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To determine whether dapagliflozin, which selectively inhibits renal glucose reabsorption, lowers hyperglycemia in patients with type 2 diabetes that is poorly controlled with high insulin doses plus oral antidiabetic agents (OADs).
This was a randomized, double-blind, three-arm parallel-group, placebo-controlled, 26-center trial (U.S. and Canada). Based on data from an insulin dose-adjustment setting cohort (n = 4), patients in the treatment cohort (n = 71) were randomly assigned 1:1:1 to placebo, 10 mg dapagliflozin, or 20 mg dapagliflozin, plus OAD(s) and 50% of their daily insulin dose. The primary outcome was change from baseline in A1C at week 12 (dapagliflozin vs. placebo, last observation carried forward [LOCF]).
At week 12 (LOCF), the 10- and 20-mg dapagliflozin groups demonstrated −0.70 and −0.78% mean differences in A1C change from baseline versus placebo. In both dapagliflozin groups, 65.2% of patients achieved a decrease from baseline in A1C ≥0.5% versus 15.8% in the placebo group. Mean changes from baseline in fasting plasma glucose (FPG) were +17.8, +2.4, and −9.6 mg/dl (placebo, 10 mg dapagliflozin, and 20 mg dapagliflozin, respectively). Postprandial glucose (PPG) reductions with dapagliflozin also showed dose dependence. Mean changes in total body weight were −1.9, −4.5, and −4.3 kg (placebo, 10 mg dapagliflozin, and 20 mg dapagliflozin). Overall, adverse events were balanced across all groups, although more genital infections occurred in the 20-mg dapagliflozin group than in the placebo group.
In patients receiving high insulin doses plus insulin sensitizers who had their baseline insulin reduced by 50%, dapagliflozin decreased A1C, produced better FPG and PPG levels, and lowered weight more than placebo.
Treatment of hyperglycemia in patients with type 2 diabetes remains a challenge, particularly in those who require insulin as the disease progresses (1,2). Various combinations of insulin with oral antidiabetic agents (OADs) have been investigated (2–8). Often, these combination therapies become less effective in controlling hyperglycemia over time, particularly as a result of weight gain and worsening insulin resistance as well as progressive failure of insulin secretion.
Hypoglycemia, weight gain, and subsequent increased insulin resistance are significant factors that limit optimal titration and effectiveness of insulin (2). Weight gain with insulin therapy, used alone or with OADs (7–9), is in part a consequence of reducing glucosuria (10,11). Among commonly used OADs, thiazolidinediones (TZDs) and sulfonylureas intrinsically contribute to weight gain, whereas metformin causes weight loss and dipeptidyl peptidase-4 inhibitors are weight neutral. Overall, there is a need for novel agents that can be safely administered to help achieve glycemic targets without increasing the risks of weight gain or hypoglycemia.
A novel approach to treating hyperglycemia targets receptors for renal glucose reabsorption (12). Agents that selectively block sodium-glucose cotransporter 2 (SGLT2), located in the proximal tubule of the kidney, inhibit glucose reabsorption and induce its elimination through urinary excretion (13). Preclinical models have shown that SGLT2 inhibition lowers blood glucose independently of insulin (14–17). Dapagliflozin, a highly selective inhibitor of SGLT2, has demonstrated efficacy, alone or in combination with metformin, in reducing hyperglycemia in patients with type 2 diabetes (18,19) but has not been tested in patients requiring insulin. This study was designed to determine whether dapagliflozin is effective in lowering blood glucose in patients with type 2 diabetes who have not responded adequately to insulin combined with oral therapies that act through insulin-dependent mechanisms.
This randomized, single- and double-blind, three-arm parallel-group, placebo-controlled trial was conducted in 26 study centers in the U.S. and Canada. Institutional review boards or independent ethics committees for each center approved the protocol. All patients provided written informed consent. The trial consisted of a 10- to 21-day qualification period, 12-week treatment phase, and 4-week follow-up phase. Starting at day −7, patients were instructed on a diet and exercise program, pursuant to American Diabetes Association or similar local guidelines, to be followed throughout the study. Until day 1, patients maintained their stable dose of OADs and insulin.
We used an adaptive trial design with two cohorts. The purpose of the first cohort was to identify a reduced insulin starting dose unlikely to cause hypoglycemia after addition of dapagliflozin. Four patients received single-blind 20 mg dapagliflozin after having their daily insulin dose decreased by 50%. If at least one patient recorded a glucose value ≤100 mg/dl in this cohort, lesser dose reductions (i.e., 30 or 10%) would not be tested, and the daily insulin dose reduction for patients in the larger second cohort would be set at 50%. This was the case, and in the second treatment cohort, patients were randomly assigned 1:1:1 on day 1 to double-blind placebo, 10 mg dapagliflozin, or 20 mg dapagliflozin once daily, in addition to open-label therapy with 50% of their usual daily insulin dose and their OAD(s).
Patients performed self-monitoring of blood glucose five times daily during the 3–5 days before clinic visits at weeks 1, 2, 4, 6, 8, 10, and 12. No dose modifications of blinded study medication or OAD(s) were allowed during the treatment phase. In patients with or at risk of hypoglycemia, insulin could be down-titrated for self-monitored blood glucose levels <54 mg/dl or mean daily glucose <100 mg/dl or when clinically necessary as determined by the investigator. Patients experiencing major hypoglycemia were discontinued from the study. For any fasting plasma glucose (FPG) level >240 mg/dl at weeks 4 and 6, >220 mg/dl at week 8, or >200 mg/dl at week 10, the insulin dose could be increased after a retest. Patients lacking glycemic control despite up-titration or whose modified insulin dose exceeded baseline were discontinued from the study.
Men and women with type 2 diabetes, aged 18–75 years, with BMI ≤45 kg/m2 and A1C 7.5–10%, were enrolled between October 2006 and November 2007. Patients were receiving stable-dose insulin sensitizer therapy (metformin ≥1,000 mg and/or pioglitazone ≥30 mg or rosiglitazone 4 mg) for ≥6 weeks and insulin therapy for ≥12 weeks before enrollment (insulin dose must have been ≥50 units of U100 daily and stable for ≥6 weeks). Laboratory criteria included fasting C-peptide ≥0.8 ng/ml, serum creatinine <1.5 mg/dl (men) or <1.4 mg/dl (women), and a urine microalbumin-to-creatinine ratio <300 mg/g or, if exceeded on spot check, a 24-h urine total protein <3 g/24 h. Major exclusion criteria were a history of type 1 diabetes, aspartate transaminase and/or alanine transaminase >2.5 times the upper limits of normal, creatine kinase ≥3 times the upper limits of normal, symptoms of severely uncontrolled diabetes, a history of severe hypoglycemia, and unstable condition or serious cardiovascular, renal, or hepatic disease.
The primary efficacy measure was change from baseline in A1C at week 12 (last observation carried forward [LOCF]). Secondary efficacy measures at week 12 (LOCF) included changes from baseline in FPG and total daily dose of insulin (TDDI), the proportion of patients achieving a decrease in A1C ≥0.5% from baseline, and the proportion of patients achieving A1C <7%. Tertiary end points included changes from baseline in total body weight and in postprandial glucose (PPG) measured by an oral glucose tolerance test. Safety outcomes were assessed by treatment-emergent adverse events, vital signs, and laboratory measurements, including 24-h urine collections for volume and electrolytes.
For the treatment cohort, the sample size target of 22 patients per treatment group was chosen to allow for the calculation of 95% CI for the primary end point with a half-width of 0.42% for each treatment group, assuming a 1% SD; the half-width of a 95% CI for differences between mean treatment changes was estimated to be 0.59%. The primary efficacy dataset consisted of all randomly assigned patients who took ≥1 dose of double-blind study medication. Analyses of efficacy variables (except change from baseline in insulin dose) excluded data after insulin up-titration. Analyses for change from baseline in A1C, FPG, insulin dose, and total body weight at week 12 (LOCF) were performed using an ANCOVA model with treatment group as effect and baseline value as a covariate. No statistical hypothesis testing was planned for this study designed for exploratory analysis.
Figure 2 shows A1C, FPG, and change from baseline in body weight over time. In the 10- and 20-mg dapagliflozin groups, A1C decreased from baseline to week 12 (LOCF), resulting in differences in mean changes versus placebo of −0.70 and −0.78% (Table 2). At week 12 (LOCF), 65.2% of patients in both dapagliflozin groups achieved a ≥0.5% decrease from baseline A1C versus 15.8% in the placebo group. Five patients (one each in the dapagliflozin 20-mg and placebo groups, and three in the dapagliflozin 10-mg group) showed a therapeutic response defined as A1C <7%. At week 12 (LOCF), mean changes in total body weight were −1.9 kg (placebo), −4.5 kg (10 mg dapagliflozin), and −4.3 kg (20 mg dapagliflozin).
The effect of dapagliflozin on FPG was dose dependent. PPG, measured at 120 min by an oral glucose tolerance test, also showed dose-response characteristics. There was no appreciable change from baseline in TDDI. Four patients in the placebo arm required insulin up-titration, compared with one in the dapagliflozin 10-mg arm and three in the dapagliflozin 20-mg arm.
The placebo group experienced a slight increase in standing blood pressure at week 12, whereas both dapagliflozin groups demonstrated mean improvements in standing systolic and diastolic blood pressure (−7.2 systolic/–1.2 diastolic mmHg [10 mg dapagliflozin] and −6.1 systolic/–3.9 diastolic mmHg [20 mg dapagliflozin]). In the 20-mg dapagliflozin group, supine blood pressure decreased (mean change of −5.5 mmHg systolic/–5.8 mmHg diastolic), whereas there was little or no change in the 10-mg group (supplementary Table 1, available in the online appendix).
Mean changes from baseline in urinary glucose excretion at week 12 were −1.5 g/24 h (placebo), 83.5 g/24 h (10 mg dapagliflozin), and 85.2 g/24 h (20 mg dapagliflozin). Mean 24-h urine output increased from 1,870 to 2,125 ml (placebo), from 1,921 to 2,286 ml (10 mg dapagliflozin), and from 1,809 to 2,253 ml (20 mg dapagliflozin). Compared with baseline, Modification of Diet in Renal Disease–estimated glomerular filtration rates at the end of treatment were normal, with minor changes of −0.58, −0.84, and 1.45 ml/min per 1.73 m2 in the respective placebo and 10- and 20-mg dapagliflozin groups. Generally, there were no remarkable changes from baseline in key laboratory parameters. Median change from baseline in serum uric acid was −0.30 mg/dl in both dapagliflozin groups. There were no marked abnormalities for serum Na+ and liver function tests. Median increases from baseline in serum hematocrit at week 12 were 2.5 and 3.05% in the 10- and 20-mg dapagliflozin groups, respectively.
Adverse events were balanced across all groups (Table 3). Three patients who received placebo, seven who received 10 mg dapagliflozin, and six who received 20 mg dapagliflozin experienced episodes of hypoglycemia. Of these, one patient who received placebo experienced major hypoglycemia. There were no deaths. Two patients, one in the placebo and one in the 20-mg dapagliflozin group, experienced a serious adverse event. One patient in each treatment arm experienced an adverse event that led to discontinuation.
Six patients experienced genital tract infections during the double-blind period; five of these received 20 mg dapagliflozin. One patient in the 20-mg dapagliflozin group reported a urinary tract infection. Events of pollakiuria were reported across all treatment groups, including the placebo group. One patient in each dapagliflozin arm reported polyuria. One case of microalbuminuria in the 20-mg dapagliflozin arm resulted in discontinuation.
One event of renal failure occurred during treatment with 10 mg dapagliflozin. The patient was being chronically treated with multiple antihypertensive agents, including enalapril, carvedilol, and furosemide. Eleven days after starting study medication, the patient was discontinued from the study because of dehydration and prerenal azotemia. Furosemide and enalapril therapy were withheld, and the prerenal azotemia resolved with oral rehydration.
Disease progression in type 2 diabetes is frequently accompanied by a cycle of deteriorating glycemic control due to declining β-cell function. Therapies that depend on insulin supplementation or secretion entail the risk of hypoglycemia, weight gain, decreased insulin sensitivity, and eventual loss of effectiveness. This frustrating clinical setting is exemplified most dramatically by patients with late-stage type 2 diabetes who require escalating insulin doses, often with oral agents such as metformin and/or TZDs to maintain glycemic control. Ultimately, > 25% of patients are treated with insulin-based regimens, often in combination with OADs (6). A novel strategy for controlling glycemia independently of insulin involves limiting glucose reabsorption in the proximal tubule of the kidney, where glucose is reabsorbed via SGLT2 receptors. Dapagliflozin selectively inhibits SGLT2, thereby limiting glucose reabsorption.
Patients recruited for this study had inadequate glycemic control despite aggressive regimens of insulin plus OADs. After reducing the insulin dose by 50%, patients in the placebo arm experienced weight loss, little change in A1C, and a mean 17.8 mg/dl increase in FPG, an outcome that probably reflects the relatively severe insulin resistance in these patients and perhaps improved compliance with diet and lifestyle as a result of study participation. Treatment with dapagliflozin, with its insulin-independent mechanism of action, was associated with additional weight loss of ~2.5 kg and with improvements in glycemic control compared with placebo. Although the total number of hypoglycemic events reported was greater with dapagliflozin than with placebo, there were no major hypoglycemia episodes with dapagliflozin. The effect of dapagliflozin in this insulin-treated population was similar to that observed in treatment-naive diabetic patients (19).
Improvements in glycemic outcome measures were dose dependent, as was the potential safety signal of genital tract infections, more frequently seen in the 20-mg dapagliflozin dose arm. However, the main pharmacodynamic measure, 24-h urinary glucose, increased by ~85 g/day at week 12 in both the 10-mg and 20-mg dapagliflozin groups. A plausible explanation is that 20 mg dapagliflozin may have caused greater glucosuria earlier in the study, as has been seen in other settings (18–20), but that the resulting greater declines in glycemia in the 20-mg dose group led to a lower filtered load of glucose at the kidney, such that by week 12, the point at which glucosuria was measured, the amount of glucose in the urine had equalized between the dapagliflozin dose groups.
Reductions in standing blood pressure in both dapagliflozin groups and in supine blood pressure in the dapagliflozin 20-mg group are noteworthy. The decrease in blood pressure and slight increase in hematocrit are effects consistent with the glucose-induced osmotic diuresis caused by SGLT2 inhibition. A dramatic presentation of this effect was seen in the 10-mg dose arm in an event of dehydration and prerenal azotemia in a volume-sensitive patient. Otherwise, there were no further reports of dizziness or dehydration associated with dapagliflozin in this study. The diuretic property of dapagliflozin warrants further evaluation.
Conclusions that can be drawn from this study are limited by its size and relatively short duration. Nevertheless, these results establish the proof of concept that SGLT2 inhibition can improve glycemic control and weight in patients with diabetes that is poorly controlled with high insulin doses and oral insulin sensitizer therapy, despite a 50% insulin dose reduction. These results further suggest the hypothesis that this therapeutic approach may lend itself to reducing the weight gain that otherwise might occur when insulin therapy is intensified in this population.
This study was funded by Bristol-Myers Squibb and AstraZeneca. J.P.H.W. has received consultancy fees from Bristol-Myers Squibb and AstraZeneca, codevelopers of dapagliflozin; has served on a scientific advisory panel for Bristol-Myers Squibb and AstraZeneca; has received research support and lecture fees from AstraZeneca; and is an investigator for ongoing clinical trials with dapagliflozin. P.N. was a trialist for this study and has performed clinical trials funded by Bristol-Myers Squibb. No other potential conflicts of interest relevant to this article were reported.
Parts of this study were presented in abstract form at the 69th Scientific Sessions of the American Diabetes Association, New Orleans, Louisiana, 5–9 June 2009.
We thank Paul Strumph and Stephanie Moran for their substantial contributions in developing the study design and protocol; Maryse Courval and Dominique Duchesne for their assistance as protocol managers; and the investigators and contributors from each of the study sites. We also thank Alan G. Hempel, Bristol-Myers Squibb, for writing and editorial support, and William Watkins, PAREXEL, for editorial and graphics support.
Clinical trial reg. no. NCT00357370, clinicaltrials.gov.
A complete list of investigators can be found in an online appendix, available at http://care.diabetesjournals.org/cgi/content/full/dc09-0517/DC1.
The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked “advertisement” in accordance with 18 U.S.C. Section 1734 solely to indicate this fact.