Translation of Tissue Engineering Approach from Laboratory to Clinics

Daniel Chavarria-Bolanos,’■[1] José Vega-Baudrit,2 Bernardino Isaac Cerda-Cristerna? Amaury Pozos-Guillén2 and Mauricio Montero-Aguilar1

Introduction

Biotechnological advances in the dental and maxillofacial field have shown exponential growth in the last decade in terms of research funding and product development, resulting in novel more effective clinical applications. Now, more than ever, the industry is working with academia to produce new biomaterials allowing the possibility for techniques to either repair or regenerate biological tissues. The regeneration process is described as a slow replacement of a lost or damaged structure with the identical original tissue, a process observed naturally only during the first stages of life. On the other-hand, repairing tissue is a much faster process involving the inflammatory cell cascade, following the deposition of a matrix and remodeling of the tissues in the damaged site.

Tissue engineering makes it possible for a clinician to repair or regenerate an affected tissue using cells fixed to biological or synthetic matrices or scaffolds which will guide the growth of the new tissue (Oakes 2004). In the near future, clinicians will be able to replace or regenerate completely lost or damaged oral structures with some kind of engineered product coming from a laboratory. Currently, scientific research is focusing on expanding our knowledge regarding the biological processes involved in tissue regeneration and repainnent. This new knowledge has the potential to be translated clinically in more biological approaches for the final benefit of patients (Simon et al. 2011). Unfortunately, the commercially available products represent a small proportion of what has been tested and developed in the laboratory. The elevated costs and the complex regulatory pathway are responsible for the disparity between the amount of research investment and the number of products available in the market (Mishra et al. 2016).

New inventions and advances in tissue engineering commonly raise the same question among clinicians... WHEN? When will it be available in the market? And when can it be used in our clinical practice? It seems that other questions such as, how does it work? Who could benefit from it? And what adverse effects can we expect, play a secondary role. For researchers, it is impossible to predict when a new material or method will be available in the market, since the road from the laboratory to the final consumer is regularly a long way, full of complex challenges which not always depend on the research team’s efforts or capacity. Zafar et al., discuss some of the challenges in the process of translating tissue engineering research from the laboratory to the clinic. These challenges could be classified into two main groups: scientific and non-scientific challenges. Among the scientific challenges, they highlight the need for a multidisciplinary approach as one of the major concerns. Also, the complex nature of the oral tissues, the lack of an ideal scaffold material, and sterilization protocols are some of the challenges scientists and research groups must deal with in order to advance in bringing new therapeutic options to the clinic. On the other hand, regulatory and ethical issues regarding the use of some of the basic elements needed in tissue engineering like stem cells, funding opportunities, cost-effectiveness analysis, and the ideal packing and storage of these tissues are listed as the non-scientific challenges (Zafar et al. 2015). Most of the answers for overcoming these challenges are still to be discovered, others need a change in the perception of scientific progr ess from authorities and regulatory' agencies. Now more than ever, the industry and academia need to work together, and scarce resources need to be used effectively.

Clinical Setting

Let us consider a likely real-life clinical situation. After cancer surgery, a patient loses a segment of the mandible and now needs the replacement of the lost bone structure. The tr eating clinician could opt for one of the available cun ent options which include a standard titanium prosthesis or an autologous bone graft from a different donor site, for example. Also, he may figure out a new therapeutic option, not yet properly tested or developed, which may bring more clinical benefits and fewer costs. After reading a press article, he thinks of a novel idea, a hypothetical 3D printable scaffold made of shr imp crust residues, which is also functionalized with an analgesic molecule to theoretically improve the postoperative application. As a clinician, the fundamental question still remains, how much time and effort would it take to turn this concept into an available commercial product ready to use? Figures 2.1 and 2.2 will lead us in exploring the pathway for how to turn this concept into an available product.

The Rise of New Ideas—The Key to the Laboratory

Tissue engineering has been defined as “an interdisciplinary field which applies the principles of engineering and life sciences toward the development of biological substitutes that restore, maintain or improve tissue function” (Langer and Vacanti 1993). This definition is valid to describe the concept of oral and craniofacial tissue engineering with a focus on dental and maxillofacial structures. As an interdisciplinary research field, this involves many scientific areas such as biology, mathematics, physics, chemistry, mechanics and informatics, among others. Hence, the final product is the result of the combined knowledge of these areas. In an attempt to simplify it, tissue engineering is a system mainly composed by a scaffold, cells and active molecules; consequently, every compound and also the combined compounds should be evaluated with in vitro and in vivo tests. The translation from the bench to the clinic consequently implies a hard-scientific work as well as an ethical challenge.

Translational resear ch refers to all the steps needed for bringing the concept of an idea to advanced preclinical and clinical testing and, ultimately, to the development of new therapies for patients (Chen et al. 2012; Ungerleider and Christman 2014). As it can be exemplified (Fig. 2.1a), every new invention rises from a clinical need, and depending on the context, this clinical need can have different

Schematic representation of the initial steps for the concept development process

Figure 2.1. Schematic representation of the initial steps for the concept development process.

Translational flowgraph of the concept development process

Figure 2.2. Translational flowgraph of the concept development process.

origins. In most cases, the main source of a clinical need is the patient itself who presents a certain disease or condition. Usually if there is an effective treatment available, the clinician will tr eat the patient with the existing approach; but, if this treatment is not ideal or could be enhanced, then the clinician should look for an alternative treatment. Some of the available ‘novel’ therapies may not fit every single case or may lack enough evidence to assure a safe and effective outcome. In such cases, the clinician may finally consider, once again, the traditional strategy. Of course, this will drag the limitations or side-effects already tarown, and the clinical need may still be unsatisfactory.

After recognizing the need for a new material, the clinician will play a key role in the tr anslational process, which is to search in the market for available options; subsequently, they will turn to industry' when they realize the material is not available (Fig. 2.1b). Let us consider again our example, the new 3D printable scaffold, which from now on we will call 3D-SCAFF! The heating clinician will search the literature and look in the market for a scaffold with analgesic purposes that also acts better than the available treatment options, just to find out that none exists yet. Tire market offers several kinds of bone gr afts, but these are not ideal for this case. Then the market will ask the companies and industry if this product exists, with no positive response.

At this point, we can recognize a defining moment where the translational process could be interrupted. When the idea is presented to a pharmaceutical or medical business incubator or a startup company, the amount of resources the company invests in research and development (R&D) of new medical products and its experience in the regrrlatory process, is crucial (Bergek and Nonina 2008). For instance, a local or artisanal company might consider the idea interesting, but no further-steps are taken since they do not have the capacity to develop the prodtrct. Nonetheless, if the company has an advanced program for R&D and usually invests money in testing new ideas, it could identify an emerging market and the possibility to create a new product that will strengthen its position in the market is conceivable. These kind of companies will make a deep analysis of the development opportunity, and if the project is considered profitable, then the translational process will continue, looking for either private or public sponsors to materialize the new idea. This is finally the key for the laboratory.

Activation of Scientific Resources—Where the Industry and the Academy Meet

The unavailable material has now spun from a problem to a proposal. The company in charge of the development process will shape the concept into a formal business-oriented document. At this point, hermeticism and confidentiality are mandatory; and conflict of interests should be analyzed. The patient’s welfare should always be prioritized and kept in mind as the driving force during this translational process. Other interests, such as financial benefits and professional prestige should be considered as secondary endpoints when taking a new product from the laboratory to the clinic (Bekelman et al. 2003). Now, the idea can be a mere intention of gaining the intellectual property of the invention, or in turn, it can be worth millions of dollars if the product is finally developed. Secrecy and strict bioethical conducts between the different stakeholders are crucial when searching for the required scientific resotuces (Fig. 2.1c).

Biomaterial researchers need to provide meaningful endpoints to start the translation process (Tracey 2014). thus developing the idea should be scientifically and conceptually sound enough to gain the trust of potential investors. The prospect to create a new product will depend on two key issues: financial and academic support. Even when a big company may cover both factors, usually the amount of human and economic resotuces needed can make the project unfeasible. Hence, the creation of interdisciplinary collaborations is decisive and should involve private and public contributors.

Public resources include the participation of the universities or academic public groups (such as government research facilities), which may be in charge of the experiments to develop the prototype of the desirable product (Fig. 2.1c). These institutions usually require the option of research grants to cover the expenses of the research, and most of these arrangements may require confidentiality agreements between the parties. In some cases, the academic groups themselves may play a leading role, creating an inner industry that will benefit the universities’ budget. This kind of participation is usually known as "spin-off companies ”. Spin-off refers to how a company is created from another pre existing entity. In this case, entrepreneurial universities may play a key role in the economic and social development of a country (Miranda et al. 2018).

The private sector may contribute to the process as active developers financing the first experimental stages or only as mere suppliers of scientific resources. When time is vital and an unavailable advanced byproduct is needed, skilled suppliers are essential to minimize costs and time.

By reaching out for these suppliers with specific technology and advanced manufacturing processes, the developers could access the required piece of the puzzle, avoiding side-developing investments (Martinelli-Lopes et al. 2015).

The 3D SCAFF is a good example to show this process. Once the industry identifies the need for this new scaffold, they may look at different scientific databases for a competent academic or research group, who will satisfy this demand. This group could offer not only the equipment and technology but also the needed experience to guar antee an optimum beginning of the research process. If the developer recognizes that the project is too expensive to be covered by the company, the option of a public/private grant, to share the intellectual property with a sponsor or to activate a university spin-off company could be a good idea. Also, if the analgesic drug needed to load the 3D-SCAFF or a source of purified shrimp crust is needed, an outsourcer should be contacted to speed up the process. Once all the pieces are placed in order, the development process may begin (Fig. 2. Id).

Getting into the Laboratory

The concept development is ready to activate the laboratory protocols (Fig. 2.2a). This step, far from being a recipe to follow, is a complex multidisciplinary collaboration that will change depending on the desired product. For instance, some biomaterials for tissue engineering will require more mechanical than chemical evaluation, while others will need a deeper analysis of then biological behavior. However, one step camiot suppress the other, and a complete understanding of every factor is needed: from a frill physicochemical characterization (Fig. 2.2a. 1), to a dynamic mechanical evaluation (Fig. 2.2a.2) and a biological guarantee of safety for further in vivo experiments (Fig. 2.2a.3). It is advisable for the research team to consult different international standards (such as ISO protocols) to assure that every step is sound and accepted by others.

Since all the experiments needed vary from one product to another, let us discuss the possible steps to develop 3D-SCAFF. First, all the single materials to be used must be characterized individually, determining theh chemical composition, purity and behavior under different conditions (such as temperature changes, variable pH, pressure modifications or light exposure). Understanding each material will predict how they will behave once combined and may help to select and adapt the fabrication method. 3d printing—as an example—sometimes requires modifying the polymer temperature or the printing pattern; especially when an active molecule is added to the polymer. Once a possible combination is obtained, several mechanical tests will determine how the biomaterial will behave in the body and will predict the maximum load of force or deformation that may suffer. Different chemical analysis will also analyze the stability of the combmations, and the integrity of the added active molecules, such as drugs. Some vulnerable molecules may become inactive after preparation processes, so controlled release assays and bioactivity research must be conducted to determine if the loaded drug is still present.

Once some samples are obtained, the best laboratory options will be selected for biological tests to determine its biocompatibility (Fig. 2.2a.3). Biocompatibility states that the material must be non-toxic, non-allergenic, non-carcinogenic and non-mutagenic; and that it does not influence the fertility of the patient (Rogero et al. 2003). Specific experiments will determine the cellular response over the new product, in order to predict further responses from a living organism. In this context, the degradation and the by-products generated should be determined and understood as well. Although the first attempts to evaluate cytotoxicity depends on animal models, cunent advances hi cell culture techniques have allowed the use of faster and standardized analyses to detennine specific cell responses such as proliferation, adhesion, metabolism changes and differentiation, among others (Hanks et al. 1996). The obtained biological information; along with the mechanical and physicochemical data will lead to obtaining an accepted prototype: a theoretical ideal candidate (Fig. 2.2c).

Even when laboratory research is evolving, in vitro testing is essential to safely investigate the biological performance of newly developed devices when implanted in a living system. The annual model chosen should achieve the expected answers and should try to mimic the human response (Costa-Pinto et al. 2016). Unfortunately, a single animal model will only be used to evaluate a limited number of variables, and different tests and animal sources should be included to frilly understand the biological response (Fig. 2.2d). In order to minimize the number of annuals and tests required, the planning of each experiment must be meticulous, trying to obtain every possible data from each intervention. Life is valuable, and this does not exclude laboratory animals. Tire design of the study should consider the aim of each phase (i.e., evaluation of bone response, determination of inflammatory reaction and/or related pain and expression of biochemical mediators, among others) as well as specific biomaterial features (size, shape, degr adation time and byproducts) animal factors (species, age, sex, genetic background) and technical aspects (housing conditions surgical procedure, time of evaluation, sacrifice method) in order to guarantee a good experiment (Costa-Pinto et al. 2016; Pearce et al. 2007).

Contextualizing these steps to our 3D-SCAFF, specific experiments will include the characterization of both the natural polymer (including purity, stability, manipulation, physicochemical properties, etc.), and the analgesic drag. Compatibility between the materials and stability of the obtained product must be guaranteed before biological assays. Then, the cellular models will determine which of the prepared batches shows better behavior, and all data will then be translated into an annual model. In this case, an experiment to determine the bone reaction and replacement; and a second study to determine degradation and biocompatibility may be needed. However, as for in vitro biological assays, every experiment should have the corresponding bioethical authorization (Fig. 2.2b). It will be described that bioethical permission is not a license that allows a ‘free behavior’ m research. Single authorizations must be needed for every' single step that involves living organisms; from samples to animals and of course human beings.

Bioethical Issues—The Research Team Obligations

All the different parties involved dining the process of bringing an experimental product from the laboratory to the clinic, including academia, sponsors and pharmaceutical/medical industry, as well clinicians and the entire research group, all have great fundamental responsibilities and ethical obligations with the scientific community and with the potential final beneficiaries of the developed product. Good clinical practice principles must be considered dining every' step of the process and an independent ethics committee must review and approve each study or experiment conducted (Corley et al. 2016). In a simple definition, ethics is “the study of the nature and meaning of human activity”, and it is not an exclusive field for philosophers or ethicists. The ethical process of translating research, specifically in tissue engineering, is a daily challenge because humans and human/animal-derived products will be inherently used in these processes (Michman 1990). Bioethical concerns are present m basic or preclinical research stirdies, dining human clinical trials, in the adoption of best practices m the community, and in refinement of best practices in the community (Shapiro and Layde 2008).

Ethical behavior should start from the conception of the idea (Fig. 2.2b). No matter how the experimental product is conceptualized, all the ideas and perceptions around it should be understood from an ethical point of view. Available resources should be maximized, and human safety measures should always be prioritized along the process. An efficient translation process should be well planned and well designed to reduce failed processes in the early stages. To impact and contribute to the clinical stage, good translation planning should be considered from the laboratory (Kimmehnan and London 2015). For instance, the early stages of tissue engineering product development include the use of cells from human extracted teeth, stem cells from the apical papilla, human dental pulp cells and human umbilical vein endothelial cells, among others. These harvested cells from donated human tissues should be considered by scientists as an ethical issue, and the research protocol, even on basic research, has to be revised by an ethics committee. Usually, universities and research centers have an ethics committee within their organizations and independent/private research teams should submit then-protocols to an independent ethics committee. Especially in the clinical stage, it will be common that protocols include international research teams located in different locations or countries. These are called multi-center or multi-site trials, and an ethics committee should review and approve the protocol locally for every participating center. During the course of a multi-center trial, it is of utmost importance that data is constantly reviewed and any rising issue should be discussed by the research organizing team. Regularly, the research protocol may require many amendments during the study and each center should keep its local ethics committee with an updated protocol (Cerda-Cristema et al. 2014).

The use of animal models in research is sometimes controversial and discussions exploring the rights of animals and the responsibilities of scientists to annuals are imperative to understand and to achieve a rational decision for the use of these models (Baumans 2004). For some biomaterials, 3D cell models have been developed to substitute testing with animals; nonetheless, when experimenting in the preclinical stages of tissue engineering, in vivo models are mandatory since the regenerative process of tissue comprises intricate biological interactions that are difficult or sometimes impossible to reproduce in vitro. Hence, rats, mice, dogs and other in vivo animal models are common in oral and craniofacial tissue engineering studies (Zang et al. 2014; Shamma et al. 2017; Chien et al. 2018). To date, it seems impossible to move forward on translational research by only applying in vitro models or in silico models, bitt strict policies and ethical regulations limit unethical procedures on research of animals and great efforts are made to limit the unnecessary use of these models (Combrisson 2017). Since 1956. the concept of the 3R on animal research has impacted positively on animal welfare and also on the efficiency of translational research moving knowledge faster from the bench to clinics, giving more reproducible results and improving cost-effective results. These 3R conventional definitions have been recently discussed and analyzed, and contemporary approaches have been proposed: (i) replacement should be understood as the need to accelerate the development and use of tools relevant to the target species (usually humans) based on the latest technologies, (ii) reduction describes how protocols should aim to use appropriately designed and considerate animal experiments that are robust and reproducible, (iii) refinement finally stands for employing new in vivo technologies that can benefit both annual welfare and science, including methods to minimize pain and distress, as well as to deliver enhancements in annual care, housing, training and use (MacArthur 2018). The 3Rs have helped to create an international consensus on animal welfare, and have guided discussions to create international laws of the use of animals in experimental models. Although the legal requirements and practices for animal models in preclinical research usually vary between countries, currently a common fundamental rule is that scientists carrying out research involving the participation of animals must undergo special training in order to plan and conduct experiments on animal models. Thus, translational research in tissue engineering requires scientists to develop skills in management, development and data analysis of experiments with animals. Scientists trained in annual welfare should apply the 3R concepts and understand the ethical implications to then-laboratories (Franco et al. 2018).

During the entire translational process of developing an experimental product in oral and craniofacial tissue engineering, the stage where most ethical concerns arise is definitely during the clinical trial’s I-IV phases (Fig. 2.2e), where human testing of the product is conducted. Tire ethical regulation for clinical research must be understood as a dynamic evolving regulation, since this a more recent concept as compared to drug/device developing, for example. The regulatory agencies responsible for supervision and evaluation of new drugs and medical/dental devices, the US Food and Drug Administration (FDA) and the European Medicines Agency (EMA), have created guidelines on ethical conduct, in an effort to allow a faster arrival of novel tissue engineering products into the market. Tire ethical issues for clinical studies are many because a tissue engineering product is a combmation of human, animal and/or synthetic subproducts (scaffold, cells and active molecules), which will be used as part of clinical treatment in human beings. Before the experimental product could be tested clinically, its safety and efficacy must be demonstrated satisfactorily on in vitro and in vivo studies (Lu et al. 2015). According to Li et al., independent of the socio-cultural context where the study is taking place when writing and/or reviewing the ethics section of a clinical research protocol, 11 essential elements should be addressed and discussed to consider all possible aspects involved during the study. These elements are (1) addressing a relevant question. (2) choice of control and standard of care, (3) choice of study design, (4) choice of subject population, (5) potential benefits and harms, (6) informed consent, (7) community engagement, (8) return of research results and incidental findings, (9) post-trial access, (10) payment for participation, and (11) study-related injury (Li et al. 2016). If these elements are adequately discussed hi the research protocol, the approval of the document could be achieved faster and more efficiently.

Researchers and drug developers should be aware and consider the complexity of an experimental product and which regulations oversee its clinical evaluation, before starting the clinical stages. Each country has its own regulations and laws for approving the use of specific drugs, active molecules and autologous or xenogenous cells employed in the resear ch ofmedical/dental biomaterials. Moreover, the legislation for tr eating patients with tissue engineering products is not the same between countries and cultures (Chen et al. 2013). It is widely recommended that all the parties involved in the development of experimental products in tissue engineering be locally guided in the corresponding ethical and legal regulation for conducting research of such products.

From the First Prototype to Pre-Clinical Data

Going back to the 3D-SCAFF example, to evaluate the preclinical behavior of this experimental product, two bioethical concerns must be considered. First, obtaining cell lines and biological tissues (such as hitman blood for coagulation assays) where the biocompatibility and cytotoxicity will be tested. All human tissue samples (even when they are as tiny as a cluster of cells from disposable tissue like human pulp from extracted teeth) must be acquired following informed consent from the donor, and the final manipulation of these samples after each assay must assure no biological hazard to the researchers and the environment. Tire second concern is related to the evaluation itself. Tire acquiring, manipulation and sacrifice of animals involved in biological tests should be considered. Some of the tests can be expected innocuous or less harmful for the animals, while others are invasive and may include experiments that affect the integrity of the specimen. The researcher must count with the approval from a bioethical committee, to assure the best and minimum amount of experiments to assure high-quality data. If the 3D-SCAFF succeeds in being considered as biocompatible, analgesic and non-cytotoxic, then a human clinical trial can be designed.

The "Jump" to Clinical Trials—First Contact with Human Beings

Once all the needed preclinical data has been collected and all the required initial quality and biocompatibility tests have been cleared, IT’S TIME TO GO CLINICAL! (Fig. 2.2e). But, what exactly does this mean? What steps must the research group take in order to initiate human clinical trials?

As previously discussed, new information on disease mechanisms has been gamed through annual testing and experimental cellular designs, and new methods and materials for treating the targeted condition have been developed hi the laboratory. But. usually, the regulatory requirements to initiate human testing could be overwhelming, especially if not properly guided. Tracy points out five key elements that are desired to shorten the gap of taking a new medical dnrg/device to a clinical trial phase (i) the researchers and clinicians involved hi the product development must be adequately educated hi the translation process; (ii) it is desirable that tins translation process be standardized across different institutions; (iii) network connections between interdisciplinary teams must be promoted; (iv) optimized infrastructure for the translation process; and (v) proper funding for project management, bioethical regulatory process management, intellectual property management. informatics support, and for enabling industry-academy liaisons. If such elements are achieved, the process of taking a laboratory product for human testing should be much faster and the final step to becoming a commercially available product is much closer (Fig. 2.2f) (Tracy 2014).

Randomized Clinical Trials (RCTs) remain the gold standard study design to compare the effectiveness and safety of new biomaterials, medical/dental devices and clinical procedures, to prevent, diagnose or treat oral health conditions. Although, designing and executing RCTs could be more difficult and expensive than it may seem. For RCTs to provide significant input and really contribute to the translational process, these must be implemented with robust scientific rigor and all legal and bioethical matters must be considered. As stipulated by the FDA and EMA, the road to developing a new drug/device must consider safety and efficacy, in that order of priority. With all the required preclinic al data, a sponsor or drug developer, usually from industry or academia, will submit an Investigational New Drug (IND) application and then clinical research could begin (Kashyap et al. 2013).

RCTs are classified according to their purpose and should follow a specific order. Phase I stirdies are designed to test the safety and maximum tolerated dose (when testing a drag). Since this will be the first contact of the experimental product with humans, this study design usually involves a small number of healthy test subjects (20-100) and the product is open-labeled. Volunteers are very closely monitored for signs of toxicity and, bioethical issues must be especially addressed during informed consent, in order to avoid the misconception that participants will receive a therapeutic intervention. The FDA estimates that approximately 70% of these stirdies move to the next phase. Phase II trials also include a small number of volunteers (100-300), but unlike Phase I, participants have the condition or disease of interest. This design is used to understand more of the pharmacokinetics and the pharmacodynamics of the tested product including optimal doses, frequency of intake, administration routes and endpoints. These trials could be designed to provide valuable information for a much larger Phase III trial. Phase II trials will use some exploratory methods to understand the therapeutic efficacy of the product, but since only a small number of participants are recruited, they lack statistical power to infer any effect. FDA reports that 33% of Phase II studies will move to the next phase, and usually sponsors, researchers and the regulatory agency will meet at this point to discuss the preliminary data, IND, methodology of Phase III tr ials and any safety concerns (Umscheid et al. 2011).

Phase III RCTs are the next step in the road to an IND approval and are ethically justified only after enough data has been collected to satisfy the rigorous standards for product safety and potential efficacy. Phase III trials will recruit a number of participants (sample size) large enough to have statistical power to confirm therapeutic efficiency (300-3000). These trials will not only attempt to demonstrate and confinn efficacy in a significantly much larger sample of variedly ill volunteers, but also will identify common adverse reactions and how often these occur. Some characteristic RCT elements appear in this phase, including randomization, stratification ofparticipants and doubleblinding. A Phase III trial could take between 1-4 years to be completed, and approximately 25% of these studies will go to Phase IV. The ‘placebo-controlled trial’ is the most common design of Phase III RCTs. The experimental product’s efficacy and safety are compared to standard therapy or a sometimes controversially used placebo group. Another design for Phase III studies is the ‘equivalency trial’ and these will establish if the experimental product has equal efficacy than the available therapy. This equal efficacy is defined by researchers usually in a more clinical than statistically way. Many other designs exist depending on the purpose of the study, such as cross-over, factorial design and split-mouth (Lesaffre 2008; Pozos-Guillen et al. 2017; Ganocho-Rangel et al. 2019). Although Phase III RCTs are the gold standard for the drug/device approval process, the regulatory agency will require more than one Phase III trial to establish drag safety and efficacy, and in the pathway of clinical testing, this phase is where most of the resources (time and money) need to be invested.

For the researchers in charge of the clinical evaluation of the innovative 3D-SCAFF example, the first will be addressed to design a Phase I trial that will evaluate the behavior of the scaffold in a small group of healthy patients, obtaining important information to design further experiments. All trials should be evaluated by the pertinent bioethical committees and should be registered as well. Then, the following steps may include larger trials, as well as comparative experiments to evaluate the benefits between this new material and earlier similar options. A comparison will determine if the new biomaterial is ready to be introduced into the market. However, the complexity of this stage will need long processes and observation periods, so patience of the researches and the expecting witnesses is advised.

Surveillance and Monitoring—When the Ball is in the Court

Based on all the data generated from preclinical studies and Phases I, II and III clinical trials (prémarketing stirdies), the regulatory' agency approves the new drug/device (Fig. 2.2f). The most common adverse events have already been identified, and efficacy has been statistically demonstrated. However, the sponsor will usually be asked to run a Phase IV study (Fig. 2.2g), also referred to as ‘post-marketing’ or ‘pharmacovigilance’ studies. These are observational studies specifically designed to monitor the newly approved experimental product, concentrating on safety and effectiveness on a much larger scale. Just as Phase I is the first contact of the experimental product with humans. Phase IV studies are the first contact of the marketed product with the real world and, usually, several thousand volunteers who have the condition/disease participate in these long-lasting studies (Suvama 2010). Although much of the required information about the experimental product is already known, most of the in-depth understanding of the product will be attained during Phase IV studies. These studies will identify less common adverse reactions, evaluate cost and drug effectiveness across a larger range of methodological factors than those investigated previously. Different study designs could be implemented in the post-marketing phase, according to the targeted goal. Either the industry or the regulatory agency could be interested in looking into specific data regarding drug-drug interactions, formulation advancement, special safety, special populations (elderly, pediatrics, etc.), superiority vs. equivalence testing, pharmacovigilance studies, drug utilization studies and large sample trial (also called Phase V), among other existing designs. Moreover, these studies could contribute directly to the implementation of the product thr ough labeling changes, pricing negotiations and marketing (Glasser et al. 2007).

An alternative post-marketing design that can be utilized by sponsor companies or drug developers is the pragmatic trial. Unlike the RCT designs discussed so far, which aim to test whether an intervention works under optimal situations, pragmatic trials are designed to evaluate the effectiveness of interventions in real-life routine practice conditions. The results of these trials can be generalized and applied in daily practice settings and the strong internal validity (control for most potential biases) of RCT designs in exchange for a solid external validity (ability to generalize the results) of the pragmatic design (Patsopoulos 2011). Table 2.1 compares the basic characteristics of traditional RCTs and pragmatic trails.

Although the pragmatic trial concept has been used since 1967, when it was first introduced (Schwartz and Lellouch 1967), it was only in recent years when the scientific community started to be conscious of its pros and cons. It is important to highlight that implementing this design in more surveillance and monitoring studies will contribute to expanding the understanding of the behavior of newly approved medical products in real-life settings, encircling the full spectrum of the target population. They should not replace the exploratory prémarketing dials, but rather be a continuum of the pathway necessary to fully comprehend the safety and efficacy of a new product. These studies could be especially relevant for tissue engineering product development since the clinical application of these biomaterials could vastly vary among patients. The input pragmatic studies could open the door to new clinical necessities and products.

If the 3D SCAFF obtained the corr esponding permissions, it could probably be available in the market in the short term. Now, every' clinician will determine if this new material offers the ideal properties that were offered by the developers. The same clinicians and patients that ask for this new

Table 2.1. Comparison of RCTs vs pragmatic trial characteristics.

Randomized clinical trials

Pragmatic trials

Htgh internal validity Smaller sample size Sophrstrcated desrgn Controlled environment Prémarketing studres

Htgh external validity Large sample srze Sunpie desrgn Drverse settings Post-marketing studres

option will play a new role as observers and ‘anonymous evaluators’. They will report possible adverse effects or will even contribute by publishing clinical cases sharing their experience with 3D-SCAFF. Some users and researchers may also get involved in a pragmatic trial to fully understand the day-by-day behavior of the biomaterial. Curiously, with the new materials new clinical needs will also emerge, and maybe the cycle and the development of new materials will start up once again.

Conclusions

Tissue engineering provides a new era for therapeutic medicine; it is progressing very rapidly and extends to include all tissues in our physique. Three decades ago, tissue engineering was an idea and today it has become a potential treatment for numerous conditions. However, the road from the conception of new ideas to a frilly developed biomaterial is complex, and all the right steps to achieve a good product cannot be avoided. Not all the ideas will become a tangible option, many will be part of the laboratory ‘experience-stock’, but definitely every attempt will contribute to the process.

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  • [1] 1 Faculty of Dentistry, Universidad de Costa Rica, Costa Rica. Ciudad Universitaria Rodrigo Fació, San José Costa Rica. Email: This email address is being protected from spam bots, you need Javascript enabled to view it - National Laboratory of Nanotechnology, Costa Rica. 5 Faculty of Dentistry, Universidad Veracruzana, México. 4 Faculty of Dentistry, Universidad Autónoma de San Luis Potosi, México. 2 Corresponding author: This email address is being protected from spam bots, you need Javascript enabled to view it
 
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