The design and quality of the binding reagents , along with other test conditions such as sample quality, play a key role in establishing the test specificity and selectivity, which determine the proportion of false positive and false negative results. Although the recombinant protein mass needed for diagnostic testing is relatively small , the number of tests needed for the global population is massive, given that many individuals will need multiple and/or frequent tests. For example, 8 billion tests would require a total of ~2.5 kg purified recombinant protein, which is not an insurmountable target. However, although the production of soluble trimeric full-length S protein by transient transfection in HEK293 cells has been improved by process optimization, current titers are only ~5 mg L−1 after 92 h . Given a theoretical recovery of 50% during purification, a fermentation volume of 1,000 m3 would be required to meet the demand for 2.5 kg of this product. Furthermore, to our knowledge, the transient transfection of mammalian cells has only been scaled up to ~0.1 m3 . The transient expression of such protein-based diagnostic reagents in plants could increase productivity while offering lower costs and more flexibility to meet fluctuating demands or the need for variant products. Furthermore, diagnostic reagents can include purification tags with no safety restrictions, and quality criteria are less stringent compared to an injectable vaccine or therapeutic. Several companies have risen to the challenge of producing such reagents in plants, including Diamante , Leaf Expression Systems ,4×8 botanicare tray and a collaborative venture between PlantForm, Cape Bio Pharms, Inno-3B, and Microbix.
Resilience is the state of preparedness of a system, defining its ability to withstand unexpected, disastrous events , and to preserve critical functionality while responding quickly so that normal functionality can be restored . The concept was popularized by the 2011 Fukushima nuclear accident but received little attention in the pharmaceutical sector until COVID-19. Of the 277 publications retrieved from the National Library of Medicine22 on July 9th 2020 using the search terms “resilience” and “pandemic,” 82 were evenly distributed between 2002 and 2019 and 195 were published between January and July 2020. Resilience can be analyzed by defining up to five stages of a resilient system under stress, namely prevent, prepare, protect, respond, and recover . Here, prevent includes all measures to avoid the problem all together. In the context of COVID-19, this may have involved the banning of bush meat from markets in densely populated areas . The prepare stage summarizes activities that build capacities to protect a system and pre-empt a disruptive event. In a pandemic scenario, this can include stockpiling personal protective equipment but also ensuring the availability of rapid-response bio-pharmaceutical manufacturing capacity. The protect and respond stages involve measures that limit the loss of system functionality and minimize the time until it starts to recover, respectively. In terms of a disease outbreak, the former can consist of quarantining infected persons, especially in the healthcare sector, to avoid super-spreaders and maintain healthcare system operability . The response measures may include passive strategies such as the adjustment of legislation, including social distancing and public testing regimes, or active steps such as the development of vaccines and therapeutics . Finally, the recover phase is characterized by regained functionality, for example by reducing the protect and response measures that limit system functionality, such as production lockdown.
Ultimately, this can result in an increased overall system functionality at the end of a resilience cycle and before the start of the next “iteration” . For example, a system such as society can be better prepared for a pandemic situation due to increased pharmaceutical production capacity or platforms like plants. From our perspective, the production of recombinant proteins in plants could support the engineering of increased resilience primarily during the prepare and respond stages and, to a lesser extent, during the prevent and recover stages . During the prepare stage, it is important to build sufficient global production capacity for recombinant proteins to mount a rapid and scalable response to a pandemic. These capacities can then be used during the response stage to produce appropriate quantities of recombinant protein for diagnostic , prophylactic , or therapeutic purposes as discussed above. The speed of the plant system will reduce the time taken to launch the response and recovery stages, and the higher the production capacity, the more system functionality can be maintained. The same capacities can also be used for the large-scale production of vaccines in transgenic plants if the corresponding pathogen has conserved antigens. This would support the prevent stage by ensuring a large portion of the global population can be supplied with safe and low-cost vaccines, for example, to avoid recurrent outbreaks of the disease. Similarly, existing agricultural capacities may be re-directed to pharmaceutical production as recently discussed . There will be indirect benefits during the recover phase because the speed of plant-based production systems will allow the earlier implementation of measures that bring system functionality back to normal, or at least to a “new or next normal.”
Therefore, we conclude that plant-based production systems can contribute substantially to the resilience of public healthcare systems in the context of an emergency pandemic.The cost of pharmaceuticals is increasing in the United States at the global rate of inflation, and a large part of the world’s population cannot afford the cost of medicines produced in developed nations23 . Technical advances that reduce the costs of production and help to ensure that medicines remain accessible, especially to developing nations, are, therefore, welcome. Healthcare in the developing world is tied directly to social and political will, or the extent of government engagement in the execution of healthcare agendas and policies . Specifically, community-based bodies are the primary enforcers of government programs and policies to improve the health of the local population . Planning for the expansion of a bio-pharmaceutical manufacturing program to ensure that sufficient product will be available to satisfy the projected market demand should ideally begin during the early stages of product development. Efficient planning facilitates reductions in the cost and time of the overall development process to shorten the time to market, enabling faster recouping of the R&D investment and subsequent profitability. In addition to the cost of the API, the final product form , the length and complexity of the clinical program for any given indication , and the course of therapy have a major impact on cost. The cost of a pharmaceutical product, therefore, depends on multiple economic factors that ultimately shape how a product’s sales price is determined . Product-dependent costs and pricing are common to all products regardless of platform. Plant-based systems offer several options in terms of equipment and the scheduling of upstream production and DSP, including their integration and synchronization . Early process analysis is necessary to translate R&D methods into manufacturing processes . The efficiency of this translation has a substantial impact on costs, particularly if processes are frozen during early clinical development and must be changed at a subsequent stage. Process-dependent costs begin with production of the API. The manufacturing costs for PMPs are determined by upstream production and downstream recovery and purification costs. The cost of bio-pharmaceutical manufacturing depends mostly on protein accumulation levels,flood tables for greenhouse the overall process yield, and the production scale. Techno-economic assessment models for the manufacture of bio-pharmaceuticals are rarely presented in detail, but analysis of the small number of available PMP studies has shown that the production of bio-pharmaceuticals in plants can be economically more attractive than in other platforms . A simplified TEA model was recently proposed for the manufacture of mAbs using different systems, and this can be applied to any production platform, at least in principle, by focusing on the universal factors that determine the cost and efficiency of bulk drug manufacturing .Minimal processing may be sufficient for oral vaccines and some environmental detection applications and can thus help to limit process development time and production costs . However, most APIs produced in plants are subject to the same stringent regulation as other biologics, even in an emergency pandemic scenario . It is, therefore, important to balance production costs with potential delays in approval that can result from the use of certain process steps or techniques.
For example, flocculants can reduce consumables costs during clarification by 50% , but the flocculants that have been tested are not yet approved for use in pharmaceutical manufacturing. Similarly, elastin-like peptides and other fusion tags can reduce the number of unit operations in a purification process, streamlining development and production, but only a few are approved for clinical applications . At an early pandemic response stage, speed is likely to be more important than cost, and production will, therefore, rely on well characterized unit operations that avoid the need for process additives such as flocculants. Single-use equipment is also likely to be favored under these circumstances, because although more expensive than permanent stainless-steel equipment, it is also more flexible and there is no need for cleaning or cleaning validation between batches or campaigns, allowing rapid switching to new product variants if required. As the situation matures , a shift toward cost-saving operations and multi-use equipment would be more beneficial.An important question is whether current countermeasure production capacity is sufficient to meet the needs for COVID-19 therapeutics, vaccines, and diagnostics. For example, a recent report from the Duke Margolis Center for Health Policy24 estimated that ~22 million doses of therapeutic mAbs would be required to meet demand in the United States alone , assuming one dose per patient and using rates of infection estimated in June 2020. The current demand for non-COVID-19 mAbs in the United States is >50 million doses per yea, so COVID-19 has triggered a 44% increase in demand in terms of doses. Although the mAb doses required for pre-exposure and post-exposure COVID-19 treatment will not be known until the completion of clinical trials, it is likely to be 1–10 g per patient based on the dose ranges being tested and experience from other disease outbreaks such as Ebola . Accordingly, 22–222 tons of mAb would be needed per year, just in the United States. The population of the United States represents ~4.25% of the world’s population, suggesting that 500–5,200 tons of mAb would be needed to meet global demand. The combined capacity of mammalian cell bioreactors is ~6 million liters, and even assuming mAb titers of 2.2 g L−1, which is the mean titer for well-optimized large scale commercial bioreactors , a 13-day fed-batch culture cycle , and a 30% loss in downstream recovery, the entirety of global mammalian cell bioreactor capacity could only provide ~259 tons of mAb per year. In other words, if the mammalian cell bioreactors all over the world were repurposed for COVID-19 mAb production, it would be enough to provide treatments for 50% of the global population if low doses were effective but only 5% if high doses were required. This illustrates the importance of identifying mAbs that are effective at the lowest dose possible, production systems that can achieve high titers and efficient downstream recovery, and the need for additional production platforms that can be mobilized quickly and that do not rely on bioreactor capacity. Furthermore, it is not clear how much of the existing bioreactor capacity can be repurposed quickly to satisfy pandemic needs, considering that ~78% of that capacity is dedicated to in-house products, many to treat cancer and other life-threatening diseases . The demand-on-capacity for vaccines will fare better, given the amount of protein per dose is 1 × 104 to 1 × 106 times lower than a therapeutic mAb. Even so, most of the global population may need to be vaccinated against SARS-CoV-2 over the next 2–3 years to eradicate the disease, and it is unclear whether sufficient quantities of vaccine can be made available, even if using adjuvants to reduce immunogen dose levels and/or the number of administrations required to induce protection. Even if an effective vaccine or therapeutic is identified, it may be challenging to manufacture and distribute this product at the scale required to immunize or treat most of the world’s population . In addition, booster immunizations, viral antigen drift necessitating immunogen revision/optimization, adjuvant availability, and standard losses during storage, transport, and deployment may still make it difficult to close the supply gap.