A Study to Evaluate the Effect of ACT-774312 in Subjects With Bilateral Nasal Polyposis

Inclusion Criteria: * Signed informed consent in the local language prior to any study mandated procedure. * A minimum bilateral nasal polyp score (NPS) of 5 out of a maximum of 8 for both nostrils (with at least a score of 2 for each nostril) despite completion of a prior intranasal corticosteroids (INCS) treatment for at least 8 weeks before screening, with at least the 6 last weeks on INCS spray. * Presence of at least 2 of the following symptoms at screening: * nasal blockade/obstruction * nasal discharge (anterior/posterior nasal drip) * reduction or loss of smell. * Male and female participants aged between 18 and 70 years (inclusive) at screening. * Systolic blood pressure 90 to 160 mmHg, diastolic blood pressure 50 to 100 mmHg, pulse rate 45 to 100 bpm (inclusive), measured on the dominant arm, after 5 minutes in the supine position at screening. * Women of childbearing potential must have a negative serum pregnancy test at screening and a negative urine pregnancy test pre-dose on Day 1. Women of childbearing potential must consistently and correctly use (from at least first dosing, during the entire study, and for at least 30 days after last study treatment intake) 1 highly effective method of contraception with a failure rate of less than 1% per year, be sexually abstinent, or have a vasectomized partner. Hormonal contraceptive must have been initiated at least 1 month before first study treatment administration. Exclusion Criteria: * CYP2C9 poor metaboliz…