Romosozumab-induced P1NP decline predicts 2-year lumbar spine BMD gain after sequential therapy
Background
Identifying patients who will achieve optimal long-term bone mineral density (BMD) gains after sequential therapy following romosozumab treatment for osteoporosis remains a key challenge. While romosozumab, a sclerostin inhibitor, significantly increases BMD, the magnitude of on-treatment changes in bone turnover markers (BTMs) like P1NP and TRACP-5b has not been established as a predictor for cumulative 2-year BMD. Understanding this predictive relationship could enable more personalized treatment strategies and improve patient outcomes by identifying those most likely to benefit.
Study Design
This retrospective single-center cohort study (initial n=315) analyzed 129 patients with complete on-treatment BTM pairs and 24-month BMD data. Researchers calculated on-treatment changes in procollagen type I N-terminal propeptide (ΔP1NP) and tartrate-resistant acid phosphatase 5b (ΔTRACP-5b) as the difference between post-treatment and pre-treatment values. The primary outcome was the cumulative percentage change in lumbar spine BMD (LS-BMD) from baseline to 24 months. Spearman's rank correlations and multiple linear regression (adjusting for age, baseline LS-BMD, prior treatment, sequential therapy type, and 12-month BMD change) were performed, alongside ROC analysis to define an optimal ΔP1NP cutoff.
Results
ΔP1NP was significantly correlated with the 24-month cumulative LS-BMD change (ρ=-0.375, p<0.0001, n=129), indicating a greater decline in P1NP during romosozumab treatment predicted greater cumulative BMD gain. ΔTRACP-5b showed a similar association (ρ=-0.348, p=0.0001, n=114). In multiple linear regression, ΔP1NP remained an independent predictor (β=-0.061, p=0.010; model R²=0.796, n=113). The optimal ΔP1NP cutoff for predicting a good response was -40.3 μg/L (AUC = 0.761; sensitivity=0.545, specificity=0.854).
Patients in the highest
ΔP1NPdecline tertile (T1) achieved 23.5% cumulativeLS-BMDgain versus 12.3% in the lowest tertile (T3; p=0.0003). This association was replicated in the denosumab sequential therapy subgroup (ρ=-0.354).
Key Findings
- On-treatment
ΔP1NPcorrelated significantly with 24-month cumulativeLS-BMDchange (ρ=-0.375, p<0.0001). - A greater decline in
P1NPduring romosozumab predicted greater cumulative BMD gain. ΔP1NPremained an independent predictor of BMD gain in multiple linear regression (β=-0.061, p=0.010).- An optimal
ΔP1NPcutoff of -40.3 μg/L predicted good response (AUC = 0.761). - Highest
ΔP1NPdecline tertile achieved 23.5%LS-BMDgain vs. 12.3% in lowest tertile (p=0.0003).
Why It Matters
This study provides a practical biomarker for predicting long-term bone mineral density (BMD) response to romosozumab and subsequent sequential therapy. Monitoring on-treatment P1NP changes could enable clinicians to identify patients most likely to achieve substantial 2-year BMD gains, or conversely, those who may require earlier intervention adjustments. This could lead to more personalized treatment protocols for osteoporosis, potentially optimizing therapeutic outcomes and reducing fracture risk. While a specific dosing protocol isn't provided, the finding supports integrating P1NP monitoring into existing clinical pathways to guide sequential therapy decisions, moving towards a more data-driven approach to bone health management.
romosozumab
osteoporosis
bone-mineral-density
p1np
tracp-5b
sclerostin-inhibitor