This is a double-blind, placebo-controlled, multicenter, efficacy and safety study of firibastat (QGC001) administered po bid over 12 weeks in male and female subjects ≥18 years of age at Screening, with uncontrolled primary HTN. Subjects will be randomized 1:1 to investigational product (IP) and will receive either firibastat (QGC001) or matching placebo on top of their current chronic antihypertensive treatments.

The primary objective of this study is to assess the effects of administration of firibastat (QGC001) 500 mg oral (po) twice daily (bis in die [bid]) on blood pressure (BP) over 12 weeks in subjects with uncontrolled primary HTN.

Inclusion Criteria:

• Men and women ≥18 years of age at Screening
• Diagnosis of primary HTN for at least 6 months prior to Screening

Exclusion Criteria:

• Known or suspected secondary HTN (eg, hyperaldosteronism, renovascular HTN, pheochromocytoma, Cushing's disease).
• Automated office SBP >180 mmHg or DBP >110 mmHg at the Screening or Inclusion Visit (Visit 2, Day 1) and confirmed by a second measurement within 30 minutes to 1 hour.
• Known hypertensive retinopathy (Keith-Wagener Grade 3 or Grade 4) and/or hypertensive encephalopathy.