The present Phase 1/2a study aims at demonstrating the safety and efficacy of ALLOB®, a proprietary population of allogeneic osteoblastic cells, in the treatment of delayed-union fractures of long bones. In this study, delayed-union is defined at the time of screening as an absence of healing of minimum 3 months and maximum 7 months (+/- 2 weeks) after the onset of the fracture.