ACVR1 and hereditary disease: This is in part because unlike the case for most genetic disorders, ACVR1 is both a receptor and a kinase, and therefore, provides at least four different ‘ACVR1-centric’ paths to drug development: (a) inhibitors of ACVR1 kinase (several of which are under development) [68–72]; (b) antisense oligonucleotides or siRNA based therapeutics [73,74]; (c) antibodies that bind the extracellular domain of ACVR1 and block its function; and, (d) antibodies to putative ligand(s) responsible for activating ACVR1 in a manner that results in HO.