To Evaluate the Efficacy and Safety of Amorphous Calcium Carbonate in RA Patient With Osteopenia or Osteoporosis

This is a randomized, double-blind, active-controlled study to evaluate the efficacy and safety of amorphous calcium carbonate in rheumatoid arthritis patients with osteopenia or osteoporosis, compared to crystalized calcium carbonate. A total of 180 subjects will be enrolled into this study. Eligible subjects will be randomized to receive amorphous calcium carbonate (ACC group) or crystalized calcium carbonate (CCC group) with 1:1 allocation. Randomization will be stratified by the use of biologics. The study product, 2 tablets (400mg calcium element), will be taken twice daily approximately 30 minutes after breakfast and dinner during 12-month treatment period. Additional 600 IU vitamin D3 will be also received with investigational product after breakfast. The study will consist of 7 clinical visits. Subjects will come to the clinics at Visit 1 (screening visit), Visit 2 (randomization, regimen start), Visit 3 to 6 (follow-up visits), and Visit 7 (post-treatment follow-up visits) according to the pre-defined schedule. The DXA score, and BTM (P1NP, CTX) from fasting serum samples, and FRAX score will be collected. The treatment-emergent adverse events for safety endpoints will be also recorded.