This investigator-initiated study aims to determine the effects of BAY2586116 (a novel TASK channel blocker nasal spray) on sleep apnoea severity and the potential influence of route of breathing.

Inclusion Criteria:

• Male or female participants aged 18 years or older at screening
• Must have completed Part A of the KOALA study (NCT04236440)
• Must be willing to sleep three nights in the sleep lab without OSA therapy (This includes continuous positive airway pressure therapy (CPAP) and/or a mandibular advancement device (MAD))
• Must be willing to refrain from drinking alcohol on the study days.
• Must be willing to limit consumption of tobacco to four cigarettes or one cigar a day and not smoke while at the sleep laboratory. This might be up to 12 hours.
• Must be willing to limit caffeinated beverage intake (coffee, tea, cola, and other soft drinks) to 400 mg / day or less of caffeine and not to be used within 4 hours of bedtime on study days.
• Contraceptive use required by men or women according to the methods of contraception for those participating in clinical studies

Exclusion Criteria:

• Any medications or herbal supplements that may interfere or be contraindicated with the study drug as determined by the investigator
• Severely impaired breathing within two days prior to randomization (e.g., acute nasal congestion during upper airway infection).
• known allergies or hypersensitivities to the study drugs (active substances or excipients of the preparations).
• Any other condition which at the discretion of the investigator would make the participant unsuitable for participation in the study and will not allow participation for the full planned study period (e.g., active malignancy or other condition limiting life expectancy to less than 12 months)

Individual data will be included in the study publication.

Upon publication

Available in the publication.

Participants and outcomes assessor (sleep scorer) blinded to all 3 study arms. Investigator blinded to 2/3 arms.