A monoclonal antibody that blocks the activation of the skeletal muscle protein myostatin could be novel muscle-directed therapy for spinal muscular atrophy patients. Cambridge, Mass.–based Scholar Rock (NSDQ:SRRK), which makes the SRK-015 investigational antibody, saw its shares more than double to $30.02 apiece yesterday. SRK-015 could lead to the formation of a new treatment category…