Denosumab Favored Over Alendronate for BMD Protection in Glucocorticoid-Induced Osteoporosis

Damian McNamara

November 13, 2020

Denosumab boosted bone mineral density (BMD) over 12 months to a greater extent than did alendronate in a randomized, 12-month study. The investigator-initiated research compared BMD at the lumbar spine and elsewhere among people with systemic lupus erythematosus (SLE) and other autoimmune conditions. Long-term glucocorticoid therapy places some people in this group at higher risk for adverse effects of bone density loss.

"Glucocorticoids remain the mainstay of treatment of rheumatic diseases, but [they are] a major risk factor for osteoporosis and fracture," study author Chi Chiu Mok, MD, said in an interview.

Compared with baseline, adults randomly assigned to denosumab had a 3.5% increase in lumbar spine BMD at 12 months, compared with 2.5% among those taking alendronate, a significant difference. Mok, a consultant and honorary associate professor in the department of medicine and nuclear medicine at Tuen Mun Hospital in Hong Kong, presented the study results at the virtual annual meeting of the American College of Rheumatology.

"Given the knowledge that denosumab is more effective than alendronate in raising spinal BMD in chronic users of GCs without increasing adverse events, this drug may be considered as an alternative first-line therapy in higher-risk patients and in those who are contraindicated for the oral bisphosphonates," he said.

Cost Considerations

Denosumab is a human monoclonal antibody administered as a subcutaneous injection, available under the brand names Prolia and Xgeva. Alendronate is an oral agent available as both generic and brand name formulations.

"Yes, denosumab is more expensive, more costly than oral alendronate, but our study shows efficacy is better for steroid users," Mok said in answer to a question about cost disparity between the two agents during his presentation at the meeting. "For patients who are contraindicated or have low compliance for bisphosphonate, or are high-risk patients, I recommend first-line use of denosumab."

Researchers previously studied these agents, including a smaller study by Mok and colleagues that showed a BMD benefit after switching people on an oral bisphosphonate to denosumab. However, he said, "There is a paucity of data regarding comparative efficacy of denosumab and the bisphosphonates in long-term steroid users."

To explore any differences in a larger patient population, the investigators randomly assigned adults with SLE and other autoimmune conditions to the two treatments: denosumab 60 mg subcutaneoulsy every 6 months or oral alendronate 70 mg/week. All patients also received 3,000 mg calcium and 1,000 IU vitamin D3 (cholecalciferol) each day.

After three discontinuations in denosumab cohort and four in the alendronate group, the researchers evaluated 69 people taking denosumab and 70 others taking alendronate. The discontinuations were caused by noncompliance, Mok said, not by adverse events.

Adverse events were reported, but the rate did not differ significantly between groups. Mok highlighted some notable differences, including more minor infections and arthralgias reported in the denosumab cohort. Chest discomfort was reported in one denosumab recipient versus no patients in the alendronate group. Dyspepsia/upper GI symptoms and dizziness/vertigo occurred more often in the alendronate group.

Women were 96% of the study population, and mean age was 50 years. A majority, 81%, had underlying SLE. Other diagnoses included rheumatoid arthritis, myositis, antineutrophil cytoplasmic antibody–associated vasculitis, and polymyalgia rheumatica. The mean dose of prednisolone at study entry was 5.1 mg/day.

Key BMD and Biomarker Findings

BMD increased significantly in the spine, hip, and femoral neck in both treatment groups by 12 months. However, after adjustment for baseline BMD and covariates including age, menopause, and history of fracture, the gains in the denosumab group were significantly higher.

The increase in lumbar spine BMD at 12 months of 3.5% in the denosumab group versus 2.5% in the alendronate group was statistically significant (P = .045). Less significant was a 0.9% increase at the hip in the denosumab patients versus 1.6% in the alendronate group (P = .10), as well as femoral neck BMD gains of 1% in the denosumab group versus 1.5% in the alendronate group (P = .86).

Furthermore, "denosumab was more potent in suppressing the bone markers at 12 months," Mok said.

Specifically, the percentage decrease in serum PINP (procollagen type I N-terminal propeptide) levels in the denosumab group was significantly greater than in the alendronate group (P = .001). Likewise, the decrease in CTX (C-terminal telopeptide of type I collagen) was significantly greater in the denosumab cohort versus the alendronate cohort (P < .001).

"Dr Mok's study was a well-controlled investigation. The superiority of denosumab was impressive, especially given the small group sizes of 69 and 70," session comoderator Gregg Silverman, MD, professor in the department of internal medicine and the department of pathology at New York University, said when asked for comment.

"However, bone density measurements may not tell the whole story. These results support a bigger and much larger-scale study to confirm that rates of fracture on denosumab are also reduced."

No new symptomatic fractures occurred in either group during the study. The investigators are evaluating for any new radiologic fractures, with results pending.

Mok said "results of our study in Asian patients are largely confirmatory" of a previous 2018 comparison study and a 2019 comparison study, each sponsored by Amgen.

A small sample size, short duration of treatment, and the open-label design were limitations of the study.

The trial was an investigator-initiated study. Mok and colleagues had no relevant financial disclosures. Silverman had no relevant financial disclosures.

SOURCE: Mok CC et al. Arthritis Rheumatol. 2020;72(suppl 10). ACR 2020, Abstract 1442.

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