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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary 3 Vaccines: Research, Development, Production, and Procurement Issues OVERVIEW Vaccines not only afford the best protection against infectious disease but can serve as strong deterrence factors as well. From a bioterrorist perspective, vaccine-resistant agents are more difficult to engineer than drug-resistant agents. But the potential market has been too small and uncertain to encourage the vaccine industry to make large investments in research, development, and manufacturing of new products. This is alarming considering the eight to ten years often needed to develop a new vaccine, compared to only two to three years to develop a new bioweapon. Even among the four major vaccine manufacturers, there is insufficient production capacity. It was suggested during this session that in order to move animal and clinical testing forward, incentives need to be established to reduce the current challenges of vaccine development; vaccine production priorities need to be set and a central office or leader authorized to declare top priorities; and the role of the major vaccine manufacturers needs to be facilitated by clear directions and active collaboration between industry and government. The use of vaccines as a civilian biodefense measure presents multiple challenges that are quite different from those of vaccine use by the military. Much of the challenge is due to the fact that the threats are uncertain and riskbenefit information difficult to assess. The very nature of terrorism produces a high level of uncertainty about what to expect and how to prepare. Additionally, DoD has developed vaccines to be used in normal healthy adults between the ages of 18 and 65, not pediatric, geriatric, immunocompromised or other subsets of the civilian population. Currently, there is no policy in place for immunizing
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary the civilian population as a bioweapons defense measure, however several government agencies are working at unprecedented speed to put the correct policies into place. The threat of a global pandemic makes smallpox one of the top vaccine priorities. An aggressive clinical development plan is currently in place; its goal is to build the stockpile with enough vaccine to protect the entire country within the year. The vaccine immune globulin (VIG) supply also needs to be expanded. Long-term goals include developing a safer vaccine that can be used in immunocompromised or other at-risk individuals. Anthrax vaccine is another top priority. As of May 2001, over two million doses of the current anthrax vaccine have been administered to over 500,000 individuals, mostly military personnel. But there is an urgent need for more anthrax vaccine for the immunization of high risk civilian populations, as well as for use in medical management of exposed individuals in conjunction with antibiotics. Currently, there is only one manufacturer of licensed anthrax vaccine, but production is limited because of regulatory problems. Several commercial firms have offered to aid in scaled-up production, but the inherent variability of the manufacturing process and the risk of failure when scaling up so rapidly to such a high volume could create problems. Other mid to long-term anthrax vaccine needs include the development of a second-generation vaccine (e.g., a recombinant protective antigen vaccine) as well as better delivery technologies (e.g., plasmid DNA). Of lesser importance than vaccines against smallpox and anthrax are vaccines against bacterial infections for which antibiotics can be used and other viral agents that, for the present, seem to be a lesser threat. A recent independent review of DoD’s vaccine acquisition program recommended an integrated approach between DoD and industry and the establishment of a dedicated national vaccine production facility that allows for maximal flexibility and expandable manufacturing capability for the production of various types of vaccines. Whether the proposed facility will be governmentowned and contractor-operated or contractor-owned and contractor operated is open for discussion. Ebola virus provides a useful paradigm for how a molecular-level understanding of the pathogenesis of a virus can be used to develop a new vaccine for an infectious agent that would otherwise be difficult to tackle. This type of molecular genetics approach can reveal possible targets for antiviral drugs as well. For example, recent studies have shown that one of the domains of the ebola virus forms a coil-to-coil structure that is similar to structures found in other viruses, including HIV and influenza. This similarity suggests that the approach being used to develop products for antiviral use against HIV may also be useful for targeting the coil-to-coil region of ebola virus. In fact, targeting this coil-to-coil structure may prove to be a useful general antiviral strategy against many different viruses.
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary Other vaccine issues that were raised during this session include: Improving the usefulness of DNA vaccines, which work well in rodents but not primates. Consideration of combination vaccines, for example can we use what we have learned from ebola to make a combination vaccine for use against all hemorrhagic fevers? Application of genomics to vaccine research could have, for example if we could use the new high throughput technology to identify genomic biomarkers for vaccine efficacy, then we could use these biomarkers in the future to move forward more quickly toward licensure. The need for a strong infrastructure to receive the intense flow of resources that would be expected with a rapid deployment of vaccines in response to outbreaks. The need for ways to accelerate vaccine FDA licensure without compromising product safety, for example use of the proposed animal efficacy rule for products that are either not feasible or ethical for human efficacy trials. VACCINES FOR THREATENING AGENTS: ENSURING THE AVAILABILITY OF COUNTERMEASURES FOR BIOTERRORISM Philip K. Russell,* M.D. Special Advisor on Vaccine Development and Production Office of the Secretary Department of Health and Human Services Recent events have brought the subject of vaccines as a defense against bioterrorism into very sharp focus. We have been forced to take action in an area that, for the civilian sector, had previously been largely an academic debate and planning exercise with inadequate definitive action. We have changed from a nation of skeptics concerning the threat of bioterrorism to a nation of believers. Several government agencies are working at unprecedented speed to acquire the needed vaccines and put the correct policies into place for utilization. However, the use of vaccines for defense against bioterrorism presents multiple challenges that are quite different from the traditional public health use of vaccines for protection against endemic or epidemic diseases. The issues are also quite different from those faced by the armed forces. The appropriate use of vaccines as a defense against bioterrorism presents major challenges in public policy development as well as public education. The ongoing public debates in the media highlight the complexity of the issues and reveal the widespread lack * This statement reflects the professional view of the author and should not be construed as an official position of the Department of Health and Human Services.
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary of understanding of the limitations of the current vaccines, especially vaccinia vaccine. For example, there is a call for widespread vaccination against smallpox but, in contrast, there is much misinformation and inappropriate fear about the effects of anthrax vaccine. Some of the challenges involved with developing vaccine policies for defense against bioterrorism lie in the uncertainty of the threats. In contrast, policies for the use of vaccines against naturally-occurring disease threats are based on a wealth of historical and current epidemiologic information about disease burden and potential. Additionally, there is extensive data available on the safety of widely used vaccines that can be used to confidently assess risk benefit and cost effectiveness. In the case of agents of bioterrorism, however, risk assessment is much more difficult. The great difficulty in obtaining timely and reliable intelligence on the threat of biologic terrorism is a major part of the problem. Critical policy decisions—such as which vaccines will be needed, how large the stockpiles should be, and how the vaccine should be used—are greatly influenced by perceptions of threat. The very nature of terrorism produces a high level of uncertainty about what to expect and prepare for, and there is a wide and varying spectrum of perceived threats. Obtaining the vaccines that are needed to protect our military and civilian populations depends entirely on effective government action. The potential market has been too small, at least up to the present time, to encourage the vaccine industry to make the large investments needed in research, development and manufacturing facilities. This has changed dramatically in the past two months. Nevertheless, the current situation is a result of past misjudgments, which resulted in insufficient government investment in vaccine research and development, and manufacturing capacity. There is an urgent need for rapid progress in R&D, manufacturing, and licensing processes, all of which are painfully slow processes when done by the usual methodologies. Vaccines have varying usefulness in defense against bioterrorism. At the top of the list is the need for smallpox vaccine to prevent an outbreak from becoming a catastrophic global pandemic. Both smallpox and anthrax vaccines would be very useful in the medical management of exposed individuals, if the vaccines were readily available and placed in geographic proximity to multiple centers for distribution. Less important to the civilian populations are vaccines against bacterial agents that can be managed with antibiotics and viral agents which, at least for the present, seem to be lesser threats. These include plague, tularemia, hemorrhagic fever viruses, alphavirus encephalidities, Rift Valley fever, and others. However, several of these vaccines should be available for both civilian and military use. A government-owned production facility may be the best means for meeting the needs of these lower priority vaccines which will probably, at least initially, be made in much smaller quantities than smallpox and anthrax vaccines.
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary Smallpox Vaccine The acquisition of a smallpox vaccine stockpile for civilian use started in 1999, with an Acambis contract for 40 million doses which now has been increased to 54 million doses. The seed virus was developed by cloning a New York City Board of Health strain derived from Wyeth Dry Vax. Animal model studies indicate that this strain appears to be somewhat less neurovirulent than the parent virus. The clinical development plan is aggressive; the phase I clinical trial should occur, as planned, in the latter part of January 2002. A very rapid procurement action has been in progress over the past weeks. The goal is to stockpile enough smallpox vaccine to protect the entire nation within the year. The response from the vaccine industry has been very heartening and has provided excellent options for utilizing existing manufacturing capacity to meet current requirements. Every effort will be made by CDC, FDA and NIH to assure that these contractors succeed to meet goals, time lines, and regulatory requirements. This will require truly unprecedented coordination and responsiveness by both the manufacturers and the various agencies. Although the first step in building the smallpox vaccine stockpile is to ensure that vaccine manufacturing is underway, there are several other immediate issues that need to be addressed: Vaccination policy issues continue to be controversial. The CDC recently sent out a draft smallpox response plan to the states for comment. The plan calls for primary reliance on ring vaccination—the traditional method—to control an outbreak. The CDC has vaccinated 140 staff members who are most likely to be involved in investigating an outbreak, but no further vaccination with potential responders or health care providers is planned at this time. Laboratory personnel working with pox viruses will, of course, continue to be vaccinated. There is a need for more vaccine immune globulin (VIG) or VIG substitute to deal with the consequences of vaccination in immunosuppressed or other high risk subsets of the population. An interagency working group is currently exploring options for expanding the VIG supply. There is a need to develop a safer vaccine for use in immunosuppressed individuals, pregnant women, and other individuals for which the current vaccine is contraindicated. This will not only be a challenging research and development problem but also a challenging regulatory problem due to the difficulties in proving efficacy. Anthrax Vaccine The current licensed U.S. anthrax vaccine is a filtrate of culture media that contains a high level of PA (protective antigen) absorbed to alum; it probably contains small amounts of the other factors as well. An ongoing study at CDC is
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary testing immunization schedules that involve fewer than the currently recommended six doses for this vaccine. Conventional wisdom has it that the live attenuated vaccines used in Russia and China are too reactogenic to be licensed in the United States. Israeli scientists have published reports on animal studies of experimental vaccines engineered to over-express recombinant protective antigen, but no clinical data are available. The problems that the manufacturer has had with meeting regulatory criteria have limited the U.S. supply. A small amount of anthrax vaccine has been made available to DHHS by DoD, but that amount is far below what will be needed. There is an urgent need for a sufficient supply of anthrax vaccine for vaccinating high risk populations and for use as post-exposure vaccination in conjunction with antibiotics. There are several immediate issues that need to be addressed. The production method for current licensed vaccine must be scaled up. Several commercial firms have made informal proposals to do this. However, this is a high risk option because of the inherent variability of the manufacturing process and the high risk of failure when scaling up so rapidly to such a high volume. There needs to be more serious consideration of the applications of the various platform technologies—such as plasmid DNA, viral vectors, and a variety of other delivery technologies—that are being developed within the biotech industry. Finally, we need to accelerate development of a second generation vaccine. The time to availability could be shortened by overlapping large scale production with clinical trials. It has been suggested that we might have a stockpile of IND recombinant protective antigen (PA) vaccine within 18 months. This may be an achievable goal if all involved interests work in an effective, coordinated manner. A recombinant PA vaccine produced in E. coli will likely be the first to enter a phase I trial. In order to address this issue of a second generation vaccine, the National Institute of Allergy and Infectious Diseases has put together a team with contractor help. Efforts are underway to gather all available information on ongoing or planned development efforts for a second generation anthrax vaccine, and compile the information in a systematic fashion and convene several advisors to review the resulting data, findings, and policy options. This may involve a major research and development contract program similar to what exists for smallpox vaccine and which will hopefully build on the work that has been done by DoD and DoD-DHHS collaboration. It will hopefully involve some new players as well, including the large vaccine manufacturers. Although it is difficult to predict which particular options will receive aggressive support, there is nonetheless a system now in place that will hopefully pave the way for pursuing an effective strategy in a reasonable period of time. The speed at which a second generation anthrax vaccine is developed will depend on both the underlying science and the responsiveness of the vaccine industry to national needs.
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary THE DEPARTMENT OF DEFENSE AND THE DEVELOPMENT AND PROCUREMENT OF VACCINES AGAINST DANGEROUS PATHOGENS: A ROLE IN THE MILITARY AND CIVILIAN SECTOR? Anna Johnson-Winegar,* Ph.D. Deputy Assistant to the Secretary of Defense, Chemical and Biological Matters, U.S. Department of Defense Introduction In October 2001, the threat of bioterrorism became a reality. In support of this Forum’s efforts to identify the obstacles to preparing an optimal response to bioterrorism—particularly as it relates to the complexities of interaction between private industry, research and public health agencies, regulatory agencies, policymakers, academic researchers, and the public—this paper will highlight emerging opportunities for more effective collaboration as well as scientific and programmatic needs for responding to bioterrorism. The focus of this paper is on the potential opportunities and issues related to Department of Defense (DoD) support for the research, development, and production of biological defense vaccines for the military and civilian populations to protect against bioterrorist threats. This paper will address the following topics: Current medical biological defense research and development efforts; Current biological defense vaccine capabilities; Proposed national biological defense vaccine production facility; and, Issues related to the use of biological defense vaccines. In accordance with Congressional direction, DoD established a Joint Service Chemical and Biological Defense Program in 1994. The vision of the program is to ensure U.S. military personnel are the best equipped and best prepared force in the world for operating in future battlespaces that may feature chemical or biological contamination. The capabilities being developed for the military may have applicability to protection of civilians, especially as the military mission may increasingly support homeland security. Vaccines to protect against biological agents provide one critical capability to protect against the threat. Medical Biological Defense Research and Development Efforts The primary research program for the development of biological defense vaccines to protect U.S. forces is the Medical Biological Defense Research Pro- * The information provided in this paper reflects the professional view of the author and not an official position of the U.S. Department of Defense.
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary gram (MBDRP). In developing countermeasures to biological agents, the MBDRP uses a technical approach that focuses on four areas: Identify mechanisms involved in disease process; Develop and evaluate products (vaccines or drugs) to prevent or counter effects of toxins, bacteria, viruses, and genetically engineered threats; Develop methods to measure effectiveness of countermeasures in animal models that predict human response; and, Develop diagnostic systems and reagents. Biological defense vaccines are being developed to counter viruses, toxins, bacteria, and genetically engineered biological threat agents. Research activities start with basic research activities and proceed through the following steps, as research demonstrates successful candidates: (1) construction of the infectious clone, (2) identification of attenuating mutations, (3) construction of vaccine candidates, (4) testing in rodent models, (5) testing in non-human primates, (6) final selection, and (7) formulation. The formulated production may then become a candidate for an Investigational New Drug (IND) application for transition to advanced development and clinical trials, then ultimately licensed production. An example of a product being developed within the MBDRP is the Next Generation Anthrax Vaccine. In cooperation with the National Institutes of Health, the next generation vaccine will provide greater or equal protection, require fewer doses to produce immunity, and have fewer adverse effects than the current anthrax vaccine. The reduced number of doses would provide greater flexibility to military forces by reducing the time constraint for developing immunity, hence accelerating the time for fielding a protected force. The next generation vaccine is based on recombinant protective antigen (rPA), which binds to the lethal factor (LF) and edema factor (EF) of B. anthracis. The recombinant production technology would eliminate need for spore-forming anthrax, and hence the need for a dedicated production facility. Overall, the next generation anthrax vaccine would decrease production cost, allow a greater range of potential vaccine production facilities, and potentially allow for streamlining of the regulatory approval process. Another example of a product being developed within the MBDRP is Multiagent Vaccines (MAV) for Biological Warfare (BW) Threat Agents. The MAV project is a proof-of-principle effort to construct a vaccine or vaccine delivery approach that could concurrently immunize an individual against a range of BW threats. Bioengineered and recombinant vaccine technologies will be exploited to achieve vaccines that are directed against multiple agents, yet use the same basic construct for all of the agents. The MAV would be analogous to commercial vaccines (e.g., measles-mumps-rubella) but would exploit new approaches—naked DNA vaccines and replicon vaccines. The MAV would result in a reduced number of doses and thus provide greater flexibility to military forces by reducing the time constraint for developing immunity, hence acceler-
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary ating the time for fielding a protected force. The MAV also could decrease production cost, allow for greater range of potential vaccine production facilities, and potentially allow for streamlining of the regulatory approval process. Current Biological Defense Vaccine Capabilities Joint Vaccine Acquisition Program (JVAP) In order to enable the transition of candidate biological defense vaccines developed under the MBDRP or from other sources, a Prime Systems Contract was awarded in November 1997 to DynPort Vaccine Production Corporation, LLC. The JVAP was established for the purpose of developing, testing, and Food and Drug Administration (FDA) licensure of vaccine candidates, and production and storage of vaccine stockpiles. A major objective of the program is to establish a viable industrial base for vaccine production. The next generation anthrax vaccine (rPA) is one of several vaccines being investigated for development by the JVAP. Other vaccines in advanced development include smallpox, pentavalent Botulinum Toxoid, and tularemia. The Prime Systems Contract also provides options for other biological defense vaccines. Currently, all vaccines in the JVAP are in the development phase. Anthrax Vaccine Adsorbed (AVA) and the Anthrax Vaccine Immunization Program (AVIP) The only vaccine currently licensed for use in the United States to protect against anthrax is AVA. AVA is cell-free filtrate, produced by an avirulent strain of Bacillus anthracis. It is manufactured by BioPort Corporation in Lansing, Michigan and procured under a separate contract. It was licensed by the FDA in 1970. Six doses of the vaccine are required for full immunity, including doses at 0, 2, and 4 weeks, 6, 12, and 18 months, followed by an annual booster. On December 15, 1997, the Secretary of Defense approved the decision to vaccinate all of the U.S. armed forces against anthrax, contingent on the successful completion of four conditions, which were met: supplemental testing of the vaccine; tracking of immunizations; approved operational and communications plans; and review of health and medical aspects of the program by an independent expert. Implementation is determined in accordance with DoD Directive 6205.3, “DoD Immunization Program for Biological Warfare Defense,” November 26, 1993, with complete implementation of the plan contingent upon adequate supply of the licensed vaccine. On May 28, 1998, the Secretary of Defense directed vaccination of the total force. Implementation of this directive was administered by the AVIP. As of May 29, 2001, more than two million doses were administered to more than 500,000 military personnel, with at least 70,000 completing the full six-shot
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary regimen. Since then, there has been only a few who have received vaccinations. As outlined in a June 8, 2001 memorandum, the Secretary of the Army ordered a slowdown in immunization to accommodate delays in release of vaccine pending FDA approval. Implementation of the vaccination continues to designated special mission units, to vaccine manufacturing and DoD personnel conducting anthrax research, and others conducting Congressionally mandated anthrax vaccine research. Detailed information on the status of the AVIP is available at www.anthrax.osd.mil. What Does Producing a Vaccine Mean? With no vaccines currently in production under the JVAP and AVA as the only currently available FDA licensed vaccine for protection against BW threats, DoD is evaluating other mechanisms to increase and sustain vaccine production. In order to identify the status of vaccines, it is important to understand the major phases of research, development, and production through which they must proceed. Within different phases of vaccine development and production, there will be varying levels of production risk and overall risk. There are three major phases in the development and production of new vaccines—science and technology base, development and licensure, and licensed production. Following is a summary comparing different activities within each phase. Production Approach Within the science and technology phase, production is focused on small quantities and relies on bench top methods, which may include many different approaches, including new state-of-the-art experimental approaches. When a candidate product transitions to the next phase, a best approach is selected (or in some cases two or three promising approaches) and tested for scale up for full scale production. Following licensure, production proceeds at full scale and relies on a single, fixed method. Changes in the method typically require further testing and require approval by the FDA. Vaccine Recipients Perhaps the most obvious difference among the phases are the numbers and types of vaccine recipients and the purposes for which they receive the vaccine. Within the science and technology phase, recipients are primarily laboratory animals and include hundreds of animals. The primary purpose for using these recipients is to demonstrate the potential effectiveness of a vaccine candidate, that is proof-of-principle testing. During the development and licensure phase, vaccine recipients are humans, who participate in clinical trials. All recipients are volunteers, who participate in clinical trials that comply with FDA regula-
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary tions. The focus of these investigations is to determine the safety and efficacy of a vaccine as well as to optimize dosing and scheduling. The final phase is production and includes providing a licensed vaccine to all individuals who may be at risk, in accordance with the FDA license and based on quantities available, for the purpose of providing protection against potential threats. The effected populations could be on the order of millions of individuals. Production Risk Production risk during the science and technology phase is moderate since only small quantities can be produced yet only small quantities are needed. Risk is minimized since FDA approval of the product is not required. During the development and licensure phase, production risk is usually high because of the risks involved in scaling up pilot lot product to full scale production. Overall risk is also high because of reliance on and surrogate models or biomarkers to determine efficacy, since law prohibits exposure of humans to chemical or biological agents. Overall Risk Overall risk for production of biological defense vaccines will vary depending on the type of vaccine being produced and the policy implemented for immunization. For example, use of a live vaccine (e.g., vaccinia live vaccine) poses risk that inoculated individual may be giving off live vaccinia viruses until scarification has occurred (2–5 days), hence potentially exposing unprotected individuals. Another risk is that low rates of adverse effects may become more apparent in a large scale immunization program than had occurred during testing. For example, if 1,000 people are tested in clinical trials and only one had a serious adverse reaction, there may be hundreds of reactions if the total military force is vaccinated. Biological Defense Vaccine Development and Production Issues One of the major factors limiting the availability of biological defense vaccines is the limited interest from the pharmaceutical industry in supporting the production of these vaccines. In contrast to vaccines to support public health needs (e.g., childhood diseases, influenza), most vaccine needs are fulfilled by the private sector. However, the private sector has some challenges in fulfilling public health vaccine needs. The vaccine production industrial base is nearly at full capacity to meet public health priorities. This will pose a challenge for the production of biological defense vaccines if production of biological defense vaccines results in the deferral of production of public health vaccines. Biologi-
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary into the viral membrane (Volchkov et al., 1995; Sanchez et al., 1996). The secreted form was originally believed to serve as an immunological decoy for the full-length glycoprotein, allowing the full-length glycoprotein to attach to the target cell. However, more recent evidence now suggests that this hypothesis is unlikely. Instead, the secreted form appears to inhibit early steps in neutrophil activation and thereby inhibit the host inflammatory response to the virus (Yang et al., 1998). The secreted glycoproteins have been shown to bind quite well to neutrophils, but bind poorly to endothelial cells (Yang et al., 1998). In contrast, the full-length glycoprotein interacts with endothelial cells but binds poorly to neutrophils (Yang et al., 1998). This glycoprotein enables the Ebola virus to recognize and introduce its viral contents into the endothelial cell lining of the blood vessels, as well as monocytes/macrophages, thereby resulting in the cellular damage that is associated with the devastating symptoms of Ebola infection. Antiviral Targets Detailed analyses of the mechanisms of viral entry, replication, and cell damage have identified the Ebola glycoprotein 2 (GP2) as a potential antiviral target. In particular, there is a region in the GP2 ectodomain of Ebola virus that forms a coiled coil, or hairpin-like structure similar to what exists in the human immunodeficiency virus (HIV), influenza, respiratory syncytial virus, and a variety of other viruses (Weissenhorn et al., 1998a, 1998b; Malashkevich et al., 1999). This coiled-coil region contributes to membrane fusion by undergoing conformational changes after the glycoprotein binds to the membrane receptor (Weissenhorn et al., 1998b; Watanabe et al., 2000). The fact that this structure is conserved in a number of different viruses suggests that it may represent a potential target for antiviral therapy. In fact, a peptide product directed at the analogous structure in HIV has potent antiviral effects and is currently being developed for the clinical treatment of AIDS. This or similar peptides could be useful against many other viruses as well, including Ebola. Not only does the transmembrane glycoprotein direct the Ebola virus into specific cells, but the glycoprotein itself is also highly toxic to cells. For example, when full-length Ebola glycoprotein is overexpressed in cultured renal epithelial cells, it inserts into the membrane and causes morphological changes and detachment from culture dishes (Yang et al., 2000). This finding suggests that there is a genetic determinant in the glycoprotein that mediates its toxicity and, therefore, might represent another potential target for antiviral therapies. Mapping studies identified a serine-threonine-rich, mucin-like core domain region of the glycoprotein that is required for cytotoxicity in human endothelial cells (Yang et al., 2000). When the mucin-like region of the glycoprotein was deleted, its cytotoxicity was abolished, but protein expression and function remained unchanged (Yang et al., 2000). Every possible open reading frame in the Ebola virus genome has been tested for toxicity, except for the polymerase re-
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary gion. To date, only the glycoprotein has been shown to induce toxic cytopathic changes. However, a better understanding of the detailed molecular mechanism of virus assembly may eventually provide insight into other potential antiviral targets as well. Vaccine Development Not only does the glycoprotein play an important role in toxicity, increasing evidence suggests that it also plays an important role in the pathogenesis of Ebola infection. Infection of cultured cells with adenoviral vectors encoding the glycoprotein causes considerable cellular damage that correlates with toxicity. However, overexpression of a glycoprotein that is unable to insert into the cell membrane is not cytotoxic. In fact, injecting adenoviral vectors, or DNA forms of these vectors, into mice, rabbits, and primates actually protects the animals from disease by inducing an effective vaccine response. No human vaccine against Ebola is currently available. However, studies in animals suggest that DNA vaccines, together with replication-defective adenoviral vectors, may be particularly promising. In the DNA vaccination platform, a plasmid expression vector is injected into muscle, thereby enabling muscle to synthesize large quantities of proteins that stimulate the immune system to generate an effective immune response. DNA vaccination technology could greatly simplify the vaccination production process that would otherwise rely on very large-scale plants for making these complex and highly purified proteins. However, although current DNA vaccines work well in rodents, they are not as effective in non-human primates and are even less robust in humans. Thus, one of the important challenges for developing an effective DNA vaccination platform technology is to improve immune responses in non-human primates and humans. The first successful studies of a DNA vaccine for Ebola virus were carried out in guinea pigs (Xu et al., 1999). Animals that were immunized with sufficient levels of Ebola virus glycoprotein to induce a high-titer antibody response survived infection. Guinea pigs with intermediate levels of titers exhibited an intermediate chance of survival. In contrast, none of the control animals, immunized with vector alone, survived Ebola infection (Xu et al., 1999). “Primeboost” strategies combine DNA immunization and boosting with adenoviral vectors that encode viral proteins to specifically target dendritic cells. Such DNA vector-viral vector combinations can be very potent. Animals are first immunized with a DNA vector, and typically develop titers ranging from 1:1,500 to about 1:3,500. Following the adenovirus boost, antibody titers increase dramatically, ranging from 1:50,000 to 1:100,000. This far exceeds the minimum threshold that is considered to be necessary for an effective immune response in primates. A modified prime-boost strategy was recently used to immunize cynomolgus macaques against several strains of the Ebola glycoprotein (Sullivan et al., 2000). Several months later, animals were boosted with recombinant ade-
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary novirus expressing the Ebola (Zaire) glycoprotein. Control animals received empty vectors consisting of plasmid DNA and ADV-DE1 recombinant adenovirus in a parallel injection regimen. When animals were subsequently challenged with a lethal dose of the Zaire subtype of Ebola virus, all control animals (6 out of 6) exhibited rapid increases in their viral antigen levels and succumbed to infection within seven days. In striking contrast, all animals immunized with the combination DNA-adenovirus vaccine survived Ebola virus challenge (4 out of 4). The level of antibody production and the cellular proliferative response were closely correlated with immunoprotection. It is of interest to note that vaccines are not only clinically useful, but they can also serve an important function as deterrents against bioweapons. It is much more difficult to engineer vaccine resistance than drug resistance in an organism. Having well-defined, publicly known, and effective vaccines is a critical preventive, or deterrent, strategy. Another benefit of a successful vaccine is that it opens the way for developing novel immunotherapies. In the case of Ebola virus, for example, hyperimmune serum from animals that are protected from the disease is currently being examined, to determine if it can be used during the course of infection as a possible post-exposure therapy. Role of Genomics in Vaccine Development and Biodefense Genomic approaches hold enormous potential for vaccine development, and these possibilities are only just beginning to be explored. For example: Analysis of global gene expression patterns can facilitate the early identification of both environmental and disease-associated pathogens. Gene expression patterns can be used to identify specific genetic susceptibility and resistance markers. Biomarkers for vaccine efficacy could be incorporated into the experimental design of efficacy trials, which could then accelerate approval and licensure processes. High throughput technology can be used to improve vaccine design, by allowing researchers to readily monitor how specific structural changes in the vaccine affect the cellular response to immunization. It is possible that enough information will eventually be available and implemented within the technology that simply knowing the sequence of a particular open reading frame will be sufficient to understand how to generate an effective vaccine. Such technology would be useful not only as a defense measure against bioterrorism, but also for the prevention or treatment of naturally occurring outbreaks, such as influenza. The influenza virus constantly mutates, but if genetic information could be acquired quickly enough, it may become possible to develop more effective countermeasures.
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary In conclusion, the process of vaccine development must evolve to become more responsive to the changing needs and emerging outbreaks of society today. In other words, more agile vaccines are needed. Agility includes the ability to rapidly deploy vaccines in the event of an outbreak; to accelerate immunization regimens so that such an outbreak could be effectively managed; and, finally, new technology must be applied to develop better vaccines and to accelerate the development process. MEETING THE REGULATORY AND PRODUCT DEVELOPMENT CHALLENGES FOR VACCINES AND OTHER BIOLOGICS TO ADDRESS TERRORISM Jesse L. Goodman,* M.D., M.P.H. Deputy Director, Center for Biologics Evaluation and Research, Food and Drug Administration The FDA plays an important role in multiple stages of the product development process, from initial clinical studies through licensure, manufacturing and post-marketing studies which may be used to further evaluate safety and effectiveness. For these reasons, FDA is committed to working together with the scientific and clinical communities and with industry and the public to fulfill its regulatory and public health role in facilitating the development of biodefense biologics and therapeutics. Recent and ongoing FDA biodefense-related activities include, for example, meeting with sponsors and sister agencies and departments to encourage interest in developing safe and effective new products needed for public health biodefense, performing research that ultimately facilitates the development of these products; and providing intensive and early interactions with product sponsors to speed their availability. As with any medical product, bioterrorism products need to be regulated to ensure consistent and objective protection of the public safety. While there is currently a sense of emergency and a set of urgent needs to address, the desire for rapid and innovative responses must not be allowed to compromise the objective assessment of safety and effectiveness. Thus we need a regulatory agency that can step back and provide a more objective perspective. If and when things go wrong in the wake of decision(s) made in a time of crisis, few people will remember the crisis and that the decision was in fact made with the best intentions. The public expects safe and effective products, and safety expectations are especially high for vaccines administered to healthy individuals. Maintaining public confidence in vaccines and medical products, in general, is critical to maintaining overall confidence in our nation’s public health programs and leadership in matters extending far beyond bioterrorism. For these reasons, * This statement reflects the professional view of the author and should not be construed as an official position of the Food and Drug Administration.
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary even in difficult times, we must continue to make and communicate clearly the best possible scientific and public health decisions about product development, licensure, availability and use. Furthermore, bioterrorism is a moving target, not a single disease of predictable epidemiology, and all potential product uses may not be anticipated. This complicates many decisions about product use. For example, a vaccine, such as the licensed anthrax vaccine, which may have been originally studied and used in a limited population effectively and without major safety concerns may raise more significant public concerns about uncommon adverse events, whether coincidental or due to the vaccine, if and when it is administered for similar reasons to hundreds of thousands of people or when unanticipatedly used for post-exposure prophylaxis. There are several factors that account for why we do not have an adequate supply of vaccines for bioterrorism defense: Financial Disincentives Uncertain markets, especially for potentially more limited use products such as a tularemia or plague vaccine. Uncertain longevity of the needs, markets and of resources; short attention spans in government budgeting. The fact that vaccines are complex biological products that carry a high risk of uncertainty, unpredictability of success, and financial loss. The rigorous safety requirements and low public tolerance of risk—in part because they are often administered to healthy people as a preventative measure—and associated costs of developing biologics. The fact that preventive measures are generally undervalued, both perceptually and financially. Vaccines are often expected to be sold for very low prices, and the expected profit for the producer is therefore lower than for other products (e.g., drugs for treatment) competing for the same resources. However, while difficult to model when risks are unclear, it would be interesting to conduct more comprehensive and long-term cost-benefit analyses concerning the personal health impacts and the social and economic costs versus potential benefits of vaccine compared to treatment strategies for specific agents of interest. The added cost of the large clinical trials needed to address potential wide use including in diverse populations. The presence of advocacy groups with various points of view. A fair amount of concern about possible adverse effects of vaccines, ranging from specific disease issues to more general anti-vaccine sentiment on the part of a proportion of the public. A mistrust of government and industry. Product liability issues.
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary Scientific Challenges Lack of historical or recent precedents for vaccines against many pathogens, which makes it difficult to establish good surrogates. The potential for genetic or other manipulation of antigenic determinants. (Although this is presently more difficult in many cases to engineer than antibacterial resistance.) The potential complications of live vaccine administration to increasing immunocompromised populations. The intense flow of resources demanded by urgent perceived needs (sometimes referred to as the “disease du jour” phenomenon), in contrast to the more normal lengthy product development cycle. The FDA Response There are several regulatory approaches and mechanisms that the FDA has employed in an attempt to safely speed up product availability and licensure: Early and frequent consultation between the sponsor producing the product, the potential end users (e.g., health officials and providers in the military and civilian sectors), and the FDA is very resource-intensive but important. This kind of up-front investment can greatly improve the product development process by identifying creative study designs, recognizing factors that are normally not anticipated in developing a product, and reducing misunderstandings and the likelihood of unwelcome surprises. Early dialogue also increases accountability. Emergency use under IND (investigational new drug status) allows rapid access to products that have not yet completed requirements for licensure. INDs require acceptable evidence of safety; a reasonable though not necessarily formally proven scientific basis for efficacy; a favorable risk:benefit ratio; and an intent to license. While allowing availability of potentially lifesaving products, a disadvantage to emergency use under this rule is that the product is not licensed, which not only reflects the true scientific limitations of the data but also raises important issues about public perception. Fast track processes can speed up the review process for products that will provide meaningful therapeutic benefits compared to existing therapies for serious or life-threatening illnesses. Fast track allows the FDA to review information as it becomes available and as the sponsor submits it. Accelerated approval through the use of surrogate end points to demonstrate benefit. The use of CD4 cells for assessment of antiviral treatment of HIV was one of the first surrogates to be approved under this rule. For bioterrorist agents, protective antibody levels for a vaccine or immunoglobulin could serve as potential surrogate end points. Clinical end points can also be utilized. There still must be good post-licensure studies to demonstrate the effects on disease outcomes and to collect additional safety information, and the FDA can place restrictions on use and promotion and even withdraw the product if agreements are violated or the product proves unsafe or ineffective. Thus far, this process has worked fairly well
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary although, once a product is licensed, or if a disease is rare, it may be difficult to obtain patients for studies, and sponsors sometimes are unable or unmotivated to fulfill their commitments. But because most accelerated approval products also receive priority review, this process can allow for rapid approval of a product based on more limited and simpler-to-obtain clinical data than may be the case with large, randomized control trials and/or longer-term endpoints. Priority review is applied when a product is considered a significant advance or will be used for serious or life-threatening illness. Approval under the forthcoming “Animal Rule” has very important biodefense implications. In fact, the rule is specifically oriented to drugs or biologics that reduce or prevent serious or life threatening conditions caused by exposure to lethal or disabling toxic, chemical, biologic, or nuclear threats. The products should be expected to provide a meaningful therapeutic benefit over existing treatments. Human efficacy trials should either be not feasible or unethical, and the use of the animal efficacy data should be scientifically appropriate. In this proposed rule, the end point should be related to the desired benefit in humans, usually a significant outcome such as mortality or major morbidity. Clinical studies in representative populations are still needed, however, both for establishing pharmacokinetics (including, in the case of many vaccines, immunogenicity) and for assessing safety. Such studies are critical because civilian populations often include vulnerable or pharmacokinetically variable subsets. Finally, similar to the fast track and accelerated approvals, the animal rule has post-marketing and labeling commitments and restrictions. It does not apply if the product could be approved based on any other standard in FDA’s regulation. It is a rule of last resort, but it certainly would be applicable to many of the situations that have been described in this workshop. In addition to its regulatory responsibilities, the FDA’s Center for Biologics conducts a significant amount of biodefense-related research, supporting approximately sixty ongoing projects that are directly relevant to identified high threat agents. The general goal is to meet otherwise unmet research needs, often with regulatory implications. Examples include how to better determine potency; defining immune and other correlates of protection; how to make safer and purer products (including characterization of the safety of cell substrates and detection of adventitious agents); better assessment of adverse events and efficacy under conditions of use, and studies which allow the agency to make regulations more scientific and less “defensive.” These types of research can benefit not only the public, but also multiple companies across industry, but are often not performed by a given sponsor as they may not provide a direct and/or immediate benefit. Furthermore, through its research and related scientific interactions, the center maintains the type of cutting edge expertise that is increasingly needed for dealing intelligently and proactively with evolving products and their underlying biotechnology. This expertise and confidence fosters the science-
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary based objectivity necessary for anticipating and/or reacting appropriately to the issues raised during the development of a product which, ultimately, accelerates the regulatory and licensure process. By maintaining its scientific, objective regulatory stance, the FDA can increase confidence in the likely efficacy of products primarily approved based on surrogate/animal data and reduce the likelihood of serious adverse events. The FDA brings several other unique attributes to the product development process as well, including: Knowledge of scientific and industrial capabilities, which is very helpful when it is necessary to identify people with specific expertise. This includes knowledge of emerging technologies which are cross-cutting among diverse products that nobody else may have the opportunity to see; knowledge of manufacturing capabilities; and knowledge of potential new uses of both licensed and investigational products, for example anti-sepsis and immune modulators. Day-to-day participation in what it takes to develop a product, including clinical trials, quality assurance, adverse event monitoring, timelines, etc. A unique ability to match product needs to industrial and academic capabilities. Much of this is informal, but it can be very helpful in getting the job done well. However, there are several things that the FDA cannot do. FDA cannot provide monetary or tax incentives; assure that anyone will make a product; sponsor or directly assume the burden of product development, since this would be a conflict of interest; provide indemnification or compensation for injuries; Furthermore, while the prelicensure process can provide reasonable assurances about the degree of safety and effectiveness, FDA cannot guarantee absolute safety; guarantee human efficacy under field conditions based on non-human data such as animal studies or surrogate endpoints (or, for that matter, based on efficacy observed in the controlled setting of a clinical trial). In addition to expedited regulatory pathways, as well as orphan drug status, there are several potential incentives—both push and pull—which are outside the mission of FDA but that could be evaluated with respect to their potential to stimulate product development. Push incentives, which could be considered where markets are small or uncertain, could include: direct financial awards or contracts; tax credits; enhanced exclusivity; partnerships in product development; and
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary research and development assistance to reduce the financial sting and risk of product development. Possible pull incentives, which are probably more valuable, include: known markets; longer term financial contracts; defining prices that more accurately reflect known and potential public health benefit, which will require more economic discussion and modeling; and where possible, developing dual or multiple use products/concepts which can used not just for meeting bioterrorism needs but also for enhancing general public health and medical care. In summary, FDA and CBER are highly committed to working with multiple partners in and outside of government to help in meeting the challenges posed by bioterrorism. Especially in times of threat and crisis, there is a need for a responsive, yet independent and science-based regulatory process. Relevant research and expertise remains critical in meeting the challenge. Existing laws and regulations can help facilitate product development in a timely manner. There are significant financial disincentives which have and may continue to impede the industrial development of some needed products where markets may be small or uncertain. Careful and open communication with the public about what is and is not known about proposed bioterrorism responses using new and existing products is critical not only in responding to specific threats and protecting the public but also in maintaining confidence in and support for the public health system as a whole. MOVING THE VACCINE AGENDA FORWARD: OBSTACLES AND OPPORTUNITIES Stanley Plotkin, M.D. Medical and Scientific Consultant Aventis Pasteur, Inc. The vaccine industry is highly concentrated with only four major manufacturers providing more than three quarters of the market. Even within these four main manufacturers production capacity may be insufficient for unseen circumstances or urgent need, as has been demonstrated by shortages of DT Acellular pertussis vaccine and pneumococcal conjugate vaccine. Following September 11th, all four major manufacturers expressed interest in biodefense/military vaccines. But how long will patriotism sustain this interest? The industry is both high risk (e.g., the rotavirus vaccine which had to be withdrawn from use) and risk adverse (e.g., certain vaccines for pregnant women have yet to be developed). There are several factors that impede vaccine product development:
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary The vaccine industry is market-driven, and the major manufacturers are simply not interested if the market is insufficient. The industry is highly regulated, and perceived regulatory hurdles can impede product development. Intellectual property conflicts can prevent companies from developing products. Negative marketing assessment impedes vaccine production. Marketing departments often make unchecked predictions. An uncertain or dubious proof of concept creates reluctance to develop a particular new product. Biohazard to personnel, especially with regards to biodefense vaccines, can create reluctance. The production of an adequate biodefense vaccine supply will depend on many factors: Development of biodefense vaccines must be in collaboration with DoD, NIH, CDC, and other agencies with national interests. With regard to the development of a new smallpox vaccine, for example, efficacy is an important issue that requires the use of monkey models for which the vaccine industry must turn to DoD or NIH. Development of biodefense vaccines requires better adverse reaction surveillance. With the military anthrax vaccine, for example, initially there were no data to support the claim that the vaccine was indeed safe. New vaccines must have built-in surveillance in order to discredit unsubstantiated claims about adverse reactions based on anecdotal data. New vaccine production requires that liability indemnification be guaranteed. One possible solution would be to place these vaccines on a list of compensable vaccines. We need to create a no-fault system which indemnifies companies against non-negligent harm but also provides some relief for injured individuals. Access to new technology would likely stimulate more interest in vaccine development. For example, a number of companies have pursued DNA vaccines because they are an interesting new technology which could likely be applied to a number of different targets. After all, the main role of the vaccine industry is not to conduct basic research but apply basic research to the development of new products. Finally, vaccine production priorities need to be set and somebody authorized to say “this is the top priority.” For example, Gary Nabel has presented some very elegant work on an Ebola vaccine. But what does intelligence say is the real risk of Ebola? Should a virus that cannot be spread as an aerosol be considered a priority?
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Biological Threats and Terrorism: Assessing the Science and Response Capabilities - Workshop Summary In summary, the major vaccine manufacturers will not be able to provide all of the needed biodefense vaccines. However, they should be asked to play a significant role. That role will be facilitated by clear directions, clear priority setting, and a tight collaboration between industry and government in order to move animal and clinical testing forward. REFERENCES A. Johnson-Winegar: Grabenstein, J.D., and Wilson, J.P. (1999), “Are Vaccines Safe? Risk Communication Applied to Vaccination,” Hospital Pharmacy, Vol.34, No. 6, pp. 713–729. Institute of Medicine. (1996), Interaction of Drugs, Biologics, and Chemicals in U.S. Military Forces. Washington, D.C.: National Academy Press. Morbidity and Mortality Weekly Report. (December 15, 2000), 49(RR15);1–20 “Use of Anthrax Vaccine in the United States—Recommendations of the Advisory Committee on Immunization Practices.” G. Nabel: Balter, M. 2000. Science 290: 923–925. Colebunders R, Borchert M. 2000. Journal of Infections. 40: 16–20. Malashkevich VN, Schneider BJ, McNally ML, Milhollen MA, Pang JX, Kim PS. 1999. Proceeding of the National Academy of Sciences, U S A 96:2662–2667. Peters CJ, Sanchez A, Rollin PE, Ksiazek TG, Murphy FA. 1996. In: Fields BN, Knipe DM, Howley PM, eds. Fields Virology 1161–1176 (Lippincott-Raven, Philadelphia). Peters CJ, Khan AS. 1999. In: Klenk, HD, ed. Current Topics in Microbiology and Immunology 235:85–95 (Springer-Verlag, Berlin). Sanchez A, Khan AS, Zaki SR, Nabel GJ, Ksiazek TG, Peters CJ. 1996a. In: Fields BN, Knipe DM, Howley PM, eds. Fields Virology 1279–1304 (Lippincott-Raven, Philadelphia). Sanchez A, Trappier SG, Mahy BWJ, Peters CJ, Nichol ST. 1996b. Proceedings of the National Academy of Sciences, USA 93: 3602–3607. Sullivan NJ, Sanchez A, Rollin PE, Yang ZY, Nabel GJ. 2000. Nature 408: 605–609. Volchkov VE, Becker S, Volchkova VA, Ternovoj VA, Kotov AN, Netesov SV, Klenk HD. 1995. Virology 214: 421–430. Watanabe S, Takada A, Watanabe T, Ito H, Kida H, Kawaoka Y. 2000. Journal of Virology. 74: 10194–10201. Weissenhorn W, Calder LJ, Wharton SA, Skehel JJ, Wiley DC. 1998a. Proceedings of the National Academy of Sciences, USA 95: 6032–6036. Weissenhorn W, Carfi A, Lee KH, Skehel JJ, Wiley DC. 1998b. Molecular Cell. 5: 605–616. Xu L, Sanchez A, Yang Z, Zaki SR, Nabel EG, Nichol ST, Nabel GJ. 1998. Nature Medicine 4: 37–42. Yang Z, Delgado R, Xu L, Todd RF, Nabel EG, Sanchez A, Nabel GJ. 1998. Science 279: 1034–1037. Yang ZY, Duckers HJ, Sullivan NJ, Sanchez A, Nabel EG, Nabel GJ. 2000. Nature Medicine. 6: 886–889.
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