Chapter 1
Introduction to Biomanufacturing

Mark F. Witcher

NNE, Durham, North Carolina, USA

1.1 Introduction

While the book covers designing biopharmaceutical and vaccine manufacturing facilities, this chapter is a brief introduction to biopharmaceutical manufacturing covering the essential elements of the overall biomanufacturing enterprise. Biomanufacturing is very complex and challenging. To be successful, the facility must be designed with a basic understanding of the overall manufacturing enterprise and how it functions. To simplify the discussion, vaccines will be combined with protein products for the purposes of this chapter.

The objective of this introduction is to:

• Identify and describe a biopharmaceutical manufacturing enterprise's three basic elements (process, facility, and infrastructure);
• Briefly describe the constituents used in biopharmaceutical manufacturing processes to appreciate the complexity and fundamental issues of operating the process's unit operations (UOs) within the facility;
• Identify the basic process UOs typically used in biopharmaceutical manufacturing;
• Provide a framework for describing, evaluating, and controlling the facility and process UOs, and;
• Provide an understanding of how the overall manufacturing enterprise is operated and controlled.

In order to understand the challenges of biomanufacturing, we begin by looking at the overall manufacturing enterprise that surrounds and operates the manufacturing facility. As shown in Fig. 1.1, the manufacturing enterprise's myriad of components can be divided into three elements. The facility, process, and infrastructure are integrated and operated in concert to produce the product. As will be discussed, the three elements contain a wide variety of components required to achieve the overall objectives of the enterprise. Although the distribution used here provides structure to this introductory chapter, many variants or alternative distributions are possible.

Figure 1.1 The manufacturing enterprise is composed of three elements. Basically, the enterprise operates the process within the facility under the control of the infrastructure. The process and the facility are separate entities that can be run independently with the infrastructure providing the interface between the two. As shown in the side figure, the process is contained within the facility. The infrastructure element resides partially within the facility because the infrastructure is composed of both facility-specific and companywide, multifacility components.

In older enterprises, the facility and process are interdependent because the two were designed and constructed at the same time, usually for a specific product. In future enterprises, the process and facility will much less dependent on each other, with the multiproduct facility capable of running a wide variety of different processes. Because the process is not directly integrated with the facility, the processes can be moved in and out of a facility or moved to a different facility depending on manufacturing capacity or logistical requirements [1].

Manufacturing facilities are harder to run than they are to build. For the enterprise to be successful, the facility must be designed to be operated. All three elements must be carefully developed, so they can be integrated to assure the overall enterprise's success. They must work together in order to support and facilitate adequate control of all production activities to assure the efficient production of high quality product over the entire lifecycle of every product produced by the facility. This concept is emphasized by understanding that conformance lots or PPQ (process performance qualification) batches are more than just a test of the process [2]. Conformance lots are a test of the enterprise's ability to operate the process. Many conformance lot issues are encountered because the staff, part of the infrastructure, are not adequately trained and do not have the experience to execute the many tasks and activities required to successfully run the process and facility.

Starting from the beginning, the basic constituents of biopharmaceutical processes are cells, nucleic acids, and proteins.

1.2 The Basic Constituents of Biopharmaceuticals

Biopharmaceutical manufacturing uses relatively simple processes composed of UOs employing relatively simple pieces of equipment as compared to other industries, particularly those in the chemical and petrochemical industries. However, the constituents within the UOs are many orders of magnitude more complex. The purpose of this section is to provide a very brief introduction to the formidable challenges of managing and manipulating these constituents.

A defining element of biopharmaceuticals is the use of cells to produce the product. The product is most frequently a protein, but the product can be the cells themselves used for cellular therapies or in some cases the product can be genetic material manufactured in large quantities to modify or control genetic constructs and control mechanisms within the patient.

The cell is the largest and most complex element. The growth and characteristics of the cells are defined primarily by the genetic information stored in the cell's DNA. The machinery of the cells that use the genetic information is operated by proteins. The discussion will begin by describing the simplest element, proteins. Most pharmaceutical products are proteins manufacturing by the cell under the control of genetic constructs inserted into the cells using recombinant technology.

1.2.1 Proteins

Biopharmaceuticals are proteins. The product is created by cells in a complex environment of many complex biological molecules (carbohydrates, nucleic acids, lipids, and proteins) and cellular processes required for cell growth and product manufacturing. The discussion begins with an overview of proteins and their structure and behavior.

The fundamental structure of proteins is shown in Fig. 1.2. Proteins are polymers of 20 specific amino acids shown in Fig. 1.3 assembled by the cell according to the genetic code contained within the cell.

Figure 1.2 Proteins are a polymer of the 20 amino acids listed in Fig. 1.3. They are typically between 100 and 1500 amino acids in length. The term peptide refers to amino acid polymers of <25 amino acids.

Figure 1.3 While the Earth's natural environment contains hundreds of different amino acids, all life forms use only the 20 amino acids shown.

The sequence of amino acids forms the primary structure of the protein. Depending on many different structural and environmental factors, the amino acid chain is folded into higher order structures. These higher order structures can be defined as follows:

• Primary: the linear amino acid sequence of the polypeptide;
• Secondary: the localized folding of the primary structure into substructures sometimes called helices, strands, and sheets;
• Tertiary: the combining of the secondary spiral and flat elements to form larger three-dimensional structures;
• Quaternary: combining of tertiary structures to form a much larger complex three-dimensional structures.

The structures determine the protein's properties, including its safety and efficacy as a therapeutic product.

Additional protein complexity comes from post-translational modifications (PTMs) added to the protein during and after the four structural features described earlier are formed by the cell. PTMs change the behavior of the protein in solution and affect their therapeutic impact, safety, and efficacy in a wide variety of ways. The four structural features and PTMs along with the various altered product forms resulting from degradation, alternations, misincorporation, and aggregation combine with various impurities and contaminates from the manufacturing processes to determine the complex set of critical quality attributes (CQAs) that define the product's overall quality target product profile (QTPP) as defined in ICH Q8 (R2) [3]. The objective of the manufacturing process is to consistently produce a product described by the product's QTPP defined during development, tested in preclinical testing; and demonstrated to be safe and effective by clinical trials. For more details on the definition of biological products, ICH Q6B and ICH Q5E should be consulted [4, 5]. Biochemistry text books can be consulted for more information related to the structure, composition, and behavior of proteins [6-8].

All cells use thousands of proteins, called enzymes, to operate the machinery required to perform the myriad of internal maintenance functions, reproduce, and manufacture the product protein [9]. The production of proteins within the cell is carried out by complex metabolic pathways based on the genetic information contained within the cell. The genetic information is stored in the cell's DNA (deoxyribonucleic acid) formed by polymers of nucleic acids described later.

1.2.2 Nucleic Acids (DNA and RNA)

DNA provides a stable and efficient mechanism for storing and maintaining genetic information critical to the cell's ability to consistently and efficiently replicate without losing the ability to produce the target protein over many generations. DNA has a complex double helix spiral structure formed by two...