Greater lumbar spine BMD gains with romosozumab for postmeno
Postmenopausal women with osteoporosis receiving romosozumab for 12 months had larger improvements in bone mineral density and bone strength at the lumbar spine compared with those receiving alendronate alone, according to study data.

The ARCH trial showed that romosozumab for 1?year followed by alendronate led to larger areal BMD (aBMD) gains and superior fracture risk reduction versus alendronate alone. aBMD correlates with bone strength but does not capture all determinants of bone strength that might be differentially affected by various osteoporosis therapeutic agents. This study therefore used QCT and finite element analysis (FEA) to assess changes in lumbar spine volumetric BMD (vBMD), bone volume, bone mineral content (BMC), and bone strength with romosozumab versus alendronate in a subset of ARCH patients.

In ARCH, 4093 postmenopausal women with severe osteoporosis received monthly s.c. romosozumab 210?mg or weekly oral alendronate 70?mg for 12?months, followed by open-label weekly oral alendronate 70?mg for more than 12?months. Of these, 90 (49 romosozumab, 41 alendronate) enrolled in the QCT/FEA imaging substudy. QCT scans at baseline and Months 6, 12, and 24 were assessed to determine changes in integral (total), cortical, and trabecular lumbar spine vBMD and corresponding bone strength by FEA. Additional outcomes assessed include changes in aBMD, bone volume, and BMC.

Romosozumab caused greater gains in lumbar spine integral, cortical, and trabecular vBMD and BMC than alendronate at Months 6 and 12, with the greater gains maintained upon transition to alendronate through Month 24. These improvements were accompanied by significantly greater increases in FEA bone strength. Most newly formed bone was accrued in the cortical compartment, with romosozumab showing larger absolute BMC gains than alendronate.

In conclusion, romosozumab significantly improved bone mass and bone strength parameters at the lumbar spine compared with alendronate. These results are consistent with greater vertebral fracture risk reduction observed with romosozumab versus alendronate in ARCH and provide insights into structural determinants of this differential treatment effect.