Aliskiren Combined With Losartan in Proteinuric, Non-diabetic Chronic Kidney Disease

Inclusion Criteria: * Male or female 18 - 80 years of age * Presence of nondiabetic CKD stages 3 to 4 as defined by estimated glomerular filtration rate (eGFR by 4-variable MDRD equation) as follows: * Stage 3: Moderate decrease in GFR 30-59 mL/min/1.73 sq.m * Stage 4: Severe decrease in GFR 15-29 mL/min/1.73 sq.m * CKD is defined as either kidney damage or GFR \<60 mL/min/1.73 m2 for \> 3 months with variations of less than 30% in the 3 months before screening * Early-morning urinary protein-to-creatinine ratio of \>500 mg/g or 57 mg/mmol on at least 2 occasions four weeks apart * Patients who are willing to give written, informed consent Exclusion Criteria: * eGFR \< 15 or \> 60 ml/min/1.73m2 * Early-morning urinary protein-to-creatinine ratio of \>5000 mg/g or 570 mg/mmol, or urinary protein-to-creatinine ratio of \<500 mg/g or 57 mg/mmol * Serum K+ \> 5.2 mmol/L * Presence of bilateral renal artery stenosis * Known allergy to losartan or aliskiren * Patients who are receiving angiotensin II receptor blocker / angiotensin converting enzyme inhibitor combination within 12 weeks of randomization * Concurrent treatment with corticosteroids, nonsteroidal antiinflammatory drugs, or immunosuppressive agent * Patients with connective tissue disease or obstructive uropathy * Patients with concomitant malignancy or any such conditions that will severely limit life expectancy * Female who are pregnant or intending to conceive * Female of child-bearing age who are unwilling to practice effective contraception * Patients who are unable to give informed consent * Patients simultaneously participating in another study or who have participated in another study within the last 30 days of entry into this study