William (Bill) D. Klaren, Ph.D., DABT
Senior Scientist II


Phone(262) 806-3509
Address31 College Place
Suite B118
Asheville, NC 28801




Professional Profile

Dr. William (Bill) Klaren is a board-certified toxicologist in ToxStrategies’ Health Practices Division. With a Ph.D. in Human Toxicology and more than 6 years of experience across both academia and industry, he brings broad toxicological, risk assessment, and project management expertise to the consulting environment. Dr. Klaren has experience in systematic review and distilling essential concepts from published literature. Furthermore, he has expertise on the reliability and relevance of publications to advance prioritization initiatives. He has also worked with mechanistic and in vivo data sets for subsequent incorporation into mode-of-action or adverse-outcome pathway frameworks, with a particular focus on endocrine disruption (ED).

Dr. Klaren has expertise with new-approach methods, highlighted by research into alternative approaches to animal testing by developing and qualifying high-throughput in vitro assays utilizing organotypic cultures. By multiplexing the assays, many endpoints could be leveraged to generate bioactivity profiles for test substances. Such endpoints ranged from transcriptomics to cellular responses and morphology data. Given the large amounts of data coming from the high-throughout transcriptomics and high-content imaging, extensive data processing was necessary. This approach was used for a wide variety of petroleum distillates and the prototypical UVCB (Unknown or Variable composition, Complex, or Biological) substances, producing a case study on the utility of such a framework in grouping similar biologically active substances. Dr. Klaren also conducted research into the degree of concordance between available in vitro assay data and DrugMatrix transcriptomic data, noting that key variables, such as physiochemical properties, can have a great impact on the magnitude of agreement between these orthogonal data sources. This work primarily demonstrated that context is key when understanding and using in vitro assay data.

Dr. Klaren has collaborated with academicians in the development of predictive models for ED potential. This work encompassed all the EATS (estrogen, androgen, thyroid, and steroidogenesis) modalities involving thorough evaluations of existing sources of endocrine-related data—notably, the ToxCast and Tox21 assay data. This work allowed for a preliminary evaluation of ED potential for data-poor chemicals found in consumer goods. Dr. Klaren has conducted ED potential assessments following current guidance—in particular, the ECHA/EFSA ED guidance, and has also conducted screening-level ED assessments on a variety of chemicals and components of consumer goods. He has advised decision makers on the complexity of endocrine disruption toxicity and relevant regulations in pursuit of business goals and strategic decision making.

Dr. Klaren has performed numerous risk assessments on consumer products, covering pest control, cosmetics, and hair-care products. He has also reviewed chemical portfolios and overseen Good Laboratory Practice (GLP) acute toxicity testing. Additionally, he has supported exposure studies to refine consumer goods risk assessments and has acquired broad expertise in the inhalation exposure that results from consumer product use. This experience, coupled with an in-depth knowledge of regulations related to biocidal products, allowed for the support of registration for multiple pest control products in the US and EU. In conjunction with this support, Dr. Klaren has served on several task forces instituted to expand the robust safety profiles, through ongoing toxicity testing and governmental registrations, of the pyrethroid class of insecticides.

Dr. Klaren has a strong record of communication through publications and presentations. He is active in the Society of Toxicology, supports younger career toxicologists via guest lecturing, and has received multiple awards from employers and in academia. Additionally, Dr. Klaren became a Diplomate of the American Board of Toxicology in the fall of 2021.