A remarkable aspect of the otherwise terrible covid pandemic we are now experiencing is that medical technologies, both vaccine and therapeutic, had been in development that suddenly became front-line tools in public health efforts to control spread of disease and to treat victims of the infection. The messenger RNA-based vaccines have gone from experimental to game-changer in amazing time. Other therapeutics, such as monoclonal antibodies, have proven useful, although convalescent plasma remains an unproven treatment. Finally, there are drugs that have been developed and were abandoned for various reasons that are being re-examined for activity against coronaviruses. These issues will be discussed, including potential late-developing issues. When nonclinical data become available for products currently being distributed in the US under Emergency Use Authorization, these findings may be compared with clinical experience to assess the risk of expedited product development in the context of a global public health emergency.
Nonclinical development strategies for drugs intended to be administered clinically by the topical route are generally well defined and follow principles outlined in ICH guidelines. There are, however, some additional considerations for topical drug development compared to those administered via the oral route regarding both hazard identification and risk assessment approaches. For topical drug development, the minipig is the standard nonclinical non-rodent model that is more relevant to humans and used to characterize local skin effects because of the overall similarity to human skin anatomy and physiology, while the rodent species is utilized to understand systemic risks and has limited value for understanding local skin effects since rodent skin is anatomically and functionally dissimilar to humans. Risk assessment approaches to clearly define a threshold-based toxicity in skin can be complicated by the absence of validated tools to routinely and accurately model or measure drug concentrations at specific anatomic locations within the skin, and therefore reliance on species with comparable physiology, such as minipig, is required for extrapolations based on applied dose. Exploratory methods exist for measuring drug concentrations in deep dermis of skin but understanding bioavailable concentrations of topically applied drugs closer to the site of application in the viable epidermis, the stratum basale, are not validated. This presentation will discuss challenges associated with the conduct and interpretation of topical carcinogenicity studies in rodents. Emphasis will be on the characterization and positioning of potential risk for drugs that are aneugenic in vitro but not in vivo. The presentation will offer scenarios that involve compounds with existing comprehensive systemic nonclinical data packages including oral rodent carcinogenicity data for which conduct of additional topical carcinogenicity studies in rodents may not be warranted or scientifically justified, especially considering the 3Rs. In addition, exploratory experimental data from EpiDermTM in vitro micronucleus assay will be presented as a hazard identification tool of aneugens and how it compares to the physiologically relevant in vivo minipig model.
Proposed streamlined development approaches for vaccines for SDLT indications and non-oncology SDLT small molecule therapeutics will be presented. For therapeutics, this proposed approach would allow rapid initiation of patient trials and continued treatment beyond the conclusion of the early therapeutic studies regardless of availability of nonclinical safety data, as well as elimination or deferment of nonclinical studies that are not considered essential to supporting patient safety given the high unmet medical need. This approach would allow patients with SDLT conditions earlier and continued access to therapeutics and increase the speed of progression through development. For both therapeutics and vaccines, these approaches would enable an early understanding of potential efficacy and allow patients or participants, in conjunction with their physicians, to make more informed decisions regarding potential initiation and/or continuation of treatment in the context of benefit versus risk considerations. This may additionally increase the SDLT indication therapeutic pipeline, directly beneﬁting patients and reducing the economic and societal burden of SDLT conditions.
The Coronavirus Treatment Acceleration Program (CTAP) has been created by the US Food and Drug Administration during the COVID-19 public health emergency. Guidance documents have been created to facilitate the development of possible therapies and provide streamlined processes for feedback during this pandemic. It is recommended that sponsors seek initial advice under a Pre-Investigational New Drug (pre-IND) meeting request for investigational uses of unapproved drugs as well as for new indications of US FDA–approved drugs; therefore, the Center for Drug Evaluation and Research (CDER) has established a COVID-19 scientific triage team to ensure the completeness and sufficiency of the information provided by sponsors for expedited review by the Agency. Discussion of what constitutes a complete package for IND review, case studies, and related challenges will be presented from a nonclinical perspective.
Computational or in silico toxicology is a broad and emerging field of toxicology. Quantitative Structural Activity Relationship ((Q)SAR) models are increasingly being used to identify hazards, assist in risk assessment, occupational banding assignments, early drug development and, ultimately, as a new test system for de novo evaluation of substances of interest. Acceptance of in silico is evident in the ICH M7 guidance on the assessment and control of DNA reactive (mutagenic) impurities in pharmaceuticals and, coupled with judicious use of read across and expert assessment these methods are increasingly used to supplement predictions from in vitro and in vivo test systems. This talk will aim to explore the basic background and history of computational toxicology, the advantages, and limitations of such tools, the current regulatory environment and acceptance of QSARs and potential future uses and applications.
ゲノムへの化学的修飾であるエピゲノムは、発生・分化やその後の恒常性維持で重要な役割を担うと共に、環境の影響を受けて変化し得ることも知られている。その結果生じたエピゲノム変化が適切でなければ、ゲノム変異と同様に、疾病素因となる可能性が懸念される。加えてエピゲノムは、長期安定して伝わるため、胎児期や新生児期の不適切な環境が成人期の疾患リスクにつながることが懸念されている。このような観点から、DOHaD学説（Developmental Origins of Health and Disease）が提唱され、モデル生物では、intergenerational（母から胎児へ）あるいはtransgenerational（親や祖父母から生殖細胞を介して）なエピゲノム変化の伝搬が示されている。一方ヒトでは、ゲノム多様性と同様にエピゲノム多様性が存在し、臓器毎の差、あるいはepigenetic clock(エピゲノム状態からみた年齢)等が存在するため、真のエピゲノム変化を同定するのは容易ではない。我々は、ヒトの胎児期や新生児期の不適切な環境とエピゲノム変化の関連を検証するために、様々な環境（妊娠中の母体の痩せや肥満、妊娠合併症、早産等）に曝された児の生体試料を収集・解析した。これらの症例ではDNAメチル化変化が観察されたが、必ずしも特定の遺伝子領域に集中するのではなく、ランダムな領域に生じていた。また早産児を経時的に追跡することで、早産児のepigenetic clockを同定できたが、一部の症例では、発生・分化に関わる領域で高頻度に、epigenetic clockが変化しない状態（早産時の未熟な状態が遺残している状態」であった。最近、このようなepigenetic clockを人為的に変化させる試みも報告されており、自験例を含め、ヒトで観察される環境によるエピゲノム変化について概説したい。
医薬品開発では，明らかに変異原性が予測される構造を化合物の探索初期に回避する目的や，化合物開発段階での代謝物・不純物の変異原性評価の一環として（定量的）構造活性相関（[Q]SAR）が用いられることがある．特に不純物については，2006年のEMAガイドライン「Guideline on the Limits of Genotoxic Impurities」および2008年のFDAドラフトガイダンス「Genotoxic and Carcinogenic Impurities in Drug Substances and Products: Recommended Approaches」より(Q)SARの使用が推奨されるようになり，2014年のICH M7ガイドライン発効により国際的にハーモナイズされた．
CRISPR is an acronym for Clustered Regularly Interspaced Short Palindromic Repeat that refers to the unique organization of short, partially palindromic repeated DNA sequences found in the genomes of bacteria and other microorganisms. Since that discovery, CRISPR-Cas9 is recognized as a powerful and flexible functional genomic screening approach that can be employed to provide mechanistic insight and advance or capabilities in toxicology. CRISPR is known for its role in gene editing and Toxicologists most often employ this technology to modulate gene expression in mechanistic investigations. When CRISPR is used as a modality to treat disease, the challenge for toxicologists in characterization of potential on-and off-target toxicities and informing human safety risks that may be caused by these unique treatments are significant. In this introductory segment, various methods and strategies that have evolved since the discovery of this special bacterial defense system will be discussed. The use of CRISPR for investigative work in toxicology, assay development and the challenges CRISPR-based therapies pose for toxicologists will also be reviewed. Last, an overview of some of the current challenges and potential for CRISPR in toxicology will be outlined to bridge to the main talks in the session.
Drug Induced Liver Injury (DILI) is a major contributor to the overall clinical occurrence of acute liver failure (ALF), often leading to early termination of clinical trials, post-marketing drug withdrawals, and the need for liver transplantation, and compound-specific causality is not always clear. Despite a recent pivot toward utilization of in vitro tools for early safety assessment, nonclinical safety studies are still utilized to predict clinical liabilities for new drugs. However, recent advancements in genome editing coupled with network-based approaches in toxicogenomics allow new insight to explore relationships from molecular/cellular level to pathological changes occurring at the organ in preclinical studies. Here, we will focus on recent investigations utilizing an integrated systems biology toolkit consisting of CRISPR/Cas9 and toxicogenomics to reduce uncertainty for both adaptive and progressive changes in the liver during early safety assessment as well as implications for new therapeutics.
The vectors for expressing genes in mammalian cells and animals has not only been a tool for analyzing gene functions, but also has played an important role in industrial and medical applications. In the conventional transgenic technology, the size of DNA that can be introduced into mammalian cells and animals is usually limited to several hundred kb, and to introduce genes or gene clusters having a size exceeding 1 Mb has been impossible. To solve these problems, we used chromosome engineering technology to develop human artificial chromosomes (HAC) and mouse artificial chromosomes (MAC) that can carry large human genes, multiple human genes in a stable manner. On the other hand, the endogenous gene or gene cluster that corresponds to the human GOI(s) being transferred needs to be disrupted to generate a fully humanized animal model. Cre/loxP-mediated deletion of large genomic regions in mouse ESCs has been used to generate gene cluster KO mice. However, this is labor intensive and time consuming because the targeting of two loxP sites and Cre/loxP-mediated chromosomal deletion via Cre expression must be performed in mouse ESCs. To overcome this limitation, genome editing technologies such as ZFN, TALEN, and CRISPR/Cas9 have been utilized to induce large genomic deletions and generate orthologous gene cluster KO animals. These technologies can also be used to further modify previously constructed HACs/MACs carrying human genomic regions. Therefore, the combination of chromosome transfer and genome editing technology is requisite for the efficient production of fully humanized animals. In this symposium, I will introduce new drug discovery tools developed by HAC/MAC and genome editing technology, and further introduce new combined technologies of DNA synthesis and HAC/MAC.
Here I present cases where results of toxicology studies using monkeys were efficiently used for labeling in some regulatory agencies as well as for establishing potential safety biomarkers. All of those examples of labeling are from immune check point inhibition and the resultant immune-related pregnancy risks. These include the cases of CTLA-4 inhibition that exhibits premature births and decreased birth weight (PMDA), PD-1 inhibition mAb that exhibits increased abortion and premature infant death (FDA), and PD-L1 inhibition that exhibits irregular menstrual cycle pattern (EMA), all of which have been observed in ePPND studies of cynomolgus monkeys. Since blockade of PD1/PDL1 (+CTLA-4) pathway may result in a decrease in the efficiency of Tregs and an increase in inflammatory Th17 cells leading to loss of tolerance at the feto maternal interface, the above finding are described as basis of clinical risks in respective labeling. In the course of monkey studies, etc, there are also recent research papers that have raised out Th17/Treg ratio, Th1/Th2 ratio, or NK cell activity in maternal peripheral blood as the potential predictive biomarkers for spontaneous abortion, preterm or preeclampsia. Thus, as far as drug-related immunological pregnancy risks, monkey studies appear to serve as a good translational model to clinical.
医薬品候補化合物によって誘発する痙攣は医薬品開発において重篤な神経毒性の一つであり、臨床試験で痙攣が認められた場合、開発の中止または中断を余儀なくされる。医薬品開発の早期に痙攣毒性の有無やその順位付け、および作用機序を予測することができれば、医薬品開発のコストと時間が大幅に短縮される。前臨床試験における精度の高い痙攣リスク評価法の開発を進めるとともに、実験動物とヒトにおける種差の問題、in vitroからin vivoへの外挿性の問題を解決することが求められる。本シンポジウムでは、培養細胞、オルガノイド、脳スライス、生体脳における痙攣陽性化合物に対する電気活動の変化を最先端の計測技術とともに紹介し、波形データから神経活動の状態を検出する解析法および痙攣リスクを予測するAI解析法を紹介する。また、波形データから作用機序を予測する方法や痙攣前兆状態を予測する方法についても紹介し、in vitro, ex vivo, in vivoで得られたデータの解釈と一致性について議論したい。