Accordingly, we performed a first-in-patient randomised, multicentre, double-blind, placebo-controlled, parallel group-comparison study to investigate the efficacy and safety of BAY 2253651 for the treatment of OSA.Adults currently on treatment for OSA with continuous pos. airway pressure (CPAP) (3 mo), with an apnoea-hypopnoea index (AHI) of 15-50 h-1 after 48 h of CPAP withdrawal documented by polysomnog. (PSG; night 1) (table 1) and at least 4 h of sleep time, were eligible to participate in the study.As genioglossus muscle activation alone in very severe and multifactorial OSA (i.e. AHI >50 h-1) is less likely to be efficacious, these individuals were not enrolled.All participants provided informed consent and were investigated at tertiary centers by an experienced investigator.The trial was registered a priori (ClinicalTrials.gov identifier: NCT03603678; EudraCT-number 2017-001851-29) and an independent data monitoring committee was delegated.The study data remained blinded until all clin. assessments have been completed, database lock and authorisation of data release according to standard operating procedures.This study was planned to fulfil the go criterion if the posterior probability that the responder rate in the active arm is larger than the responder rate under placebo exceeds 0.95.On the assumption of a response rate of 0.10 to placebo and 0.40 to the active drug, 30 participants per treatment arm were needed to provide 87% probability to go.The sponsor terminated the trial for futility after data review of the first 30 subjects randomised.Finally, there were no major discernible differences in other polysomnog. or pulse oximetric parameters between the BAY 2253651- and placebo-treated patient groups.However, similar to other non-CPAP interventions and consistent with OSA endophenotyping concepts, those who have less collapsible pharyngeal airways at baseline may be more likely to respond favorably to pharmacotherapy.Lastly, BAY 2253651 was safe and well-tolerated in the treated group of OSA patients.