Assessing the effect of baseline status of serum bone turnover markers and vitamin D levels on efficacy of teriparatide 20 μg/day administered subcutaneously in Japanese patients with osteoporosis

In this previously reported multicenter study, teriparatide 20 μg/day was administered to elderly Japanese subjects (93 % female; median age 70 years) with osteoporosis and at high risk of fracture during a 12-month, randomized, double-blind, placebo-controlled period, which was followed by a 12 month treatment period in which all subjects received open-label teriparatide. Subjects were randomized 2:1 to teriparatide versus placebo (teriparatide n = 137, placebo-teriparatide n = 70). This was an exploratory analysis to determine whether the baseline status of serum bone turnover markers (BTMs) and vitamin D levels affect the efficacy of teriparatide at 20 μg/day. The BTMs included were type I procollagen N-terminal pro-peptide (P1NP) and type I collagen cross-linked C-telopeptide (CTX). Changes in BMD were analyzed by subgroups: (1) tertile subgroups of BTM; (2) BTM determined by the upper limit of normal; and (3) level of vitamin D. Teriparatide increased lumbar spine BMD in all subgroups by 10 % or more through 24 months. Subgroups with higher baseline BTM levels had greater mean percent changes of lumbar spine BMD through 24 months. The baseline status of vitamin D sufficiency did not impact the mean percent change of lumbar spine BMD through 24 months. Results of this study suggest that clinically significant increases in BMD can be achieved in patients receiving teriparatide regardless of baseline BTM or vitamin D levels. Additionally, when vitamin D is coadministered, vitamin D insufficiency would not be expected to affect the overall efficacy of teriparatide.