Mechanism(s) Underlying Cardiovascular Effects of ARB/NEP Inhibition - Aim 2

Patients with heart failure (HF) with reduced ejection fraction who qualify for the study
will undergo a three-week run-in period in which any prior angiotensin-converting enzyme
(ACE) inhibitor or angiotensin receptor blocker they were taking will be discontinued and
they will be given valsartan 80 mg bid in a single-blind fashion. After the run-in, subjects
will undergo four study periods in random order. During two study periods they will receive
enalapril 10 mg bid and during two they will receive sacubitril/valsartan (LCZ696) 200 mg bid
for seven days. On the seventh day or each period, subjects will complete a study day in
which they are randomized to receive either the bradykinin B2 receptor blocker icatibant or
placebo intravenously. Each study period will be separated by a three-week washout during
which subjects receive valsartan 80 mg bid.

Inclusion Criteria:

1. Stable patients with a reduced EF

1. EF less than or equal to 40% (confirmed by echocardiogram within the last six
months), and

2. history of symptoms of New York Heart Association class I, II or III HF

3. stable clinical symptoms including no hospitalizations for the last six months

4. treatment with a stable dose of an ACEi or ARB and with a beta blocker (unless
contraindicated or not tolerated) for at least four weeks

5. treatment with a stable dose of an MR antagonist for at least four weeks unless
not possible due to renal function or serum potassium.

2. For female subjects, the following conditions must be met:

1. postmenopausal status for at least one year, or

2. status post-surgical sterilization

Exclusion Criteria:

1. History of hypersensitivity or allergy to any of the study drugs, drugs of similar
chemical classes, ACEi, ARBs, or NEPi, as well as known or suspected contraindications
to the study drugs

2. History of angioedema

3. History of pancreatitis or known pancreatic lesions

4. History of decompensated HF within the last six months (exacerbation of chronic HF
manifested by signs and symptoms that required intravenous therapy or hospitalization)

5. History of heart transplant or on a transplant list or with left ventricular
assistance device

6. Symptomatic hypotension and/or a SBP<100 mmHg at screening or <90 mmHg during the
study

7. Serum potassium >5.2 mmol/L at screening or >5.4 mmol/L during the study

8. Acute coronary syndrome, cardiac, carotid, or other major cardiovascular surgery,
percutaneous coronary intervention, or carotid angioplasty within six months prior to
screening

9. Coronary or carotid artery disease likely to require surgical or percutaneous
intervention within six months of screening

10. History of serious neurologic disease such as cerebral hemorrhage, stroke, seizure, or
transient ischemic attack within six months

11. History of ventricular arrhythmia with syncopal episodes

12. Symptomatic bradycardia or second- or third-degree atrioventricular block without a
pacemaker

13. Presence of hemodynamically significant mitral and/or aortic valve disease, except
mitral regurgitation secondary to LV dilatation

14. Presence of other hemodynamically significant obstructive lesions of the left
ventricular outflow tract, including aortic and subaortic stenosis

15. Type 1 diabetes

16. Poorly controlled type 2 diabetes mellitus (T2DM), defined as a HgbA1c >9%

17. Hematocrit <35%

18. Impaired renal function (eGFR of <30mL/min/1.73 m2) as determined by the four-variable
Modification of Diet in Renal Disease (MDRD) equation, where serum creatinine (Scr) is
expressed in mg/dL and age in years:

eGFR (mL/min/1.73m2)=175 • Scr-1.154 • age-0.203 • (1.212 if Black) • (0.742 if
female)

19. Use of hormone-replacement therapy

20. Breast feeding and pregnancy

21. History or presence of immunological or hematological disorders

22. History of malignancy other than non-melanoma skin cancer

23. Diagnosis of asthma requiring use of inhaled beta agonist more than once a week

24. Clinically significant gastrointestinal impairment that could interfere with drug
absorption

25. Impaired hepatic function [aspartate amino transaminase (AST) and/or alanine amino
transaminase (ALT) >3.0 x upper limit of normal range]

26. Any underlying or acute disease requiring regular medication which could possibly pose
a threat to the subject or make implementation of the protocol or interpretation of
the study results difficult, such as arthritis treated with non-steroidal
anti-inflammatory drugs

27. Treatment with chronic systemic glucocorticoid therapy within the last year

28. Treatment with lithium salts

29. History of alcohol or drug abuse

30. Treatment with any investigational drug in the one month preceding the study

31. Mental conditions rendering the subject unable to understand the nature, scope, and
possible consequences of the study

32. Inability to comply with the protocol, e.g., uncooperative attitude, inability to
return for follow-up visits, and unlikelihood of completing the study