1. From the Department of Medicine, Centre for Pharmacology and Therapeutics (L.A., V.A.-S., L.D., A.J.A., M.R.W., B.W.-S.) and Centre for Haematology (T.M.K.), Experimental Medicine, Imperial College London, United Kingdom; and Pulmonary Vascular Diseases Unit, Papworth Hospital NHS Foundation Trust, Papworth Everard Cambridge, United Kingdom (J.P.-Z., M.S., C.H., M.T.).