FRI683 Every Dose Counts: Response To Half The Recommended Dose Of Romosozumab
Authors: Ramchandani Bhanvi Prakash , Mirza Faryal Sardar 
Published: October 2023

Disclosure: B.P. Ramchandani: None. F.S. Mirza: None.

Introduction: Romosozumab (RSB) is a monoclonal antibody that inhibits sclerostin, increases bone formation and decreases bone resorption. It was approved by FDA in 2019 at a dose of 210 mg monthly for 1 year, followed by an anti-resorptive medication. We present a case of a 76 y.o. female with severe osteoporosis and history of intolerance to multiple medications, who was given half the monthly recommended dose of Romo due to extreme concern about side effects. We hereby report the response of her bone density to the treatment. Case Description: A 76-year-old female with history of primary biliary cirrhosis, Sjogren’s syndrome, hemorrhagic duodenal ulcer, s/p subtotal gastrectomy in 1962 presented for evaluation of severe osteoporosis. Fracture history was significant for T11 compression fracture in 2020 requiring kyphoplasty, and a T10 inferior endplate compression fracture requiring vertebroplasty in 2022. Osteoporosis was first diagnosed in 2005. She was intolerant of teriparatide in 2005 (stopped after six months due to nausea, hypercalcemia, cramps, pain in extremities and fatigue). Zoledronic acid (ZA) was administered in 2006 and 2008. Baseline urine telopeptide cross-links (NTx) was low at 18 which decreased to 10 while on ZA and further infusions were held. She declined denosumab and teriparatide was tried again in 2013 that she did not tolerate. She received ZA again in 2016. BMD did not improve on ZA and she declined further infusions. She was physically active and walked daily and was taking calcium citrate, vitamin D and ursodiol during this time. On examination, she was frail and elderly, with BMI of 16.6 mg/kg2. She had mild kyphoscoliosis of the spine with no spinal or paraspinal tenderness. Remainder of the exam was unremarkable. Laboratory evaluation showed normal serum calcium (9.5 mg/dl), albumin (4.1g/dl), Vit D 25-OH (36 mg/ml), bone specific alkaline phosphatase of 22.7 U/L and urine NTx of 23 nm BCE/mm creatinine. Bone density (BMD) in January 2022 showed lumbar spine (LS) BMD of 0.613 g/cm2 (T-score −4.7) and a total hip BMD of 0.575 g/cm2 (T-score −3.4).

She was reluctant to consider any medications due to concern about side effects, but finally agreed to a trial of RSB at half the recommended dose at 105 mg monthly for 12 months. DXA scan a year later showed 17% increase in LS BMD (0.715 g/cm2, T-score -3.9), with stable total hip BMD. She has been transitioned to denosumab, which she was now agreeable to take. Discussion: Our patient showed significant improvement in BMD with half the recommended dose of RSB, comparable to the increase in LS BMD reported in phase 3 trials. She was petite and her weight-based dose was just short of 3 mg/kg body weight. Phase 1 and 2 studies had tried weight based and smaller doses of Romo and showed improvement in BMD. This case highlights the need for additional studies with weight-based dosing of RSB, which may reduce the cost of treatment.

Presentation: Friday, June 16, 2023