Background/Purpose:

Abaloparatide (ABL) is a selective activator of the PTH1 receptor signaling pathway that stimulates bone formation. In the ACTIVE Phase 3 study, ABL significantly increased BMD and reduced the risk vertebral, nonvertebral, clinical, and major osteoporotic fractures in women with postmenopausal osteoporosis compared with placebo (PBO). In ACTIVExtend, the ABL and PBO arms were switched to receive alendronate (ALN) 70 mg weekly for two years. The objective of these analyses was to evaluate bone mineral density (BMD) response rates with ABL/ALN vs PBO/ALN in ACTIVExtend.

Methods:

BMD was measured at the lumbar spine, total hip, and femoral neck from the beginning of ACTIVE to the end of ACTIVExtend (18 months of ABL or PBO followed by 1 month for reconsent, followed by 24 months of ALN treatment for a total of 43 months). Measurements were collected from 1,139 women enrolled in ACTIVExtend, and were centrally analyzed. Patients experiencing BMD gains of >0%, >3%, and >6% at the lumbar spine, total hip, and femoral neck were evaluated. A responder was defined as a patient with BMD increases at all three sites. A Chi-square test was used to determine the difference in number of responders between treatment groups.

Results:

From ACTIVE baseline through month 43 of ACTIVExtend, BMD increases of >3% were observed at the lumbar spine in 93.1% (472/507 evaluable patients) and 79.4% (404/509) patients, at the total hip in 80.1% (406/507) and 52.1% (263/505) patients, and at the femoral neck in 67.5% (342/507) and 34.9% (176/505) patients in ABL/ALN and PBO/ALN groups, respectively. A greater percentage of patients in the ABL/ALN group responded with BMD changes from ACTIVE baseline of >0%, >3%, and >6% at all three sites combined compared with the PBO/ALN group (P<0.0001 for each comparison). At month 43, 60.7% (307/506) vs 24.0% (121/505) of patients experienced BMD increases of >3% at all three sites in ABL/ALN vs PBO/ALN groups, respectively (P<0.0001). Increases of >6% at all three sites were experienced by 33.2% (168/506) vs 4.0% (20/505) of patients in ABL/ALN vs PBO/ALN groups, respectively (P< 0.0001).

Conclusion:

In conclusion, from ACTIVE baseline through the 43 months of ACTIVExtend, BMD response increased in both ABL/ALN and PBO/ALN groups, with significantly greater response rates in the ABL/ALN group at the total hip, femoral neck, and lumbar spine. Results are consistent with significant BMD response with ABL vs PBO observed in ACTIVE, and continued fracture risk reduction from ACTIVE through ACTIVExtend with sequential ABL/ALN compared with PBO/ALN treatment.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/response-rates-for-hip-femoral-neck-and-lumbar-spine-bone-mineral-density-in-patients-treated-with-abaloparatide-followed-by-alendronate/