Recombinant Anti-DKK1 x Anti-SOST Bispecific Antibody (Tandem Fab) is designed to be expressed as three chains derived from the variable domains of anti-DKK1 and anti-SOST parental antibodies. It contains a His-tag for affinity purification. And the two Fd regions are connected by a flexible linker. This BsAb can bind two factors simultaneously and promote osteoblastogenesis. It is designed for the research of Osteoporosis; Osteogenesis imperfecta (OI); Low bone mineral density; Fracture therapy.