Peptide Research
GLP-1 Receptor Agonists and Kidney Disease: What the FLOW Trial Shows
⚠ FOR EDUCATIONAL AND SCIENTIFIC REFERENCE PURPOSES ONLY. THIS ARTICLE SUMMARISES PUBLISHED CLINICAL LITERATURE AND IS NOT MEDICAL ADVICE.
Quick answer: The FLOW trial — the first dedicated kidney outcomes trial for a GLP-1 receptor agonist, published in the New England Journal of Medicine in 2024 — reported a 24% reduction in major kidney disease events with once-weekly semaglutide 1.0 mg versus placebo in adults with type 2 diabetes and chronic kidney disease. The trial was stopped early at a prespecified interim analysis because of clear efficacy. Secondary outcomes included 18% fewer major cardiovascular events and 20% lower all-cause mortality.
Why a Dedicated Kidney Trial Was Needed
Chronic kidney disease affects approximately one in ten people worldwide, and diabetic kidney disease is the leading cause of end-stage kidney disease globally. Published estimates indicate that roughly one in three US adults with diabetes has chronic kidney disease.
Earlier evidence of kidney benefit from GLP-1 receptor agonists came from secondary analyses of cardiovascular outcome trials — informative, but not designed to answer kidney questions. Consequently, FLOW was constructed specifically to test kidney endpoints as the primary outcome.
FLOW: Trial Design
- Registration: NCT03819153, conducted at 387 sites across 28 countries
- Population: 3,533 adults with type 2 diabetes and established CKD (mean eGFR 47 mL/min/1.73 m², median urine albumin-to-creatinine ratio 568 mg/g)
- Randomisation: 1:1 to once-weekly subcutaneous semaglutide 1.0 mg or placebo, both alongside standard of care
- Median follow-up: 3.4 years
- Primary outcome: composite of kidney failure (dialysis, transplantation, or sustained eGFR below 15), persistent ≥50% eGFR reduction from baseline, or death from kidney or cardiovascular causes
Baseline characteristics reflected a high-risk population: mean age 66, 30% women, mean HbA1c approximately 7.8%, mean BMI 32.
Reported Outcomes
| Outcome | Reported Result |
|---|---|
| Primary composite (major kidney events) | 24% risk reduction — 331 vs 410 events; HR 0.76 (95% CI 0.66–0.88), P=0.0003 |
| Event rate | 5.8 vs 7.5 per 100 patient-years |
| Kidney-specific components | HR 0.79 (95% CI 0.66–0.94) |
| Annual eGFR decline | 1.16 mL/min/1.73 m² slower (95% CI 0.86–1.47), P<0.001 |
| Major cardiovascular events | 18% lower |
| Cardiovascular death | 29% lower |
| All-cause mortality | 20% lower |
| Heart failure events | 27% lower (prespecified analysis, JACC) |
Prespecified subgroup analyses reported consistent benefit across baseline eGFR categories and albuminuria strata, including participants with advanced CKD — a population frequently excluded from or underpowered in earlier trials.
The eGFR Slope: An Instructive Detail
One finding deserves specific attention because it illustrates how kidney pharmacology differs from intuition. Published slope analyses describe an initial acute reduction in eGFR in the semaglutide arm, followed by a U-shaped rebound and subsequently a slower long-term decline than placebo.
By week 12, the difference between groups was minimal (−0.03 mL/min/1.73 m²), yet the total slope favoured semaglutide substantially over the full follow-up. This pattern — an early dip preceding long-term preservation — is also documented with other renoprotective agent classes, and it means short-term eGFR movement cannot be interpreted as a proxy for long-term kidney outcomes.
Combination With SGLT2 Inhibitors
Because SGLT2 inhibitors independently reduce kidney and cardiovascular events, whether combining both classes adds benefit was an open question. A prespecified FLOW analysis stratified participants by baseline SGLT2 inhibitor use (550 with, 2,983 without).
In the subgroup not using SGLT2 inhibitors, primary outcome events occurred in 19.5% versus 24.9% (HR 0.73; 95% CI 0.63–0.85). Investigators reported benefit irrespective of baseline SGLT2 inhibitor use, though the smaller size of the concomitant-use subgroup limits precision in that stratum.
Proposed Mechanisms
The magnitude of kidney benefit exceeds what glycaemic control, blood pressure reduction, and weight loss alone would predict. Consequently, published discussion focuses on additional pathways, including anti-inflammatory effects, reduced albuminuria through direct glomerular mechanisms, and attenuation of oxidative stress in renal tissue. Notably, kidney outcomes were also examined in the SELECT trial population — adults with obesity and cardiovascular disease but without diabetes — extending the mechanistic question beyond diabetic kidney disease. The relative contribution of each pathway remains unresolved.
What Remains Unestablished
- Non-diabetic CKD. FLOW enrolled only participants with type 2 diabetes; dedicated trials in non-diabetic CKD have not reported.
- Early stopping. Trials halted for efficacy provide less long-term safety and durability data than trials run to completion.
- Mechanistic attribution. How much benefit is weight-mediated, glycaemia-mediated, or direct renal action has not been quantified.
- Durability after discontinuation. Whether kidney protection persists after cessation has not been studied — connecting to the broader discontinuation literature.
Regulatory Status
The compounds discussed in this article — semaglutide and related receptor agonists — exist as FDA-approved prescription pharmaceutical products, prescribed and monitored by licensed clinicians. This article summarises published clinical literature about those approved products for scientific reference only.
LiveWell Peptides supplies research-grade compounds strictly for in-vitro laboratory research. Research materials are not pharmaceutical products, are not manufactured or approved for clinical use, are not substitutes for any prescription medication, and are not intended for human or animal administration. No comparison to any approved pharmaceutical product is made or implied, and nothing here constitutes guidance about any individual’s medical care.
Frequently Asked Questions
What was the FLOW trial?
FLOW (NCT03819153) was the first dedicated kidney outcomes trial for a GLP-1 receptor agonist — a phase 3, double-blind, placebo-controlled study of 3,533 adults with type 2 diabetes and chronic kidney disease across 387 sites in 28 countries, with a median follow-up of 3.4 years.
What did FLOW report?
A 24% reduction in the primary composite of major kidney disease events (HR 0.76; 95% CI 0.66–0.88; P=0.0003), plus 18% fewer major cardiovascular events, 29% lower cardiovascular death, and 20% lower all-cause mortality. The trial was stopped early for efficacy.
Why did eGFR drop initially?
Slope analyses describe an early acute eGFR reduction followed by a U-shaped rebound and slower long-term decline. This pattern is documented with other renoprotective classes, so short-term eGFR movement is not a reliable proxy for long-term kidney outcomes.
Does benefit extend to patients already on SGLT2 inhibitors?
A prespecified analysis stratified participants by baseline SGLT2 inhibitor use and reported benefit irrespective of that use. However, only 550 participants were using an SGLT2 inhibitor at baseline, which limits precision within that subgroup.
Is the effect explained by weight loss and glucose control?
Published discussion holds that the magnitude exceeds what glycaemic, blood pressure, and weight effects alone would predict, pointing to anti-inflammatory action, direct glomerular mechanisms, and reduced oxidative stress. The relative contributions have not been quantified.
Does this apply to kidney disease without diabetes?
FLOW enrolled only participants with type 2 diabetes. Kidney outcomes were separately examined in the SELECT population — adults with obesity and cardiovascular disease without diabetes — but dedicated trials in non-diabetic CKD have not yet reported.
Related Research
Continue reading: GLP-1 and Liver Disease: MASH Trial Findings · GLP-1 and Sleep Apnea: SURMOUNT-OSA Findings · GLP-1 Discontinuation and Weight Regain
External context: FLOW on ClinicalTrials.gov · PubMed
References
- Perkovic V, Tuttle KR, Rossing P, et al. Effects of semaglutide on chronic kidney disease in patients with type 2 diabetes. N Engl J Med. 2024;391(2):109–121.
- Effects of semaglutide with and without concomitant SGLT2 inhibitor use in participants with type 2 diabetes and chronic kidney disease in the FLOW trial. Nat Med. 2024.
- Effects of semaglutide on heart failure outcomes in diabetes and chronic kidney disease in the FLOW trial. J Am Coll Cardiol. 2024.
- Cardiovascular outcomes with semaglutide by severity of chronic kidney disease in type 2 diabetes: the FLOW trial. Eur Heart J. 2025.
- Kidney and survival outcomes with semaglutide by CKD severity in the FLOW trial. 2026.
- Agarwal R. The FLOW of progress in diabetic kidney disease: semaglutide’s role in combination therapy. Diabetes Care. 2025;48(11):1875–1877.
- Colhoun HM, et al. Long-term kidney outcomes of semaglutide in obesity and cardiovascular disease in the SELECT trial. Nat Med. 2024.
Educational reference only. This article summarises findings from published clinical literature as a scientific reference. It is not medical advice, contains no dosing or treatment guidance, and should not be used to make healthcare decisions. Individuals with questions about kidney disease or prescribed medications should consult a licensed clinician. LiveWell Peptides products are supplied strictly for in-vitro laboratory research, are not pharmaceutical products, and are not for human or animal consumption.