[1] She previously worked with Merck Research Laboratories (MRL), joining the company in 1979 as a biochemist and retiring from the position of senior vice president and franchise head, diabetes and endocrinology in 2013.

[2][11][12] In October, 2021, Thornberry assumed the post of Chair, R&D while also maintaining her seat on the company’s Board of Directors (succeeded by colleague from Merck, Jay Galeota, who became CEO of Kallyope.

[16] Thornberry was involved in early enzymology research on Lisinopril, an angiotensin converting enzyme (ACE) inhibitor used for the treatment of hypertension.

[3][20] Thornberry also developed a novel method for analyzing protease specificities in combinatorial libraries of positional scanning substrates.

[22][23] Beginning in 1999, Thornberry led the biology team for the development of Januvia™ (generic: sitagliptin), a once-a-day oral medication that inhibits the dipeptidyl peptidase-4 (DPP-4) enzyme and improves glucose tolerance to treat Type 2 diabetes.

"[27]At Kallyope Inc., drug discovery focuses on the study of hormonal and neural communication between the gut and the brain to better understand and improve health and nutrition.

She is also on the board of the New York Genome Center, and a member of the NYC Mayor’s Life Science Advisory Council.