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BIOSIMILARS

OVERVIEW

WHAT ARE BIOLOGIC DRUGS?

The rapid development of science and technology in the XXth century allowed for the introduction of biologic drugs (biopharmaceuticals), which have revolutionized the treatment of patients with metabolic, oncologic and autoimmune diseases. Biologic drugs is relatively broad group of products that are derived from living organisms (eg. human, animal, plant or microorganism sources). Some of them, like recombinant proteins, are manufactured with the use of  advanced biotechnology methods, using genetic engineering tools and living expression systems based on cell cultures. Biologics are a diverse group that also including products obtained directly from humans or animals – like blood or blood components, cells and tissues for transplantations, vaccines, gene and cell therapies. are designed on the basis of natural proteins present in the human organism, substituting a missing or malfunctioning  protein (e.g. erythropoietin, the human growth factor) or exercising a known function in a newly designed process, bringing about a therapeutic effect (e.g. monoclonal antibodies exterminating cancerous cells in leukemia). These therapeutics are under constant development - e.g. insulin used to be obtained from animals, but now a fully human type of insulin, developed by genetic engineering, is being produced by microorganisms. Mabion focuses  on a group of biopharmaceuticals produced with use of recombinant DNA technology with special focus on monoclonal antibodies class. The first monoclonal antibodies (used for the treatment of cancer and autoimmune diseases) were of mouse origin, which made them  highly immunogenic, so various methods of diminishing  this effect had to be designed.  This led first to the construction of genetically engineered chimeric antibodies, then of humanized ones, which means that the sequence and structure of the protein is design mostly basing on human native antibody sequences and only small parts responsible for antigen recognition are derived from murine sequences. This technique ensures low immunogenicity and safety of the product, maintaining its therapeutic effect. Because biopharmaceuticals are much bigger (200 to 1,000 times) and more complex than small molecule chemical compounds (which are the basis of traditional drugs) they cannot be obtained in the process of traditional chemical synthesis, but  involve the usage of living cell systems, followed by a multi-step purification and formulation process, resulting in a molecule, which is perfectly designed for  its target. Summing up, Monoclonal Antibodies have two unique features which decide about their marketing as well as clinical success - high level of safety due imitating native huan proteins occusring in the organism and triggering immune response against disease, and specificity - antibodies interact only with molecular target, cause of disease, with limited influence on any other tissues, cells or proteins.

BIOSIMILARS VERSUS GENERICS

The complex and highly advanced nature of biosimilars' production makes this type of medicines different from chemically synthesized generic drugs on many levels. A biosimilar is never identical to its reference drug, as well as each batch of a reference drug is never identical to other batches. However, biosimilars are not required to be identical – they have to execute their designed therapeutic function, while remaining safe and efficient at equivalent level as their reference medicines. Generic drug manufacturers can usually choose from different pathways of chemical synthesis and introduce changes to the process, as long as the finished product remains the same as the originator, which is easily proven by analytical methods, confirming the product identity. However, this does not apply to biosimilars, which are composed of  large and complex molecules, which  have to be obtained by expression in genetically engineered cells in a process, which is specifically designed for particular cell clone. The selection of a cell line, post-translational modifications of a protein, the design of the process flow, the choice of buffers and starting materials – all those factors influence the final product. Even a small change in the process can result in a different molecule.In order to obtain approval for a generic drug, the manufacturer needs to demonstrate that the product consists of the same active ingredients and that its therapeutic effect, dosage form, routes of administration and bioequivalence are no different from the originator. These tests are usually easy to perform in the laboratory, and may require only blood test sampling from healthy volunteers, with no need for clinical trials.  However, each biosimilar is treated as a new product, produced by a unique, specifically designed process, and should be treated like a new medicine. Despite the fact that amino acid sequence must be the same, the protein product in many cases is composed by more than one isoform.The isoforms have the same amino acid sequence but different posttranslational modifications (eg. with added different sets of sugars in case of glycoproteins). The manufacturer has to prove, that the product obtained via a newly designed process has equivalent therapeutic effect, safety and side effects as the originator. Therefore a large number of lab test and robust clinical trials are required by the legal authorities which is not a case when generic drugs are concerned. Due to their biologic nature, biosimilars are more fragile with regard to handling, storage and transport conditions. They are sensitive to changes in pH, temperature, and are susceptible to potential microbial contamination and degradation. Their manufacturing process needs to be performed in highly controlled. A biosimilar is an advanced product, handled by professionals at each step and designed by experienced scientists. It is manufactured by professionally trained employees, working in strict accordance with GMP regulations.

MARKETING AUTHORISATION PROCESS

Regulations on granting marketing authorisation for biosimilars are complex and very demanding everywhere in the world. In regulated markets (Europe, the United States, Japan, Canada), regulatory bodies require meeting restrictive criteria regarding quality, safety and efficacy. Companies which wish to obtain marketing authorisation in a regulated market have to present detailed laboratory and toxicological trials (conducted on animals) and clinical data, including studies on pharmacokinetics and pharmacodynamics of a biosimilar and a reference drug to demonstrate no significant clinical differences. As biosimilars must imitate the effects of the reference product, requirements regarding clinical trials are different from those applicable to innovative biologic drugs.
On the one hand, phase II of clinical trials which is set to determine the effective dose is not required for the development of biosimilar drugs, as the adequate posology is already known. On the other hand, however, the collected clinical data range is smaller than in the case of innovative drugs, hence the overall set of data – including a wide range of analytical data – is pivotal for demonstrating a high similarity to the reference drug.Regulatory agencies may grant marketing authorisation to a given drug for indications analysed in the course of clinical trials or for a full range of the reference drug's indications. Different regulatory agencies may decide differently on that matter. However, in most cases, if the responsible entity demonstrates a high level of similarity to an already registered product, the regulatory agencies grant the new product a marketing authorisation for all indications of the reference drug.

SAFETY PROFILE AND REGULATORY REQUIREMENTS

Drugs manufacturers are obliged to draw up and submit reports on safety both during clinical trials and after the drug’s registration. The analysis of the safety profile leads to reduction of risk of adverse effects in patients. Doctors need comprehensive and accurate data on adverse events related to a given medicine in order to prescribe a patientspecific dose.
All biological drugs pose a risk, sometimes relatively insignificant, of an adverse immune reaction. This is why, timely reporting of every adverse effect is very important. Special programmes of supervision over the safety of pharmacotherapy have been established in order to manage the risk of adverse effects correctly and to protect patients. It is crucial for every programme dedicated to a given biological drug, including biosimilars, to incorporate strict procedures which allow for drug safety monitoring in order to identify, comprehend, assess correctly and, thus, prevent adverse effects of the use of biological drugs in the future. Giving a drug an International Nonproprietary Name (INN) is an important tool for its identification and monitoring. Each INN is a unique name recognised all over the world.

SCIENCE

CLONE IDENTIFICATION

Due to their high complexity, biological drugs are produced by cells, for example, mammiferous cells, and later purified. However, various cell lines will produce biological drugs with slightly different profiles. Even various clones obtained from the same cell line may demonstrate different protein expression. Hundreds of cellular clones from one line have to be analysed to identify cells which produce a biological molecule which is as similar to the reference product as possible. In order to choose the best cellular clone to manufacture a biosimilar drug, scientists have to choose a clone whose critical attributes are as similar to the reference drug as possible. Most importantly, the biological functions of both such drugs are almost identical. The better the match of critical quality features and biological functions, the greater the certainty as to the efficacy and safety of the biosimilar drug.

CRITICAL QUALITY ATTRIBUTES

Biological drugs are extremely complex molecules whose function and mechanisms of action in the human body are not fully understood, which means that their characteristics and biological activity determined in vitro do not have to fully correspond to the mechanisms which are significant in vivo.
Biological drugs usually have at least several dozens of critical features called attributes. Some of those attributes are important for the body to recognise the protein molecule and thereby they are of pivotal importance for the safety, efficacy and pharmacokinetics of the drug. The most significant features of biological drugs are referred to as critical quality attributes.
Full understanding of the pivotal quality features of both the reference and the biosimilar product (including the attributes significant for their characteristics), as well as the safety profile, efficacy and pharmacokinetics (the way the drug is metabolised by the body), has fundamental significance for the proper development of the antibody manufacture process.
Critical attributes are conditioned firstly by the DNA sequence which codes them, and additionally by the cell line in which the expression occurs, as well as by the manufacture process itself. Full knowledge of all the mentioned variables allows for developing a high-quality biosimilar drug.
Biosimilar drugs, as opposed to small molecule generic drugs, are not 100% identical to the reference drug. For such a drug to be authorised, the most important quality features, and thus the biological activity, must be very similar, and the drug must have the same impact on the patient.
The greatest challenge faced in the process of developing biological biosimilar drugs is the fact that not all features of the biologically active molecule are characterised in full or even in part, and therefore the biological activity is not perfectly clear.

ANALYTICAL METHODS

Results of clinical trials are of pivotal importance for the development of innovative drugs. However, in the case of development of biosimilars, the most important aspects are the data from physico-chemical properties analyses and biological tests which aim at demonstrating high level of similarity to the reference product. Hence, all analytical methods used for that purpose need to be sufficiently advanced technologically to allow for detecting all, even slight, differences in critical attributes (physico-chemical properties and biological activity). In this case clinical trials only supplement the results obtained in the laboratory.
Biological tests are used to assess activity of the therapeutic protein in the biological system with a selected cellular line (in vitrotests) or a protein which is significant from the perspective of the mechanism of action of the drug in the cell. The measurement can be based on an evaluation of the bonding strength of the biosimilar drug or on the relative activity of the biosimilar drug to the reference drug.
Product quality is essential to the efficacy and safety of all drugs, not just biological ones. It is evaluated at every stage of the process. The methods used for such analyses must not only be sensitive enough to detect even the smallest differences, but they also must have sufficient resolution to ensure that the actual differences can be detected. In many cases this requires specific expertise which can be obtained by way of participating in numerous workshops and conferences. Furthermore, this often requires adequate, complex, cutting-edge – and thus expensive – specialised equipment.
Different drugs have different mechanisms of action, which results from activation of different cellular pathways. For example, one of the mechanisms of action of antibodies in the human body is the antibody-dependent cellular cytotoxicity (ADCC) mechanism. ADCC is a process in which a target cell, e.g. a tumour cell, is killed by NK (natural killer) cells – a group of lymphocytes which take part in the non-specific response of the body.
Antibody-dependent cellular cytotoxicity (ADCC) can be measured in an assay using cells from a donor's blood or cells producing and containing (preferably on their surface) a protein recognised by the therapeutic antibody. Human cells collected from a donor include a wide range of cell types in the serum, not all of which are involved in the ADCC reaction. Furthermore, natural genetic variation in the human population can result in significant differences between donors, therefore genetically recombinant cell lines are in principle a better alternative with regard to not only reproducibility of results, but also sensitivity and specificity of the test.

DEVELOPMENT OF BIOSIMILARS

The clinical trials programme aims at demonstrating that there are no significant differences between the original drug and the biosimilar one in terms of their efficacy, safety and immunogenicity. Immunogenicity is the ability of, e.g., a drug, to trigger a specific immunological response. Every drug may activate the immune system strongly or weakly – it is said that a given drug is, respectively, strongly or weakly immunogenic. Clinical trials involve the evaluation of pharmacokinetics, pharmacodynamics, safety and efficacy. Since many drugs can be used to treat more than one illness, the choice of patient population is crucial. Guidelines provided by regulatory organisations indicate that clinical trials should be conducted on the most sensitive and homogeneous population which allows to detect clinically significant differences between the researched drugs. Those trials should be designed in a way which allows to demonstrate the bioequivalence of the drugs in question. Bioequivalence means that there is no significant difference in the bioavailability of drugs in the biological target after administering them in the same doses and forms, i.e. that the drug’s efficacy is neither higher nor lower, as compared to the reference product. Moreover, the trials should demonstrate a similar safety profile. They also must have sufficient resolution to ensure that the actual differences can be detected. In many cases this requires specific expertise which can be obtained by way of participating in numerous workshops and conferences. Furthermore, this often requires adequate, complex, cutting-edge – and thus expensive – specialised equipment. Different drugs have different mechanisms of action, which results from activation of various cellular pathways. For example, one of the mechanisms of action of antibodies in the human body is the antibody-dependent cellular cytotoxicity (ADCC) mechanism. ADCC is a process in which a target cell, e.g. a tumour cell, is killed by NK (natural killer) cells – a group of lymphocytes which take part in the non-specific response of the body. Antibody-dependent cellular cytotoxicity (ADCC) can be measured in an assay using cells from a donor's blood or cells producing and containing (preferably on their surface) a protein recognised by the therapeutic antibody. Human cells collected from a donor include a wide range of cell types in the serum, not all of which are involved in the ADCC reaction. Furthermore, natural genetic variation in the human population can result in significant differences between donors, therefore genetically recombinant cell lines are in principle a better alternative with regard to not only reproducibility of results, but also sensitivity and specificity of the test.

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