BMP agonist 2 (derivative I-9) is a potent bone-inducing cytokine. BMP agonist 2 promotes bone tissue production by increasing the proportion and activity of osteoblasts. BMP agonist 2 promotes osteoblast proliferation and differentiation through the BMP2-ATF4 signaling axis, in which ATF4 is a transcription factor closely related to osteoblast differentiation and bone formation. BMP agonist 2 can be used in the study of senile osteoporosis (SOP).