Background/Purpose:  STRUCTURE was a phase 3, open-label study evaluating the effect of romosozumab or teriparatide for 12 months in women with postmenopausal osteoporosis transitioning from bisphosphonate therapy (NCT01796301).

Methods:   This multicenter, active-controlled study enrolled women with postmenopausal osteoporosis who had taken an oral bisphosphonate for ≥ 3 years prior to screening and alendronate (70 mg weekly or equivalent) in the year prior to screening; had a bone mineral density (BMD) T-score ≤ –2.5 at the total hip, lumbar spine, or femoral neck; and had a history of nonvertebral fracture after age 50 or vertebral fracture. Subjects received daily calcium and vitamin D and were randomized to receive subcutaneous romosozumab 210 mg once monthly or teriparatide 20 µg once daily. The primary endpoint was percent change from baseline in BMD by DXA at the total hip through month 12 (the average at months 6 and 12). Secondary endpoints included percent change from baseline at months 6 and 12 in BMD by DXA at the total hip, lumbar spine, and femoral neck; hip integral and cortical BMD by quantitative computed tomography (QCT); and estimated hip strength by finite element analysis. Imaging assessments were done blinded to treatment.

Results:   A total of 436 women, with a mean age of 72 years, were randomized to receive romosozumab (N = 218) or teriparatide (N = 218). Baseline mean total hip, lumbar spine, and femoral neck T-scores were –2.2, –2.9, and –2.5, respectively. Through 12 months, the mean (95% CI) percent change from baseline in total hip BMD by DXA was 2.6% (2.2, 3.0) with romosozumab and –0.6% (–1.0, –0.2) with teriparatide (p < 0.0001 between groups). Total hip BMD changes at months 6 and 12 were significantly larger with romosozumab than with teriparatide (p < 0.0001): month 6, 2.3% (1.9, 2.7) vs –0.8% (–1.2, –0.4); month 12, 2.9% (2.5, 3.4) vs –0.5% (–0.9, 0), respectively. Romosozumab also resulted in significantly larger BMD gains at the lumbar spine at months 6 and 12 vs teriparatide (p < 0.0001): month 6, 7.2% (6.6, 7.8) vs 3.5% (2.9, 4.0); month 12, 9.8% (9.0, 10.5) vs 5.4% (4.7, 6.1), respectively. QCT assessments of the hip demonstrated significantly greater gains in integral and cortical BMD with romosozumab vs teriparatide at months 6 and 12 (p < 0.0001). Estimated hip strength gains were also significantly larger with romosozumab at both time points (p < 0.0001) and declined from baseline in teriparatide-treated subjects at month 6. The subject incidences of treatment emergent adverse events and adverse events of interest were generally balanced between treatment groups.

Conclusion:  In subjects transitioning from bisphosphonate therapy, romosozumab was well-tolerated and was associated with significant BMD gains at both the hip and spine compared with teriparatide. BMD gains in the cortical compartment contributed to the greater treatment effect of romosozumab at the hip. Estimated hip strength improved with romosozumab over 12 months but decreased early with teriparatide. A global phase 3 program evaluating romosozumab for the treatment of postmenopausal osteoporosis is ongoing.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/superior-gains-in-bone-mineral-density-and-estimated-strength-at-the-hip-for-romosozumab-compared-with-teriparatide-in-women-with-postmenopausal-osteoporosis-transitioning-from-bisphosphonate-therapy/