SOT FDA Colloquia

Leigh Ann Burns Naas, PhD, DABT, ATS, ERT, Co-Chair

Dr. Leigh Ann Burns Naas is an independent consultant and President of Magnolia Toxicology Consulting, LLC, providing advice in the areas of nonclinical safety and strategic planning for drug development. The experience she brings stems from a 25+ year career in product development and safety, 20 of the most recent in the biopharmaceutical industry. Throughout her career, her work has focused on strategic aspects and the design of safety programs to support chemical product development and registration, and the clinical development and licensure for small molecules and biotherapeutics, including vaccines.

Prior to launching her company, Leigh Ann was Vice President and Head of Nonclinical Safety & Pathobiology at Gilead Sciences where she oversaw the strategic aspects of nonclinical safety for the company’s diverse research and development portfolio. She also gained extensive experience through her time as a Drug Safety Therapeutic Area Leader for antivirals, global infectious disease, and oncology at Pfizer. Her early experience includes serving as the Immunotoxicology Lab Supervisor in the Toxicology Laboratory and then Group Leader for America’s Product Toxicology at Dow Corning Corporation (now The Dow Chemical Company).

She is a member of the Editorial Board for the International Journal of Toxicology and Journal of Immunotoxicology, and the editor of two volumes of Comprehensive Toxicology, 3rd Edition (Immune and Hematopoietic Systems). She is a Past President of the Society of Toxicology, the American College of Toxicology, and the Academy of Toxicological Sciences, is a former member of the Board of Directors of the American Board of Toxicology, and is also a European Registered Toxicologist (UK). Dr. Burns Naas received her doctorate degree in pharmacology and toxicology from the Medical College of Virginia/VCU in 1992 with an emphasis in immunotoxicology and completed a postdoctoral fellowship in biochemical and molecular immunology at the Mayo Clinic in Rochester, MN.

Patrick Crittenden, PhD, Co-Chair

Dr. Patrick Crittenden has served as a review toxicologist in the Division of Food Contact Substances (DFCS) in the Center for Food Safety and Applied Nutrition of the FDA for the past three years. His extensive background in immunotoxicology includes formal education and professional experience. Dr. Crittenden evaluated the in vivo effects of carbamate and organophosphate pesticides on the rodent immune system during his master’s research, and in vitro assays investigated manganese-induced potentiation of proinflammatory cytokine production in microglia, one of the innate immune cells of the nervous system, during his PhD research.

In three years as a staff toxicologist for a contract research organization, he conducted general toxicology and immunotoxicity studies on behalf of sponsors in the environmental chemical and pharmaceutical industries. As a study director for immunotoxicology studies, he obtained knowledge of GLP study conduct (EPA OPPTS, FDA Redbook, and OECD) and experience evaluating in vitro and in vivo immunotoxicology data. He is currently the DFCS point-of-contact for the Interagency Coordinating Committee on the Validation of Alternative Methods (ICCVAM). One of the alternatives emphasized by ICCVAM is the consideration of in vitro assays in lieu of animal-based toxicology studies. Recently, he participated in the OECD Expert Working Group (EWG) evaluation of a Detailed Review Paper (DRP) of in vitro immunotoxicity testing prepared by the Japanese Center for the Validation of Alternative Methods, including proposed use of a tiered in vitro approach for immunotoxicity testing in lieu of animal-based testing.

Dr. Crittenden is a member of a special project group evaluating alternative methods of developmental immunotoxicity testing sponsored by the Center for Alternatives to Animal Testing at John Hopkins Bloomberg School of Public Health. He is a member of the Society of Toxicology (SOT), the SOT Immunotoxicology Specialty Section, and the FDA Immunotoxicology Interest Group. He has published eight peer-reviewed manuscripts, four as first author.

Hollie Skaggs, PhD, DABT

Dr. Hollie Skaggs is a Diplomate of the American Board of Toxicology and currently Senior Director at Horizon Therapeutics, a global biotherapeutic company, where she oversees all non-clinical safety activities and manages the project toxicology team, in addition to representing non-clinical safety on the extended Research and Development Leadership Team, the Translational Sciences Leadership Team, and the Amgen integration team. Throughout her career, Dr. Skaggs has developed a specialization in immunotoxicology through the management of toxicology activities on immune-oncology, autoimmune, severe inflammatory disease, and rare disease drug discovery and development programs.

Dr. Skaggs received her BS in Zoology from Auburn University and PhD in Toxicology from the University of Kentucky and began her toxicology career as an undergraduate research scientist at Auburn University and Mount Desert Island Biological Laboratory studying the effects of heavy metals on marine invertebrates. She is currently pursuing a Masters of Business Administration, specializing in Strategic Leadership, from the University of Delaware. Prior to joining Horizon, Dr. Skaggs was Director of Toxicology at Incyte Pharmaceuticals and Relay Therapeutics, Principal Scientist at Janssen Pharmaceutica, a pharmaceutical company of Johnson and Johnson; Senior Scientist at Mylan Pharmaceuticals; and Study Director at Covance Laboratories. Dr. Skaggs is a well-respected academic author and has been an invited speaker at multiple scientific meetings including the Society of Toxicology (SOT), Health and Environmental Sciences Institute, and The Minipig Research Forum. She is currently the Vice-President Elect of the SOT Mid-Atlantic Regional Chapter and enjoys mentoring early career toxicologists. She remains passionate about getting safe and efficacious medicines to patients. In her spare time, Dr. Skaggs loves to read, travel, knit, sew, bake, play tennis, and spend time with family and friends. She recently made a terrible decision and is currently training for a marathon.

Kjersti Aagaard, MD, PhD, MScCI

Dr. Kjersti Aagaard is the Henry and Emma Meyer Professor and Endowed Chair in Obstetrics and Gynecology and the Division of Maternal-Fetal Medicine at Baylor College of Medicine and Texas Children’s Hospital. She serves as Vice Chair of Research for Obstetrics and Gynecology, and professor in the Departments of Molecular and Human Genetics, Molecular and Cellular Biology, and Molecular Physiology and Biophysics. She is a Co-director in the Baylor College of Medicine MSTP MD PhD program and involved in medical and graduate student training and mentorship. Clinical and translational research interests parallel her clinical interests: the role of the microbiome in pregnancy and early developmental programming, and the impact of key exposures in pregnancy (such as nutrition, diabetes, maternal high fat diet, smoking, and environmental chemical exposures) on fetal development and later in life disease.

With a PhD in immunology from the Mayo Clinic School of Graduate Medical Education, MD from the University of Minnesota, and master’s in clinical investigation from the University of Utah, a residency in obstetrics and gynecology, and a fellowship in maternal-fetal medicine, she joined the faculty at Texas Children’s Hospital, Baylor College of Medicine. She has been continually funded by NIH since her fellowship, with additional support from major foundations. Dr. Aagaard received the NIH Director’s New Innovator Award (2007), the Michael E. DeBakey Medal for Excellence in Research (2015), and the Nature mid-career Mentor of the Year Award (2018). Elected to the American Society for Clinical Investigators (2019), additional awards include the Society for Reproductive Investigators President’s Award (2020), the Society of Toxicology Translational Research Impact Award (2023), multiple awards from Baylor College of Medicine for her teaching and mentorship, as well as Texas “Top Doc” and “Super Doc” awards annually and the Houston Women’s Magazine “Maximum Mom” Award (2011). She actively contributes to the greater Houston community and runs marathons.

Eliver Ghosn, PhD

Dr. Eliver Ghosn is an Assistant Professor in the Division of Immunology, Departments of Medicine and Pediatrics, at Emory University and a faculty member at the Lowance Center for Human Immunology, Emory Vaccine Center, Center for Immunity and Applied Genomics (Pediatric Research Alliance), and the Bioinformatics Program of the School of Biology at Georgia Institute of Technology. Previously, he was an Instructor in the Department of Genetics at Stanford University and a visiting scientist at the Centre for Stem Cell and Regenerative Medicine at the University of Tokyo in Japan. His laboratory combines high-dimensional flow cytometry and multi-omics single-cell sequencing technologies as a systems immunology approach to study the development and function of tissue-resident immune cells, including B lymphocytes, plasma cells, and macrophages that develop early during prenatal life and persist in tissues throughout adulthood. His previous studies in murine Hematopoietic Stem Cell (HSC) transplantation have challenged the current paradigm on immune system development and established a novel concept of HSC-independent hematopoiesis in prenatal life. His lab also develops new computational tools and technologies integrating multi-omics datasets to study the human immune system. During the pandemic, he pivoted to leverage the lab’s tools and expertise to understand the human immune responses to viral infections, particularly SARS-CoV-2. Dr. Ghosn has been an ad hoc reviewer for national and international funding agencies (NIH, DoD, MRC-UK) and scientific journals in immunology. At Emory, he is an active member of the Graduate Program and teaches the Developmental Immunology course to the Immunology and Molecular Pathogenesis PhD students.

Dr. Ghosn received a Master of Science in Infectious Diseases from the University of São Paulo and a PhD in Immunology/Pharmaceutical Sciences from the University of São Paulo and Stanford University through a joint fellowship program. In addition, he conducted postdoctoral research at Stanford University and the University of Tokyo.

Fenna Sillé, PhD, MS

Dr. Fenna Sillé is an assistant professor of Environmental Health and Engineering at the Johns Hopkins University School of Public Health. As an immunologist with a passion for environmental health, her motto is that a “healthy environment equals healthy people.”

Dr. Sillé’s interest is in studying how environmental exposures change the immune system and increase the long-term risk of respiratory infections and lung cancer. For her research, she combines her expertise in immunotoxicology, microbiology, and functional genomics with metabolomics and exposure epidemiology. Her lab focuses on the sex-specific effect of early-life as well as chronic heavy metal (mixture) exposures on cancer, tuberculosis, influenza, and vaccine efficacy and neurodegeneration—issues that affect millions of people worldwide. In addition, she is investigating sex differences and the COVID-19 associated cytokine storm. As the director of the JHU Exposome Collaborative, Dr. Sillé leads several projects focused on the impact of the cumulative imprint of environmental influences and associated biological responses throughout the lifespan on human health. With her research, she hopes to identify potential targets for intervention to reduce the burden of disease in exposed communities.

Finally, Dr. Sillé is the program coordinator of the Developmental Immunotoxicity (DIT) Program within the JHU Center for Alternatives to Animal Testing. In this role, she leads the International DIT Working Group aiming toward a functional framework of new approach methods for developmental immunotoxicity testing.

Prior to joining Johns Hopkins, she was a postdoctoral fellow at the University of California Berkeley. Dr. Sillé received an MS in immunology and molecular virology from the University of Groningen and as a Boehringer Ingelheim Fonds PhD Fellow, she received her PhD in immunology from the Utrecht University for her work at Brigham and Women’s Hospital in Boston.