Mitchel L. Zoler, PhD
October 28, 2021
Agents that form the sodium-glucose cotransporter 2 inhibitor class – including canagliflozin (Invokana), dapagliflozin (Farxiga), and empagliflozin (Jardiance) – have show remarkably consistent cardiovascular efficacy and safety for treating patients with heart failure, chronic kidney disease, and higher-risk patients with type 2 diabetes.
But despite an essential role now established for drugs in the SGLT2 inhibitor class for patients with heart failure with reduced ejection fraction, progressive renal dysfunction, or – most recently – patients with heart failure with preserved ejection fraction, the scope may be less clear when using these agents in patients with type 2 diabetes because they fall across a broad spectrum of risk for cardiorenal disease.
"What makes patients with type 2 diabetes distinct from other patients in whom SGLT2 inhibitors have been studied, such as patients with heart failure, is that they have a much wider spectrum of risk. Low-risk patients with type 2 diabetes were not included in the SGLT2 inhibitor trials. Defining risk in patients with type 2 diabetes has the potential to inform prioritization" for treatment with an SGLT2 inhibitor, explained David D. Berg, MD, who has led one effort to develop risk scores that can risk-stratify patients with type 2 diabetes based on their vulnerability to incident heart failure and hospitalization for these episodes.
The hefty cost for these drugs, with retail prices that run over $6,000 annually for the most widely used and most potent agents in the class, has spurred researchers to try to find cost-effective ways to identify patients with type 2 diabetes who stand to benefit most from taking an SGLT2 inhibitor.
'Cost Must Be Considered'
"Cost must be considered, and at this point it's probably more responsible on a societal level to advise using SGLT2 inhibitors mainly in patients [with type 2 diabetes] with compelling indications," said Silvio Inzucchi, MD, professor and director of the Yale Medicine Diabetes Center in New Haven, Conn. Inzucchi added, however, that "I can easily foresee a day when these agents are considered foundational therapy for all patients with type 2 diabetes, after they go generic and cost is not a major issue. I'm starting to lean toward this very simplified approach, but the costs are prohibitive at this time."
"If the SGLT2 inhibitors were available at a low cost, I'd argue that they should be used in all patients with type 2 diabetes who have no contraindications or tolerability issues; but we live in a world where they are not yet low cost," agreed Mikhail N. Kosiborod, MD, a cardiologist and codirector of the Cardiometabolic Center of Excellence at Saint Luke's Mid-America Heart Institute in Kansas City, Mo.
"We can't give SGLT2 inhibitors to everyone with type 2 diabetes right now because that would be too costly; these agents are so expensive. You start by targeting the patients with the highest risk" for incident heart failure, said Ambarish Pandey, MD, a cardiologist at the University of Texas Southwestern Medical Center, Dallas.
The spotlight the SGLT2 inhibitor class has received, based on its unexpectedly potent efficacy in cutting rates of acute heart failure episodes in patients with type 2 diabetes, has also sharply raised the profile of this complication of type 2 diabetes, an outcome that until recently many clinicians had largely ignored, overshadowed by a focus on adverse outcomes from atherosclerotic cardiovascular disease such as MIs and strokes.
"Results from the SGLT2 inhibitor trials have reignited interest in the relationship between type 2 diabetes and heart failure and have started to shift the mindset of clinicians toward thinking about reducing both atherothrombotic risk and heart failure risk in patients with type 2 diabetes," said Berg, a cardiologist at Brigham and Women's Hospital in Boston.
"Prior to the SGLT2 inhibitor trials, heart failure was on the radar of diabetes clinicians only as something to watch for as a potential side effect of certain glucose-lowering therapies. Now that there are therapies that can lower heart failure hospitalization, it's made us think more about heart failure, how common it is in patients with type 2 diabetes, and what can we do to lower this risk," commented Alice Y.Y. Cheng, MD, a diabetes specialist at the University of Toronto.
Banking on Biomarkers
Risk scores for assessing the likelihood of people developing incident heart failure date back more than a decade. More recent efforts have focused on patients with type 2 diabetes, starting with scores that relied entirely on clinical markers of risk such as prior heart failure, established coronary artery disease, and chronic kidney disease. Reports of two of these validated scores appeared in 2019, one from a team led by Berg and associates in 2019, and a second score developed by Pandey and associates.
More recently, both research teams behind these two scores validated newer versions that further refined assessment of patients with diabetes by including biomarkers of incipient heart failure, such as N-terminal of the prohormone brain natriuretic peptide (NT-proBNP). The UT Southwestern group's biomarker-based score relies on levels of NT-proBNP as well as on levels of high sensitivity troponin T (hsTnT) and C-reactive protein, plus ECG-based assessment of left ventricular hypertrophy to assess risk for incident heart failure. Developers reported in 2021 that this biomarker score could account for 74% (C-statistic) of the 5-year risk for heart failure among patients with diabetes.
The biomarker-based score devised by Berg and associates, relies on NT-proBNP, hsTnT, and a history of heart failure to predict the risk for a future hospitalization for heart failure. They reported in Diabetes Care that in validation testing this score accounted for 84% of the risk.
"I'm hopeful that both our original clinically-based risk score and our new biomarker-based score will be endorsed by professional society guidelines. The intent of the biomarker-based score is not to replace the clinical one," Berg stressed in an interview. But he acknowledged that it uses biomarker values that currently are not routinely collected in U.S. practice. Biomarkers like NT-proBNP "are highly associated with future heart failure risk, but are not yet routinely assessed," he said. Because of this, "widespread adoption of the [biomarker] risk tool will require some education."
It may also require some sort of preliminary screening to determine the appropriateness of using it in a specific patient because of the relative expense of a test for NT-proBNP.
A Texas Two-Step Process
"We can't perform a [NT-proBNP] test on every patient with type 2 diabetes because cost is a huge barrier," with a U.K. price of roughly £28 (about $40) per test, commented Naveed Sattar, MD, PhD, professor of metabolic medicine at the University of Glasgow. "NT-proBNP is the best biomarker by far to predict risk" for heart failure," but "it's too expensive. It's not going to happen in everyone," he said in an interview. He suggested taking a two-step approach to identify patients to test for NT-proBNP based on clinical measures like blood pressure, weight and height, lipid levels and renal function and the presence of suggestive symptoms like dyspnea, fatigue, and peripheral edema, an argument he recently spelled out in detail in an editorial he coauthored.
"More work is needed to define which patients would usefully have cardiac biomarkers measured," Sattar wrote with his associate.
Two-step is the approach used in routine practice by clinicians at UT Southwestern Medical Center. "We screen all patients with type 2 diabetes and no diagnosed heart failure who are not already on an SGLT2 inhibitor" using their 2019 screening tool, called the WATCH-DM Risk score, said Pandey. Patients flagged at high risk by their clinical score receive an SGLT2 inhibitor (presuming no contraindications). The remaining patients with low or intermediate risk may then undergo biomarker-based assessment to find additional patients who warrant SGLT2 inhibitor treatment, he said in an interview.
Often, a record of the most important biomarker, NT-proBNP, is already in the patient's record and less than a year old, in which case clinicians use that value. An NT-proBNP level of at least 125 pg/mL indicates increased risk in people with a body mass index of less than 30 kg/m2, while for those with higher body mass indexes clinicians at Southwestern apply a threshold for higher risk of at least 100 pg/mL.
In addition to starting those patients on an SGLT2 inhibitor, the Southwestern protocol calls for intensified efforts at weight loss and improved fitness to further lower incident heart failure risk, and they are also considering targeting treatment with a glucagonlike peptide–1 receptor agonist to these patients as well. They have a research protocol in place, called WATCH-DM, that will prospectively assess the efficacy of this strategy.
Despite the cost, others also believe that the time is right for biomarker-based tests to boost access to the benefits that treatment with SGLT2 inhibitors can give patients with type 2 diabetes.
"In theory it's reasonable" to use a risk score like the recent one reported by Berg and coauthors, said Vanita R. Aroda, MD, an endocrinologist and director of diabetes clinical research at Brigham and Women's Hospital in Boston. "We need to pay attention to heart failure as an outcome and use risk stratification" to decide which patients with type 2 diabetes but without established cardiovascular disease warrant treatment with an SGLT2 inhibitor, she said in an interview. "Given the data, we need more concrete recommendations" from medical societies on how to reasonably use biomarkers and imaging to identify patients with type 2 diabetes who are at increased risk for heart failure and hence would benefit from treatment. "This should be of high interest to guidelines committees," she added.
The earlier version of Berg's score, based exclusively on clinical observations and conventional measures like estimated glomerular filtration rate and urinary creatinine to albumin ratio, had overlap with established criteria for starting treatment with an SGLT2 inhibitor, such as the presence of chronic kidney disease, she noted. "A biomarker-based score may provide the additional level of discrimination needed to characterize risk and potential benefit."
Asymptomatic Diabetic Cardiomyopathy
Aroda and several coauthors recently published a review that describes a subset of patients with type 2 diabetes who might get picked up by intensified screening for heart failure risk: those with asymptomatic diabetic cardiomyopathy, a clinical state that they said represents patients with stage B heart failure based on the new Universal Definition and Classification of Heart Failure. Until recently, these patients with type 2 diabetes and asymptomatic cardiomyopathy have mostly gone unrecognized.
A recent report from Pandey and associates reviewed records from 2,900 U.S. patients with diabetes and no symptoms who had been included in any of three cohort studies and found echocardiographic evidence of early-stage cardiomyopathy in as many as two-thirds. In an editorial about this report, Aroda and coauthors called these patients a potential "window of opportunity for prevention and treatment of heart failure."
"There is evidence of structural cardiac changes that progress through the stages of heart failure," and starting treatment with an SGLT2 inhibitor during an earlier stage can potentially slow or prevent this progression and thereby limit future functional decline, Aroda said.
Sattar agreed. Type 2 diabetes appears to help cause "fluid derangements" and abnormal hemodynamics that produces cardiac stress, changes in heart structure, and adverse remodeling of the heart, a process that "some call cardiomyopathy," which is exacerbated by other pathologic forces that are also often present in these patients such as obesity and hypertension. SGLT2 inhibitors can help these patients by producing "reverse remodeling of the heart."
"This process was neglected because for many years our focus was on ischemic heart disease in patients with type 2 diabetes. It was there in plain sight, but we were missing it," explained Sattar. Having agents from the SGLT2 inhibitor class "has allowed us to better understand this mechanism."
The SGLT2 inhibitors are "absolutely the driving reason" why the diabetes–heart failure link has become so important, said Inzucchi. Having drugs that reduce heart failure risk provided clinicians with a tool that has "changed our mindset."
"Heart failure prevention has been largely neglected in patients with type 2 diabetes. Reprioritizing heart failure prevention to first and foremost among patients with type 2 diabetes is long overdue," commented Gregg C. Fonarow, MD, professor and chief of cardiology at the University of California, Los Angeles.
Clinicians Don't Like Risk Scores
Will systematic screening for heart failure risk in selected patients with type 2 diabetes take hold, and with it expanded and better-targeted use of SGLT2 inhibitors?
"I hope so," said Kosiborod, but one challenge is that "for the most part clinicians don't like using risk scores." Only a few have ever been widely incorporated into practice; mostly they become tools for research. Plus, SGLT2 inhibitor uptake has in general been slow to catch on, which Kosiborod blames primarily on clinical inertia, a pervasive issue that has also hampered optimal use of drugs as commonplace as statins, ACE inhibitors, and angiotensin-receptor blockers.
"Given the avalanche of positive data, uptake of SGLT2 inhibitors will continue to improve and accelerate; but unfortunately, unless something dramatic happens we'll likely see their continued underuse for several more years," he predicted. "Designing better systems of care that prioritize prevention are absolutely needed to improve implementation of effective therapies, including SGLT2 inhibitors."
Despite their underuse the SGLT2 inhibitor class has, in just 6 years since results from the EMPA-REG OUTCOME trial came out and launched the current treatment era, transformed thinking about the risk that heart failure poses to patients with type 2 diabetes and the need to manage this risk.
"I thank the SGLT2 inhibitors for raising awareness of heart failure risk in patients with diabetes," and for giving clinicians a new way to mitigate this risk, said Cheng.
Berg has been a consultant to AstraZeneca, and received research grant support to his institution from AstraZeneca and Pfizer. Cheng has received personal fees from multiple pharmaceutical companies. Kosiborod has been an adviser and consultant to multiple pharmaceutical companies; has received research grants from AstraZeneca and Boehringer Ingelheim; and has received other research support from AstraZeneca. Pandey has been an adviser to Roche Diagnostics; has received nonfinancial support from Pfizer and Merck; and has received research support from Gilead Sciences, Myovista, and Applied Therapeutics. Sattar has received consulting honoraria from multiple pharmaceutical companies, and has received grant support from Boehringer Ingelheim, Roche Diagnostics, and Novartis. Aroda has been a consultant for several pharmaceutical companies; has a spouse employed with Janssen; and has received research support (institutional contracts) from multiple pharmaceutical companies. Fonarow has been a consultant to several pharmaceutical companies.
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