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Lumbar spine BMD, bone strength benefits persist after romosozumab-to-alendronate switch



– Patients who took romosozumab for 12 months and then switched to alendronate continued to see benefits in bone mineral density (BMD) of the lumbar spine after 12 months of therapy with alendronate, compared with patients who began taking, and continued to take, alendronate over the same time period, according to findings from a subgroup of the ARCH study presented at the annual meeting of the American Society for Bone and Mineral Research.

“These effects occurred rapidly, as early as month 6, were sustained beyond 12 months after transitioning to alendronate, and are consistent with greater fracture-risk reduction observed in ARCH with romosozumab to alendronate versus alendronate to alendronate,” Jacques P. Brown, MD, FRCPC, of Laval University, Quebec City, said in his presentation.

In the double-blinded ARCH study, 4,093 postmenopausal women with osteoporosis and a previous fracture history were randomized to receive subcutaneous monthly romosozumab 210 mg or oral weekly alendronate 70 mg for 12 months, followed by an open-label period during which romosozumab patients received oral weekly alendronate 70 mg and alendronate patients continued to receive the same dose on the same schedule for an additional 24 months (Saag KG et al. N Eng J Med. 2017 Oct 12. doi: 10.1056/NEJMoa1708322).

Dr. Brown and colleagues performed an imaging substudy of ARCH, which included examining how the romosozumab-to-alendronate and alendronate-only groups improved lumbar spine BMD and lumbar spine bone strength. Lumbar spine BMD was assessed through quantitative CT, and lumbar spine bone strength was measured with finite element analysis. The researchers received quantitative CT images from baseline and at 6 months, 12 months, and 24 months, and determined the percentage change at each of those periods to calculate integral, trabecular, and cortical lumbar spine volumetric BMD (vBMD), and to bone mineral content (BMC). They also measured areal BMD (aBMD) at baseline, 6 months, 12 months, 18 months, and 24 months with dual-energy x-ray absorptiometry.

Overall, 49 romosozumab patients and 41 alendronate patients from the ARCH study were enrolled in the imaging substudy. Of those patients, 76 had vBMD and BMC information available at baseline and one or more time periods post baseline, and 86 patients had finite element analysis data at baseline and one or more postbaseline time periods. Patients in the romosozumab and alendronate groups had similar baseline characteristics with regard to age (73.1 years vs. 72.8 years, respectively), mean lumbar spine BMD T score (–2.82 vs. –3.38), mean total hip BMD T score (–2.65 vs. –2.75), mean femoral neck T score (–2.84 vs. –2.83), mean lumbar spine integral vBMD (130.3 mg/cm3 vs. 120.5 mg/cm3), trabecular vBMD (60.1 mg/cm3 vs. 53.7 mg/cm3) and cortical vBMD (284.6 mg/cm3 vs. 270.9 mg/cm3). Patients in both groups also had similar rates of previous osteoporotic fracture at or after aged 45 years, previous vertebral fracture, and history of hip fracture.

Beginning at 6 months, there were significant least squares mean BMD improvements in both groups, but the romosozumab group had significant improvements in aBMD percentage changes, compared with the alendronate group, which persisted until 24 months (P less than .001 at all time points). Integral, trabecular, and cortical vBMD in the romosozumab group also saw significantly greater increases from baseline, compared with the alendronate group, and those results persisted in the open-label portion of the study for patients in the romosozumab group who transitioned to alendronate and patients in the alendronate to alendronate group (P less than .001 at all time points).

“The rapid and large increases in BMD with romosozumab followed by BMD consolidation where [patients were] transitioning to alendronate, support the important role of romosozumab as a first-line therapy in treating patients who are at very high risk for fracture,” Dr. Brown said.

In regard to BMC, there were larger increases in least squares mean BMC changes from baseline in the cortical compartment than the trabecular compartment, and actual change in bone strength as measured by finite element analysis was highly correlated with integral BMC in the romosozumab group.

Dr. Brown said the study was limited to the small sample size from the imaging substudy of ARCH, and quantitative CT dictated the imaging sites for the substudy, which may have affected patient selection. However, he noted that the characteristics of the ARCH imaging substudy were similar to patients in the overall ARCH study.

Amgen, UCB Pharma, and Astellas Pharma funded the study in part. Amgen and UCB Pharma assisted in the preparation of Dr. Brown’s presentation at ASBMR 2019, including funding costs associated with its development. Dr. Brown and the other coauthors reported relationships with Amgen, UCB Pharma, and other companies in the form of consultancies, grants and research support, speaker’s bureau appointments, paid employment, and stock options.

SOURCE: Brown JP et al. ASBMR 2019, Abstract 1050.

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