An Efficacy, Safety, Tolerability and Dose Finding Study of XXB750 in Resistant Hypertension Patients.

Inclusion Criteria: 1. Male and female participants who are ≥ 18 years old. 2. Signed informed consent prior to participation in the study. 3. Apparent rHTN at screening (Visit 1) defined as uncontrolled BP with an office msSBP ≥ 140 mmHg despite treatment with stable (i.e., unchanged for ≥4 weeks), optimal or maximally tolerated doses of three or four antihypertensive drugs of different classes, including an ACEI/ARB, a long-acting dihydropyridine CCB, and a thiazide or thiazide-like diuretic. Participant with documented intolerance to any doses of CCBs may be eligible if receiving another class of antihypertensive medication at an optimal or maximally tolerated dose (referred to as triple background antihypertensive therapy. An optimal dose is defined as the highest dose taking in to account participant's documented comorbidities and tolerability per investigator's clinical judgment. 4. Mean 24hr SBP ≥135 mmHg (measured by ABPM) at the end-of Run-in-Visit (Visit 30) on treatment with optimal or maximally tolerated doses of an ACEI/ARB, a long-acting dihydropyridine CCB (or a suitable alternative in case of intolerance per inclusion criterion above), and a thiazide or thiazide-like diuretic. Exclusion Criteria: 1. Subjects with the following blood pressures at the specified time points are not eligible to participate in the study: 1. Office msSBP \<140 mmHg at Visit 20 OR 2. Office msSBP ≥180 mmHg or office msDBP ≥110 mmHg at the end-of-run-in visit (Visit 30) OR 3. 24h mean SBP \>170 mmHg or 24h mean DBP \>105mmHg measured by ABPM at the end of the run-in (Visit 30). 2. Known history of secondary hypertension (moderate-to-severe obstructive sleep apnea without receiving CPAP therapy (either face mask or nasal device), renovascular hypertension, primary aldosteronism, pheochromocytoma, Cushing syndrome, aortic coarctation or other cause of secondary hypertension). 3. Estimated GFR \<30 mL/min/1.73m2 using CKD-Epi equation at screening (Visit 1) or at end-of-run-in visit (Visit 30). 4. Serum potassium \>5.0 mmol/L (or equivalent plasma potassium value) at screening or end-of-run-in visit (Visit 30). 5. Current therapy with a mineralocorticoid receptor antagonist (MRA) or sacubitril/valsartan or received an MRA or sacubitril/valsartan within the 4 weeks prior to screening. 6. Type I diabetes mellitus or uncontrolled Type II diabetes (defined as a plasma HbA1c ≥9%) 7. Clinically significant cardiac arrhythmias (e.g., ventricular tachycardia), high-grade AV block (e.g., Mobitz type II and third-degree AV block in absence of a pacemaker) within 6 months of screening according to investigator's judgement. 8. Chronic non-paroxysmal atrial fibrillation. 9. Acute myocardial infarction (AMI) or unstable angina, or any history of ischemic or hemorrhagic stroke within 12 months of screening; or any percutaneous coronary intervention (PCI) or coronary artery bypass graft (CABG) within 12 months of screening 10. History of a renal denervation procedure. 11. Mid-arm circumference ≥44 cm. The cuff should snugly fit on the arm with out the margins of cuff overhanging arm musculature. 12. Patients with history of hospitalisation for hypertensive emergencies characterised by severe hypertension (usually grade 3) associated with funduscopic changes (flame haemorrhages and/or papilloedema), microangiopathy, disseminated intravascular coagulation, encephalopathy, acute aortic dissection, acute myocardial ischaemia, or acute heart failure any time prior to screening or hospitalisation for non-emergent/non-urgent uncontrolled hypertension without target organ damage within 3 months prior to screening 13. Receiving more than 4 antihypertensive medications. 14. Night shift workers. 15. History of presence of any other disease where the life expectancy is less than 3 years. 16. History of malignancy of any organ system (other than localized basal or squamous cell carcinoma of the skin or localized prostate cancer), treated or untreated, within the past 3 years, regardless of whether there is evidence of local recurrence or metastases. 17. Evidence of hepatic disease as determined by any one of the following: SGOT (AST) or SGPT (ALT) values exceeding 3x the upper limit of normal (ULN), or bilirubin \>1.5 mg/dl at Visit 1. 18. Use of other investigational drugs at the time of enrollment, or within 30 days or 5 half-lives of enrollment, whichever is longer. 19. History of drug abuse or alcohol dependency. 20. Lacking the ability to comprehend or follow instructions, or for any reason in the opinion of the investigator, a participant that would be unlikely or unable to comply with study protocol. 21. Concurrent enrollment in any other investigational drug or device trial (participation in non-interventional registries is acceptable). 22. Requiring prolonged/regular use of NSAIDs except for prophylactic use of low dose aspirin up to 325 mg QD or other prohibited medications during of the study (i.e., required use for longer than 1 week). 23. Pregnant, nursing or planning to become pregnant (documented negative pregnancy test required within a maximum of 7 days prior to enrollment of all women of childbearing potential). Documentation of highly effective contraception is also required for women of childbearing potential (see below). Women of child-bearing potential, defined as all women physiologically capable of becoming pregnant, unless they are using highly effective methods of contraception while taking study treatment and for 3 months after stopping medication. Highly effective contraception methods include: * Total abstinence (when this is in line with the preferred and usual lifestyle of the participant. Periodic abstinence (e.g. calendar, ovulation, symptom-thermal, post-ovulation methods) and withdrawal are not acceptable methods of contraception. * Female sterilization (have had surgical bilateral oophorectomy with or without hysterectomy), total hysterectomy, or bilateral tubal ligation at least six weeks before taking study treatment. In case of oophorectomy alone, only when the reproductive status of the woman has been confirmed by follow-up hormone level assessment. * Male sterilization (at least 6 months prior to screening). For female participants on the study, the vasectomized male partner should be the sole partner for that participant. * Use of oral, (estrogen and progesterone), injected, or implanted hormonal methods of contraception or placement of an intrauterine device (IUD) or intrauterine system (IUS), or other forms of hormonal contraception that have comparable efficacy (failure rate \< 1%), for example hormone vaginal ring or transdermal hormone contraception. In case of use of oral contraception women should have been stable on the same pill for a minimum of 3 months before taking study treatment. Women are considered post-menopausal if they have had 12 months of natural (spontaneous) amenorrhea with an appropriate clinical profile (e.g., age-appropriate history of vasomotor symptoms). Women are considered not of childbearing potential if they are post-menopausal or have had surgical bilateral oophorectomy (with or without hysterectomy), total hysterectomy or bilateral tubal ligation at least six weeks ago. In the case of oophorectomy alone, only when the reproductive status of the woman has been confirmed by follow-up hormone level assessment is she considered not of child bearing potential. If local regulations deviate from the contraception methods listed above to prevent pregnancy, local regulations apply and will be described in the ICF. 24. History of hypersensitivity to any of the study drugs, excipients or drugs of similar class.