Bone turnover markers predict changes in bone mineral density in men treated with abaloparatide: results from the abaloparatide for the treatment of men with osteoporosis (ATOM) study

Early increases in bone turnover markers (BTMs) in response to anabolic therapy correlate with 18-mo BMD increases in postmenopausal women with osteoporosis; however, this relationship has not been assessed in men. In this analysis, the correlation between changes from baseline in fasting intact serum procollagen type I N propeptide (PINP) and serum CTX at 1, 3, 6, and 12 mo and percent increase from baseline in BMD at 12 mo in men from the randomized phase 3 ATOM study (NCT03512262) were evaluated using Pearson's correlation coefficients. The uncoupling index (UI), a measure of the balance between markers of bone formation (PINP) and bone resorption (CTX), with positive UI favoring bone formation, was calculated. Results in men were compared to 12-mo results for women from the ACTIVE study using the z score test after Fisher's Z transformation. In abaloparatide-treated men, PINP increases at 1 mo (r = 0.485), 3 mo (r = 0.614), 6 mo (r = 0.632), and 12 mo (r = 0.521) were highly correlated (p < .0001) with 12-mo LS BMD increases. The mean UI for abaloparatide-treated men was greater than placebo as early as 1 mo (2.26 vs -0.25). At month 3, the mean UI for men was greater (1.32) than for women (0.88) (p < .001). There was a significant correlation between 3-mo UI and LS BMD at 12 mo in both men (r = 0.453; p < .001) and women (r = 0.252; p < .01). UI at months 6 and 12 were also significantly correlated with 12-mo LS BMD in men and women, but the correlation was stronger in men than women. These data support that early changes in BTMs in men treated with abaloparatide are associated with subsequent changes in BMD similar to what has been reported in women.