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Testing for the erythropoiesis-stimulating agent Sotatercept/ACE-011 (ActRIIA-Fc) in serum by means of Western blotting and LC-HRMS: Testing for Sotatercept/ACE-011 in serum by Western blotting and LC-HRMS
Abstract
Sotatercept (formerly ACE-011) is a glycosylated, dimeric fusion protein composed of the extracellular domain of the human activin receptor type IIA (ActRIIA) and the Fc region of human IgG1. The protein-based drug candidate acts as ligand trap which competitively binds to activin A and other members of the transforming growth factor beta superfamily, thus blocking signalling through ActRIIA. Since the inhibition of activin A was found to significantly increase bone formation and quality, Sotatercept was originally developed for the treatment of diseases involving bone loss. But as the protein therapeutic also stimulates erythropoiesis by a mechanism independent from the EPO receptor, it has been evaluated for the treatment of anaemia in rare blood diseases such as beta thalassemia. Due to its positive effects on erythropoiesis and bone formation, Sotatercept may also be misused as performance-enhancing agent in sports. Within this study, two complementary detection assays for Sotatercept and related ActRIIA-Fc fusion proteins in serum samples were developed. While the first assay combines affinity purification and Western blotting to generically detect ActRIIA-Fc fusion proteins irrespective of their amino acid sequence, the LC-HRMS method is highly specific for proteolytic peptides originating from the receptor and Fc domain of Sotatercept. Both approaches can readily be modified to include other pharmaceutical proteins such as therapeutic antibodies, and serve as proof-of-concept for the capability of the approach to detect TGF-β inhibitors and Fc fusion proteins in doping control serum samples.
... After the pcDNA-Activin A was transfected into GCTB stromal cells, the cells were then incubated with 10 ng/mL TGF-β2 for 1 day. ActRIIA-Fc can block the binding of Activin A to type II receptors [21]. The GCTB stromal cells were treated with 250 nM ActRIIA-Fc for 1 day. ...
... As exhibited in Fig. (7C), compared with the pcDNA-NC group, TGF-β2 treatment elevated p-Smad2 and p-Smad3, while Activin A overexpression decreased p-Smad2 and p-Smad3 protein levels (Fig. 7D). ActRIIA-Fc has been found to block the binding of Activin A to type II receptors [21]. After the GCTB stromal cells were treated with HCG and/or ActRI-IA-Fc, ActRIIA-Fc elevated p-Smad2 and p-Smad3 (Fig. 7E); quantitative results of p-Smad2/Smad2 and p-Smad3/Smad3 are shown in Fig. (7F). ...
Background: Giant cell tumor of bone (GCTB) is a locally aggressive bone tumour aggravated by stromal cell proliferation and metastasis.
Objective: We investigated the mechanism of action of human chorionic gonadotropin (HCG) in mediating GCTB proliferation and invasion.
Methods: The expression of HCG was quantified using quantitative real-time PCR. After the primary stromal cells were isolated and identified, the function of HCG in GCTB was estimated using the cell counting kit-8, flow cytometry, scratch experiment, transwell assay, Western blot, and immunofluorescence. Moreover, the mechanism of HCG was assessed through western blotting.
Results: HCG expression was decreased in clinical tissue samples from patients with GCTB. We validated that HCG repressed stromal cell proliferation, migration, invasion, autophagy, and epithelial-mesenchymal transition (EMT) and promoted cell apoptosis in GCTB. We also verified that HCG repressed the autophagy and EMT of stromal cells through the Smad signaling axis in GCTB. HCG inhibited the transduction of the Smad signaling pathway by restraining the binding of the TGF-β II receptor to ligand Activin A.
Conclusion: HCG restrained the Smad signaling pathway by antagonizing TGF-β signaling in GCTB. HCG may serve as a useful patent to treat GCTB.
... As in earlier studies, [19][20][21][22] a protocol based on the manufacturer's instructions was used for the preparation of the NHS Magnetic Sepharose beads (GE Healthcare, Solingen, Germany). In brief, 25 μl of the medium slurry were transferred to an Eppendorf tube and the storage solution was removed by using a magnetic rack. ...
Cytokines of the transforming growth factor beta (TGF‐β) superfamily such as myostatin and activin A are considered as key regulators of skeletal muscle mass. In vivo, their activity is controlled by different binding proteins such as follistatin (FST), whose interaction with the circulating growth factors prevents activation of the activin type II receptors. FST‐based protein therapeutics are therefore not only promising drug candidates for the treatment of muscular diseases but also potential performance‐enhancing agents in sports.
Within this study, two complementary detection assays for FST‐based inhibitors of the TGF‐β signaling pathways in doping control serum and plasma samples were developed by using both monomeric FST and dimeric FST‐Fc fusion proteins as model compounds. The initial testing procedure is based on immunoaffinity purification, tryptic digestion, and LC‐HRMS/MS, offering high specificity by targeting tryptic signature peptides of FST. As the glycoprotein is also produced endogenously, the confirmation method employs immunoaffinity purification, sodium dodecyl sulfate polyacrylamide gel electrophoresis, and Western blotting in order to detect the intact proteins and differentiate synthetic FST‐Fc constructs from naturally occurring FST isoforms. Both assays were found to be highly specific with an estimated detection limit of 10 ng/ml.
Moreover, a commercial sandwich enzyme‐linked immunosorbent assay was used to determine endogenous FST values. The detected FST serum levels of healthy volunteers were found below 5 ng/ml, which is in accordance with reference values from the literature and below the doping control detection methods' limit of detection (LOD).
The presented assays expand the range of available tests for emerging doping agents, and the initial testing procedure can readily be modified to include further protein drugs.
... Following publication of Walpurgis et al, [1] additional, relevant information has been obtained: Diagnostic peptides selected for the mass spectrometric identification of Sotatercept/ACE-011 are listed in Table 2 of the main paper. They comprise five tryptic peptides originating from the receptor domain and two signature peptides located in the Fc fragment of the fusion protein. ...
An increasing number of novel Fc‐fusion proteins and monoclonal antibodies (mAbs) are being developed as therapeutic agents for treating various diseases. Among these, there are inhibitors of the activin Type II receptor (ActRIIA and ActRIIB) signaling pathways and mAbs against nerve growth factor (NGF), which may be misused for performance enhancement in horseracing and equestrian sports. This study is aimed at developing a generic detection method for doping control analysis of nine targeted proteins, each containing the Fc domain of human IgG or IgG from other species in equine plasma, namely, three recombinant Fc‐fusion proteins (sotatercept, follistatin‐Fc (FST‐Fc), and erythropoietin‐Fc (EPO‐Fc)) and six mAbs (bimagrumab, domagrozumab, garetosmab, landogrozumab, bedinvetmab (Librela), and frunevetmab (Solensia)). A generic workflow has been developed, involving affinity purification with commercially available Protein A magnetic beads followed by tryptic digestion and detection of 20 targeted peptides (with 2–3 diagnostic peptides for each targeted protein) using capillary flow high‐performance liquid chromatography–high‐resolution tandem mass spectrometry (HPLC‐HRMS). The method identified all nine targeted proteins in spiked equine plasma with adequate sensitivity and precision, and for the first time, bedinvetmab (Librela) was detected and identified in plasma for at least 34 days after a single subcutaneous administration (0.5 mg/kg) to a Thoroughbred horse. The results have demonstrated the method's applicability to equine doping control. This generic method involving affinity purification by Protein A has provided a pragmatic and effective approach to cope with the doping control of novel Fc domain–containing proteins.
Detection and monitoring of biomarkers related to doping is particularly suitable for the development of analytical strategies dedicated to indirect detection of banned substances. Previous studies in horses have already allowed the investigation of transcriptomic biomarkers in equine blood associated with reGH and rHuEPO administrations. Our most recent developments continue to focus on the discovery and monitoring of transcriptomic biomarkers for the control of ESAs, and a collaborative study with WADA‐accredited doping control laboratories has recently been initiated to conduct a pilot study. In humans, three mRNAs (ALAS2, CA1, and SLC4A1) were previously observed to be differentially expressed after blood doping and were associated with immature red blood cells, the so‐called circulating reticulocytes. In horses, circulating reticulocytes are rarely observed even after rHuEPO administration. With the improved primers that detect the equine orthologues of the human mRNAs from the ALAS2, CA1, and SLC4A1 genes, we can now report the first evidence of the detection of the three biomarkers in equine blood. In addition, an upregulation of the mRNA levels of the three genes was observed after analysis of blood samples collected from MirCERA‐treated animals, with kinetics similar to those previously documented in humans. Our data suggest that ALAS2 and CA1 are promising indirect biomarkers for the detection of recombinant EPO abuse in horses, as observed in humans.
Due to the presumed lipolytic and anabolic properties, the misuse of human growth hormone (hGH) and its synthetic analogs in sports is prohibited both in‐ and out‐of‐competition. Within this research project, the detectability of somatrogon, a recombinant fusion glycoprotein of 22 kDa hGH and the C‐terminal peptide (CTP) of the human chorionic gonadotropin (hCG) β‐subunit, with current WADA‐approved doping control assays for hGH and hCG was investigated. For that purpose, cross‐reactivity tests and a somatrogon administration study were conducted, and only “Kit 2” of the GH isoform differential immunoassays proved applicable to the detection of somatrogon administration in serum. In urine, the immunoassay specific for total hCG yielded presumptively positive findings for several post‐administration samples, which can probably be attributed to the presence of an immunoreactive fragment of the hCG β‐subunit. As the detectability of somatrogon with these approaches was found to be limited, a highly specific detection assay (LOD: 10 ng/mL) for the drug in serum samples was developed by using affinity purification with GH receptor (GHR)‐conjugated magnetic beads, proteolytic digestion, and liquid chromatography high‐resolution tandem mass spectrometry (LC‐HRMS/MS). Following optimization, the approach was comprehensively characterized, and authentic post‐administration serum samples were successfully analyzed as proof‐of‐concept, indicating a detection window of at least 96 h. Consequently, the presented method can be employed to confirm the presence of somatrogon in serum samples, where only “Kit 2” of the currently used immunoassay kits yielded an abnormally high Rec/Pit ratio.
Introduction:
The analysis of doping control samples is preferably performed by mass spectrometry, because obtained results meet the highest analytical standards and ensure an impressive degree of reliability. The advancement in mass spectrometry and all its associated technologies thus allow for continuous improvements in doping control analysis.
Areas covered:
Modern mass spectrometric systems have reached a status of increased sensitivity, robustness, and specificity within the last decade. The improved sensitivity in particular has, on the other hand, also led to the detection of drug residues that were attributable to scenarios where the prohibited substances were not administered consciously but rather by the unconscious ingestion of or exposure to contaminated products. These scenarios and their doubtless clarification represent a great challenge. Here, too, modern MS systems and their applications can provide good insights in the interpretation of dose-related metabolism of prohibited substances. In addition to the development of new instruments itself, software-assisted analysis of the sometimes highly complex data is playing an increasingly important role and facilitating the work of doping control laboratories.
Expert opinion:
The sensitive analysis and evaluation of a higher number of samples in a shorter time is made possible by the ongoing developments in mass spectrometry.
Dried blood spot (DBS) based microsampling is an emerging approach that requires a minimally invasive procedure. It is being increasingly used in metabolic screening, therapeutic drug monitoring, pharmacokinetic, diagnostic, pharmaco-toxicology and proteomic studies. DBS is a promising technique in clinical research due to its simplicity, convenience of storage and transportation, and compatibility with different analytical methods. Although DBS has been progressively established in numerous analytical domains concerning small molecules, it is still relatively less explored for peptides and proteins. Comprehensive literature discussing aspects of the usefulness of DBS sampling for protein and peptide bioanalysis is not reported in any literature till date. For the analysis of proteins and peptides, selection of a DBS card has a significant impact on analytical accuracy. This review specifically discusses recent technological advancements and difficulties associated with DBS sampling for proteins and peptides. Selective modifications on DBS cards for proteins and peptides have also been discussed. The assumptions and facts about use of DBS in comparison with traditional methods have been explained. While DBS has many benefits, certain difficulties associated with the technique can not be ignored. The article covers critical discussions on available DBS cards, extraction procedures, storage recommendations along with challenges and strategies to overcome them. Considering all the factors, it can be inferred that DBS bio-sampling need to go through more application based research and development before its effective application in clinical studies. However, it has all the potential to replace whole blood sampling approach in clinical applications in near future.
Activin receptor type IIA and type IIB fusion protein have been designed to sequester circulating molecules of the TGF‐β superfamily and inactivate their actions. Members of this superfamily have been reported as essential regulators of erythropoiesis by triggering the formation of activated ternary complexes containing different combinations of type I and type II receptors which can limit RBC production by accelerating erythroid differentiation and inhibiting erythroid progenitor expansion. The recent approval of Luspatercept for the treatment of anemia associated to transfusion‐dependent MDS and Beta‐thalassemia in afflicted patients means that it can now pose a real threat of being abuse in sport for its ability to stimulate erythropoiesis. Several methods for the detection of these molecules in blood have been proposed for the purpose of sport antidoping control. Here we propose the detection of the ActRIIA‐Fc and ActRIIB‐Fc fusion proteins by automated capillary Western immunoassay (Simple Western). The use of these immunoassays for the detection of protein targets has become widespread in the recent years. The work presented here demonstrates that this methodology enables a versatile, rapid, and sensitive detection of activin ligand traps in blood samples, either plasma, serum or DBS. Preliminary results indicate that detection in urine samples is also possible. The option to use different antibodies allows the possibility to use this method as an initial testing procedure as well as a confirmation procedure. Finally, results coming from an administration study confirm that the method is suitable for routine analysis.
Performance and image enhancing drugs are misused by top athletes, young people and amateurs like bodybuilders. Their misuses lead to adverse analytical findings in sport but also physical and mental health risks. Anti-doping laboratories must set up analytical strategies and develop precise, robust and sensitive methods to detect all analytes prohibited by the World Anti-Doping Agency (WADA). In recent years, high resolution mass spectrometry (HRMS) systems have emerged and are gradually replacing more traditional systems for screening and quantification. The targeted compounds in this review are the drugs prohibited by the WADA in-and out-of competition and glucocorticoids. Advanced technologies were applied for anti-doping, forensic and clinical purposes. The contribution of HRMS in the analysis of doping products allows a retrospective analysis to detect new metabolites in order to increase the detection windows and to identify new synthetic products. These systems are also used for new applications like study of metabolomics, characterisation of metabolites and applications in alternative matrices (hair, dried blood spots). Moreover, the misuses of these substances lead the consumers to purchase on the black market.
For at least the first three decades since its advent, proteomics has exclusively largely belonged to a clinical, diagnostic, or fundamental biology context. However, the range and the significance of information that proteomes can disclose have led this discipline to be also applied to forensics, ranging from human identification from hair samples, identification of bodily fluids, and microbial forensics to doping investigations. Fingermarks are a relatively new specimen for proteomic studies with any form of proteomic investigation only appearing in 2012 with the analysis of intact peptides and small proteins in situ published by the research group at Sheffield Hallam University. It was not until 2015 that further developments allowed bottom-up proteomics to be also applied directly in situ. While in situ proteomics of fingermarks has many advantages, encompassing simplified sample preparation protocols, speed and the opportunity to perform molecular imaging analyses, this area remains under-investigated. This is probably due to the unique challenges of working with fingermark specimens. The relatively low protein content and the predominantly eccrine origin of fingermarks have been shown to severely impact protein detection at least when the "intact" protein approach is used both in full scan and using a top down approach. In this chapter, advantages, application, challenges and perspective of in situ fingermark proteomics are discussed and compared with classic approaches.
The TGF‐β cytokine myostatin is considered as one of the key regulators of skeletal muscle mass. Consequently, specific inhibitors of the growth factor and its signaling pathways are promising therapeutics for the treatment of muscle wasting disorders as well as potential performance‐enhancing agents in sports. Domagrozumab is a humanized monoclonal antibody which neutralizes the circulating cytokine, thus preventing receptor activation. Within this study, two complementary detection assays for Domagrozumab from serum were developed by using ammonium sulfate precipitation and immunoaffinity purification either in combination with tryptic digestion and LC‐HRMS or Western blotting. While the LC‐HRMS assay is highly specific for diagnostic peptides originating from both the heavy and the light chain of the antibody, the second assay is capable to generically detect intact therapeutic proteins comprising of a human Fc domain and exhibiting high specificity for dimeric myostatin/GDF‐11. Following optimization, both assays were comprehensively characterized. They can readily be modified to include further protein drugs and will expand the range of available tests for emerging myostatin inhibitors.
Aim: sotatercept is a therapeutic Fc-fusion protein with erythropoiesis-stimulating activity. Due to a potential abuse of the drug by athletes in professional sports, a sensitive detection method is required. In sports drug testing, alternative matrices such as dried blood spots (DBS) are gaining increasing attention as they can provide several advantages over conventional matrices. Materials & methods: Herein, two complementary LC-high-resolution mass spectrometry (HRMS) detection methods for sotatercept from DBS, an initial testing procedure (ITP) and a confirmation procedure (CP) were developed and validated for the first time. Both methods comprise an ultrasonication-assisted extraction, affinity enrichment, proteolytic digestion and HRMS detection. Results & conclusion: For the multianalyte ITP, artificial samples fortified with sotatercept, luspatercept and bimagrumab, and authentic specimens containing bimagrumab were successfully analyzed as proof-of-concept. The validated detection methods for sotatercept are fit for purpose and the ITP was shown to be suitable for the detection of novel IgG-based pharmaceuticals in doping control DBS samples.
Mass spectrometry-based proteomics has been a useful tool for addressing numerous questions in basic biology research for many years. This success, combined with the maturity of mass spectrometric instrumentation, the ever-increasing availability of protein sequence databases derived from genome sequencing, and the growing sophistication of data analysis methods, places proteomics in a position to have an important role in biological forensics. Because proteins contain information about genotype (sequence) and phenotype (expression levels), proteomics methods can both identify biological samples and characterize the conditions that produced them. In addition to serving as a valuable orthogonal method to genomic analyses, proteomics can be used in cases where nucleic acids are absent, degraded, or uninformative. Mass spectrometry provides both broad applicability and exquisite specificity, often without customized detection reagents like primers or antibodies. This review briefly introduces proteomics methods, and surveys a variety of forensic applications (including criminal justice, historical, archaeological, and national security areas). Finally, challenges and crucial areas for further research are addressed.
Therapeutic proteins are a continuously growing class of pharmaceuticals and comprise several drug candidates with potential performance‐enhancing properties. Especially activin receptor competitors such as the ActRII‐Fc fusion proteins Sotatercept (ActRIIA‐Fc) and Luspatercept (modified ActRIIB‐Fc) have the potential for being misused as doping agents in sports as they were found to inhibit negative regulators of late‐stage erythropoiesis.
Within this study, ammonium sulfate precipitation, immunoaffinity purification, tryptic digestion, and LC‐MS/MS were employed to develop an assay for the combined detection of Sotatercept and Luspatercept in doping control serum samples. The assay was optimized, comprehensively characterized, and found to be fit‐for‐purpose for an application to sports drug testing. It complements existing tests for ActRII‐Fc fusion proteins and expands the range of available detection methods for novel protein therapeutics.
Bone morphogenetic proteins (BMPs) are secreted cytokines that were initially discovered on the basis of their ability to induce bone. Several decades of research have now established that these proteins function in a large variety of physio‐pathological processes. There are about 15 BMP family members, which signal via three transmembrane type II receptors and four transmembrane type I receptors. Mechanistically, BMP binding leads to phosphorylation of the type I receptor by the type II receptor. This activated heteromeric complex triggers intracellular signaling that is initiated by phosphorylation of receptor‐regulated SMAD1, 5 and 8 (also termed R‐SMADs). Activated R‐SMADs form heteromeric complexes with SMAD4, which engage in specific transcriptional responses. There is convergence along the signaling pathway and besides the canonical SMAD pathway, BMP‐receptor activation can also induce non‐SMAD signaling. Each step in the pathway is fine‐tuned by positive and negative regulation and crosstalk with other signaling pathways. For example, ligand bioavailability for the receptor can be regulated by ligand‐binding proteins that sequester the ligand from interacting with receptors. Accessory co‐receptors, also known as BMP type III receptors, lack intrinsic enzymatic activity but enhance BMP signaling by presenting ligands to receptors. In this review, we discuss the role of BMP receptor signaling and how corruption of this pathway contributes to cardiovascular and muscle‐skeletal diseases and cancer. We describe pharmacological tools to interrogate the function of BMP receptor signaling in specific biological processes and focus on how these agents can be used as drugs to inhibit or activate the function of the receptor, thereby normalizing dysregulated BMP signaling.
This article is protected by copyright. All rights reserved.
We recently published two protocols for the detection of Sotatercept (ACE‐011, ACVR2A‐Fc) and Luspatercept (ACE‐536, ACVR2B‐Fc) in human serum. Both methods used covalently immobilized antibodies on agarose beads for immunoprecipitation and SAR‐PAGE/Western blotting for detection. Disadvantages were the relatively high amount of antibody required per sample (10 μg) and the need of a secondary antibody for the final detection. The updated protocols overcome these limitations by antigen‐antibody complex formation in solution followed by capture of the complex with anti‐antibody coated magnetic beads. They also omit the secondary antibody incubation step by usage of biotinylated primary antibodies, which can be directly incubated with streptavidin‐HRP. Thus, the new protocols are faster, simpler, and cheaper and offer comparable sensitivities.
Iso‐Electric Focusing (IEF) was the first method established to discriminate endogenous and recombinant erythropoietins (rEPOs) and is still approved by the World Anti‐Doping Agency (WADA) as Initial Testing Procedure to detect erythropoiesis stimulating agents (ESAs) in doping control samples. However EPO‐Fc, one of the prohibited rEPOs designated by WADA, is not detectable with the actual IEF conditions. Other newly developed ESAs luspatercept and sotatercept, both activin receptor type II‐Fc fusion proteins (ActRII‐Fc), are also now prohibited and could be used in combination with rEPOs. Methods of identification of ActRII‐Fc in blood by SAR/SDS‐PAGE have been described, but not by IEF. Here we detail improvements in blood sample preparation and IEF analysis: a combined immuno‐purification of EPOs and ActRII‐Fc proteins in a single procedure, an appropriate isoforms separation for all proteins using new pre‐loading and gel conditions, and a single detection of all rEPOs and ActRII‐Fc proteins after successive incubation with anti‐EPO and anti‐ActRII antibodies.
With these changes, distinctive profiles for all the ESAs were obtained by IEF. Therefore IEF could be used as a screening method to detect a wide spectrum of prohibited ESAs in blood samples prior to specific confirmation for the identified rEPO or ActRII‐Fc.
With an increase in the ageing population worldwide, the prevalence of osteoporosis increases at an alarming rate in both male and female irrespective of their ethnicity. At present, the currently available therapeutic options are mostly limited to either bone resorptive or bone forming efficacies and both approaches are associated with serious side effects. Despite these options, there is still need for newer therapeutics to treat osteoporosis, which can offer beneficial effects for maintaining balanced dynamics between bone formation and bone resorption, devoid of any side effect. The proper understanding of pathophysiology of the disease is essential for designing or investigating an effective and safe anti‐osteoporotic agent. This review represents a discussion around the molecular targets with their implications in disease progression, available therapeutic options, the emerging targets, and the importance of designing an effective anti‐osteoporotic agent.
New therapeutic proteins that trap circulating members of the TGF beta superfamily (activins and growth differentiation factors) show promising effects on erythropoiesis and muscular growth. They are dimeric recombinant fusion proteins composed of the extracellular domain of a human activin receptor (ActRIIA or IIB) linked to the Fc part of human IgG1. Sotatercept (ActRIIA-Fc) and Luspatercept (a modified ActRIIB-Fc) in particular are now in phase 2/3 of clinical trials against anemia and included in the prohibited list established by the World Anti-Doping Agency. To prevent a potential misuse by athletes in the near future, a robust and sensitive method of detection is needed. We validated an approach adapted from an electrophoretic method used for detection of recombinant erythropoietins that allowed detection of various ActRIIA-Fc and ActRIIB-Fc proteins, including variants produced in different cell-types, after a single immuno-extraction step. After separation by SDS-PAGE, an initial testing procedure performed by single-blotting can indicate the presence of an ActRII-Fc (indifferently type IIA or IIB). A confirmation performed by double-blotting using different antibodies for detection allows a more precise identification of the type of ActRII-Fc (IIA, IIB). Starting from a few hundred microliters of serum or plasma, this method is specific, sensitive and easy to perform. It could easily be adopted by anti-doping laboratories.
Analytical chemistry represents a central aspect of doping controls. Routine sports drug testing approaches are primarily designed to address the question whether a prohibited substance is present in a doping control sample and whether prohibited methods (for example, blood transfusion or sample manipulation) have been conducted by an athlete. As some athletes have availed themselves of the substantial breadth of research and development in the pharmaceutical arena, proactive and preventive measures are required such as the early implementation of new drug candidates and corresponding metabolites into routine doping control assays, even though these drug candidates are to date not approved for human use. Beyond this, analytical data are also cornerstones of investigations into atypical or adverse analytical findings, where the overall picture provides ample reason for follow-up studies. Such studies have been of most diverse nature, and tailored approaches have been required to probe hypotheses and scenarios reported by the involved parties concerning the plausibility and consistency of statements and (analytical) facts. In order to outline the variety of challenges that doping control laboratories are facing besides providing optimal detection capabilities and analytical comprehensiveness, selected case vignettes involving the follow-up of unconventional adverse analytical findings, urine sample manipulation, drug/food contamination issues, and unexpected biotransformation reactions are thematized.
Purpose:
Inhibitors of the ActRII signaling pathways represent promising therapeutics for the treatment of muscular diseases, but also pose risks as performance-enhancing agents in sports. Bimagrumab is a human anti-ActRII antibody which was found to increase muscle mass and function by blocking ActRII signaling. As it has considerable potential for being misused as doping agent in sports, the aim of this study was to develop a mass spectrometric detection assay for doping control serum samples.
Experimental design:
Within this study, a detection method for Bimagrumab in human serum was developed, which combines ammonium sulfate precipitation and affinity purification with proteolytic digestion and LC-HRMS. To facilitate the unambiguous identification of the diagnostic peptides, an orthogonal IM separation was additionally performed.
Results:
The assay was successfully validated and the analysis of clinical samples demonstrated its fitness for purpose for an application in routine doping control analysis.
Conclusions and clinical relevance:
Although no myostatin inhibitors have obtained clinical approval yet, the proactive development of detection methods for emerging doping agents represents a key aspect of preventive doping research. The presented approach will expand the range of available tests for novel protein therapeutics and can readily be modified to include further target analytes. This article is protected by copyright. All rights reserved.
A method for the detection of Sotatercept (ACE-011, ACVR2A-Fc) in human serum is presented. The method is a modification of a recently published protocol for Luspatercept (ACE-536, ACVR2B-Fc), another erythropoiesis stimulating fusion protein. Out of 27 tested antibodies against either the extracellular domain of ACVR2A or the full length protein, only 4 antibodies bound strongly enough to Sotatercept for usage with immunoprecipitation followed by SAR-PAGE and Western single blotting. The adapted protocol allows the detection of 0.1 ng/mL Sotatercept in just 50 μL human serum. None of the three commercial ACVR2-ELISAs was able to detect Sotatercept and the two tested surrogate proteins even in the μg/mL range. As for Luspatercept, only IPG-IEF/2D-PAGE generated discrete isoforms. Due to the long serum half-life, the SAR-PAGE method will be able to detect Sotatercept for several weeks and will be very useful in doping testing.
A number of high profile revelations concerning anti-doping rule violations over the past 12 months has outlined the importance of tackling prevailing challenges and reducing the limitations of the current anti-doping system. At this time, the necessity to enhance, expand and improve analytical test methods in response to the substances outlined in the World Anti-Doping Agency's (WADA) Prohibited List represents an increasingly crucial task for modern sports drug testing programs. The ability to improve analytical testing methods often relies on the expedient application of novel information regarding superior target analytes for sports drug testing assays, drug elimination profiles, alternative test matrices, together with recent advances in instrumental developments. This annual banned-substance review evaluates literature published between October 2016 and September 2017 offering an in-depth evaluation of developments in these arenas and their potential application to substances reported in WADA's 2017 Prohibited List.
Introduction: The accurate and comprehensive determination of peptide hormones from biological fluids has represented a considerable challenge to analytical chemists for decades. Besides long-established bioanalytical ligand binding assays (or ELISA, RIA, etc.), more and more mass spectrometry-based methods have been developed recently for purposes commonly referred to as targeted proteomics. Eventually the combination of both, analyte extraction by immunoaffinity and subsequent detection by mass spectrometry, has shown to synergistically enhance the test methods’ performance characteristics.
Areas covered: The review provides an overview about the actual state of existing methods and applications concerning the analysis of endogenous peptide hormones. Here, special focus is on recent developments considering the extraction procedures with immobilized antibodies, the subsequent separation of target analytes, and their detection by mass spectrometry.
Expert commentary: Key aspects of procedures aiming at the detection and/or quantification of peptidic analytes in biological matrices have experienced considerable improvements in the last decade, particularly in terms of the assays’ sensitivity, the option of multiplexing target compounds, automatization, and high throughput operation. Despite these advances and progress as expected to be seen in the near future, immunoaffinity purification coupled to mass spectrometry is not yet a standard procedure in routine analysis compared to ELISA/RIA.
A snapshot of noteworthy recent developments in the patent literature of relevance to pharmaceutical and medical research and development.
The use of recombinant bovine somatotropin (rbST) to enhance milk production is approved in several countries, but it is prohibited in the European Union. According to EU legislation, it is necessary to confirm positive screening results prior to enforcement. Although adequate screening assays are available nowadays, development of liquid chromatography tandem mass spectrometry (LC-MS/MS) confirmatory methods to detect low levels of rbST is still a challenge. Here, we present a novel approach using immuno-affinity enrichment on monolithic micro-columns in combination with state-of-the-art ultra-high pressure LC-MS/MS (UHPLC-MS/MS) detection. The developed approach enables detection and confirmation of rbST in serum at a decision limit (CCα) concentration of 0.8 ng mL−1. Furthermore, the method is easy to handle, robust and reproducible. We successfully applied the confirmatory method to serum samples from rbST treated cows that were found suspect after immunoassay-based screening. The use of rbST could be confirmed over 1 week after treatment, and the developed method demonstrated the sensitivity needed for effective control.
Graphical Abstract
Graphical summary of the workflow, for serum preparation, enrichment with monolith microcolumns and LC-MS/MS measurement of rbST
The pathophysiology of ineffective erythropoiesis in β-thalassemia is poorly understood. We report that RAP-011, an activin receptor IIA (ActRIIA) ligand trap, improved ineffective erythropoiesis, corrected anemia and limited iron overload in a mouse model of β-thalassemia intermedia. Expression of growth differentiation factor 11 (GDF11), an ActRIIA ligand, was increased in splenic erythroblasts from thalassemic mice and in erythroblasts and sera from subjects with β-thalassemia. Inactivation of GDF11 decreased oxidative stress and the amount of α-globin membrane precipitates, resulting in increased terminal erythroid differentiation. Abnormal GDF11 expression was dependent on reactive oxygen species, suggesting the existence of an autocrine amplification loop in β-thalassemia. GDF11 inactivation also corrected the abnormal ratio of immature/mature erythroblasts by inducing apoptosis of immature erythroblasts through the Fas-Fas ligand pathway. Taken together, these observations suggest that ActRIIA ligand traps may have therapeutic relevance in β-thalassemia by suppressing the deleterious effects of GDF11, a cytokine which blocks terminal erythroid maturation through an autocrine amplification loop involving oxidative stress and α-globin precipitation.
This phase IIa study evaluated the safety and tolerability of sotatercept, and its effects on bone metabolism and haematopoiesis in newly diagnosed and relapsed multiple myeloma (MM) patients. Patients were randomized (4:1) to receive four 28-d cycles of sotatercept (0·1, 0·3, or 0·5 mg/kg) or placebo. Patients also received six cycles of combination oral melphalan, prednisolone, and thalidomide (MPT). Thirty patients were enrolled; six received placebo and 24 received sotatercept. Overall, 25% of patients received all four sotatercept doses; 71% of sotatercept-treated patients had ≥1 dose interruption mainly due to increases in haemoglobin levels. Grade ≥3 adverse events (AEs) were reported in 17% of patients receiving placebo and 58% receiving sotatercept. Grade 4 AEs in sotatercept-treated patients were neutropenia, granulocytopenia, and atrial fibrillation (one patient each). In patients without bisphosphonate use, anabolic improvements in bone mineral density and in bone formation relative to placebo occurred, whereas bone resorption was minimally affected. Increases in haemoglobin levels, versus baseline, and the duration of the increases, were higher in the sotatercept-treated patients, with a trend suggesting a dose-related effect. Multiple doses of sotatercept plus MPT appear to be safe and generally well-tolerated in MM patients.
Sotatercept (ACE-011), a recombinant human fusion protein containing the extracellular domain of the human Activin receptor IIA, binds to and inhibits activin and other members of the transforming growth factor -β (TGF-β) superfamily. Administration of sotatercept led to a rapid and sustained increase in red blood cell (RBC) count and haemoglobin (Hb) in healthy volunteers (phase I clinical trials), but the mechanism is not fully understood. Mice treated with RAP-011 (murine ortholog of ACE-011) respond with a rapid (within 24 h) increase in haematocrit, Hb, and RBC count. These effects are accompanied by an equally rapid stimulation of late-stage erythroid precursors in the bone marrow (BM). RAP-011 also induces a significant increase in erythroid burst-forming units and erythropoietin, which could contribute to additional, sustained effects on RBC production. Further in vitro co-culture studies demonstrate that BM accessory cells are required for RAP-011 effects. To better understand which TGF-β family ligand(s) mediate RAP-011 effects, we evaluated the impact of several of these ligands on erythroid differentiation. Our data suggest that RAP-011 may act to rescue growth differentiation factor 11/Activin A-induced inhibition of late-stage erythropoiesis. These data define the mechanism of action of a novel agent that regulates RBC differentiation and provide the rationale to develop sotatercept for the treatment of anaemia and ineffective erythropoiesis.
Since the first description in 1989 of CD4-Fc-fusion antagonists that inhibit human immune deficiency virus entry into T cells, Fc-fusion proteins have been intensely investigated for their effectiveness to curb a range of pathologies, with several notable recent successes coming to market. These promising outcomes have stimulated the development of novel approaches to improve their efficacy and safety, while also broadening their clinical remit to other uses such as vaccines and intravenous immunoglobulin therapy. This increased attention has also led to non-clinical applications of Fc-fusions, such as affinity reagents in microarray devices. Here we discuss recent results and more generally applicable strategies to improve Fc-fusion proteins for each application, with particular attention to the newer, less charted areas.
After the initial discovery of activins as important regulators of reproduction, novel and diverse roles have been unraveled for them. Activins are expressed in various tissues and have a broad range of activities including the regulation of gonadal function, hormonal homeostasis, growth and differentiation of musculoskeletal tissues, regulation of growth and metastasis of cancer cells, proliferation and differentiation of embryonic stem cells, and even higher brain functions. Activins signal through a combination of type I and II transmembrane serine/threonine kinase receptors. Activin receptors are shared by multiple transforming growth factor-β (TGF-β) ligands such as myostatin, growth and differentiation factor-11 and nodal. Thus, although the activity of each ligand is distinct, they are also redundant, both physiologically and pathologically in vivo. Activin receptors activated by ligands phosphorylate the receptor-regulated Smads for TGF-β, Smad2 and 3. The Smad proteins then undergo multimerization with the co-mediator Smad4, and translocate into the nucleus to regulate the transcription of target genes in cooperation with nuclear cofactors. Signaling through receptors and Smads is controlled by multiple mechanisms including phosphorylation and other posttranslational modifications such as sumoylation, which affect potein localization, stability and transcriptional activity. Non-Smad signaling also plays an important role in activin signaling. Extracellularly, follistatin and related proteins bind to activins and related TGF-β ligands, and control the signaling and availability of ligands.
The functions of activins through activin receptors are pleiotrophic, cell type-specific and contextual, and they are involved in the etiology and pathogenesis of a variety of diseases. Accordingly, activin signaling may be a target for therapeutic interventions. In this review, we summarize the current knowledge on activin signaling and discuss the potential roles of this pathway as a molecular target of therapy for metabolic diseases, musculoskeletal disorders, cancers and neural damages.
Mass accuracy is a key parameter of mass spectrometric performance. TOF instruments can reach low parts per million, and FT-ICR instruments are capable of even greater accuracy provided ion numbers are well controlled. Here we demonstrate sub-ppm mass accuracy on a linear ion trap coupled via a radio frequency-only storage trap (C-trap) to the orbitrap mass spectrometer (LTQ Orbitrap). Prior to acquisition of a spectrum, a background ion originating from ambient air is first transferred to the C-trap. Ions forming the MS or MS(n) spectrum are then added to this species, and all ions are injected into the orbitrap for analysis. Real time recalibration on the "lock mass" by corrections of mass shift removes mass error associated with calibration of the mass scale. The remaining mass error is mainly due to imperfect peaks caused by weak signals and is addressed by averaging the mass measurement over the LC peak, weighted by signal intensity. For peptide database searches in proteomics, we introduce a variable mass tolerance and achieve average absolute mass deviations of 0.48 ppm (standard deviation 0.38 ppm) and maximal deviations of less than 2 ppm. For tandem mass spectra we demonstrate similarly high mass accuracy and discuss its impact on database searching. High and routine mass accuracy in a compact instrument will dramatically improve certainty of peptide and small molecule identification.
Diseases that affect the regulation of bone turnover can lead to skeletal fragility and increased fracture risk. Members of the TGF-β superfamily have been shown to be involved in the regulation of bone mass. Activin A, a TGF-β signaling ligand, is present at high levels in bone and may play a role in the regulation of bone metabolism. Here we demonstrate that pharmacological blockade of ligand signaling through the high affinity receptor for activin, type II activin receptor (ActRIIA), by administration of the soluble extracellular domain of ActRIIA fused to a murine IgG2a-Fc, increases bone formation, bone mass, and bone strength in normal mice and in ovariectomized mice with established bone loss. These observations support the development of this pharmacological strategy for the treatment of diseases with skeletal fragility.
• anabolic
• osteoporosis
• TGF-β
• therapeutic
There are more than 500 biopharmaceuticals on the market, including more than 200 therapeutic proteins, making biologics the fastest growing sector in the biopharmaceutical market. These products include more than 40 monoclonal antibodies, for indications ranging from treatment or mitigation of various types of cancer to rheumatoid arthritis. The clinical application of these therapeutic peptides and proteins is limited by several problems, such as lack of physical and chemical stability or the lack of desirable attributes for adequate absorption or distribution. Thus, as these therapeutic peptides and proteins are made available, it will be essential to formulate these drugs into safe, stable, and efficacious delivery systems. The pharmaceutical scientist involved in this effort needs to call upon the knowledge of several disciplines, such as pharmaceutics, medicinal chemistry, biochemistry, microbiology, and chemical engineering and needs to keep abreast with the latest research in the published literature. Therapeutic Peptides and Proteins: Formulation, Processing, and Delivery Systems, Third Edition provides a comprehensive overview of the field for scientists in industry and academia and for students, while also providing practical information on the challenges facing the formulation and delivery aspects of these unique macromolecules. In particular, the book: • Explains how recombinant DNA techniques now allow us to produce therapeutic proteins in a commercially viable form • Discusses the physical and chemical pathways of peptide and protein degradation • Includes a detailed discussion of protein formulation and lyophilization • Overviews the pharmacokinetic aspects of therapeutic peptides and proteins and discusses controlled delivery systems for parenteral administration, including microsphere formulations • Discusses research progress on oral, transdermal, mucosal, and topical delivery systems discusses transdermal and topical delivery.
RationaleA plethora of compounds potentially leading to drug candidates that affect skeletal muscle function and, more specifically, mitochondrial biogenesis, has been under (pre)clinical investigation for rare as well as more common diseases. Some of these compounds could be the object of misuse by athletes aiming at artificial and/or illicit and drug-facilitated performance enhancement, necessitating preventive and proactive anti-doping measures. Methods
Early warnings and the continuous retrieval and dissemination of information are crucial for sports drug testing laboratories as well as anti-doping authorities, as they assist in preparation of efficient doping control analytical strategies for potential future threats arising from new therapeutic developments. Scientific literature represents the main source of information, which yielded the herein discussed substances and therapeutic targets, which might become relevant for doping controls in the future. Where available, mass spectrometric data are presented, supporting the development of analytical strategies and characterization of compounds possibly identified in human sports drug testing samples. Results & Conclusions
Focusing on skeletal muscle and mitochondrial biogenesis, numerous substances exhibiting agonistic or antagonistic actions on different cellular control centers' resulting in increased skeletal muscle mass, enhanced performance (as determined with laboratory animal models), and/or elevated amounts of mitochondria have been described. Substances of interest include agonists for REV-ERB (e.g. SR9009, SR9011, SR10067, GSK4112), sirtuin 1 (e.g. SRT1720, SRT2104), adenosine monophosphate-activated protein kinase (AMPK, e.g. AICAR), peroxisome proliferator-activated receptor (PPAR) (e.g. GW1516, GW0742, L165041), and inhibitory/antagonistic agents targeting the methionine-folate cycle (MOTS-c), the general control non-derepressible 5 (GCN5) acetyl transferase (e.g. CPTH2, MB-3), myostatin (e.g. MYO-029), the myostatin receptor (bimagrumab), and myostatin receptor ligands (e.g. sotatercept, ACE-031). In addition, potentially relevant drug targets were identified, e.g. with the sarcoplasmic transmembrane peptide myoregulin and the nuclear receptor corepressor 1 (NCOR-1). The antagonism of these has shown to result in substantially enhanced physical performance in animals, necessitating the monitoring of strategies such as RNA interference regarding these substances. Most drug candidates are of lower molecular mass and comprise non-natural compositions, facts which suggest approaches for their qualitative identification in doping control samples by mass spectrometry. Electrospray ionization/collision-induced dissociation mass spectra of representatives of the aforementioned substances and selected in vitro derived phase-I metabolites support this assumption, and test methods for a subset of these have been recently established. Expanding the knowledge on analytical data will further facilitate the identification of such analytes and related compounds in confiscated material as well as sports drug testing specimens. Copyright (c) 2016 John Wiley & Sons, Ltd.
Myostatin is a key regulator of skeletal muscle growth and inhibition of its signaling pathway results in an increased muscle mass and function. The aim of this study was to develop a qualitative detection assay for myostatin-neutralizing antibodies for doping control purposes by using immunological approaches.
To detect different types of myostatin-neutralizing antibodies irrespective of their amino acid sequence, an immunological assay specific for antibodies directed against myostatin and having a human Fc domain was established. Affinity purification and western blotting strategies were combined to allow extracting and identifying relevant analytes from 200 μL of plasma/serum in a non-targeted approach. The assay was characterized regarding specificity, linearity, precision, robustness, and recovery.
The assay was found to be highly specific, robust, and linear from 0.1 to 1 μg/mL. The precision was successfully specified at three different concentrations and the recovery of the affinity purification was 58%.
Within this study, an immunological detection assay for myostatin-neutralizing antibodies present in plasma/serum specimens was developed and successfully characterized. The presented approach can easily be modified to include other therapeutic antibodies and serves as proof-of-concept for the detection of antibody-based myostatin inhibitors in doping control samples. This article is protected by copyright. All rights reserved.
This article is protected by copyright. All rights reserved.
Ligands of the transforming growth factor-beta superfamily and activin-receptor signaling play an important role in erythropoiesis. Sotatercept, an activin receptor type IIA (ActRIIA) ligand trap, is a novel, recombinant, fusion protein comprising the extracellular domain of human ActRIIA linked to the Fc portion of human immunoglobulin G1. Sotatercept, originally developed to increase bone mineral density, was noted to have robust effects on erythropoiesis. Here, we evaluated the safety, pharmacokinetic properties, and pharmacodynamic effects of sotatercept in 31 healthy postmenopausal women. Sotatercept was administered at dose level 0.1, 0.3, or 1mg/kg every 28-days subcutaneously for up to four doses. Sotatercept was generally safe and well tolerated, and elicited clinically significant, dose-dependent increases in hemoglobin, hematocrit, and red blood cell counts that persisted for up to 4 months. The effect of sotatercept on hemoglobin was dose-limiting. Sotatercept also increased bone mineral density and biomarkers of bone formation. The sotatercept serum exposure-dose relationship was linear, with a mean terminal half-life of approximately 23 days. ActRIIA ligands are important regulators of erythrocyte production in healthy individuals. Clinical studies are ongoing to explore the potential of sotatercept to treat anemia and diseases of ineffective erythropoiesis as well as an agent to increase bone mineral density.
Red cell production is primarily determined by the action of erythropoietin. Additional erythropoiesis-regulatory factors include molecules and cellular interactions occurring within the bone marrow (BM) microenvironment. Sotatercept (ACE-011) is an activin receptor ligand trap which binds several members of the TGF-β superfamily. Treatment with ACE-011 reverses bone loss and reduces the degree of osteoporosis. Surprisingly, this was accompanied by elevated hemoglobin and hematocrit levels. The mechanisms underlying the beneficial effects of ACE-011 on red cell production remain unknown. This study explores the means by which ACE-011 promotes erythropoiesis. We showed that ACE-011 does not directly affect erythroid differentiation of human CD34(+) cells in vitro. We next tested whether ACE-011 acts indirectly by affecting BM accessory cells. Conditioned media (CM) produced by BM stromal cells (SC) inhibited erythroid differentiation of CD34(+) cells while maintained their ability to proliferate. However, CM from SC treated with ACE-011 partially restored erythropoiesis coinciding with changes in the molecular and secretory profile of SC, including the expression and secretion of erythropoiesis-modulatory factors. We conclude that inhibitory factors produced by BM-SC in vitro might control erythropoiesis in vivo and that agents that reverse these microenvironmental signals may provide an approach to attenuate anemia in clinical conditions.
Protein therapeutics and its enabling sister discipline, protein engineering, have emerged since the early 1980s. The first protein therapeutics were recombinant versions of natural proteins. Proteins purposefully modified to increase their clinical potential soon followed with enhancements derived from protein or glycoengineering, Fc fusion or conjugation to polyethylene glycol. Antibody-based drugs subsequently arose as the largest and fastest growing class of protein therapeutics. The rationale for developing better protein therapeutics with enhanced efficacy, greater safety, reduced immunogenicity or improved delivery comes from the convergence of clinical, scientific, technological and commercial drivers that have identified unmet needs and provided strategies to address them. Future protein drugs seem likely to be more extensively engineered to improve their performance, e.g., antibodies and Fc fusion proteins with enhanced effector functions or extended half-life. Two old concepts for improving antibodies, namely antibody-drug conjugates and bispecific antibodies, have advanced to the cusp of clinical success. As for newer protein therapeutic platform technologies, several engineered protein scaffolds are in early clinical development and offer differences and some potential advantages over antibodies.
Mass spectrometry-based proteomic approaches have been used to develop methodologies capable of detecting the abuse of protein therapeutics such as recombinant human erythropoietin and recombinant human growth hormone. Existing detection methods use antibody-based approaches that, although effective, suffer from long assay development times and specificity issues. The application of liquid chromatography with tandem mass spectrometry and selected reaction-monitoring-based analysis has demonstrated the ability to detect and quantify existing protein therapeutics in plasma. Furthermore, the multiplexing capability of selected reaction-monitoring analysis has also aided in the detection of multiple downstream biomarkers in a single analysis, requiring less sample than existing immunological techniques. The flexibility of mass spectrometric instrumentation has shown that the technique is capable of detecting the abuse of novel and existing protein therapeutics, and has a vital role in the fight to keep sports drug-free.
Activin A belongs to the TGF-beta superfamily and plays an important role in bone metabolism. It was reported that a soluble form of extracellular domain of the activin receptor type IIA (ActRIIA) fused to the Fc domain of murine IgG, an activin antagonist, has an anabolic effect on bone in intact and ovariectomized mice. The present study was designed to examine the skeletal effect of human ActRIIA-IgG1-Fc (ACE-011) in non-human primates. Young adult female Cynomolgus monkeys were given a biweekly subcutaneous injection of either 10mg/kg ACE-011 or vehicle (VEH) for 3months. Treatment effects were evaluated by histomorphometric analysis of the distal femur, femoral midshaft, femoral neck and 12th thoracic vertebrae, by muCT analysis of femoral neck and by biomarkers of bone turnover. Compared to VEH, at the distal femur ACE-011-treated monkeys had significantly increased cancellous bone volume (+93%), bone formation rate per bone surface (+166%) and osteoblast surface (+196%) indicating an anabolic action. Monkeys treated with ACE-011 also had decreased osteoclast surface and number. No differences were observed in parameters of cortical bone at the midshaft of the femur. Similar to distal femur, ACE-011-treated monkeys had significantly greater cancellous bone volume, bone formation rate and osteoblast surface at the femoral neck relative to VEH. A significant increase in bone formation rate and osteoblast surface with a decrease in osteoclast surface was observed in thoracic vertebrae. muCT analysis of femoral neck indicated more plate-like structure in ACE-011-treated monkeys. Monkeys treated with ACE-011 had no effect on serum bone-specific alkaline phosphatase and CTX at the end of the study. These observations demonstrate that ACE-011 is a dual anabolic-antiresorptive compound, improving cancellous bone volume by promoting bone formation and inhibiting bone resorption in non-human primates. Thus, soluble ActRIIA fusion protein may be useful in the prevention and/or treatment of osteoporosis and other diseases involving accelerated bone loss.
A recent study suggests that activin inhibits bone matrix mineralization, whereas treatment of mice with a soluble form of the activin type IIA receptor markedly increases bone mass and strength. To further extend these observations, we determined the skeletal effects of inhibiting activin signaling through the ActRIIA receptor in a large animal model with a hormonal profile and bone metabolism similar to humans. Ten female cynomolgus monkeys (Macaca fascicularis) were divided into two weight-matched groups and treated biweekly, for 3 months, with either a subcutaneous injection 10 mg/kg of a soluble form of the ActRIIA receptor fused with the Fc portion of human IgG(1) (ACE-011) or vehicle (VEH). Bone mineral density (BMD), micro-architecture, compressive mechanical properties, and ash fraction were assessed at the end of the treatment period. BMD was significantly higher in ACE-011 treated individuals compared to VEH: +13% (p=0.003) in the 5th lumbar vertebral body and +15% (p=0.05) in the distal femur. In addition, trabecular volumetric bone density at the distal femur was 72% (p=0.0004) higher than the VEH-treated group. Monkeys treated with ACE-011 also had a significantly higher L5 vertebral body trabecular bone volume (p=0.002) and compressive mechanical properties. Ash fraction of L4 trabecular bone cores did not differ between groups. These results demonstrate that treatment with a soluble form of ActRIIA (ACE-011) enhances bone mass and bone strength in cynomolgus monkeys, and provide strong rationale for exploring the use of ACE-011 to prevent and/or treat skeletal fragility.
The effects of ACE-011 on safety, pharmacokinetics, and bone biomarkers were evaluated in healthy, postmenopausal women. Our data indicate that ACE-011 results in a sustained increase in biomarkers of bone formation and reduction in markers of bone resorption. The activin type IIA receptor (ActRIIA) is the high-affinity receptor for activin. ACE-011 is a dimeric fusion protein consisting of the extracellular domain of the human ActRIIA linked to the Fc portion of human IgG1. ACE-011 binds to activin, preventing activin from binding endogenous receptors. A randomized, double-blind, placebo-controlled study was conducted to evaluate the safety and tolerability of ACE-011. Forty-eight healthy, postmenopausal women were randomized to receive either a single dose of ACE-011 or placebo and were followed for 4 mo. Dose levels ranged from 0.01 to 3.0 mg/kg intravenously and from 0.03 to 0.1 mg/kg subcutaneously. Safety and pharmacokinetic (PK) analyses and the biological activity of ACE-011, as assessed by markers of bone turnover, and follicle stimulating hormone (FSH) levels were measured. No serious adverse events (AEs) were reported. AEs were generally mild and transient. The PK of ACE-011 was linear over the dose range studied, with a mean half-life of 24-32 days. The absorption after subcutaneous dosing was essentially complete. ACE-011 caused a rapid and sustained dose-dependent increase in serum levels of bone-specific alkaline phosphatase (BSALP) and a dose-dependent decrease in C-terminal type 1 collagen telopeptide (CTX) and TRACP-5b levels. There was also a dose-dependent decrease in serum FSH levels consistent with inhibition of activin. ACE-011 is a novel agent with biological evidence of both an increase in bone formation and a decrease in bone resorption. ACE-011 may be an effective therapy in a variety of diseases involving bone loss.
Advances in recombinant DNA technology have created one of the most powerful weapons in the current doping arsenal: recombinant proteins [Sweeney HL. Gene doping. Sci Am 2004;291:62-9; Unal M, Ozer Unal D. Gene doping in sports. Sports Med 2004;34:357-62]. Recombinant erythropoietin (EPO) and human growth hormone (hGH) are currently being abused but are fortunately detectable either directly by employing isoelectric focusing and immunoassays or indirectly by assessing changes in selected hematopoietic parameters. The detection is technically demanding due to the extent of similarity between the recombinant proteins and their endogenous counterparts. Another issue facing detection efforts is the speed and conditions at which blood samples are collected and analyzed in a sports setting. Recently, gene doping, which stemmed out of legitimate gene therapy trials, has emerged as the next level of doping. Erythropoietin (EPO), human growth hormone (hGH), insulin-like growth factor-1 (IGF-1), peroxisome proliferator-activated receptor-delta (PPAR delta), and myostatin inhibitor genes have been identified as primary targets for doping. Sports clinical scientists today are racing against the clock because assuring the continued integrity of sports competition depends on their ability to outpace the efforts of dopers by developing new detection strategies.
The present study investigated serum immunoglobulin (Ig) concentrations in relation to demographic factors, common habits (alcohol consumption and smoking) and metabolic abnormalities in an adult population-based survey including 460 individuals. Serum levels of interleukin (IL)-6, a marker of inflammation, were also determined. After adjusting for confounders, male sex was associated positively with IgA levels and negatively with IgM levels. Age was associated positively with IgA and IgG levels. Smoking was associated negatively with IgG levels. Heavy drinking was associated positively with IgA levels. Metabolic abnormalities (obesity and metabolic syndrome) were associated positively with IgA levels. Abdominal obesity and hypertriglyceridaemia were the components of metabolic syndrome associated most strongly with serum IgA. Heavy drinkers with metabolic syndrome showed particularly high serum IgA levels. Serum IL-6 levels were correlated positively with IgA and IgG concentrations. It is concluded that sex, age, alcohol consumption, smoking and common metabolic abnormalities should be taken into account when interpreting serum levels of IgA, IgG and IgM.
Once a rarely used subset of medical treatments, protein therapeutics have increased dramatically in number and frequency of use since the introduction of the first recombinant protein therapeutic--human insulin--25 years ago. Protein therapeutics already have a significant role in almost every field of medicine, but this role is still only in its infancy. This article overviews some of the key characteristics of protein therapeutics, summarizes the more than 130 protein therapeutics used currently and suggests a new classification of these proteins according to their pharmacological action.
BioRad Laboratories Inc Introduction to Western Blotting https
- Abd Serotec
Safety and hemoglobin effect of the first 28-day dose cycle of sotatercept 0.7 mg/kg compared with lower doses and placebo for correction of anemia in hemodialysis subjects: interim analysis
- M El-Shahawy
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Protein therapeutics: a summary and pharmacological classification
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Electrophoresis ’86: proceedings of the Fifth Meeting of the International Electrophoresis Society
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Ig gamma-1 chain C region P01857 (IGHG1_HUMAN)
- Uniprot Consortium
Activin receptor type-2A P27037 (AVR2A_HUMAN)
- Uniprot Consortium