Experimental Medicine and Immunotherapeutics, University of Cambridge, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, UK. Experimental Medicine and Immunotherapeutics, University of Cambridge, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, UK; Sosei Heptares, Granta Park, Cambridge, UK; Metabolic Research Laboratories, Institute of Metabolic Sciences, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK. Sosei Heptares, Granta Park, Cambridge, UK. Metabolic Research Laboratories, Institute of Metabolic Sciences, University of Cambridge, Addenbrooke's Hospital, Cambridge, CB2 0QQ, UK. Experimental Medicine and Immunotherapeutics, University of Cambridge, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, UK. Electronic address: jjm1003@medschl.cam.ac.uk. Experimental Medicine and Immunotherapeutics, University of Cambridge, Level 6, Centre for Clinical Investigation, Addenbrooke's Hospital, Cambridge, UK. Electronic address: apd10@medschl.cam.ac.uk.