Evaluating the Efficacy of Sequential Microimmunotherapy Medicine on Early and Established Postmenopausal Osteoporosis Rat Model

Postmenopausal osteoporosis (OP) is characterized by an imbalance between bone formation and resorption due to declining estrogen levels, leading to progressive bone loss and increased fracture risk. This study aimed to evaluate the effects of the sequential microimmunotherapy medicine 2LOSTEO-N (MIM-seq) in two rat models of OP. Treatment began either 3 weeks (early-onset OP) or 15 weeks (established OP) after ovariectomy (OVX) and was administered orally for 9 weeks. The impact of MIM-seq was assessed through (i) body composition analysis, (ii) plasma bone turnover markers-CTX-I, alkaline phosphatase (ALP), osteoprotegerin (OPG), and RANKL-and (iii) bone quality by mechanical testing and micro-computed tomography (micro-CT) of trabecular bone morphology. In early-onset OP, MIM-seq improved vertebral strength, reduced CTX-I levels, and increased the OPG/RANKL ratio, suggesting a decrease in bone resorption. In established OP, MIM-seq also significantly reduced CTX-I levels. However, micro-CT analysis did not show significant changes in bone microarchitecture in either model. Overall, this study highlights the biological response to MIM-seq in experimental OP, indicating a modulatory effect on bone turnover markers and mechanical strength in early disease stages. Although no significant microstructural improvements were detected, these findings suggest potential therapeutic benefits of MIM-seq in bone health management.