Design of a Randomized Controlled Trial for Ebola Virus Disease Medical Countermeasures: PREVAIL II, the Ebola MCM Study

Using Bayesian statistics in confirmatory clinical trials in the regulatory setting: a tutorial review

Bayesian statistics plays a pivotal role in advancing medical science by enabling healthcare companies, regulators, and stakeholders to assess the safety and efficacy of new treatments, interventions, and medical procedures. The Bayesian framework offers a unique advantage over the classical framework, especially when incorporating prior information into a new trial with quality external data, such as historical data or another source of co-data. In recent years, there has been a significant increase in regulatory submissions using Bayesian statistics due to its flexibility and ability to provide valuable insights for decision-making, addressing the modern complexity of clinical trials where frequentist trials are inadequate. For regulatory submissions, companies often need to consider the frequentist operating characteristics of the Bayesian analysis strategy, regardless of the design complexity. In particular, the focus is on the frequentist type I error rate and power for all realistic alternatives. This tutorial review aims to provide a comprehensive overview of the use of Bayesian statistics in sample size determination, control of type I error rate, multiplicity adjustments, external data borrowing, etc., in the regulatory environment of clinical trials. Fundamental concepts of Bayesian sample size determination and illustrative examples are provided to serve as a valuable resource for researchers, clinicians, and statisticians seeking to develop more complex and innovative designs.

An evolutionary algorithm for the direct optimization of covariate balance between nonrandomized populations

Matching reduces confounding bias in comparing the outcomes of nonrandomized patient populations by removing systematic differences between them. Under very basic assumptions, propensity score (PS) matching can be shown to eliminate bias entirely in estimating the average treatment effect on the treated. In practice, misspecification of the PS model leads to deviations from theory and matching quality is ultimately judged by the observed post-matching balance in baseline covariates. Since covariate balance is the ultimate arbiter of successful matching, we argue for an approach to matching in which the success criterion is explicitly specified and describe an evolutionary algorithm to directly optimize an arbitrary metric of covariate balance. We demonstrate the performance of the proposed method using a simulated dataset of 275,000 patients and 10 matching covariates. We further apply the method to match 250 patients from a recently completed clinical trial to a pool of more than 160,000 patients identified from electronic health records on 101 covariates. In all cases, we find that the proposed method outperforms PS matching as measured by the specified balance criterion. We additionally find that the evolutionary approach can perform comparably to another popular direct optimization technique based on linear integer programming, while having the additional advantage of supporting arbitrary balance metrics. We demonstrate how the chosen balance metric impacts the statistical properties of the resulting matched populations, emphasizing the potential impact of using nonlinear balance functions in constructing an external control arm. We release our implementation of the considered algorithms in Python.

Towards achieving transnational research partnership equity: lessons from implementing adaptive platform trials in low- and middle-income countries

Background

Use of adaptive clinical trials, particularly adaptive platform trials, has grown exponentially in response to the coronavirus disease (COVID-19) pandemic. Implementation of these trials in low- and middle-income countries (LMICs) has been fostered through the formation or modification of transnational research partnerships, typically between research groups from LMICs and high-income countries (HICs). While these partnerships are important to promote collaboration and overcome the structural and economic disadvantages faced by LMIC health researchers, it is critical to focus attention on the multiple dimensions of partnership equity.

Methods

Based on informal literature reviews and a meeting with leaders of one of the multinational COVID-19 adaptive platform trials, we describe some important considerations about research partnership equity in this context.

Results

We organize these considerations into eight thematic categories: 1) epistemic structures, 2) funding, 3) ethics oversight, 4) regulatory oversight, 5) leadership, 6) post-trial access to interventions, data, and specimens, 7) knowledge translation and dissemination, and 8) research capacity strengthening and maintenance. Within each category we review normative claims that support its relevance to research partnership equity followed by discussion of how adaptive platform trials highlight new dimensions, considerations, or challenges.

Conclusion

In aggregate, these observations provide insight into procedural and substantive equity-building measures within transnational global health research partnerships more broadly.

GRADE concept 6: a novel application of external indirect evidence into GRADE ratings of evidence certainty in network meta-analysis

OBJECTIVES

We describe how consideration of external evidence may play an important role in judging certainty in the process of establishing the certainty of the evidence. Our example is a network meta-analysis (NMA) addressing treatment for Ebola virus disease, which informed a World Health Organization guideline.

STUDY DESIGN AND SETTING

Through Grading of Recommendations Assessment, Development, and Evaluations (GRADE) project group iterative online, in-person and email discussions, we developed this GRADE concept and obtained approval from the GRADE working group. Using the null as a threshold, we rated our certainty for network estimates in mortality, including consideration of evidence external to the NMA (i.e., did not meet eligibility criteria) and formal logical construction.

RESULTS

Based on the existing GRADE guidance, we rated the network estimate for one indirect comparison as low certainty. The formal logical construction that lead us reevaluate the certainty of the evidence is as follows: if A is superior to B, and B is not inferior to C, then A must be superior to C. After considering the logic and the external indirect evidence, we concluded at least moderate certainty for the comparison.

CONCLUSION

Systematic review authors and guideline developers should apply the fundamental logical construction for indirect comparisons and consider compelling external evidence in NMA certainty ratings.

Towards achieving transnational research partnership equity: lessons from implementing adaptive platform trials in low- and middle-income countries

Background: Use of adaptive clinical trials, particularly adaptive platform trials, has grown exponentially in response to the coronavirus disease (COVID-19) pandemic. Implementation of these trials in low- and middle-income countries (LMICs) has been fostered through the formation or modification of transnational research partnerships, typically between research groups from LMICs and high-income countries (HICs). While these partnerships are important to promote collaboration and overcome the structural and economic disadvantages faced by LMIC health researchers, it is critical to focus attention on the multiple dimensions of partnership equity. Methods: Based on informal literature reviews and meetings with leaders of one of the multinational COVID-19 adaptive platform trials, we describe what can be learned about research partnership equity from these experiences. Results: We organize these considerations into eight thematic categories: 1) epistemic structures, 2) funding, 3) ethics oversight, 4) regulatory oversight, 5) leadership, 6) post-trial access to interventions, data, and specimens, 7) knowledge translation, and 8) research capacity strengthening and maintenance. Within each category we review the normative claims that support its relevance to research partnership equity followed by discussion of how adaptive platform trials highlight new dimensions, considerations, or challenges. Conclusion: These observations provide insight into procedural and substantive equity-building measures within transnational global health research partnerships more broadly.

Integrating non-concurrent controls in the analyses of late-entry experimental arms in multi-arm trials with a shared control group in the presence of parameter drift

BACKGROUND

Under a master protocol, open platform trials allow new experimental treatments to enter an existing clinical trial. Whether late-entry experimental treatments should be compared to all available or concurrently randomized controls is not well established. Using all available data can increase power and precision; however, drift in population parameters can yield biased estimates and impact type I error rate.

METHODS

We explored the application of methods developed to incorporate historical controls in two-arm trials to the analysis of a late-entry arm in a simulated open platform trial under varying scenarios of parameter drift. Methods explored include test-then-pool, fixed power prior, dynamic power prior, and multi-source exchangeability model approaches.

RESULTS/CONCLUSIONS

Simulated trial results confirm that in the presence of no drift, naively pooling all controls increases power and produces more precise, unbiased estimates when compared to using concurrent controls only. However, under drift, pooling can result in type I error rate inflation or deflation and biased estimates. In the presence of parameter drift, methods that partially borrow non-concurrent data, either through a static weighting mechanism or through methods that allow the heterogeneity between non-concurrent and concurrent data to determine the degree of borrowing, are superior to naively pooling the data. However, compared to using concurrent controls only, these approaches cannot guarantee type I error control or unbiased estimates. Thus, concurrent controls should be used as comparators in confirmatory studies.

Prepared to Act: Lessons Learned by the Special Pathogens Research Network, Based on Collaborations with the NIAID-Led Adaptive COVID-19 Treatment Trial

The need for well-controlled clinical trials is fundamental to advancing medicine. Care should be taken to maintain high standards in trial design and conduct even during emergency medical events such as an infectious disease outbreak. In 2020, SARS-CoV-2 emerged and rapidly impacted populations around the globe. The need for effective therapeutics was immediately evident, prompting the National Institutes of Health to initiate the Adaptive COVID-19 Treatment Trial. The Special Pathogens Research Network, made up of 10 Regional Emerging Special Pathogens Treatment Centers, was approached to participate in this trial and readily joined the trial on short notice. By trial closure, the Special Pathogens Research Network sites, making up 19% of all study sites, enrolled 26% of the total participants. The initial resources available and experience in running clinical trials at each treatment center varied from minimal experience and few staff to extensive experience and a large staff. Based on experiences during the first phase of this trial, the Special Pathogens Research Network members provided feedback regarding operational lessons learned and recommendations for conducting future studies during a pandemic. Communication, collaboration, information technology, regulatory processes, and access to resources were identified as important topics to address. Key stakeholders including institutions, institutional review boards, and study personnel must maintain routine communication to efficiently and effectively activate when future research needs arise. Regular and standardized training for new personnel will aid in transitions and project continuity, especially in a rapidly evolving environment. Trainings should include local just-in-time training for new staff and sponsor-designed modules to refresh current staff knowledge. We offer recommendations that can be used by institutions and sponsors to determine goals and needs when preparing to set up this type of trial for critical, short-notice needs.

Learning in times of stress: Lessons from COVID-19 that will last throughout this century

Systems tend toward inertia until an external pressure pushes them toward change; thus, a situation of crisis such as the COVID-19 pandemic represents an opportunity for technological innovation. The prevailing need for treatments and vaccines has impelled innovation in the world of randomized clinical trials (RCT), resorting to ideas that had been floating around for a while. Is this merely a circumstantial phenomenon or are new methods here to stay?

Challenges in Evaluating Safety and Efficacy in Drug Development for Rare Diseases: A Review for Pharmacists

A rare disease, or orphan disease, in the United States is a condition with a national prevalence of fewer than 200,000 diagnoses. As therapies for rare diseases are developed and brought to market, pharmacists should understand the challenges of drug development for rare diseases and aid in educating patients about the approval process for rare disease therapies. Developing drugs for treating rare diseases presents unique challenges in proving the drug's safety and efficacy with adequate study design, power, and validity. Results of the clinical trials for rare diseases may be weakened by small patient populations, limited disease information, and difficulty defining end points and biomarkers. In addition to investigational barriers, pharmaceutical companies face financial barriers in justifying the investment of bringing a rare disease therapy to market. Federal programs, such as the Orphan Drug Act of 1983, expedited review, the Rare Pediatric Disease Priority Review Vouchers (RPD PRV) program, and the 21st Century Cures Act, give pharmaceutical companies motivation to develop therapies for rare diseases. The objective of this article is to provide pharmacists with an understanding of the challenges in designing clinical trials for drugs for rare diseases and discuss federal programs that address efforts to develop safe and efficacious drugs for rare diseases.

Urgently seeking efficiency and sustainability of clinical trials in global health

This paper shows the scale of global health research and the context in which we frame the subsequent papers in the Series. In this Series paper, we provide a historical perspective on clinical trial research by revisiting the 1948 streptomycin trial for pulmonary tuberculosis, which was the first documented randomised clinical trial in the English language, and we discuss its close connection with global health. We describe the current state of clinical trial research globally by providing an overview of clinical trials that have been registered in the WHO International Clinical Trial Registry since 2010. We discuss challenges with current trial planning and designs that are often used in clinical trial research undertaken in low-income and middle-income countries, as an overview of the global health trials landscape. Finally, we discuss the importance of collaborative work in global health research towards generating sustainable and culturally appropriate research environments.

Optimizing clinical research procedures in public health emergencies

Public Health Emergencies of International Concern, such as the coronavirus disease 2019 pandemic, have a devastating impact on an individual and societal level, and there is an urgent need to learn, understand and bridge the therapeutic gap at a time of extreme stress on the patient, health care systems and staff. Well-designed, controlled clinical trials play a crucial role in the discovery of novel diagnostic and management strategies; however, these catastrophic circumstances pose unique challenges in initiating research studies at institutional, national, and international levels, highlighting the importance of a coordinated, collaborative approach. This review discusses key elements necessary to consider for developing clinical trials within a Public Health Emergency setting.

Machine learning for clinical trials in the era of COVID-19

The world is in the midst of a pandemic. We still know little about the disease COVID-19 or about the virus (SARS-CoV-2) that causes it. We do not have a vaccine or a treatment (aside from managing symptoms). We do not know if recovery from COVID-19 produces immunity, and if so for how long, hence we do not know if "herd immunity" will eventually reduce the risk or if a successful vaccine can be developed - and this knowledge may be a long time coming. In the meantime, the COVID-19 pandemic is presenting enormous challenges to medical research, and to clinical trials in particular. This paper identifies some of those challenges and suggests ways in which machine learning can help in response to those challenges. We identify three areas of challenge: ongoing clinical trials for non-COVID-19 drugs; clinical trials for repurposing drugs to treat COVID-19, and clinical trials for new drugs to treat COVID-19. Within each of these areas, we identify aspects for which we believe machine learning can provide invaluable assistance.

Efficient Adaptive Designs for Clinical Trials of Interventions for COVID-19

The COVID-19 pandemic has led to an unprecedented response in terms of clinical research activity. An important part of this research has been focused on randomized controlled clinical trials to evaluate potential therapies for COVID-19. The results from this research need to be obtained as rapidly as possible. This presents a number of challenges associated with considerable uncertainty over the natural history of the disease and the number and characteristics of patients affected, and the emergence of new potential therapies. These challenges make adaptive designs for clinical trials a particularly attractive option. Such designs allow a trial to be modified on the basis of interim analysis data or stopped as soon as sufficiently strong evidence has been observed to answer the research question, without compromising the trial's scientific validity or integrity. In this article, we describe some of the adaptive design approaches that are available and discuss particular issues and challenges associated with their use in the pandemic setting. Our discussion is illustrated by details of four ongoing COVID-19 trials that have used adaptive designs.

The REMAP-CAP (Randomized Embedded Multifactorial Adaptive Platform for Community-acquired Pneumonia) Study. Rationale and Design

There is broad interest in improved methods to generate robust evidence regarding best practice, especially in settings where patient conditions are heterogenous and require multiple concomitant therapies. Here, we present the rationale and design of a large, international trial that combines features of adaptive platform trials with pragmatic point-of-care trials to determine best treatment strategies for patients admitted to an intensive care unit with severe community-acquired pneumonia. The trial uses a novel design, entitled "a randomized embedded multifactorial adaptive platform." The design has five key features: 1) randomization, allowing robust causal inference; 2) embedding of study procedures into routine care processes, facilitating enrollment, trial efficiency, and generalizability; 3) a multifactorial statistical model comparing multiple interventions across multiple patient subgroups; 4) response-adaptive randomization with preferential assignment to those interventions that appear most favorable; and 5) a platform structured to permit continuous, potentially perpetual enrollment beyond the evaluation of the initial treatments. The trial randomizes patients to multiple interventions within four treatment domains: antibiotics, antiviral therapy for influenza, host immunomodulation with extended macrolide therapy, and alternative corticosteroid regimens, representing 240 treatment regimens. The trial generates estimates of superiority, inferiority, and equivalence between regimens on the primary outcome of 90-day mortality, stratified by presence or absence of concomitant shock and proven or suspected influenza infection. The trial will also compare ventilatory and oxygenation strategies, and has capacity to address additional questions rapidly during pandemic respiratory infections. As of January 2020, REMAP-CAP (Randomized Embedded Multifactorial Adaptive Platform for Community-acquired Pneumonia) was approved and enrolling patients in 52 intensive care units in 13 countries on 3 continents. In February, it transitioned into pandemic mode with several design adaptations for coronavirus disease 2019. Lessons learned from the design and conduct of this trial should aid in dissemination of similar platform initiatives in other disease areas.Clinical trial registered with www.clinicaltrials.gov (NCT02735707).

Reporting of master protocols towards a standardized approach: A systematic review

BACKGROUND

In September 2018 the FDA provided a draft guidance on master protocols reflecting an increased interest in these designs by industry. Master protocols refer to a single overarching protocol developed to evaluate multiple hypotheses and may be further categorized as basket, umbrella, and platform trials. However, inconsistencies in reporting persist in the literature. We conducted a systematic review to describe master protocol reporting with the goal of facilitating the further development and spread of these innovative trial designs.

METHODS

We searched MEDLINE, EMBASE, and CENTRAL from inception to April 25, 2019 for English articles on master protocols. This was supplemented by hand searches of trial registries and of the bibliographies of published reviews. We used the FDA's definitions of master protocols as references and compared them to self-reported master protocols.

RESULTS

We identified 278 master protocol publications, consisting of 228 protocols and 50 reviews. Sixty-six records provided unique definitions of master protocol types. We observed considerable heterogeneity in definitions of master protocols, and over half (54%) used oncology-specific language. The majority of self-classified master protocols (57%) were consistent with the FDA's definitions of master protocols.

CONCLUSION

The terms 'master protocol', 'basket trial', 'umbrella trial', and 'platform trial' are inconsistently described. Careful treatment of these terms and adherence to the definitions set forth by the FDA will facilitate better understanding of these trial designs and allow them to be used broadly and to their full potential in clinical research. We encourage trial methodologists to use these trial designations when applicable.

The Past Need Not Be Prologue: Recommendations for Testing and Positioning the Most-Promising Medical Countermeasures for the Next Outbreak of Ebola Virus Infection

Background

The 2013-2016 outbreak of Ebola virus disease (EVD) in West Africa led to unprecedented morbidity and mortality. Although different classes of putative antiviral agents with supportive preclinical data were available for testing, and although several attempts to perform meaningful evaluation of these agents were undertaken during the epidemic, different research methods, a lack of appropriate controls in most studies, and formidable logistical challenges to completion of studies under field conditions hampered the success of these efforts. Ultimately only 1 randomized, placebo-controlled clinical trial (PREVAIL II) was performed in this setting, and, owing to a decrease in the number of new cases available for study, it, too, ended prior to reaching definitive results. Retrospective review of the lessons learned from this outbreak argues strongly for the need for much better preparedness in terms of selecting the trial design and drug(s) for use during the next outbreak.

Methods

Using recent data provided by representatives from the pharmaceutical industry, clinical and laboratory subject matter experts from the National Institute of Allergy and Infectious Diseases, other US government agencies, and academic partners were consulted regarding the current state of knowledge about several lead compounds with putative activity against EVD. Consensus was sought on recommendations concerning the most promising treatment strategies against EVD that should be studied in the context of a randomized clinical trial during the next outbreak.

Results

Four compounds from 2 different classes (monoclonal antibody [mAb] cocktails and direct-acting antiviral agents [DAAs]) were highlighted as lead candidates, limitations in the current knowledge base about these drug classes were reviewed, and recommendations about the optimal clinical research design for studying combinations of these different agents were made.

Conclusions

Although achieving the desired sample size could be challenging, a randomized, controlled clinical trial based on a combination strategy of a mAb with a DAA was recommended as the most appropriate clinical trial design to be undertaken during the next outbreak of EVD.

A multi-source adaptive platform design for testing sequential combinatorial therapeutic strategies

Traditional paradigms for clinical translation are challenged in settings where multiple contemporaneous therapeutic strategies have been identified as potentially beneficial. Platform trials have emerged as an approach for sequentially comparing multiple trials using a single protocol. The Ebola virus disease outbreak in West Africa represents one recent example which utilized a platform design. Specifically, the PREVAIL II master protocol sequentially tested new combinations of therapies against the concurrent, optimal standard of care (oSOC) strategy. Once a treatment demonstrated sufficient evidence of benefit, the treatment was added to the oSOC for all future comparisons (denoted as segments throughout the manuscript). In the interest of avoiding bias stemming from population drift, PREVAIL II considered only within-segment comparisons between the oSOC and novel treatments and failed to leverage data from oSOC patients in prior segments. This article describes adaptive design methodology aimed at boosting statistical power through Bayesian modeling and adaptive randomization. Specifically, the design uses multi-source exchangeability models to combine data from multiple segments and adaptive randomization to achieve information balance within a segment. When compared to the PREVAIL II design, we demonstrate that our proposed adaptive platform design improves power by as much as 51% with limited type-I error inflation. Further, the adaptive platform effectuates more balance with respect to the distribution of acquired information among study arms, with more patients randomized to experimental regimens.

[Integrating clinical research into epidemic response: the field perspective in the Ebola experience]

During the 2013-2016 west African Ebola outbreak that affected West Africa, accelerated clinical trials, testing unproven but promising and potentially lifesaving experimental interventions emerged as a key component of the global outbreak. In 2017, no Ebola medical countermeasures had proven antiviral efficacy in patients. However, in September 2014, the World Health Organization inventoried a list of potential drug candidates developed or repurposed with demonstrated antiviral efficacy in vitro or in animal models. Numerous therapeutics were considered or explored during the outbreak, including nucleoside and nucleotide analogues, nucleic acid-based drugs and immunotherapeutics. Drugs in clinical trials were tested within the framework of optimized supportive care with fluids and electrolytes and management of severe compromise of multiple organs resulting from viral cytopathology and immune-mediated cell damage. Assessment of those therapeutics with encouraging preliminary efficacy or safety profile, like the repurposed direct antiviral agent favipiravir or the combination of antibodies ZMapp requires further investigation to confirm their efficacy in humans, propose appropriate doses and evaluate the possibility of treatment combinations. During the lull before the next epidemic, major challenges for managing future Ebola epidemics include scientific, clinical and public health preparedness with establishment of innovative patient care and clinical research support in remote poor areas where Ebola and other deadly infectious diseases typically reemerge.

Clinical Evaluation of Ebola Virus Disease Therapeutics

Ebola virus disease (EVD) was first described over 40 years ago, but no treatment has been approved for humans. The 2013-2016 EVD outbreak in West Africa has expedited the clinical evaluation of several candidate therapeutics that act through different mechanisms, but with mixed results. Nevertheless, these studies are important because the accumulation of clinical data and valuable experience in conducting efficacy trials under emergency circumstances will lead to better implementation of similar studies in the future. Here, we summarize the results of EVD clinical trials, focus on the discussion of factors that may have potentially impeded the effectiveness of existing candidate therapeutics, and highlight considerations that may help meet the challenges ahead in the quest to develop clinically approved drugs.

Collaboration of the NIH and PHS Commissioned Corps in the International Ebola Clinical Research Response

The U.S. response to the Ebola epidemic resulted in many federal agencies assessing their ability to respond to global threats and improve the efficiency of humanitarian efforts.

Antiviral therapeutics for the treatment of Ebola virus infection

There have been significant developments in Ebola virus therapeutics. While the efficacy of several products was evaluated in the recent West Africa outbreak, a licensed treatment for EBOV disease remains elusive. Factors that negatively impacted the execution of clinical trials included an overall lack of world readiness to conduct clinical trials in an outbreak setting, ethical concerns limiting implementation of the randomized controlled trials in an outbreak setting, and a decline in case numbers by the time resources were mobilized to conduct clinical trials. We summarize relevant therapeutics that underwent clinical trials during the West Africa outbreak and highlight promising candidates under advanced development.

Antibody therapies for the prevention and treatment of viral infections

Antibodies are an important component in host immune responses to viral pathogens. Because of their unique maturation process, antibodies can evolve to be highly specific to viral antigens. Physicians and researchers have been relying on such high specificity in their quest to understand host–viral interaction and viral pathogenesis mechanisms and to find potential cures for viral infection and disease. With more than 60 recombinant monoclonal antibodies developed for human use in the last 20 years, monoclonal antibodies are now considered a viable therapeutic modality for infectious disease targets, including newly emerging viral pathogens such as Ebola representing heightened public health concerns, as well as pathogens that have long been known, such as human cytomegalovirus. Here, we summarize some recent advances in identification and characterization of monoclonal antibodies suitable as drug candidates for clinical evaluation, and review some promising candidates in the development pipeline.

Bayesian randomized clinical trials: From fixed to adaptive design

Randomized controlled studies are the gold standard for phase III clinical trials. Using α-spending functions to control the overall type I error rate, group sequential methods are well established and have been dominating phase III studies. Bayesian randomized design, on the other hand, can be viewed as a complement instead of competitive approach to the frequentist methods. For the fixed Bayesian design, the hypothesis testing can be cast in the posterior probability or Bayes factor framework, which has a direct link to the frequentist type I error rate. Bayesian group sequential design relies upon Bayesian decision-theoretic approaches based on backward induction, which is often computationally intensive. Compared with the frequentist approaches, Bayesian methods have several advantages. The posterior predictive probability serves as a useful and convenient tool for trial monitoring, and can be updated at any time as the data accrue during the trial. The Bayesian decision-theoretic framework possesses a direct link to the decision making in the practical setting, and can be modeled more realistically to reflect the actual cost-benefit analysis during the drug development process. Other merits include the possibility of hierarchical modeling and the use of informative priors, which would lead to a more comprehensive utilization of information from both historical and longitudinal data. From fixed to adaptive design, we focus on Bayesian randomized controlled clinical trials and make extensive comparisons with frequentist counterparts through numerical studies.

Will There Be a Cure for Ebola?

Despite the unprecedented Ebola virus outbreak response in West Africa, no Ebola medical countermeasures have been approved by the US Food and Drug Administration. However, multiple valuable lessons have been learned about the conduct of clinical research in a resource-poor, high risk-pathogen setting. Numerous therapeutics were explored or developed during the outbreak, including repurposed drugs, nucleoside and nucleotide analogues (BCX4430, brincidofovir, favipiravir, and GS-5734), nucleic acid-based drugs (TKM-Ebola and AVI-7537), and immunotherapeutics (convalescent plasma and ZMapp). We review Ebola therapeutics progress in the aftermath of the West Africa Ebola virus outbreak and attempt to offer a glimpse of a path forward.

[Science in a crisis. Medical countermeasures in Ebola virus disease, 2016: lessons learned and perspectives]

In 2013, the world began to witness an unprecedented Ebola epidemic in West Africa that was smoldering by early 2016. Under this urgent circumstance, the global scientific community organized and made progress in identifying potential preventive countermeasures and therapeutics and accelerated the development of those promising interventions. Trials of experimental interventions soon emerged as a key component of the global response. Hence, an interdisciplinary issue ensued concerning how best to assess clinical safety and effectiveness of potential interventions prior to or concurrent with their broad use in humans. Key issues rely on the close collaboration between research and clinical teams involved in care in the field. Indeed, it is of prime importance to consider cultural dimensions when aiming to build trust within communities and flexibility to adapt trial procedures to field constraints. Trials implemented during the outbreak crisis illustrates challenging inputs for producing scientific and ethical gains for the benefits of vulnerable populations in the context of an international emerging or re-emerging infectious disease event. This includes rapid implementation of clinical research studies from the early phase of the next global outbreak on the basis of practical and ready-to-apply innovative methodological framework built during interepidemic periods.

Treating the host response to emerging virus diseases: lessons learned from sepsis, pneumonia, influenza and Ebola

There is an ongoing threat of epidemic or pandemic diseases that could be caused by influenza, Ebola or other emerging viruses. It will be difficult and costly to develop new drugs that target each of these viruses. Statins and angiotensin receptor blockers (ARBs) have been effective in treating patients with sepsis, pneumonia and influenza, and a statin/ARB combination appeared to dramatically reduce mortality during the recent Ebola outbreak. These drugs target (among other things) the endothelial dysfunction found in all of these diseases. Most scientists work on new drugs that target viruses, and few accept the idea of treating the host response with generic drugs. A great deal of research will be needed to show conclusively that these drugs work, and this will require the support of public agencies and foundations. Investigators in developing countries should take an active role in this research. If the next Public Health Emergency of International Concern is caused by an emerging virus, a "top down" approach to developing specific new drug treatments is unlikely to be effective. However, a "bottom up" approach to treatment that targets the host response to these viruses by using widely available and inexpensive generic drugs could reduce mortality in any country with a basic health care system. In doing so, it would make an immeasurable contribution to global equity and global security.

A Randomized, Controlled Trial of ZMapp for Ebola Virus Infection

BACKGROUND

Data from studies in nonhuman primates suggest that the triple monoclonal antibody cocktail ZMapp is a promising immune-based treatment for Ebola virus disease (EVD).

METHODS

Beginning in March 2015, we conducted a randomized, controlled trial of ZMapp plus the current standard of care as compared with the current standard of care alone in patients with EVD that was diagnosed in West Africa by polymerase-chain-reaction (PCR) assay. Eligible patients of any age were randomly assigned in a 1:1 ratio to receive either the current standard of care or the current standard of care plus three intravenous infusions of ZMapp (50 mg per kilogram of body weight, administered every third day). Patients were stratified according to baseline PCR cycle-threshold value for the virus (≤22 vs. >22) and country of enrollment. Oral favipiravir was part of the current standard of care in Guinea. The primary end point was mortality at 28 days.

RESULTS

A total of 72 patients were enrolled at sites in Liberia, Sierra Leone, Guinea, and the United States. Of the 71 patients who could be evaluated, 21 died, representing an overall case fatality rate of 30%. Death occurred in 13 of 35 patients (37%) who received the current standard of care alone and in 8 of 36 patients (22%) who received the current standard of care plus ZMapp. The observed posterior probability that ZMapp plus the current standard of care was superior to the current standard of care alone was 91.2%, falling short of the prespecified threshold of 97.5%. Frequentist analyses yielded similar results (absolute difference in mortality with ZMapp, -15 percentage points; 95% confidence interval, -36 to 7). Baseline viral load was strongly predictive of both mortality and duration of hospitalization in all age groups.

CONCLUSIONS

In this randomized, controlled trial of a putative therapeutic agent for EVD, although the estimated effect of ZMapp appeared to be beneficial, the result did not meet the prespecified statistical threshold for efficacy. (Funded by the National Institute of Allergy and Infectious Diseases and others; PREVAIL II ClinicalTrials.gov number, NCT02363322 .).

Ebola virus disease and critical illness

As of 20 May 2016 there have been 28,646 cases and 11,323 deaths resulting from the West African Ebola virus disease (EVD) outbreak reported to the World Health Organization. There continue to be sporadic flare-ups of EVD cases in West Africa.EVD presentation is nonspecific and characterized initially by onset of fatigue, myalgias, arthralgias, headache, and fever; this is followed several days later by anorexia, nausea, vomiting, diarrhea, and abdominal pain. Anorexia and gastrointestinal losses lead to dehydration, electrolyte abnormalities, and metabolic acidosis, and, in some patients, acute kidney injury. Hypoxia and ventilation failure occurs most often with severe illness and may be exacerbated by substantial fluid requirements for intravascular volume repletion and some degree of systemic capillary leak. Although minor bleeding manifestations are common, hypovolemic and septic shock complicated by multisystem organ dysfunction appear the most frequent causes of death.Males and females have been equally affected, with children (0-14 years of age) accounting for 19 %, young adults (15-44 years) 58 %, and older adults (≥45 years) 23 % of reported cases. While the current case fatality proportion in West Africa is approximately 40 %, it has varied substantially over time (highest near the outbreak onset) according to available resources (40-90 % mortality in West Africa compared to under 20 % in Western Europe and the USA), by age (near universal among neonates and high among older adults), and by Ebola viral load at admission.While there is no Ebola virus-specific therapy proven to be effective in clinical trials, mortality has been dramatically lower among EVD patients managed with supportive intensive care in highly resourced settings, allowing for the avoidance of hypovolemia, correction of electrolyte and metabolic abnormalities, and the provision of oxygen, ventilation, vasopressors, and dialysis when indicated. This experience emphasizes that, in addition to evaluating specific medical treatments, improving the global capacity to provide supportive critical care to patients with EVD may be the greatest opportunity to improve patient outcomes.

Considerations for Use of Investigational Drugs in Public Health Emergencies

The paradigm for the use of investigational drugs in public health emergencies has been recently tested to prevent and treat highly infectious and lethal diseases. Examples include the successful implementation of vaccine and therapeutic clinical trials during the recent Ebola outbreak in West Africa. On the other end of the spectrum was the Emergency Use Authorization (EUA) of peramivir in the treatment of H1N1 influenza virus that did not provide an opportunity to collect data or understand the effectiveness of the EUA program. Between the gold standard of a randomized controlled clinical trial and the problems associated with EUAs are the domain of expanded access protocols that may provide an avenue to make products available while awaiting licensure. This paper will examine the regulatory pathways in the United States (US) for the use of investigational drugs in a public health emergency as well as considerations when making these products available outside the US. Descriptions of the applications of the various approaches will be presented. Regardless of the pathway chosen, public health and clinical research planners need to work together to consider several factors associated with the respective options and maintain a goal of working toward the collection of data to support licensure before faced with future outbreaks. Finally, this paper will consider the lessons learned from public health response in the context of investigational drugs in other diseases where "right to try laws" may pose opportunities, as well as challenges.