This applies to the mAb used for our studies that target human ALK1 receptor, a cell surface receptor preferentially expressed on endothelial cells as well as various solid human tumors.31 For locally expressed membrane bound targets in the extravascular space, the target concentration, when normalized by the volume of the tumor, may be comparable between adult and children if the tumor biology and the tumor volume are the same. Here, CD177 is linked to neoplasm.