Current therapeutic strategies for the management of osteoporosis in postmenopausal women aim to reduce the risk of fractures with the use of either antiresorptive agents which reduce the rate of bone resorption (bisphosphonates, selective estrogen receptor modulators, estrogen and progestogens, denosumab) or anabolic agents which increase bone formation (teriparatide, abaloparatride, romosozumab) [1, 2].

Anti-resorptive agents, particularly bisphosphonates, are commonly used as first-line agents but are associated with certain limitations and adverse effects with long-term use [3, 4]. More recently, development of the osteoanabolic therapy, teriparatide, abaloparatide and romosozumab, has expanded the range of treatment options [5, 6] and has offered the opportunity to evaluate use of the different classes of therapeutic compounds (antiresorptive and osteoanabolic) in combination or sequentially to optimize clinical efficacy especially in patients at very high risk of fracture [7].

Teriparatide is a recombinant human parathyroid hormone (PTH 1–34) analog originally approved in the USA in 2002 and in Europe in 2003, based on the results of a Phase 3 pivotal study, the Fracture Prevention Trial [FPT]), showing it to be effective in reducing the risk of vertebral and non-vertebral fractures and increasing bone mineral density (BMD) in postmenopausal women with osteoporosis [8, 9]. The FPT follow-up study showed that 18 months after discontinuation of teriparatide treatment, the reduction in vertebral fracture risk was still evident [10].

More recently, the VERO study compared the anti-fracture efficacy of teriparatide and the oral bisphosphonate, risedronate, in postmenopausal women with severe osteoporosis using the incidence of new vertebral fractures as the primary outcome measure [11]. Results showed that the risk of new vertebral and clinical fractures was significantly lower in patients treated with a once-daily subcutaneous injection of teriparatide than in those treated with oral risedronate.

Since the expiration of the patent for the original teriparatide in 2019, several biosimilar compounds have been developed some of which have been granted marketing authorization. In January 2017, the first biosimilar products, RGB-10), were approved by the European Medicines Agency (EMA) based on preclinical confirmation of their structure, purity and biological activity, and the results of a randomized, double-blind, 2-way cross-over pharmacokinetic/pharmacodynamic study in 54 healthy women [12,13,14]. The biosimilar products were approved for the same indications as reference teriparatide, namely treatment of osteoporosis in postmenopausal women and in men at increased risk of fracture and for osteoporosis associated with sustained systemic glucocorticoid therapy in women and men at increased risk for fracture.

This retrospective study evaluates for the first time in a real-world setting the comparative efficacy of a teriparatide biosimilar (RGB-10) with reference teriparatide in reducing measures of osteoporosis in a population of postmenopausal women with osteoporosis at very high fracture risk using multiple assessment methods. Dual-energy x-ray absorptiometry (DXA) and 3D-SHAPER® imaging were used to determine bone mineral density comprising (BMD), while trabecular bone scores (TBS), quantitative ultrasound (QUS), and high-resolution peripheral quantitative computed tomography (HRpQCT) imaging of the radius and tibia were undertaken to evaluate bone microarchitecture and fracture risk.