He has been interested in the optimisation of CML treatment for more than 25 years and has been the principal investigator in several academic clinical trials. In 1984 he founded the Swedish CML Study Group and in 2004 the Nordic CML Study Group. Professor Simonsson is Chairman of the Nordic CML Study Group and of the Work Package 4 (CML) of the European LeukemiaNet (ELN). The ELN strengthens and develops scientific and technological excellence in the research and therapy of leukaemia in Europe.