Dapagliflozin's Renal Protection Extends to 'Fast Decline' of eGFR

Mitchel L. Zoler, PhD

June 25, 2020

Treatment of patients with type 2 diabetes with the SGLT2 inhibitor dapagliflozin led to a significant drop in the occurrence of 'fast decline' of renal function in more than 15,000 patients enrolled in the drug's main cardiovascular outcome trial, another example of the potent renal protective effects of agents from this drug class.

Among patients with type 2 diabetes enrolled in the DECLARE-TIMI 58 trial, the incidence of a fast decline in renal function, defined as a drop in estimated glomerular filtration rate (eGFR) of at least 3 mL/min per 1.73 m2, was 27% among patients treated with dapagliflozin and 37% in control patients who received placebo, a statistically significant difference for this post-hoc analysis, Itamar Raz, MD, said at the virtual annual scientific sessions of the American Diabetes Association.

This finding, which adds to a long list of other renal function parameters reported to have been improved by treatment with sodium-glucose cotransporter 2 (SGLT2) inhibitors, "emphasizes the value of SGLT2 inhibitors as an important component of both prevention and treatment of chronic kidney disease among patients with type 2 diabetes," said Dr. Raz, a diabetes researcher and professor of medicine at Hadassah University Hospital in Jerusalem.

The primary, prespecified renal outcomes in DECLARE-TIMI 58 were a cardiorenal composite outcome of sustained decline of at least 40% in eGFR to less than 60 mL/min per 1.73 m2, end-stage renal disease (defined as dialysis for at least 90 days, kidney transplantation, or confirmed sustained eGFR of less than 15 mL/min per 1.73 m2), or death from renal or cardiovascular causes; and a second prespecified renal-specific composite outcome that was the same except for excluding death from cardiovascular causes. The results showed that the cardiorenal outcome dropped by a statistically significant 24% with dapagliflozin treatment relative to control patients, and the renal-specific outcome fell by a statistically significant 47% with dapagliflozin relative to control patients (Lancet Diab Endocrinol. 2019 Aug 1;7[8];606-17).

The new findings on the incidence of fast decline in renal function help to further flesh out the scope of renal benefit exerted by SGLT2 inhibitors like dapagliflozin in patients with type 2 diabetes, said experts. Fast decline is a relatively recently devised measure of a high-risk, precipitous loss of renal function that has been defined as a drop of either 3 or 5 mL/min per 1.73 m2 per year (Kidney Int. 2017 Jun;91[6]:1300-11); for this analysis Dr. Raz and his associates used the less stringent definition.

Finding and Treating 'Fast Decliners'

The new report from Dr. Raz "confirms the original [renal] findings and looks to expand them to a particularly high risk group: the fast decliners," commented Robert A. Gabbay, MD, chief science & medical officer of the ADA. "In some ways, the group of patients that we need to find a better treatment for most are those whose GFR declines quickly. We don't always know who they are until after the fact, and studies have been looking for markers that might prospectively identify them," he said in an interview.

The new analysis showed that dapagliflozin "was effective in this subgroup of patients. Furthermore, it didn't matter if they had significant baseline disease or not. Even people with normal kidney function [at baseline] who were still fast decliners fared better with the drug than without it. This suggests that, if it can be confirmed in a prospective study, dapagliflozin might be effective very early in the course of treatment if we can identify who will be the fast decliners."

Dr. Raz and his associates had the data necessary to calculate the rates of eGFR decline during the full follow-up period for 15,012 of the 17,160 patients enrolled in DECLARE-TIMI 58, and they found that 4,788 (32%) were fast decliners and 10,224 had a slower rate of renal deterioration. The average annual decline in eGFR during the period from 6 months after study entry through 4 years was 6.3 mL/min per 1.73 m2 per year (median of 5.1 mL/min per 1.73 m2 per year) among the fast decliners, and zero (median of 0.6 mL/min per 1.73 m2 per year) among the other patients.

Overcoming Dapagliflozin's Initial eGFR Reduction

The researchers focused on the 6-month to 4-year period of treatment as more representative of the impact of dapagliflozin because the SGLT2 inhibitors have an established pattern of triggering an initial, moderate decline in eGFR over roughly the first 6 months on the drug, which is similar to what happens to patients who start treatment with an angiotensin-converting enzyme inhibitor or angiotensin receptor blocker.

"Some patients get as much as a 10% decline in eGFR" when SGLT2 inhibitor treatment starts, but "patients do better over time even with this initial hit," the same way they do on drugs that act on the renin-angiotensin system, explained Silvio E. Inzucchi, MD, an endocrinologist and professor of medicine at Yale University in New Haven who has extensively studied the SGLT2 inhibitors.

The analyses reported by Dr. Raz showed that the protection against fast decline during the 6-month to 4-year period with dapagliflozin treatment was consistent across a range of patient subgroups regardless of age, duration of their type 2 diabetes, their baseline level of hyperglycemia, and their baseline eGFR. Nearly half the patients enrolled in DECLARE-TIMI 58 had an eGFR at baseline of at least 91 mL/min per 1.73 m2 and in this subgroup the incidence of fast decliners was 23% with dapagliflozin and 31% on placebo. Among the 45% of patients who began with an eGFR of 60-90 mL/min per 1.73 m2 the fast-decliner incidence was 32% and 43% when on or off dapagliflozin. Among the 7% of patients who entered with an eGFR below 60 mL/min per 1.73 m2, the fast-decliner incidence was 25% on dapagliflozin and 36% among controls. All the between-group differences were statistically significant.

The incidence of fast decliners was also lower with dapagliflozin treatment when the analysis included the entire first 4 years on treatment, including the first 6 months when SGLT2s usually spikes a loss of renal function. For the entire 4-year period, fast decline occurred among 34% of patients on dapagliflozin and in 37% of control patients, a statistically significant difference.

The mechanisms behind the consistent renal-protective effects of the SGLT2 inhibitors remain unclear right now, but likely seem related to the "perfect" diuretic action the drugs produce, said Dr. Inzucchi. "They're not as hugely effective as diuretics, but they're gentler." While the SGLT2 inhibitors cause a modest amount of fluid loss "for some reason they don't activate the compensatory mechanisms that prevent further reductions in plasma volume," a property that manifests as little or no change in catecholamines or renin-angiotensin activity, which sets this diuretic action apart from what happens with conventional diuretic drugs, he said in an interview.

In DECLARE-TIMI 58 treatment with dapagliflozin met its primary safety outcome of noninferiority to placebo with respect to major adverse cardiovascular events. The results failed to show statistically significant superiority for one of the primary efficacy endpoints, the rate of major adverse coronary events, but they did show significantly better performance for the second primary efficacy outcome of the rate of cardiovascular death or hospitalization for heart failure, which occurred in 4.9% of patients treated with dapagliflozin and in 5.8% of the control patients during a median follow-up of 4.2 years (N Engl J Med. 2019 Jan 24;380[4]:347-57).

DECLARE-TIMI 58 was sponsored by AstraZeneca, the company that markets dapagliflozin (Farxiga). Dr. Raz has been an advisor to and speaker on behalf of AstraZeneca as well as several other companies. Dr. Gabbay had no relevant disclosures. Dr. Inzucchi has been a consultant to AstraZeneca, and also to Abbott, Boehringer Ingelheim, Merck, Novo Nordisk, Sanofi/Lexicon, and vTv Therapeutics.

mzoler@mdedge.com

SOURCE: Raz I et al. ADA 2020, Abstract 303-OR.

This article originally appeared on MDedge.com.

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