Plants, like human and animal cells, are capable of producing complex and folded proteins, and plant-based protein expression technology may provide advantages over cell-culture systems. Bio-Manguinhos/Fiocruz, the technical scientific unit of the Oswaldo Cruz Foundation (Fiocruz), which produces and develops immunobiologicals for public health needs, primarily in support of programs run by the Brazilian Ministry of Health, is taking plant-based expression technology to the next level. It recently signed an agreement with GE Healthcare for the design of a new plant-based multipurpose biopharmaceutical and vaccine manufacturing facility using a plant-based expression and production platform from iBio, a developer of such systems.
|Figure 1 Automated plant agro-infiltration equipment. Image courtesy of iBio.|
Plant-based protein expression is not new technology. The first human test of a therapeutic protein made in plants was conducted by NeoRx Corp. in 1997, according to Robert Erwin, president of iBio. The experimental cancer therapeutic Avicidin incorporated a monoclonal antibody produced in transgenic plants by a unit of Monsanto. Although there were no problems with the quality of the plant-made antibody itself, the Avicidin product was not ultimately commercialized. About the same time, Planet Biotechnology tested a transgenic plant-derived antibody for the prevention of tooth decay in collaboration with Guy’s Hospital in London.
Transgenic plants have since been used to produce several products that have entered human clinical trials, including gastric lipase, interferon, and insulin. Plant-produced human glucocerebrosidase, produced in transgenic carrot cells by the biopharmaceutical company Protalix BioTherapeutics, received FDA approval. In May 2012, Protalix and its partner received FDA approval for Elelyso (taliglucerase alfa), a plant cell-produced glucocerebrosidase enzyme replacement therapy (ERT) for the long-term treatment of adult patients with Type 1 Gaucer disease. Protalix is also developing an oral form of glucocerebrosidase; Elelyso is parenterally delivered. Viral vectors were used to produce proteins for individualized treatment of non-Hodgkin’s lymphoma in a Phase I clinical trial conducted in 2002 (1), and Icon Genetics is currently conducting a Phase I clinical trial of individualized cancer therapy based on its transient expression technology for producing proteins in plants.Numerous advantages
Compared to the traditional use of animal cells grown in bioreactors, plant-based protein expression systems have several advantages, according to Erwin. Because they do not require the time-consuming identification and isolation of high-producing cell clones that need to be scaled up for manufacture, plant-based systems can be operational in much less time. In addition, the plants are grown in a soil-free, hydroponic medium under strict climatic and lighting controls for the highest degrees of reproducibility (see Figure 1). As a positive consequence, no animal-derived products or growth factors are used, thereby eliminating the risk of the introduction of human pathogens into the manufacturing process. Thus, the expensive aseptic liquid-handling process steps for cell culture are not required.
The iBioLaunch technology from iBio is a third-generation plant-based protein expression platform that uses unmodified green plants. The first-generation system, which some companies still use, relies on transgenic (i.e., genetically modified organisms) plants, a process that is slow and relatively low in yield. Second-generation systems, also still used by some companies, are based on the transient virus-delivery of genes into nontransgenic plants. Although this technology works rapidly, there are yield constraints and target product-size limitations that restrict its applicability, according to Erwin.
“Harnessing the combined biological features of bacterial, viral, and plant biology to achieve the speed of transient production without the yield and size limitations of older technology, iBioLaunch technology has the advantages of speed, simplicity, flexibility, and lower cost,” Erwin asserts. He says that unlike more conventional systems that fundamentally alter a host cell’s DNA, there is no need to isolate and expand rare, high-producing cell clones to production level. A gene of interest can be cloned and inserted into the iBioLaunch vectors and be ready for production at scale within a month’s time. In addition, the transient nature of the expression system allows the accumulation of massive amounts of desired protein over a four- to seven-day period, after which time purification can begin.
“The simplicity of the iBioLaunch system comes from the use of whole plants for the manufacture of proteins,” explains Erwin. “These plants can be grown in chemically defined media in the open air or climatically controlled greenhouses and do not require the expensive aseptic-culture systems required to prevent contamination of cell-culture production methods. Furthermore, the system is highly flexible, thereby allowing the expression of vaccine antigens, monoclonal antibodies, replacement enzymes, blood-cell growth factors, and many other products that cannot be produced by more traditional expression systems,” he adds. Other important benefits include the ability to produce proteins that are difficult to obtain using other methods and the ability to scale-up capacity readily, for example, in developing treatments for pandemic disease. Also, using whole plants to provide the biomass for manufacturing obviates the need for bioreactors and media and also reduces development times associated with traditional cell-culture manufacturing.Validated technology
Erwin notes that various proteins have been successfully produced with iBio’s platform, including antibodies, interferons and cytokines, growth factors, protease inhibitors, clotting factors, and enzymes for replacement therapy (specifically alpha-galactosidase A). In addition, a variety of antigens for vaccines against diseases, such as influenza, anthrax, malaria, yellow fever, sleeping sickness, plague, and human papilloma virus have been produced, as well as several therapeutic antibodies for the treatment of acute influenza and anthrax infections. “Virtually any protein that can be produced in prokaryotic or other eukaryotic expression systems can be made in plants with the iBioLaunch platform with significant cost advantages,” Erwin states.
The iBioLaunch technology was validated through the construction of a cGMP pilot manufacturing facility in Newark, Delaware that has provided clinical-trial material for multiple FDA-approved studies, according to Erwin. Human testing of products made using the iBioLaunch platform began in 2010 with the initiation of Phase I clinical trials of an H5 avian influenza vaccine sponsored by the Bill & Melinda Gates Foundation and a vaccine for H1N1 influenza sponsored by the US Defense Advanced Research Projects Agency, the results of which were published in 2012 (2).
Bio-Manguinhos/Fiocruz is interested in and investing in the iBio plant-based technology." “ "In order to accomplish our mission and to meet the Brazilian Ministry of Health’s demands, we are constantly investing in innovative technologies,” says Artur Couto, director of Bio-Manguinhos/Fiocruz. “The agreement with GE Healthcare is important because it will allow us to build a new facility based on a very innovative platform and address an important need of the Brazilian Ministry of Health,” he says.
|Figure 2 Stainless steel growth racks. Image courtesy of iBio|
Bio-Manguinhos/Fiocruz also has an additional co-development agreement with iBio and its research and development collaborator Fraunhofer USA Center for Molecular Biotechnology (FCMB), which will continue to play a key role in advancing iBioLaunch, according to Erwin. The contract with Bio-Manguinhos/Fiocruz in Brazil for the design of a new plant-based biomanufacturing facility is the first for the global alliance between GE Healthcare and iBio, which was announced in 2012. The agreement with Bio-Manguinhos/Fiocruz and GE Healthcare for the new plant-based production facility was announced in April 2013.
Although the details of the process and facility design are confidential, a typical plant would be based on the following approach. The front-end of the process would involve technology proprietary to iBio, including the production of green-plant biomass using hydroponic systems, the transfer of appropriate recombinant protein expression vectors into the plants, and the extraction of protein from the biomass (See Figure 2). Downstream operations, including separation and purification of the target protein and final product formulation, could be based on the proprietary products and expertise of GE Healthcare.
1. A. A. McCormick et al., PNAS, 105 (29), 10131–10136 (2008).
2. J. A. Chichester et al., Viruses 4 (11), 3227-3244 (2012).