FST and inclusion body myositis: Significant improvements in muscle strength or physical function have not been reached7–9 with the exception of two small open-label studies using an AAV vector encoding the follistatin isoform FS344 intramuscularly injected in Becker Muscular Dystrophy (BMD, n = 6) patients and in Inclusion Body Myositis (IBM, n = 6)10–12 and 1 small randomised controlled trial using a monoclonal antibody against the AcvRII receptor in IBM patients (n = 11 active, 3 placebo)13.