FDA draft guidance on adaptive design clinical trials: Pfizer's perspective

The Food and Drug Administration of the United States issued a draft guidance on adaptive design clinical trials in February 2010. This draft guidance has attracted a lot of attention because of the increasing interest in adaptive trials by the pharmaceutical industry in recent years. In this paper, we report on highlights of comments collected within Pfizer on this draft guidance. In addition, we share Pfizer's internal journey to promote efficient trial designs since 2005. Adaptive designs have been part of that journey.     

An FDA perspective on general pharmacology studies to determine activity and safety

General pharmacology studies are conducted to determine various pharmacological activities, as part of drug discovery or to define some specific issues which are relevant to safety. Regulatory submissions of biological products, unlike other therapeutics classes of agents, e.g., drugs, are frequently accompanied by extensive information regarding their preclinical aspects of physiology, biochemistry, and pharmacology. Although not true in every instances, biologic products exert their effects in a highly specific manner. Various fundamental aspects of protein chemistry and receptor function combine to restrict the spectrum of pharmacological and toxicological effects likely to occur. General pharmacology studies may be conducted either separately or nested in larger studies assessing general toxicity. Pharmacology studies are used best in an attempt to answer specific questions and are particularly effective when complementing other tests of safety. © 1995 Wiley-Liss, Inc.     

Developments in antivirals against influenza, smallpox and hemorrhagic fever viruses

INTRODUCTION: the search for effective inhibitors to multiple infectious agents including influenza, smallpox and hemorrhagic fever viruses is an area of active research as many of these agents pose dramatic health and economic challenges to the human population. Many of these infectious agents are not only endemic threats in different parts of the globe, but are also considered to have the potential of being used as bioterrorism agents. AREAS COVERED: this review focuses on inhibitors that are currently in use in the research community against specific emerging infectious agents and those that have bioterrorism potential. The paper provides information about the availability of FDA approved drugs, whenever applicable, and insights into the specific aspect of the agent life cycle that is affected by drug treatment, when known. EXPERT OPINION: the key message that is conveyed in this review is that a combination of pathogen and host-based inhibitors may have to be used for successful control of viral replication to limit the development of drug resistance.     

Risk assessment and the credibility of federal regulatory policy: an FDA perspective

FDA's fundamental goals are to protect and promote the public health, using the best possible science and the law. The evolution of food safety policy toward potential carcinogens reflects a conscious decision by the agency and Administration to use risk assessment in carrying out these goals. Examples include FDA policies toward assessing the safety of animal drug residues, setting specifications for constituents of food and color additives, and most recently, a common sense de minimis interpretation of the "Delaney clause." While committed to risk assessment as a useful tool, FDA acknowledges that judgments must be made on less than perfect data. In addition, recent history shows that there may be a serious "credibility gap" in public acceptance of regulatory toxicology. To ensure that there is an adequate science base for regulatory decisions, the challenge is twofold: First, the data necessary for sound safety evaluations in individual cases must be developed, based on current knowledge; and, second, the validity of assumptions underlying risk assessment should be tested and refined and scientific consensus achieved. Otherwise, risk management policy will rely on assessments based on extremely conservative assumptions, tending to overestimate risk. Risk assessment assumptions must also be better communicated to policymakers and the public. If these challenges are successfully addressed, public confidence in marketed products, and in science-based regulatory policy, will be enhanced.     

Developing early formulations: practice and perspective

Early formulations are prepared mostly for drug compounds at both discovery and preclinical stages and are used to animals via various routes such as oral and intravenous dosing. They serve the purpose of evaluating these compounds on a broad range of pharmaceutical interests, notably pharmacology (activity/efficacy), pharmacokinetics (PK), and toxicology. It is estimated that approx. 40% of all drug compounds discovered have certain delivery limitations due to poor solubility or poor bioavailability. This brings tremendous challenges to the scientists working in the field of early formulations. This study intends to cover a broad spectrum of early formulations including basic aspect and development aspect. On basic aspect, it summarized early formulation study purpose, objectives, dosing route, animal species, etc. It then evaluated a variety of dosage forms and solubility enhancement approaches including various solutions, suspensions, lipid-based formulations, solid dispersions, etc. On development aspect, this study broadly reviewed literatures and current practice in the field, the issues and challenges. It offered authors' own approaches and strategies including general development schemes for oral and for i.v., recommended excipient use range for oral and for i.v., experimental procedures for vitro serial dilution method, for kinetic solubility, etc. The study also discussed a number of case analyses and emphasized scientific rationales and experimental approaches in each of them. The study concluded with authors' summary and some comments on early formulation practice, thoughts and perspectives on its future trend. The study is a mixture of literature review and investigational research. It provides many useful information, practical procedures, and recommendations. It is expected that the study will fill the void of literature of such kind, and provide direct benefit to everyday practitioners in the field.     

Dendrimers and antivirals: a review

In response to the need for antiviral agents, dendrimers, hyper-branched, well-defined, and chemically versatile molecules, have been found to have a number of potential uses. How they are used is based on knowledge of 1) how a virus interacts with its target cells, 2) how it replicates, and 3) which viral components are recognized by the immune response of the host. Many viral-host cell interactions are initiated by viral proteins binding to specific cell surface carbohydrates. Dendrimers offer an efficient means of presenting multiple ligands, or sites of contact, on a single molecule. Derivatized with carbohydrate residues, the multivalent ligands have been shown to inhibit viral binding. Dendrimers derivatized with peptides or anionic groups have also been found to inhibit infection. The availability of a number of different types of dendrimers permits synthesis of potential inhibitors of viral binding to be tailored to meet the dimensions needed for optimum adherence by the virus. Future directions should see increased studies of the use of dendrimers as carriers of 1) multiple indicators on a viral probe to increase diagnostic sensitivity, 2) multiple peptides for use as immunogens or as inhibitors of viral binding, and 3) inhibitors of viral enzymes. While the field of dendrimer chemistry is relatively young, promising results indicate that dendrimers may provide the scaffolding needed for development of effective antivirals.     

Design and development of antivirals and intervention strategies against human herpesviruses using high-throughput approach

Introduction: Although a number of antiviral agents are licensed for treatment of some human herpesvirus (HHV) infections, effective antiviral therapy is not available for all HHVs. Additional complications are associated with approved drugs, such as toxicity and side effects, and rise in drug-resistant strains is a driving force for new drug development. Success in HHV vaccine development is limited with only vaccines against varicella-zoster virus currently in use in the clinic. In vitro, in vivo and in silico high-throughput (HTP) approaches and innovative microfluidic systems will provide novel technologies to efficiently identify and evaluate new targets and antiherpetic compounds. Coupled with HTP strategies for manipulation of herpesvirus viral genomes, these strategies will greatly accelerate the development of future antivirals as well as candidate vaccine intervention strategies.

Areas covered: The authors provide a brief overview of the herpesvirus family and associated diseases. Further, the authors discuss the approved and investigational antiherpetic drugs in the context of current HTP technologies.

Expert opinion: HTP technology such as microfluidic systems is crucial for the identification and validation of novel drug targets and next-generation antivirals. Current drug development is limited by the unavailability of HTP preclinical model systems. Specific advancement in the development of HTP animal-specific technology, applied in parallel, allows a more rapid evaluation of drugs at the preclinical stage. The advancement of HTP combinatorial drug therapy, especially ‘Organ-on-a-Chip’ approaches, will aid in the evaluation of future antiviral compounds and intervention strategies.     

US FDA perspective on challenges in co-developing in vitro companion diagnostics and targeted cancer therapeutics

Recent advances in cancer therapy are based on agents that specifically target the products of the genes mutated in cancer cells. Development of companion diagnostic tests for these agents can simplify the drug-discovery process, make clinical trials more efficient and informative, and be used to individualize the therapy of cancer patients. Companion diagnostic development has many challenges. Examples include the reluctance of drug companies to restrict the use of their drugs through biomarker tests, difficulties of developing companion diagnostics from discovery to clinical validation, and the regulatory challenges in developing effective mechanisms to synchronize reviews of therapeutics with diagnostic devices used to personalize treatment. This article addresses the various challenges in developing companion diagnostics along with the US FDA's approach to regulation of companion diagnostic devices.     

A fresh perspective on comparing the FDA and the CHMP/EMA: approval of antineoplastic tyrosine kinase inhibitors

We compared and determined the reasons for any differences in the review and approval times of tyrosine kinase inhibitors (TKIs) by the US Food and Drug Administration (FDA) and the European EMA/CHMP. Applications for these novel cancer drugs were submitted to them within a mean of 31.2 days of each other, providing a fair basis for comparison. The FDA had granted priority review to 12 TKIs but the EMA/CHMP did not grant the equivalent accelerated assessment to any. The FDA granted accelerated approvals to six (38%) and CHMP granted (the equivalent) conditional approvals to four (29%) of these agents. On average, the review and approval times were 205.3 days in the US compared with 409.6 days in the European Union (EU). The active review times, however, were comparable (225.4 days in the EU and 205.3 days in the US). Since oncology drug development lasts about 7 years, the 20 days difference in review times between the two agencies is inconsequential. Clock stops during review and the time required to issue an approval had added the extra 184.2 days to review time in the EU. We suggest possible solutions to expedite the EU review and approval processes. However, post-marketing emergence of adverse efficacy and safety data on gefitinib and lapatinib, respectively, indicate potential risks of expedited approvals. We challenge the widely prevalent myth that early approval translates into early access or beneficial impact on public health. Both the agencies collaborate closely but conduct independent assessments and make decisions based on distinct legislation, procedures, precedents and societal expectations.     

An FDA perspective on the nonclinical use of the X-Omics technologies and the safety of new drugs

Work in the field "omics" (toxicogenomics, proteomics, and metabolomics) has exploded. It is hoped that 'omics' could be a tool for evaluation of general toxicology, reproductive toxicology, the carcinogenicity potential of pharmaceuticals and several other types of toxicity, eventually replacing the use of animals. Although much progress has been made in the standardization of procedures, challenges remain for evaluation of pharmaceuticals for regulatory purposes, because of off-target toxicologic effects, as well as issues of interpretation and the large number of biologic variables that can affect results. Such variables include species/strain, genetic variations, diet, age, dose, duration, and weight of animals. These variables also confound database compilations of expression profiles. The most promising use in the near future would be to clarify pathways for the various types of toxicity and carcinogenicity and get biomarkers for these pathways, to help assess relevance of nonclinical findings to humans.     

Biomarkers to improve the benefit/risk balance for approved therapeutics: a US FDA perspective on personalized medicine

This article highlights a current US FDA perspective concerning the use of biomarker-based diagnostics for personalized medicine. Specifically, current biomarkers that have application for improving the benefit/risk profile of already approved drugs are discussed. The success of biomarkers for use in personalized medicine depends on many factors, including proper evaluation of the usefulness of the biomarker for assessing the event of interest, and the safety and effectiveness of the diagnostic device used to measure the biomarker, which includes appropriate analytical and clinical validation. These points along with the many regulatory concerns regarding co-labeling of drugs and devices and future aspects, such as co-development, will be discussed in this regulatory science focus.     

The use of one-sided tests in drug trials: an FDA advisory committee member's perspective.

The use of one-sided or two-sided tests in drug trials to evaluate new compounds is considered. For drugs that may be tested against placebos, with two positive trials required (as in the United States), it is argued that from both a regulatory and pharmaceutical industry perspective, one-sided tests at the 0.05 significance level are appropriate. In situations where only one trial against placebo may be done (for example, survival trials), one-sided tests at the 0.025 level are appropriate in many cases. For active control trials it is argued that two-sided tests are usually appropriate.     

Bioactive natural compounds against human coronaviruses: a review and perspective

Coronaviruses (CoVs), a family of enveloped positive-sense RNA viruses, are characterized by club-like spikes that project from their surface, unusually large RNA genome, and unique replication capability. CoVs are known to cause various potentially lethal human respiratory infectious diseases, such as severe acute respiratory syndrome (SARS), Middle East respiratory syndrome (MERS), and the very recent coronavirus disease 2019 (COVID-19) outbreak. Unfortunately, neither drug nor vaccine has yet been approved to date to prevent and treat these diseases caused by CoVs. Therefore, effective prevention and treatment medications against human coronavirus are in urgent need. In the past decades, many natural compounds have been reported to possess multiple biological activities, including antiviral properties. In this article, we provided a comprehensive review on the natural compounds that interfere with the life cycles of SARS and MERS, and discussed their potential use for the treatment of COVID-19.     

Arenaviruses and hantaviruses: from epidemiology and genomics to antivirals

The arenaviruses and hantaviruses are segmented genome RNA viruses that are hosted by rodents. Due to their association with rodents, they are globally widespread and can infect humans via direct or indirect routes of transmission, causing considerable human morbidity and mortality. Nevertheless, despite their obvious and emerging importance as pathogens, there are currently no effective antiviral drugs (except ribavirin which proved effective against Lassa virus) with which to treat humans infected by any of these viruses. The EU-funded VIZIER project (Comparative Structural Genomics of Viral Enzymes Involved in Replication) was instigated with an ultimate view of contributing to the development of antiviral therapies for RNA viruses, including the arenaviruses and bunyaviruses. This review highlights some of the major features of the arenaviruses and hantaviruses that have been investigated during recent years. After describing their classification and epidemiology, we review progress in understanding the genomics as well as the structure and function of replicative enzymes achieved under the VIZIER program and the development of new disease control strategies.     

In vitro efficacy of approved and experimental antivirals against novel genotype 3 hepatitis C virus subgenomic replicons

Infection with genotype 3 hepatitis C virus (HCV) is common throughout the world, however no direct-acting antiviral (DAA) has been approved to treat this genotype. We therefore attempted to develop novel genotype 3 replicons to facilitate the discovery and development of new HCV therapies. A novel Huh-7-derived cell line 1C but not Lunet cells enabled the selection of a few stable colonies of a genotype 3a subgenomic replicon (strain S52). Genotypic analysis revealed a mutation of P89L in the viral NS3 protease domain, which was confirmed to enhance genotype 3a RNA replication and enable the establishment of highly replicating luciferase-encoding replicons. Secondary adaptive mutations that further enhanced RNA replication were identified in the viral NS3 and NS4A proteins. In addition, cell lines that were cured of genotype 3a replicons demonstrated higher permissiveness specifically to genotype 3a HCV replication. These novel replicons and cell lines were then used to study the activity of approved and experimental HCV inhibitors. NS3 protease and non-nucleoside NS5B polymerase inhibitors often demonstrated substantially less antiviral activity against genotype 3a compared to genotype 1b. In contrast, nucleoside analog NS5B inhibitors and host-targeting HCV inhibitors showed comparable antiviral activity between genotypes 3a and 1b. Overall, the establishment of this novel genotype 3a replicon system, in conjunction with those derived from other genotypes, will aid the development of treatment regimens for all genotypes of HCV.     

Vaporization,bioactive formulations and a marine natural product: different perspectives on antivirals

This note examines three aspects of antivirals as they can potentially relate to the treatment of COVID-19; (i) the use of vaporization for the delivery of antivirals, with the bulk constituents having mild antiviral efficacy, (ii) a counter intuitive approach to formulation that, is in part, based on delivering multiple species that fall into three categories; building blocks for the virus to accelerate replication; an energy source for the infected cell to boast its immune response; species that antagonize or provide toxicity to the virus, (iii) the application of a marine natural product extract with several species, as opposed to a focusing on a single molecule as the anti-viral agent.

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Thoughts on carcinogenesis testing: the FDA today

Prevention of human cancer in the future will depend on using the results of epidemiologic and animal studies and strategies to minimize exposure. Changes are occurring in the area of animal testing and research that potentially represent significant steps toward reducing our dependence on the traditional 2-year bioassay as our primary tool for identification of chemical carcinogens and management of risk. Efforts to prevent cancer would be enhanced by more attention to describing modes of action so that the development of tumors would not be the only basis for predicting carcinogenic potential. These markers might also serve for early detection of cancer at a stage more amenable to treatment. What carcinogens do we want to detect through animal tests in the future? Whether the goal is to identify weak or potent carcinogens, or both, there will still be a need for 2-year bioassays, but hopefully for confirmatory rather than screening purposes.     

Enterovirus A71 antivirals: Past,present, and future

Enterovirus A71 (EV-A71) is a significant human pathogen, especially in children. EV-A71 infection is one of the leading causes of hand, foot, and mouth diseases (HFMD), and can lead to neurological complications such as acute flaccid myelitis (AFM) in severe cases. Although three EV-A71 vaccines are available in China, they are not broadly protective and have reduced efficacy against emerging strains. There is currently no approved antiviral for EV-A71. Significant progress has been made in developing antivirals against EV-A71 by targeting both viral proteins and host factors. However, viral capsid inhibitors and protease inhibitors failed in clinical trials of human rhinovirus infection due to limited efficacy or side effects. This review discusses major discoveries in EV-A71 antiviral development, analyzes the advantages and limitations of each drug target, and highlights the knowledge gaps that need to be addressed to advance the field forward.