Introduction
Type 2 diabetes mellitus (T2DM) is a progressive disease that often requires combination therapy with antihyperglycemic agents (AHAs) to achieve and maintain glycemic control [
1]. Metformin is the most widely recommended initial monotherapy approach, but some patients are started first with sulfonylureas either for intolerance to metformin or because of physician and/or patient preferences despite the known adverse effects, such as hypoglycemia and weight gain [
1]. As the sulfonylurea glucose-lowering effects are not sustained, many patients fail to achieve individualized glycemic targets and will need additional therapy [
2,
3]. Accordingly, the availability of new agents that can lower blood glucose levels with good safety and tolerability, without increasing hypoglycemia risk and ideally neutralizing the sulfonylurea-induced weight gain, may have significant potential in the future management of the condition.
Canagliflozin is a sodium glucose co-transporter 2 (SGLT2) inhibitor approved in the United States and elsewhere as an adjunct to diet and exercise to improve glycemic control in adults with T2DM [
4‐
17]. Treatment produces significant urinary glucose loss with beneficial effects on glycemic control, body weight, and blood pressure (BP) [
5‐
17]. Small increases in low-density lipoprotein cholesterol (LDL-C) and high-density lipoprotein cholesterol (HDL-C) have been observed, with the ratio remaining unchanged [
5‐
17].
Canagliflozin is not associated with hypoglycemia when used in isolation, although rates may be increased when used in conjunction with insulin or insulin secretagogues [
5‐
17]. The risks of genital mycotic infections and lower urinary tract infections, but not upper urinary tract infections, are elevated with canagliflozin [
18,
19].
This report defines the effects of canagliflozin on indicators of glycemia, safety, and tolerability compared to placebo in a subset of patients who were on background sulfonylurea monotherapy in a prespecified substudy of the CANagliflozin cardioVascular Assessment Study (CANVAS).
Methods
Overall Design of the CANVAS Trial
CANVAS is a randomized, double-blind, placebo-controlled, parallel-group, multi-center trial. A total of 4330 individuals have been randomized to placebo, canagliflozin 100 mg or canagliflozin 300 mg (Janssen Pharmaceuticals, Inc.; Titusville, NJ, USA) [
20].
Objectives and Specific Hypotheses for the Sulfonylurea Substudy
The prespecified CANVAS sulfonylurea substudy was designed to determine the effects of canagliflozin when used in addition to sulfonylurea monotherapy on efficacy, safety, and tolerability in patients with T2DM with inadequate glycemic control at 18 weeks without compromising the masked study design of the entire study cohort. The objectives of the substudy were to assess the changes in glycated hemoglobin (HbA1c) and effects on safety and tolerability with canagliflozin 100 and 300 mg compared to placebo at 18 weeks. A greater reduction in HbA1c with each dose of canagliflozin compared to placebo was the primary hypothesis to be tested.
Secondary objectives of the substudy were to assess the effects of canagliflozin 100 and 300 mg compared to placebo on body weight, fasting plasma glucose (FPG), proportion of participants reaching HbA1c <7.0%, systolic and diastolic BP, fasting plasma lipids (i.e., triglycerides, HDL-C, LDL-C, total cholesterol, and LDL-C to HDL-C ratio) at 18 weeks. Prespecified hypotheses were evaluated for effects on body weight, FPG, proportion of participants reaching HbA1c <7.0%, systolic BP, triglycerides, and HDL-C.
Recruitment
Patient recruitment methods for CANVAS (ClinicalTrials.gov Identifier: NCT01032629) have been previously described [
20].
Participant Inclusion and Exclusion Criteria
Participants in the CANVAS trial are men and women aged ≥30 years with T2DM with inadequate glycemic control (HbA1c ≥7.0% and ≤10.5%) on current antihyperglycemic therapies and at increased risk of cardiovascular disease [
20]. The specific inclusion and exclusion criteria and the overall CANVAS trial design (including screening and run-in procedures, randomization, and follow-up procedures) have been previously published [
20].
The subset included in the sulfonylurea substudy are the participants who were taking minimum or above specified doses of sulfonylurea monotherapy at baseline, specifically glipizide 20 mg, glipizide extended release 10 mg, glyburide/glibenclamide 10 mg, glimepiride 4 mg, gliclazide 160 mg, or gliclazide modified release (MR) 60 mg (i.e., at least half the maximum labeled dose of sulfonylurea).
Background Drug Treatments
Participants were required to have stable background sulfonylurea monotherapy for 8 weeks prior to screening and to continue on the same sulphonylurea dose if at all possible for 18 weeks to allow for the evaluation of short-term effects of canagliflozin on biomarkers while participants were on stable background therapy. Criteria for the initiation of glycemic rescue therapy have been published [
20]. In summary, glycemic rescue therapy was either up-titration of current sulfonylurea or the stepwise addition of non-insulin AHA(s), and then insulin therapies, instituted by investigators using local guidelines for glycemic targets.
Outcomes
The primary efficacy outcome for this substudy was change in HbA1c from baseline to week 18. The secondary efficacy outcomes evaluated at week 18 were body weight, FPG, proportion of participants reaching HbA1c <7.0%, systolic BP, triglycerides, and HDL-C.
Adverse events (AEs), including preidentified AEs of interest (i.e., genital mycotic infections, urinary tract infections, and AEs related to osmotic diuresis and reduced intravascular volume) were recorded. Hypoglycemia episodes were also reported and were defined as biochemically documented (concurrent finger-stick or plasma glucose ≤3.9 mmol/L, irrespective of symptoms) and severe (i.e., requiring the assistance of another individual or resulting in seizure or loss of consciousness).
Statistical Analyses
Efficacy and safety analyses were performed using the modified intent-to-treat population, consisting of all randomized patients who received ≥1 dose of study drug. The last observation carried forward approach was used to impute missing efficacy data. An analysis of covariance model including treatment as a fixed effect and corresponding baseline value as a covariate was used for primary and continuous secondary endpoints. Least squares means and 2-sided 95% confidence intervals (CIs) were calculated for the comparison of each canagliflozin dose versus placebo. A logistic regression model with treatment as a factor and baseline HbA1c as a covariate was used for the analysis of the proportion of patients reaching HbA1c <7.0%. A prespecified, hierarchical testing sequence was used to evaluate the prespecified 18-week hypotheses and estimate P values. For endpoints that were not prespecified for hypothesis testing, point estimates and 95% CIs are provided in lieu of P values. For patients who received rescue therapy, the last post-baseline value prior to the initiation of rescue therapy was used for analysis. Finally, the efficacy analyses were repeated for all CANVAS trial participants who recorded use of any sulfonylurea dose in monotherapy at baseline (data not shown, but conclusions not different). Data for other outcomes remain blinded. Statistical analyses were performed using SAS, version 9.2 (Cary, NC, USA).
Compliance with Ethics
The study is being conducted in accordance with the ethical standards of the responsible committee on human experimentation (institutional and national) and with the Helsinki Declaration of 1964, as revised in 2013, and is consistent with Good Clinical Practice. Regulatory approval for the conduct of the trial was obtained in each country, and ethics approval was received for every site prior to initiation. Informed consent was obtained from all patients included in the CANVAS trial.
Discussion
The addition of canagliflozin to background sulfonylurea monotherapy was efficacious, with further placebo-adjusted decreases of HbA1c of −0.74% and −0.83% for canagliflozin 100 and 300 mg, respectively, at 18 weeks. Furthermore, the reductions in HbA1c were accompanied by a significant decrease in body weight for the 300-mg dose (−1.8%) although not for the 100-mg dose. Canagliflozin 100 mg has been associated with consistent weight loss in other Phase 3 studies [
5‐
17], with significant weight loss observed with canagliflozin 100 mg versus placebo (–1.4%) in the 26-week study as add-on to metformin plus sulfonylurea [
6]. Thus, it seems unlikely that the addition of canagliflozin to the background of a sulfonylurea alone would diminish the extent of weight loss and suggests that the modest reduction in body weight with canagliflozin 100 mg in this study is likely an outlying estimate. Changes in BP, while not significant, were in a similar direction to those observed in other reports [
5‐
17]. Effects on lipid metabolism were also inconsistent and nonsignificant, but the overall pattern appeared to be similar to that reported previously in larger, better powered studies with small increases in LDL-C [
5‐
17]. Importantly, there was no change in the LDL-C/HDL-C ratio with either canagliflozin 300 or 100 mg.
The observed additive glycemic effects of canagliflozin on top of sulfonylurea are anticipated on the basis of its complementary mechanism of action, and while the efficacy of sulfonylurea is dependent on adequate pancreatic insulin-secretory capacity, this is not the case with the SGLT2 inhibitors. For this reason, it is hypothesized that canagliflozin will be an effective treatment choice at most stages of the disease, and in combination with other glucose-lowering therapies. The 300-mg dose of canagliflozin was associated with numerically greater effects on several parameters compared with the 100-mg dose, including a modest increase in the percentage of patients achieving a target HbA1c <7.0% (placebo-subtracted differences of 28.3% vs 20.0%, respectively).
We and others have previously reported that the additional efficacy effects of the 300-mg over the 100-mg dose were achieved at the expense of an increased risk of drug-related AEs [
5‐
17]. By contrast, (almost certainly as the result of the much smaller study numbers), osmotic diuresis-related (e.g., polyuria, pollakiuria, thirst) and volume-related AEs (e.g., postural dizziness, orthostatic hypotension, hypotension, syncope, presyncope) were similar in all treatment groups, with no difference between the 2 canagliflozin doses. We should not, however, conclude that the combination of canagliflozin with a sulfonylurea provides a protective effect against these side effects, and identifying patients potentially susceptible to AEs will be an important component of a patient-centered approach to diabetes management. At the same time, it reinforces the impression that serious adverse effects are relatively uncommon with this compound.
The other AEs observed with canagliflozin were those generally recognized for SGLT2 inhibitors [
21]. Genital mycotic infections were more common with canagliflozin than placebo. As has been reported, they were generally mild or moderate in intensity, were managed with usual therapies, and treatment was continued [
19]. There was no evidence of an increased rate of either upper or lower urinary tract infections, although this is a recognized potential complication with this drug class in larger datasets [
21]. The observed decline in eGFR is likely to be hemodynamic in origin and was not associated with an excess of renal AEs. The small size of the decline in eGFR and the other favorable metabolic effects suggest that the net impact of canagliflozin on renal outcomes is unlikely to be harmful.
The primary weakness of this study is the relatively small sample size. This almost certainly reflects a decrease in the use of sulfonylureas as initial therapy in general, and the small proportion of diabetic patients managed on sulfonylurea monotherapy. As such, the confidence intervals about many estimates are wide, and, while the point estimates of effects sometimes appear different to those reported in prior studies, it is difficult to know whether this reflects real differences in efficacy and safety or chance. In this context, these substudy findings are best interpreted in the context of the broader experience with canagliflozin in this and other patient groups. The conduct of the analyses at 18 weeks provides estimates of short-term effects only, with the long-term impact of canagliflozin in this group remaining to be established.
Acknowledgments
Steering Committee: D. R. Matthews (Co-chair), B. Neal (Co-chair), G. Fulcher, K. Mahaffey, V. Perkovic, G. Meininger, D. de Zeeuw. Independent Data Monitoring Committee: P. Home (Chair), J. Anderson, I. Campbell, J. Lachin, D. Scharfstein, S. Solomon, R. Uzzo. Endpoint Adjudication Committee: G. Fulcher, J. Amerena, C. Chow, G. Figtree, J. French, G. Hillis, B. Jenkins, R. Lindley, B. McGrath, A. Street, J. Watson. The authors thank all investigators, study teams, and patients for participating in this study. The trial is funded by Janssen Research & Development, LLC (Raritan, NJ, USA) and article processing charges were supported by Janssen Global Services, LLC (Raritan, NJ, USA). Technical editorial assistance was provided by Alaina DeToma, PhD, of MedErgy, and was funded by Janssen Global Services, LLC. Canagliflozin has been developed by Janssen Research & Development, LLC, in collaboration with Mitsubishi Tanabe Pharma Corporation. Greg Fulcher contributed to the design and conduct of the study and the interpretation of the data and wrote the first draft of the paper. David R. Matthews, Vlado Perkovic, Dick de Zeeuw, Kenneth W. Mahaffey, Robert Weiss, Julio Rosenstock, and Bruce Neal contributed to the design and conduct of the study and the interpretation of data. George Capuano contributed to the analysis and interpretation of the data. Mehul Desai and Frank Vercruysse contributed to the conduct of the study, and the acquisition and interpretation of data. Wayne Shaw contributed to the design and conduct of the study, and the acquisition of data. Gary Meininger contributed to the design and conduct of the study, and the acquisition, analysis, and interpretation of the data. All authors had full access to all of the data in this study and take complete responsibility for the integrity of the data and accuracy of the data analysis. All named authors meet the ICMJE criteria for authorship for this manuscript, take responsibility for the integrity of the work as a whole, and have given final approval to the version to be published.
Conflict of interest
Greg Fulcher has served on advisory boards for Johnson & Johnson and as a consultant to Janssen.
David R. Matthews has served on advisory boards or as a consultant for Novo Nordisk, GlaxoSmithKline, Novartis, Eli Lilly, Sanofi Aventis, Janssen, and Servier; receives current research support from Janssen and NIHR; and has given lectures for Novo Nordisk, Servier, Sanofi Aventis, Eli Lilly, Novartis, Janssen, and Aché Laboratories.
Vlado Perkovic is supported by a Senior Research Fellowship from the Australian National Health and Medical Research Council; has served on advisory boards and/or spoken at scientific meetings sponsored by Janssen, Baxter, Abbvie, Astellas, Boehringer Ingelheim, AstraZeneca, Merck, and GlaxoSmithKline; and has a policy of honoraria going to his employer.
Dick de Zeeuw has served as a consultant to AbbVie, Astellas, Chemocentryx, Eli Lilly, Fresenius, Janssen, and Merck Darmstadt; all consultancy honoraria are paid to his institution.
Kenneth W. Mahaffey has provided continuing medical education on behalf of, and/or has served as a consultant to the American College of Cardiology, AstraZeneca, Bayer, Boehringer Ingelheim, Bristol-Myers Squibb, Cubist, Eli Lilly, Elsevier, Forest, GlaxoSmithKline, Johnson & Johnson, Medtronic, Merck, Omthera, Portola Pharma, Spring Publishing, The Medicines Company, and WebMD; and has received research support from Medtronic and St. Jude.
Robert Weiss has received research grants from Johnson & Johnson, Boehringer Ingelheim, Sanofi, Amgen, and Pfizer.
Julio Rosenstock has served on scientific advisory boards and received honoraria or consulting fees from companies involved in the development of SGLT2 inhibitors, including Bristol-Myers Squibb, AstraZeneca, Merck, Janssen, Boehringer Ingelheim, and Lexicon; and has received grants/research support from Pfizer, Merck, Janssen, Bristol-Myers Squibb, AstraZeneca, Boehringer Ingelheim, and Lexicon.
Bruce Neal is supported by a National Health and Medical Research Council Senior Research Fellowship; holds a research grant for this study from Janssen and for other large-scale cardiovascular outcome trials from Roche, Servier, and Merck Schering Plough; and has received honoraria or travel support for contributions to the continuing medical education programs of Abbott, Novartis, Pfizer, Roche, and Servier.
George Capuano is a full-time employee of Janssen Research & Development, LLC and a shareholder of Johnson & Johnson.
Mehul Desai is a full-time employee of Janssen Research & Development, LLC.
Wayne Shaw is a full-time employee of Janssen Research & Development, LLC.
Frank Vercruysse is a full-time employee of Janssen Research & Development and a shareholder of Johnson & Johnson.
Gary Meininger is a full-time employee of Janssen Research & Development, LLC and a shareholder of Johnson & Johnson.