This is a Phase III, multicentre, randomised, double-blind, placebo-controlled, parallel-group study to evaluate the safety, tolerability, and efficacy of baxdrostat versus placebo, on the reduction of Seated Blood Pressure (SBP) and achieving normalization of the Renin Angiotensin Aldosterone System (RAAS) in approximately 250 participants ≥ 18 years of age with Primary Aldosteronism (PA), with or without prior treatment with Mineralocorticoid Receptor Antagonists (MRAs) or potassium-sparing diuretics.

Baxdrostat (or placebo) will be administered once daily, up-titrated after 2 weeks based on clinical response and tolerability.

The study is planned to be conducted globally in approximately 90 study centres and 12 countries.

Inclusion Criteria:

• Male or female participants must be ≥ 18 years of age

• Participants with a documented diagnosis of PA that fulfils the criteria defined in the 2016 or 2025 Endocrine Society Guidelines.

• Participants willing and able to cease dosing of MRA or potassium sparing diuretics per study requirement for participants taking an MRA or potassium sparing diuretic at Screening.

• eGFR ≥ 45 mL/min/1.73m2 at Screening

• Serum potassium level ≥ 3.0 and < 5.0 mmol/L at Screening determined as per the central laboratory.

• Have a stable regimen of antihypertensive medications for at least 4 weeks prior to randomisation

• Mean seated SBP on AOBPM of ≥ 135 mmHg and ≤ 170 mmHg and mean DBP of

  ≤ 105 mmHg.

• Serum potassium (local lab) > 3.0 mmol/L at randomization.

Exclusion Criteria:

- If not taking an MRA or potassium sparing diuretic at Screening: Mean seated SBP > 170 mmHg or mean seated DBP >105 mmHg (on AOBPM).

If taking an MRA or potassium sparing diuretic at Screening: Mean seated SBP > 160 mmHg or mean seated DBP ≥ 100 mmHg.

• Previous surgical intervention for an adrenal adenoma or have a planned adrenalectomy, renal nerve denervation, or adrenal ablative procedure during the course of the study.
• Has the following known secondary causes of HTN: renal artery stenosis, uncontrolled or untreated hyperthyroidism, uncontrolled or untreated hypothyroidism, pheochromocytoma, Cushing's syndrome, aortic coarctation.
• Serum sodium level < 135 mmol/L at Screening, determined as per central laboratory.
• New York Heart Association functional HF class IV at Screening.
• Persistent atrial fibrillation.
• Treatment with any MRA or potassium-sparing diuretic within 2 weeks prior to Randomisation.

Qualified researchers can request access to anonymized individual patient-level data from AstraZeneca group of companies sponsored clinical trials via the request portal Vivli.org. All requests will be evaluated as per the AZ disclosure commitment:

https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

"Yes", indicates that AZ are accepting requests for IPD, but this does not mean all requests will be approved.

AstraZeneca will meet or exceed data availability as per the commitments made to the EFPIA/PhRMA Data-Sharing Principles. For details of our timelines, please refer to our disclosure commitment at:

https://astrazenecagrouptrials.pharmacm.com/ST/Submission/Disclosure.

When a request has been approved AstraZeneca will provide access to the anonymized individual patient-level data via secure research environment Vivli.org. A Signed Data Usage Agreement (non-negotiable contract for data accessors) must be in place before accessing requested information.