a4, Adipoq, and Cidec. However, no differences in activation of insulin receptor, Akt and Erk and induction of the early genes Fos and Cebpb were observed between insulin detemir and human insulin.

CONCLUSION

Insulin detemir displays reduced induction of the Pparg2 adipocyte master gene and diminished effects on adipocyte differentiation and lipogenesis in human subcutaneous and visceral ASC, in spite of normal activation of proximal insulin signaling reactions. These characteristics of insulin detemir may be of potential relevance to its weight-sparing effects observed in the clinical setting.

Clinical use of Insulin Degludec: Practical Experience and Pragmatic Suggestions

Insulin degludec (IDeg) is an ultralong acting basal insulin. IDeg has unique pharmacokinetic and pharmacodynamic properties which allow once a daily dosage, at any time of the day. Its use is associated with a significantly lower risk of hypoglycemia. This review discusses the pragmatic use of IDeg, based on available evidence. A complete search of all nine original research papers (BEGIN® clinical trial program) pertaining to IDeg, listed in PubMed, was made to prepare this article.