The study is a multicentre, open label, phase I, two arms study to compare pharmacokinetic of firibastat after a single oral dose of firibastat 500 mg in fourteen healthy male volunteers and in fourteen End Stage Renal Disease (ESRD) patients not yet in dialysis.

It is planned to enroll a total of 28 subjects to receive a single oral dose of investigational medicinal product (IMP): 14 ESRD patients will be enrolled in three Hungarian centres (1st arm) and 14 Healthy volunteers will be enrolled by Eurofins Optimed in Gières, France (2nd arm).

Subjects will be screened for eligibility to participate in the study up to 21 days prior to the first administration. For both arm, subjects will be admitted into the Clinical Research Unit (CRU) on Day -3. On the morning of Day 1, subjects will receive a single 500 mg oral dose of firibastat following an overnight fast (i.e., at least 10 hours). Subjects will be confined to the CRU until discharge on Day 3 with PK blood sample draws for measurement of firibastat and its main metabolites being taken throughout the confinement.

A follow-up post study visit will occur on Day 10 post-dose to ensure the ongoing wellbeing of the subjects.

Inclusion Criteria:

• Male subjects, aged 18 to 55 years inclusive;
• Non-smoker subject or smoker of not more than 5 cigarettes a day;

Exclusion Criteria:

• Positive Hepatitis B surface (HBs) antigen or anti Hepatitis C Virus (HCV) antibody, or positive results for Human Immunodeficiency Virus (HIV) 1 or 2 tests);
• History or presence of drug or alcohol abuse (alcohol consumption > 40 grams/day);