Mr. Sean Roosen reports

OSISKO DEVELOPMENT ANNOUNCES AGREEMENT TO DIVEST NON-CORE SAN ANTONIO GOLD PROJECT

Osisko Development Corp. has entered into a securities purchase agreement dated Nov. 21, 2025, with Axo Copper Corp. to sell its 100-per-cent interest in the San Antonio gold project located in the Sonora state, Mexico. Pursuant to the purchase agreement, Axo will acquire Sapuchi Minera S.A. de R.L. de C.V., which holds a 100-per-cent interest in the mineral concessions comprising San Antonio, subject to the satisfaction of certain conditions.

Upon closing of the transaction, Osisko Development will receive, subject to adjustment in accordance with the terms of the purchase agreement, 15,305,536 common shares of Axo or such other number of Axo shares that would result in Osisko Development owning 9.99 per cent of the issued and outstanding Axo shares on a non-diluted basis. Osisko Development will also be entitled to receive the following contingent payments:

• A cash payment equal to 70 per cent of any Mexican value-added tax refund due or owing to Sapuchi in respect of any period of time ending on or before the closing date of the transaction;
• Upon the public filing by Axo of a feasibility study respecting the project that is prepared in accordance with National Instrument 43-101, $2-million (U.S.), payable in cash or Axo shares, at Axo's option;
• Upon the first gold pour being completed at the project, $2-million (U.S.), payable in cash or Axo shares, at the company's option;
• In the event that Axo completes one or more equity financings that result in aggregate gross proceeds of at least $10-million (U.S.), Axo will issue to Osisko Development such number of Axo shares that would result in Osisko Development retaining a 9.99-per-cent interest in Axo, on a non-diluted basis, on the initial $10-million (U.S.) raised pursuant to such equity financing.

"In line with our strategy of focusing on priority development assets within our portfolio, we are pleased to announce the sale of San Antonio to Axo. We believe Axo is well equipped to successfully advance the project through its next phase and look forward to remaining a supportive long-term shareholder," commented Sean Roosen, chairman and chief executive officer.

The company has agreed that it will hold its Axo shares for at least 12 months following the closing of the transaction, and to comply with certain other conditions until the date that is 24 months from the date of completion of the transaction.

The project is not considered a material property of the company and has been in care and maintenance since the third quarter of 2023.

The transaction is subject to customary closing conditions, including the acceptance of the TSX Venture Exchange.

Bennett Jones LLP is acting as legal adviser to Osisko Development for the transaction.

About Osisko Development Corp.

Osisko Development is a continental North American gold development company focused on past-producing mining camps located in mining-friendly jurisdictions with district-scale potential. The company's objective is to become an intermediate gold producer by advancing its flagship permitted 100-per-cent-owned Cariboo gold project, located in central British Columbia, Canada. Its project pipeline is complemented by the Tintic project in the historic East Tintic mining district in Utah, United States, brownfield properties with significant exploration potential, extensive historical mining data, access to existing infrastructure and skilled labour. The company's strategy is to develop attractive, long-life, socially and environmentally responsible mining assets, while minimizing exposure to development risk and growing mineral resources.

We seek Safe Harbor.