Basal activity profiles of NPH and [Nepsilon-palmitoyl Lys (B29)] human insulins in subjects with IDDM

Derivatization with fatty acids in peptide and protein drug discovery

Peptides and proteins are widely used to treat a range of medical conditions; however, they often have to be injected and their effects are short-lived. These shortcomings of the native structure can be addressed by molecular engineering, but this is a complex undertaking. A molecular engineering technology initially applied to insulin - and which has now been successfully applied to several biopharmaceuticals - entails the derivatization of peptides and proteins with fatty acids. Various protraction mechanisms are enabled by the specific characteristics and positions of the attached fatty acid. Furthermore, the technology can ensure a long half-life following oral administration of peptide drugs, can alter the distribution of peptides and may hold potential for tissue targeting. Due to the inherent safety and well-defined chemical nature of the fatty acids, this technology provides a versatile approach to peptide and protein drug discovery.

Pharmacodynamics of the long-acting insulin analogues detemir and glargine following single-doses and under steady-state conditions in patients with type 1 diabetes

AIM

The pharmacodynamic characteristics of the basal insulin analogues insulin detemir (IDet) and insulin glargine (IGlar) have been examined extensively via euglycaemic clamp studies. However, differences in clamp methodology and in the analysis of clamp data between trials have led to confusion over the duration of action of these two insulins. The aim of this study was to address these ambiguities in the literature by assessing the pharmacodynamic properties of IDet and IGlar over 30 h under single-dose and steady-state conditions using the definitions and procedures previously standardized by Heise and Pieber in 2007.

METHODS

This was a single-centre, randomized, double-blind, glucose clamp trial involving 36 patients with type 1 diabetes.

RESULTS

The mean duration of action of IDet was 25.9 h, compared with 19.8 h for IGlar after a single-dose (NS), and 23.3 h (IDet) versus 27.1 h (IGlar) at steady-state (p < 0.0001). IDet had a significantly higher area under the curve glucose infusion rate (AUCGIR ) than IGlar over 0-12 h after a single-dose (p = 0.0018). The steady-state AUCGIR for IDet was numerically higher than IGlar over 0-12 h (728 vs. 592 mg/kg, respectively; p = NS), but significantly lower than IGlar at 12-30 h (p = 0.0003).

CONCLUSIONS

The duration of action of IDet is 23 h (range: 4.0-30.0), while that of IGlar is 27 h (range: 10.5-29.0) (95% CI: -8.1, 0.6). This suggests both insulins can be used for once-daily dosing, but individual needs must be considered.

Insulin preparations with prolonged effect

The discovery of insulin and its clinical application early in the last century dramatically improved the prospects of people with diabetes. However, the limitations of those initial, unmodified insulin preparations were quickly recognized; most notably, their relatively "short action" meant that multiple daily subcutaneous injections were required. This stimulated a concerted effort to modify the properties of insulin in order to extend the duration of its blood glucose-lowering effect, minimize dosing frequency, and decrease the burden of treatment. The first successful attempts to prolong insulin's action were achieved by modifying its formulation with additives such as protamine and zinc, culminating in the production of "intermediate-acting" neutral protamine Hagedorn (NPH) insulin in the 1940s and the lente family of insulins in the 1950s. However, NPH and lente insulins were still associated with several limitations, including considerable variability of effect and a pronounced peak in their time-action profile. In the 1980s, the focus of research moved toward the modification of insulin itself with the aim of producing a "long-acting" insulin that would better satisfy basal insulin requirements over the entire day. Once-daily insulin glargine was the first "long-acting" insulin analog in clinical practice, followed by once- or twice-daily insulin detemir and, more recently, insulin degludec, which is now being evaluated for administration at less frequent intervals. These analogs demonstrate several benefits over "intermediate-acting" insulins, including a lower risk of both overall hypoglycemia and nocturnal hypoglycemia and reduced day-to-day glucose variability, making it more feasible to achieve better fasting and overall glycemic control. Long-acting insulin analogs (insulin glargine and insulin detemir) are now firmly established as key tools in the battle against diabetes, and ongoing clinical research of insulin-based therapy should focus on treatment strategies to maximize their benefits. To date, the clinical experience with insulin degludec is limited but demonstrates it has comparable efficacy to insulin glargine.

Beyond the era of NPH insulin--long-acting insulin analogs: chemistry, comparative pharmacology, and clinical application

The new rDNA and DNA-derived "basal" insulin analogs, glargine and detemir, represent significant advancement in the treatment of diabetes compared with conventional NPH insulin. This review describes blood glucose homeostasis by insulin in people without diabetes and outlines the physiological application of exogenous insulin in patients with type 1 and type 2 diabetes. The requirements for optimal basal insulin treatment are discussed and the methods used in the evaluation of basal insulins are presented. An essential criterion in the development of an "ideal" basal insulin preparation is that the molecular modifications made to the human insulin molecule do not compromise safety. It is also necessary to obtain a clear understanding of the pharmacokinetic and pharmacodynamic characteristics of the two currently available basal insulin analogs. When comparing glargine and detemir, the different molar concentration ratios of the two insulin formulations should be considered along with the nonspecificity of assay systems used to determine insulin concentrations. However, euglycemic clamp studies in crossover study design provide a good basis for comparing the pharmacodynamic responses. When the latter is analyzed by results of intervention clinical trials, it is concluded that both glargine and detemir are superior to NPH in type 1 and type 2 diabetes. However, there is sufficient evidence to demonstrate that these two long-acting insulin analogs are different in both their pharmacokinetic and pharmacodynamic profiles. These differences should be taken into consideration when the individual analogs are introduced to provide basal insulin supplementation to optimize blood glucose control in patients with type 1 and type 2 diabetes as well. PubMed-Medline was searched for articles relating to pharmacokinetics and pharmacodynamics of glargine and detemir. Articles retrieved were reviewed and selected for inclusion if (1) the euglycemic clamp method was used with a duration >or=24 h, (2) a single subcutaneous dose of glargine/detemir was used, and (3) area under the curve for insulin concentrations or glucose infusion rates were calculated.

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 acids(0-24 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.

pI-shifted insulin analogs with extended in vivo time action and favorable receptor selectivity

A long-acting (basal) insulin capable of delivering flat, sustained, reproducible glycemic control with once daily administration represents an improvement in the treatment paradigm for both type 1 and type 2 diabetes. Optimization of insulin pharmacodynamics is achievable through structural modification, but often at the expense of alterations in receptor affinity and selectivity. A series of isoelectric point (pI)-shifted insulin analogs based on the human insulin sequence or the GlyA21 acid stable variant were prepared by semi-synthetic methods. The pI shift was achieved through systematic addition of one or more arginine (Arg) or lysine (Lys) residues at the N terminus of the A chain, the N terminus of the B chain, the C terminus of the B chain, or through a combination of additions at two of the three sites. The analogs were evaluated for their affinity for the insulin and IGF-1 receptors, and aqueous solubility under physiological pH conditions. Notably, the presence of positively charged amino acid residues at the N terminus of the A chain was consistently associated with an enhanced insulin to IGF-1 receptor selectivity profile. Increased IGF-1 receptor affinity that results from Arg addition to the C terminus of the B chain was attenuated by cationic extension at the N terminus of the A chain. Analogs 10, 17, and 18 displayed in vitro receptor selectivity similar to that of native insulin and solubility at physiological pH that suggested the potential for extended time action. Accordingly, the in vivo pharmacokinetic and pharmacodynamic profiles of these analogs were established in a somatostatin-induced diabetic dog model. Analog 18 (A0:Arg, A21:Gly, B31:Arg, B32:Arg human insulin) exhibited a pharmacological profile comparable to that of analog 15 (insulin glargine) but with a 4.5-fold more favorable insulin:IGF-1 receptor selectivity. These results demonstrate that the selective combination of positive charge to the N terminus of the A chain and the C terminus of the B chain generates an insulin with sustained pharmacology and a near-native receptor selectivity profile.

Molecular variants and derivatives of insulin for improved glycemic control in diabetes

Insulin is a historic molecule. It presents many first instances, such as the first protein to be fully sequenced, one of the first proteins to be crystallized in pure form, one among the early proteins whose structure was investigated using X-ray crystallography, the first protein to be chemically synthesized and the first Biotech drug. Therefore, the development of insulin in the early years is intricately intertwined with the progress in molecular and structural biology. In recent years, development of a range of insulin analogs has led to better control of glucose levels, thus preventing secondary complications and improving the quality of life in diabetic patients. Such analogs were obtained by modification of the native insulin sequence. They vary with regard to their pharmacokinetic profile, stability, tissue specificity and mode of administration. In addition, alterations involving incorporation of various chemical moieties in insulin and its co-crystallization with insoluble derivatives are used to modulate the time-action profile of the drug. This article traces the development of molecular variants and derivatives of insulin. It discusses future directions for further improvement in their properties to produce still better insulin therapeutics for tight glycemic control.

Insulin Therapy: Current Alternatives

In normal humans, blood glucose and insulin are maintained within a narrow range despite wide variations in physical activity and dietary intake. At present, reproducing this pattern is an impossible task in type 1 diabetes and extremely difficult in type 2 DM. New approaches using novel insulin analogs and routes of administration, attempting to replicate physiological insulin secretion in diabetic patients, are improving the profiles of glucose levels and, thus, the quality of life. Ultra-short-acting insulin analogues and ultra-long-acting analogues are being used for prandial and basal effects with better results, lower prevalence of hypoglycemia, and, hopefully, fewer chronic complications. Non-invasive routes of administration are being developed. The most promising appears to be inhaled insulin according to studies demonstrating excellent control, apparently without significant side effects, although in relatively short-term trials. Longer-term studies to assure the safety are still necessary before recommending its extended use. This is an extensive, up-to-date review of recent advances in insulin therapy.

Novel insulins: expanding options in diabetes management

Management of type 1 and type 2 diabetes mellitus with intensive insulin therapy usually includes an intermediate- or long-acting basal component for between-meal and nocturnal glycemic control, together with preprandial bolus injections of a short-acting insulin for control of meal-stimulated increases in serum glucose levels. Although the ideal basal/bolus insulin combination has yet to be found, recent developments may provide safer and more effective options. Two new short-acting semisynthetic analogs--insulin lispro and insulin aspart--can be administered as preprandial bolus injections closer to mealtime than regular human insulin, thereby synchronizing insulin administration and food absorption. In clinical trials, postprandial increases in blood glucose levels were significantly less after treatment with insulin lispro or insulin aspart than with premeal regular insulin. Because of their short duration of action, a slightly greater basal insulin supply may be needed when insulin lispro or insulin aspart is used. Inhalation devices for aerosolized regular human insulin offer another alternative to premeal subcutaneous bolus injections. Inhaled insulin is absorbed more rapidly than subcutaneous regular insulin and may therefore be given closer to mealtime. For basal therapy, insulin glargine, a new long-acting analog, is absorbed more slowly after subcutaneous administration than are conventional neutral protamine Hagedorn (NPH) and ultralente insulin, and has a relatively flat metabolic effect. Clinical trials indicate that insulin glargine is at least as effective as NPH insulin and ultralente insulin, and is associated with a reduced risk of nocturnal hypoglycemia. Other long-acting analogs, such as fatty acid acylated insulins, have been tested in animal models and are being evaluated in clinical studies.

Hybrid insulin cocrystals for controlled release delivery

The ability to tailor the release profile of a drug by manipulating its formulation matrix offers important therapeutic advantages. We show here that human insulin can be cocrystallized at preselected ratios with the fully active lipophilically modified insulin derivative octanoyl-N(epsilon)-LysB29-human insulin (C8-HI). The cocrystal is analogous to the NPH (neutral protamine Hagedorn) crystalline complex formed with human insulin, which is commonly used as the long-acting insulin component of diabetes therapy. The in vitro and in vivo release rates of the cocrystal can be controlled by adjusting the relative proportions of the two insulin components. We identified a cocrystal composition comprising 75% C8-HI and 25% human insulin that exhibits near-ideal basal pharmacodynamics in somatostatin-treated beagle dogs. The dependence of release rate on cocrystal ratio provides a robust mechanism for modulating insulin pharmacodynamics. These findings show that a crystalline protein matrix may accommodate a chemical modification that alters the dissolution rate of the crystal in a therapeutically useful way, yet that is structurally innocuous enough to preserve the pharmaceutical integrity of the original microcrystalline entity and the pharmacological activity of the parent molecule.

Recombinant DNA technology in the treatment of diabetes: insulin analogs

After more than half a century of treating diabetics with animal insulins, recombinant DNA technologies and advanced protein chemistry made human insulin preparations available in the early 1980s. As the next step, over the last decade, insulin analogs were constructed by changing the structure of the native protein with the goal of improving the therapeutic properties of it, because the pharmacokinetic characteristics of rapid-, intermediate-, and long-acting preparations of human insulin make it almost impossible to achieve sustained normoglycemia. The first clinically available insulin analog, lispro, confirmed the hopes by showing that improved glycemic control can be achieved without an increase in hypoglycemic events. Two new insulin analogs, insulin glargine and insulin aspart, have recently been approved for clinical use in the United States, and several other analogs are being intensively tested. Thus, it appears that a rapid acceleration of basic and clinical research in this arena will be seen, which will have direct significance to both patients and their physicians. The introduction of new short-acting analogs and the development of the first truly long-acting analogs and the development of analogs with increased stability, less variability, and perhaps selective action, will help to develop more individualized treatment strategies targeted to specific patient characteristics and to achieve further improvements in glycemic control. Data on the currently available and tested analogs, as well as data on those currently being developed, are reviewed.

Time-action profile of the soluble, fatty acid acylated, long-acting insulin analogue NN304

AIMS

To compare the pharmacokinetic and pharmacodynamic properties of subcutaneously injected NN304, a novel long-acting insulin analogue, to NPH-insulin during euglycaemic glucose clamps in 11 healthy volunteers.

METHODS

On three study days NN304 was injected in three different doses (0.15, 0.3, 0.6 U/kg body weight), while NPH-insulin (0.3 U/kg) was injected in identical dose on two other days.

RESULTS

Injection of NN304 resulted in a linear and proportional increase in total NN304 concentrations (AUC0-1440 min: 0.15 U/kg: 344+/-43, 0.3 U/kg: 666+/-82, 0.6 U/kg: 1295+/-210 nmol/l; P<0.001). Maximal concentrations (609+/-140, 1046+/-283, 2033+/-460 pmol/l; P<0.001) were reached after 4-6 h. The metabolic response (expressed as maximal glucose infusion rates (GIR)) induced by subcutaneous injection of NN304 did not show the pronounced peak seen with NPH-insulin in an identical dose: GIRmax 3.2+/-1.1 vs. 4.4+/-1.8 mg/kg/min (P<0.05 for 0.3 U/kg NN304 vs. NPH-insulin; mean of both study days with NPH-insulin, all others not significant). NN304 also showed a slower onset of action, as indicated by a significantly higher tmax (446+/-162 vs. 359+/-175 min) and lower AUC0-240min (0.5+/-0.3 vs. 0.8+/-0.4 g/kg/240min; P<0.05, respectively). The three different doses of NN304 induced a significantly different glucose consumption in the first 720 min after injection (AUC0-720 min 1.1+/-0.6, 1.9+/-0.8, 1.7+/-0.8 g/kg; P<0.05 for 0.15 U/kg), but not over the whole study period (AUC0-1440 min 1.8+/-1.1, 3.1+/-1.3, 2.8+/-1.4 g/kg).

CONCLUSIONS

Injection of NN304 at different doses resulted in an increase in total NN304 concentration in a linear dose-response effect and a more even metabolic effect than NPH-insulin. However, we found no clear dose-response in its metabolic effect.

Insulin analogs with improved pharmacokinetic profiles

The aim of insulin replacement therapy is to normalize blood glucose in order to reduce the complications of diabetes. The pharmacokinetics of the traditional insulin preparations, however, do not match the profiles of physiological insulin secretion. The introduction of the rDNA technology 20 years ago opened new ways to create insulin analogs with altered properties. Fast-acting analogs are based on the idea that an insulin with less tendency to self-association than human insulin would be more readily absorbed into the systemic circulation. Protracted-acting analogs have been created to mimic the slow, steady rate of insulin secretion in the fasting state. The present paper provides a historical review of the efforts to change the physicochemical and pharmacological properties of insulin in order to improve insulin therapy. The available clinical studies of the new insulins are surveyed and show, together with modeling results, that new strategies for optimal basal-bolus treatment are required for utilization of the new fast-acting analogs.