A novel bioassay for the activity determination of therapeutic human brain natriuretic peptide (BNP)

Development and application of potency assays based on genetically modified cells for biological products

Potency assays are key to the development, registration, and quality control of biological products. Although previously preferred for clinical relevance, in vivo bioassays have greatly diminished with the advent of dependent cell lines as well as due to ethical concerns. However, for some products, the development of in vitro cell-based assay is challenging, or existing method has limitations such as tedious procedure or low sensitivity. The generation of genetically modified (GM) cell line with improved response to the analyte provides a scientific and promising solution. Potency assays based on GM cell lines are currently used for the quality control of biological products including cytokines, hormones, therapeutic antibodies, vaccines and gene therapy products. In this review, we have discussed the general principles of designing and developing GM cells-based potency assays, including identification of cellular signaling pathways and detectable biological effects, generation of responsive cell lines and constitution of test systems, based on the current research progress. In addition, the applications of some novel technologies and the common concerns regarding GM cells have also been discussed. The research presented in this review provides insights for the development and application of novel GM cells-based potency assays for biological products.

A robust reporter assay for the determination of the bioactivity of IL-4R-targeted therapeutic antibodies

Type 2 inflammatory cytokines, including IL-4, IL-5 and IL-13, contribute considerably to the pathogenesis of asthma. Anti-IL-4R monoclonal antibody (mAb) has been approved for the therapeutic treatment of asthma, and many mAbs with the same target are in the different stages of R&D and clinical trials. Bioactivity determination is required to ensure the quality control of mAbs. However, current ELISA and SPR assays or cell-based anti-proliferation assays for IL-4R mAbs are either not mechanism-of-action (MOA) representative or tedious and time consuming. Therefore, we developed a reporter gene assay (RGA) based on the HEK-293 cell line that stably expressed signal transducer and activator of transcription 6 (STAT6) and the luciferase reporter controlled by STAT6 binding elements. Anti-4R mAb could bind to IL-4R, and block the interaction between IL-4 and IL-4R, resulting in the reduction of IL-4 induced STAT6 controlled luciferase expression. After careful optimization of the experiment parameters, the RGA method demonstrated optimal dose-response curve between anti-IL-4R mAb concentration and luciferase expression level. Validation according ICH-Q2 proved the excellent assay performance characteristics of the established RGA, including specificity, accuracy, precision, linearity and range. The established transgenic cell line was stable for the bioactivity determination of anti-IL-4R mAb up to 46 generations, and the RGA was also suitable for the bioactivity determination of anti-IL-4 mAbs, and potentially of anti-IL-13 mAbs. The established RGA could be adopted to determine the bioactivity during the development, characterization, lot release, stability, and comparability studies of anti-IL-4R mAbs.

B-type natriuretic peptide enhances fibrotic effects via matrix metalloproteinase-2 expression in the mouse atrium in vivo and in human atrial myofibroblasts in vitro

B-type natriuretic peptide (BNP) was approved by the US Food and Drug Administration in 2001 for the treatment of heart failure. However, the effects of BNP in clinical applications are controversial and uncertain. Recently, study indicated that high BNP levels are associated with an increased risk of developing atrial fibrillation. In this study, we investigated the direct effects of BNP on TNF-α-induced atrial fibrosis mice, as well as its effects on human atrial myofibroblasts. We found that injecting TNF-α-induced mice with recombinant human BNP enhanced atrial fibrosis via matrix metalloproteinase-2 (MMP-2) expression and collagen accumulation. Furthermore, we found that BNP stimulated MMP-2 expression in human atrial myofibroblasts. Treatment of human atrial myofibroblasts with cycloheximide had no effect on this outcome; however, treatment of cells with MG132 enhanced BNP-induced MMP-2 expression, indicating that protein stability and inhibition of proteasome-mediated protein degradation pathways are potentially involved. Inhibition of SIRT1 significantly decreased BNP-induced MMP-2 expression. Additionally, confocal and coimmunoprecipitation data indicated that BNP-regulated MMP-2 expression are likely to be mediated through direct interaction with SIRT1, which is thought to deacetylate MMP-2 and to increase its protein stability in human atrial myofibroblasts. Finally, we confirmed that SIRT1 is expressed and cytoplasmically redistributed as well as colocalized with MMP-2 in mouse fibrotic atrial tissue. We suggest a possible fibrosis-promoting role of BNP in the atrium, although the antifibrotic properties of BNP in the ventricle have been reported in previous studies, and that the coordination between MMP-2 and SIRT1 in BNP-induced atrial myofibroblasts participates in atrial fibrosis.

Responsive Cells for rhEGF bioassay Obtained through Screening of a CRISPR/Cas9 Library

Bioassay of recombinant protein products is important tests to ensure protein effectiveness. Some recombinant protein products have no cells used in their bioassay but instead use animal models, while others have no suitable method. Here, we developed a method to obtain responsive cells used in bioassay of proteins. After screening of a CRISPR/Cas9 library, we obtained a responsive cell line that grew faster in the presence of rhEGF (recombinant human epidermal growth factor) than that of control cells. We used this cell line for bioassay of rhEGF. This cell line, compared with the control cells, had a 2 day shorter operation time and had lower interference. The responsive cell line is more suitable for use in bioassay of rhEGF.

A rapid reporter assay for recombinant human brain natriuretic peptide (rhBNP) by GloSensor technology

Accurate determination of biological activity is essential in quality control of recombinant human brain natriuretic peptide (rhBNP). In previous study, we successfully developed a genetically modified cell line 293GCAC3-based ELISA assay for rhBNP. But ELISA procedure is still tedious, so this study was aimed to develop a rapid and simple bioassay for rhBNP using GloSensor technology, which provides a platform of flexible luciferase-based biosensors for real-time detection of signaling events in live cells, including cGMP production. A reporter cell line 293GCAGlo-G1 was constructed by transfecting pGloSensor™ 40 F plasmid into 293GCAC3. The reporter assay based on 293GCAGlo-G1 showed high precision with intra-assay CV being 8.3% and inter-assay CV being 14.1%; high accuracy with 80%, 100% and 120% recovery rate being 99.2%, 102.4% and 99.0% respectively; and great linearity with R² of linear fitting equation being 0.99. Besides, no significant difference was found in test results of reporter assay and 293GCAC3-based ELISA assay (paired t test, p = 0.630). All these results suggested that the reporter assay was a viable assay for biological determination of rhBNP.

Synthesis, secretion, function, metabolism and application of natriuretic peptides in heart failure

As a family of hormones with pleiotropic effects, natriuretic peptide (NP) system includes atrial NP (ANP), B-type NP (BNP), C-type NP (CNP), dendroaspis NP and urodilatin, with NP receptor-A (guanylate cyclase-A), NP receptor-B (guanylate cyclase-B) and NP receptor-C (clearance receptor). These peptides are genetically distinct, but structurally and functionally related for regulating circulatory homeostasis in vertebrates. In humans, ANP and BNP are encoded by NP precursor A (NPPA) and NPPB genes on chromosome 1, whereas CNP is encoded by NPPC on chromosome 2. NPs are synthesized and secreted through certain mechanisms by cardiomyocytes, fibroblasts, endotheliocytes, immune cells (neutrophils, T-cells and macrophages) and immature cells (embryonic stem cells, muscle satellite cells and cardiac precursor cells). They are mainly produced by cardiovascular, brain and renal tissues in response to wall stretch and other causes. NPs provide natriuresis, diuresis, vasodilation, antiproliferation, antihypertrophy, antifibrosis and other cardiometabolic protection. NPs represent body's own antihypertensive system, and provide compensatory protection to counterbalance vasoconstrictor-mitogenic-sodium retaining hormones, released by renin-angiotensin-aldosterone system (RAAS) and sympathetic nervous system (SNS). NPs play central roles in regulation of heart failure (HF), and are inactivated through not only NP receptor-C, but also neutral endopeptidase (NEP), dipeptidyl peptidase-4 and insulin degrading enzyme. Both BNP and N-terminal proBNP are useful biomarkers to not only make the diagnosis and assess the severity of HF, but also guide the therapy and predict the prognosis in patients with HF. Current NP-augmenting strategies include the synthesis of NPs or agonists to increase NP bioactivity and inhibition of NEP to reduce NP breakdown. Nesiritide has been established as an available therapy, and angiotensin receptor blocker NEP inhibitor (ARNI, LCZ696) has obtained extremely encouraging results with decreased morbidity and mortality. Novel pharmacological approaches based on NPs may promote a therapeutic shift from suppressing the RAAS and SNS to re-balancing neuroendocrine dysregulation in patients with HF. The current review discussed the synthesis, secretion, function and metabolism of NPs, and their diagnostic, therapeutic and prognostic values in HF.

Regulatory science accelerates the development of biotechnology drugs and vaccines by NIFDC

The Chinese National Institutes for Food and Drug Control (NIFDC) is the national laboratory responsible for the quality control of pharmaceutical products. In recent years, to ensure the quality of biological products and improve the research and development (R&D) of new biological drugs and vaccines, NIFDC conducted a series of regulatory science studies on key technologies for quality control and evaluation, and established a quality control and evaluation platform for biological drugs and vaccines. These studies accelerated the R&D of the biological drugs and vaccines in China and assured their safety and efficacy. In this paper, NIFDC's duties and achievements in the biological drug and vaccine field are summarized.