The Key to Success is in Our People

Our team is comprised of true innovators in the field who are passionate about changing the way we treat GI diseases. 



Mark McKenna

President & CEO, Board Member

Mr. McKenna serves as President, CEO and member of the board of Prometheus Biosciences. Prior to joining Prometheus Biosciences, Mr. McKenna was President & CEO of Salix Pharmaceuticals, a wholly owned subsidiary of Bausch Health Companies.  He joined Salix in March 2016 as the Senior Vice President and General Manager, responsible for the company’s gastrointestinal franchise. During his tenure, Mr. McKenna successfully led the company through a series of key strategic acquisitions, the launch of a number of new products, and delivered strong operating performance, with revenue increasing from $1.2B to $2B. Prior to joining Salix, Mr. McKenna spent more than a decade with Bausch + Lomb, most recently as Senior Vice President/General Manager of its U.S. Vision Care business.  Prior to Bausch + Lomb, Mark held several roles of increasing responsibility at Johnson & Johnson.  Mark holds a B.S. in Marketing from Arizona State University, an MBA from Azusa Pacific University and is a Fellow with the University of Pennsylvania, Wharton School of Business. 


Laurens Kruidenier, PhD

Chief Scientific Officer

Dr. Kruidenier has been active in pre-clinical GI research for over 20 years. Prior to joining Prometheus Biosciences, Laurens was VP of Discovery at Second Genome, where he was responsible for a portfolio of microbiome programs. Previously, Laurens held various positions at GlaxoSmithKline and at Takeda Pharmaceuticals, where he was Head of GI Immunology Research. Laurens received his PhD in Experimental Gastroenterology from Leiden University (The Netherlands), after which he continued his training in GI immunology as a post-doctoral fellow at the University of London. Over the years, his research has resulted in multiple publications in top scientific journals, including Gastroenterology, Nature and Nature Chemical Biology.


Allison Luo, MD

Chief Medical Officer

Dr. Luo has served as Chief Medical Officer of Precision IBD, the predecessor of Prometheus Biosciences since August 2018. Prior to joining Prometheus Biosciences, Dr. Luo was Senior Vice President of Clinical Development for Gastroenterology at Progenity, and Vice President of Clinical Development at Ophthotech where she was responsible for the completion of two Phase 3 studies. Prior to Ophthotech, Dr. Luo was Executive Director at Bristol-Myers Squibb where she was responsible for Inflammatory Bowel Disease and led the Phase 3 program for Orencia (abatacept) and the Phase 2 program for eldelumab (anti-IP10 antibody) for ulcerative colitis and Crohn’s disease. Earlier in her career she was a Medical Director at Abbott Laboratories where she led the regulatory filing of Humira for rheumatoid arthritis in Japan and developed the clinical trial protocols for Humira in ulcerative colitis. Dr. Luo received her Bachelor of Science in Biochemistry and Doctor of Medicine degrees from Northwestern University, followed by a residency in internal medicine at Loyola University, and a fellowship in drug development at Abbott Laboratories (Abbvie).


Lauren Otsuki

Chief Operating Officer

Ms. Otsuki has over 25 years experience in biotechnology product development and commercialization as well as specific expertise in the pre-clinical programs. Over the last 15 years, Ms. Otsuki has founded and managed 6 successful biotech firms including Selexagen Therapeutics, Kanisa Pharmaceuticals, Alastin Skincare, Oncternal Therapeutics, NovaCardia and Dexcom.  In her roles, she has had responsibility for research operations and CMC operations in an environment that utilized many diverse contract research organizations as well as key internal resources. Prior to that Ms. Otsuki held a number of positions (VP of Operations, VP of International, Director of Business Development, Director of Manufacturing, Director of Process Development) at Quidel Corporation, an in vitro diagnostics company.


Keith W. Marshall, PhD

Chief Financial Officer

Mr. Marshall was appointed as our Chief Financial Officer in August 2020.  Prior to joining Prometheus, Mr. Marshall served as Executive Vice President, Chief Operating Officer and Chief Financial Officer of Conatus Pharmaceuticals (Nasdaq: CNAT) since 2017.  Prior to Conatus, he served as Chief Financial Officer and Head of Corporate Development  at Torque Therapeutics (now Repertoire Immune Medicines), a Flagship Pioneering company.  Mr. Marshall also served as Managing Director in Healthcare Investment Banking at GCA Savvian Advisors, Managing Director, Co-founder, and Chief Financial Officer at Montgomery, Marshall Healthcare Partners, and Managing Director of Healthcare Investment Banking at Montgomery & Co. He began his career in investment banking at JP Morgan.  Mr. Marshall holds an MBA from the University of Chicago – Booth School of Business, a Ph.D. in Pharmaceutical Chemistry from the University of California, San Francisco and an A.B. in Biology from Washington University in St. Louis.


Olivier Laurent, PhD

Chief Technology Officer

Dr. Laurent joined Prometheus in September 2020 as Chief Technology Officer.  Dr. Laurent most recently served as Chief Scientific Officer at Intrepida Bio, an immuno-oncology company focused on developing novel antibodies for the treatment of solid tumors.  Prior to this position, Dr. Laurent spent twenty years designing and developing biopharmaceuticals at companies including Sanofi, Bayer HealthCare, Genentech, Pfizer, CovX (acquired by Pfizer in 2008) and Ambrx (acquired by a Chinese consortium in 2015). Dr. Laurent holds numerous patents in the field of biotherapeutics and has contributed to multiple antibody regulatory dossiers. Dr. Laurent holds a Ph.D. in Cell Biology from the University of Grenoble in France and is an alumnus of the École Normale Supérieure de Lyon.


Robert Armstrong, PhD

Sr. Vice President, Development

Dr. Armstrong brings over 25 years’ experience in drug discovery and development to Prometheus Biosciences.  Prior to Prometheus, Dr. Armstrong was Vice President of Research at Retrophin, a commercial stage company focused on expansion of their rare disease pipeline; Chief Scientific Officer at Patara Pharma, a small clinical-stage company focused on inflammatory and fibrotic disease; Ambit Biosciences where he held positions of increasing responsibility over ten years focused on the discovery and preclinical development of kinase inhibitors for cancer and inflammation. Dr. Armstrong’s other positions include those at Chiron Corporation and a career initiating eleven-years at Idun Pharmaceuticals.  He earned his PhD in Neurobiology from SUNY Stony Brook.


Thierry Dervieux, PharmD, PhD

Chief Development Officer, Diagnostics

Dr. Dervieux serves as Chief Development Officer, Diagnostics at Prometheus Biosciences. Previously Dr. Dervieux was at Exagen Diagnostics, a diagnostic company focused on chronic autoimmune diseases, where he served as Chief Scientific Officer, Medical Director.  Prior to joining Exagen, Dr. Dervieux was Vice President of Research and Development at Cypress Bioscience, Inc. and Senior Director Research and Development with Proprius Pharmaceuticals, Inc. Prior to that, he served as Principal Scientist and Director of Research and Development at Prometheus Laboratories. Dr. Dervieux is board certified by the American Board of Clinical Chemistry and holds certificates of qualification as medical laboratory director in the categories of cellular immunology, clinical chemistry, drug monitoring, genetic testing and diagnostic immunology. Dr. Dervieux holds Pharm.D. and Ph.D. degrees from Claude Bernard University in Lyon, France, an inter-university diploma in biostatistics from the University of Pierre and Marie Curie University in Paris, France, and trained at St. Jude Children’s Research Hospital in Memphis, Tennessee.


Mike Walther

Chief Commercial Officer

Mr. Walther serves as Chief Commercial Officer of Prometheus Biosciences. Prior to joining Prometheus Biosciences, Mr. Walther was General Manager at Aries Pharmaceuticals, establishing corporate, pipeline, and portfolio strategies including the commercial launch of the company’s first two products. Mr. Walther’s industry experience spans numerous therapeutic markets, most notably a greater than 25-year focus in pharmaceutical, medical device and diagnostics product development and commercialization in gastroenterology. Prior to joining Aries, Mr. Walther was Vice President, Marketing and Commercial Development at Prometheus Laboratories Inc. where he was responsible for commercializing specialty therapeutics and proprietary diagnostic testing services designed to advance patient-personalized care and previously held roles spanning sales, specialty marketing, and commercial operations at Takeda Pharmaceuticals North America and TAP Pharmaceuticals (a Takeda Pharmaceuticals & Abbott Laboratories Partnership). Mr. Walther received his B.A. in Biology from Ithaca College.


Brian Littlefield

Sr. Vice President, IT

Mr. Littlefield joins Prometheus Biosciences from Exagen Inc., where he served as Senior Vice President, Information Services. At Exagen, he established the IS function and led development and implementation of the information systems that enabled the company’s rapid growth. Prior to Exagen, Brian was with Prometheus Laboratories Inc. for sixteen years, having joined soon after its formation. During that time, he led the development and implementation of specialized systems to support proprietary diagnostic testing services and promotion of specialty therapeutics. Prior to that, Brian worked as a consultant with Deloitte and as the Director of Support Services at Quidel Corporation, a diagnostics manufacturer. Brian holds a B.S. in Biochemistry from Purdue University and an M.B.A. from Pepperdine University.


Vika Brough

Vice President, Finance

Ms. Brough has over fifteen years of experience in public and private accounting roles. She started her career as an auditor at Ernst & Young Assurance practice in San Diego, California.  During the ten years as an auditor, Ms. Brough served many multinational public and private clients in life science, medical devices and technology industries.  After Ernst & Young, Ms. Brough was Head of Finance at Human Longevity, Inc., a genomics-based company in San Diego, where she oversaw financial planning, accounting, treasury and procurement functions. Ms. Brough graduated from the San Diego State University with a Bachelor of Accounting degree.