Safety, tolerability, pharmacokinetics, and pharmacodynamics of recombinant human parathyroid hormone (1-34) in healthy Chinese subjects

Incidence of new fractures in older patients with osteoporosis receiving biosimilar teriparatide or reference products: A retrospective cohort study

AIMS

Biosimilar products have clinical characteristics similar to those of brand-name products and can reduce medical costs. However, the use of biosimilar products for osteoporosis treatments remains limited due to concerns regarding its safety and efficacy. We aimed to clarify the effectiveness and safety of the biosimilar teriparatide compared with those of the reference product using the incidence of new fractures and osteosarcoma as outcomes in osteoporosis patients.

METHODS

This study used the DeSC database, which contains medical claims data for various insurers in Japan. We included patients with osteoporosis aged ≥65 years who newly received either biosimilar teriparatide or the reference products between April 2019 and November 2022. Competing risk analyses were performed with adjustments for patient characteristics. The primary and secondary outcomes were the occurrence of new fractures and osteosarcoma, respectively.

RESULTS

Among 45 861 included patients, 3613 and 42 248 were in the biosimilar and reference product groups, respectively. The median follow-up duration was 439 days. New fractures occurred in 6.7% of patients. Cumulative incidence function curves showed similar risks of new fractures over time in both groups. The cause-specific hazard ratio for new fractures was 0.95 (95% confidence interval: 0.82-1.11) for the biosimilar group compared with that of the reference product group. The incidence of osteosarcoma did not differ significantly between the groups (P = .559).

CONCLUSIONS

The biosimilar teriparatide showed effectiveness and safety comparable with those of the reference products in treating osteoporosis patients. Our results suggest that clinicians need not hesitate to prescribe biosimilar teriparatide for osteoporosis patients.

Biosimilarity Assessment of the Biosimilar Teriparatide Candidate and the Reference Drug in Healthy Subjects

SAL001, a recombinant form of parathyroid hormone, is a biosimilar drug to teriparatide and is planned to be used in osteoporosis treatment. A single-dose, randomized, open-label, 2-way crossover trial was conducted in healthy subjects to compare the pharmacokinetics (PK) and safety between SAL001 and the reference drug. Sixty-four subjects were enrolled in the study, and 61 subjects completed the study. In each period, 20 μg of the test or reference formulation was administered subcutaneously. SAL001 was administered by autoinjector pen, whereas the reference drug was administered by a self-matched injection pen. Serial blood samples were obtained for the analyses of PK and serum calcium concentration. Geometric mean ratios with 90%CIs for the maximum plasma concentration (C_max ) and area under the plasma concentration-time curve (AUC) were estimated. The safety of these 2 formulations was also evaluated. Overall, the 90%CIs for the geometric mean ratios of C_max , AUC from time 0 to the last quantifiable time point, and AUC from time 0 extrapolated to infinity of the test or reference product were within 80.0%-125.0% of biosimilarity criteria. Other PK parameters, serum calcium concentration, and safety profiles had no significant differences between the 2 formulations. SAL001 demonstrated PK similarity to the reference drug, and the serum calcium concentration and safety profiles of SAL001 were also considered comparable to the reference drug.

The first biosimilar approved for the treatment of osteoporosis: results of a comparative pharmacokinetic/pharmacodynamic study

To demonstrate the clinical comparability between RGB-10 (a biosimilar teriparatide) and the originator, a comparative pharmacokinetic trial was conducted. The study was successful in establishing bioequivalence. Marketing authorisation for RGB-10 (Terrosa®) was granted by the European Medicines Agency in 2017.

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_0-tlast) and peak exposure (C_max), 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_0-tlast and C_max, 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_max, 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.

Optimal dosing and delivery of parathyroid hormone and its analogues for osteoporosis and hypoparathyroidism - translating the pharmacology

In primary hyperparathyroidism (PHPT), bone loss results from the resorptive effects of excess parathyroid hormone (PTH). Under physiological conditions, PTH has actions that are more targeted to homeostasis and to bone accrual. The predominant action of PTH, either catabolic, anabolic or homeostatic, can be understood in molecular and pharmacokinetic terms. When administered intermittently, PTH increases bone mass, but when present continuously and in excess (e.g. PHPT), bone loss ensues. This dual effect of PTH depends not only on the dosing regimen, continuous or intermittent, but also on how the PTH molecule interacts with various states of its receptor (PTH/PTHrP receptor) influencing downstream signalling pathways differentially. Altering the amino-terminal end of PTH or PTHrP could emphasize the state of the receptor that is linked to an osteoanabolic outcome. This concept led to the development of a PTHrP analogue that interacts preferentially with the transiently linked state of the receptor, emphasizing an osteoanabolic effect. However, designing PTH or PTHrP analogues with prolonged state of binding to the receptor would be expected to be linked to a homeostatic action associated with the tonic secretory state of the parathyroid glands that is advantageous in treating hypoparathyroidism. Ideally, further development of a drug delivery system that mimics the physiological tonic, circadian, and pulsatile profile of PTH would be optimal. This review discusses basic, translational and clinical studies that may well lead to newer approaches to the treatment of osteoporosis as well as to different PTH molecules that could become more advantageous in treating hypoparathyroidism.