Mr. Sean Roosen reports

OSISKO DEVELOPMENT ANNOUNCES NOMINATION OF KEITH MCKAY TO THE BOARD OF DIRECTORS AND PROPOSES NAME CHANGE TO OSISKO GOLD GROUP INC. AT UPCOMING ANNUAL AND SPECIAL MEETING OF SHAREHOLDERS

The upcoming annual and special meeting of holders of common shares of Osisko Development Corp., will be held on June 23, 2026, at 1:30 p.m. Eastern Time at First Canadian Place, 100 King St. W, Suite 3400, Toronto, Ont., M5X 1A4.

Director nomination

As non-executive director, Duncan Middlemiss will not be standing for re-election at the upcoming meeting, the company has nominated Keith McKay for election to the board of directors. The company has also nominated the other incumbent directors for re-election at the meeting.

"On behalf of the board and management team, I would like to thank Duncan for his valuable contributions and dedicated service," said Sean Roosen, chairman and chief executive officer. "We've greatly benefited from his guidance and commitment during his tenure, and we wish him all the best in his future endeavours."

Mr. McKay is a chartered professional accountant with over 45 years of experience in finance and executive leadership, primarily in the mining and natural resources sector. He has extensive expertise in public company reporting, financing, mergers and acquisitions, risk management, and governance. Mr. McKay currently serves as chief financial officer of Dalradian Resources Inc., a position he has held since June, 2010. Mr. McKay has significant board experience, having served as a director and audit committee chair of several publicly listed mining companies, including Osisko Mining Inc., O3 Mining Inc. and Noront Resources Ltd. Over the course of his career, he has held senior executive roles, including chief financial officer of Continental Gold Ltd., Andina Minerals Inc. and Aurelian Resources Inc., as well as senior finance positions with AMEC Canada, Algoma Steel Inc. and Rio Algom Ltd. Mr. McKay obtained his chartered accountant designation in 1981 with Coopers & Lybrand (now PricewaterhouseCoopers LLP) and holds a bachelor of arts degree from Western University.

Proposed name change

At the upcoming meeting, the company is proposing that shareholders consider a change of the company's name to Osisko Gold Group Inc. to better reflect its evolution toward a primary gold and precious metals focused asset base in North America. Management believes the proposed name change is timely as the company enters a new chapter, underpinned by the continued derisking and advancement of its fully permitted Cariboo gold project.

Additional information regarding the meeting, matters to be considered at the meeting and voting can be found in the management information circular of Osisko Development dated May 11, 2026, filed with securities regulators and available on the company's website and on SEDAR+ under Osisko Development's issuer profile.

About Osisko Development Corp.

Osisko Development is a continental North American gold development company focused on past-producing mining camps with district-scale potential. The company's objective is to become an intermediate gold producer through the development of its flagship, fully permitted, 100-per-cent-owned Cariboo gold project, located in central British Columbia, Canada. Its project pipeline is complemented by the Tintic project, located in the historic East Tintic mining district in Utah, a brownfield property with significant exploration potential, extensive historical mining data and access to established infrastructure. Osisko Development is focused on developing long-life mining assets in mining-friendly jurisdictions while maintaining a disciplined approach to capital allocation, development risk management and mineral inventory growth.

We seek Safe Harbor.