THU455 Sclerostin Inhibitor Use In The Medical Management Of Osteogenesis Imperfecta Type III
Authors: Lundholm Michelle Diane , Derkyi Alberta , Talvacchio Sara , Marini Joan Carol , Khan Leila Zeinab 
Published: October 2023

Disclosure: M.D. Lundholm: None. A. Derkyi: None. S. Talvacchio: None. J.C. Marini: Other; Self; Ultragenyx, Amgen Inc. L.Z. Khan: None.

Background: Osteogenesis imperfecta (OI) is a rare collagen-related hereditary skeletal disorder with an increased fracture risk from minimal trauma, short stature, and bone deformity. OI is associated with defects in collagen structure or synthesis, high bone turnover, and paradoxical bone hypermineralization. The optimal medical therapies for bone health in these patients are unknown. Clinical Case: A 27-year-old woman with OI presented to clinic for bone health. She was diagnosed with OI type III by phenotype, collagen biochemistry, and genetic analyses (heterozygous for a COL1A1 Gly187Ala substitution) following fractures at age 4 mos. She experienced dozens of fractures, has had orthopedic hardware in bilateral femora, left tibia, humerus, and radius, and right tibia, as well as spine fusion at age 7 yrs. She had not fractured in over 3 yrs which she attributed to the stability of her automatic wheelchair. She had no family history of OI and had been in studies at the NIH; from ages 6-9 yrs she received pamidronate (1 mg/kg/cycle q3m) with BMD improvement. Presently, her vitals were normal, with height of 3’6” (25-50th percentile for type III OI females) and weight of 64 lbs (BMI 25.5 kg/m2). On exam she had blue sclera, midface hypoplasia, dentinogenesis imperfecta, severe kyphosis and scoliosis, and a barrel chest. She had normal calcium, PTH, and 25-OH vitamin D levels. Skull CT showed 1 mm increase in basilar invagination (16 to 17 mm). DEXA demonstrated progressive decline in radial BMD from 0.671 g/cm2 to 0.625 g/cm2 over 3 yrs (z-score -0.4 to -1.1) into the osteopenic range. For worsening bone disease, she is starting romosozumab 210 mg monthly. Discussion: While several agents increase BMD in OI, there are no placebo-controlled studies to show an effect on fracture rate. Bisphosphonates including pamidronate are used most commonly, with increased areal BMD, decreased bone turnover, but also increased mineralization of already brittle bone. Overall, two Cochran reviews failed to support decreased fracture rates from bisphosphonates, and there is risk of adynamic bone with chronic use. There is even less evidence for use of denosumab which is additionally associated with a rebound effect upon discontinuation. Sclerostin inhibitors are the newest agents with both anabolic and antiresorptive effects and good results in OI mouse models. Phase 2 data with sestrusumab showed increased BMD and decreased bone turnover. Ongoing studies are looking at sclerostin inhibitor use in adults and adolescents. From a practical standpoint, romosozumab has a shorter effect with quicker offset than bisphosphonates if needed to stop for fracture healing. Conclusion: Sclerostin inhibitors are an option for the medical treatment of OI. Further investigation is needed to determine long-term safety, optimal duration, and use of sclerostin inhibitors in combination with antiresorptive agents in OI.

Presentation: Thursday, June 15, 2023