Emerging Treatments and Technologies ORIGINAL ARTICLE

Randomized Dose Ranging Study of the Reduction of Fasting and Postprandial Glucose in by (A-4166)

1 ϩ FIONA M. GRIBBLE, MA, BM, BCH, DPHIL ATP-sensitive K (KATP) channels in the 2 SUSAN E. MANLEY, PHD plasma membrane of the pancreatic ␤-cell 2 JONATHAN C. LEVY, BSC, MD (3–5). Closure of KATP channels enables ␤-cells to depolarize, thereby triggering the opening of voltage-gated calcium channels, calcium influx, and re- OBJECTIVE — This randomized crossover double-blind placebo-controlled study aimed to lease (6–8). Although not containing a assess the efficacy of nateglinide (A-4166), a novel phenylalanine-derived insulin secretagogue, group, nateglinide binds to in type 2 diabetic subjects while fasting and 5 min before a standard meal. the same site in the ␤-cell as gliben- RESEARCH DESIGN AND METHODS clamide and has been shown to displace — A single dose of nateglinide (60, 120, or 180 3 mg) or placebo was given to eight diet-treated overnight-fasted type 2 diabetic patients and to [ H] binding from insuli- seven patients 5 min before a standard breakfast. Plasma glucose, radioimmunoassay insulin, noma cell membranes (4,9,10). Its action and nateglinide were measured at baseline and for a further 180 min. in vitro and in animal studies is, however, more rapidly reversible than that of glib- RESULTS — The time-averaged 180-min postdose mean decrease in fasting plasma glucose enclamide (4,10,11). concentration was greater after nateglinide (1.8 mmol/l; 95% CI 1.5–2.0) than after placebo (0.7 K channels are also found in a va- mmol/l; 95% CI 0.3–1.2) (P Ͻ 0.001). did not develop in any of the subjects. ATP Insulin concentrations increased 1.5-, 1.8-, and 1.9-fold with the 60-, 120-, and 180-mg doses, riety of extrapancreatic tissues, including respectively (P Ͻ 0.001), peaking ϳ30 min after the dose. Nateglinide concentrations peaked cardiac, skeletal, and smooth muscle and after ϳ30 min, decreasing to 21% of peak by 180 min. In the meal test, the mean increase (2.9 some neurons. The roles of these channels mmol/l, 2.3–3.6) in plasma glucose over 180 min after placebo was reduced by 1.8 mmol/l (P Ͻ are incompletely understood, but their 0.001) with the two higher doses of nateglinide. opening in cardiac muscle during hyp- oxia may provide some protection against CONCLUSIONS — A single dose of nateglinide administered to diet-treated type 2 diabetic ischemia. These KATP channels exhibit patients with fasting hyperglycemia increased insulin secretion and reduced fasting glucose different sensitivities to without hypoglycemia. Administered 5 min before a meal, nateglinide reduced the postprandial due to the presence of alternative types glucose excursion by 64%. With its rapid onset and short duration of action, nateglinide is a promising oral prandial therapy in type 2 diabetes. of sulfonylurea receptor subunit (12). Therefore, some sulfonylureas (e.g., glib- Diabetes Care 24:1221–1225, 2001 enclamide) are effective blockers of KATP channels from a range of tissues, whereas others (e.g., and ) ␤ he hyperglycemia of type 2 diabetes ureas in current use (1). In developing are more -cell–specific (12). Nateglinide is also relatively specific for the , is associated with a relative impair- novel therapies without this drawback, ␤ ϳ T ment of insulin secretion and re- one strategy has been to produce rapid- inhibiting -cell KATP channels with 50 sponds, in many cases, to the therapeutic acting compounds with a short biological times greater potency than smooth mus- use of oral insulin secretagogues such as half-life. cle KATP channels (13); however, it re- sulfonylureas. These , however, are Nateglinide (A-4166) is a novel rapid- mains controversial whether blocking commonly associated with hypoglycemic acting nonsulfonylurea insulin secreta- KATP channels in cardiac and smooth side effects due to the prolonged pharma- gogue (2). Like the sulfonylureas, it muscle produce clinically significant side cological action of many of the sulfonyl- stimulates insulin secretion by blocking effects. Recent studies in type 2 diabetic sub- ●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●●● jects have shown that nateglinide en- From the 1Department of Clinical Biochemistry, Addenbrooke’s Hospital, Cambridge; and the 2Diabetes hances insulin release in response to an Research Laboratories, Radcliffe Infirmary, Oxford, U.K. Address correspondence and reprint requests to Dr. Jonathan C. Levy, The Radcliffe Infirmary NHS Trust, intravenous glucose tolerance test (14) Woodstock Road, Oxford OX2 6HE. E-mail: [email protected]. and that it is well tolerated during 7 days Received for publication 16 January 2001 and accepted in revised form 30 March 2001. of continuous therapy (15). We present J.C.L. has received a consulting fee from for participation in the U.K. West Midlands Advisory here a dose-response study of the effects Board. Novartis is currently marketing nateglinide in the U.K. under the trade name Starlix. ϩ of nateglinide on plasma glucose and in- Abbreviations: KATP, ATP-sensitive K channel; UKPDS, U.K. Prospective Diabetes Study. A table elsewhere in this issue shows conventional and Syste`me International (SI) units and conversion sulin when given to diet-treated type 2 factors for many substances. diabetic subjects in both the fasting and

DIABETES CARE, VOLUME 24, NUMBER 7, JULY 2001 1221 Nateglinide in type 2 diabetes

Table 1—Patient characteristics Biochemistry Plasma glucose was determined by a Fasting study Meal study hexokinase method on a Cobas MIRA dis- crete analyzer (Roche Diagnostica, Herts, n 87U.K.). Plasma radioimmunoassay insulin Sex (M/F) 4/4 6/1 was measured in heparinized plasma by Ϯ Ϯ Age (years) 55 8558 double antibody radioimmunoassay, 2 Ϯ Ϯ BMI (kg/m ) 32.8 10.2 31.0 4.5 with Sepharose attached to the second Duration of diabetes (years) 1.3 (5–15) 7 (0.4–10) antibody for separation by decanting Fasting plasma glucose (mmol/l) 9.8 Ϯ 1.6 9.7 Ϯ 1.6 Ϯ Ϯ (Pharmacia, Milton Keynes, Bucks, U.K.). HbA1c (%) 7.4 1.2 7.1 1.2 Ϯ The insulin assay crossreacts 100% with Data are n, means SD, or median (range). intact proinsulins and ϳ90% with split prandial states. We used a double-blind randomized crossover placebo-controlled design to examine the effects of a single dose of 60, 120, or 180 mg of nateglinide.

RESEARCH DESIGN AND METHODS — The patients recruited were between the ages of 35 and 70 years and had type 2 diabetes treated with diet alone. Patients were excluded if they suf- fered from active cardiovascular disease or were women of child-bearing potential. Eight subjects participated in the fasting study, and seven subjects participated in the meal study. The patient characteris- tics are presented in Table 1. The protocol was approved by the Central Oxfordshire Research Ethics Committee. All subjects gave written informed consent.

Protocol Both studies used a double-blind ran- domized crossover placebo-controlled design. and placebo tablets, sup- plied by the manufacturer before the initiation of the study, were indistin- guishable and individually randomized. In the fasting study, subjects attended after an overnight fast on four occasions. Each subject took a single dose of either placebo or 60, 120, or 180 mg of nate- glinide orally in randomized order at time 0 min. Treatment was blinded to both pa- tient and investigators. Blood samples were collected at Ϫ10, Ϫ5, 0, 10, 20, 30, 45, 60, 90, 120, 150, and 180 min from ingestion of the tablets from a cannula in a distal vein that was arterialized by heating with an electric blanket. In the meal study, subjects attended after an overnight fast and were given a standard breakfast consisting of 56.6 g carbohydrate, 19.5 g protein, 11.5 fat, and 395 kcal at time 0 min, having taken a single dose of nateglinide 3–5 min prior Figure 1—Fasting plasma glucose (A), insulin (B), and nateglinide (C) profiles after oral ad- to this. Doses and sample times were the ministration of placebo (Œ)or60mg(Ⅺ), 120 mg (‚), or 180 mg (ϫ) nateglinide to type 2 same as in the fasting study. diabetic subjects.

1222 DIABETES CARE, VOLUME 24, NUMBER 7, JULY 2001 Gribble, Manley, and Levy proinsulins. Plasma nateglinide concen- trations were measured by Inveresk Re- search International (Edinburgh, U.K.). HBA1c was measured using the Bio-Rad Variant HPLC Haemoglobin Testing Sys- tem (Bio-Rad, Richmond, CA), certified by the National Glycohemoglobin Stan- dardization Program as comparable to the Diabetes Control and Complications Trial (normal range 4.7–6.4%).

Statistics For each study, the primary outcome measures were the plasma concentrations of glucose, insulin, and nateglinide after dosing. The glucose and nateglinide re- sponses were calculated as the incremen- tal or decremental time-averaged mean concentrations (trapezoidal area under the curve divided by the total time inter- val) during the 180-min sampling period. Insulin responses were calculated as pro- portional changes from baseline to take into account differences in insulin sensi- tivity between subjects. The overall insu- lin response is reported as the time- averaged mean of the proportional increase from 0 to 90 min in order to avoid the confounding effect of altered glucose concentrations in the second half of the study. Results are expressed as arithmetic means for glucose and nategli- nide concentrations and as geometric means for insulin responses; 95% CIs are shown in parentheses. Secondary out- come measures were the mean times to reach peak concentrations for insulin and nateglinide, calculated using the com- bined data for the three drug doses, and are presented as the geometric mean (95% CI). Analysis was performed using analysis of variance, with subject and pe- Figure 2—Postprandial plasma glucose (A), insulin (B), and nateglinide (C) profiles of type 2 riod as fixed variables and with trend tests diabetic subjects. The meal was started at time 0; 3–5 min earlier, the patients were given either across different doses. Residual plots placebo (Œ)or60mg(Ⅺ), 120 mg (‚), or 180 mg (ϫ) nateglinide. showed no marked deviation from nor- mality, so untransformed values were used. The analysis after logarithmic trans- of 0.7 mmol/l (95% CI 0.3–1.2) over the glinide, with proportional increases of formation yielded no significant differ- 3 h of continued fast, but a greater reduc- 1.48-fold (1.35–1.61), 1.76-fold (1.43– ences. Paired t tests between individual tion was achieved after administration of 2.09), and 1.89-fold (1.52–2.26) at 60, doses were performed when significant nateglinide, with no significant difference 120, and 180 mg, respectively (P Ͻ 0.001 differences were detected by analysis of between the three doses (Fig. 1A). The for trend across doses). Insulin concentra- variance. Analysis was performed using mean decrease in plasma glucose for the tions increased within 10 min after ad- SPSS release 6.1.4 for VAX/VMS (SPSS, combined doses of nateglinide was 1.8 ministration of the 120- and 180-mg Chicago, IL). mmol/l (1.5–2.0) (P Ͻ 0.001 vs. place- doses, reaching a peak at 29 min (25–34). bo). No biochemical or symptomatic hy- Nateglinide concentrations increased RESULTS poglycemia was experienced. The insulin within 10 min, with a time to peak of 42 profiles are shown in Fig. 1B. Insulin con- min (33–53). At 3 h, the nateglinide con- Fasting test centrations did not change significantly centration decreased to 21–22% of the Plasma glucose concentrations on pla- after administration of placebo but rose peak values at each dose (Fig. 1C). The cebo decreased by a time-averaged mean after administration of all doses of nate- 180-min time-averaged mean nategli-

DIABETES CARE, VOLUME 24, NUMBER 7, JULY 2001 1223 Nateglinide in type 2 diabetes nide concentrations were proportional and , the concentrations of rently great interest in developing therapies to the ingested dose (r ϭ 0.93, P Ͻ which, in a comparison study by Sartor that specifically target the postprandial 0.0001). et al. (16), reached peak values by 2–2.5 increase in glucose. slows intes- hours, were still present at concentrations tinal absorption of glucose but is associ- Meal test Ͼ80% of peak at 3 h, and did not reach ated with dose-related side effects that The mean increase in the plasma glucose 20% of peak concentrations until ϳ24 limit its acceptability to patients (18). Re- concentration during the 180-min period and 8 h, respectively. The insulin re- paglinide is a recently licensed short- after the meal was 2.9 mmol/l (2.3–3.6) sponse after administration of nateglinide acting insulin secretagogue that also on placebo, and this was reduced to 1.8 was prompt, producing a significant re- produces significant reductions in fasting (1.1–2.6), 1.1 (0.5–1.7), and 1.0 mmol/l duction in plasma glucose, but in accor- glycemia (19,20). Our results suggest that (0.2–1.9) after administration of the 60-, dance with the short plasma half-life of nateglinide has a similar rapid action and 120-, and 180-mg doses of nateglinide, thedrug,theinsulinresponsewasnotpro- elimination. At doses that do not produce respectively (P Ͻ 0.001 for trend across longed and, in these patients with fasting hypoglycemia in the fasting state, nate- doses, with no significant difference be- hyperglycemia, did not provoke hypogly- glinide improved the postprandial glu- tween the two higher doses) (Fig. 2A). cemia. Hypoglycemia is a recognized side cose excursion by a clinically significant The mean postprandial glucose during effect of standard sulfonylurea therapy. amount at all doses, reaching a 64% de- the 3-h period for the two combined In the U.K. Prospective Diabetes Study crease at the two higher doses. This rep- higher doses was reduced by 1.8 mmol/l, (UKPDS), 11% of patients taking chlor- resents an 18% reduction in the total i.e., by 64% compared with the postpran- propamide and 17% of patients taking glucose exposure during the 3 hours after dial increase on placebo. Plasma insulin glibenclamide experienced at least one the meal. concentrations also increased after the episode of symptomatic hypoglycemia In conclusion, nateglinide displays meal and were further enhanced by nate- per year in the first 10 years after diag- characteristics that are of potential use for glinide (Fig. 2B). The mean proportional nosis, and major hypoglycemia was the treatment of early type 2 diabetes. The increase in plasma insulin above the fast- recorded in 0.4% of the - present study demonstrates that the drug ing level during the first 90 min after the treated group and 0.5% of the gliben- stimulates a prompt insulin response in meal increased 3.3-fold (3.0–3.5) on pla- clamide-treated group during this period. type 2 diabetic subjects and results in a cebo, compared with 5.3-fold (4.1–6.6), The rate of hypoglycemia was greatest in clinically significant reduction of both 5.1-fold (4.2–6.0), and 6.2-fold (4.7– the earlier years of follow-up (1). Al- fasting hyperglycemia and postprandial 7.7) on 60, 120, and 180 mg of nategli- though chlorpropamide is rarely used be- glucose excursion. With these character- nide, respectively (P ϭ 0.001 for trend). cause of its very long elimination time, istics, the drug would be particularly At 3 h, the insulin concentrations after glibenclamide is still the most widely pre- suited to a preprandial dose regimen, al- nateglinide had decreased to concentra- scribed oral therapy for type 2 diabetes. lowing increased safety and more flexibil- tions similar to those seen on placebo, al- The importance of achieving tight ity in meal timing. though in the context of lower plasma glucose control at the earliest stages of glucose concentrations at this time point. type 2 diabetes emphasizes the need for Nateglinide concentrations (Fig. 2C) in- drugs that more effectively mimic the Acknowledgments— This study was con- creased within 10 min and reached a peak physiological insulin response to meals. ceived and conducted with the guidance of the at median 30 min (range 20–180). The The of nateglinide late Professor Robert Turner, who died unex- 180-min time-averaged mean nateglinide would allow repeated preprandial dosage pectedly before the preparation of this manu- concentrations over the first 90 min were with less danger of either drug accumula- script. We thank Beryl Barrow for nursing support, Pauline Sutton for insulin measure- proportional to the ingested dose (r ϭ tion or the development of hypoglycemia Ͻ ments, Robin Carter for glucose, and Dick Jelfs 0.74, P 0.0001). before the next meal. This study would for HBA . not exclude the possibility that a hypogly- 1c CONCLUSIONS — This study inves- cemic effect may occur in subjects treated tigated the effects of nateglinide at three more vigorously, to normal fasting plas- References different doses in diet-treated type 2 dia- ma glucose concentrations (for instance, 1. 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This allowed the assess- sion contributes significantly to the total phenylalanines and related compounds: a new class of oral hypoglycemic agents. 2. ment of direct effects of the drug on insu- glycemic exposure in type 2 diabetes, and J Med Chem 32:1436–1441, 1989 lin secretion. Nateglinide was absorbed although therapy with chronic long-act- 3. Akiyoshi M, Kakei M, Nakazaki M, Tana- rapidly and was 80% eliminated within ing sulfonylurea reduces fasting plasma ka H: A new hypoglycemic agent, A-4166, 3 h. This may be compared with the glucose, it has relatively little impact on inhibits ATP-sensitive potassium chan- short-acting sulfonylureas tolbutamide meal-related increases (17). There is cur- nels in rat pancreatic beta-cells. Am J

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