Survey of Data Package and Sample Size of Comparative Clinical Studies for Biosimilar Developments from PMDA Assessments.

BACKGROUND: The Japanese biosimilar guideline requires that the sponsors conduct clinical studies such as comparative pharmacokinetic (PK), pharmacodynamic (PD), or efficacy studies. In each biosimilar development, the sponsors consider the clinical data package, and thus clinical data packages vary among biosimilar developments. OBJECTIVES: The aim of this study was to elucidate the clinical data packages for the biosimilars approved in Japan. The details of clinical data packages and sample size for the regulatory approvals of biosimilars in Japan was reported. METHODS: We surveyed the clinical data packages and sample size based on the Pharmaceuticals and Medical Devices Agency (PMDA) website review reports between 2009 and 2023. RESULTS: Twenty-four biosimilars have been approved based on the comparative PK and efficacy studies, 10 biosimilars have been approved based on the comparative PK/PD study, and one biosimilar has been approved based on the comparative efficacy study. Regarding the sample size, comparative PK studies were conducted in healthy volunteers or patients for up to 300 cases, although the majority enrolled only 1-100 cases (68.1%, 32/47). Comparative PD studies enrolling 1-30, 31-60, and 61-90 cases totaled 4, 7, and 4 cases, respectively. Finally, comparative efficacy studies enrolling 1-300, 301-600, and 601-900 totaled 6, 10, and 11 cases, respectively. In particular, the oncology and rheumatology areas were the first and second disease areas recruiting 601-900 patients. CONCLUSION: Large numbers of patients were enrolled to conduct a comparative efficacy study. Efficient biosimilar development should be considered on the basis of the accumulation of scientific understanding of comparable features of biosimilars and their development.

Revisions to the requirement of the Japanese clinical study data for biosimilar developments in Japan.

BACKGROUND: The 'Questions and Answers (Q&A)' document regarding Japanese biosimilar guideline elucidated that Japanese participant enrollment in at least one comparative clinical study was required for the marketing authorization application (MAA) of biosimilars in Japan. RESEARCH DESIGN AND METHODS: To discuss the requirement of Japanese clinical study data for biosimilar development, the trend in comparative clinical studies conducted for approved biosimilars of monoclonal antibodies and fusion proteins was analyzed, and the consistency of the results between the overall population and the Japanese population according to the publicly available information was reviewed. RESULTS: The number of comparative clinical studies enrolling Japanese participants was 25 cases, and the type and percentage were 13 (52%) and 12 (48%) cases of comparative pharmacokinetic study and comparative efficacy study, respectively. In all comparative clinical studies, consistent results between the overall population and the Japanese population were shown. CONCLUSIONS: Our study indicated that Japanese participant enrollment in comparative clinical studies may not always be necessary for biosimilar development when certain conditions are satisfied. This has been described in the revised Q&A document published by the Ministry of Health, Labour and Welfare in January 2024.

Historical Overview of Regulatory Approvals and PMDA Assessments for Biosimilar Products in Japan During 2009-2022.

A biosimilar product is defined as "a biological product that is highly similar to an existing, approved biological product (known as originator or reference product) in terms of structure, function, quality, and clinical efficacy and safety". Recently, biosimilar products have been actively developed around the world, and part of the reason for this is to combat the rapid growth of medical expenses in many countries, including Japan, the United States (US), and Europe. The use of biosimilar products has been promoted as a measure to address this issue. The review of marketing authorization applications for biosimilar products in Japan is conducted by the Pharmaceuticals and Medical Devices Agency (PMDA), which reviews the comparability of the quality, efficacy, and safety based on the data submitted by the applicants. As of December 2022, 32 biosimilar products have been approved in Japan. Through this process, the PMDA has gained much experience and knowledge regarding the development and regulatory approval of biosimilar products; however, details of the regulatory approvals for biosimilar products in Japan have not been reported until now. Therefore, in this article, we present the details of regulatory history and revised guidelines for approval of biosimilar products in Japan, questions and answers, other relevant notifications, and consideration for comparability evaluations for analytical, non-clinical, and clinical studies. In addition, we provide details about the approval history, number, and types of biosimilar products that have been approved between 2009 and 2022 in Japan.

Decorin enhances the proliferation and differentiation of myogenic cells through suppressing myostatin activity.

Decorin, a small leucine-rich proteoglycan, plays an important role in the regulation of cell growth. Our recent study has shown that immobilized decorin in the collagen matrix sequesters myostatin into the extracellular matrix and prevents its inhibitory action to myoblast proliferation in vitro. However, it still remains unclear whether free decorin could affect the proliferation and differentiation of myogenic cells by regulating myostatin activity. In the present study, we generated stable clonal C2C12 myoblasts that were over-expressing decorin, and showed that decorin over-expressing cells had an increased rate of proliferation as compared to control cells. Decorin over-expressing cells formed multi-giant hypertrophic myotubes with an elongated morphology and larger size as compared to control cells, although the initiation of differentiation in decorin over-expressing cells was somewhat delayed as compared to control cells. Western blot analysis demonstrated that MyoD expression in decorin over-expressing cells was lower than that in control cells until 12 h after induction to differentiate. At 48-h differentiation, the expressions of MyoD, p21 and myogenin were dramatically increased in cells that over-expressed decorin. Furthermore, we revealed that over-expression of decorin suppressed the activity of myostatin endogenously synthesized in C2C12 myoblasts and attenuated the signaling of exogenous myostatin. Consistent with these results, knock-down of decorin impairs C2C12 myoblast growth by increasing the sensitivity to exogenous myostatin. These results clearly show that decorin enhances the proliferation and differentiation of C2C12 myoblasts through suppressing myostatin activity.

Decorin expression in quiescent myogenic cells.

Satellite cells are quiescent muscle stem cells that promote postnatal muscle growth and repair. When satellite cells are activated by myotrauma, they proliferate, migrate, differentiate, and ultimately fuse to existing myofibers. The remainder of these cells do not differentiate, but instead return to quiescence and remain in a quiescent state until activation begins the process again. This ability to maintain their own population is important for skeletal muscle to maintain the capability to repair during postnatal life. However, the mechanisms by which satellite cells return to quiescence and maintain the quiescent state are still unclear. Here, we demonstrated that decorin mRNA expression was high in cell cultures containing a higher ratio of quiescent satellite cells when satellite cells were stimulated with various concentrations of hepatocyte growth factor. This result suggests that quiescent satellite cells express decorin at a high level compared to activated satellite cells. Furthermore, we examined the expression of decorin in reserve cells, which were undifferentiated myoblasts remaining after induction of differentiation by serum-deprivation. Decorin mRNA levels in reserve cells were higher than those in differentiated myotubes and growing myoblasts. These results suggest that decorin participates in the quiescence of myogenic cells.

Decorin activates Akt downstream of IGF-IR and promotes myoblast differentiation.

Decorin, a small leucine-rich proteoglycan, plays an important role in cellular activities through modification of growth factors. It also acts as a signaling molecule to non-muscle cells through epidermal growth factor receptor or insulin-like growth factor I receptor (IGF-IR). However, it is unclear if decorin acts as a signaling molecule to myogenic cells. In this study, we investigated the effect of decorin on the differentiation of myoblasts and the signaling via IGF-IR to myogenic cells. C2C12 myoblasts cultured in media containing decorin for 72 h showed more extensive formation of multinucleated myotubes than control cells cultured in the same media without decorin. The protein expressions of myogenin and myosin heavy chian were higher in decorn-treated cells than in control cells. These results suggest that decorin enhances the differentiation of myoblasts. Western blot analysis and immunocytochemistry showed that IGF-IR was expressed in myoblasts and myotubes. Furthermore, Akt, which is downstream of IGF-IR, was more phosphorylated in myoblasts cultured in media containing decorin than those in media without decorin. These results suggest that decorin activates Akt downstream of IGF-IR and enhances the differentiation of myogenic cells.

Laminin binds to myostatin and attenuates its signaling.

Myostatin is a growth and differentiation factor and acts as a negative regulator of skeletal muscle mass. Although the mechanism whereby myostatin controls muscle cell growth is mostly clarified, the regulation of myostatin activity after its secretion into the extracellular matrix (ECM) is still unclear. In the present study, we investigated the interaction between laminin and myostatin and the effect of laminin on myostatin signaling in vitro. The surface plasmon resonance assay showed that laminin bound to mature myostatin and activin receptor type IIB (ActRIIB), but did not bind to latency-associated protein, which remains non-covalently linked to mature myostatin. Furthermore, kinetic analysis demonstrated that the affinity of mature myostatin for laminin was similar to that for ActRIIB. Next, we examined the action of laminin on the myostatin signaling pathway using a conventional reporter assay. The luciferase activity of myostatin-treated cells was repressed significantly (P < 0.05) by coincubation of laminin. These results suggest that laminin has a potential to regulate myostatin activity through binding to mature myostatin and/or its receptor ActRIIB.

Interaction between myostatin and extracellular matrix components.

Myostatin, a member of the TGF-beta superfamily, is a negative regulator of skeletal muscle mass. We have recently demonstrated that decorin binds to myostatin in vitro, and that immobilized decorin within the collagen matrix prevents myostatin-mediated inhibition of myoblast proliferation. However, little is known about other ECM molecules that bind to myostatin and modulate its activity. Thus, in the present study, we investigated the interaction of several other ECM molecules with myostatin. We here show that fibromodulin, fibronectin and laminin bind to myostatin in the presence of Zn(2+) with a dissociation constant (K(D)) of 10(-10) approximately 10(-8) mol/L. Fibromodulin shows the highest affinity for myostatin among them. These results suggest that these ECM molecules may modulate myostatin activity like decorin does.

Inhibition of matrix metalloproteinases suppresses the migration of skeletal muscle cells.

Skeletal muscle satellite cells are quiescent stem cells that localized between the plasmalemma and the basement membrane of muscle fiber. When muscle is injured, satellite cells are activated, migrate to the injured site and contribute to the regeneration of muscle. However, little is known about the mechanism by which satellite cells migrate underneath the basement membrane. To clarify this, we investigated the effect of MMP inhibition on the migration of C2C12 muscle cells in vitro using a time-lapse imaging system. The migration speed of cells cultured with an MMP-inhibitor reagent was significantly lower (P<0.01) than the control cultured without an inhibitor reagent. The persistency index was significantly higher (P<0.01) in cells cultured with an inhibitor than in those without an inhibitor. Furthermore, MMP-3 knockdown cells migrated faster than control cells. These results strongly suggest that MMPs synthesized in skeletal muscle cells play an important role in the migration of these cells.

Spatiotemporal expression of decorin and myostatin during rat skeletal muscle development.

Decorin, a small leucine-rich proteoglycans, plays an important role in tissue morphogenesis through the regulation of collagen fibrillogenesis and the modulation of some growth factors. Our recent study has shown that decorin binds to myostatin, a negative regulator of skeletal muscle mass, and modulates its inhibitory action to myogenic cell growth in vitro. However, it still remains unclear whether decorin binds to myostatin in vivo during the development of skeletal muscle. To clarify this, we investigated the spatiotemporal expression of decorin and myostatin in rat skeletal muscle by RT-PCR and immunohistochemistry. Decorin mRNA abundance in fetal skeletal muscle was significantly higher than those in neonates and adults (P<0.05). Decorin mRNA expression decreased drastically at birth, and thereafter gradually up to 9 weeks of age. The mRNA expression pattern of myostatin was quite similar to that of decorin during prenatal and postnatal development of rat skeletal muscle. Immunohistochemical analysis demonstrated that myostatin was located in the muscle fibers, and that decorin was located in the periphery of muscle fibers in fetal rat skeletal muscle. Taken together with our previous data, these results suggest that decorin binds myostatin and sequesters it in the ECM during the development of rat skeletal.

Decorin binds myostatin and modulates its activity to muscle cells.

Myostatin, a member of TGF-beta superfamily of growth factors, acts as a negative regulator of skeletal muscle mass. The mechanism whereby myostatin controls the proliferation and differentiation of myogenic cells is mostly clarified. However, the regulation of myostatin activity to myogenic cells after its secretion in the extracellular matrix (ECM) is still unknown. Decorin, a small leucine-rich proteoglycan, binds TGF-beta and regulates its activity in the ECM. Thus, we hypothesized that decorin could also bind to myostatin and participate in modulation of its activity to myogenic cells. In order to test the hypothesis, we investigated the interaction between myostatin and decorin by surface plasmon assay. Decorin interacted with mature myostatin in the presence of concentrations of Zn(2+) greater than 10microM, but not in the absence of Zn(2+). Kinetic analysis with a 1:1 binding model resulted in dissociation constants (K(D)) of 2.02x10(-8)M and 9.36x10(-9)M for decorin and the core protein of decorin, respectively. Removal of the glycosaminoglycan chain by chondroitinase ABC digestion did not affect binding, suggesting that decorin could bind to myostatin with its core protein. Furthermore, we demonstrated that immobilized decorin could rescue the inhibitory effect of myostatin on myoblast proliferation in vitro. These results suggest that decorin could trap myostatin and modulate its activity to myogenic cells in the ECM.