Dennis joined Domain as a partner in 2007 and became an advisory partner in January 2020. Since joining the Domain team has served as an active investor, a company founder and as the chief executive officer or executive chairman for a number of portfolio investments, resulting in multiple successful exits, initial public offerings, and new drug approvals to address unmet medical needs.

Most recently, Dennis led the growth and sale of Tobira Therapeutics to Allergan in November 2016.  He previously served on the board of Avanir Pharmaceuticals through its acquisition by Otsuka Pharmaceuticals in January 2015, and was a founding board member of RightCare Solutions through its acquisition by Cardinal Health in December 2015. 

Currently, Dennis is the chairman of the board at Syndax Pharmaceuticals and a board member of Exalys Therapeutics.

Earlier in his tenure with Domain, Dennis served as the chief executive officer of Peninsula Pharmaceuticals and, after building the company, led its sale to Johnson & Johnson. In his next role, Dennis was a founder and the chief executive officer of Cerexa and led its sale to Forest Laboratories. Dennis was also a founder and the chief executive officer of Calixa Therapeutics and successfully led the growth and subsequent sale of Calixa to Cubist Pharmaceuticals. Dennis also served as executive chairman of Corthera and after repositioning the company into the cardiovascular space, led the sale of Corthera to Novartis AG.

Prior to Domain, Dennis served as head of the North American Business Unit for Novartis AG and as a member of Novartis' Pharmaceutical Executive Committee and Global Leadership Team. Earlier in his career, Dennis served as vice president and head of the CEC division of Allergan, and as member of Allergan's Global and North American Management Teams. Dennis spent the first ten years of his career with SmithKline Beecham (now GlaxoSmithKline). Dennis received a B.A. from Western Illinois University and an MBA from Pepperdine University, and has completed post-graduate studies at The Wharton School, University of Pennsylvania.