Jay R. Luly, Ph.D., President, Chief Executive Officer and Director


Dr. Luly joined Enanta in July 2003. Prior to joining Enanta, Dr. Luly was an Entrepreneur in Residence at Oxford Bioscience Partners. Before joining Oxford in March 2002, Dr. Luly held the positions of Senior Vice President, Research and Development Operations and Senior Vice President, Discovery Strategy and Operations at Millennium Pharmaceuticals following Millennium’s merger with LeukoSite, Inc., where he had served as Senior Vice President, Drug Discovery and Preclinical Development. Prior to joining LeukoSite, he held a number of senior drug discovery positions at Abbott Laboratories from 1983 to 1997. Dr. Luly received a B.S. from the University of Illinois, Urbana/Champaign and a Ph.D. in synthetic organic chemistry from the University of California, Berkeley.

Nathalie Adda, M.D., Senior Vice President and Chief Medical Officer


Dr. Adda joined Enanta in June 2015. Dr. Adda is a specialist in infectious disease and has more than 20 years of experience in the pharmaceutical industry in all phases of global clinical research and development and commercialization. Most recently, Dr. Adda was Chief Medical Officer, VP Clinical Development, Medical and Regulatory Affairs at Transgene SA, where she led the Oncology and Infectious Disease programs since 2012. From 2006 to 2012, she was Senior Medical Director and the medical lead for the Incivek® (telaprevir) Clinical Program at Vertex Pharmaceuticals Inc., where she designed the phase 2 and Phase 3 programs, and led the medical team in its successful marketing applications and registration in the USA, Canada, and, Asia. Earlier in her career, she held medical and research positions at Gilead, Triangle Pharmaceuticals and Boehringer Ingelheim, where she worked on programs for infectious diseases such as human immunodeficiency virus, hepatitis B virus and hepatitis C virus.

Dr. Adda is a graduate of the University of Paris, where she received a Doctorate in Medicine, as well as a Master’s Degree in Biostatistics, and where she did post-graduate work in infectious diseases.

Nathaniel S. Gardiner, J.D., Senior Vice President and General Counsel


Mr. Gardiner joined Enanta in 2014. Previously he was a corporate and securities law partner in private practice for 25 years, starting at Palmer & Dodge LLP and continuing through its merger into Edwards Angell Palmer & Dodge LLP, which then became Edwards Wildman Palmer LLP. Since 2008 Mr. Gardiner had been co-chair of the firm’s Life Sciences Group, and before that he was co-chair of the Business Law Department. In his private practice, Mr. Gardiner was Enanta’s outside counsel and Secretary since it was founded, and he led its IPO legal team. He also served for 15 years as a Trustee of Joslin Diabetes Center, Inc. in Boston, where he was a member of the Executive Committee and Chair of the Compensation Committee until 2015. Mr. Gardiner received his A.B. from Harvard College and his J.D. from the University of Virginia School of Law.

Tara L. Kieffer, Ph.D. , Senior Vice President, New Product Strategy and Development


Tara L. Kieffer, Ph.D. joined Enanta in December 2020. Prior to Enanta, Dr. Kieffer was at Vertex Pharmaceuticals where she held roles of increasing responsibility. Most recently, she was Vice President, External Innovation, Business Development where she was responsible for assessing the external innovation landscape and leading projects aimed at identifying in-licensing and acquisition opportunities. Prior to that, she was Vice President, Integrated Program Management, after being Senior Director, Chief of Staff to the Chief Medical Officer. Dr. Kieffer also held the positions of Director, Clinical Biomarkers and Head of Clinical Virology where she built and led a team responsible for laboratory and clinical research studies to understand the development of antiviral drug resistance to Hepatitis C and influenza viruses. Before joining Vertex, Dr. Kieffer was at Johns Hopkins University School of Medicine in the Department of Molecular Biology and Genetics, where her research studies focused on ongoing replication in patients with well-suppressed Human Immunodeficiency Virus infection.

Dr. Kieffer graduated summa cum laude from Colgate University with a B.A. in Molecular Biology. She holds a Ph.D. in Immunology from Johns Hopkins University School of Medicine. She is co-author on more than 50 publications and an inventor on multiple patents involving treatments for Hepatitis C.

Brendan Luu, Senior Vice President, Business Development


Mr. Luu joined Enanta in January 2021. Prior to Enanta, he was at Merck KGaA, where he held roles of increasing responsibility. Most recently, he was Vice President and Global Head of Oncology Business Development, responsible for setting the franchise business development strategy and was accountable for its execution, including the completion of several major transactions across all stages of drug development in line with the company’s R&D goals. Previously, Mr. Luu was Senior Director and Global Head of Business Development, Strategic Initiatives, where he led the strategy and partnering efforts to secure external financing for Merck KGaA’s late-stage pipeline. Before that, he was Director, Global Licensing and Business Development, Neurology and Immunology, where he led in/out licensing transactions for preclinical and clinical-stage assets to support R&D in neurodegenerative diseases. Previously, he was an Associate Director of Regional Business Development, General Medicines responsible for growing the product portfolio in the Asia-Pacific region. Earlier in his career, he held various roles in the chemicals industry with BASF Corporation and in telecommunications with Tyco International, working in engineering, sales and marketing.

Mr. Luu graduated magna cum laude from Drexel University with a B.S. in Chemical Engineering and Biology. He holds an M.B.A from the New York University Stern School of Business.

Paul J. Mellett, Senior Vice President, Finance & Administration and Chief Financial Officer


Mr. Mellett joined Enanta in September 2003. Prior to joining Enanta, he held the position of Senior Vice President and Chief Financial Officer of Essential Therapeutics. Previously, Mr. Mellett was the Chief Financial Officer and Vice President of Administration at GelTex Pharmaceuticals, Inc., a publicly held biotechnology company that was acquired by Genzyme Corporation in December 2000. Mr. Mellett also served as Chief Financial Officer of Marshall Contractors, a construction management firm specializing in the pharmaceutical, biotechnology and semiconductor industries, which was acquired by Fluor Corporation. Earlier in his career, Mr. Mellett was employed with Deloitte & Touche LLP, a public accounting firm, where he served as Audit Partner. Mr. Mellett received a B.S. in Business Administration from Boston College.

Yat Sun Or, Ph.D., Senior Vice President, Research & Development, and Chief Scientific Officer


Dr. Or joined Enanta in November 1999 and led its preclinical and early clinical development efforts, including the team responsible for achieving all milestones in the collaboration with AbbVie to develop hepatitis C treatments. Dr. Or and his team discovered glecaprevir, the protease inhibitor in AbbVie’s successful combination treatment for hepatitis C virus currently marketed as MAVYRET®. He is leading Enanta’s ongoing research on antivirals for hepatitis B virus, respiratory syncytial virus, human metapneumovirus and SARS-CoV-2, as well as the non-viral liver disease nonalcoholic steatohepatitis. Dr. Or’s team also worked on the earlier protease inhibitor in AbbVie’s VIEKIRA PAK® treatment for hepatitis C virus, and previously developed antibacterials for methicillin-resistant staphylococcus aureus (MRSA). Further, Dr. Or has managed Enanta’s research and development collaborations with Shionogi, Abbvie and Novartis.

Prior to Enanta, Dr. Or was a senior project leader and research fellow of antibacterial research at Abbott Laboratories from 1985 to 1999. Prior to Abbott, he was a member of the cardiovascular drug discovery team at Schering-Plough.

Dr. Or received his Ph.D. in Organic Chemistry from the University of Chicago and completed Postdoctoral Fellowships at Ohio State University and Indiana University. He has co-authored more than 100 publications and is listed as a co-inventor on over 260 filed U.S. patent applications.