Investigating potential treatments for human lung injury in healthy volunteers

INTERVENTION: Participants will be randomised to intervention or comparator by computer programme. The intervention will be Baricitinib (Olumiant) 4mg orally, once daily for 3 days. Comparator is no intervention. Participants and clinicians will be unblinded to intervention. Laboratory staff undertaking the analysis will be blinded. Day 4 of study period: the participant will be brought back the day after they have completed all study interventions i.e.: completed treatment period of 3 days and undergone LPS challenge, and bronchoalveolar lavage for safety screening. CONDITION: Acute Respiratory Distress Syndrome (ARDS) ; Respiratory PRIMARY OUTCOME: Broncho‐alveolar lavage neutrophil count during bronchoscopy at day 4 SECONDARY OUTCOME: Broncho‐alveolar lavage fluid/Plasma/Urine: cytokines including but not limited to Il‐6, IL‐10, IL‐18, CXCL8, IL‐1b, markers of epithelial and endothelial injury including but not limited to RAGE, SP‐D, Ang2, single‐cell RNA sequencing, plasma differential white cell count, BAL differential white cell count, plasma C‐reactive protein INCLUSION CRITERIA: Healthy non‐smoking adults aged 18‐45 years old