Iodinated contrast media have been causally linked to acute kidney injury known as contrast-induced nephropathy (CIN), which is the consequence of CM-induced local renal ischemia and direct toxic effects. Conestat alfa (recombinant human C1 esterase inhibitor) has been shown to decrease renal ischemic damage in experimental models of renal ischemia.

The Recombinant Human C1 Esterase Inhibitor in the Prevention of Contrast-induced Nephropathy in High-risk Subjects (PROTECT) Study is a randomized, placebo-controlled, double-blind single-center trial that will assess the effect of prophylactic administration of Conestat alfa on the degree of acute kidney injury subjects undergoing elective coronary angiography. Patient with an estimated glomerular filtration rate <=50 ml/min/1.73 m2 and at least one additional risk factor for CIN will be enrolled and randomly assigned to 1) Conestat alfa at 50 U/kg given as intravenous injection immediately before and 4 hours after coronary angiography or 2) placebo (sodium chloride). All patients will receive standard intravenous hydration with isotonic saline. Surrogate markers of kidney injury will be assessed over a 48 hours time period. Patients will be followed for cardiovascular and renal events over 12 weeks.

The primary outcome measure is peak change in urinary Neutrophil gelatinase-associated lipocalin within 48 hours after elective coronary angiography.

Iodinated contrast media (CM) are an essential component of contemporary imaging and interventional studies. Although CM are generally well tolerated, they have been causally linked to acute kidney injury known as contrast-induced nephropathy (CIN), the third leading cause of acute kidney injury in hospitalized patients. Preexisting renal impairment, diabetes mellitus, advanced age, congestive heart failure, or large volumes and repeated use of CM have been identified as risk factors for CIN. CIN is the consequence of CM-induced local renal ischemia in combination with direct toxic effects to renal tubular cells. Subsequent inflammation may cause further tissue damage in the reperfusion period. Apart from intravenous hydration preventive strategies for CIN are lacking.

The complement system consists of several circulating proteins that are implicated in the first-line defence against pathogens and in the removal of dying cells. Following renal ischemia activation of the lectin pathway of complement in particular has been associated with local tissue damage in the kidney. Conestat alfa is a recombinant human C1 esterase inhibitor, which inhibits activation of the complement system and is licensed in Europe and USA for the treatment of a hereditary condition (hereditary angioedema). Conestat alfa markedly reduced tissue damage in experimental models of renal ischemia and reperfusion injury, but has not been investigated in human ischemia.

The Recombinant Human C1 Esterase Inhibitor in the Prevention of Contrast-induced Nephropathy in High-risk Subjects (PROTECT) Study is a randomized, placebo-controlled, double-blind single-center trial that will assess the effect of prophylactic administration of Conestat alfa on the degree of acute kidney injury subjects undergoing elective coronary angiography. Patient with an estimated glomerular filtration rate <=50 ml/min/1.73 m2 and at least one additional risk factor for CIN will be enrolled and randomly assigned to 1) Conestat alfa at 50 U/kg given as intravenous injection immediately before and 4 hours after coronary angiography or 2) placebo (sodium chloride). All patients will receive standard intravenous hydration with isotonic saline. Surrogate markers of kidney injury including serum creatinine and cystatin C and urinary Neutrophil gelatinase-associated lipocalin and TIMP2 * Insulin-like growth factor-binding protein 7 (IGFBP7) will be assessed over a 48 hours time period. In addition, increases in troponin T, a marker of cardiac damage, will be assessed. Patients will be followed for thromboembolic, anaphylactic and a composite endpoint of cardiovascular and renal events over a 12 week period.

The primary outcome measure is peak change in urinary Neutrophil gelatinase-associated lipocalin within 48 hours after elective coronary angiography.

Total hydration and contrast media volume will be recorded. Serum C1 esterase inhibitor levels immediately before and 10 minutes after administration of Conestat alfa or placebo will be assessed.

Inclusion Criteria:

• Estimated glomerular filtration rate (eGFR) of <50 ml/min/1.73m2
• At least one of the following risk factors: diabetes mellitus, age at least 75 years, anemia (baseline hematocrit value less or equal 39% for men and less or equal 36% for women), congestive heart failure class III or IV by New York Heart Association classification, history of pulmonary edema.

Exclusion Criteria:

• Contraindications to the class of drugs under study (C1 esterase inhibitors), e.g. known hypersensitivity or allergy to class of drugs or the investigational product
• History of allergy to rabbits
• Current treatment with N-acetylcysteine, sodium bicarbonate, fenoldopam, mannitol (not applicable to mannitol serving as excipient in other medical drugs), dopamine or theophylline
• Women who are pregnant or breast feeding
• Multiple myeloma
• Acute decompensated heart failure (requiring hospital admission and treatment with supplemental oxygen, diuretics and/or vasodilator therapy) within two weeks prior to the date of coronary angiography
• Acute myocardial infarction (ST elevation or non-ST elevation myocardial infarction) within two weeks prior to the date of coronary angiography
• Dialysis
• Exposure to iodinated contrast media within seven days prior to the date of coronary angiography.
• Participation in another study with investigational drug within the 30 days preceding and during the present study
• Previous enrolment into the current study
• Enrolment of the investigators and their family members