Eldecalcitol is more effective for the prevention of osteoporotic fractures than alfacalcidol

Eldecalcitol, a vitamin D3 analogue, significantly reduces the risk of new vertebral fractures and increases bone mineral density (BMD) more than does alfacalcidol. To determine the effect of eldecalcitol on the incidence of all fragility fractures caused by osteoporosis, we conducted post hoc analyses of the phase III clinical trial to evaluate the incidence of the osteoporotic fractures defined in the World Health Organization (WHO) Technical Report, and, also, the incidence of the major osteoporotic fractures utilized in the WHO Fracture Risk Assessment Tool (FRAX), and compared those in the eldecalcitol group with those in the alfacalcidol group. We also analyzed the incidence of osteoporotic fractures stratified by prespecified risk factors for fractures. Eldecalcitol treatment reduced the incidence of osteoporotic fractures defined by the WHO more than alfacalcidol treatment (18.6 % vs. 25.2 %; hazard ratio, 0.70; 95 % CI, 0.54-0.93). Prevalent vertebral fractures, two or more prevalent vertebral fractures, and total hip BMD T score less than -2.5 were the risk factors for new osteoporotic fractures with significant differences between the two treatments. Eldecalcitol also decreased the incidence of major osteoporotic fractures in the FRAX more than alfacalcidol (11.1 % vs. 16.3 %; hazard ratio, 0.66; 95 % CI, 0.46-0.94). In conclusion, treatment with eldecalcitol reduced the risk of fragility fractures caused by osteoporosis compared with alfacalcidol administration, which may result from a potent effect of eldecalcitol on BMD, bone structure, and bone turnover.