Diabetes Care 30:890-895, 2007 DOI: 10.2337/dc06-1732 © 2007 by the American Diabetes Association
Effects of Vildagliptin on Glucose Control Over 24 Weeks in Patients With Type 2 Diabetes Inadequately Controlled With Metformin
1 Diabetes and Endocrinology Unit, Department of General Medicine, San Raffaele Scientific Institute, Vita-Salute San Raffaele University, Milan, Italy Address correspondence and reprint requests to Alan J. Garber, MD, PhD, Baylor College of Medicine, 6550 Fannin St., Suite 1045, Houston, TX 77030. E-mail: agarber{at}bcm.tmc.edu
OBJECTIVEWe sought to evaluate the efficacy and safety of vildagliptin, a new dipeptidyl peptidase-4 inhibitor, added to metformin during 24 weeks of treatment in patients with type 2 diabetes.
RESEARCH DESIGN AND METHODSThis was a double-blind, randomized, multicenter, parallel group study of a 24-week treatment with 50 mg vildagliptin daily (n = 177), 100 mg vildagliptin daily (n = 185), or placebo (n = 182) in patients continuing a stable metformin dose regimen (
RESULTSThe between-treatment difference (vildagliptin placebo) in adjusted mean change (AM CONCLUSIONSVildagliptin is well tolerated and produces clinically meaningful, dose-related decreases in A1C and FPG as add-on therapy in patients with type 2 diabetes inadequately controlled by metformin.
Abbreviations: AM
Vildagliptin is a new oral antidiabetes drug acting as a potent and selective inhibitor of dipeptidyl peptidase-4 (DPP-4), the enzyme responsible for the rapid degradation of circulating glucagon-like peptide-1. Early studies suggest that vilgagliptin improves islet function in patients with type 2 diabetes by increasing both - and ß-cell responsiveness to glucose (1,2). In 12-week studies, vildagliptin given as monotherapy in drug-naïve patients with type 2 diabetes was shown to decrease fasting plasma glucose (FPG) and postprandial glucose (PPG) (3,4). Furthermore, a phase II study of vildagliptin added to metformin suggested that combining this DPP-4 inhibitor with metformin may be a particularly effective approach to improving glycemic control in patients with type 2 diabetes (5). Metformin is the most commonly prescribed first-line antidiabetes drug worldwide, but due to the progressive worsening of blood glucose control during the natural history of type 2 diabetes, combination therapy usually becomes necessary (6). Therefore, it was of interest to ascertain the efficacy and tolerability of vildagliptin in combination with metformin in a larger phase III clinical trial. Accordingly, the present 24-week, multicenter, randomized, parallel-group, placebo-controlled study examined the effects of vildagliptin in patients with type 2 diabetes inadequately controlled with metformin monotherapy.
This was a 24-week, double-blind, randomized, placebo-controlled, parallel-group study conducted at 109 centers in the U.S. (n = 79), France (n = 8), Italy (n = 6), and Sweden (n = 16). Patients with type 2 diabetes inadequately controlled with metformin monotherapy attended one screening visit (visit 1, week 4), during which inclusion/exclusion criteria were assessed. Eligible patients were randomized at visit 2 (week 0) to receive 50 mg vildagliptin daily (as a q.d. dose), 100 mg vildagliptin daily (as equally divided doses), or placebo. Efficacy and tolerability were assessed during four additional visits, at weeks 4, 12, 16, and 24 of treatment.
The study enrolled patients with type 2 diabetes who had been treated with metformin monotherapy for at least 3 months and who had been on a stable dose of
Patients were excluded if they had a history of type 1 or secondary forms of diabetes, acute metabolic diabetes complications within the past 6 months, congestive heart failure requiring pharmacologic treatment, myocardial infarction, unstable angina, or coronary artery bypass surgery within the previous 6 months. Liver disease such as cirrhosis or chronic active hepatitis also precluded participation, as did renal disease or renal dysfunction as suggested by elevated serum creatinine levels
Study assessments All adverse events (AEs) were recorded. Patients were provided with glucose monitoring devices and supplies and instructed on their use. Hypoglycemia was defined as symptoms suggestive of low blood glucose confirmed by self-monitored blood glucose measurement <3.1 mmol/l plasma glucose equivalent. Severe hypoglycemia was defined as any episode requiring the assistance of another party. All laboratory assessments were made by central laboratories. All assessments except A1C were performed by Bio Analytical Research Corporation (BARC). Assays were performed with standardized and validated procedures according to good laboratory practice. A1C measurements were performed by either BARC-EU (Ghent, Belgium) for European subjects or by the National Glycohemoglobin Standardization Program network laboratory, Diabetes Diagnostics Laboratory (Columbia, MO), or Covance-US (Indianapolis, IN) for U.S. subjects. All samples from any single patient were measured by the same laboratory.
Data analysis All participants provided written informed consent. The protocol was approved by the independent ethics committee/institutional review board at each study site, and the study was conducted using good clinical practice in accordance with the Declaration of Helsinki.
Patient disposition from screening through study end point is summarized in supplemental Fig. 1 (available in an online appendix at http://dx.doi.org/10.2337/dc06-1732), and baseline demographic and metabolic characteristics of the primary ITT population are reported in Table 1. A total of 544 patients were randomized; 416 patients comprised the primary ITT population, and >83% of patients in each treatment group completed the study. In the primary ITT population, the groups were well balanced at baseline, with A1C averaging 8.4% and FPG averaging 9.9 mmol/l in the combined cohort. Participants were predominantly Caucasian and obese, with a mean age of 54 years and mean disease duration of 6.2 years. Patients had been using metformin at a stable dose for an average of 17 months; the mean metformin dose was 2,100 mg/day. Standard breakfast meal test was performed at weeks 0 and 24 in a subgroup of 163 patients with characteristics representative of the whole ITT population, of whom 53 were treated with 50 mg vildagliptin daily, 56 with 100 mg daily, and 54 were in the placebo group.
Efficacy All reported efficacy data derive from the primary ITT population. Similar findings were obtained in the ITT population for all the variables measured (data not shown). The time courses of mean A1C and FPG during the 24-week treatment with 50 mg vildagliptin daily, 100 mg daily, or placebo added to metformin are depicted in Fig. 1A and B, respectively. The mean baseline A1C was 8.4 ± 0.1% in both groups of patients randomized to vildagliptin and 8.3 ± 0.1% in patients randomized to placebo. The adjusted mean change (AM ) A1C was 0.2 ± 0.1% in patients receiving placebo and 0.5 ± 0.1 and 0.9 ± 0.1% in patients receiving 50 mg and 100 mg vildagliptin daily, respectively. The between-treatment difference (vildagliptin placebo) was 0.7 ± 0.1% with 50 mg vildagliptin daily (P < 0.001) and 1.1 ± 0.1% with 100 mg vildagliptin daily (P < 0.001).
To allow better appreciation of the response to treatment, supplemental Fig. 2 depicts the number of patients in each treatment group who experienced a deterioration of glycemic control (
Responder rates (percentage of patients achieving end point A1C <7.0%) were also calculated and stratified according to baseline A1C levels. In patients with baseline A1C
Baseline FPG averaged 9.7 ± 0.2, 9.9 ± 0.2, and 10.1 ± 0.2 mmol/l in patients randomized to 50 mg vildagliptin daily, 100 mg vildagliptin daily, and placebo, respectively. A dose-related decrease in FPG was also observed, and a modest increase in FPG was seen in patients receiving placebo added to metformin (AM
Standard meal tests
The AM
At baseline, the ß-cell function index (i.e., the ratio of the 2-h ISR AUC to the 2-h glucose AUC) averaged 18.7 ± 1.1, 20.0 ± 1.0, and 20.3 ± 1.1 pmol/min per m2 per mmol/l in patients randomized to 50 mg vildagliptin daily, 100 mg vildagliptin daily, and placebo, respectively. After 24 weeks of treatment, these measures increased significantly in vildagliptin-treated patients; the between-treatment difference in the AM
Lipids and body weight
As shown in supplemental Fig. 4B, relative to baseline, body weight did not change significantly after 24 weeks of treatment with 50 mg vildagliptin daily (AM
The change in body weight from baseline to study end point in the three treatment groups was also assessed by a categorical analysis and expressed as the percentage of patients experiencing a meaningful increase in body weight (>1 kg), a meaningful decrease in body weight (>1 kg), or weight neutrality (
Safety and tolerability The SAEs occurring in patients in the 50 mg vildagliptin treatment group were one instance each of coronary artery disease, deep venous thrombosis, acute uveitis, and renal calculus; the first three named SAEs led to discontinuation. The SAEs occurring in patients in the 100 mg vildagliptin treatment group were one instance each of silent ischemia, anginal attack, left limb acute ischemia, stroke and suspected gastrointestinal infection (in the same patient), urinary tract infection, and diarrhea with dehydration. The patient who experienced the anginal attack discontinued the study. The SAEs occurring in patients receiving placebo added to metformin were one instance each of squamous cell carcinoma of the skin, inverted T-wave, skeletal cancer, coronary artery blockage, bronchitis with exacerbated asthma, uterine fibroids, transient ischemic attack and left eye hemorrhage (in the same patient), and coronary artery disease with unstable angina pectoris. The patients with SAEs of inverted T-wave and skeletal cancer discontinued the study. One patient in each treatment group experienced one mild hypoglycemic event. No severe (grade 2) hypoglycemic events were reported, and no deaths occurred during the study.
Both systolic and diastolic blood pressure tended to decrease during the study in each treatment group, and the decrease in diastolic blood pressure in patients receiving 100 mg vildagliptin daily (AM
This study demonstrates that the DPP-4 inhibitor vildagliptin at doses of 50 or 100 mg daily, when added to metformin monotherapy, results in a clinically significant and dose-related decrease in FPG and A1C. These effects are associated with an improvement in measures of ß-cell function, with no weight gain and no increase in the incidence of hypoglycemia. Furthermore, the combination is very well tolerated with no major safety concerns identified in this study. Thus, it appears that combining vildagliptin with metformin is an effective and well-tolerated approach to treating patients with type 2 diabetes. These results are consistent with those observed in an earlier phase II study conducted in a similar patient population (5). In the present study, the 50 mg daily dose of vildagliptin resulted in a placebo-adjusted decrease in A1C of 0.8% at week 12, and A1C remained stable for the remainder of the study. The 100 mg daily dose of vildagliptin provided additional efficacy, achieving a placebo-adjusted A1C reduction of 1.2% at week 12, with no appreciable changes in A1C thereafter. In the aforementioned phase II study, the placebo-subtracted A1C in patients receiving 50 mg vildagliptin daily added to metformin was 0.7%, and this was 1.1% after 52 weeks of treatment, reflecting deterioration of glycemic control in the patients receiving placebo and continuing metformin treatment. Although firm conclusions cannot be drawn from comparisons between studies performed in different patient populations with different designs, the efficacy of vildagliptin added to metformin appears to be within the range of results of similar previous studies with other oral antidiabetes agents (913) and with the injectable incretin mimetic exenatide (14). Supplemental Table 2 summarizes these published findings. A particularly noteworthy finding of this study is the improvement in measures of ß-cell function seen in patients treated with vildagliptin. While absolute plasma insulin levels were essentially unchanged by vildagliptin treatment (see supplemental Fig. 3C and D), both vildagliptin dose regimens elicited similar, approximately threefold increases in ß-cell function relative to placebo when expressed as ISR relative to glucose (Fig. 1B). The lack of a dose-response in this parameter describing ß-cell function reflects the fact that 50 mg vildagliptin was given just before the breakfast meal test in both the 50 and 100 mg vildagliptin daily dose regimen. Indeed, essentially complete inhibition of DPP-4 is produced by either dose for >4 h (the duration of meal test sampling), as well as by doses as low as 10 mg, and it is the duration of DPP-4 inhibition that is dose related (16). The improvement in the ß-cell function index used in the present study is in agreement with previous reports demonstrating a significant effect on other measures, such as the corrected insulin response following meal tests (4). Although a variety of mechanisms may contribute to the therapeutic efficacy of DPP-4 inhibitors (15), the present findings suggest an important role for improved ß-cell function. Consistent with previous experience, vildagliptin was very well tolerated. Hypoglycemia was rarely encountered, and vildagliptin elicited no clinically meaningful mean increase in body weight despite the improvement in overall glycemic control. The observation in this study that the frequency of gastrointestinal side effects in patients receiving vildagliptin tended to be lower than that in patients receiving placebo and continuing metformin requires confirmation and further investigation. Overall, the safety profile of vildagliptin was well characterized in this study. From this study it may be concluded that vildagliptin elicits clinically significant and dose-related decreases in FPG, PPG, and, accordingly, A1C when added to metformin monotherapy. In view of its efficacy and excellent tolerability profile, vildagliptin may be a useful addition to the therapeutic armamentarium for treatment of patients with type 2 diabetes.
List of investigators: France: P. Darmon, R. Duhirel, M. Levy, A. Penfornix, M. Remigy, A.M. Salandini, C. LeDevehat, and R. Mira; Italy: F. Pacini, E. Bosi, G. Testa, A. Colao, W. Donadon, and F. Mollo; Sweden: M. Landin-Olsson, M. Svensson, P.A. Jansson, S. Efendic, I. Lager, A. Nilsson, U. Adamsson, A. Hänni, B.G. Polhem, S. Rössner, A. Sjoberg, M.S. Dahl, G. Stromblad, A. Norrby, T. Lindström, and P.S. Nicol; U.S.: D. Kereiakes, E. Roth, M. Rendell, R. Lipetz, A. Philis-Tsimikas, K. Vijayaraghan, N. Messina, P. McCoullough, L. Ralph, N. Fraser, J. LeLevier, P. Davis, J. McGill, J. Holcomb, A. Mooradian, L. Doerhing, D. Aboud, W. Drummond, S. El Hafi, C. Horn, J. Mitchell, J. Rosenstock, G. Serfer, K. Roberts, J. Capo, C. Strong, M. Rodebaugh, A. Villafria, M. Houston, S. Pohl, S. Jones, J. Minkoff, J. Willcox, N. Bohannon, A. Lewin, J. Bruner, S. Daisley, D. McCluskey, T. Isakov, J. Kang, S. Ong, J. Cohen, R. Montoro, J. Fidelholtz, A. Forker, R. Cady, W. Zigrang, L. Anastasi, F. Civitarese, K. Hershon, D. Calhoun, A. Garber, S. Schneider, L. Olansky, S. Schwartz, K. Ward, R. Mayfield, X. Pi-Sunyer, K. Bordenave, D. Kendall, A. Taylor, S. Yates, E. Zawada, C. Fleming, D. Smith, T. Howard, R. Egelhof, N. Shealy, J. Rhudy, S. Greco, A. Rauba, G. Brar, N. Lunde, J. Quigley, R. Farsad, D. Nadeau, R. Pratley, J. Pullman, and T. Moretto.
This study was funded by Novartis Pharmaceuticals Corporation. We gratefully acknowledge the investigators and staff at the 109 participating centers, as well as the editorial assistance of Beth Dunning Lower, PhD. A list of the investigators is provided in the APPENDIX.
Published ahead of print at http://care.diabetesjournals.org on 2 February 2007. DOI: 10.2337/dc06-1732. Clinical trial reg. no. NCT00099892, clinicaltrials.gov. E.B. has received a research grant and honoraria from Novartis. R.P.C., C.C., and E.R. are employees and stockholders of Novartis. A.J.G. has received grants and research support from Novartis and is a member of the advisory board for Novartis. Additional information for this article can be found in an online appendix at http://dx.doi.org/10.2337/dc06-1732. A table elsewhere in this issue shows conventional and Système International (SI) units and conversion factors for many substances. The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 U.S.C Section 1734 solely to indicate this fact. Received for publication August 15, 2006. Accepted for publication December 19, 2006.
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