Walter founded WG&A in 1998 focused solely on early-stage life science companies. Since 2002, the firm has raised $238M in seed and Series A round capital for early stage lifescience companies and returned, to date, $640M to investors in those rounds. An experienced entrepreneur and “hands-on” operating executive, Walter has founded and grown to profitability a series of successful operating businesses. Earlier in his career he worked as a strategic consultant at Bain & Company in a variety of industries in including healthcare. Walter holds an BA from Yale University, an MA from Oxford University and an MBA from Harvard Business School. .

Stewart is a board-certified surgeon (2 years of General Surgery followed by 3 years of Urology, certified in both the US and Canada.) He completed a fellowship in microsurgery, and is an active fellow of the American College of Surgeons [FACS]. Stewart has designed, conducted, read out, and published studies in over 1,400 patients across a range of surgical procedures for a Cox-2 pain product while CMO at Baudax Bio. He has built Medical Affairs teams focused on orthopedics, general surgery, and anesthesia as Clinical Director at GlaxoSmithKline (GSK). Prior to that, he was Director of Clinical Pharmacology at GSK. He has extensive experience taking complex programs through first-in-human trials and on to approval, along with completing post-approval commitments. Prior to his work in industry, Dr. McCallum was Assistant Professor of Urology at Stanford University.

Greg is a seasoned life sciences executive with over 20 years of global leadership experience in clinical development, operations, and commercialization across the pharmaceutical, biotech, and medical device industries. He has successfully led and advised clinical programs resulting in the launch of therapies in oncology, renal disease, pain management, and wound care.

Greg has overseen more than 200 clinical projects and contributed to over 25 global regulatory approvals. His expertise spans early- and late-phase development, clinical technology strategy, and operational execution. He is recognized for driving innovation and efficiency in complex clinical environments.

As founder and CEO of a U.S.-based Clinical Research Organization, Greg built and scaled the company into a full-service provider with strong client relationships and sustained growth, culminating in a successful acquisition. He also led the development of proprietary clinical trial platform that was later acquired.

Earlier in his career, Greg held senior Clinical Affairs roles at Baxter Healthcare and Convatec, where he played a key role in the development and commercialization of advanced dialysis, wound, and ostomy care products. Greg brings deep strategic insight, operational excellence, and a proven track record of success.