A Study of Modified Release RTN-001 In Patients With Uncontrolled Hypertension

Inclusion Criteria:

* Male or female patients age 18 to 75 years, inclusive, at the Screening Visit.
* Uncontrolled HTN despite being on a stable regimen of 2-5 antihypertensive medications.
* Mean BP of ≥135/80 mm Hg.
* Body mass index of 18 to 35 kg/m2.

Exclusion Criteria:

* Mean seated SBP \>175 mm Hg and/or DBP \>110 mm Hg.
* Current or planned use of nitrates and/or alpha-blockers or other drugs known to affect BP during the study period.
* Participants who use PDE5 inhibitors for other indications that cannot or will not refrain from use of PDE5 inhibitors for 7 days before and during their entire period of participation in the study.
* History of hypotension, fainting spells, blackouts or autonomic dysfunction, including orthostatic hypotension.
* Known diagnosis of secondary hypertension (e.g. Cushing's Disease or hyperaldosteronism, renal fibrodysplasia, renal artery stenosis, etc., clinically significant aortic stenosis etc.).
* Recent (within 3 months before the Screening Visit \[Visit S1\]) myocardial infarction; unstable angina leading to hospitalization; uncontrolled, symptomatic atrial fibrillation, or any cardiac arrhythmia that has not been clinically stable for at least 3 months prior to screening. Participants with implantable pacemakers or automatic implantable cardioverter defibrillators may be considered if deemed by the Investigator to be stable for the previous 3 months.
* Uncontrolled hypothyroidism
* Liver disease or dysfunction
* Renal dysfunction (\<45 mL/min/1.73m²) or glomerulonephritis
* Active infection or major illness
* Gastrointestinal conditions or procedures (including weight loss surgery \[eg, Lap-Band or gastric bypass\]) that may affect drug absorption.
* Hematologic or coagulation disorders
* Active malignancy
* Unexplained creatine kinase (CK) \>3 × ULN at any time before randomization
* A known history of temporary or permanent partial or total vision loss
* A known history of "crowded" optic disc.
* A known history of retinitis pigmentosa, a rare genetic eye disease.
* Any prescription or over-the counter drugs or herbal supplements known to be strong inhibitors of CYP3A4 enzymes
* NHYA class III-IV symptoms of heart failure.
* History of diabetes or suspected diabetes with glycosylated hemoglobin \> 10% or fasting glucose \>250 mg/dl at Screening Visit (S1).