Lawrence Blonde, MD

From the Ochsner Diabetes Clinical Research Unit, Frank Riddick Diabetes Institute, Department of Endocrinology, Ochsner Medical Center, New Orleans, LA (Dr. Blonde), and AstraZeneca, Gaithersburg, MD (Drs. Sheehan, Barrett, and Garcia-Sanchez).

 

Abstract

• Objective: To evaluate diabetes care quality measure attainment, specifically, blood glucose and blood pressure (BP) control, with saxagliptin, a dipeptidyl peptidase-4 inhibitor, and dapagliflozin, a sodium-glucose cotransporter-2 inhibitor, added singly or as dual add-on therapy in patients with type 2 diabetes inadequately controlled with metformin alone.
• Methods: Analysis of a phase 3, randomized, double-blind, active-controlled, parallel-group trial was conducted. Patients were randomized 1:1:1 to receive saxagliptin 5 mg/d plus dapagliflozin 10 mg/d, saxagliptin 5 mg/d, or dapagliflozin 10 mg/d as add-on to metformin 1500 to 2000 mg/d. Assessments included attainment of individual and composite glycated hemoglobin (A1C) and BP measures at 24 weeks of treatment.
• Results: Compared with single add-on saxagliptin or dapagliflozin, dual add-on saxagliptin plus dapagliflozin to metformin was associated with significantly more patients attaining the individual quality measures of A1C < 7% and A1C < 8%. Similarly, dual add-on saxagliptin plus dapagliflozin was associated with significantly more patients attaining the composite quality measures A1C < 7% and BP < 140/90 mm Hg and A1C < 8% and BP < 140/90 mmHg (vs saxagliptin plus metformin).
• Conclusion: Dual add-on saxagliptin plus dapagliflozin to metformin was associated with a higher proportion of patients achieving glycemic and BP quality measures compared with single add-on saxagliptin or dapagliflozin.

Assessment of performance is a focus of many health care organizations as a means to evaluate and improve the quality of health care. Standardized performance measures have been developed to improve quality of care as well as to allow for comparative assessment of health plans and to support pay for performance models [1]. A widely used set of performance measures is the Healthcare Effectiveness Data and Information Set or HEDIS [2,3], measures that are maintained by the National Committee for Quality Assurance [4,5] and used by most US health plans [6].

Type 2 diabetes (T2D) is a focus of quality measure assessment and performance improvement because of its high prevalence, substantial personal and economic impact on society, high morbidity and mortality, and because it is a condition that requires coordinated care. Important outcome measures for diabetes include blood glucose control and blood pressure (BP) control. HEDIS measures for T2D include a glycated hemoglobin (A1C) > 9%, indicating poor glucose control, < 8%, indicating good control, and < 7%, a more stringent measure of good glycemic control. The HEDIS measure for BP in T2D is < 140/90 mm Hg, which is considered good BP control. All of these HEDIS measures are currently or were previously (A1C < 7%) endorsed by the National Quality Forum [1,7–10]. Endorsement of a quality measure by the NQF indicates that the measure has been thoroughly evaluated, meets specific criteria, and is based on recognized standards of care grounded in evidence-based medicine [1].

A number of oral agents are utilized in the treatment of diabetes. Saxagliptin, an oral dipeptidyl peptidase-4 (DPP-4) inhibitor, and dapagliflozin, an oral sodium-glucose cotransporter-2 (SGLT-2) inhibitor, are indicated as adjuncts to diet and exercise in adults with T2D [11,12]. Saxagliptin inhibits DPP-4, and thereby reduces fasting and postprandial glucose concentrations by preventing degradation of the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide [13]. Dapagliflozin reduces blood glucose concentrations by inhibiting glucose reabsorption in the proximal tubule of the kidney, which results in enhanced urinary glucose excretion [14]. Because their mechanisms of action are glucose-dependent, both saxagliptin and dapagliflozin have a low intrinsic potential to cause hypoglycemia [13,14]. In a randomized, double-blind study of patients with T2D inadequately controlled with metformin, Rosenstock et al assessed the efficacy and safety of dual add-on of saxagliptin plus dapagliflozin versus saxagliptin and dapagliflozin added on alone (ClinicalTrials.gov identifier, NCT01606007) [15]. The dual add-on therapy resulted in a greater adjusted mean reduction from baseline in A1C at week 24 (–1.47%) compared with either saxagliptin (–0.88%) or dapagliflozin (–1.20%) alone added to metformin; the difference for dual add-on saxagliptin plus dapagliflozin to metformin vs. single add-on saxagliptin and single add-on dapagliflozin was –0.59% (P < 0.001) and –0.27% (P = 0.0166), respectively. The incidence of adverse events was similar across the 3 treatment groups, and hypo-glycemia was infrequent (1%), with no reports of severe hypoglycemia events (symptomatic events with glucose ≤ 54 mg/dL requiring assistance).

In this paper, we assess the attainment of diabetes quality measures among patients in this study, specifically, measures of glycemic and BP control.

Methods

Study Design and Patients

This was a post hoc analysis of a phase 3, multicenter, randomized, double-blind, active-controlled, parallel-group, 24-week study. Details of the study design, inclusion/exclusion criteria, and primary results have been previously reported [15]. In brief, men and women aged ≥ 18 years with T2D poorly controlled (A1C 8.0%–12.0%) with metformin monotherapy were randomized 1:1:1 to receive saxagliptin 5 mg/d and dapagliflozin 10 mg/d, saxagliptin 5 mg/d and placebo, or dapagliflozin 10 mg/d and placebo on a background of metformin extended release 1500 to 2000 mg/d (Figure 1). Patients were required to be on stable metformin (≥ 1500 mg/d) for ≥ 8 weeks before screening and to have a C-peptide concentration ≥ 1.0 ng/mL and a body mass index ≤ 45.0 kg/m². The trial was designed and monitored in accordance with the ethical principles of Good Clinical Practice as defined by the International Conference on Harmonisation and the Declaration of Helsinki. Institutional review boards or ethics committees at each study site approved the protocol, and all patients gave written informed consent.

Quality Measure Assessment

Individual measures assessed included the proportion of patients with A1C < 7%, A1C < 8%, A1C > 9%, and BP < 140/90 mm Hg. Composite measures assessed includedthe proportion of patients with A1C < 7% and BP < 140/90 mm Hg and the proportion of patients with A1C < 8% and BP < 140/90 mm Hg.

Antihypertensive or cholesterol-lowering medication use was not controlled for in this study. Patients were maintained on their prescribed dosing regimen for antihypertensive and cholesterol-lowering medications, with adjustments as needed per the standard of care for their diagnosis. Treatment outcomes for A1C < 7%, < 8%, or > 9% were prespecified. The BP treatment outcome was also prespecified per the statistical analysis plan; however, a change to the HEDIS quality measure treatment outcome for BP during the clinical study resulted in this analysis being no longer relevant. Therefore, analyses of the currently endorsed quality measures for BP were conducted post hoc. Quality measure assessments for A1C and BP treatment outcomes were conducted using data from the 24-week, double-blind treatment period.

Statistical Analysis

P values for the differences in proportion of patients with individual treatment outcomes and composite treatment outcomes with saxagliptin plus dapagliflozin plus metformin versus saxagliptin plus metformin or dapagliflozin plus metformin were calculated using Fisher’s exact test. The numerator and denominator for each percentage are the number of responders and the number of patients with non-missing values in the treatment group at the corresponding baseline category, respectively, and are not corrected for baseline A1C. Because some patients experienced improvement in A1C during the lead-in period and could have already been at treatment goal at baseline, a sensitivity analysis excluding these patients was completed. Results are presented for the total number of patients with non-missing values in the treatment group, as well as patients with non-missing values in the treatment group who did not meet quality measure criteria at baseline. The number needed to treat (NNT) was calculated for all comparisons reaching statistical significance.

 

Results

Patients

Patient disposition, baseline demographics, and disease characteristics have been previously published [15]. A total of 534 patients were randomized to saxagliptin plus dapagliflozin plus metformin (n = 179), saxagliptinplus metformin (n = 176), or dapagliflozin plus metformin (n = 179) and received ≥ 1 dose of study medication. Patient demographics and baseline disease characteristics were generally balanced across all 3 treatment groups (Table). Mean age across the 3 treatment groups was 54 years, and there was a generally equal distribution of men and women. The mean known duration of T2D across the 3 treatment groups was 7.6 years, and mean baseline A1C was 8.94%. At baseline, 93% to 98% of patients had A1C > 7%, 74% to 82% had A1C > 8%, and 39% to 44% had A1C > 9%. At baseline, 18% to 28% of patients had BP > 140/90 mm Hg.

Individual Quality Measures

A significantly greater proportion of patients attained A1C < 7% (good glycemic control) with the dual add-on of saxagliptin plus dapagliflozin to metformin (41.8%) compared with saxagliptin plus metformin (16.6%, P < 0.001; NNT 4, 95% confidence interval [CI], 3–6) or dapagliflozin plus metformin (23.1%, P < 0.001; NNT 5, 95% CI, 4–11; Figure 2). The data were similar when the analysis excluded patients with baseline A1C < 7% (proportions of patients: 40.8% vs 15.6% vs 21.1%; P < 0.001 for both; NNTs 4 [95% CI 3–6] and 5 [95% CI 3–10]).

The dual addition of saxagliptin plus dapagliflozin to metformin resulted in a significantly greater proportion of patients achieving A1C < 8.0% compared with saxagliptin plus metformin (71.2% vs 49.1%; P < 0.001; NNT 5 [95% CI 3–8]) or dapagliflozin plus metformin (60.1%; P = 0.033; NNT 9 [95% CI 5–85]; Figure 2). Similar results (proportions of patients: 66.4% vs 40.0% vs 51.9%; P ≤ 0.02; NNTs 4 [95% CI 3–7]) and 7 [95% CI 4–34]) were attained when the analysis excluded patients with baseline A1C < 8.0%.

Significantly fewer patients had A1C > 9% (a measure of poor glycemic control) with saxagliptin plus dapagliflozin plus metformin (12.4%) compared with saxagliptin plus metformin (22.3%; P = 0.017; NNT –10 [95% CI –50 to –6]; Figure 2). The proportion of patients with A1C > 9% was similar for both regimens that included dapagliflozin (12.4% vs 10.4%; P = 0.616).

No significant difference was observed among treatment groups in the proportion of patients with BP < 140/90 mm Hg (Figure 2). However, most patients had BP < 140/90 mm Hg (72%–82%) at baseline, which was generally maintained at week 24.

Composite Quality Measures

A significantly greater proportion of patients attained the composite of A1C < 7% and BP < 140/90 mm Hg with saxagliptin plus dapagliflozin plus metformin (33.5%) compared with saxagliptin plus metformin (13.1%; P < 0.001; NNT 5 [95% CI 4–9]) or dapagliflozin plus metformin (18.6%; P = 0.002; NNT 7 [95% CI 4–17]; Figure 3). Results were similar when patients already at these goals at baseline were excluded from the analysis (32.4% vs 12.1% vs 16.3%; P < 0.001 for both; NNTs 5 [95% CI 4–9] and 6 [95% CI 4–14]).

A significantly greater proportion of patients achieved the composite of A1C < 8% and BP < 140/90 mm Hg with saxagliptin plus dapagliflozin plus metformin compared with saxagliptin plus metformin (56.8% vs 37.1%; P < 0.001; NNT 5 [95% CI 3–11]). Although not statistically significant, a numerically greater proportion of patients achieved A1C < 8% and BP < 140/90 mmHg with saxagliptin plus dapagliflozin plus metformin compared with dapagliflozin plus metformin (56.8% vs 50.0%; P = 0.237; Figure 4). Results were similar when patients already at these goals at baseline were excluded from the analysis (55.9% vs 30.2% [P < 0.001] vs 42.6% [P = 0.025]; NNTs 4 [95% CI 3–7] and 8 [95% CI 4–55]).

Discussion

This post hoc analysis evaluated attainment of glycemic and BP quality measures for diabetes. A significantly greater proportion of patients achieved the individual quality measures of A1C < 7% and A1C < 8% with dual add-on saxagliptin plus dapagliflozin to metformin compared with single add-on saxagliptin or dapagliflozin to metformin after 24 weeks. Similar results were seen when the analysis excluded patients with A1C < 7% and < 8% at baseline. All measures of good glycemic control had clinically relevant NNTs ≤ 10 after 24 weeks with saxagliptin plus dapagliflozin plus metformin compared with saxagliptin or dapagliflozin plus metformin, regardless of baseline status. Very few patients experienced lackof improvement in glycemic control, evidenced by small proportions of patients with A1C > 9%.

 

There was little difference in BP between dual add-on saxagliptin plus dapagliflozin or single add-on saxagliptin or dapagliflozin to metformin. The proportion of patients who attained the BP quality measure of BP < 140/90 mm Hg was similar across the 3 treatments, as might be expected because most patients already met this target at baseline. However, as might be expected based on the mild diuretic effect and weight loss associated with SGLT-2 inhibitors [16,17], trends in BP favored groups treated with dapagliflozin.

Attainment of multiple treatment targets is desirable in reducing complications of diabetes. A significantly greater proportion of patients achieved both A1C < 7% and BP < 140/90 mm Hg when both saxagliptin and dapagliflozin were added to metformin compared with single-agent addition of either saxagliptin or dapagliflozin plus metformin. Similarly, a significantly greater proportion of patients achieved both A1C < 8% and BP < 140/90 mm Hg with dual addition of saxagliptin and dapagliflozin plus metformin compared with saxagliptin plus metformin. There was also a numerically greater number of patients who achieved both of these goals with triple therapy compared with dapagliflozin plus metformin, but this finding did not reach statistical significance. Clinically relevant NNT values ≤ 10 were observed for both composite outcomes for saxagliptin plus dapagliflozin plus metformin compared with saxagliptin plus metformin or dapagliflozin plus metformin after 24 weeks.

Despite advances in the medical management of T2D, a report published in 2013 showed that between 2007 and 2010, only 53% of patients achieved an A1C < 7.0% and only 19% simultaneously achieved all 3 American Diabetes Association (ADA) goals recommended for most patients at that time: A1C < 7.0%, BP < 130/80 mm Hg, and low-density lipoprotein cholesterol LDL-C < 100 mg/dL [18]. These data highlight a need for new approaches to help patients attain glycemic, BP, and cholesterol goals. Our results demonstrated that a higher proportion of patients attained glycemic and BP quality measures with dual add-on saxagliptin plus dapagliflozin compared with single add-on saxagliptin or dapagliflozin to metformin. As a result of recent updates for cholesterol management from the American College of Cardiology and the American Heart Association [19], attainment of a cholesterol level was retired as a diabetes quality measure and replaced with a recommendation for statin therapy use [20,21]. Although the current analysis did not include assessment of LDL, DPP-4 inhibitors have demonstrated neutral effects on lipids [22,23], and SGLT-2 inhibitors have demonstrated generally modest increases in LDL-C (placebo-adjusted change from baseline: 4.5%–8.0% for canagliflozin 100 and 300 mg/d, 3.9% for dapagliflozin 10 mg, and 2.3%–4.2% for empagliflozin 10 and 25 mg/d) [12,24,25], as well as increases in high-density lipoprotein cholesterol and reductions in triglycerides [26].

Current ADA guidelines recommend an individualized, stepwise approach to treatment with sequential addition of single oral antihyperglycemic agents for patients who do not achieve their glycemic goal in 3 months [27]. Although T2D may progress at different rates in different patients, T2D does generally progress over time [28], and the ADA and American Association of Clinical Endocrinologists treatment guidelines recommend initial dual add-on therapy for individuals with higher A1C, which is suggestive of more advanced disease [27,29]. For individuals requiring initial combination therapy, guidelines note that antihyperglycemic agents that have a low risk of hypoglycemia and low potential for weight gain should be preferentially selected [29]. Attainment of A1C ≤ 7%, the guideline recommendation considered appropriate for many patients, is associated with reductions in microvascular disease and, if attained soon after diagnosis of diabetes, studies have shown reductions in macrovascular disease with long-term follow-up [27,30,31]. However, it may be challenging to achieve A1C < 7% with the addition of single oral antihyperglycemic agents, especially in patients with higher A1C [32]. Less stringent A1C goals (eg, A1C < 8%) may be appropriate in individuals with a long duration of diabetes that is difficult to control, history of severe hypoglycemia, limited life expectancy, numerous comorbidities, and extensive complications or comorbidities, especially cardiovascular disease [27]. Given the shift toward individualized treatment plans with patient-specific treatment goals, it is valuable to understand how different treatment strategies effect attainment of guideline-recommended less stringent and more stringent glycemic targets that may be appropriate for certain patients.

 

In addition to quality measures that assess glucose lowering with pharmacotherapy, it is important to consider measures that assess other aspects of diabetes care. For example, quality measures related to hypoglycemia and hyperglycemia may help avoid potentially adverse glucose levels, and quality measures related to weight may provide insight on treatment and lifestyle efforts directed at weight loss and management. NQF-endorsed measures of hypoglycemia and hyperglycemia are currently moving through annual review and are paired measures, intended to be interpreted with respect to one another to ensure balanced outcomes [33,34]. This underscores the value of efficacious antihyperglycemic agents with low intrinsic potential for hypoglycemia. Although this analysis did not include quality measures related to hypoglycemia or weight, future studies evaluating these aspects of diabetes care will likely further contribute to a more comprehensive and holistic treatment approach.

In addition to assessing a broad range of quality measures, an important aspect of care to consider is patient affordability. Affordability for an individual patient will depend on access in the patient’s individual plan, the financial resources of the patient, and the potential for medical cost offsets from improved control of the patient’s disease. For example, fixed-dose combination products are associated with increased patient adherence and may increase pharmacy costs but decrease medical costs [35].

Limitations of this study include the post hoc design and that quality measure attainment was assessed over a shorter duration of time (24 weeks) than is commonly assessed in the real-world/community setting (~12 months).

Dual add-on therapy with oral antihyperglycemic agents that have complementary mechanisms of action should lead to enhanced reductions in A1C. The results reported here and from the primary study, in which saxagliptin and dapagliflozin added to metformin significantly reduced mean A1C from baseline to week 24 compared with single add-on saxagliptin or dapagliflozin [15], showed that greater reductions in A1C were attained with the coadministration of saxagliptin and dapagliflozin. The glucuretic effect of SGLT-2 inhibitors has been associated with increased plasma glucagon concentrations and increased endogenous glucose production, which may impair the full glucose-lowering potential of SGLT-2 inhibitors [36,37]. Administering saxagliptin with dapagliflozin as dual therapy was shown to blunt the rise in plasma glucagon caused by dapagliflozin [38], and this may have contributed to the greater glucose control achieved with dual add-on of these 2 antihyperglycemic drugs [15].

By targeting multiple aspects of the underlying pathophysiology in T2D, greater improvements in A1C can be achieved. Dual add-on saxagliptin plus dapagliflozin to metformin resulted in a greater proportion of patients achieving NQF-endorsed HEDIS quality measures, as well as A1C < 7% (no longer an NQF-endorsed measure). As health care shifts to a more value-based payment structure, measuring quality outcomes will assume a greater role in guiding decision making and influence the care that patients receive. Understanding how antihyperglycemic medication regimens affect quality measures can help clinicians make informed decisions.

 

Corresponding author: Lawrence Blonde, MD, Ochsner Diabetes Clinical Research Unit, Frank Riddick Diabetes Institute, Department of Endocrinology, Ochsner Medical Center, New Orleans, LA.

Funding/support: This study was supported by AstraZeneca. Medical writing support for the preparation of this manuscript was provided by Lauren D’Angelo, PhD, and Janet Matsuura, PhD, from Complete Healthcare Communications, LLC (Chadds Ford, PA), with funding from AstraZeneca.

Financial disclosures: Dr. Blonde has received grant and research support from AstraZeneca, Jansen Pharmaceuticals, Lexicon Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis and has received honoraria for participating as a speaker from AstraZeneca, Janssen Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis as well as honoraria for consultant work from AstraZeneca, GlaxoSmithKline, Intarcia Therapeutics, Janssen Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis. R. Garcia-Sanchez is an employee of AstraZeneca. J. Sheehan and Y. C. Barrett were employees of AstraZeneca at the time of this research.

From the Ochsner Diabetes Clinical Research Unit, Frank Riddick Diabetes Institute, Department of Endocrinology, Ochsner Medical Center, New Orleans, LA (Dr. Blonde), and AstraZeneca, Gaithersburg, MD (Drs. Sheehan, Barrett, and Garcia-Sanchez).

 

Abstract

• Objective: To evaluate diabetes care quality measure attainment, specifically, blood glucose and blood pressure (BP) control, with saxagliptin, a dipeptidyl peptidase-4 inhibitor, and dapagliflozin, a sodium-glucose cotransporter-2 inhibitor, added singly or as dual add-on therapy in patients with type 2 diabetes inadequately controlled with metformin alone.
• Methods: Analysis of a phase 3, randomized, double-blind, active-controlled, parallel-group trial was conducted. Patients were randomized 1:1:1 to receive saxagliptin 5 mg/d plus dapagliflozin 10 mg/d, saxagliptin 5 mg/d, or dapagliflozin 10 mg/d as add-on to metformin 1500 to 2000 mg/d. Assessments included attainment of individual and composite glycated hemoglobin (A1C) and BP measures at 24 weeks of treatment.
• Results: Compared with single add-on saxagliptin or dapagliflozin, dual add-on saxagliptin plus dapagliflozin to metformin was associated with significantly more patients attaining the individual quality measures of A1C < 7% and A1C < 8%. Similarly, dual add-on saxagliptin plus dapagliflozin was associated with significantly more patients attaining the composite quality measures A1C < 7% and BP < 140/90 mm Hg and A1C < 8% and BP < 140/90 mmHg (vs saxagliptin plus metformin).
• Conclusion: Dual add-on saxagliptin plus dapagliflozin to metformin was associated with a higher proportion of patients achieving glycemic and BP quality measures compared with single add-on saxagliptin or dapagliflozin.

Assessment of performance is a focus of many health care organizations as a means to evaluate and improve the quality of health care. Standardized performance measures have been developed to improve quality of care as well as to allow for comparative assessment of health plans and to support pay for performance models [1]. A widely used set of performance measures is the Healthcare Effectiveness Data and Information Set or HEDIS [2,3], measures that are maintained by the National Committee for Quality Assurance [4,5] and used by most US health plans [6].

Type 2 diabetes (T2D) is a focus of quality measure assessment and performance improvement because of its high prevalence, substantial personal and economic impact on society, high morbidity and mortality, and because it is a condition that requires coordinated care. Important outcome measures for diabetes include blood glucose control and blood pressure (BP) control. HEDIS measures for T2D include a glycated hemoglobin (A1C) > 9%, indicating poor glucose control, < 8%, indicating good control, and < 7%, a more stringent measure of good glycemic control. The HEDIS measure for BP in T2D is < 140/90 mm Hg, which is considered good BP control. All of these HEDIS measures are currently or were previously (A1C < 7%) endorsed by the National Quality Forum [1,7–10]. Endorsement of a quality measure by the NQF indicates that the measure has been thoroughly evaluated, meets specific criteria, and is based on recognized standards of care grounded in evidence-based medicine [1].

A number of oral agents are utilized in the treatment of diabetes. Saxagliptin, an oral dipeptidyl peptidase-4 (DPP-4) inhibitor, and dapagliflozin, an oral sodium-glucose cotransporter-2 (SGLT-2) inhibitor, are indicated as adjuncts to diet and exercise in adults with T2D [11,12]. Saxagliptin inhibits DPP-4, and thereby reduces fasting and postprandial glucose concentrations by preventing degradation of the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide [13]. Dapagliflozin reduces blood glucose concentrations by inhibiting glucose reabsorption in the proximal tubule of the kidney, which results in enhanced urinary glucose excretion [14]. Because their mechanisms of action are glucose-dependent, both saxagliptin and dapagliflozin have a low intrinsic potential to cause hypoglycemia [13,14]. In a randomized, double-blind study of patients with T2D inadequately controlled with metformin, Rosenstock et al assessed the efficacy and safety of dual add-on of saxagliptin plus dapagliflozin versus saxagliptin and dapagliflozin added on alone (ClinicalTrials.gov identifier, NCT01606007) [15]. The dual add-on therapy resulted in a greater adjusted mean reduction from baseline in A1C at week 24 (–1.47%) compared with either saxagliptin (–0.88%) or dapagliflozin (–1.20%) alone added to metformin; the difference for dual add-on saxagliptin plus dapagliflozin to metformin vs. single add-on saxagliptin and single add-on dapagliflozin was –0.59% (P < 0.001) and –0.27% (P = 0.0166), respectively. The incidence of adverse events was similar across the 3 treatment groups, and hypo-glycemia was infrequent (1%), with no reports of severe hypoglycemia events (symptomatic events with glucose ≤ 54 mg/dL requiring assistance).

In this paper, we assess the attainment of diabetes quality measures among patients in this study, specifically, measures of glycemic and BP control.

Methods

Study Design and Patients

This was a post hoc analysis of a phase 3, multicenter, randomized, double-blind, active-controlled, parallel-group, 24-week study. Details of the study design, inclusion/exclusion criteria, and primary results have been previously reported [15]. In brief, men and women aged ≥ 18 years with T2D poorly controlled (A1C 8.0%–12.0%) with metformin monotherapy were randomized 1:1:1 to receive saxagliptin 5 mg/d and dapagliflozin 10 mg/d, saxagliptin 5 mg/d and placebo, or dapagliflozin 10 mg/d and placebo on a background of metformin extended release 1500 to 2000 mg/d (Figure 1). Patients were required to be on stable metformin (≥ 1500 mg/d) for ≥ 8 weeks before screening and to have a C-peptide concentration ≥ 1.0 ng/mL and a body mass index ≤ 45.0 kg/m². The trial was designed and monitored in accordance with the ethical principles of Good Clinical Practice as defined by the International Conference on Harmonisation and the Declaration of Helsinki. Institutional review boards or ethics committees at each study site approved the protocol, and all patients gave written informed consent.

Quality Measure Assessment

Individual measures assessed included the proportion of patients with A1C < 7%, A1C < 8%, A1C > 9%, and BP < 140/90 mm Hg. Composite measures assessed includedthe proportion of patients with A1C < 7% and BP < 140/90 mm Hg and the proportion of patients with A1C < 8% and BP < 140/90 mm Hg.

Antihypertensive or cholesterol-lowering medication use was not controlled for in this study. Patients were maintained on their prescribed dosing regimen for antihypertensive and cholesterol-lowering medications, with adjustments as needed per the standard of care for their diagnosis. Treatment outcomes for A1C < 7%, < 8%, or > 9% were prespecified. The BP treatment outcome was also prespecified per the statistical analysis plan; however, a change to the HEDIS quality measure treatment outcome for BP during the clinical study resulted in this analysis being no longer relevant. Therefore, analyses of the currently endorsed quality measures for BP were conducted post hoc. Quality measure assessments for A1C and BP treatment outcomes were conducted using data from the 24-week, double-blind treatment period.

Statistical Analysis

P values for the differences in proportion of patients with individual treatment outcomes and composite treatment outcomes with saxagliptin plus dapagliflozin plus metformin versus saxagliptin plus metformin or dapagliflozin plus metformin were calculated using Fisher’s exact test. The numerator and denominator for each percentage are the number of responders and the number of patients with non-missing values in the treatment group at the corresponding baseline category, respectively, and are not corrected for baseline A1C. Because some patients experienced improvement in A1C during the lead-in period and could have already been at treatment goal at baseline, a sensitivity analysis excluding these patients was completed. Results are presented for the total number of patients with non-missing values in the treatment group, as well as patients with non-missing values in the treatment group who did not meet quality measure criteria at baseline. The number needed to treat (NNT) was calculated for all comparisons reaching statistical significance.

 

Results

Patients

Patient disposition, baseline demographics, and disease characteristics have been previously published [15]. A total of 534 patients were randomized to saxagliptin plus dapagliflozin plus metformin (n = 179), saxagliptinplus metformin (n = 176), or dapagliflozin plus metformin (n = 179) and received ≥ 1 dose of study medication. Patient demographics and baseline disease characteristics were generally balanced across all 3 treatment groups (Table). Mean age across the 3 treatment groups was 54 years, and there was a generally equal distribution of men and women. The mean known duration of T2D across the 3 treatment groups was 7.6 years, and mean baseline A1C was 8.94%. At baseline, 93% to 98% of patients had A1C > 7%, 74% to 82% had A1C > 8%, and 39% to 44% had A1C > 9%. At baseline, 18% to 28% of patients had BP > 140/90 mm Hg.

Individual Quality Measures

A significantly greater proportion of patients attained A1C < 7% (good glycemic control) with the dual add-on of saxagliptin plus dapagliflozin to metformin (41.8%) compared with saxagliptin plus metformin (16.6%, P < 0.001; NNT 4, 95% confidence interval [CI], 3–6) or dapagliflozin plus metformin (23.1%, P < 0.001; NNT 5, 95% CI, 4–11; Figure 2). The data were similar when the analysis excluded patients with baseline A1C < 7% (proportions of patients: 40.8% vs 15.6% vs 21.1%; P < 0.001 for both; NNTs 4 [95% CI 3–6] and 5 [95% CI 3–10]).

The dual addition of saxagliptin plus dapagliflozin to metformin resulted in a significantly greater proportion of patients achieving A1C < 8.0% compared with saxagliptin plus metformin (71.2% vs 49.1%; P < 0.001; NNT 5 [95% CI 3–8]) or dapagliflozin plus metformin (60.1%; P = 0.033; NNT 9 [95% CI 5–85]; Figure 2). Similar results (proportions of patients: 66.4% vs 40.0% vs 51.9%; P ≤ 0.02; NNTs 4 [95% CI 3–7]) and 7 [95% CI 4–34]) were attained when the analysis excluded patients with baseline A1C < 8.0%.

Significantly fewer patients had A1C > 9% (a measure of poor glycemic control) with saxagliptin plus dapagliflozin plus metformin (12.4%) compared with saxagliptin plus metformin (22.3%; P = 0.017; NNT –10 [95% CI –50 to –6]; Figure 2). The proportion of patients with A1C > 9% was similar for both regimens that included dapagliflozin (12.4% vs 10.4%; P = 0.616).

No significant difference was observed among treatment groups in the proportion of patients with BP < 140/90 mm Hg (Figure 2). However, most patients had BP < 140/90 mm Hg (72%–82%) at baseline, which was generally maintained at week 24.

Composite Quality Measures

A significantly greater proportion of patients attained the composite of A1C < 7% and BP < 140/90 mm Hg with saxagliptin plus dapagliflozin plus metformin (33.5%) compared with saxagliptin plus metformin (13.1%; P < 0.001; NNT 5 [95% CI 4–9]) or dapagliflozin plus metformin (18.6%; P = 0.002; NNT 7 [95% CI 4–17]; Figure 3). Results were similar when patients already at these goals at baseline were excluded from the analysis (32.4% vs 12.1% vs 16.3%; P < 0.001 for both; NNTs 5 [95% CI 4–9] and 6 [95% CI 4–14]).

A significantly greater proportion of patients achieved the composite of A1C < 8% and BP < 140/90 mm Hg with saxagliptin plus dapagliflozin plus metformin compared with saxagliptin plus metformin (56.8% vs 37.1%; P < 0.001; NNT 5 [95% CI 3–11]). Although not statistically significant, a numerically greater proportion of patients achieved A1C < 8% and BP < 140/90 mmHg with saxagliptin plus dapagliflozin plus metformin compared with dapagliflozin plus metformin (56.8% vs 50.0%; P = 0.237; Figure 4). Results were similar when patients already at these goals at baseline were excluded from the analysis (55.9% vs 30.2% [P < 0.001] vs 42.6% [P = 0.025]; NNTs 4 [95% CI 3–7] and 8 [95% CI 4–55]).

Discussion

This post hoc analysis evaluated attainment of glycemic and BP quality measures for diabetes. A significantly greater proportion of patients achieved the individual quality measures of A1C < 7% and A1C < 8% with dual add-on saxagliptin plus dapagliflozin to metformin compared with single add-on saxagliptin or dapagliflozin to metformin after 24 weeks. Similar results were seen when the analysis excluded patients with A1C < 7% and < 8% at baseline. All measures of good glycemic control had clinically relevant NNTs ≤ 10 after 24 weeks with saxagliptin plus dapagliflozin plus metformin compared with saxagliptin or dapagliflozin plus metformin, regardless of baseline status. Very few patients experienced lackof improvement in glycemic control, evidenced by small proportions of patients with A1C > 9%.

 

There was little difference in BP between dual add-on saxagliptin plus dapagliflozin or single add-on saxagliptin or dapagliflozin to metformin. The proportion of patients who attained the BP quality measure of BP < 140/90 mm Hg was similar across the 3 treatments, as might be expected because most patients already met this target at baseline. However, as might be expected based on the mild diuretic effect and weight loss associated with SGLT-2 inhibitors [16,17], trends in BP favored groups treated with dapagliflozin.

Attainment of multiple treatment targets is desirable in reducing complications of diabetes. A significantly greater proportion of patients achieved both A1C < 7% and BP < 140/90 mm Hg when both saxagliptin and dapagliflozin were added to metformin compared with single-agent addition of either saxagliptin or dapagliflozin plus metformin. Similarly, a significantly greater proportion of patients achieved both A1C < 8% and BP < 140/90 mm Hg with dual addition of saxagliptin and dapagliflozin plus metformin compared with saxagliptin plus metformin. There was also a numerically greater number of patients who achieved both of these goals with triple therapy compared with dapagliflozin plus metformin, but this finding did not reach statistical significance. Clinically relevant NNT values ≤ 10 were observed for both composite outcomes for saxagliptin plus dapagliflozin plus metformin compared with saxagliptin plus metformin or dapagliflozin plus metformin after 24 weeks.

Despite advances in the medical management of T2D, a report published in 2013 showed that between 2007 and 2010, only 53% of patients achieved an A1C < 7.0% and only 19% simultaneously achieved all 3 American Diabetes Association (ADA) goals recommended for most patients at that time: A1C < 7.0%, BP < 130/80 mm Hg, and low-density lipoprotein cholesterol LDL-C < 100 mg/dL [18]. These data highlight a need for new approaches to help patients attain glycemic, BP, and cholesterol goals. Our results demonstrated that a higher proportion of patients attained glycemic and BP quality measures with dual add-on saxagliptin plus dapagliflozin compared with single add-on saxagliptin or dapagliflozin to metformin. As a result of recent updates for cholesterol management from the American College of Cardiology and the American Heart Association [19], attainment of a cholesterol level was retired as a diabetes quality measure and replaced with a recommendation for statin therapy use [20,21]. Although the current analysis did not include assessment of LDL, DPP-4 inhibitors have demonstrated neutral effects on lipids [22,23], and SGLT-2 inhibitors have demonstrated generally modest increases in LDL-C (placebo-adjusted change from baseline: 4.5%–8.0% for canagliflozin 100 and 300 mg/d, 3.9% for dapagliflozin 10 mg, and 2.3%–4.2% for empagliflozin 10 and 25 mg/d) [12,24,25], as well as increases in high-density lipoprotein cholesterol and reductions in triglycerides [26].

Current ADA guidelines recommend an individualized, stepwise approach to treatment with sequential addition of single oral antihyperglycemic agents for patients who do not achieve their glycemic goal in 3 months [27]. Although T2D may progress at different rates in different patients, T2D does generally progress over time [28], and the ADA and American Association of Clinical Endocrinologists treatment guidelines recommend initial dual add-on therapy for individuals with higher A1C, which is suggestive of more advanced disease [27,29]. For individuals requiring initial combination therapy, guidelines note that antihyperglycemic agents that have a low risk of hypoglycemia and low potential for weight gain should be preferentially selected [29]. Attainment of A1C ≤ 7%, the guideline recommendation considered appropriate for many patients, is associated with reductions in microvascular disease and, if attained soon after diagnosis of diabetes, studies have shown reductions in macrovascular disease with long-term follow-up [27,30,31]. However, it may be challenging to achieve A1C < 7% with the addition of single oral antihyperglycemic agents, especially in patients with higher A1C [32]. Less stringent A1C goals (eg, A1C < 8%) may be appropriate in individuals with a long duration of diabetes that is difficult to control, history of severe hypoglycemia, limited life expectancy, numerous comorbidities, and extensive complications or comorbidities, especially cardiovascular disease [27]. Given the shift toward individualized treatment plans with patient-specific treatment goals, it is valuable to understand how different treatment strategies effect attainment of guideline-recommended less stringent and more stringent glycemic targets that may be appropriate for certain patients.

 

In addition to quality measures that assess glucose lowering with pharmacotherapy, it is important to consider measures that assess other aspects of diabetes care. For example, quality measures related to hypoglycemia and hyperglycemia may help avoid potentially adverse glucose levels, and quality measures related to weight may provide insight on treatment and lifestyle efforts directed at weight loss and management. NQF-endorsed measures of hypoglycemia and hyperglycemia are currently moving through annual review and are paired measures, intended to be interpreted with respect to one another to ensure balanced outcomes [33,34]. This underscores the value of efficacious antihyperglycemic agents with low intrinsic potential for hypoglycemia. Although this analysis did not include quality measures related to hypoglycemia or weight, future studies evaluating these aspects of diabetes care will likely further contribute to a more comprehensive and holistic treatment approach.

In addition to assessing a broad range of quality measures, an important aspect of care to consider is patient affordability. Affordability for an individual patient will depend on access in the patient’s individual plan, the financial resources of the patient, and the potential for medical cost offsets from improved control of the patient’s disease. For example, fixed-dose combination products are associated with increased patient adherence and may increase pharmacy costs but decrease medical costs [35].

Limitations of this study include the post hoc design and that quality measure attainment was assessed over a shorter duration of time (24 weeks) than is commonly assessed in the real-world/community setting (~12 months).

Dual add-on therapy with oral antihyperglycemic agents that have complementary mechanisms of action should lead to enhanced reductions in A1C. The results reported here and from the primary study, in which saxagliptin and dapagliflozin added to metformin significantly reduced mean A1C from baseline to week 24 compared with single add-on saxagliptin or dapagliflozin [15], showed that greater reductions in A1C were attained with the coadministration of saxagliptin and dapagliflozin. The glucuretic effect of SGLT-2 inhibitors has been associated with increased plasma glucagon concentrations and increased endogenous glucose production, which may impair the full glucose-lowering potential of SGLT-2 inhibitors [36,37]. Administering saxagliptin with dapagliflozin as dual therapy was shown to blunt the rise in plasma glucagon caused by dapagliflozin [38], and this may have contributed to the greater glucose control achieved with dual add-on of these 2 antihyperglycemic drugs [15].

By targeting multiple aspects of the underlying pathophysiology in T2D, greater improvements in A1C can be achieved. Dual add-on saxagliptin plus dapagliflozin to metformin resulted in a greater proportion of patients achieving NQF-endorsed HEDIS quality measures, as well as A1C < 7% (no longer an NQF-endorsed measure). As health care shifts to a more value-based payment structure, measuring quality outcomes will assume a greater role in guiding decision making and influence the care that patients receive. Understanding how antihyperglycemic medication regimens affect quality measures can help clinicians make informed decisions.

 

Corresponding author: Lawrence Blonde, MD, Ochsner Diabetes Clinical Research Unit, Frank Riddick Diabetes Institute, Department of Endocrinology, Ochsner Medical Center, New Orleans, LA.

Funding/support: This study was supported by AstraZeneca. Medical writing support for the preparation of this manuscript was provided by Lauren D’Angelo, PhD, and Janet Matsuura, PhD, from Complete Healthcare Communications, LLC (Chadds Ford, PA), with funding from AstraZeneca.

Financial disclosures: Dr. Blonde has received grant and research support from AstraZeneca, Jansen Pharmaceuticals, Lexicon Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis and has received honoraria for participating as a speaker from AstraZeneca, Janssen Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis as well as honoraria for consultant work from AstraZeneca, GlaxoSmithKline, Intarcia Therapeutics, Janssen Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis. R. Garcia-Sanchez is an employee of AstraZeneca. J. Sheehan and Y. C. Barrett were employees of AstraZeneca at the time of this research.

From the Ochsner Diabetes Clinical Research Unit, Frank Riddick Diabetes Institute, Department of Endocrinology, Ochsner Medical Center, New Orleans, LA (Dr. Blonde), and AstraZeneca, Gaithersburg, MD (Drs. Sheehan, Barrett, and Garcia-Sanchez).

 

Abstract

• Objective: To evaluate diabetes care quality measure attainment, specifically, blood glucose and blood pressure (BP) control, with saxagliptin, a dipeptidyl peptidase-4 inhibitor, and dapagliflozin, a sodium-glucose cotransporter-2 inhibitor, added singly or as dual add-on therapy in patients with type 2 diabetes inadequately controlled with metformin alone.
• Methods: Analysis of a phase 3, randomized, double-blind, active-controlled, parallel-group trial was conducted. Patients were randomized 1:1:1 to receive saxagliptin 5 mg/d plus dapagliflozin 10 mg/d, saxagliptin 5 mg/d, or dapagliflozin 10 mg/d as add-on to metformin 1500 to 2000 mg/d. Assessments included attainment of individual and composite glycated hemoglobin (A1C) and BP measures at 24 weeks of treatment.
• Results: Compared with single add-on saxagliptin or dapagliflozin, dual add-on saxagliptin plus dapagliflozin to metformin was associated with significantly more patients attaining the individual quality measures of A1C < 7% and A1C < 8%. Similarly, dual add-on saxagliptin plus dapagliflozin was associated with significantly more patients attaining the composite quality measures A1C < 7% and BP < 140/90 mm Hg and A1C < 8% and BP < 140/90 mmHg (vs saxagliptin plus metformin).
• Conclusion: Dual add-on saxagliptin plus dapagliflozin to metformin was associated with a higher proportion of patients achieving glycemic and BP quality measures compared with single add-on saxagliptin or dapagliflozin.

Assessment of performance is a focus of many health care organizations as a means to evaluate and improve the quality of health care. Standardized performance measures have been developed to improve quality of care as well as to allow for comparative assessment of health plans and to support pay for performance models [1]. A widely used set of performance measures is the Healthcare Effectiveness Data and Information Set or HEDIS [2,3], measures that are maintained by the National Committee for Quality Assurance [4,5] and used by most US health plans [6].

Type 2 diabetes (T2D) is a focus of quality measure assessment and performance improvement because of its high prevalence, substantial personal and economic impact on society, high morbidity and mortality, and because it is a condition that requires coordinated care. Important outcome measures for diabetes include blood glucose control and blood pressure (BP) control. HEDIS measures for T2D include a glycated hemoglobin (A1C) > 9%, indicating poor glucose control, < 8%, indicating good control, and < 7%, a more stringent measure of good glycemic control. The HEDIS measure for BP in T2D is < 140/90 mm Hg, which is considered good BP control. All of these HEDIS measures are currently or were previously (A1C < 7%) endorsed by the National Quality Forum [1,7–10]. Endorsement of a quality measure by the NQF indicates that the measure has been thoroughly evaluated, meets specific criteria, and is based on recognized standards of care grounded in evidence-based medicine [1].

A number of oral agents are utilized in the treatment of diabetes. Saxagliptin, an oral dipeptidyl peptidase-4 (DPP-4) inhibitor, and dapagliflozin, an oral sodium-glucose cotransporter-2 (SGLT-2) inhibitor, are indicated as adjuncts to diet and exercise in adults with T2D [11,12]. Saxagliptin inhibits DPP-4, and thereby reduces fasting and postprandial glucose concentrations by preventing degradation of the incretin hormones, glucagon-like peptide-1 and glucose-dependent insulinotropic polypeptide [13]. Dapagliflozin reduces blood glucose concentrations by inhibiting glucose reabsorption in the proximal tubule of the kidney, which results in enhanced urinary glucose excretion [14]. Because their mechanisms of action are glucose-dependent, both saxagliptin and dapagliflozin have a low intrinsic potential to cause hypoglycemia [13,14]. In a randomized, double-blind study of patients with T2D inadequately controlled with metformin, Rosenstock et al assessed the efficacy and safety of dual add-on of saxagliptin plus dapagliflozin versus saxagliptin and dapagliflozin added on alone (ClinicalTrials.gov identifier, NCT01606007) [15]. The dual add-on therapy resulted in a greater adjusted mean reduction from baseline in A1C at week 24 (–1.47%) compared with either saxagliptin (–0.88%) or dapagliflozin (–1.20%) alone added to metformin; the difference for dual add-on saxagliptin plus dapagliflozin to metformin vs. single add-on saxagliptin and single add-on dapagliflozin was –0.59% (P < 0.001) and –0.27% (P = 0.0166), respectively. The incidence of adverse events was similar across the 3 treatment groups, and hypo-glycemia was infrequent (1%), with no reports of severe hypoglycemia events (symptomatic events with glucose ≤ 54 mg/dL requiring assistance).

In this paper, we assess the attainment of diabetes quality measures among patients in this study, specifically, measures of glycemic and BP control.

Methods

Study Design and Patients

This was a post hoc analysis of a phase 3, multicenter, randomized, double-blind, active-controlled, parallel-group, 24-week study. Details of the study design, inclusion/exclusion criteria, and primary results have been previously reported [15]. In brief, men and women aged ≥ 18 years with T2D poorly controlled (A1C 8.0%–12.0%) with metformin monotherapy were randomized 1:1:1 to receive saxagliptin 5 mg/d and dapagliflozin 10 mg/d, saxagliptin 5 mg/d and placebo, or dapagliflozin 10 mg/d and placebo on a background of metformin extended release 1500 to 2000 mg/d (Figure 1). Patients were required to be on stable metformin (≥ 1500 mg/d) for ≥ 8 weeks before screening and to have a C-peptide concentration ≥ 1.0 ng/mL and a body mass index ≤ 45.0 kg/m². The trial was designed and monitored in accordance with the ethical principles of Good Clinical Practice as defined by the International Conference on Harmonisation and the Declaration of Helsinki. Institutional review boards or ethics committees at each study site approved the protocol, and all patients gave written informed consent.

Quality Measure Assessment

Individual measures assessed included the proportion of patients with A1C < 7%, A1C < 8%, A1C > 9%, and BP < 140/90 mm Hg. Composite measures assessed includedthe proportion of patients with A1C < 7% and BP < 140/90 mm Hg and the proportion of patients with A1C < 8% and BP < 140/90 mm Hg.

Antihypertensive or cholesterol-lowering medication use was not controlled for in this study. Patients were maintained on their prescribed dosing regimen for antihypertensive and cholesterol-lowering medications, with adjustments as needed per the standard of care for their diagnosis. Treatment outcomes for A1C < 7%, < 8%, or > 9% were prespecified. The BP treatment outcome was also prespecified per the statistical analysis plan; however, a change to the HEDIS quality measure treatment outcome for BP during the clinical study resulted in this analysis being no longer relevant. Therefore, analyses of the currently endorsed quality measures for BP were conducted post hoc. Quality measure assessments for A1C and BP treatment outcomes were conducted using data from the 24-week, double-blind treatment period.

Statistical Analysis

P values for the differences in proportion of patients with individual treatment outcomes and composite treatment outcomes with saxagliptin plus dapagliflozin plus metformin versus saxagliptin plus metformin or dapagliflozin plus metformin were calculated using Fisher’s exact test. The numerator and denominator for each percentage are the number of responders and the number of patients with non-missing values in the treatment group at the corresponding baseline category, respectively, and are not corrected for baseline A1C. Because some patients experienced improvement in A1C during the lead-in period and could have already been at treatment goal at baseline, a sensitivity analysis excluding these patients was completed. Results are presented for the total number of patients with non-missing values in the treatment group, as well as patients with non-missing values in the treatment group who did not meet quality measure criteria at baseline. The number needed to treat (NNT) was calculated for all comparisons reaching statistical significance.

 

Results

Patients

Patient disposition, baseline demographics, and disease characteristics have been previously published [15]. A total of 534 patients were randomized to saxagliptin plus dapagliflozin plus metformin (n = 179), saxagliptinplus metformin (n = 176), or dapagliflozin plus metformin (n = 179) and received ≥ 1 dose of study medication. Patient demographics and baseline disease characteristics were generally balanced across all 3 treatment groups (Table). Mean age across the 3 treatment groups was 54 years, and there was a generally equal distribution of men and women. The mean known duration of T2D across the 3 treatment groups was 7.6 years, and mean baseline A1C was 8.94%. At baseline, 93% to 98% of patients had A1C > 7%, 74% to 82% had A1C > 8%, and 39% to 44% had A1C > 9%. At baseline, 18% to 28% of patients had BP > 140/90 mm Hg.

Individual Quality Measures

A significantly greater proportion of patients attained A1C < 7% (good glycemic control) with the dual add-on of saxagliptin plus dapagliflozin to metformin (41.8%) compared with saxagliptin plus metformin (16.6%, P < 0.001; NNT 4, 95% confidence interval [CI], 3–6) or dapagliflozin plus metformin (23.1%, P < 0.001; NNT 5, 95% CI, 4–11; Figure 2). The data were similar when the analysis excluded patients with baseline A1C < 7% (proportions of patients: 40.8% vs 15.6% vs 21.1%; P < 0.001 for both; NNTs 4 [95% CI 3–6] and 5 [95% CI 3–10]).

The dual addition of saxagliptin plus dapagliflozin to metformin resulted in a significantly greater proportion of patients achieving A1C < 8.0% compared with saxagliptin plus metformin (71.2% vs 49.1%; P < 0.001; NNT 5 [95% CI 3–8]) or dapagliflozin plus metformin (60.1%; P = 0.033; NNT 9 [95% CI 5–85]; Figure 2). Similar results (proportions of patients: 66.4% vs 40.0% vs 51.9%; P ≤ 0.02; NNTs 4 [95% CI 3–7]) and 7 [95% CI 4–34]) were attained when the analysis excluded patients with baseline A1C < 8.0%.

Significantly fewer patients had A1C > 9% (a measure of poor glycemic control) with saxagliptin plus dapagliflozin plus metformin (12.4%) compared with saxagliptin plus metformin (22.3%; P = 0.017; NNT –10 [95% CI –50 to –6]; Figure 2). The proportion of patients with A1C > 9% was similar for both regimens that included dapagliflozin (12.4% vs 10.4%; P = 0.616).

No significant difference was observed among treatment groups in the proportion of patients with BP < 140/90 mm Hg (Figure 2). However, most patients had BP < 140/90 mm Hg (72%–82%) at baseline, which was generally maintained at week 24.

Composite Quality Measures

A significantly greater proportion of patients attained the composite of A1C < 7% and BP < 140/90 mm Hg with saxagliptin plus dapagliflozin plus metformin (33.5%) compared with saxagliptin plus metformin (13.1%; P < 0.001; NNT 5 [95% CI 4–9]) or dapagliflozin plus metformin (18.6%; P = 0.002; NNT 7 [95% CI 4–17]; Figure 3). Results were similar when patients already at these goals at baseline were excluded from the analysis (32.4% vs 12.1% vs 16.3%; P < 0.001 for both; NNTs 5 [95% CI 4–9] and 6 [95% CI 4–14]).

A significantly greater proportion of patients achieved the composite of A1C < 8% and BP < 140/90 mm Hg with saxagliptin plus dapagliflozin plus metformin compared with saxagliptin plus metformin (56.8% vs 37.1%; P < 0.001; NNT 5 [95% CI 3–11]). Although not statistically significant, a numerically greater proportion of patients achieved A1C < 8% and BP < 140/90 mmHg with saxagliptin plus dapagliflozin plus metformin compared with dapagliflozin plus metformin (56.8% vs 50.0%; P = 0.237; Figure 4). Results were similar when patients already at these goals at baseline were excluded from the analysis (55.9% vs 30.2% [P < 0.001] vs 42.6% [P = 0.025]; NNTs 4 [95% CI 3–7] and 8 [95% CI 4–55]).

Discussion

This post hoc analysis evaluated attainment of glycemic and BP quality measures for diabetes. A significantly greater proportion of patients achieved the individual quality measures of A1C < 7% and A1C < 8% with dual add-on saxagliptin plus dapagliflozin to metformin compared with single add-on saxagliptin or dapagliflozin to metformin after 24 weeks. Similar results were seen when the analysis excluded patients with A1C < 7% and < 8% at baseline. All measures of good glycemic control had clinically relevant NNTs ≤ 10 after 24 weeks with saxagliptin plus dapagliflozin plus metformin compared with saxagliptin or dapagliflozin plus metformin, regardless of baseline status. Very few patients experienced lackof improvement in glycemic control, evidenced by small proportions of patients with A1C > 9%.

 

There was little difference in BP between dual add-on saxagliptin plus dapagliflozin or single add-on saxagliptin or dapagliflozin to metformin. The proportion of patients who attained the BP quality measure of BP < 140/90 mm Hg was similar across the 3 treatments, as might be expected because most patients already met this target at baseline. However, as might be expected based on the mild diuretic effect and weight loss associated with SGLT-2 inhibitors [16,17], trends in BP favored groups treated with dapagliflozin.

Attainment of multiple treatment targets is desirable in reducing complications of diabetes. A significantly greater proportion of patients achieved both A1C < 7% and BP < 140/90 mm Hg when both saxagliptin and dapagliflozin were added to metformin compared with single-agent addition of either saxagliptin or dapagliflozin plus metformin. Similarly, a significantly greater proportion of patients achieved both A1C < 8% and BP < 140/90 mm Hg with dual addition of saxagliptin and dapagliflozin plus metformin compared with saxagliptin plus metformin. There was also a numerically greater number of patients who achieved both of these goals with triple therapy compared with dapagliflozin plus metformin, but this finding did not reach statistical significance. Clinically relevant NNT values ≤ 10 were observed for both composite outcomes for saxagliptin plus dapagliflozin plus metformin compared with saxagliptin plus metformin or dapagliflozin plus metformin after 24 weeks.

Despite advances in the medical management of T2D, a report published in 2013 showed that between 2007 and 2010, only 53% of patients achieved an A1C < 7.0% and only 19% simultaneously achieved all 3 American Diabetes Association (ADA) goals recommended for most patients at that time: A1C < 7.0%, BP < 130/80 mm Hg, and low-density lipoprotein cholesterol LDL-C < 100 mg/dL [18]. These data highlight a need for new approaches to help patients attain glycemic, BP, and cholesterol goals. Our results demonstrated that a higher proportion of patients attained glycemic and BP quality measures with dual add-on saxagliptin plus dapagliflozin compared with single add-on saxagliptin or dapagliflozin to metformin. As a result of recent updates for cholesterol management from the American College of Cardiology and the American Heart Association [19], attainment of a cholesterol level was retired as a diabetes quality measure and replaced with a recommendation for statin therapy use [20,21]. Although the current analysis did not include assessment of LDL, DPP-4 inhibitors have demonstrated neutral effects on lipids [22,23], and SGLT-2 inhibitors have demonstrated generally modest increases in LDL-C (placebo-adjusted change from baseline: 4.5%–8.0% for canagliflozin 100 and 300 mg/d, 3.9% for dapagliflozin 10 mg, and 2.3%–4.2% for empagliflozin 10 and 25 mg/d) [12,24,25], as well as increases in high-density lipoprotein cholesterol and reductions in triglycerides [26].

Current ADA guidelines recommend an individualized, stepwise approach to treatment with sequential addition of single oral antihyperglycemic agents for patients who do not achieve their glycemic goal in 3 months [27]. Although T2D may progress at different rates in different patients, T2D does generally progress over time [28], and the ADA and American Association of Clinical Endocrinologists treatment guidelines recommend initial dual add-on therapy for individuals with higher A1C, which is suggestive of more advanced disease [27,29]. For individuals requiring initial combination therapy, guidelines note that antihyperglycemic agents that have a low risk of hypoglycemia and low potential for weight gain should be preferentially selected [29]. Attainment of A1C ≤ 7%, the guideline recommendation considered appropriate for many patients, is associated with reductions in microvascular disease and, if attained soon after diagnosis of diabetes, studies have shown reductions in macrovascular disease with long-term follow-up [27,30,31]. However, it may be challenging to achieve A1C < 7% with the addition of single oral antihyperglycemic agents, especially in patients with higher A1C [32]. Less stringent A1C goals (eg, A1C < 8%) may be appropriate in individuals with a long duration of diabetes that is difficult to control, history of severe hypoglycemia, limited life expectancy, numerous comorbidities, and extensive complications or comorbidities, especially cardiovascular disease [27]. Given the shift toward individualized treatment plans with patient-specific treatment goals, it is valuable to understand how different treatment strategies effect attainment of guideline-recommended less stringent and more stringent glycemic targets that may be appropriate for certain patients.

 

In addition to quality measures that assess glucose lowering with pharmacotherapy, it is important to consider measures that assess other aspects of diabetes care. For example, quality measures related to hypoglycemia and hyperglycemia may help avoid potentially adverse glucose levels, and quality measures related to weight may provide insight on treatment and lifestyle efforts directed at weight loss and management. NQF-endorsed measures of hypoglycemia and hyperglycemia are currently moving through annual review and are paired measures, intended to be interpreted with respect to one another to ensure balanced outcomes [33,34]. This underscores the value of efficacious antihyperglycemic agents with low intrinsic potential for hypoglycemia. Although this analysis did not include quality measures related to hypoglycemia or weight, future studies evaluating these aspects of diabetes care will likely further contribute to a more comprehensive and holistic treatment approach.

In addition to assessing a broad range of quality measures, an important aspect of care to consider is patient affordability. Affordability for an individual patient will depend on access in the patient’s individual plan, the financial resources of the patient, and the potential for medical cost offsets from improved control of the patient’s disease. For example, fixed-dose combination products are associated with increased patient adherence and may increase pharmacy costs but decrease medical costs [35].

Limitations of this study include the post hoc design and that quality measure attainment was assessed over a shorter duration of time (24 weeks) than is commonly assessed in the real-world/community setting (~12 months).

Dual add-on therapy with oral antihyperglycemic agents that have complementary mechanisms of action should lead to enhanced reductions in A1C. The results reported here and from the primary study, in which saxagliptin and dapagliflozin added to metformin significantly reduced mean A1C from baseline to week 24 compared with single add-on saxagliptin or dapagliflozin [15], showed that greater reductions in A1C were attained with the coadministration of saxagliptin and dapagliflozin. The glucuretic effect of SGLT-2 inhibitors has been associated with increased plasma glucagon concentrations and increased endogenous glucose production, which may impair the full glucose-lowering potential of SGLT-2 inhibitors [36,37]. Administering saxagliptin with dapagliflozin as dual therapy was shown to blunt the rise in plasma glucagon caused by dapagliflozin [38], and this may have contributed to the greater glucose control achieved with dual add-on of these 2 antihyperglycemic drugs [15].

By targeting multiple aspects of the underlying pathophysiology in T2D, greater improvements in A1C can be achieved. Dual add-on saxagliptin plus dapagliflozin to metformin resulted in a greater proportion of patients achieving NQF-endorsed HEDIS quality measures, as well as A1C < 7% (no longer an NQF-endorsed measure). As health care shifts to a more value-based payment structure, measuring quality outcomes will assume a greater role in guiding decision making and influence the care that patients receive. Understanding how antihyperglycemic medication regimens affect quality measures can help clinicians make informed decisions.

 

Corresponding author: Lawrence Blonde, MD, Ochsner Diabetes Clinical Research Unit, Frank Riddick Diabetes Institute, Department of Endocrinology, Ochsner Medical Center, New Orleans, LA.

Funding/support: This study was supported by AstraZeneca. Medical writing support for the preparation of this manuscript was provided by Lauren D’Angelo, PhD, and Janet Matsuura, PhD, from Complete Healthcare Communications, LLC (Chadds Ford, PA), with funding from AstraZeneca.

Financial disclosures: Dr. Blonde has received grant and research support from AstraZeneca, Jansen Pharmaceuticals, Lexicon Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis and has received honoraria for participating as a speaker from AstraZeneca, Janssen Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis as well as honoraria for consultant work from AstraZeneca, GlaxoSmithKline, Intarcia Therapeutics, Janssen Pharmaceuticals, Merck, Novo Nordisk, and Sanofi-Aventis. R. Garcia-Sanchez is an employee of AstraZeneca. J. Sheehan and Y. C. Barrett were employees of AstraZeneca at the time of this research.

Data from the Centers for Disease Control and Prevention indicate that almost 24 million Americans, or 7.8% of the population, have diabetes; 90% to 95% of these have type 2 diabetes mellitus (T2DM).¹ Diabetes and excessive weight often coexist. An analysis of data from the 1999–2002 National Health and Nutrition Examination Survey (NHANES) showed that among individuals with diabetes, 85% were overweight or obese and 55% were obese.²

Gaps remain in the management of T2DM between the goals for clinical parameters of care (eg, control of glucose, blood pressure [BP], and lipids) and actual clinical practice.³ NHANES data reveal that glycemic control improved from a mean glycosylated hemoglobin A1c (HbA1c) of 7.82% in 1999–2000 to 7.18% in 2003–2004.⁴ Hazard models based on the United Kingdom Prospective Diabetes Study (UKPDS) 10-year outcomes data in 4,320 newly diagnosed T2DM patients suggest that a sustained decrease in HbA1c of 0.511 percentage points could reduce diabetes complications by 10.7%.^4,5

Additional analysis of NHANES data showed that in 2003–2004, about 57% of individuals achieved glycemic control, 48% reached BP targets, and 50% achieved target cholesterol goals.Only about 13% of diabetes patients achieved their target goals for all three parameters concurrently.⁶

This article reviews the association between cardiometabolic risk and the current antihyperglycemic treatments for patients with T2DM, with a focus on the role of incretin-related therapies.

THE IMPORTANCE OF CARDIOMETABOLIC RISK IN T2DM

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among people with diabetes and is the reported cause of mortality in up to 65% of deaths in persons with diabetes in the United States.⁷ The risk of CVD is two- to fourfold greater among adults with diabetes than among adults who do not have diabetes.⁸ The risk of CVD in patients with T2DM was evident in the UKPDS 17, where macrovascular complications, including CVD, were about twice as common as microvascular complications (20% vs 9%) after 9 years of follow-up.⁹ A study that involved more than 44,000 patients showed an almost double rate of mortality from all causes among individuals with T2DM compared with those with no diabetes (hazard ratio, 1.93; 95% confidence interval, 1.89 to 1.97).¹⁰ Current guidelines recommend aggressive management of CV risk factors, including BP control, correction of atherogenic dyslipidemia, glycemic control, weight reduction for those who are overweight or obese, and smoking cessation for those who smoke.^3,11 Lifestyle interventions, including weight reduction and appropriately prescribed physical activity, result in reduced CV risk factors, which can help slow the progression of T2DM.¹²

GOALS OF T2DM THERAPY

Several studies have demonstrated that glycemic control can delay or prevent the development and progression of microvascular complications.^13,14 UKPDS 33 showed that more intensive blood glucose control (median HbA1c 7.0%) in patients with T2DM followed over 10 years significantly (P = .029) reduced the risk for any diabetes-related end point by 12% compared with conventional therapy (median HbA1c 7.9%). Most of the risk reduction was accounted for by a 25% risk reduction in microvascular end points (P = .0099).¹³ Another report (UKPDS 35) demonstrated that HbA1c was strongly related to microvascular effects, with a 1% reduction in HbA1c associated with a 37% reduction in microvascular complications.¹⁴

Does intensive glucose control reduce CV risk?

To resolve the ongoing question of whether intensive glucose control can lead to a reduction in CV risk in patients with T2DM, three large, long-term trials were conducted within the last decade.^15–18 Two of these, the Action to Control Cardiovascular Risk in Diabetes (ACCORD) and Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) trials, each enrolled more than 10,000 previously treated patients with long-standing T2DM. Patients were randomized to standard or intensive glycemic control for 3.5 years in the ACCORD trial and for 5 years in the ADVANCE trial.^15,16

The ACCORD and ADVANCE trials, along with the smaller Veterans Administration Diabetes Trial (VADT) (N = 1,791), failed to show that more intensive glycemic control significantly reduced CVD.^15–17 Additionally, the glycemic control component of ACCORD was halted because of increased mortality in the intensive arm compared with the standard arm.¹⁵ Further analyses of ACCORD data presented at the 69th Scientific Sessions of the American Diabetes Association (ADA) showed that HbA1c values lower than 7.0% did not explain the increased mortality. The 20% higher risk of death for every 1.0% increase in HbA1c greater than 6.0% suggests that glucose concentrations even lower than the general HbA1c goal of less than 7.0% may be appropriate in some patients.¹⁸ The most recent finding from VADT was that CV risk was dependent on disease duration and presence of comorbidities. Intensive therapy seemed to work best in patients with diabetes of less than 15 years’ duration, while risk of a CV event was more than doubled with intensive therapy in patients having diabetes for more than 21 years.

Clarification of treatment goals

A position statement of the ADA and a scientific statement of the American College of Cardiology Foundation and the American Heart Association¹⁹ concluded that the “evidence obtained from ACCORD, ADVANCE, and VADT does not suggest the need for major changes in glycemic control targets but, rather, additional clarification of the language that has consistently stressed individualization.” They state that while the general HbA1c goal of less than 7.0% seems reasonable, even lower HbA1c goals may be appropriate for some patients if they can be achieved without significant hypoglycemia or other adverse effects. Such patients might include those with diabetes of short duration, long life expectancy, or no significant CVD or hypoglycemia. Conversely, higher HbA1c goals may be appropriate for patients with limited life expectancy, a history of severe hypoglycemia, established microvascular or macrovascular complications, significant other comorbid conditions, or longstanding diabetes in whom an HbA1c of less than 7.0% has been difficult to attain despite optimal treatment and diabetes self-management education.¹⁹

 

 

Long-term risk reduction

A 10-year, postinterventional follow-up study (UKPDS 80) of the UKPDS survivor cohort was reported recently.²⁰ Results showed that despite an early loss of glycemic differences between patients treated with diet and those treated with intensive regimens (sulfonylurea or insulin; metformin in overweight patients), the pharmacotherapy group demonstrated a prolonged reduction in microvascular risk as well as a significant reduction in the risk for myocardial infarction (15% [P = .01] in the sulfonylurea-insulin group and 33% [P = .005] in the metformin group) and death from any cause.²⁰ This suggests that early improvement in glycemic control is associated with long-term benefits in the micro- and macrovascular health of patients with T2DM.

Additionally, the recent long-term follow-up of the Steno-2 study²¹ showed that a multifactorial intervention striving for intensive glucose, BP, and lipid control that included the use of renin-angiotensin system blockers, aspirin, and lipid-lowering agents not only reduced the risk of nonfatal CVD among patients with T2DM and microalbuminuria, but also had sustained beneficial effects on vascular complications and on rates of death from any cause and from CV causes. From a health care payer perspective, intensive multifactorial intervention was more likely to be cost-effective than conventional treatment in Denmark, especially if applied in a primary care setting.²²

Comprehensive care needed

The lower-than-expected rates of CV outcomes in the ACCORD, ADVANCE, VADT, and Steno-2 studies reinforce the importance of comprehensive diabetes care that treats not only hyperglycemia but also elevated BP and dyslipidemia; these are considered the “ABCs” of diabetes.^11,19 The 2009 ADA standards of medical care guidelines recommend that for most T2DM patients, HbA1c should be maintained at less than 7.0%,³ while the American Association of Clinical Endocrinologists (AACE) 2007 guidelines state that HbA1c should be 6.5% or less.¹¹ Both organizations stress the importance of individualized goals, as discussed above, and advocate BP goals of less than 130/80 mm Hg and dyslipidemia goals of low-density lipoprotein cholesterol (LDL-C) less than 100 mg/dL, high-density lipoprotein cholesterol (HDL-C) greater than 40 mg/dL for men and 50 mg/dL for women, and triglycerides less than 150 mg/dL. It is recommended that an optional LDL-C goal of less than 70 mg/dL be considered for individuals with overt CVD.

CURRENT ANTIHYPERGLYCEMIC TREATMENT STRATEGIES

In response to new insights from clinical research and emerging treatment strategies, disease-specific organizations and medical specialty societies regularly revise and update their treatment guidelines and algorithms. These resources recommend that glycemic progress should be regularly monitored and pharmacologic therapy titrated or new drugs added promptly if glycemic goals are not met after 2 to 3 months.

Several algorithms combine scientific evidence with expert clinical opinion to guide physicians in treating their patients with T2DM. The American College of Endocrinology (ACE)/AACE road maps are designed to help develop individualized treatment regimens to achieve an HbA1c of 6.5% or less.²³ The algorithm from a writing group assembled by the ADA and the European Association for the Study of Diabetes (EASD) similarly promotes pharmacologic treatment together with lifestyle modifications to maintain a glycemic goal of HbA1c less than 7.0%.²⁴

OVERVIEW OF ANTIHYPERGLYCEMIC TREATMENT APPROACHES

Lifestyle measures, medical nutrition therapy, and appropriately prescribed physical activity are recommended for virtually all patients with T2DM, as well as weight loss for those who are overweight or obese. Unfortunately, many patients cannot achieve glycemic goals with lifestyle measures alone and require the addition of pharmacotherapy.³ Extensive development of new therapies during the past 15 years has resulted in more than 11 classes of approved antihyperglycemic medications (Table 1) with diverse mechanisms of action and varied effects on HbA1c, body weight, lipids, and other factors.^24–26

Initial oral therapy

T2DM is usually treated initially with a single oral agent. Consistent with the progressive nature of the disease, patients often eventually require one or more additional oral agents and in many cases insulin.^13,27 Choice of specific agents is based on individual patient circumstances, including the need for weight loss and control of fasting versus postprandial glucose, the presence of dyslipidemia and hypertension, and the risk for and potential consequences of hypoglycemia.²⁴ T2DM patients with severely uncontrolled and symptomatic hyperglycemia are best treated, at least initially, with a combination of insulin therapy and lifestyle intervention, often with metformin.

Metformin. The recently revised ADA/EASD writing group algorithm recommends that patients not requiring initial insulin begin treatment with metformin at the time of diagnosis unless there are contraindications.²⁴ Metformin is not associated with hypoglycemia and is considered weight-neutral, although some patients may lose weight.²⁸

Sulfonylureas. Sulfonylureas stimulate insulin secretion from pancreatic beta cells; their use may be associated with hypoglycemia and weight gain. Mechanisms for weight gain with sulfonylureas include reduction of glucosuria and increased caloric intake to prevent or treat hypoglycemia.^11,28 Nateglinide and repaglinide are nonsulfonylurea oral insulin secretagogues. They result in rapid and relatively short-lived insulin responses and are usually administered three times a day, before each meal. Their use may be associated with weight gain and hypoglycemia.¹¹

Thiazolidinediones. Thiazolidinediones (TZD) increase insulin sensitivity in muscle, adipose tissue, and the liver. Hypoglycemia is uncommon with TZD monotherapy but weight gain related to increased and redistributed adiposity and fluid retention frequently occurs.

Alpha-glucosidase inhibitors. The alpha-glucosidase inhibitors are administered before meals and primarily reduce postprandial hyperglycemia. They are generally weight-neutral.²⁸

Insulin. Insulin and insulin analogues are the most effective antihyperglycemic agents, but their use can be associated with hypoglycemia and clinically significant weight gain.²⁸

Colesevelam. Colesevelam is a bile acid sequestrant that was recently approved by the US Food and Drug Administration as an antihyperglycemic therapy in people with T2DM. At a dosage of 1.875 g BID or 3.75 g QD in combination with a sulfonylurea, metformin, or insulin therapy, reductions in HbA1c compared with placebo in clinical trials of colesevelam have ranged from ­–0.5% to –0.7% (P < .02). Frequency of hypoglycemia and weight gain is low with this agent.²⁶

Weight management. Weight reduction is important for overweight or obese patients with T2DM.^27,28 Even moderate weight loss (5% of body weight) can be associated with improved insulin action and reduced hyperglycemia.²⁹ Conversely, weight gain has been shown to worsen hyperglycemia and other CV risk factors. Treatment-related weight gain can also lead to decreased regimen adherence, contributing to poor glycemic control.²⁸

 

 

THE ROLE OF INCRETIN HORMONES AND INCRETIN-BASED THERAPIES IN T2DM PATIENTS

Over the last few years, the role of incretin hormones and their contribution to diabetes pathophysiology has become more apparent. The incretin effect refers to the observation that orally administered glucose elicits a greater insulin response than does glucose administered intravenously to produce equivalent blood glucose concentrations.^30,31 The incretin effect is diminished in patients with T2DM.

Hormone mediation of the incretin effect

The two hormones that mediate the incretin effect are GIP (also known as gastric inhibitory polypeptide or glucose-dependent insulinotropic polypeptide) and glucagon-like peptide−1 (GLP-1).^30,31 GLP-1 has several glucoregulatory actions, including enhancement of endogenous insulin release and suppression of inappropriate glucagon secretion, both in a glucose-dependent manner. Therefore, these effects of GLP-1 occur only when glucose concentrations are elevated, thereby minimizing the risk of hypoglycemia. GLP-1 also regulates gastric emptying; infusions of GLP-1 can slow the accelerated emptying that is often present in T2DM patients. GLP-1 also increases satiety and decreases food intake via a central mechanism.³¹

Because GLP-1 is rapidly inactivated by the enzyme dipeptidyl peptidase–4 (DPP-4), therapeutic use of GLP-1 would require continuous infusion, which is impractical.^30,31 Two strategies have been used to produce incretin-related therapies. One, inhibition of the DPP-4 enzyme, results in a two- to threefold enhancement of endogenous GLP-1. The other, involving agents that resist breakdown by DPP-4 but bind to and activate the GLP-1 receptor, produces glucoregulatory effects similar to those of GLP-1.³⁰

Following subcutaneous (SC) injection, GLP-1 receptor agonists enhance insulin secretion and suppress inappropriately elevated glucagon, both in a glucose-dependent manner, as well as slow gastric emptying and enhance satiety.³⁰ DPP-4 inhibitors provide glucose-dependent enhanced insulin secretion and glucagon suppression, but they do not have the same effects on gastric emptying or satiety.

Clinically, the GLP-1 receptor agonists improve glycemia and are associated with weight loss.^32–35 Adverse gastrointestinal symptoms are relatively common during the first few weeks of treatment. DPP-4 inhibitors improve glycemia but are weight-neutral and are not generally associated with significant gastrointestinal symptoms.^32,36–38

Incretin-based therapies

Incretin-based therapies are currently part of the antihyperglycemic armamentarium.^25,32 The AACE guidelines¹¹ and the ACE/AACE roadmaps²³ include the GLP-1 receptor agonist exenatide and the DPP-4 inhibitor sitagliptin among antihyperglycemic therapies for patients with T2DM. The most recent update of the consensus algorithm statement of a joint ADA/EASD writing group included GLP-1 receptor agonists (but not DPP-4 inhibitors) in tier 2 of preferred agents, especially for patients who have concerns related to weight and hypoglycemia.²⁴ They noted that DPP-4 inhibitors may be appropriate choices in selected patients.

DPP-4 inhibitors: sitagliptin, saxagliptin. Until recently, sitagliptin was the only DPP-4 inhibitor available in the United States. Sitagliptin is approved by the FDA for treatment of T2DM at a recommended oral dosage of 100 mg QD, either as monotherapy or in combination with other oral antihyperglycemic medications. The dosage of sitagliptin should be reduced to 50 mg/day in patients with creatinine clearance (CrCl) levels that are between 30 mL/min and 50 mL/min and to 25 mg/day in those with CrCl less than 30 mL/min.³⁹

In a meta-analysis of incretin-based therapies, DPP-4 inhibitors produced a reduction in HbA1c compared with placebo (weighted mean difference of –0.74%; 95% confidence interval, –0.85% to –0.62%).³² DPP-4 inhibitor antihyperglycemic efficacy has been shown to be similar whether used as a monotherapy or add-on therapy.^32,37,38 This same meta-analysis showed DPP-4 inhibitors as having a neutral effect on weight.³² More recently, a single-pill combination of metformin and sitagliptin was approved.⁴⁰

A study comparing metformin, sitagliptin, and the combination of the two as initial monotherapy in T2DM patients with a baseline HbA1c of 8.8% showed 24-week HbA1c reductions from baseline of –0.66% with sitagliptin 100 mg QD, –0.82% with metformin 500 mg BID, and –1.90% with sitagliptin 50 mg + metformin 1,000 mg BID.⁴¹

On July 31, 2009, the FDA approved another DPP-4 inhibitor, saxagliptin, for the treatment of T2DM either as monotherapy or in combination with metformin, a sulfonylurea, or a TZD.⁴²

GLP-1 receptor agonist: exenatide. Exenatide, the only FDA-approved GLP-1 receptor agonist, is the synthetic version of exendin-4, which binds to the human GLP-1 receptor and in vitro possesses many of the glucoregulatory effects of endogenous GLP-1.^30,32 Exenatide is indicated as monotherapy or adjunctive therapy for patients with T2DM who have not achieved adequate glycemic control with metformin, a sulfonylurea, a TZD, or metformin in combination with a sulfonylurea or a TZD.⁴³ Exenatide is administered by SC injection BID at a starting dosage of 5 mg BID for 4 weeks, followed by an increase to 10 mg BID.

Exenatide has been shown not only to enhance glucose-dependent insulin secretion but also to restore impaired first-phase insulin response in subjects with T2DM. Exenatide also helps control postprandial glycemic excursions by suppressing inappropriate glucagon secretion, slowing accelerated gastric emptying, and enhancing satiety. The increased satiety results in decreased food intake and weight loss.^31,44 In a recent head-to-head crossover study, exenatide was shown to be more effective than sitagliptin in lowering postprandial glucose concentrations, increasing insulin secretion, and reducing postprandial glucagon secretion.⁴⁵ Exenatide also slowed gastric emptying and reduced caloric intake.

Exenatide, in most studies, resulted in a placebo-subtracted HbA1c reduction of approximately –1.0% and in one study lowered HbA1c from baseline by –1.5%. Completer analyses have shown HbA1c reductions of –1.0% up to 3 years and –0.8% up to 3.5 years. Exenatide has also been associated with a mean weight loss of as much as –3.6 kg at 30 weeks and as much as –5.3 kg at 3.5 years.^{33–35,46,47} A 1-year study showed that exenatide improved beta-cell secretory function compared with insulin glargine in metformin-treated patients with T2DM.⁴⁸ Long-term data, including findings from completed and intention-to-treat analyses of 82 weeks⁴⁹ to at least 3 years⁴⁷ have demonstrated that exenatide improved CV risk factors, including those related to BP, lipids, and hepatic injury biomarkers.

Therapies in development

Incretin-based therapies in development include a novel once-weekly formulation of exenatide; taspoglutide, another once-weekly GLP-1 receptor agonist; and liraglutide, a GLP-1 receptor agonist that is administered once daily.⁵⁰ Liraglutide is currently being evaluated in clinical trials as a once-daily SC injection.^51–53 Liraglutide has been reported to reduce HbA1c by –1.1% at 26 weeks and up to –1.14% at 52 weeks and result in weight loss (up to –2.8 kg at 26 weeks and up to –2.5 kg at 52 weeks) in patients with T2DM who are treatment-naïve or taking other antidiabetes agents, including metformin, sulfonylurea, and TZD.^51–53 Evaluation of the once-weekly formulation of exenatide showed reductions in HbA1c of –1.9% at 30 weeks and –2.0% at 52 weeks with a weight loss of –3.7 kg at 30 weeks and –4.1 kg over 52 weeks of treatment.^46,54

CONCLUSION

In the United States, the epidemics of excessive weight and T2DM have contributed to an increased medical risk for many individuals. Comprehensive diabetes treatments targeting not only hyperglycemia but also frequently associated overweight/obesity, hypertension, and dyslipidemia will be required to reduce such risk. Current treatment strategies have evolved based on updated clinical guidelines and trials, as well as practice experience, including those related to newer agents. Incretin-based therapies, such as the GLP-1 receptor agonist, exenatide, and the DPP-4 inhibitors, sitagliptin and saxagliptin, are important additions to the treatment armamentarium, offering a reduction in hyperglycemia and beneficial effects on weight (reduction with exenatide and neutral with sitagliptin), and have been shown to improve several CV risk factors.

Data from the Centers for Disease Control and Prevention indicate that almost 24 million Americans, or 7.8% of the population, have diabetes; 90% to 95% of these have type 2 diabetes mellitus (T2DM).¹ Diabetes and excessive weight often coexist. An analysis of data from the 1999–2002 National Health and Nutrition Examination Survey (NHANES) showed that among individuals with diabetes, 85% were overweight or obese and 55% were obese.²

Gaps remain in the management of T2DM between the goals for clinical parameters of care (eg, control of glucose, blood pressure [BP], and lipids) and actual clinical practice.³ NHANES data reveal that glycemic control improved from a mean glycosylated hemoglobin A1c (HbA1c) of 7.82% in 1999–2000 to 7.18% in 2003–2004.⁴ Hazard models based on the United Kingdom Prospective Diabetes Study (UKPDS) 10-year outcomes data in 4,320 newly diagnosed T2DM patients suggest that a sustained decrease in HbA1c of 0.511 percentage points could reduce diabetes complications by 10.7%.^4,5

Additional analysis of NHANES data showed that in 2003–2004, about 57% of individuals achieved glycemic control, 48% reached BP targets, and 50% achieved target cholesterol goals.Only about 13% of diabetes patients achieved their target goals for all three parameters concurrently.⁶

This article reviews the association between cardiometabolic risk and the current antihyperglycemic treatments for patients with T2DM, with a focus on the role of incretin-related therapies.

THE IMPORTANCE OF CARDIOMETABOLIC RISK IN T2DM

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among people with diabetes and is the reported cause of mortality in up to 65% of deaths in persons with diabetes in the United States.⁷ The risk of CVD is two- to fourfold greater among adults with diabetes than among adults who do not have diabetes.⁸ The risk of CVD in patients with T2DM was evident in the UKPDS 17, where macrovascular complications, including CVD, were about twice as common as microvascular complications (20% vs 9%) after 9 years of follow-up.⁹ A study that involved more than 44,000 patients showed an almost double rate of mortality from all causes among individuals with T2DM compared with those with no diabetes (hazard ratio, 1.93; 95% confidence interval, 1.89 to 1.97).¹⁰ Current guidelines recommend aggressive management of CV risk factors, including BP control, correction of atherogenic dyslipidemia, glycemic control, weight reduction for those who are overweight or obese, and smoking cessation for those who smoke.^3,11 Lifestyle interventions, including weight reduction and appropriately prescribed physical activity, result in reduced CV risk factors, which can help slow the progression of T2DM.¹²

GOALS OF T2DM THERAPY

Several studies have demonstrated that glycemic control can delay or prevent the development and progression of microvascular complications.^13,14 UKPDS 33 showed that more intensive blood glucose control (median HbA1c 7.0%) in patients with T2DM followed over 10 years significantly (P = .029) reduced the risk for any diabetes-related end point by 12% compared with conventional therapy (median HbA1c 7.9%). Most of the risk reduction was accounted for by a 25% risk reduction in microvascular end points (P = .0099).¹³ Another report (UKPDS 35) demonstrated that HbA1c was strongly related to microvascular effects, with a 1% reduction in HbA1c associated with a 37% reduction in microvascular complications.¹⁴

Does intensive glucose control reduce CV risk?

To resolve the ongoing question of whether intensive glucose control can lead to a reduction in CV risk in patients with T2DM, three large, long-term trials were conducted within the last decade.^15–18 Two of these, the Action to Control Cardiovascular Risk in Diabetes (ACCORD) and Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) trials, each enrolled more than 10,000 previously treated patients with long-standing T2DM. Patients were randomized to standard or intensive glycemic control for 3.5 years in the ACCORD trial and for 5 years in the ADVANCE trial.^15,16

The ACCORD and ADVANCE trials, along with the smaller Veterans Administration Diabetes Trial (VADT) (N = 1,791), failed to show that more intensive glycemic control significantly reduced CVD.^15–17 Additionally, the glycemic control component of ACCORD was halted because of increased mortality in the intensive arm compared with the standard arm.¹⁵ Further analyses of ACCORD data presented at the 69th Scientific Sessions of the American Diabetes Association (ADA) showed that HbA1c values lower than 7.0% did not explain the increased mortality. The 20% higher risk of death for every 1.0% increase in HbA1c greater than 6.0% suggests that glucose concentrations even lower than the general HbA1c goal of less than 7.0% may be appropriate in some patients.¹⁸ The most recent finding from VADT was that CV risk was dependent on disease duration and presence of comorbidities. Intensive therapy seemed to work best in patients with diabetes of less than 15 years’ duration, while risk of a CV event was more than doubled with intensive therapy in patients having diabetes for more than 21 years.

Clarification of treatment goals

A position statement of the ADA and a scientific statement of the American College of Cardiology Foundation and the American Heart Association¹⁹ concluded that the “evidence obtained from ACCORD, ADVANCE, and VADT does not suggest the need for major changes in glycemic control targets but, rather, additional clarification of the language that has consistently stressed individualization.” They state that while the general HbA1c goal of less than 7.0% seems reasonable, even lower HbA1c goals may be appropriate for some patients if they can be achieved without significant hypoglycemia or other adverse effects. Such patients might include those with diabetes of short duration, long life expectancy, or no significant CVD or hypoglycemia. Conversely, higher HbA1c goals may be appropriate for patients with limited life expectancy, a history of severe hypoglycemia, established microvascular or macrovascular complications, significant other comorbid conditions, or longstanding diabetes in whom an HbA1c of less than 7.0% has been difficult to attain despite optimal treatment and diabetes self-management education.¹⁹

 

 

Long-term risk reduction

A 10-year, postinterventional follow-up study (UKPDS 80) of the UKPDS survivor cohort was reported recently.²⁰ Results showed that despite an early loss of glycemic differences between patients treated with diet and those treated with intensive regimens (sulfonylurea or insulin; metformin in overweight patients), the pharmacotherapy group demonstrated a prolonged reduction in microvascular risk as well as a significant reduction in the risk for myocardial infarction (15% [P = .01] in the sulfonylurea-insulin group and 33% [P = .005] in the metformin group) and death from any cause.²⁰ This suggests that early improvement in glycemic control is associated with long-term benefits in the micro- and macrovascular health of patients with T2DM.

Additionally, the recent long-term follow-up of the Steno-2 study²¹ showed that a multifactorial intervention striving for intensive glucose, BP, and lipid control that included the use of renin-angiotensin system blockers, aspirin, and lipid-lowering agents not only reduced the risk of nonfatal CVD among patients with T2DM and microalbuminuria, but also had sustained beneficial effects on vascular complications and on rates of death from any cause and from CV causes. From a health care payer perspective, intensive multifactorial intervention was more likely to be cost-effective than conventional treatment in Denmark, especially if applied in a primary care setting.²²

Comprehensive care needed

The lower-than-expected rates of CV outcomes in the ACCORD, ADVANCE, VADT, and Steno-2 studies reinforce the importance of comprehensive diabetes care that treats not only hyperglycemia but also elevated BP and dyslipidemia; these are considered the “ABCs” of diabetes.^11,19 The 2009 ADA standards of medical care guidelines recommend that for most T2DM patients, HbA1c should be maintained at less than 7.0%,³ while the American Association of Clinical Endocrinologists (AACE) 2007 guidelines state that HbA1c should be 6.5% or less.¹¹ Both organizations stress the importance of individualized goals, as discussed above, and advocate BP goals of less than 130/80 mm Hg and dyslipidemia goals of low-density lipoprotein cholesterol (LDL-C) less than 100 mg/dL, high-density lipoprotein cholesterol (HDL-C) greater than 40 mg/dL for men and 50 mg/dL for women, and triglycerides less than 150 mg/dL. It is recommended that an optional LDL-C goal of less than 70 mg/dL be considered for individuals with overt CVD.

CURRENT ANTIHYPERGLYCEMIC TREATMENT STRATEGIES

In response to new insights from clinical research and emerging treatment strategies, disease-specific organizations and medical specialty societies regularly revise and update their treatment guidelines and algorithms. These resources recommend that glycemic progress should be regularly monitored and pharmacologic therapy titrated or new drugs added promptly if glycemic goals are not met after 2 to 3 months.

Several algorithms combine scientific evidence with expert clinical opinion to guide physicians in treating their patients with T2DM. The American College of Endocrinology (ACE)/AACE road maps are designed to help develop individualized treatment regimens to achieve an HbA1c of 6.5% or less.²³ The algorithm from a writing group assembled by the ADA and the European Association for the Study of Diabetes (EASD) similarly promotes pharmacologic treatment together with lifestyle modifications to maintain a glycemic goal of HbA1c less than 7.0%.²⁴

OVERVIEW OF ANTIHYPERGLYCEMIC TREATMENT APPROACHES

Lifestyle measures, medical nutrition therapy, and appropriately prescribed physical activity are recommended for virtually all patients with T2DM, as well as weight loss for those who are overweight or obese. Unfortunately, many patients cannot achieve glycemic goals with lifestyle measures alone and require the addition of pharmacotherapy.³ Extensive development of new therapies during the past 15 years has resulted in more than 11 classes of approved antihyperglycemic medications (Table 1) with diverse mechanisms of action and varied effects on HbA1c, body weight, lipids, and other factors.^24–26

Initial oral therapy

T2DM is usually treated initially with a single oral agent. Consistent with the progressive nature of the disease, patients often eventually require one or more additional oral agents and in many cases insulin.^13,27 Choice of specific agents is based on individual patient circumstances, including the need for weight loss and control of fasting versus postprandial glucose, the presence of dyslipidemia and hypertension, and the risk for and potential consequences of hypoglycemia.²⁴ T2DM patients with severely uncontrolled and symptomatic hyperglycemia are best treated, at least initially, with a combination of insulin therapy and lifestyle intervention, often with metformin.

Metformin. The recently revised ADA/EASD writing group algorithm recommends that patients not requiring initial insulin begin treatment with metformin at the time of diagnosis unless there are contraindications.²⁴ Metformin is not associated with hypoglycemia and is considered weight-neutral, although some patients may lose weight.²⁸

Sulfonylureas. Sulfonylureas stimulate insulin secretion from pancreatic beta cells; their use may be associated with hypoglycemia and weight gain. Mechanisms for weight gain with sulfonylureas include reduction of glucosuria and increased caloric intake to prevent or treat hypoglycemia.^11,28 Nateglinide and repaglinide are nonsulfonylurea oral insulin secretagogues. They result in rapid and relatively short-lived insulin responses and are usually administered three times a day, before each meal. Their use may be associated with weight gain and hypoglycemia.¹¹

Thiazolidinediones. Thiazolidinediones (TZD) increase insulin sensitivity in muscle, adipose tissue, and the liver. Hypoglycemia is uncommon with TZD monotherapy but weight gain related to increased and redistributed adiposity and fluid retention frequently occurs.

Alpha-glucosidase inhibitors. The alpha-glucosidase inhibitors are administered before meals and primarily reduce postprandial hyperglycemia. They are generally weight-neutral.²⁸

Insulin. Insulin and insulin analogues are the most effective antihyperglycemic agents, but their use can be associated with hypoglycemia and clinically significant weight gain.²⁸

Colesevelam. Colesevelam is a bile acid sequestrant that was recently approved by the US Food and Drug Administration as an antihyperglycemic therapy in people with T2DM. At a dosage of 1.875 g BID or 3.75 g QD in combination with a sulfonylurea, metformin, or insulin therapy, reductions in HbA1c compared with placebo in clinical trials of colesevelam have ranged from ­–0.5% to –0.7% (P < .02). Frequency of hypoglycemia and weight gain is low with this agent.²⁶

Weight management. Weight reduction is important for overweight or obese patients with T2DM.^27,28 Even moderate weight loss (5% of body weight) can be associated with improved insulin action and reduced hyperglycemia.²⁹ Conversely, weight gain has been shown to worsen hyperglycemia and other CV risk factors. Treatment-related weight gain can also lead to decreased regimen adherence, contributing to poor glycemic control.²⁸

 

 

THE ROLE OF INCRETIN HORMONES AND INCRETIN-BASED THERAPIES IN T2DM PATIENTS

Over the last few years, the role of incretin hormones and their contribution to diabetes pathophysiology has become more apparent. The incretin effect refers to the observation that orally administered glucose elicits a greater insulin response than does glucose administered intravenously to produce equivalent blood glucose concentrations.^30,31 The incretin effect is diminished in patients with T2DM.

Hormone mediation of the incretin effect

The two hormones that mediate the incretin effect are GIP (also known as gastric inhibitory polypeptide or glucose-dependent insulinotropic polypeptide) and glucagon-like peptide−1 (GLP-1).^30,31 GLP-1 has several glucoregulatory actions, including enhancement of endogenous insulin release and suppression of inappropriate glucagon secretion, both in a glucose-dependent manner. Therefore, these effects of GLP-1 occur only when glucose concentrations are elevated, thereby minimizing the risk of hypoglycemia. GLP-1 also regulates gastric emptying; infusions of GLP-1 can slow the accelerated emptying that is often present in T2DM patients. GLP-1 also increases satiety and decreases food intake via a central mechanism.³¹

Because GLP-1 is rapidly inactivated by the enzyme dipeptidyl peptidase–4 (DPP-4), therapeutic use of GLP-1 would require continuous infusion, which is impractical.^30,31 Two strategies have been used to produce incretin-related therapies. One, inhibition of the DPP-4 enzyme, results in a two- to threefold enhancement of endogenous GLP-1. The other, involving agents that resist breakdown by DPP-4 but bind to and activate the GLP-1 receptor, produces glucoregulatory effects similar to those of GLP-1.³⁰

Following subcutaneous (SC) injection, GLP-1 receptor agonists enhance insulin secretion and suppress inappropriately elevated glucagon, both in a glucose-dependent manner, as well as slow gastric emptying and enhance satiety.³⁰ DPP-4 inhibitors provide glucose-dependent enhanced insulin secretion and glucagon suppression, but they do not have the same effects on gastric emptying or satiety.

Clinically, the GLP-1 receptor agonists improve glycemia and are associated with weight loss.^32–35 Adverse gastrointestinal symptoms are relatively common during the first few weeks of treatment. DPP-4 inhibitors improve glycemia but are weight-neutral and are not generally associated with significant gastrointestinal symptoms.^32,36–38

Incretin-based therapies

Incretin-based therapies are currently part of the antihyperglycemic armamentarium.^25,32 The AACE guidelines¹¹ and the ACE/AACE roadmaps²³ include the GLP-1 receptor agonist exenatide and the DPP-4 inhibitor sitagliptin among antihyperglycemic therapies for patients with T2DM. The most recent update of the consensus algorithm statement of a joint ADA/EASD writing group included GLP-1 receptor agonists (but not DPP-4 inhibitors) in tier 2 of preferred agents, especially for patients who have concerns related to weight and hypoglycemia.²⁴ They noted that DPP-4 inhibitors may be appropriate choices in selected patients.

DPP-4 inhibitors: sitagliptin, saxagliptin. Until recently, sitagliptin was the only DPP-4 inhibitor available in the United States. Sitagliptin is approved by the FDA for treatment of T2DM at a recommended oral dosage of 100 mg QD, either as monotherapy or in combination with other oral antihyperglycemic medications. The dosage of sitagliptin should be reduced to 50 mg/day in patients with creatinine clearance (CrCl) levels that are between 30 mL/min and 50 mL/min and to 25 mg/day in those with CrCl less than 30 mL/min.³⁹

In a meta-analysis of incretin-based therapies, DPP-4 inhibitors produced a reduction in HbA1c compared with placebo (weighted mean difference of –0.74%; 95% confidence interval, –0.85% to –0.62%).³² DPP-4 inhibitor antihyperglycemic efficacy has been shown to be similar whether used as a monotherapy or add-on therapy.^32,37,38 This same meta-analysis showed DPP-4 inhibitors as having a neutral effect on weight.³² More recently, a single-pill combination of metformin and sitagliptin was approved.⁴⁰

A study comparing metformin, sitagliptin, and the combination of the two as initial monotherapy in T2DM patients with a baseline HbA1c of 8.8% showed 24-week HbA1c reductions from baseline of –0.66% with sitagliptin 100 mg QD, –0.82% with metformin 500 mg BID, and –1.90% with sitagliptin 50 mg + metformin 1,000 mg BID.⁴¹

On July 31, 2009, the FDA approved another DPP-4 inhibitor, saxagliptin, for the treatment of T2DM either as monotherapy or in combination with metformin, a sulfonylurea, or a TZD.⁴²

GLP-1 receptor agonist: exenatide. Exenatide, the only FDA-approved GLP-1 receptor agonist, is the synthetic version of exendin-4, which binds to the human GLP-1 receptor and in vitro possesses many of the glucoregulatory effects of endogenous GLP-1.^30,32 Exenatide is indicated as monotherapy or adjunctive therapy for patients with T2DM who have not achieved adequate glycemic control with metformin, a sulfonylurea, a TZD, or metformin in combination with a sulfonylurea or a TZD.⁴³ Exenatide is administered by SC injection BID at a starting dosage of 5 mg BID for 4 weeks, followed by an increase to 10 mg BID.

Exenatide has been shown not only to enhance glucose-dependent insulin secretion but also to restore impaired first-phase insulin response in subjects with T2DM. Exenatide also helps control postprandial glycemic excursions by suppressing inappropriate glucagon secretion, slowing accelerated gastric emptying, and enhancing satiety. The increased satiety results in decreased food intake and weight loss.^31,44 In a recent head-to-head crossover study, exenatide was shown to be more effective than sitagliptin in lowering postprandial glucose concentrations, increasing insulin secretion, and reducing postprandial glucagon secretion.⁴⁵ Exenatide also slowed gastric emptying and reduced caloric intake.

Exenatide, in most studies, resulted in a placebo-subtracted HbA1c reduction of approximately –1.0% and in one study lowered HbA1c from baseline by –1.5%. Completer analyses have shown HbA1c reductions of –1.0% up to 3 years and –0.8% up to 3.5 years. Exenatide has also been associated with a mean weight loss of as much as –3.6 kg at 30 weeks and as much as –5.3 kg at 3.5 years.^{33–35,46,47} A 1-year study showed that exenatide improved beta-cell secretory function compared with insulin glargine in metformin-treated patients with T2DM.⁴⁸ Long-term data, including findings from completed and intention-to-treat analyses of 82 weeks⁴⁹ to at least 3 years⁴⁷ have demonstrated that exenatide improved CV risk factors, including those related to BP, lipids, and hepatic injury biomarkers.

Therapies in development

Incretin-based therapies in development include a novel once-weekly formulation of exenatide; taspoglutide, another once-weekly GLP-1 receptor agonist; and liraglutide, a GLP-1 receptor agonist that is administered once daily.⁵⁰ Liraglutide is currently being evaluated in clinical trials as a once-daily SC injection.^51–53 Liraglutide has been reported to reduce HbA1c by –1.1% at 26 weeks and up to –1.14% at 52 weeks and result in weight loss (up to –2.8 kg at 26 weeks and up to –2.5 kg at 52 weeks) in patients with T2DM who are treatment-naïve or taking other antidiabetes agents, including metformin, sulfonylurea, and TZD.^51–53 Evaluation of the once-weekly formulation of exenatide showed reductions in HbA1c of –1.9% at 30 weeks and –2.0% at 52 weeks with a weight loss of –3.7 kg at 30 weeks and –4.1 kg over 52 weeks of treatment.^46,54

CONCLUSION

In the United States, the epidemics of excessive weight and T2DM have contributed to an increased medical risk for many individuals. Comprehensive diabetes treatments targeting not only hyperglycemia but also frequently associated overweight/obesity, hypertension, and dyslipidemia will be required to reduce such risk. Current treatment strategies have evolved based on updated clinical guidelines and trials, as well as practice experience, including those related to newer agents. Incretin-based therapies, such as the GLP-1 receptor agonist, exenatide, and the DPP-4 inhibitors, sitagliptin and saxagliptin, are important additions to the treatment armamentarium, offering a reduction in hyperglycemia and beneficial effects on weight (reduction with exenatide and neutral with sitagliptin), and have been shown to improve several CV risk factors.

Data from the Centers for Disease Control and Prevention indicate that almost 24 million Americans, or 7.8% of the population, have diabetes; 90% to 95% of these have type 2 diabetes mellitus (T2DM).¹ Diabetes and excessive weight often coexist. An analysis of data from the 1999–2002 National Health and Nutrition Examination Survey (NHANES) showed that among individuals with diabetes, 85% were overweight or obese and 55% were obese.²

Gaps remain in the management of T2DM between the goals for clinical parameters of care (eg, control of glucose, blood pressure [BP], and lipids) and actual clinical practice.³ NHANES data reveal that glycemic control improved from a mean glycosylated hemoglobin A1c (HbA1c) of 7.82% in 1999–2000 to 7.18% in 2003–2004.⁴ Hazard models based on the United Kingdom Prospective Diabetes Study (UKPDS) 10-year outcomes data in 4,320 newly diagnosed T2DM patients suggest that a sustained decrease in HbA1c of 0.511 percentage points could reduce diabetes complications by 10.7%.^4,5

Additional analysis of NHANES data showed that in 2003–2004, about 57% of individuals achieved glycemic control, 48% reached BP targets, and 50% achieved target cholesterol goals.Only about 13% of diabetes patients achieved their target goals for all three parameters concurrently.⁶

This article reviews the association between cardiometabolic risk and the current antihyperglycemic treatments for patients with T2DM, with a focus on the role of incretin-related therapies.

THE IMPORTANCE OF CARDIOMETABOLIC RISK IN T2DM

Cardiovascular disease (CVD) is the leading cause of morbidity and mortality among people with diabetes and is the reported cause of mortality in up to 65% of deaths in persons with diabetes in the United States.⁷ The risk of CVD is two- to fourfold greater among adults with diabetes than among adults who do not have diabetes.⁸ The risk of CVD in patients with T2DM was evident in the UKPDS 17, where macrovascular complications, including CVD, were about twice as common as microvascular complications (20% vs 9%) after 9 years of follow-up.⁹ A study that involved more than 44,000 patients showed an almost double rate of mortality from all causes among individuals with T2DM compared with those with no diabetes (hazard ratio, 1.93; 95% confidence interval, 1.89 to 1.97).¹⁰ Current guidelines recommend aggressive management of CV risk factors, including BP control, correction of atherogenic dyslipidemia, glycemic control, weight reduction for those who are overweight or obese, and smoking cessation for those who smoke.^3,11 Lifestyle interventions, including weight reduction and appropriately prescribed physical activity, result in reduced CV risk factors, which can help slow the progression of T2DM.¹²

GOALS OF T2DM THERAPY

Several studies have demonstrated that glycemic control can delay or prevent the development and progression of microvascular complications.^13,14 UKPDS 33 showed that more intensive blood glucose control (median HbA1c 7.0%) in patients with T2DM followed over 10 years significantly (P = .029) reduced the risk for any diabetes-related end point by 12% compared with conventional therapy (median HbA1c 7.9%). Most of the risk reduction was accounted for by a 25% risk reduction in microvascular end points (P = .0099).¹³ Another report (UKPDS 35) demonstrated that HbA1c was strongly related to microvascular effects, with a 1% reduction in HbA1c associated with a 37% reduction in microvascular complications.¹⁴

Does intensive glucose control reduce CV risk?

To resolve the ongoing question of whether intensive glucose control can lead to a reduction in CV risk in patients with T2DM, three large, long-term trials were conducted within the last decade.^15–18 Two of these, the Action to Control Cardiovascular Risk in Diabetes (ACCORD) and Action in Diabetes and Vascular Disease: Preterax and Diamicron Modified Release Controlled Evaluation (ADVANCE) trials, each enrolled more than 10,000 previously treated patients with long-standing T2DM. Patients were randomized to standard or intensive glycemic control for 3.5 years in the ACCORD trial and for 5 years in the ADVANCE trial.^15,16

The ACCORD and ADVANCE trials, along with the smaller Veterans Administration Diabetes Trial (VADT) (N = 1,791), failed to show that more intensive glycemic control significantly reduced CVD.^15–17 Additionally, the glycemic control component of ACCORD was halted because of increased mortality in the intensive arm compared with the standard arm.¹⁵ Further analyses of ACCORD data presented at the 69th Scientific Sessions of the American Diabetes Association (ADA) showed that HbA1c values lower than 7.0% did not explain the increased mortality. The 20% higher risk of death for every 1.0% increase in HbA1c greater than 6.0% suggests that glucose concentrations even lower than the general HbA1c goal of less than 7.0% may be appropriate in some patients.¹⁸ The most recent finding from VADT was that CV risk was dependent on disease duration and presence of comorbidities. Intensive therapy seemed to work best in patients with diabetes of less than 15 years’ duration, while risk of a CV event was more than doubled with intensive therapy in patients having diabetes for more than 21 years.

Clarification of treatment goals

A position statement of the ADA and a scientific statement of the American College of Cardiology Foundation and the American Heart Association¹⁹ concluded that the “evidence obtained from ACCORD, ADVANCE, and VADT does not suggest the need for major changes in glycemic control targets but, rather, additional clarification of the language that has consistently stressed individualization.” They state that while the general HbA1c goal of less than 7.0% seems reasonable, even lower HbA1c goals may be appropriate for some patients if they can be achieved without significant hypoglycemia or other adverse effects. Such patients might include those with diabetes of short duration, long life expectancy, or no significant CVD or hypoglycemia. Conversely, higher HbA1c goals may be appropriate for patients with limited life expectancy, a history of severe hypoglycemia, established microvascular or macrovascular complications, significant other comorbid conditions, or longstanding diabetes in whom an HbA1c of less than 7.0% has been difficult to attain despite optimal treatment and diabetes self-management education.¹⁹

 

 

Long-term risk reduction

A 10-year, postinterventional follow-up study (UKPDS 80) of the UKPDS survivor cohort was reported recently.²⁰ Results showed that despite an early loss of glycemic differences between patients treated with diet and those treated with intensive regimens (sulfonylurea or insulin; metformin in overweight patients), the pharmacotherapy group demonstrated a prolonged reduction in microvascular risk as well as a significant reduction in the risk for myocardial infarction (15% [P = .01] in the sulfonylurea-insulin group and 33% [P = .005] in the metformin group) and death from any cause.²⁰ This suggests that early improvement in glycemic control is associated with long-term benefits in the micro- and macrovascular health of patients with T2DM.

Additionally, the recent long-term follow-up of the Steno-2 study²¹ showed that a multifactorial intervention striving for intensive glucose, BP, and lipid control that included the use of renin-angiotensin system blockers, aspirin, and lipid-lowering agents not only reduced the risk of nonfatal CVD among patients with T2DM and microalbuminuria, but also had sustained beneficial effects on vascular complications and on rates of death from any cause and from CV causes. From a health care payer perspective, intensive multifactorial intervention was more likely to be cost-effective than conventional treatment in Denmark, especially if applied in a primary care setting.²²

Comprehensive care needed

The lower-than-expected rates of CV outcomes in the ACCORD, ADVANCE, VADT, and Steno-2 studies reinforce the importance of comprehensive diabetes care that treats not only hyperglycemia but also elevated BP and dyslipidemia; these are considered the “ABCs” of diabetes.^11,19 The 2009 ADA standards of medical care guidelines recommend that for most T2DM patients, HbA1c should be maintained at less than 7.0%,³ while the American Association of Clinical Endocrinologists (AACE) 2007 guidelines state that HbA1c should be 6.5% or less.¹¹ Both organizations stress the importance of individualized goals, as discussed above, and advocate BP goals of less than 130/80 mm Hg and dyslipidemia goals of low-density lipoprotein cholesterol (LDL-C) less than 100 mg/dL, high-density lipoprotein cholesterol (HDL-C) greater than 40 mg/dL for men and 50 mg/dL for women, and triglycerides less than 150 mg/dL. It is recommended that an optional LDL-C goal of less than 70 mg/dL be considered for individuals with overt CVD.

CURRENT ANTIHYPERGLYCEMIC TREATMENT STRATEGIES

In response to new insights from clinical research and emerging treatment strategies, disease-specific organizations and medical specialty societies regularly revise and update their treatment guidelines and algorithms. These resources recommend that glycemic progress should be regularly monitored and pharmacologic therapy titrated or new drugs added promptly if glycemic goals are not met after 2 to 3 months.

Several algorithms combine scientific evidence with expert clinical opinion to guide physicians in treating their patients with T2DM. The American College of Endocrinology (ACE)/AACE road maps are designed to help develop individualized treatment regimens to achieve an HbA1c of 6.5% or less.²³ The algorithm from a writing group assembled by the ADA and the European Association for the Study of Diabetes (EASD) similarly promotes pharmacologic treatment together with lifestyle modifications to maintain a glycemic goal of HbA1c less than 7.0%.²⁴

OVERVIEW OF ANTIHYPERGLYCEMIC TREATMENT APPROACHES

Lifestyle measures, medical nutrition therapy, and appropriately prescribed physical activity are recommended for virtually all patients with T2DM, as well as weight loss for those who are overweight or obese. Unfortunately, many patients cannot achieve glycemic goals with lifestyle measures alone and require the addition of pharmacotherapy.³ Extensive development of new therapies during the past 15 years has resulted in more than 11 classes of approved antihyperglycemic medications (Table 1) with diverse mechanisms of action and varied effects on HbA1c, body weight, lipids, and other factors.^24–26

Initial oral therapy

T2DM is usually treated initially with a single oral agent. Consistent with the progressive nature of the disease, patients often eventually require one or more additional oral agents and in many cases insulin.^13,27 Choice of specific agents is based on individual patient circumstances, including the need for weight loss and control of fasting versus postprandial glucose, the presence of dyslipidemia and hypertension, and the risk for and potential consequences of hypoglycemia.²⁴ T2DM patients with severely uncontrolled and symptomatic hyperglycemia are best treated, at least initially, with a combination of insulin therapy and lifestyle intervention, often with metformin.

Metformin. The recently revised ADA/EASD writing group algorithm recommends that patients not requiring initial insulin begin treatment with metformin at the time of diagnosis unless there are contraindications.²⁴ Metformin is not associated with hypoglycemia and is considered weight-neutral, although some patients may lose weight.²⁸

Sulfonylureas. Sulfonylureas stimulate insulin secretion from pancreatic beta cells; their use may be associated with hypoglycemia and weight gain. Mechanisms for weight gain with sulfonylureas include reduction of glucosuria and increased caloric intake to prevent or treat hypoglycemia.^11,28 Nateglinide and repaglinide are nonsulfonylurea oral insulin secretagogues. They result in rapid and relatively short-lived insulin responses and are usually administered three times a day, before each meal. Their use may be associated with weight gain and hypoglycemia.¹¹

Thiazolidinediones. Thiazolidinediones (TZD) increase insulin sensitivity in muscle, adipose tissue, and the liver. Hypoglycemia is uncommon with TZD monotherapy but weight gain related to increased and redistributed adiposity and fluid retention frequently occurs.

Alpha-glucosidase inhibitors. The alpha-glucosidase inhibitors are administered before meals and primarily reduce postprandial hyperglycemia. They are generally weight-neutral.²⁸

Insulin. Insulin and insulin analogues are the most effective antihyperglycemic agents, but their use can be associated with hypoglycemia and clinically significant weight gain.²⁸

Colesevelam. Colesevelam is a bile acid sequestrant that was recently approved by the US Food and Drug Administration as an antihyperglycemic therapy in people with T2DM. At a dosage of 1.875 g BID or 3.75 g QD in combination with a sulfonylurea, metformin, or insulin therapy, reductions in HbA1c compared with placebo in clinical trials of colesevelam have ranged from ­–0.5% to –0.7% (P < .02). Frequency of hypoglycemia and weight gain is low with this agent.²⁶

Weight management. Weight reduction is important for overweight or obese patients with T2DM.^27,28 Even moderate weight loss (5% of body weight) can be associated with improved insulin action and reduced hyperglycemia.²⁹ Conversely, weight gain has been shown to worsen hyperglycemia and other CV risk factors. Treatment-related weight gain can also lead to decreased regimen adherence, contributing to poor glycemic control.²⁸

 

 

THE ROLE OF INCRETIN HORMONES AND INCRETIN-BASED THERAPIES IN T2DM PATIENTS

Over the last few years, the role of incretin hormones and their contribution to diabetes pathophysiology has become more apparent. The incretin effect refers to the observation that orally administered glucose elicits a greater insulin response than does glucose administered intravenously to produce equivalent blood glucose concentrations.^30,31 The incretin effect is diminished in patients with T2DM.

Hormone mediation of the incretin effect

The two hormones that mediate the incretin effect are GIP (also known as gastric inhibitory polypeptide or glucose-dependent insulinotropic polypeptide) and glucagon-like peptide−1 (GLP-1).^30,31 GLP-1 has several glucoregulatory actions, including enhancement of endogenous insulin release and suppression of inappropriate glucagon secretion, both in a glucose-dependent manner. Therefore, these effects of GLP-1 occur only when glucose concentrations are elevated, thereby minimizing the risk of hypoglycemia. GLP-1 also regulates gastric emptying; infusions of GLP-1 can slow the accelerated emptying that is often present in T2DM patients. GLP-1 also increases satiety and decreases food intake via a central mechanism.³¹

Because GLP-1 is rapidly inactivated by the enzyme dipeptidyl peptidase–4 (DPP-4), therapeutic use of GLP-1 would require continuous infusion, which is impractical.^30,31 Two strategies have been used to produce incretin-related therapies. One, inhibition of the DPP-4 enzyme, results in a two- to threefold enhancement of endogenous GLP-1. The other, involving agents that resist breakdown by DPP-4 but bind to and activate the GLP-1 receptor, produces glucoregulatory effects similar to those of GLP-1.³⁰

Following subcutaneous (SC) injection, GLP-1 receptor agonists enhance insulin secretion and suppress inappropriately elevated glucagon, both in a glucose-dependent manner, as well as slow gastric emptying and enhance satiety.³⁰ DPP-4 inhibitors provide glucose-dependent enhanced insulin secretion and glucagon suppression, but they do not have the same effects on gastric emptying or satiety.

Clinically, the GLP-1 receptor agonists improve glycemia and are associated with weight loss.^32–35 Adverse gastrointestinal symptoms are relatively common during the first few weeks of treatment. DPP-4 inhibitors improve glycemia but are weight-neutral and are not generally associated with significant gastrointestinal symptoms.^32,36–38

Incretin-based therapies

Incretin-based therapies are currently part of the antihyperglycemic armamentarium.^25,32 The AACE guidelines¹¹ and the ACE/AACE roadmaps²³ include the GLP-1 receptor agonist exenatide and the DPP-4 inhibitor sitagliptin among antihyperglycemic therapies for patients with T2DM. The most recent update of the consensus algorithm statement of a joint ADA/EASD writing group included GLP-1 receptor agonists (but not DPP-4 inhibitors) in tier 2 of preferred agents, especially for patients who have concerns related to weight and hypoglycemia.²⁴ They noted that DPP-4 inhibitors may be appropriate choices in selected patients.

DPP-4 inhibitors: sitagliptin, saxagliptin. Until recently, sitagliptin was the only DPP-4 inhibitor available in the United States. Sitagliptin is approved by the FDA for treatment of T2DM at a recommended oral dosage of 100 mg QD, either as monotherapy or in combination with other oral antihyperglycemic medications. The dosage of sitagliptin should be reduced to 50 mg/day in patients with creatinine clearance (CrCl) levels that are between 30 mL/min and 50 mL/min and to 25 mg/day in those with CrCl less than 30 mL/min.³⁹

In a meta-analysis of incretin-based therapies, DPP-4 inhibitors produced a reduction in HbA1c compared with placebo (weighted mean difference of –0.74%; 95% confidence interval, –0.85% to –0.62%).³² DPP-4 inhibitor antihyperglycemic efficacy has been shown to be similar whether used as a monotherapy or add-on therapy.^32,37,38 This same meta-analysis showed DPP-4 inhibitors as having a neutral effect on weight.³² More recently, a single-pill combination of metformin and sitagliptin was approved.⁴⁰

A study comparing metformin, sitagliptin, and the combination of the two as initial monotherapy in T2DM patients with a baseline HbA1c of 8.8% showed 24-week HbA1c reductions from baseline of –0.66% with sitagliptin 100 mg QD, –0.82% with metformin 500 mg BID, and –1.90% with sitagliptin 50 mg + metformin 1,000 mg BID.⁴¹

On July 31, 2009, the FDA approved another DPP-4 inhibitor, saxagliptin, for the treatment of T2DM either as monotherapy or in combination with metformin, a sulfonylurea, or a TZD.⁴²

GLP-1 receptor agonist: exenatide. Exenatide, the only FDA-approved GLP-1 receptor agonist, is the synthetic version of exendin-4, which binds to the human GLP-1 receptor and in vitro possesses many of the glucoregulatory effects of endogenous GLP-1.^30,32 Exenatide is indicated as monotherapy or adjunctive therapy for patients with T2DM who have not achieved adequate glycemic control with metformin, a sulfonylurea, a TZD, or metformin in combination with a sulfonylurea or a TZD.⁴³ Exenatide is administered by SC injection BID at a starting dosage of 5 mg BID for 4 weeks, followed by an increase to 10 mg BID.

Exenatide has been shown not only to enhance glucose-dependent insulin secretion but also to restore impaired first-phase insulin response in subjects with T2DM. Exenatide also helps control postprandial glycemic excursions by suppressing inappropriate glucagon secretion, slowing accelerated gastric emptying, and enhancing satiety. The increased satiety results in decreased food intake and weight loss.^31,44 In a recent head-to-head crossover study, exenatide was shown to be more effective than sitagliptin in lowering postprandial glucose concentrations, increasing insulin secretion, and reducing postprandial glucagon secretion.⁴⁵ Exenatide also slowed gastric emptying and reduced caloric intake.

Exenatide, in most studies, resulted in a placebo-subtracted HbA1c reduction of approximately –1.0% and in one study lowered HbA1c from baseline by –1.5%. Completer analyses have shown HbA1c reductions of –1.0% up to 3 years and –0.8% up to 3.5 years. Exenatide has also been associated with a mean weight loss of as much as –3.6 kg at 30 weeks and as much as –5.3 kg at 3.5 years.^{33–35,46,47} A 1-year study showed that exenatide improved beta-cell secretory function compared with insulin glargine in metformin-treated patients with T2DM.⁴⁸ Long-term data, including findings from completed and intention-to-treat analyses of 82 weeks⁴⁹ to at least 3 years⁴⁷ have demonstrated that exenatide improved CV risk factors, including those related to BP, lipids, and hepatic injury biomarkers.

Therapies in development

Incretin-based therapies in development include a novel once-weekly formulation of exenatide; taspoglutide, another once-weekly GLP-1 receptor agonist; and liraglutide, a GLP-1 receptor agonist that is administered once daily.⁵⁰ Liraglutide is currently being evaluated in clinical trials as a once-daily SC injection.^51–53 Liraglutide has been reported to reduce HbA1c by –1.1% at 26 weeks and up to –1.14% at 52 weeks and result in weight loss (up to –2.8 kg at 26 weeks and up to –2.5 kg at 52 weeks) in patients with T2DM who are treatment-naïve or taking other antidiabetes agents, including metformin, sulfonylurea, and TZD.^51–53 Evaluation of the once-weekly formulation of exenatide showed reductions in HbA1c of –1.9% at 30 weeks and –2.0% at 52 weeks with a weight loss of –3.7 kg at 30 weeks and –4.1 kg over 52 weeks of treatment.^46,54

CONCLUSION

In the United States, the epidemics of excessive weight and T2DM have contributed to an increased medical risk for many individuals. Comprehensive diabetes treatments targeting not only hyperglycemia but also frequently associated overweight/obesity, hypertension, and dyslipidemia will be required to reduce such risk. Current treatment strategies have evolved based on updated clinical guidelines and trials, as well as practice experience, including those related to newer agents. Incretin-based therapies, such as the GLP-1 receptor agonist, exenatide, and the DPP-4 inhibitors, sitagliptin and saxagliptin, are important additions to the treatment armamentarium, offering a reduction in hyperglycemia and beneficial effects on weight (reduction with exenatide and neutral with sitagliptin), and have been shown to improve several CV risk factors.