Safety assessment of a novel C-type natriuretic peptide derivative and the mechanism of bone- and cartilage-specific toxicity

Takafumi Yotsumoto,Yasuyuki Abe,Hiroyuki Ogasawara,Yoshiharu Minamitake,Toshimasa Jindo,Ryuichi Nakamura,Tomonari Nishimura,Hiroaki Maeda,Naomi Morozumi,Mayumi Furuya,Kenji Kangawa,Michael Bader

doi:10.1371/journal.pone.0218229

Takafumi Yotsumoto, Yasuyuki Abe + Show 10 more

Open Access

https://doi.org/10.1371/journal.pone.0218229

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Abstract

ASB20123, a C-type natriuretic peptide/ghrelin chimeric peptide, was designed as a novel peptide and demonstrated full agonistic activity for natriuretic-peptide receptor B and a significantly longer half-life in plasma compared with the native peptide. We researched the toxicological profile of ASB20123, the correlation between the morphological change of the epiphyseal plate and bone and cartilage toxicity, and biomarkers to detect the toxicity. ASB20123 was systemically administered to male and female rats at daily dose levels of 0.5, 1.5, and 5.0 mg/kg/day for 4 weeks. In this study, toxicity was observed as changes related to bone and cartilage tissues, and no other toxicological changes were observed in all animals. Next, ASB20123 was administered to 12-month-old rats with a little epiphyseal plate. The toxic changes related to bone and cartilage tissues were not observed in any animal with a closed epiphyseal plate, indicating that the toxic changes were triggered by the growth-accelerating effect on the bone and cartilage. Furthermore, we searched for the biomarker related to the bone and cartilage toxicity using rats treated with ASB20123 at doses of 0.005, 0.05, 0.5, and 5.0 mg/kg/day for 4 weeks. A close correlation between necrosis/fibrosis in the epiphysis and metaphysis and thickness of the epiphyseal plate in the femur was confirmed in this study. A decrease in the bone mineral density (BMD) of the femur also was associated with the appearance of bone toxicity. These results indicated that the toxicity of ASB20123 was limited to bone- and cartilage-specific changes, and these changes were triggered by an excessive growth accelerating effect. Furthermore, our data suggested that the thickness of the epiphyseal plate and BMD could be reliable biomarkers to predict bone toxicity.

Highlights

The C-type natriuretic peptide (CNP) analog is one of the most exciting therapeutic approaches to treat achondroplasia [1]
Toxic changes were observed in the bone and cartilage tissues, and no other toxic changes were observed in all animals
In the histopathological examination, thickening of the epiphyseal plate, which was frequently accompanied by increases in the primary bone and osteoblasts, was observed in the femur and tibia in all the test article-treated groups

Summary

Introduction

The C-type natriuretic peptide (CNP) analog is one of the most exciting therapeutic approaches to treat achondroplasia [1]. The application of C-terminal part of ghrelin resulted in the higher stability of CNP analogs, compared to that of CNP-22 as the native form; it improved their bioactivity as stimulators of endochondral bone growth [9,10,11]. ASB20123, this novel CNP derivative demonstrated full agonistic activity for NPR-B and showed significantly longer half-life in plasma compared with the native forms. NPR-B is expressed in the brain, lung, bone, heart, and ovary. It is expressed at relatively high levels in fibroblasts and vascular smooth muscle cells [15]. We researched the relationship between the specific bone and cartilage toxicity and morphological changes of the epiphyseal plate and reliable biomarkers to detect the toxicity

Materials and methods

Results

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Discussion