David Raymond Owens

Monomeric Insulins and Their Experimental and Clinical Implications

Due to the inherent pharmacokinetic properties of available insulins, normoglycemia is rarely, if ever, achieved in insulin-dependent diabetic patients without compromising their quality of life. Subcutaneous insulin absorption is influenced by many factors, among which the associated state of insulin (hexameric) in pharmaceutical formulation may be of importance. This review describes the development of a series of human insulin analogues with reduced tendency to selfassociation that, because of more rapid absorption, are better suited to meal-related therapy. DNA technology has made it possible to prepare insulins that remain dimeric or even monomeric at high concentration by introducing one or a few amino acid substitutions into human insulin. These analogues were characterized and used for elucidating the mechanisms involved in subcutaneous absorption and were investigated in preliminary clinical studies. Their relative receptor binding and in vitro potency (free-fat cell assay), ranging from 0.05 to 600% relative to human insulin, were strongly correlated (r = 0.97). In vivo, most of the analogues exhibited ∼100% activity, explainable by a dominating receptor-mediated clearance. This was confirmed by clamp studies in which correlation between receptor binding and clearance was observed. Thus, an analogue with reduced binding and clearance gives higher circulating concentrations, counterbalancing the reduced potency at the cellular level. Absorption studies in pigs revealed a strong inverse correlation (r = 0.96) between the rate of subcutaneous absorption and the mean association state of the insulin analogues. These studies also demonstrated that monomeric insulins were absorbed three times faster than human insulin. In healthy subjects, rates of disappearance from subcutis were two to three times faster for dimeric and monomeric analogues than for human insulin. Concomitantly, a more rapid rise in plasma insulin concentration and an earlier hypoglycemic response with the analogues were observed. The monomeric insulin had no lag phase and followed a monoexponential course throughout the absorption process. In contrast, two phases in rate of absorption were identified for the dimer and three for the normal hexameric human insulin. The initial lag phase and the subsequent accelerated absorption of soluble insulin can now be explained by the associated state of native insulin in pharmaceutical formulation and its progressive dissociation into smaller units during the absorption process. In the light of these results, the effects of insulin concentration, injected volume, temperature, and massage on the absorption process are now also understood. When given to diabetic patients immediately before a standard meal, the monomeric analogue lowered postprandial glucose excursions by ∼50% when compared with human insulin given at the same time. Subsequently, it was shown that three monomeric to dimeric analogues injected separately just before a meal gave glycemic control at least comparable to that of human insulin administered 30 min earlier. Lower plasma glucose concentrations (∼50%) were observed with the analogues from 1.5 h postprandially. Thus, monomeric analogues are faster in onset of action, can be given with the meal without losing glycemic control, and have the potential to minimize late hypoglycemia. Therefore, the development of these novel insulins represents a major step in the evolution of insulin preparations to subserve meal-related insulin requirements.

Alternative routes of insulin delivery

Attempts at replicating physiological insulin secretion, as a means of restoring the normal metabolic milieu and thereby minimizing the risk of diabetic complications, has become an essential feature of insulin treatment. However, despite advances in the production, purification, formulation and methods of delivery of insulin which have occurred in recent years, this has met with limited success. The current advocacy of intensive insulin therapy regimens involving multiple daily subcutaneous injection places a heavy burden of compliance on patients and has prompted interest in developing alternative, less invasive routes of delivery. To date, attempts to exploit the nasal, oral, gastrointestinal and transdermal routes have been mainly unsuccessful. The respiratory tree, with a large surface area, offers the greatest potential for the delivery of polypeptide drugs and there is renewed interest in administrating insulin by the intrapulmonary route. Current pulmonary drug delivery systems include a variety of pressurized metered dose inhalers, dry powder inhalers, nebulizers and aqueous mist inhalers. Recent clinical studies suggest a possible role for inhaled insulin in fulfilling meal‐related insulin requirements in persons with Type 1 and Type 2 diabetes. Most experience with inhaled insulin has been obtained using either dry powder formulation in the Nektar Pulmonary Inhaler/Exubera device (Nektar Therapeutics Inc., San Carlos, CA, Aventis, Bridgewater, NJ, Pfizer, NY) or a liquid aerosol formulation in the AERx® Insulin Diabetes Management System (Aradigm Corp., Hayward, CA, NovoNordisk A/S, Copenhagen, Denmark). If long‐term safety and efficacy is confirmed, inhalation may become the first non‐subcutaneous route of insulin administration for widespread clinical use. Despite overwhelming interest and investment in administering insulin via the oral route, success is not expected in the short term. Attempts at utilizing the buccal mucosa and skin are also continuing. Pancreatic transplantation will remain limited to those patients receiving a kidney transplant and immunotherapy. Islet cell transplantation is at an early though encouraging stage following the availability of new less toxic immunosuppressive agents. True insulin independence will require further advances in the combined fields of cell biology and genetics to ensure freedom from both the need for lifelong administration of insulin and the complications of diabetes.

Insulins today and beyond

The advent of insulin almost 80 years ago revolutionised treatment of diabetes and must be one of the most outstanding achievements of twentieth century medicine. Since then, there has been an ever-increasing awareness and acceptance of the need to achieve and sustain near-normoglycaemia to delay onset and retard progression of diabetic angiopathy. Physiological insulin replacement is therefore central to management of patients with diabetes who are unable to make [corrected] insulin. Insulin formulations, treatment strategies, and methods and routes of delivery have changed much, with more and more options for monitoring the effect on blood glucose concentrations. Patients with type 1 and type 2 diabetes need insulin much more aggressively than previously. Parallel developments in glucose-sensing technologies are welcomed as an integral part of safe and optimum implementation of insulin replacement therapy.

Once-daily basal insulin glargine versus thrice-daily prandial insulin lispro in people with type 2 diabetes on oral hypoglycaemic agents (APOLLO): an open randomised controlled trial.

BACKGROUND As type 2 diabetes mellitus progresses, oral hypoglycaemic agents often fail to maintain blood glucose control and insulin is needed. We investigated whether the addition of once-daily insulin glargine is non-inferior to three-times daily prandial insulin lispro in overall glycaemic control in adults with inadequately controlled type 2 diabetes mellitus taking oral hypoglycaemic agents. METHODS In the 44-week, parallel, open study that was undertaken in 69 study sites across Europe and Australia, 418 patients with type 2 diabetes mellitus that was inadequately controlled by oral hypoglycaemic agents were randomly assigned to either insulin glargine taken once daily at the same time every day or to insulin lispro administered three times per day. The primary objective was to compare the change in haemoglobin A(1c) from baseline to endpoint (week 44) between the two regimens. Randomisation was done with a central randomisation service. Analysis was per protocol. This study is registered with ClinicalTrials.gov, number NCT00311818. FINDINGS 205 patients were randomly assigned to insulin glargine and 210 to insulin lispro. Mean haemoglobin A(1c) decrease in the insulin glargine group was -1.7% (from 8.7% [SD 1.0] to 7.0% [0.7]) and -1.9% in the insulin lispro group (from 8.7% [1.0] to 6.8% [0.9]), which was within the predefined limit of 0.4% for non-inferiority (difference=0.157; 95% Cl -0.008 to 0.322). 106 (57%) patients reached haemoglobin A(1c) of 7% or less in the glargine group and 131 (69%) in the lispro group. In the glargine group, the fall in mean fasting blood glucose (-4.3 [SD 2.3] mmol/L vs -1.8 [2.3] mmol/L; p<0.0001) and nocturnal blood glucose (-3.3 [2.8] mmol/L vs -2.6 [2.9] mmol/L; p=0.0041) was better than it was in the insulin lispro group, whereas insulin lispro better controlled postprandial blood glucose throughout the day (p<0.0001). The incidence of hypoglycaemic events was less with insulin glargine than with lispro (5.2 [95% CI 1.9-8.9] vs 24.0 [21-28] events per patient per year; p<0.0001). Respective mean weight gains were 3.01 (SD 4.33) kg and 3.54 (4.48) kg. The improvement of treatment satisfaction was greater for insulin glargine than for insulin lispro (mean difference 3.13; 95% CI 2.04-4.22). INTERPRETATION A therapeutic regimen involving the addition of either basal or prandial insulin analogue is equally effective in lowering haemoglobin A(1c). We conclude that insulin glargine provides a simple and effective option that is more satisfactory to patients than is lispro for early initiation of insulin therapy, since it was associated with a lower risk of hypoglycaemia, fewer injections, less blood glucose self monitoring, and greater patient satisfaction than was insulin lispro. FUNDING Sanofi-Aventis.

Efficacy and safety of linagliptin in persons with Type 2 diabetes inadequately controlled by a combination of metformin and sulphonylurea: a 24‐week randomized study1

Diabet. Med. 28, 1352–1361 (2011)

Comparison of Pharmacokinetics and Dynamics of the Long-Acting Insulin Analogs Glargine and Detemir at Steady State in Type 1 Diabetes A double-blind, randomized, crossover study

OBJECTIVE—To compare pharmacokinetics and pharmacodynamics of insulin analogs glargine and detemir, 24 subjects with type 1 diabetes (aged 38 ± 10 years, BMI 22.4 ± 1.6 kg/m2, and A1C 7.2 ± 0.7%) were studied after a 2-week treatment with either glargine or detemir once daily (randomized, double-blind, crossover study). RESEARCH DESIGN AND METHODS—Plasma glucose was clamped at 100 mg/dl for 24 h after subcutaneous injection of 0.35 unit/kg. The primary end point was end of action (time at which plasma glucose was >150 mg/dl). RESULTS—With glargine, plasma glucose remained at 103 ± 3.6 mg/dl up to 24 h, and all subjects completed the study. Plasma glucose increased progressively after 16 h with detemir, and only eight subjects (33%) completed the study with plasma glucose <180 mg/dl. Glucose infusion rate (GIR) was similar with detemir and glargine for 12 h, after which it decreased more rapidly with detemir (P < 0.001). Estimated total insulin activity (GIR area under the curve [AUC]0–end of GIR) was 1,412 ± 662 and 915 ± 225 mg/kg (glargine vs. detemir, P < 0.05), with median time of end of action at 24 and 17.5 h (glargine vs. detemir, P < 0.001). The antilipolytic action of detemir was lower than that of glargine (AUC free fatty acids0–24 h 11 ± 1.7 vs. 8 ± 2.8 mmol/l, respectively, P < 0.001). CONCLUSIONS—Detemir has effects similar to those of glargine during the initial 12 h after administration, but effects are lower during 12–24 h.

NEW HORIZONS — ALTERNATIVE ROUTES FOR INSULIN THERAPY

Since the introduction of insulin therapy 80 years ago, the lives of millions of patients with diabetes have been saved, prolonged and immeasurably improved. However, restoring normal glucose levels in diabetic patients through administering insulin by subcutaneous injection has proved virtually impossible. The consequences for patients are serious complications, including diabetic retinopathy and nephropathy, which tend to result from persistent hyperglycaemia. Maximizing glucose control in diabetic patients requires several daily injections. In an effort to reduce this burden, alternative and less-intrusive routes for the administration of insulin are being explored.

Glycemic Variability: The Third Component of the Dysglycemia in Diabetes. Is it Important? How to Measure it?:

The dysglycemia of diabetes includes two components: (1) sustained chronic hyperglycemia that exerts its effects through both excessive protein glycation and activation of oxidative stress and (2) acute glucose fluctuations. Glycemic variability seems to have more deleterious effects than sustained hyperglycemia in the development of diabetic complications as both upward (postprandial glucose increments) and downward (interprandial glucose decrements) changes activate the oxidative stress. For instance, the urinary excretion rate of 8-iso-PGF2α, a reliable marker of oxidative stress, was found to be strongly, positively correlated (r = 0.86, p < .001) with glycemic variability assessed from the mean amplitude of glycemic excursions (MAGE) as estimated by continuous glucose monitoring systems (CGMS). These observations therefore raise the question of whether we have the appropriate tools for assessing glycemic variability in clinical practice. From a statistical point of view, the standard deviation (SD) around the mean glucose value appears as the “gold standard.” By contrast, the MAGE index is probably more appropriate for selecting the major glucose swings that are calculated as the arithmetic mean of differences between consecutive peaks and nadirs, provided that the differences be greater than the SD around the mean values. Furthermore, calculating the MAGE index requires continuous glucose monitoring, which has the advantage to detect all isolated upward and downward acute glucose fluctuations. In conclusion, the increasing use of CGMSs will certainly promote better assessment and management of glycemic variability.

Endothelium and inelastic arteries: an early marker of vascular dysfunction in non-insulin dependent diabetes.

Atheroma is the main cause of mortality and morbidity in patients with non-insulin dependent diabetes mellitus. Endothelial dysfunction underlies atheroma formation. Flow mediated vasodilatation is a measure of endothelial function as well as a determinant of arterial distensibility,1 measurements of which have not previously been reported in patients with non-insulin dependent diabetes. We studied 12 symptom free, non-smoking, healthy patients (six men) with well controlled non-insulin dependent diabetes diabnosed 1-7 (mean 3.8) years previously (mean age 50 (SD 9) years, body mass index 26.9 (4.8) kg/m2, serum cholesterol concentration 5.8 (0.5) mmol/l). Patients with known causes of endothelial dysfunction were excluded. All patients had insulin resistance with basal hyperinsulinaemia,2 no biochemical evidence of renal impairment, and no microalbuminuria. A group of 12 normal non-smoking subjects was matched for sex, age, body mass index, blood …

Subcutaneous Insulin Absorption Explained by Insulin's Physicochemical Properties: Evidence From Absorption Studies of Soluble Human Insulin and Insulin Analogues in Humans

Objective To study the influence of molecular aggregation on rates of subcutaneous insulin absorption and to attempt to elucidate the mechanism of absorption of conventional soluble human insulin in humans. Research Design and Methods Seven healthy male volunteers aged 22-43 yr and not receiving any drugs comprised the study. This study consisted of a single-blind randomized comparison of equimolar dosages of 125I-labeled forms of soluble hexameric 2 Zn2+ human insulin and human insulin analogues with differing association states at pharmaceutical concentrations (AspB10, dimeric; AspB28, mixture of monomers and dimers; AspB9, GluB27, monomeric). After an overnight fast and a basal period of 1 h, 0.6 nmol/kg of either 125I-labeled human soluble insulin (Actrapid HM U-100) or 125I-labeled analogue was injected subcutaneously on 4 separate days 1 wk apart. Absorption was assessed by measurement of residual radioactivity at the injection site by external γ-counting. Results The mean ± SE initial fractional disappearance rates for the four preparations were 20.7 ± 1.9 (hexameric soluble human insulin), 44.4 ± 2.5 (dimeric analogue AspB10), 50.6 ± 3.9 (analogue AspB28), and 67.4 ± 7.4%/h (monomeric analogue AspB9, GluB27). Absorption of the dimeric analogue was significantly faster than that of hexameric human insulin (P < 0.001); absorption of monomeric insulin analogue AspB9, GluB27 was significantly faster than that of dimeric analogue AspB10 (P < 0.01). There was an inverse linear correlation between association state and the initial fractional disappearance rates (r = −0.98, P < 0.02). Analysis of the disappearance data on a log linear scale showed that only the monomeric analogue had a monoexponential course throughout. Two phases in the rates of absorption were identified for the dimer and three for hexameric human insulin. The fractional disappearance rates (%/h) calculated by log linear regression analysis were monomer 73.3 ± 6.8; dimer 44.4 ± 2.5 from 0 to 2 h and 68.9 ± 3.5 from 2.5 h onward; and hexameric insulin 20.7 ± 1.9 from 0 to 2 h, 45.6 ± 5.0 from 2.5 to 5 h, and 70.6 ± 6.3 from 5 h onward. Conclusions Association state is a major determinant of rates of absorption of insulin and insulin analogues. The lag phase and the subsequent increasing rate of subcutaneous soluble insulin absorption can be explained by the associated state of native insulin in pharmaceutical formulation and its progressive dissociation into smaller units during the absorption process.