Guide for Combining Primary Tumors for Statistical Analysis in Rodent Carcinogenicity Studies.

The Tumor Combination Guide was created at the request of the U. S. Food and Drug Administration (FDA) by a Working Group of biopharmaceutical experts from international societies of toxicologic pathology, the Food and Drug Administration (FDA), and members of the Standard for Exchange of Nonclinical Data (SEND) initiative, to assist pharmacology/toxicology reviewers and biostatisticians in statistical analysis of nonclinical tumor data. The guide will also be useful to study and peer review pathologists in interpreting the tumor data. This guide provides a higher-level hierarchy of tumor types or categories correlating the tumor names from the International Harmonization of Nomenclature and Diagnostic Criteria (INHAND) publications with those available in the NEOPLASM controlled terminology (CT) code list in SEND. The version of CT used in a study should be referenced in the nonclinical study data reviewer's guide (SDRG) (section 3.1) of electronic submissions to the FDA. The tumor combination guide instructions and examples are in a tabular format to make informed decisions for combining tumor data for statistical analysis. The strategy for combining tumor types for statistical analysis is based on scientific criteria gleaned from the current scientific literature; as SEND and INHAND terminology and information evolve, this guide will be updated.

Evaluating the sensitivity of newborn rats and newborn hamsters to oncogenic DNA.

To evaluate the risk of residual cellular DNA in vaccines manufactured in tumorigenic cell lines, we have been establishing in vivo assays to quantify the oncogenic activity of DNA. We had generated three oncogene-expression plasmids: pMSV-T24-H-ras, which expresses activated H-ras; pMSV-c-myc, which expresses c-myc; and pMSV-T24-H-ras/MSV-c-myc, which expresses both oncogenes. Tumors were induced in mice by pMSV-T24-H-ras plus pMSV-c-myc or by pMSV-T24-H-ras/MSV-c-myc. Because newborn hamsters and newborn rats have been recommended for oncogenicity testing of the DNA from tumorigenic mammalian cell-substrates used for vaccine production, we evaluated their sensitivity. Newborn hamsters and rats were inoculated with different doses of pMSV-T24-H-ras/MSV-c-myc to determine their sensitivity to tumor induction and with the single-oncogene-expression plasmids to determine whether single oncogenes could induce tumors. Newborn rats were more sensitive than newborn hamsters, and activated H-ras but not c-myc induced tumors in newborns of both rodent species. DNA from four cell lines established from tumors induced by pMSV-T24-H-ras/MSV-c-myc was inoculated into newborn rats. Because no tumors were induced by this cellular DNA, which should be optimal as it contains both oncogenes linked and present in several copies, we conclude that available in vivo models are not sensitive enough to detect the oncogenicity of cellular DNA.

A U.S. Government-Coordinated Effort to Leverage Non-Human Primate Data to Facilitate Ebolavirus Vaccine Development.

A United States Government (USG) interagency group, the Filovirus Animal Non-Clinical Group (FANG), has been established to support the development of biodefense medical countermeasures (MCMs). As both vaccines and therapeutics are licensed using "non-traditional pathways", such as the U.S. Food and Drug Administration's (FDA) Animal Rule (AR), non-human primate (NHP) models and associated assays have been developed and standardized across BSL4 testing sites to evaluate candidate products. Vaccine candidates are evaluated using these NHP models, and through this public-private partnership, a meta-analysis of NHP control data has been conducted and submitted to the FDA as a master file. This is an example of how existing NHP control data can be leveraged in lieu of conducting separate natural history studies at multiple testing facilities to demonstrate the consistency of a standardized animal model for vaccine development. As a result, animal use can be minimized and the duplication of effort avoided, thus reducing the amount of time needed to conduct additional studies, as well as the cost of vaccine candidate development. This successful strategy may be applied to other pathogens of high consequence for vaccine development, and shows how strategic preparedness for biodefense can be leveraged in response to outbreaks and public health emergencies.

The African Green Monkey Model of Pneumonic Plague and US Food and Drug Administration Approval of Antimicrobials Under the Animal Rule.

BACKGROUND: Additional treatment options for pneumonic plague, the most severe form of infection by Yersinia pestis, are needed, as past US Food and Drug Administration (FDA) approvals were not based on clinical trials that meet today's standards, and multiple drugs are sought to counter resistance or use in special populations. Due to the sporadic nature of outbreaks and the low number of pneumonic cases of disease, we sought FDA approval of antimicrobials for treatment under the Animal Efficacy Rule, where efficacy can be demonstrated in 1 or more well-characterized animal models that sufficiently represent human disease. METHODS: A model was developed in African green monkeys (AGMs) after challenge with a lethal dose of Y. pestis delivered as an aerosol, in 4 independent studies in 3 laboratories. The primary data points were bacteremia (daily), body temperature and heart rate (continuously monitored by telemetry), and survival. In antimicrobial efficacy studies, human-equivalent doses of gentamicin, ciprofloxacin, levofloxacin, and doxycycline were administered upon fever onset for 10 days. RESULTS: Disease in AGMs was similar to case reports of human disease. Fever was determined to be a reliable sign of disease and selected as a treatment trigger. Gentamicin was 60%-80% effective depending on the dose given to animals. Ciprofloxacin and levofloxacin were found to be >90% efficacious. These data were submitted to FDA and plague indications were approved. Doxycycline was less effective. CONCLUSIONS: The AGM model of pneumonic plague is reproducible, well-characterized, and mimics human disease. It has been used to support plague indications for fluoroquinolones and to test the efficacy of additional antimicrobials.

Effect of Delaying Treatment on Efficacy of Ciprofloxacin and Levofloxacin in the African Green Monkey Model of Pneumonic Plague.

BACKGROUND: Ciprofloxacin and levofloxacin, 2 fluoroquinolone antimicrobials, are ≥90% effective for the treatment of inhalational plague when administered within 2-6 hours of fever onset in African green monkeys (AGM). Based on data in the AGM model, these antimicrobials were approved under the Food and Drug Administration's Animal Efficacy Rule. However, that data did not address the issue of how long treatment with these antimicrobials would remain effective after fever onset. METHODS: The AGM model of pneumonic plague was used to explore the effect of delaying treatment with ciprofloxacin and levofloxacin on efficacy. In 2 studies, AGMs were challenged with inhaled lethal doses of Yersinia pestis. Treatment with ciprofloxacin and levofloxacin was initiated from 0 to up to 30 hours after fever onset. RESULTS: Challenged animals all developed fever within 78 hours and were treated with ciprofloxacin (n = 27) or levofloxacin (n = 29) at various predetermined time points postfever. When administered 10 hours after fever onset, 10 days of ciprofloxacin and levofloxacin treatment remained very effective (90 or 100%, respectively). The efficacy of both antimicrobials declined as treatment initiation was further delayed. Statistical analyses estimated the treatment delay times at which half of the AGMs were no longer expected to survive as 19.7 hours for ciprofloxacin and 26.5 hours for levofloxacin. CONCLUSIONS: This study demonstrates that there is a narrow window following fever onset during which ciprofloxacin and levofloxacin are fully effective treatment options for pneumonic plague in AGMs. Since the timing of disease is similar in humans and AGMs, these AGM data are reasonably likely to predict response times for treatment in humans.

Retrospective Analysis of Pneumonic Tularemia in Operation Whitecoat Human Subjects: Disease Progression and Tetracycline Efficacy.

Francisella tularensis is a highly infectious Gram-negative bacterium that is the etiologic agent of tularemia in animals and humans. The incidence of tularemia is very low with a lack of comprehensive data that describe disease in humans due to difficulty in understanding time and routes of exposure. Under the title Operation Whitecoat, researchers at Ft. Detrick, MD conducted 40 clinical studies of tularemia from 1958 to 1968. In these studies, one of the objectives was to evaluate candidate countermeasures for treatment or prophylaxis of disease after exposure to Francisella tularensis strain Schu S4 by inhalation. These studies were reviewed retrospectively to delineate the early signs and symptoms or natural history of pneumonic tularemia and examine the efficacy of tetracycline in controlled human clinical studies. Using vital signs, onset of fever was objectively defined and calculated for each subject, while Adverse Events reported after exposure were also used to define the timing of disease onset and symptoms of early disease. There was a dose response relationship between time to fever onset and exposed dose at 200 cfu (172.8 h), 700 cfu (163.2 h), 2,500 cfu (105.3 h), and 25,000 cfu (75.5 h). Onset of fever was typically the earliest sign of disease at all doses but was often accompanied by symptoms such as headache, myalgia, chest pain, and nausea, irrespective of dose except at 200 cfu where only 50% of subjects exhibited fever onset or symptoms. Examining the efficacy of different treatment regimens of tetracycline, ineffective treatments were indicated by relapse of disease (fever and Adverse Events) after cessation of antibiotic treatment. Stratification of the data suggested that treatment for <14 days or doses <2g/day was associated with increased percentage of subjects with relapse of disease symptoms. Although these types of human challenge studies would not be ethically possible now, the climate post-World War II supported human testing under rigorous conditions with informed consent. Thus, going back and analyzing these unique clinical human challenge studies has helped describe the course of infection and disease induced by a biothreat pathogen and possible countermeasures for treatment under controlled conditions.

Responsiveness to basement membrane extract as a possible trait for tumorigenicity characterization.

Immortalized cell lines used to produce vaccines are expected to be described in terms of their tumorigenicity. However, current in vivo tumorigenicity assays can be time-consuming and results can be equivocal, especially for weakly tumorigenic cells. Basement membrane extract (BME) derived from the Engelbreth-Holm-Swarm mouse tumor, such as Matrigel and Cultrex, consists of laminin, collagen IV, entactin, heparan sulfate, and proteoglycans, as well as biologically active peptides and growth factors. For nearly three decades, BME has been used in cancer research to enhance tumorigenicity assays (both tumor "take" as well as tumor growth are substantially improved). We assessed the feasibility of using BME to facilitate the evaluation of vaccine cell substrate tumorigenicity. Vero cells (WHO 10-87) were serially passaged and banked at every ten passages beginning with p140; for the present study, low-passage Vero cells (Vero LP, originating from cells banked at p140) and high-passage Vero cells (Vero HP, originating from cells banked at p250) were used. In addition, Vero TPX2 and Vero NM1, cell lines established from tumors formed in nude mice by Vero HP cells, as well as other cell lines relevant to vaccine production (HeLa, MDCK, 293, and ARPE-19), were assessed. Female adult athymic nude mice were injected subcutaneously with cells in the absence or presence of BME. We observed that the tumorigenicity of ARPE-19 cells as well as Vero cells below passage 258 (Vero LP and Vero HP; previously characterized as non-tumorigenic or weakly tumorigenic, respectively) was not enhanced by BME. In contrast, BME shortened the latency and decreased the tumor-producing cell dose of HeLa, 293, and MDCK cells as well as the tumorigenic Vero derivatives TPX2 and NM1. Thus, responsiveness to BME may reflect the status of the neoplastic process and possibly serve as a useful trait for better defining the tumorigenic phenotype of cells.

The Cynomolgus Macaque Natural History Model of Pneumonic Tularemia for Predicting Clinical Efficacy Under the Animal Rule.

Francisella tularensis is a highly infectious Gram-negative bacterium that is the etiologic agent of tularemia in animals and humans and a Tier 1 select agent. The natural incidence of pneumonic tularemia worldwide is very low; therefore, it is not feasible to conduct clinical efficacy testing of tularemia medical countermeasures (MCM) in human populations. Development and licensure of tularemia therapeutics and vaccines need to occur under the Food and Drug Administration's (FDA's) Animal Rule under which efficacy studies are conducted in well-characterized animal models that reflect the pathophysiology of human disease. The Tularemia Animal Model Qualification (AMQ) Working Group is seeking qualification of the cynomolgus macaque (Macaca fascicularis) model of pneumonic tularemia under Drug Development Tools Qualification Programs with the FDA based upon the results of studies described in this manuscript. Analysis of data on survival, average time to death, average time to fever onset, average interval between fever and death, and bacteremia; together with summaries of clinical signs, necropsy findings, and histopathology from the animals exposed to aerosolized F. tularensis Schu S4 in five natural history studies and one antibiotic efficacy study form the basis for the proposed cynomolgus macaque model. Results support the conclusion that signs of pneumonic tularemia in cynomolgus macaques exposed to 300-3,000 colony forming units (cfu) aerosolized F. tularensis Schu S4, under the conditions described herein, and human pneumonic tularemia cases are highly similar. Animal age, weight, and sex of animals challenged with 300-3,000 cfu Schu S4 did not impact fever onset in studies described herein. This study summarizes critical parameters and endpoints of a well-characterized cynomolgus macaque model of pneumonic tularemia and demonstrates this model is appropriate for qualification, and for testing efficacy of tularemia therapeutics under Animal Rule.

A Comparison of the Pathogenesis of Marburg Virus Disease in Humans and Nonhuman Primates and Evaluation of the Suitability of These Animal Models for Predicting Clinical Efficacy under the 'Animal Rule'.

Marburg virus outbreaks are sporadic, infrequent, brief, and relatively small in terms of numbers of subjects affected. In addition, outbreaks most likely will occur in remote regions where clinical trials are not feasible; therefore, definitive, well-controlled human efficacy studies to test the effectiveness of a drug or biologic product are not feasible. Healthy human volunteers cannot ethically be deliberately exposed to a lethal agent such as Marburg virus in order to test the efficacy of a therapy or preventive prior to licensure. When human efficacy studies are neither ethical nor feasible, the US Food and Drug Administration may grant marketing approval of a drug or biologic product under the 'Animal Rule,' through which demonstration of the efficacy of a product can be 'based on adequate and well-controlled animal efficacy studies when the results of those studies establish that the drug is reasonably likely to produce clinical benefit in humans.' This process requires that the pathogenic determinants of the disease in the animal model are similar to those that have been identified in humans. After reviewing primarily English-language, peer-reviewed journal articles, we here summarize the clinical manifestations of Marburg virus disease and the results of studies in NHP showing the characteristics and progression of the disease. We also include a detailed comparison of the characteristics of the human disease relative to those for NHP. This review reveals that the disease characteristics of Marburg virus disease are generally similar for humans and 3 NHP species: cynomolgus macaques (Macaca fascicularis), rhesus macaques (Macaca mulatta), and African green monkeys (Chlorocebus aethiops).

A mouse strain defective in both T cells and NK cells has enhanced sensitivity to tumor induction by plasmid DNA expressing both activated H-Ras and c-Myc.

As part of safety studies to evaluate the risk of residual cellular DNA in vaccines manufactured in tumorigenic cells, we have been developing in vivo assays to detect and quantify the oncogenic activity of DNA. We generated a plasmid expressing both an activated human H-ras gene and murine c-myc gene and showed that 1 µg of this plasmid, pMSV-T24-H-ras/MSV-c-myc, was capable of inducing tumors in newborn NIH Swiss mice. However, to be able to detect the oncogenicity of dominant activated oncogenes in cellular DNA, a more sensitive system was needed. In this paper, we demonstrate that the newborn CD3 epsilon transgenic mouse, which is defective in both T-cell and NK-cell functions, can detect the oncogenic activity of 25 ng of the circular form of pMSV-T24-H-ras/MSV-c-myc. When this plasmid was inoculated as linear DNA, amounts of DNA as low as 800 pg were capable of inducing tumors. Animals were found that had multiple tumors, and these tumors were independent and likely clonal. These results demonstrate that the newborn CD3 epsilon mouse is highly sensitive for the detection of oncogenic activity of DNA. To determine whether it can detect the oncogenic activity of cellular DNA derived from four human tumor-cell lines (HeLa, A549, HT-1080, and CEM), DNA (100 µg) was inoculated into newborn CD3 epsilon mice both in the presence of 1 µg of linear pMSV-T24-H-ras/MSV-c-myc as positive control and in its absence. While tumors were induced in 100% of mice with the positive-control plasmid, no tumors were induced in mice receiving any of the tumor DNAs alone. These results demonstrate that detection of oncogenes in cellular DNA derived from four human tumor-derived cell lines in this mouse system was not possible; the results also show the importance of including a positive-control plasmid to detect inhibitory effects of the cellular DNA.

Shifting the paradigm of coral-reef 'health' assessment.

Coral reefs are in crisis. Globally, our reefs are degrading at an accelerating rate and present methodologies for coral-reef 'health' assessment, although providing important information in describing these global declines, have been unable to halt these declines. These assessments are usually employed with no clear purpose and using uncorrelated methods resulting in a failure to prevent or mitigate coral reef deterioration. If we are to ever successfully intervene, we must move beyond the current paradigm, where assessments and intervention decisions are based primarily on descriptive science and embrace a paradigm that promotes both descriptive and mechanistic science to recognize a problem, and recognize it before it becomes a crisis. The primary methodology in this alternative paradigm is analogous to the clinical and diagnostic methodologies of evidence-based medicine. Adopting this new paradigm can provide the evidence to target management actions on those stressors currently impacting reef ecosystems as well as providing a means for proactive management actions to avert irreversible habitat decline.