John Sonnier

John Sonnier

Managing Director, Head of Life Sciences

Chicago skyline

About John

John Sonnier is a managing director for William Blair based in the firm’s Chicago office. He originally joined William Blair in 2005. Prior to William Blair, he worked for Prudential, Vector Securities International, Baxter International, and Johnson & Johnson.

Board Membership

Lake County Community Foundation

Notable Transactions


Follow-on Offering


Follow-on Offering




Follow-on Offering


Follow-on Offering


Follow-On Offering


Follow-on Offering


Follow-on Offering


Initial Public Offering


Initial Public Offering


Initial Public Offering


Follow-on Offering

Rigorous pursuit of your success. Every transaction. Every time.

Our investment bankers are 100 percent committed to your organization’s sustained success. By drawing on our deep industry and product experience as well as our dedicated global resources, we provide advisory and financing services that allow you to capitalize on today’s opportunities and anticipate tomorrow’s challenges.

More about investment banking at William Blair
Aerial view of highway interchange at night


The rapid and cost-effective development of innovative therapeutics and treatments is critical not just to public health, but to the functioning of society and economic activity. Leading drug developers, as well as their partners across the research, development, and manufacturing value chain, count on William Blair’s deep expertise in biopharma’s capital-raising and deal-making landscape.

More about our biopharma expertise
Petri dish

Medical Technology

William Blair’s Medical Technology team works with many of the world’s most innovative medical technology companies to help transform their growth trajectory through capital access and M&A partnerships. By combining deep expertise in the mega trends driving life science and medical product innovation and our knowledge of the regulatory and reimbursement environment, we deliver trusted advice and outstanding execution for market-leading companies and financial sponsors.

Learn more about our medical technology expertise
Technician and a microscope

About William Blair

William Blair is a premier global boutique with expertise in investment banking, investment management, and private wealth management. We provide advisory services, strategies, and solutions to meet our clients’ evolving needs. As an independent and employee-owned firm, together with our strategic partners, we operate in more than 20 offices worldwide.*

William Blair Emblem

Year William Blair was founded

Icon of three people

Employees worldwide

Dollar sign icon
142 billion+

Client assets

Handshake icon
89 Years

Independent and employee-owned

Globe icon

Offices worldwide

Checklist icon

Companies under coverage

As of March 31, 2024
*Includes strategic partnerships with Allier Capital, BDA Partners, and Poalim Capital Markets.

More about William Blair affiliated entities

This content is for informational and educational purposes only and not intended as investment advice or a recommendation to buy or sell any security. Investment advice and recommendations can be provided only after careful consideration of an investor's objectives, guidelines, and restrictions.

Copyright © 2022 William Blair & Company, L.L.C. | Privacy Terms

Are you sure you want to leave?

Information contained on the internet is not subject to William Blair & Company's control or review, and may not be accurate.

For disclosure information, please visit