His decade-long career as a health systems, HIV and viral hepatitis expert at WHO’s Regional Office for Europe was followed by three years at the Global Fund to Fight AIDS, Tuberculosis and Malaria. He is the past Vice-Chair of the EASL International Liver Foundation, Board Chair of AFEW International and he was the first director of Health Systems Global. He currently serves as the Chair of the Healthy Livers, Healthy Lives coalition, and is on the leadership committee of the Global NASH Council and a member of the ICE-HBV, ACHIEVE and AEHVE viral hepatitis elimination coalitions as well as the technical advisory group of CGHE. He co-chairs the annual Innovations in SLD Think-tank and is chair of the Wilton Park NAFLD meetings.

He is the author of more than 400 publications, and is principal investigator of multiple global consensus statements as well as the MASLD/MASH Best Buys, MASH investment framework, Doubling the Diagnosed, VH-COMSAVAC, COVID-VAC and a work package leader of LiverAIM. He has had continuous competitive funding for over a decade. In 2017 he joined the Lancet GastroHep Commission on viral hepatitis and in 2018 became a working group chair of the EASL-Lancet European Liver Commission. He is the lead of the Nature #COVIDconsensus and a co-author of The Lancet COVID-19 Commission. He is on the editorial board of HIV Medicine, the International Journal of Drug Policy and Liver International.