Imbalance in glycemic control between the treatment and placebo groups in cardiovascular outcome trials in type 2 diabetes

Differences in glycemic control between the treatment arms in cardiovascular outcome trials of type 2 diabetes medications do not explain cardiovascular benefits

Hyperglycemia is an undisputed epidemiological risk factor for microvascular complications in both type 1 and type 2 diabetes, integral in their causal pathways. Importantly, interventions that reduce the hyperglycemic burden in patients with either type of diabetes reduce the risk of microvascular complications (e.g., retinopathy, nephropathy, neuropathy). Hence, for microvascular risk, hyperglycemia is a proven risk factor and a proven treatment target, as reflected by treatment recommendations and guidelines across most scientific societies world-wide. However, although reducing the hyperglycemic burden to reduce microvascular risk remains a cornerstone of care for patients with type 2 diabetes, this therapeutic imperative does not apply to cardiovascular risk mitigation. This latter aspect is important in the context of interpreting therapeutic impact of treating hyperglycemia on risk for macrovascular complications in patients with type 2 diabetes. This letter, in response to a previous paper, discuss how modest differential glucose control contribute little if anything to the results observed of contemporary cardiovascular outcome trials in type 2 diabetes.

Approvals of type 2 diabetes drugs tested in cardiovascular outcome trials: A tripartite comparison

AIMS

In 2008, the US Food and Drug Administration (FDA) issued a guidance requiring that cardiovascular outcome trials (CVOTs) be conducted for newer hypoglycaemic drugs for type 2 diabetes (T2D). We aimed to examine the decisions by 3 regulatory authorities in response to identical CVOT data.

METHODS

We surveyed ClinicalTrials.gov to identify CVOTs and examined the revision histories of drug labels in databases from the FDA, the European Medicines Agency, and the Pharmaceuticals and Medical Devices Agency in Japan.

RESULTS

We selected 14 drugs and corresponding CVOTs, 12 of which were conducted as postmarketing trials. In the USA and the EU, the pre-CVOT indication on all 14 labels was "improvement in glycaemic control". Six drugs showed significant cardiovascular risk reduction, which led to an additional indication regarding reduction of cardiovascular adverse events in the USA, and a change to the EU indication to specify treatment of adults with T2D. The initial indication in Japan, T2D, remained unchanged. Regarding safety, significant increases in heart failure were observed only in the saxagliptin trial. A warning was added to the saxagliptin labels in the EU and Japan, whereas the FDA required a class effect warning to be added to the labels of all 4 dipeptidyl peptidase-4 inhibitors.

CONCLUSIONS

Regulatory authorities using identical trial data made substantially different decisions regarding both safety and efficacy of hypoglycaemic drugs. The differences in initial indication wording between Japan and the other authorities suggest that trial data and T2D are interpreted differently in these regions.

Cardiovascular protection with sodium-glucose co-transporter-2 inhibitors in type 2 diabetes: Does it apply to all patients?

Patients with type 2 diabetes (T2D) are at an increased risk of cardiovascular disease (CVD). Cardiovascular risk in these patients should be considered as a continuum, and comprehensive treatment strategies should aim to target multiple disease risk factors. Large-scale clinical trials of sodium-glucose co-transporter-2 (SGLT2) inhibitors have shown an impact on cardiovascular outcomes, including heart failure hospitalization and cardiovascular death, which appears to be independent of their glucose-lowering efficacy. Reductions in major cardiovascular events appear to be greatest in patients with established CVD, particularly those with prior myocardial infarction, but are independent of heart failure or renal risk. Most large-scale trials of SGLT2 inhibitors predominantly include patients with T2D with pre-existing CVD and high cardiovascular risk at baseline, limiting their applicability to patients typically observed in clinical practice. Real-world evidence from observational studies suggests that there might also be beneficial effects of SGLT2 inhibitors on heart failure hospitalization and all-cause mortality in various cohorts of lower risk patients. The most common adverse events reported in clinical and observational studies are genital infections; however, the overall risk of these events appears to be low and easily managed. Similar safety profiles have been reported for elderly and younger patients. There is still some debate regarding the safety of canagliflozin in patients at high risk of fracture and amputation. Outstanding questions include specific patterns of cardiovascular protection according to baseline risk.