Objectives: Chronic kidney disease (CKD) complicated by secondary hyperparathyroidism (SHPT) is associated with an increased risk of fragility fractures. Etelcalcetide (EC) is a treatment for SHPT that reduces serum parathyroid hormone (PTH) levels. However, the effects of combined treatment with osteoporosis drugs such as teriparatide (TPTD) remain unclear. This study investigates the combined effects of EC and TPTD on bone in CKD model rats. Methods: The CKD model was established in 8-week-old male Wistar rats by feeding them a 0.75% adenine diet for 4 weeks. At 20 weeks of age, the rats were divided into 4 groups (n = 9–10 in each group): CKD group (vehicle administration), TPTD group (30 μg/kg, 3 times/week), EC group (0.6 mg/kg, daily), and Comb group (TPTD and EC combined). EC was injected for 12 weeks starting at 20 weeks of age, and TPTD was injected for 8 weeks starting at 24 weeks of age. After treatment, the followings were evaluated: bone mineral density, bone strength, biochemical tests, bone and fat histomorphometry, and micro-computed tomography. Results: In CKD model rats, the combination of EC and TPTD was more effective in increasing cortical bone thickness and bone strength and inhibiting porosity. In addition, the combined treatment decreased bone marrow adiposity and fibrosis, and it increased bone mass and improved bone microstructure in trabecular bone. Conclusions With the observed benefits such as improved bone mass, bone strength, structural properties, and bone marrow adiposity, combination therapy may be a potential way to improve bone fragility in CKD.

Real-world data (RWD), such as a health insurance claim database and electronic medical record database, which records daily medical care information, is one of the most important data sources in pharmacoepidemiological studies. In Japan, a post-marketing database study has been added as a new category of post-marketing surveillance since April 2018. It is expected that the post-marketing database studies will be conducted in the actual risk management plan； however, at this point, few have reached the stage of publishing study results. On the other hand, overseas, many database research results using RWD have already been reported. Although it is necessary to keep in mind that there are differences in the characteristics of the databases (e.g., data contents, structures) and the differences in the medical environment between overseas and Japan, we think that critically reviewing these reports has a reference value for the planning, execution, and interpretation of the results in performing post-marketing database studies in Japan. The purpose of this report is to examine the characteristics and cautions of the database studies through a critical review of published articles of overseas RWD studies and to make recommendations that are useful for conducting post-marketing database studies in Japan. We hope this article will become a help in the planning and implementation of future post-marketing database studies.