Is Intention to Treat Still the Gold Standard or Should Health Technology Assessment Agencies Embrace a Broader Estimands Framework?: Insights and Perspectives From the National Institute for Health and Care Excellence and Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen on the International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use E9 (R1) Addendum

•The International Council for Harmonisation of Technical Requirements for Pharmaceuticals for Human Use E9 (R1) addendum, through the estimand framework, has affirmed the desirability, in certain circumstances, of estimating treatment effects in randomized controlled trials on the basis of strategies that depart from the intention-to-treat principle.•To the best of our knowledge, there have been limited attempts to date to assess the implications of the addendum for health technology assessment decision making.•To help with this shortfall, we discuss the perspectives of 2 agencies, the Institut für Qualität und Wirtschaftlichkeit im Gesundheitswesen and the National Institute for Health and Care Excellence, on the intention-to-treat principle, building on our understanding of published methods guidance, publicly available agency documents, and our experience of working with these agencies.