Understanding The World of Biotherapeutic Proteins

Biotherapeutic proteins have great clinical success and are now highly recognized for their great potential against numerous diseases.

The term “protein” was proposed in 1838 by Jöns Jakob Berzelius and etymologically the word derives from the Greek proteios (fundamental, principal, in time, place, order or importance). Although it is debatable which molecules are the most important for life, currently therapeutic proteins are the most important biologics in terms of their clinical utility. They represent a mainstay in the treatment of various conditions, such as autoimmune disorders, hematological disorders, hormonal dysfunctions, cancers, infectious diseases and genetic disorders. This great potential against different diseases has led to the number of existing biotherapeutic proteins exceeding one hundred, occupying a market worth more than 140 billion euros. It is estimated that in 2028 the biotherapeutic protein market will reach 250 billion euros, being mainly dominated by monoclonal antibodies (mAb) and Fc fusion proteins.

The beginning

Therapeutic proteins did not become a reality until the second half of the 1970s, when recombinant human insulin was produced in Escherichia coli. This milestone in the history of biotechnology occurred in 1978. The cloning and expression of a human gene in a bacterial host cell was achieved for the first time, allowing the large-scale production of insulin. Prior to the 1980s, insulin was obtained mainly from animal pancreases, with supply limitations and high immunogenicity in many patients. Recombinant insulin radically changed the treatment of diabetes, paving the way for future biotechnology drugs.

The first biotherapeutic proteins to be produced using mammalian cells as a host were recombinant plasminogen activator (rt-PA) and erythropoietin (EPO). Approved in 1987, rt-PA is used as a treatment for cardiovascular accidents because it dissolves blood clots. Since then, it has been produced using Chinese hamster ovary cells, known as CHO. The choice of these mammalian cells allowed the correct glycosylation of the protein, impossible to achieve in other non-mammalian hosts, and vital for its efficacy in humans. On the other hand, EPO stimulates the production of red blood cells in patients with anemia, and was also produced in CHO cells in the 1980s.

These advances not only significantly improved the accessibility of life-saving treatments, but also laid the groundwork for the production of a new generation of biologic drugs. Thus began the beginning of an era in which genetic engineering plays a key role in the innovation and development of advanced medical therapies.

The classification of therapeutic proteins!

As in an endless game of classification, these proteins seem to have more categories than the Oscar awards. Focusing on their pharmacological activity, biotherapeutic proteins can be grouped into five groups: (a) those that replace deficient or abnormal proteins, (b) those that augment existing pathways, (c) those that provide new and exciting functions or activities, (d) those that block molecules or organisms, and (e) those that release or act as transporters for other molecules such as radionuclides, cytotoxic drugs or effector proteins. But wait, there’s more! Biotherapeutic proteins can also be classified at the molecular level, thus antibody-based drugs, anticoagulants, Fc fusion proteins and growth factors. And, last but not least, there is a division according to their molecular mechanism of action, which leads us to non-covalent binding proteins, covalent binding proteins and, of course, the “others” group!

The diversity and complexity of these classifications reflect the broad therapeutic range offered by biotherapeutic proteins. Likewise, this wide range of classifications highlights their intrinsic versatility and the potential they possess to address diverse medical conditions and diseases.

Advantages and disadvantages of therapeutic proteins

Therapeutic proteins, such as mAb, are subject to rigorous safety, immunogenicity, quality and efficacy evaluations by the relevant authorities (EMA, FDA, etc.) In terms of safety, the interaction of therapeutic proteins with their specific and unintended targets can induce side effects, most notably immune overstimulation in some cases.

Immunogenicity, evidenced by the high immunogenicity of the first murine mAb, has prompted the development of less immunogenic variants, such as chimeric or humanized mAb. This paradigm shift in the production of biotherapeutic proteins has led to an increasing use in the last decade of human cell lines. These offer the advantage of producing recombinant proteins with post-translational modifications more consistent with endogenous human proteins.

Quality, which is a determining factor for approval by regulatory authorities, focuses on a number of stringent criteria including low heterogeneity and high purity of proteins. To meet these standards, meticulously designed production processes, stable cell lines and highly efficient purification methods are required, involving great care at every stage of the manufacturing process.

Efficacy, while fundamental, can vary, as evidenced by treatment with the Trastuzumab antibody for HER2-positive breast cancer. Such variability in responses may be due to factors such as pre-existing resistance or limited tissue penetration. Approaches, such as multitargeted antibodies, are being implemented to improve the efficacy of these therapies and address variability in patient responses. In summary, successful approval of therapeutic proteins involves carefully addressing these aspects, from safety to efficacy, to ensure their quality and clinical utility.


One of the main directions of current activity is to develop biosimilars. A biosimilar drug is very similar to another biological drug called a reference drug. Although biosimilar drugs and reference drugs are made from living organisms, they may be made in different ways and with slightly different substances. For a drug to be called a biosimilar, the biological drug must be shown to be as safe, as effective and work in the same way as its reference drug. It must also be used in the same way, at the same dose and for the same condition as the reference drug. Regulatory agencies must approve biosimilar drugs, which may cost less than the reference drug.

The rise of biosimilars has been fueled by the loss of patents on dozens of biological drugs. Generic companies are expected to become increasingly important, with the biosimilars market estimated to reach €10 billion by 2025. However, only a handful of large pharmaceutical companies and world-class R&D facilities will be able to be part of this market boom. This means that most small and medium-sized companies will never have the opportunity to enter the new biosimilars market. The niche for most small biotech companies is either to provide support or to take a preclinical or very early stage candidate themselves through to proof of concept, at which point they can sell it to larger companies. In the case of biosimilars, the developer will start with proof-of-concept data and then move on to the more expensive phase of clinical development, with the added cost of conducting a comparative study with the marketed drug. This whole process is neither inexpensive nor fast. In fact, the implementation of a biosimilar program takes an average of 8 years, with development costs ranging from 30 million euros to 250 million euros.

In a decade…

The rapid advances achieved in recent years raise some uncertainty about the future direction of therapeutic protein development. There are numerous open lines of research such as the gradual improvement of the characteristics of existing therapeutic proteins or the discovery of new protein-based drugs. In addition, the combination of therapeutic proteins, their conjugation with drugs, nanoparticles and other reagents are showing strong potential. Likewise, predictive tools to narrow down which candidate proteins could be successfully developed as therapeutics represent an essential part of current research. A decade from now, it is likely that many of these therapies that are currently in early stages of development will be approved for clinical use. And who knows if any of them will also represent a paradigm shift, in the same way that producing human insulin in bacteria or starting to use human cell lines for the production of biotherapeutic proteins did.


Originial article: Farmabiotec magazine, number 11, pages 44-46


About 53Biologics:

53Biologics is a CDMO with specialized in biologics production, from pDNA, mRNA and proteins. It is a leading biopharma company providing services from preclinical and clinical development to GMP manufacturing, supporting our clients in getting their biological products to market as quickly as possible.

For more information contact Patricia De La Madrid, Marketing & Business Development Manager at 53Biologics through this email: pdelamadrid@53biologics.com

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