IIVS | Study Directors
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Study Directors

Holger P. Behrsing, PhD

Holger P. BehrsingPrincipal Scientist
Principal Investigator, Respiratory Toxicology

Bringing 20 years of experience in in vitro toxicology and expertise in the use of models for pulmonary toxicology, Dr. Behrsing conducts and oversees IIVS laboratory studies, as well as teaches and serves as an industry resource for workshops, webinars, and other educational activities. He serves as the Principal Investigator for the respiratory toxicology workshop series.

Dr. Behrsing attended the University of California at Santa Barbara for his undergraduate degree, majoring in both Biology and German Studies. He completed his Doctoral degree in Pharmacology and Toxicology at University of California Davis. He has spoken at internationally-recognized meetings and has experience with numerous in vitro and ex vivo models systems, with a well-documented background in the use of pulmonary models.

Gertrude-Emilia Costin, PhD, MBA

Gertrude-Emilia CostinSenior Toxicologist
Study Director, Dermal Safety & Efficacy Assessment

Dr. Costin joined IIVS in 2007 and currently oversees a wide range of safety and efficacy commercial studies and research projects using in vitro testing strategies. Her primary area of expertise is in the use of in vitro test methods for the dermal safety assessment of ingredients and final formulations manufactured by cosmetic, personal care or pharmaceutical industry, or products to be registered under US Environmental Protection Agency (EPA) the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA). She also specializes in the use of non-animal methods to address the safety assessment of feminine care products or medical devices registered under the Food and Drug Administration (FDA). In addition, Dr. Costin promotes the use of in vitro efficacy assays to support anti-inflammatory or skin lightening claims of actives or finished products.

Dr. Costin is heavily involved with IIVS educational workshops on non-animal research and in vitro assay systems. In addition, she is the coordinator of the review process for the Alternatives Research Grants, awarded annually by the Alternative Research and Development Fund (ARDF), serves as Board member and Newsletter Editor for the National Capital Area Chapter of Society of Toxicology (NCAC-SOT) and the PanAmerican Society for Pigment Cell Research (PASPCR), and is a Board Council member of the American Society for Cellular and Computational Toxicology (ASCCT).

Dr. Costin received her PhD (Cum laude) from the Institute of Biochemistry of the Romanian Academy, followed by postdoctoral training at the National Cancer Institute, National Institutes of Health (NIH). Prior to joining IIVS, Dr. Costin worked as Senior Research Scientist for Avon Products, Inc. – Global R&D.

Allison Hilberer, MS, DABT

Toxicologist I
Study Director, Photosafety
Allison Hiberer

Allison joined IIVS in 2004 as a Biologist I and is now part of our team of Study Directors. Allison’s primary area of focus is the photosafety programs at IIVS. She also oversees ocular and dermal safety assays, as well as specialized 96-well based assays such as the Short Time Exposure (STE) assay.

Allison is dedicated to our international training workshops, and has provided training on alternative safety metthods in Brazil, China, and Vietnam. She continues to interact with colleagues who are looking to implement or are using in vitro  in their laboratories.

Allison earned her Master’s Degree in Biology from George Mason University in 2011, and received certification as a Diplomate of the American Board of Toxicology (DABT) in 2016.

Nathan Wilt, BS

Nathan Wilte

Toxicologist I
Study Director, Ocular Safety Assessment

Nathan serves as Toxicologist and Study Director for our Ocular Assay Systems, including the EpiOcular™ and BCOP assays.

Nathan joined IIVS in 2001 as a Biologist and quickly learned and worked with multiple assay systems before taking on the role as lab manager, and ultimately Toxicologist and Study Director.

Nathan has contributed to multiple posters and manuscripts for his work. He has also been one of the primary leaders for our international training workshops, contributing to training programs in Brazil, Vietnam, Japan, and China.

Nathan graduated from the University of Maryland with a degree in Biology.

Mario Aragon, PhD

Toxicologist IMario
Study Director, Respiratory Toxicology

Mario joined IIVS in September of 2016 as a Toxicologist I/Study Director, responsible for further development of the Institute’s respiratory toxicology program. In this role, he will help advance in vitro methodologies to better assess the risk of products ranging from consumer goods, chemicals, and tobacco products. Prior to joining IIVS,  Mario worked as a post-doc at Aberdeen Proving Ground (APG) in their chemical weapons defense program.

Mario graduated from Tulane University with a BS in Biomedical Engineering. He received his PhD at the University of New Mexico. His dissertation work involved the cardiovascular and neurological effects of inhaled multiwalled carbon nanotubes.

Mario has published multiple papers and is a member of the Society of Toxicology.

Tinashe Ruwona, PhD, DABT

Toxicologist IITinashe
Study Director

Tinashe recently joined IIVS as a Toxicologist I/Study Director, leading our skin sensitization screening program. With a background in immunology and toxicology, Dr. Ruwona is uniquely qualified to assist our clients in determining the best assays to meet their product development or safety testing needs. Dr. Ruwona can also assist clients in utilizing the appropriate assays for registration for REACH per ECHA’s latest guidance.

Prior to joining IIVS, Tinashe worked as a Research Scientist at SRI International Center for Infectious Disease responsible for antiviral small molecule and vaccine evaluations.

Tinashe graduated from University of Zimbabwe with a degree in Biochemistry, subsequently receiving his PhD in Chemistry at Portland State University for work he did at NIOSH/CDC Morgantown WV. The highlight of his doctoral work was the development of immunological tools to use in diiscoyanate-induced asthma research for which a patent was issued (Patent number US 8,828,667). He was also involved in projects related to alternative methods to animal-based skin sensitization testing: specifically in chemico and in vitro methods for assessment of skin sensitizers. He subsequently did two postdoctoral trainings at the Scripps Research Institute CA and University of Texas-Austin TX in antiviral vaccine and adjuvant development.

Tinashe has published multiple original research papers in toxicology and vaccine sciences. He is a board certified toxicologist with the American Board of Toxicology (DABT) and is a member of the Society of Toxicology.