Empagliflozin Win in EMPEROR-Preserved HF, but Renal Outcomes Puzzle

Mitchel L. Zoler, PhD

September 01, 2021

The featured report from the 6,000-patient EMPEROR-Preserved trial at the virtual annual congress of the European Society of Cardiology drew lots of attention for its headline finding: the first unequivocal demonstration that a medication, empagliflozin, can significantly reduce the rate of cardiovascular death and hospitalization for heart failure in patients with heart failure with preserved ejection fraction (HFpEF, a left ventricular ejection fraction of more than 40%), with the details simultaneously published online.

But at the same time, the EMPEROR-Preserved investigators released four additional reports with a lot more outcome analyses that also deserve some attention.

The Puzzling Neutral Effect on Renal Events

Perhaps the most surprising and complicated set of findings among the main EMPEROR-Preserved outcomes involved renal outcomes.

The trial's primary outcome was the combined rate of cardiovascular death or hospitalization for heart failure (HHF), and the results showed that treatment with empagliflozin (Jardiance) for a median of 26 months on top of standard treatment for patients with HFpEF led to a significant 21% relative risk reduction, compared with placebo-treated patients.

The trial had two prespecified secondary outcomes. One was the total number of HHF, which dropped by a significant 27%, compared with placebo. The second was the mean change in slope of estimated glomerular filtration rate (eGFR) on an annualized basis, and the empagliflozin regimen reduced the cumulative annual deficit, compared with placebo by an average of 1.36 mL/min per 1.73 m2, a significant difference.

This preservation of renal function was consistent with results from many prior studies of empagliflozin and all of the other U.S.-approved agents from the sodium-glucose cotransporter 2 inhibitor class. Preservation of renal function and a reduction in renal events has become a hallmark property of all agents in the SGLT2 inhibitor class both in patients with type 2 diabetes, as well as in those without diabetes but with heart failure with reduced ejection fraction (HFrEF) or with chronic kidney disease.

EMPEROR-Preserved threw a wrench into what had been an unbroken history of renal protection by SGLT2 inhibitors. That happened when a prespecified endpoint of the study – a composite renal outcome defined as time to first occurrence of chronic dialysis, renal transplantation, a sustained reduction of at least 40% in eGFR, or a sustained drop in eGFR of more than 10 or 15 mL/min per 1.73 m2 from baseline – yielded an unexpected neutral finding.

For this composite renal outcome, EMPEROR-Preserved showed a nonsignificant 5% reduction, compared with placebo, a result that both differed from what had been seen in essentially all the other SGLT2 inhibitor trials that had looked at this, but which also seemed at odds with the observed significant preservation of renal function that seemed substantial enough to produce a clinically meaningful benefit.

Renal Effects Blunted in HFpEF

The immediate upshot was a letter published by several EMPEROR-Preserved investigators that spelled out this discrepancy and came to the jolting conclusion that "eGFR slope analysis has limitations as a surrogate for predicting the effect of drugs on renal outcomes in patients with heart failure."

The same authors, along with some additional associates, also published a second letter that noted a further unexpected twist with the renal outcome: "In prior large-scale clinical trials, the effect of SGLT2 inhibitors on heart failure and renal outcomes had consistently tracked together," they noted, but in this case it didn't, a discordance they said was "extraordinarily puzzling".

This led the study's leaders to reanalyze the renal outcomes using a different definition, one that Milton Packer, MD, who helped design the trial and oversaw several of its analyses, called "a more conventional definition of renal events," during his presentation of these findings at the congress. The researchers swapped out a 40% drop from baseline eGFR as an event and replaced it with a 50% decline, a change designed to screen out less severe, and often transient, reductions in kidney function that have less lasting impact on health. They also added an additional component to the composite endpoint, renal death. A revised analysis using this new renal composite outcome appeared in the European Journal of Heart Failure letter.

This change cut the total number of renal events tallied in the trial nearly in half, down to 112, and showed a more robust decline in renal events with empagliflozin treatment compared with the initial analysis, although the drop remained nonsignificant. The revised analysis also showed that the overall, nonsignificant 22% relative reduction in renal events in patients on empagliflozin, compared with placebo, dwindled down to completely nonexistent in the tertile of patients with a left ventricular ejection fraction of 60% or greater. In this tertile the hazard ratio actually showed a nonsignificant point estimate of a 24% increased rate of renal events on empagliflozin, with the caveat that this subgroup now included a total of just 40 total events between the two treatment arms. (Each of the two other tertiles also had roughly the same number of total events.)

The biggest effect on renal-event reduction was in the tertile of patients with an ejection fraction of 41%-49%, in which empagliflozin treatment was linked with a significant 59% cut in renal events, compared with placebo. The analysis also showed significant heterogeneity in thus outcome between this subgroup and the other two tertiles that had higher ejection fractions and showed reduced rates of protection by empagliflozin against renal events.

This apparent blunting of a renal effect despite preservation of renal function seemed to mimic the blunting of the primary cardiovascular outcome effect that also appeared in patients with ejection fractions in the 60%-65% range or above.

"If we knew what blunted the effect of empagliflozin on heart failure outcomes at higher ejection fraction levels, we think the same explanation may also apply to the blunting of effect on renal outcomes, but right now we do not know the answer to either question," Packer said in an interview. He's suggested that one possibility is that many of the enrolled patients identified as having HFpEF, but with these high ejection fractions may have not actually had HFpEF, and their signs and symptoms may have instead resulted from atrial fibrillation.

"Many patients with an ejection fraction of 60%-65% and above had atrial fibrillation," he noted, with a prevalence at enrollment in this subgroup of about 50%. Atrial fibrillation can cause dyspnea, a hallmark symptom leading to diagnosis of heart failure, and it also increases levels of N-terminal of the prohormone brain natriuretic peptide, a metric that served as a gatekeeper for entry into the trial. "Essentially, we are saying that many of the criteria that we specified to ensure that patients had heart failure probably did not work very well in patients with an ejection fraction of 65% or greater," said Packer, a cardiologist at Baylor University Medical Center in Dallas. "We need to figure out who these patients are."

Some experts not involved with the study voiced skepticism that the renal findings reflected a real issue.

"I'm quite optimistic that in the long-term the effect on eGFR will translate into renal protection," said Rudolf A. de Boer, MD, PhD, a professor of translational cardiology at University Medical Center Groningen (the Netherlands), and designated discussant at the congress for the presentation by Packer.

John J.V. McMurray, MD, a professor of cardiology and a heart failure specialist at Glasgow University, speculated that the unexpected renal outcomes data may relate to the initial decline in renal function produced by treatment with SGLT2 inhibitors despite their longer-term enhancement of renal protection.

"If you use a treatment that protects the kidneys in the long-term but causes an initial dip in eGFR, more patients receiving that treatment will have an early 'event,' " he noted in an interview. He also cautioned about the dangers of subgroup analyses that dice the study population into small cohorts.

"Trials are powered to look at the effect of treatment in the overall population. Everything else is exploratory, underpowered, and subject to the play of chance," McMurray stressed.

Counting Additional Cardiovascular Disease Events Allows More Analyses

A third auxiliary report from the EMPEROR-Preserved investigators performed several prespecified analyses that depended on adding additional cardiovascular disease endpoints to the core tallies of cardiovascular death or HHF – such as emergent, urgent, and outpatient events that reflected worsening heart failure – and also included information on diuretic and vasopressor use because of worsening heart failure. The increased event numbers allowed the researchers to perform 30 additional analyses included in this report, according to the count kept by Packer who was the lead author.

He highlighted several of the additional results in this paper that documented benefits from empagliflozin treatment, compared with placebo:

  • A significant 29% reduction in the need for admission to a cardiac care unit or intensive care unit during an HHF.

  • A nonsignificant 33% reduction in the need for intravenous vasopressors or positive inotropic drugs during HHF.

  • A significantly increased rate of patients achieving a higher New York Heart Association functional class. For example, after the first year of treatment patients who received empagliflozin had a 37% higher rate of functional class improvement, compared with patients who received placebo.

McMurray had his own list of key takeaways from this paper, including:

  • Among patients who needed hospitalization, "those treated with empagliflozin were less sick than those in the placebo group."

  • In addition to reducing HHF empagliflozin treatment also reduced episodes of outpatient worsening as reflected by their receipt of intensified diuretic treatment, which occurred a significant 27% less often, compared with patients on placebo.

  • Treatment with empagliflozin was also linked with a significant 39% relative reduction in emergency or urgent-care visits that required intravenous therapy.

Empagliflozin's Performance Relative to Sacubitril/Valsartan

The fourth additional report focused on a post hoc, cross-trial comparison of the results from EMPEROR-Preserved and from another recent trial that, like EMPEROR-Preserved, assessed in patients with HFpEF a drug previously proven to work quite well in patients with HFrEF. The comparator drug was sacubitril/valsartan (Entresto), which underwent testing in patients with HFpEF in the PARAGON-HF trial.

The primary outcome of PARAGON-HF, which randomized 4,822 patients, was reduction in cardiovascular death and in total HHF. This dropped by a relative 13%, compared with placebo, during a median of 35 months, a between-group difference that came close to but did not achieve significance (P = .06). Despite this limitation, the Food and Drug Administration in February 2021 loosened the indication for using sacubitril/valsartan in patients with heart failure and a "below normal" ejection fraction, a category that can include many patients considered to have HFpEF.

Although the researchers who ran this analysis, including Packer, who was the first author, admitted that "comparison of effect sizes across trials is fraught with difficulties," they nonetheless concluded from their analysis that "for all outcomes that included HHF the effect size was larger for empagliflozin than for sacubitril/valsartan."

McMurray, a lead instigator for PARAGON-HF, said there was little to take away from this analysis.

"The patient populations were different, and sacubitril/valsartan was compared against an active therapy, valsartan," while in EMPEROR-Preserved empagliflozin compared against placebo. "Most of us believe that sacubitril/valsartan and SGLT2 inhibitors work in different but complementary ways, and their benefits are additive. You would want patients with HFpEF or HFrEF to take both," he said in an interview.

Packer agreed with that approach and added that he would probably also prescribe a third agent, spironolactone, for many patients with HFpEF.

EMPEROR-Preserved was sponsored by Boehringer Ingelheim and Eli Lilly, which jointly market empagliflozin (Jardiance). PARAGON-HF was sponsored by Novartis, which markets sacubitril/valsartan (Entresto). Packer has received consulting fees from Boehringer Ingelheim and from numerous other companies. de Boer has research contracts with Boehringer Ingelheim as well as from Abbott, AstraZeneca, Cardior, Ionis, Novo Nordisk, and Roche, and he has been a consultant to Novartis as well as to Abbott, AstraZeneca, Gayer, and Roche. McMurray led trials of sacubitril/valsartan sponsored by Novartis, and his institution has received compensation for his participation in studies sponsored by Abbvie, AstraZeneca, Cardurion, DalCor, GlaxoSmithKline, Pfizer, and Theracos.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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