View from the NKF-KDOQI Diabetes and Chronic Kidney Disease Work Group

1. View from the NKF-KDOQI Diabetes and Chronic Kidney Disease Work Group Albuminuria as a Surrogate Outcome in Diabetic Kidney Disease: Pitfalls and Opportunities Katherine R. Tuttle, MD, FASN, FACP Medical and Scientific Director Providence Medical Research Center Clinical Professor of Medicine Division of Nephrology University of Washington School of Medicine Spokane and Seattle, Washington USA

2. Historical Perspective on Microalbuminuria as a Predictor of Clinical Outcomes in Diabetes • Early marker of diabetic kidney disease (DKD) in type 1 diabetes • Predictor of cardiovascular disease (CVD) mortality in type 2 diabetes • Death rate increased 100-150% • Most deaths were due to CVD causes Mogensen CE. N Engl J Med 1984;310:356-60

3. Natural History of Diabetic Kidney Disease Onset of Hyperglycemia DIABETES High GFR Low GFR Normal GFR Glomerulosclerosis and Tubulointerstitial Fibrosis Cellular Injury Rising Blood Pressure Hypertension Microalbuminuria Macroalbuminuria Rising Blood Creatinine End-Stage Kidney Disease Cardiovascular Death Diabetes 2 5 10 20 30 Years

4. Annual Rates of Kidney Disease Progression and Death in Type 2 Diabetes (UKPDS) No Kidney Disease D E A T H 1.4% (1.3% to 1.5%) 2.0% (1.9% to 2.2%) Microalbuminuria 0.1% (0.1% to 0.2%) 0.1% (0.0% to 0.1% 3.0% (2.6% to 3.4%) 2.8% (2.5% to 3.2%) Macroalbuminuria 4.6% (3.6% to 5.7%) 2.3% (1.5% to 3.0%) 0.3% (0.1% to 0.4%) Elevated blood creatinine level or kidney replacement therapy 19.2% (14.0% to 24.4%) Adler AI et al. Kidney Int 2003;61:225-232

5. Risks of CVD Death, MI, and Stroke by Quartiles of Albuminuria in Diabetes (LIFE) 4 Unadjusted hazard ratio *Adjusted hazard ratio Hazard Ratio ( 95% CI) 3 2 1 0 <1 1-3 3-12 >12 *Adjusted for: LVH, Framingham risk, treatment Baseline Quartiles of Albuminuria (mg/mmol) Ibsen H et al. Diabetes Care 2006;29:595-600

6. Structural Correlate: Albuminuria and Severity of Angiographic Coronary Artery Disease 50 * 40 31 * Urinary Albumin to Creatinine Ratio (mg/g) 25 30 13 20 10 10 0 Absent Mild Moderate Severe Angiographic Severity Score Tuttle KR et al. Am J Kidney Dis 1999;34:918-925

7. Relationship of Albuminuria and Angiographic Coronary Artery Disease by Diabetes Status † 70 49 60 50 Urinary Albumin to Creatinine Ratio (mg/g) 23 40 ‡ 22 30 20 9 10 0 Present Absent Present Absent Non-Diabetic Patients Type 2 Diabetic Patients Tuttle KR et al.Am J Kidney Dis 1999;34:918-925

8. Degree of Overt Proteinuria Predicts Stroke and CVD Event Rates in Type 2 Diabetes A: U-Prot < 150 mg/L B: U-Prot 150–300 mg/L C: U-Prot > 300 mg/L 1 40 0.9 p <0.001 30 A 0.8 Survival Free of CVD Mortality B 20 0.7 Incidence(%) 0.6 C 10 Overall between-group p<0.001 0.5 0 0 Stroke Coronary events 0 10 20 30 40 50 60 70 80 90 Months Miettinen H et al. Stroke 1996;27:2033-2039

9. Pitfalls of Albuminuria as a Surrogate Outcome: Measurement, Analysis, Interpretation • Intra-patient variability in albuminuria measurement is often large. • Urinary albumin excretion can fluctuate considerably from day-to-day, a particular problem at the low-end range. • Analytic approaches for albuminuria are not standardized. • Relationships between albuminuria and glomerular structure are inconsistent. • Increased levels of urinary albumin are not always present in DKD. • Connection of albuminuria to systemic vascular disease is indirect.

10. How Does the Kidney Reflect Status of the Circulation-at-Large? Glomerular Structure Capillary Loop Mesangial Cell Podocyte Endothelial Cell Afferent Arteriole Efferent Arteriole Juxtaglomerular Apparatus

11. Albuminuria Response to ACE Inhibition Predicts Endothelial and Non-Endothelial-Dependent Vascular Reactivity in Diabetes 18 16.6 16 14 11.4 **10.8 12 With vs. without Microalbuminuria (MA) *p<0.001 **p=0.011 10 Vasodilatory response (%) 8 6 *4.2 4 2 0 1 2 3 4 With MA Without MA With MA Without MA FMD NDD Flow-mediated dilation: FMD Nitroglycerine-dependent dilation: NDD Jawa A. et al. J Clin Endo Metab 2006;91:31-35

12. Pitfalls of Albuminuria as a Surrogate Outcome: Clinical Utility • Transition between albuminuria categories (normo-, micro-, macro-) is not a clinical endpoint. • Data relating albuminuria to chronic kidney disease (CKD) endpoints are limited to observational analyses primarily from studies of renin angiotensin system (RAS) inhibition in patients with type 2 diabetes and macroalbuminuria. • “Masking” phenomenon? • Applicability to other populations (type 1 diabetes, earlier and later CKD stages, normal- or low-level albuminuria) or treatments (novel therapies)? • Albuminuria per se has not been a treatment target in phase 3 trials. • Blood pressure with RAS inhibition • Glycemic control

13. Death, CKD, and CVD Events by Microalbuminuria Status in Type 2 Diabetes (multi-factorial approach) 40 Non-reduction 30 Cumulative incidence (%) 20 10 >50 % reduction 0 0 2 4 6 8 10 Time (years) Araki S et al. Diabetes 2007;56:1727-1730

14. CVD Death, MI, and Stroke by Time-Varying Albuminuria in Type 2 Diabetes (LIFE) 0.36 *<1 mg/mmol (n=274, 408, 311) 1-3 mg/mmol (n=255, 239, 250) 3-12 mg/mmol (n=267, 230, 213) >12 mg/mmol (n=267, 174, 175) 0.24 Proportional Endpoint Rate 0.12 *Baseline, years 2 and 4 0.00 10 20 30 40 50 60 70 Month Ibsen H et al. Diabetes Care 2006;29:595-600

15. Pitfalls of Albuminuria as a Surrogate Outcome: Missing other Prospects? • Failure to reduce albuminuria/proteinuria does not necessarily preclude therapeutic benefit. • Primary reliance on this marker could lead to missed prospects for other effective therapies that work through different pathways or mechanisms.

16. Reduced Protein Diet Decreased ESRD andDeath in Type 1 Diabetic Kidney Disease 30 Usual Protein Diet (1.02 g/kg/d) 20 Cumulative Incidence of ESRD or Death (%) 10 Reduced Protein Diet (0.89 g/kg/d) 0 0 1 2 3 4 Follow-up Time (Years) • Stage 2 CKD (inferred) • 90% on ACEI, good BP control • No difference in albuminuria • Independent of risk factors, CVD Hansen HP et al. Kidney Int 2002;62:220-228

17. Opportunities for Albuminuria as a Surrogate Outcome: Confirm Treatment Target • Interventions that reduce albuminuria are promising as potential therapies for preventing or reducing complications of CKD and associated CVD. • Observational associations raise a strong hypothesis that albuminuria reduction produces clinical benefits. • An alternate explanation is that albuminuria reduction marks patients who are more responsive to treatment. • Clinical trials of therapies targeting albuminuria reduction with clinical endpoints as primary outcomes are necessary to confirm efficacy and safety.

18. Opportunities for Albuminuria as a Surrogate Outcome: Identify Novel Therapies • Novel therapies for DKD are urgently needed to reduce this devastating complication of the worldwide diabetes epidemic. • PKC inhibitors, AGE inhibitors, anti-fibrotic agents • Albuminuria, as well as emerging biomarkers, should be useful for screening potentially effective therapies.

19. Biomarker Discovery: Key Clinical Points • Biological plausibility • Adjudicated clinical endpoints • Doubling of blood creatinine, dialysis, kidney transplant, MI, stroke, death • Verification by test performance characteristics • True positive rate, false positive rate • ROC curve analysis • Generalizable to population of interest • Validated in different clinical groups

20. Process for Connecting Protein Biomarker Discovery with Rigorous Clinical Validation Rifai N et al. Nature Biotechnol 2006;24:971-983