Panel discussion on achieving glycemic control

This discussion contains excerpts from the satellite symposium, "Achieving Better Glycemic Control Through Management of Mealtime Glucose," presented at the American Association of Clinical Endocrinologists Tenth Annual Meeting and Clinical Congress in San Antonio, Texas, May 2, 2001.

Insulinotropic meglitinide analogues

The loss of early-phase insulin secretion is an important and early event in the natural history of type 2 diabetes. Because a normal pattern of insulin secretion is essential for the effective control of postprandial metabolism, a rational basis for the development of agents that target early-phase insulin release exists. Conventional oral hypoglycaemic agents do not target, or adequately control, postprandial glycaemia. The emergence of new classes of oral agent with a more specific mode of action provides, for the first time, an opportunity to restore early-phase insulin release. One such drug class is the meglitinide analogues (repaglinide, nateglinide, and mitiglinide). These drugs are ideally suited for combination use with metformin. They could also prove effective in combination with a thiazolidinedione, a drug class that targets insulin resistance. Exogenous insulin is frequently required in the late management of type 2 diabetes. However, one hope for newer combinations of diabetic drugs is that the functional life of the beta cell can be extended, thereby delaying the need for insulin injections.

Nateglinide therapy for type 2 diabetes mellitus

OBJECTIVE

To review the pharmacology, pharmacokinetics, dosing guidelines, adverse effects, drug interactions, and clinical efficacy of nateglinide.

DATA SOURCES

Primary and review articles regarding nateglinide were identified by MEDLINE search (from 1966 to January 2001); abstracts were identified through the Institute for Scientific Information Web of Science (from 1995 to January 2001) and the American Diabetes Association; additional information was obtained from the nateglinide product information.

STUDY SELECTION/DATA EXTRACTION

All articles and meeting abstracts identified from the data sources were evaluated and all information deemed relevant was included in this review. Much of the information was from abstracts or the product labeling, since few clinical studies have been published in the medical literature.

DATA SYNTHESIS

Nateglinide is a novel nonsulfonylurea oral antidiabetic agent that stimulates insulin secretion from the pancreas. It has a rapid onset and short duration of action, allowing administration before a meal to reduce postprandial hyperglycemia. Improvement in glycemic control with nateglinide monotherapy has been demonstrated in patients not previously treated with antidiabetic medications. Greater improvement in glycemic control was observed when nateglinide was administered in combination with metformin.

CONCLUSIONS

Nateglinide is similar to repaglinide, but has a quicker onset of action, quicker reversal, and does not usually require dosage titration. Based on the pharmacodynamics of nateglinide and repaglinide, nateglinide produces a more rapid postprandial increase in insulin secretion, and its duration of response is shorter than that of repaglinide. The risk of postabsorptive hypoglycemia should be lower than with either sulfonylureas or repaglinide.

[New molecules]

Presentation of six drugs: clopidogrel, raloxifene, mecillinam, natiglinide and repaglinide, pneumococcal conjugate vaccine. For each, positive and negative arguments, questions on hold and rating.

Rapid acting insulinotropic agents: restoration of early insulin secretion as a physiologic approach to improve glucose control

The loss of early insulin secretion appears to be a critical event in the deterioration in glucose tolerance during the development of type 2 diabetes. There is therefore a strong rationale for developing new antidiabetic agents aimed at restoring or replacing early prandial insulin secretion and thereby curbing mealtime glucose excursions in patients with type 2 diabetes. Four such new agents are either now available (repaglinide and nateglinide) or in clinical development (KAD-1229 and BTS 67 582). Preclinical studies suggest that each of these new insulinotropic agents share a common receptor/effector mechanism with the sulfonylureas (SUs) but that each may have distinct characteristics that differentiate them from the SUs and from each other. Nateglinide and KAD-1229 clearly stimulate biphasic insulin secretion in vitro and in vivo and their effects are rapidly reversible, whereas the effects of repaglinide and BTS 67 582 are prolonged well beyond their removal from perfusion media in vitro or their clearance in vivo. Available data from human studies indicate that the pharmacokinetics of repaglinide and nateglinide are similar, i.e., they are both rapidly absorbed and eliminated, but consistent with findings from animal studies, the insulinotropic and glucose-lowering effects of repaglinide are slower in onset and more prolonged than those of nateglinide. Repaglinide and nateglinide have been shown to be safe and well-tolerated in patients with type 2 diabetes and to produce clinically-meaningful reductions of HbA1c, both alone and in combination with agents with complementary modes of action (e.g., metformin and thiazolidinediones). Because these new agents can potentially bring patients to near normoglycemia without an undue risk of hypoglycemia, they are important additions to the therapeutic armamentarium.

[New drugs]

Presentation of six drugs: clopidogrel, raloxifene, mecillinam, natiglinide and repaglinide, pneumococcal conjugate vaccine. For each, positive and negative arguments, questions on hold and rating.

[Ability of novel non-competitive glutamate receptor blocking agents to weaken motor disorders in animals]

Action of mono- and dication derivatives of phenylcyclohexyl was compared with effects of known NMDA-antagonists memantine and dizocilpine. Seizures induced with the NMDA were effectively prevented both by mono- and dications, whereas against the kainate seizures dication alone was effective. Anticataleptic activity was much stronger in monocations, and the side effect of the substances under study on motor co-ordination was obviously weaker than in dizocilpine. Thereupon, the phenylcyclohexyl derivatives might be regarded as potential means for treatment of parkinsonism and other motor disorders.

Randomized dose ranging study of the reduction of fasting and postprandial glucose in type 2 diabetes by nateglinide (A-4166)

OBJECTIVE

This randomized crossover double-blind placebo-controlled study aimed to assess the efficacy of nateglinide (A-4166), a novel phenylalanine-derived insulin secretagogue, in type 2 diabetic subjects while fasting and 5 min before a standard meal.

RESEARCH DESIGN AND METHODS

A single dose of nateglinide (60, 120, or 180 mg) or placebo was given to eight diet-treated overnight-fasted type 2 diabetic patients and to seven patients 5 min before a standard breakfast. Plasma glucose, radioimmunoassay insulin, and nateglinide were measured at baseline and for a further 180 min.

RESULTS

The time-averaged 180-min postdose mean decrease in fasting plasma glucose concentration was greater after nateglinide (1.8 mmol/l; 95% CI 1.5-2.0) than after placebo (0.7 mmol/l; 95% CI 0.3-1.2) (P < 0.001). Hypoglycemia did not develop in any of the subjects. Insulin concentrations increased 1.5-, 1.8-, and 1.9-fold with the 60-, 120-, and 180-mg doses, respectively (P < 0.001), peaking approximately 30 min after the dose. Nateglinide concentrations peaked after approximately 30 min, decreasing to 21% of peak by 180 min. In the meal test, the mean increase (2.9 mmol/l, 2.3-3.6) in plasma glucose over 180 min after placebo was reduced by 1.8 mmol/l (P < 0.001) with the two higher doses of nateglinide.

CONCLUSIONS

A single dose of nateglinide administered to diet-treated type 2 diabetic patients with fasting hyperglycemia increased insulin secretion and reduced fasting glucose without hypoglycemia. Administered 5 min before a meal, nateglinide reduced the postprandial glucose excursion by 64%. With its rapid onset and short duration of action, nateglinide is a promising oral prandial therapy in type 2 diabetes.

Nateglinide

The pharmacology, pharmacokinetics, clinical efficacy, adverse effects, interactions, and dosage of nateglinide are reviewed. Nateglinide is an oral hypoglycemic agent approved for use alone or in combination with metformin as an adjunct to diet and exercise for the treatment of type 2 diabetes mellitus. Nateglinide, an amino acid derivative of D-phenylalanine, stimulates the secretion of insulin by binding to the ATP potassium channels in pancreatic beta cells. The result is an increase in beta-cell calcium influx, which leads to rapid, short-lived insulin release. The drug is rapidly and completely absorbed in the small intestine. The estimated bioavailability is 72%. Nateglinide is highly bound to plasma proteins, is metabolized extensively by the liver, and has an elimination half-life of 1.4 hours. Several clinical trials of nateglinide, alone and in combination with other oral hypoglycemic agents, have found the drug to be safe, effective, and well tolerated. The most common adverse effects are nausea, diarrhea, dizziness, and lightheadedness. There is a potential for interactions between nateglinide and medications affected by the cytochrome P-450 isoenzyme system. Dosage regimens ranging from 60 to 240 mg have been evaluated. The maximum effective dosage is 120 mg taken 10 minutes before meals three times a day. Nateglinide is an alternative to second-generation sulfonylureas for the treatment of type 2 diabetes mellitus. Additional comparative trials are needed to fully elucidate nateglinide's role.

Importance of early insulin secretion: comparison of nateglinide and glyburide in previously diet-treated patients with type 2 diabetes

OBJECTIVE

This study compared the effects of nateglinide, glyburide, and placebo on postmeal glucose excursions and insulin secretion in previously diet-treated patients with type 2 diabetes.

RESEARCH DESIGN AND METHODS

This randomized, double-blind, placebo-controlled multicenter study was conducted in 152 patients who received either nateglinide (120 mg before three meals daily, n = 51), glyburide (5 mg q.d. titrated to 10 mg q.d. after 2 weeks, n = 50), or placebo (n = 51) for 8 weeks. Glucose, insulin, and C-peptide profiles during liquid meal challenges were measured at weeks 0 and 8. At weeks -1 and 7, 19-point daytime glucose and insulin profiles, comprising three solid meals, were measured.

RESULTS

During the liquid-meal challenge, nateglinide reduced the incremental glucose area under the curve (AUC) more effectively than glyburide ( = -4.94 vs. -2.71 mmol. h/l, P < 0.05), whereas glyburide reduced fasting plasma glucose more effectively than nateglinide ( = -2.9 vs. -1.0 mmol/l, respectively, P < 0.001). In contrast, C-peptide induced by glyburide was greater than that induced by nateglinide ( = +1.83 vs. +0.95 nmol. h/l, P < 0.01), and only glyburide increased fasting insulin levels. During the solid meal challenges, nateglinide and glyburide elicited similar overall glucose control ( 12-h incremental AUC = -13.2 vs. -15.3 mmol. h/l), but the insulin AUC induced by nateglinide was significantly less than that induced by glyburide ( 12-h AUC = +866 vs. +1,702 pmol. h/l, P = 0.01).

CONCLUSIONS

This study demonstrated that nateglinide selectively enhanced early insulin release and provided better mealtime glucose control with less total insulin exposure than glyburide.

Gacyclidine (Beaufour-Ipsen)

Beaufour-Ipsen is developing gacyclidine (GK-11) for the potential treatment of traumatic brain injury. Phase II clinical trials of the compound for this indication had been completed as of October 1999 and the company is looking for a partnership before undertaking further clinical development for this and, possibly, other indications [344879], [346265], [386763]. Phase II trials for acute spinal cord injury gave disappointing results and development for this indication has been discontinued [344879].

Nateglinide: a new rapid-acting insulinotropic agent

The United Kingdom Prospective Diabetes Study has shown that tight glycaemic control significantly reduces microvascular complications in Type 2 diabetes, but the effects on macrovascular complications were less impressive and did not reach statistical significance. Epidemiological studies have shown that post-prandial hyperglycaemia, rather than fasting hyperglycaemia, is more closely related to cardiovascular complications. It is, therefore, possible that previous studies may have overlooked the possible benefits of tight control of post-prandial hyperglycaemia as an important factor in reducing the cardiovascular mortality. Nateglinide is a novel D-phenylalanine derivative that inhibits ATP-sensitive K+ channels in pancreatic beta-cells in the presence of glucose and thereby restores first phase insulin response in patients with Type 2 diabetes. This helps in reducing post-prandial glucose excursion. Combination studies with metformin have shown it to be effective in controlling hyperglycaemia. While metformin reduces the basal plasma glucose, nateglinide helps in controlling post-prandial peaks. Nateglinide provides a new therapeutic option for treating Type 2 diabetes by specifically targeting post-prandial hyperglycaemia.

Immediate-Type allergy against human insulin associated with marked eosinophilia in type 2 diabetic patient

We describe a type 2 diabetic patient who showed immediate-type allergy against human insulin associated with marked eosinophilia at initial insulin therapy. Three months after initiation of insulin therapy, he noticed itchy skin wheals at the site of the insulin injection. Laboratory data at that time showed marked eosinophilia (2,512 /mm3) and progression of renal dysfunction. Skin test with semisynthetic human insulin and protamine sulfate resulted in local immediate skin reactions such as itchy erythema and wheals. Histopathology of the biopsy specimen from skin showed perivascular infiltration of lymphocytes and numerous eosinophils in the dermis and subcutaneous fat. Although the titer of total IgE antibody was within normal range, that of insulin-specific IgE antibody was high. Insulin administration was discontinued to preserve his insulin secretion, and stable control of his hyperglycemia was obtained by initiating nateglinide treatment (360 mg/day). His itchy skin lesions disappeared within two weeks after cessation of the insulin therapy and both eosinophilia and renal dysfunction gradually improved. Although the widespread use of human insulin in diabetic patients has greatly reduced the incidence of insulin allergy, the possibility of human insulin allergy should be kept in mind when initiating such therapy.

Early insulin release effectively improves glucose tolerance: studies in two rodent models of type 2 diabetes mellitus

AIM

Islet dysfunction, characterized by the loss of an acute insulin secretory response (AIR) to glucose is a well-established pathology of type 2 diabetes mellitus. Using oral insulin secreting agents with very different pharmacodynamic profiles, the present study was undertaken to test the hypothesis that, within the setting of an underlying insulin resistance, changes in the insulin response profile can differentially affect glycaemic control.

METHOD

The mildly insulin resistant high-fat fed Sprague Dawley (HF) rat and the very insulin resistant Zucker fatty (fa/fa) rat, chronically fitted with indwelling jugular cannula were subjected to an oral glucose load. Compounds were administered 5 min before the oral glucose load. Nateglinide (Nateg) was administered to elicit only an early insulin secretory response and glipizide (Glip) to elicit a later but greater insulin secretory response. Acetaminophen was used as a marker to assess for potential effects of these compounds on gastric emptying rates.

RESULTS

Nateg rapidly increased early insulin release (from -5 to 0) while the effects on total insulin release were similar to those in the controls and glucose excursions were eliminated in both diabetic models with no evidence of sustained hypoglycaemia. Conversely, Glip did not affect early insulin release but increased total insulin release (- 15 to 120 min), but only after the oral glucose load. Glip partially curbed glucose excursions in the mildly insulin resistant HF rodent and was totally ineffective in the very insulin resistant Zucker rat. The differential effects could not be attributed to effects on gastric emptying rates.

CONCLUSION

These data support the importance of early insulin release in type 2 diabetes mellitus and indicate that, independent of the level of insulin resistance, stimulating insulin release early and briefly provides for more effective and tighter glycaemic control than increasing insulin exposure to a greater magnitude later.

Phenylcyclohexene and phenylcyclohexadiene substituted compounds having retinoid antagonist activity

Retinoids are natural and synthetic analogues of the hormone retinoic acid. Systemic retinoid agonist therapy is usually associated with toxic side effects, such as mucocutaneous toxicity, which may be alleviated by the use of topical retinoid antagonists. We report the synthesis and biological activity of a new series of potent, RAR-specific antagonists substituted with phenylcyclohexene and phenylcyclohexadiene groups.

Clinical efficacy of new thiazolidinediones and glinides in the treatment of type 2 diabetes mellitus

A central finding of the UKPDS was that in type 2 diabetic patients, tight glycemic control with HbA1c targets as close to the normal range as possible must be achieved to further reduce diabetes related-complications, -mortality, and -cardiovascular disease, highlighting the need for new, optimized treatment strategies. With a focus on clinical efficacy, this paper discusses the results from the 20 major therapeutical trials published in the years 1997-1999, that evaluated the new insulinsensitizing thiazolidinediones Rosiglitazone and Pioglitazone and the new insulin-releasing potassium channel blockers Repaglinide and Nateglinide. While for Nateglinide, promising, but only preliminary data is available at current, Rosiglitazone, Pioglitazone, and Repaglinide have been shown appropriate for both mono- and combination therapy with current standard drug treatment of type 2 diabetes. Similar to the known, older antidiabetic drugs, the new agents discussed have comparable blood glucose lowering potentials with a dose-related capacity of 0.5 to 1.5% HbA1c reduction. These beneficial effects were both seen in drug-naive patients previously treated with diet only and in combination therapies where patients had previous antidiabetic standard drug treatment suggesting effectiveness of glitazones and glinides also in more advanced stages of the disease. Problems with adverse effects appeared minor although long-range implications of weight gain, edema, lowering of hemoglobin, increase of total cholesterol for the glitazones, and hypoglycemia for glinides warrant further consideration. What becomes clear from the variety of most recent mono- and combination treatment studies with as much as five different classes of antidiabetic drugs is that individually tailored therapies that recognize quality of life parameters and target the predominant features of metabolic pathology (such as early postprandial versus fasting hyperglycemia, degree of insulin resistance, progressive loss of 1-cell function) may become a feasible goal in the future.

Nateglinide alone and in combination with metformin improves glycemic control by reducing mealtime glucose levels in type 2 diabetes

OBJECTIVE

To evaluate the efficacy and tolerability of nateglinide and metformin alone and in combination in type 2 diabetic patients inadequately controlled by diet, focusing on changes in HbA1c, fasting plasma glucose (FPG), and mealtime glucose excursions.

RESEARCH DESIGN AND METHODS

In this randomized double-blind study, patients with an HbA1c level between 6.8 and 11.0% during a 4-week placebo run-in received 24 weeks' treatment with 120 mg nateglinide before meals (n = 179), 500 mg metformin three times a day (n = 178), combination therapy (n = 172), or placebo (n = 172). HbA1c and FPG were evaluated regularly, and plasma glucose levels were determined after Sustacal challenge at weeks 0, 12, and 24. Hypoglycemia and other adverse events were recorded.

RESULTS

At study end point, HbA1c was reduced from baseline with nateglinide and metformin but was increased with placebo (-0.5, -0.8, and +0.5%, respectively; P < or = 0.0001). Changes in FPG followed the same pattern (-0.7, -1.6, and +0.4 mmol/l; P < or = 0.0001). Combination therapy was additive (HbA1c -1.4% and FPG -2.4 mmol/l; P < or = 0.01 vs. monotherapy). After Sustacal challenge, there was a greater reduction in mealtime glucose with nateglinide monotherapy compared with metformin monotherapy or placebo (adjusted area under the curve [AUC]0-130 min -2.1, -1.1, and -0.6 mmol x h(-1) x l(-1); p < or = 0.0001). An even greater effect was observed with combination therapy (AUC0-130 min -2.5 mmol x h(-1) x l(-1); P < or = 0.0001 vs. metformin and placebo). All regimens were well tolerated.

CONCLUSIONS

Nateglinide and metformin monotherapy each improved overall glycemic control but by different mechanisms. Nateglinide decreased mealtime glucose excursions, whereas metformin primarily affected FPG. In combination, nateglinide and metformin had complementary effects, improving HbA1c, FPG, and postprandial hyperglycemia.

Meglitinide analogues in the treatment of type 2 diabetes mellitus

Type 2 diabetes mellitus is a complex heterogenous metabolic disorder in which peripheral insulin resistance and impaired insulin release are the main pathogenetic factors. The rapid response of the pancreatic beta-cells to glucose is already markedly disturbed in the early stages of type 2 diabetes mellitus. The consequence is often postprandial hyperglycaemia, which seems to be extremely important in the development of secondary complications, especially macrovascular disease. Therefore one of the main aims of treatment is to minimise blood glucose oscillations and attain near-normal glycosylated haemoglobin levels. Meglitinide analogues belong to a new family of insulin secretagogues which stimulate insulin release by inhibiting ATP-sensitive potassium channels of the beta-cell membrane via binding to a receptor distinct from that of sulphonylureas (SUR1/KIR 6.2). The pharmacokinetic and pharmacodynamic properties of repaglinide, the first drug of these new antihyperglycaemic agents on the market, and of nateglinide, which will be available soon, differ markedly from the currently used sulphonylureas [mainly glibenclamide (glyburide) and glimepiride]. Repaglinide and nateglinide are absorbed rapidly, stimulate insulin release within a few minutes, are rapidly metabolised in the liver and are mainly excreted in the bile. Therefore, following preprandial administration of these drugs, insulin is more readily available during and just after the meal. This leads to a significant reduction in postprandial hyperglycaemia without the danger of hypoglycaemia between meals. The short action of these compounds and biliary elimination makes repaglinide and nateglinide especially suitable for patients with type 2 diabetes mellitus who would like to have a more flexible lifestyle, need more flexibility because of unplanned eating behaviour (e.g. geriatric patients) or in whom one of the other first-line antidiabetic drugs, i.e. metformin, is strictly contraindicated (e.g. nephropathy with creatinine clearance < or = 50 ml/min). Meglitinide analogues act synergistically with metformin and thiazolidinediones (pioglitazone and rosiglitazone) and can be also combined with long-acting insulin (NPH insulin at bedtime). Therefore, these drugs enrich the palette of antidiabetic drugs and make the treatment more flexible and better tolerated, which both add to better metabolic control and support the empowerment and compliance of the patient. However, this will only be the case if the patient and the diabetes care team are trained for this new therapeutic schedule and the healthcare system is able to pay for these rather expensive drugs.

Impairment of early insulin response after glucose load, rather than insulin resistance, is responsible for postprandial hyperglycemia seen in obese type 2 diabetes: assessment using nateglinide, a new insulin secretagogue

The insulin secretory pattern as a phenotype of type 2 diabetes is an impairment in the rapid, pulsatile secretion of insulin in response to a rise in blood glucose after meal-intake. The restoration of endogenous rapid insulin secretion after oral glucose load was established for the first time by using nateglinide, which is a newly developed insulin secretagogue, in obese patients with type 2 diabetes mellitus. It was clearly demonstrated that with nateglinide, serum insulin levels were quickly raised, and glycemic response curves were almost normalized with the same amount of insulin secretion during 180 min. Therefore, the lack of rapid, pulsatile secretion of insulin in response to glycemic rise after oral glucose load, rather than insulin resistance, is responsible for postprandial glycemic response in obese type 2 diabetes patients.

[Pharmacological properties of nateglinide, rapid-onset/short-duration insulinotropic agent, in the treatment of type 2 diabetes]

An early defect in Type 2 diabetes is the loss of acute insulin release after food intake, which causes prolonged elevation of postprandial glucose levels. Suppressing postprandial hyperglycemia is considered to be very important for preventing diabetic complications. Sulfonylureas are well-known insulin secretagogues and have been widely used in the treatment of Type 2 diabetes. These agents, however, do not appear to be able to ameliorate impairment of the first phase of insulin secretion and postprandial hyperglycemia. Nateglinide, which is a derivative of D-phenylalanine, is a non-sulfonylurea insulin secretagogue. Although the in vitro insulin-releasing effect of nateglinide is similar to that of sulfonylureas, its hypoglycemic effect is more rapid and short lasting. The in vivo unique pharmacodynamic profile of nateglinide is likely to result from its rapid absorption and elimination. This novel antidiabetic agent has made it possible to compensate for the impaired first phase insulin response and thus suppresses postprandial hyperglycemia. In clinical trials, nateglinide reduced prandial glucose excursion and improved early phase of insulin release dose-dependently after 12 weeks treatment. Nateglinide is a highly physiologic mealtime glucose regulator, which rapidly increases insulin secretion when taken before meals, mimicking early-phase insulin release lost in patients with Type 2 diabetes.

Effects of the new oral hypoglycaemic agent nateglinide on insulin secretion in Type 2 diabetes mellitus

AIMS

The new non-sulphonylurea oral hypoglycaemic agent nateglinide has been shown to enhance insulin secretion in animals and in healthy human volunteers and thus offers a potential advance in the treatment of Type 2 diabetes mellitus. This study examined whether nateglinide can enhance insulin secretion, and particularly the first phase insulin response, in patients with Type 2 diabetes.

METHODS

A double-blind, placebo-controlled trial, examining the effects of a single oral dose of 60 mg nateglinide, given 20 min prior to an intravenous glucose tolerance test (IGTT), on insulin secretion in 10 otherwise healthy Caucasian men with recently diagnosed Type 2 diabetes (duration since diagnosis 0-44 months).

RESULTS

Insulin secretion (both overall and first phase) was significantly increased by nateglinide (P < 0.001), as were C-peptide (P < 0.001) and proinsulin (P < 0.001) secretion. Overall glucose concentrations following glucose challenge were lower after nateglinide than after placebo (P = 0.05).

CONCLUSIONS

Nateglinide significantly increases insulin secretion in Type 2 diabetic patients, in particular restoring the first phase insulin response. Further study is necessary to determine the effects of chronic administration on insulin secretion and blood glucose concentration.