Bioprocess engineering Manufacturing process for final products - Industrial scale process - Scale-up - Process optimization - Cost analysis : Economic feasibility Tainted Drugs Put Focus on the FDA Contaminated medicine from China was linked to as many as 19 deaths in t he United States Members of Congress clamored for changes while regul
ators defended their actions. Nineteen deaths have been linked to contaminated heparin, a crucial blood thinner manufactured in China. The FDA admitted that it violated its own policies by failing to inspect the China plant, altering border agents to detain suspect heparin shipments. Eighty percent of the active pharmaceutical ingredients consumed in the Uni ted States are manufactured abroad; - 40 % are made in China and India. The FDA has cut back on its foreign drug
inspections, mainly because of lack of budget. There are 566 plants in China that export drugs to the United States, but the agency inspected just 13 of them last year. Plants in China and India are rarely inspected by Western governments, whic h can reduce costs dramatically.
Even the Chinese did not inspect the plant making contaminated heparin bec ause everything made at the plant was shipped overseas. Heparin A highly-sulfated glycosaminoglycan with highest negative charge density of any known biological molecule. It is most abundant in connective tissues, and produ ced by basophils and mast cells
Widely used as an injectable anticoagulant and an inner anticoagulant surface o n various experimental and medical devices such as renal dialysis machines. Heparin binds to the enzyme inhibitor anti-thrombin III (AT), activating it. The activated AT then inactivates thrombin and other proteases involved in blood clotting, most notably factor Xa.
Derived from mucosal tissues of slaughtered meat animals such as porcine (pig) intestine or bovine (cow) lung. Native heparin: a polymer with a molecular weight ranging from 3 kDa to 40 kD a. The average molecular weight of most commercial heparin preparations: 12 k Da ~ 15 kDa.
A variably-sulfated repeating disaccharide unit. The most common disaccha ride unit is composed of a 2-O-sulfated iduronic acid and 6-O-sulfated, N-su lfated glucosamine, IdoA(2S)-GlcNS(6S). Bioprocess for production of therapeutic agents Manufacture of therapeutic agents : one of the most highly regulated and rigorously controlled bioprocesses To gain a manufacturing license, the producer proves that not only the product itself is safe and effective, but all aspects of the
proposed bioprocess comply with the highest safety and quality standards Elements contributing to the safe production Design and layout of the manufacturing facility Raw materials utilized in the process
Bioprocess itself Training and commitment of personnel involved in all aspects of the manufacturing operation Existence of a regulatory framework which assures the establis hment and maintenance of the highest quality standards regard ing all aspects of bioprocess Overall manufacturing process
Infrastructure of a typical manufacturing facility Source of therapeutic proteins Up-stream and down-stream processing of products Analysis of the final products : quality control Cell culture process for therapeutic proteins Overall process
Protein purification process Affinity purification Loading A Affinity ligand Colum
n Binding Washing Elution Affinity chromatography Therapeutic antibody production and purification
Protein A Surface protein of bacterium Staphylococcus aureus : 56 kDa Binds the heavy chain within the Fc of most immunoglobulins : KD= ~30 nM Major market share by GE Healthcare - immobilization of protein A on resin Ethanol fermentation process
Ethanol fermentation tanks Microorganism fermentation system Host cells for the production of valuable molecules The use of appropriate expression system for specific products : Each expression system displays its own unique set of advantage s and disadvantages Many of therapeutic agents currently on the market : produced by recombinant DNA technology using various expression syste ms such as bacteria, yeast, fungi, and mammalian cells
Many therapeutic proteins are produced by recombinant DNA t echnology E. coil Most common microbial species used to produce heterologous proteins - Heterologous protein : protein that does not occur in host cells Some important molecules: Amino acids, organic acids, vitamins ex) recombinant human insulin (Humulin) in 1982 tPA (tissue plasminogen activator in 1996
L-Threonine, L-Tryptophan, L-lactic acid Major advantages of E. coli - Its molecular biology is well characterized - High level expression of heterologous proteins : - High expression promoters - ~ 30 % of total cellular protein - Rapid growth, simple and inexpensive media, appropriate fermentation tech nology, large scale cultivation
Drawbacks of E. coli Intracellular accumulation of proteins in the cytoplasm complicate downstream processing compared to extracellular production additional primary processing steps : cellular homogenization, subsequent removal of cell debris by filtration or centrifugation extensive purification steps to separate the protein of interest
Inclusion body (insoluble aggregates of partially folded protein) formation via intermolecular hydrophobic interactions - high level expression of heterologous proteins overload the normal cellular protein-folding mechanisms - Nonetheless, inclusion body displays one processing advantage easy and simple isolation by single step centrifugation denaturation using 6 M urea refolding via dialysis or diafiltration - Prevention of inclusion body formation - growth at lower temperature (30 oC)
- expression with fusion partner : GST, Thioredoxin, GFP, - high level co-expression of molecular chaperones Inability to undertake post-translational modification, especially glycosylatio n : limitation to the production of glyco-proteins Typical examples of glyco-proteins Presence of lipopolysaccharide on its surface : pyrogenic nature more complicate purification procedure Yeast Saccharomyces cerevisiae, Pichia pastoris : Major use : Glycoproteins, Alcohols
Major advantages - Well-characterized molecular biology easy genetic manipulation - Regarded as GRAS-listed organisms (generally regarded as safe) Long history of industrial applications ( e.g., brewing and baking) - Fast growth in relatively inexpensive media, outer cell wall protects them fr om physical damage - Suitable industrial scale fermentation equipment/technology is already avail able - Post-translational modifications of proteins, especially glycosylation Drawbacks
- Glycosylation pattern usually differs from the pattern observed in the nativ e glycoprotein : highly mannosylation pattern -Low expression level of heterologous proteins : < 5 % Many therapeutic proteins are produced in Yeast Fungal production system Aspergillus niger Mainly used for production of industrial enzymes : a-amylase, glucoamylase, cellulase, lipase, protease etc..
Advantages - High level expression of heterologous proteins - Secretion of proteins into extracellular media easy and simple separation procedure - Post-translational modifications : glycosylation - different glycosylation pattern compared to that in human Animal cells Major advantage : Post-translational modifications, especially glycosylation Chinese Hamster Ovary (CHO) and Baby Hamster Kidney (BHK) cells Many glycoproteins are produced in animal cells
Drawbacks - Complex nutritional requirements : Many kinds of growth factors Expensive Complicate the purification procedure - Slow growth rate - Far more susceptible to physical damage or contamination - Increased production costs CHO cells Transgenic animals
Transgenic animal : live bioreactor Generation of transgenic animals : Direct microinjection of exogenous DNA into an egg cell Stable integration of the DNA into the genetic complement of the cell After fertilization, the ova are implanted into a surrogate mother Transgenic animal harboring a copy of the transferred DNA
In order for the transgenic animal system to be practically useful, the recombina nt protein must be easily separable from the animal Simple and easy way is to produce a target protein in a mammary gland Simple recovery of a target protein from milk Mammary-specific expression : Fusing the gene of interest with the promotercontaining regulatory sequence of a gene coding for a milk-specific protein
ex) Regulatory sequences of the whey acid protein (WAP, the most abundant p rotein in the milk), -casein, - and -lacto-globulin genes ex) Production of tPA in the milk of transgenic mice - Fusion of the tPA gene to the upstream regulatory sequence of the mouse whey acidic protein - More practical approach : production of tPA in the milk of transgenic goats Production of proteins in the milk of transgenic animals
Goats and sheep : Most attractive host system - High milk production capacities - Ease of handling and breeding - Ease of harvesting of crude product : simply requires the animal to be milked - Pre-availability of commercial milking systems with maximum process hygiene - Low capital investment : relatively low-cost animals replace high-cost tradition al equipment and low running costs - High expression levels of proteins are potentially attained : > 1 g protein/liter milk - On-going supply of product is guaranteed by breeding - Ease downstream (separation and purification) processing due to well-charact
erized properties of major native milk proteins Issues to be addressed for practical use - Variability of expression levels - Different post-translational modifications, especially glycosylation, from that in human - Significant time lag between the generation of a transgenic embryo and comme ncement of routine product manufacture : - Gestation period ranging from 1 month to 9 months
- Requires successful breeding before beginning to lactate - Overall time lag : 3 years in the case of cows, 7 months in the case of rabbits - Inefficient and time-consuming in the use of the micro-injection technique to int roduce the desired gene into the egg Another approaches - Use of replication-defective retroviral vectors : consistent delivery of a gene int o cells and chromosomal integration - Use of nuclear transfer technology
Manipulation of donor cell nucleus so as to harbor a gene coding for a target protein Substitution of genetic information in un unfertilized egg with donor genetic i nformation Transgenic sheep, Polly and Molly, producing human blood factor IX, in 1990s Nuclear transfer technology No therapeutic proteins produced in the milk of transgenic animals had be
en approved for general medical use Alternative approach : production of therapeutic proteins in the blood of transgenic pigs and rabbits - Drawbacks - Relatively low volumes of blood - Complicate downstream processing - Low stability of proteins in serum
Transgenic plants Expression of heterologous proteins in plant : Introduction of foreign genes into the plant species : Agrobacterium-based vector-mediated gene transfer - Agarobacterium tumefaciens, A. rhizogenes : soil-based plant pathogens - When infected, a proportion of Agarobacterium Ti plasmid is trans-located t o the plant cell and is integrated into the plant cell genome - Expression of therapeutic proteins in plant tissue Transgenic plants
Potentially attractive recombinant protein producer - Low cost of plant cultivation - Harvest equipment/methodologies are inexpensive and well established - Ease of scale-up: Proteins expressed in seeds are generally stably expressed - Plant-based systems are free of human pathogens(e.g., HIV) Disadvantages - Variable/low expression levels of proteins - Potential occurrence of post-translational gene silencing
( a sequence specific mRNA degradation mechanism) - Different glycosylation pattern from that in human - Seasonal/geographical nature of plant growth Most likely focus of future transgenic plant : Production of oral vaccines in edible plants or fruit, such as tomatoes and bananas - Ingestion of transgenic plant tissue expressing recombinant sub-unit vaccines indu ces the production of antigen-specific antibody responses Direct consumption of plant material provides an inexpensive, efficient and techni
cally straightforward mode of large-scale vaccine delivery Several hurdles - Immunogenicity of orally administered vaccines vary widely - Stability of antigens in the digestive tract varies widely - Genetics of many potential systems remain poorly characterized Inefficient transformation systems and low expression levels Insect cell-based system
Laboratory scale production of proteins Infection of cultured insect cells with an engineered baculovirus ( a viral family that naturally infects insects) carrying the gene coding for a target protein Most commonly used systems
- Silkworm virus Bombyx mori nuclear polyhedrovirus(BmNPV) in conjunction with cultured silkworm cells: - Virus Autographa californica nuclear polyhedrovirus(AcNPV) in conjunction with cultured armyworm cells Advantages - High level intracellular protein expression - Use of strong promoter derived from the viral polyhedrin: ~30-50 % of total intracellular protein
- Cultivation at high growth rate and less expensive media than animal cell lines - No infection of human pathogens, e.g., HIV Drawbacks - Low expression level of targeted extracellular production of protein - Glycosylation patterns : incomplete and different
No therapeutic protein approved for human use Alternative insect cell-based system Use of live insects - Live caterpillars or silkworms Infection with the engineered baculovirus vector Ex) Veterinary pharmaceutical company, Vibragen Owega - Use of silkworm for the production of feline interferon - Direct injection of a vector containing a gene coding for a target protein
- protein expression level: ~ 0.4 mg protein /each Guides to Good Manufacturing Practice Producer must comply with the most rigorous standards to ensure consist ent production of a safe and effective therapeutic agents Principles underlining such standards are summarized in publications whi
ch detail Good Manufacturing Practice (GMP) - EU guide to Good Manufacturing Practice for Medicinal Products Producers must be familiar with the principles, and they are legally oblige d to ensure adoption of these principles to their specific bioprocess Regulatory authority assesses compliance of the producer with the princi
ples by undertaking regular inspections of the facility Principles outlined in GMP An adequate number of sufficiently qualified, experiences pe rsonnel Key personnel, such as the heads of production and quality c ontrol, must be independent of each other Personnel should have well-defined job descriptions, and sho uld receive adequate training Issues of personal hygiene should be emphasized to prevent product contamination
Premises and equipment All premises and equipments should be designed, operated, and serviced t o carry out their intended functions Facility and equipment should be designed and used to avoid cross-conta mination or mix-up between different products
Sufficient storage area must be provided, and clear demarcation must exist between storage zones for materials at different levels of processing (raw materials, partially processes products, finished products etc..) Quality control labs must be separated from production, and must be desi gned equipped to a standard allowing them to fulfill their intended functio
n Some of the principles outlined in the guide are sufficiently general to re nder them applicable to most manufacturing industries. Most of principles outlined in guides to GMP are equally as applicable to the manufacture of traditional pharmaceuticals as to new ones
Many of the guidelines are specific : guidelines relating to the requireme nt for dedicated facilities when manufacturing specific products Manufacturing facility Appropriate design and layout of the facility required for prod uction of pharmaceuticals : crucial to the production of safe an d effective medicines
Injectable products - Clean room technology - Generation of ultra pure water - Maintenance of non-critical areas : storage, labeling, and packing areas Clean rooms Environmentally controlled areas for injectable/sterile drugs: specifically des
igned to protect the product from contamination Designed in a way that allows tight control of entry of all substances ( e.g., e quipment, personnel, in-process product, air etc..) Installation of high efficiency particulate air(HEPA) in the ceilings : - Layers of high-density glass fiber : depth-filter
- Flow pattern of HEPA-filtered air - Air is pumped into the room via the filters, generating a constant downward sweeping motion Flow motion promotes continued flushing from room of any particulates gene rated during processing Clean rooms with various levels of cleanliness - Classified based on the number of airborne particles and viable microorganisms in the ro
om - A, B, C, D grades in order of decreasing cleanliness in Europe - Class 100 (grade A/B), Class 10,000(grade C), Class 100,000 (grade D) in the US A B C D Max permitted No. of particles / m3 3,500
3,500 350,000 3,500,000 Max. permitted No. of microorganisms <1 5 100 500 Water for bioprocess and therapeutic agents
Water : One of the most important raw materials : used as a basic ingredient - Cell culture media, buffers, solvent in extraction and purification, solvent in preparation of liquid form and freeze-dried products - Used for ancillary processes : cleaning - ~ 30,000 liters of water : production of 1 kg of a recombinant products by microbial system - Generation of water of suitable purity : central to successful operation of fac ility
Purified water : - Used as the solvent in the manufacture of aqueous-based oral products (e.g., cough mixtures, ) - Used for primary cleaning of some process equipment/clean room floors gene ration of steam in the facilities, autoclaves - Used for cell culture media Water for injection (WFI) - Extensive application in biopharmaceutical manufacturing - Extraction/homogenization/chromatography buffers rinsing process equipme
nt coming into direct contact with the products Generation of purified water and WFI Generated from potable water Removal of impurities found in potable water Multi-step purification procedure for purified water and WFI: Monitoring o f each step : continuous measurement of the resistivity of the water
Increased resistivity with purity 1- 10 M Filters for filtration : 0.22 m, 0,45 m of pore size Reverse osmosis (RO) membrane : semi-permeable membrane (permeable to the solvent, water, but impermeable to solute, i.e., contaminant
General process Depth filtration Organic Trap Activated charcoal Anion exchange Cation exchange Filtration Distillation or reverse osmosis Water for injection Documentation Adequate documentation : essential part of GMP
Essential in order to - Help prevent errors/misunderstandings associated with verbal communi cation - Facilitate the tracing of the manufacturing history of any batch of produc t - Ensure reproducibility in all aspects of bioprocess
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