The First Biosimilar Approved for the Treatment of Osteoporosis: Results of a Comparative Pharmacokinetic/pharmacodynamic Study

Introduction: Teriparatide, the first bone anabolic agent, is the biologically active fragment of human parathyroid hormone. The imminent patent expiry of the originator will open the door for biosimilars to enter the osteology market, thereby improving access to a highly effective, yet prohibitively expensive therapy.

Methods: Subsequent to establishing comparability on the quality and non-clinical levels between RGB-10, a biosimilar teriparatide, and its reference product (Forsteo®), a randomised, double-blind, 2-way cross-over comparative study (duration: four days) was conducted in 54 healthy women (ages: 18 to 55 years) to demonstrate the pharmacokinetic/pharmacodynamic (PK/PD) equivalence and comparable safety of these products. Extents of exposure (AUC) and peak exposure (C), as measured by means of ELISA, were evaluated as co-primary PK endpoints, and serum calcium levels, as measured using standard automated techniques, were assessed for PD effects. Safety was monitored throughout the study.

Results: The 94.12% CIs for the ratio of the test to the reference treatments, used due to the two-stage design (85.20-98.60% and 85.51-99.52% for AUC and C, respectively), fell within the 80.00-125.00% acceptance range. The calcium PD parameters were essentially identical with geometric mean ratios (GMRs) of 99.93% and 99.87% for AUC and C, respectively. Analysis of the safety data did not reveal any differences between RGB-10 and its reference.

Conclusion: Based on the high level of similarity in the preclinical data and the results of this clinical study, marketing authorisation for RGB-10 (Terrosa®) was granted by the European Medicines Agency (EMA) in 2017.