ACVR1B and cancer: Taking these data into consideration, we sought to determine whether (1) systemic inhibition of ALK4/5, and thus potentially blocking the myostatin signalling pathway, enhances myogenesis in vitro and limits muscle wasting in experimental cancer cachexia in vivo, and (2) whether combined treatment of ALK 4/5 inhibition and IGF-I supplementation would improve treatment outcome without impacting on tumour growth50.