Mechanism(s) Underlying Cardiovascular Effects of ARB/NEP Inhibition - Aim 1

After informed consent is obtained, subjects will undergo a screening history and physical
exam, and anti-hypertensive medications will be withdrawn. During this period, blood pressure
(BP) will be measured every one to three days.

After subjects have been off anti-hypertensive medications for three weeks (four for
spironolactone), they will be randomized to four-week treatment with valsartan 160 mg bid (80
mg bid for one week, then 160 mg bid) or LCZ696 200 bid (100 mg bid for one week, then 200 mg
bid) in a double-blind fashion. On the morning of the 28th day of study drug, subjects will
report to the Vanderbilt Clinical Research Center (CRC) after an overnight fast. Subjects
will be studied in the supine position in a temperature-controlled room. They will be
instrumented for intra-arterial infusions. Subjects will be given their last dose of study
drug. One hour after drug administration, we will measure forearm blood flow (FBF) and give
bradykinin, substance P, or BNP. Each peptide will be infused in three graded doses for five
minutes. After administration of all three peptides, subjects will be allowed to rest for an
hour. Then they will be given a single oral dose of sitagliptin 200 mg and be allowed to rest
for 90 minutes. We will repeat baseline measurements and the peptide infusions with an
intervening rest period. The four-week study treatment and protocol will be repeated after a
three-week washout, until participants complete both arms.

Inclusion Criteria:

1. Patients with essential hypertension defined as having

1. untreated, seated systolic blood pressure (SBP) of 130 mmHg or greater on three
separate occasions, or

2. untreated, seated diastolic BP (DBP) of 80 or greater on three separate
occasions, or

3. taken anti-hypertensive agent(s) for a minimum of six months.

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

1. postmenopausal status for at least one year, or

2. status post-surgical sterilization, or

3. if of childbearing potential, utilization of adequate birth control and
willingness to undergo urine beta-human chorionic gonadotropin (hCG) testing
prior to drug treatment and on every study day.

Exclusion Criteria:

1. Presence of secondary form of hypertension

2. Symptomatic hypertension and/or SBP>170 mmHg or DBP>110 mmHg, relevant to the washout
period

3. History of hypersensitivity or allergy to any of the study drugs, drugs of similar
chemical classes, angiotensin-converting enzyme inhibitor (ACEi), ARBs, or NEPi, as
well as known or suspected contraindications to the study drugs

4. History of angioedema

5. History of pancreatitis or known pancreatic lesions

6. History of significant cardiovascular disease (other than essential hypertension and
left ventricular hypertrophy)

7. Symptomatic hypotension and/or a SBP<100 mmHg at screening or <95 mmHg during the
study

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

9. Individuals using oral contraceptives and smokers in order to reduce the risk of
thrombosis following arterial line placement

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

11. Presence of significant pulmonary disorders

12. Type 1 diabetes

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

14. Hematocrit <35%

15. Impaired renal function [estimated glomerular filtration rate (eGFR) of <30
mL/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)

16. Use of hormone-replacement therapy

17. Breast feeding and pregnancy

18. History or presence of immunological or hematological disorders

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

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

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

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

23. 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

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

25. Treatment with lithium salts

26. History of alcohol or drug abuse

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

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

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