Background/Purpose:

The risk of fracture increases with increasing age. Thus, it is important to understand efficacy and safety of osteoporosis treatments in elderly patients. In the ACTIVE phase 3 study, 18 months (M) of abaloparatide (ABL) treatment significantly increased bone mineral density (BMD) and reduced the risk of new vertebral, nonvertebral, clinical, and major osteoporotic fractures vs placebo (PBO). Women receiving ABL or PBO in ACTIVE were offered enrollment in the ACTIVExtend extension study in which both groups received 24M open-label alendronate (ALN) 70 mg weekly for a total of 43M (18M ABL or PBO, 1M for reconsent, and 24M ALN). The objective of this post hoc analysis was to evaluate efficacy and safety of ABL followed by ALN (ABL/ALN) vs PBO/ALN in the subgroup of patients aged ≥80 years in ACTIVExtend.

Methods:

ACTIVExtend enrolled postmenopausal women with osteoporosis between the ages of 50 and 85; 558 were from the original ABL group and 581 from the PBO group of the ACTIVE study. Pre-specified endpoints, including BMD, new vertebral, nonvertebral, clinical, and major osteoporotic fractures, were assessed over the 43M period. Nonvertebral fracture endpoints were assessed using the Kaplan-Meier (KM) method, proportional hazard model, and logrank test.

Results:

A total of 56 ACTIVExtend patients (29 ABL/ALN; 27 PBO/ALN) were aged ≥80 years at ACTIVE baseline. Mean age was 81.8 years in both groups. Mean percent changes from baseline in total hip, femoral neck, and lumbar spine BMD were all significantly greater with ABL/ALN vs PBO/ALN at all timepoints assessed, except for total hip at M6. At M43, BMD mean percent change from baseline was 5.3% ABL/ALN vs 3.1% PBO/ALN (P=0.024) at the total hip, 4.6% ABL/ALN vs 3.1% PBO/ALN (P=0.044) at the femoral neck, and 17.2% ABL/ALN vs 8.6% PBO/ALN (P<0.0001) at the lumbar spine. Fracture rates were very low in both groups in this small subset of women (new vertebral: 0 ABL/ALN, 1 PBO/ALN; nonvertebral: 1 ABL/ALN, 2 PBO/ALN). Adverse event rates were similar between treatment arms with 78.6% and 81.5% of patients in the ABL/ALN and PBO/ALN groups, respectively reporting ≥1 treatment-emergent adverse event.

Conclusion:

In conclusion, significant BMD gains were maintained through 43M with ABL/ALN vs PBO/ALN. This post hoc analysis suggests that an ABL/ALN treatment was effective in an elderly subgroup of ACTIVExtend, with a safety profile similar across treatment arms.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/abaloparatide-effect-on-bone-mineral-density-and-fracture-incidence-in-postmenopausal-women-with-osteoporosis-aged-80-years-or-older/