Osisko Development Reports Fourth Quarter and Year-End 2025 Results

Press Release

HIGHLIGHTS

Q4 2025 (at December 31, 2025)

• Financial: ~$422.3 million in cash and cash equivalents; sold 3,970 ounces of gold from small-scale mining activities at the Tintic Project
• Financing: Completed a private placement financing for ~$82.5 million in gross proceeds
• Cariboo Gold Project: Released new infill drill results from the ongoing program in the Lowhee Zone and commenced a multi-faceted surface exploration program targeting new discoveries; pre-construction activities continued to advance, including the water treatment plant, underground development waste rock storage facility, sediment control pond, site camp upgrade and other critical infrastructure
• Corporate: Announced sale of the San Antonio Gold Project; Appointed Scott Smith as VP, Exploration

Subsequent to Q4 2025

• Financial: Received ~$24.9 million in proceeds from a warrants exercise
• Financing: Completed prospectus offering of common shares for ~US$143.8 million in gross proceeds
• Cariboo Gold Project: Resumed planned site activities in accordance with a phased reopening plan following a temporary suspension due to a fatal incident that occurred on January 22, 2026; entered into a project and construction management services agreement with JDS Energy & Mining; released new infill drill results from the ongoing Lowhee Zone (aggregate total 11,025 metres, or ~80% of planned program)
• Corporate: Completed sale of the San Antonio Gold Project; appointed Sarah Harrison as VP, Permitting & Compliance; announced the Company’s inclusion in the VanEck Junior Gold Miners ETF (GDXJ)

MONTREAL, — Osisko Development Corp. (NYSE: ODV, TSXV: ODV) (“Osisko Development” or the “Company”) reports its financial and operating results for the three and twelve months ended December 31, 2025 (“Q4 2025” and “2025”, respectively).

Q4 2025 HIGHLIGHTS

Operating, Financial and Corporate Updates:

• As of December 31, 2025, the Company had approximately $422.3 million in cash and cash equivalents. Approximately $145.8 million (US$106.4 million), inclusive of accrued interest, is outstanding under the initial draw of the US$450 million senior secured project loan credit facility (the “2025 Financing Facility”) with funds advised by Appian Capital Advisory Limited (“Appian”) for the development and construction of the Cariboo Gold Project.
• $24.2 million in revenues (nil in Q4 2024) and $6.8 million in cost of sales (nil in Q4 2024) generated from the sale of 3,970 gold ounces from small-scale activities including heap leaching of certain tailings and stockpile material and selective mining at the Tintic Project, generating operating income of $8.7 million ($19.8 million loss in Q4 2024).
• During the quarter, the Company released new infill drilling results from its ongoing 13,000-metre underground infill drilling program in the Lowhee Zone of its Cariboo Gold Project. An aggregate total of 5,983 metres of drilling results was released, representing approximately 44% of the total planned program.
• On October 29, 2025, the Company completed a private placement offering of 15,409,798 common shares of the Company for aggregate gross proceeds of approximately $82.5 million comprised of:
  • LIFE Offering ($50 million): (i) 2,990,000 common shares that qualified as “flow-through shares” (“FT Shares”) within the meaning of subsection 66(15) of the Income Tax Act (Canada) (the “Tax Act”) at a price of $6.69 per FT Share for gross proceeds of approximately $20.0 million; (ii) 1,444,000 common shares to certain eligible British Columbia resident subscribers (the “BC FT Shares”) that qualified as “flow-through shares” within the meaning of subsection 66(15) of the Tax Act at a price of $6.93 per BC FT Share for gross proceeds of approximately $10.0 million; and (iii) 4,182,000 common shares at a price of $4.78 per common share for gross proceeds of approximately $20.0 million.
  • Private Placement ($32.5 million): 6,793,798 common shares at a price of $4.78 per common share for gross proceeds of approximately $32.5 million pursuant to exemptions available under NI 45-106.
• On November 3, 2025, the Company announced the appointment of Mr. Scott Smith as Vice President, Exploration effective November 1, 2025.
• On November 24, 2025, the Company announced that it entered into a securities purchase agreement with Axo Copper Corp. (“Axo”) to sell its 100% interest in the San Antonio Gold Project located in Sonora State, Mexico. The transaction closed on January 27, 2026 (refer to section entitled Discontinued Operations – San Antonio Gold Project).
• On December 8, 2025, the Company announced the launch of a fully-funded 70,000-metre exploration drilling campaign aimed at targeting new discoveries at the Cariboo Gold Project.

Cariboo Gold Project – British Columbia, Canada (100%-owned)

• Infill Drilling Program. The ongoing 13,000-metre infill drill program within the Lowhee Zone is being undertaken as part of the Appian 2025 Financing Facility obligations, from existing underground development infrastructure.
  • The infill program is expected to provide a comprehensive data set that will inform resource modeling, mine planning and production stope design procedures and parameters. It will also support the development of a systematic approach to infill drilling for the underground mining operation.
  • In 2025, a total of 5,983 metres of drilling was released, representing ~44% of the planned program. To date, 11,025 metres of drilling have been released, representing ~80% of the planned program, with 96% of the total planned drilling completed. Assay results and associated quality assurance and quality control reviews are pending for unreleased holes. The Company anticipates completing the 13,000-metre infill drill program in the second quarter of 2026.
• Pre-Construction Activities. The Company continues to advance pre-construction activities, including certain surface infrastructure and underground development.
  • Water treatment plant: Upgrades to the Bonanza Ledge water treatment plant are in the final stages of commissioning and the facility is anticipated to be fully operational in the second quarter of 2026.
  • Underground development: To date, approximately 2.1 kilometres of underground development has been completed from the existing Cow Portal into the Lowhee Zone, and along the main access ramp, through the Lowhee fault, towards the Cow Mountain Zone. Development progress has been below plan while encountering challenging ground conditions in and around the Lowhee fault, requiring enhanced ground support. Development rates are expected to improve as the ramp advances beyond this zone.
  • Surface infrastructure: Construction of the waste rock storage facility, the sediment control pond, early works in the mine site complex (“MSC”) area and other critical infrastructure continues.
  • Camp upgrade: The upgrade and expansion of the site camp to 266 rooms is complete and is expected to provide accommodation capacity aligned with peak construction manpower requirements for the project.
• Exploration & Conversion Drilling Programs. In the quarter, the Company commenced a multi-faceted exploration drilling campaign across the Cariboo Gold Project and regional targets. Together with planned infill conversion drilling, up to 20 drill rigs are expected to be active at times throughout 2026, as the various programs overlap and advance, for a combined total of approximately 160,000 metres of planned drilling across all targets.
  • A total of six drill rigs are currently operating on two surface exploration programs, including three surface drill rigs targeting exploration below the current extent of the Cariboo Gold deposit to depths of up to 1,000 metres.
  • To date, approximately 6,000 metres of drilling have been completed, with assays pending. A second surface exploration program on the adjacent Proserpine regional target has also commenced and ramped up to three drill rigs, with approximately 1,500 metres completed to date.
  • Infill and conversion drilling is planned for 2026 to upgrade inferred resources to higher level confidence resource categories with potential to be converted into mineral reserves. The initial targets are within and below the current Cariboo Gold deposit.

Figure 1: Waste rock storage facility (WRSF) aerial overview.

Figure 2: Sediment control pond (SCP) spillway pipe encasement.

Figure 3: BL water treatment plant commissioning in progress.

Figure 4: Lowhee Zone ventilation raise foundation drilling.

Figure 5: Active surface exploration drill rig on Cow Mountain targeting areas below the Cariboo Gold deposit.

Tintic Project – Utah, U.S.A. (100%-owned)

• Small-Scale Heap Leach Project and Selective Mining. In the quarter, the Company continued small-scale heap leaching of certain tailings and stockpiled material, generating sales of 1,992 ounces of gold. In addition, small-scale selective mining activities in the quarter resulted in the sale of 1,978 ounces of gold.
  • In total, these activities resulted in the sale of 6,240 gold ounces in 2025 from the cumulative processing of 22,668 metric tonnes at an average grade of 11.17 grams per tonne gold and average recoveries of approximately 80%, generating revenue of $35.5 million ($4.6 million in 2024) and cost of sales of $13.9 million ($4.8 million in 2024).
• While management continues to evaluate options for the next steps at the Tintic Project, it is expected that limited activities beyond care and maintenance may occur on the Tintic Project from time to time.

Figure 6: Gold bar (~276 troy ounces) poured from small-scale activities at the Tintic Project (March 2026).

2026 OBJECTIVES

Activity		Expected Timing of Completion2		Anticipated 2026 Cost1
Cariboo Gold Project
Underground Development (including production drilling)		Q4 2026		$40.2 million
Underground infill drilling (13,000 metres)3		Q2 2026		$0.6 million
Regional surface exploration drilling		Q4 2026		$6.8 million
Mine design, processing, water management, infrastructure and other		Q4 2026		$9.9 million
Underground Infill Drilling to Convert Mineral Resources to Mineral Reserves		Q4 2026		$1.8 million
Surface (Directional) Drilling to expand Mineral Resource Estimate at depth (up to 300 metres below current Mineral Resource Estimate)		Q4 2026		$2.5 million

DISCONTINUED OPERATIONS – SAN ANTONIO GOLD PROJECT

• On November 24, 2025, the Company entered into an agreement to sell its 100% interest in the San Antonio Gold Project located in Sonora State, Mexico, through the sale of all of the issued and outstanding equity interests of Sapuchi Minera S. de R.L. de C.V. (“Sapuchi Minera”) which held a 100% interest in the mineral concessions comprising the San Antonio Project, to Axo Copper Corp. The transaction closed on January 27, 2026.
• At closing, the Company received 15,325,841 common shares of Axo, representing 9.99% of Axo’s outstanding shares on a non‑diluted basis. The Company is also entitled to certain contingent deferred payments in connection with the sale, as well as an anti-dilution provision whereby a qualifying financing triggers the issuance of Axo shares to the Company. Subsequent to closing, the Company received an additional 2,363,516 Axo common shares pursuant to the anti‑dilution provision triggered by a qualifying financing. In addition to the shares received, the Company is entitled to certain contingent deferred payments, including: (i) a cash payment equal to 70% of any Mexican VAT refund relating to periods ending on or before closing; (ii) US$2 million payable in cash or Axo shares upon Axo’s filing of a NI 43‑101 compliant feasibility study; and (iii) US$2 million payable in cash upon the project’s first gold pour.

SUBSEQUENT TO Q4 2025

• On January 22, 2026, a contractor working on surface activities suffered a fatal injury following an isolated incident at the Cariboo Gold Project. The Company promptly notified appropriate authorities, and an investigation of the incident was initiated. Activities at the project site were temporarily suspended to allow for completion of an investigation. On March 2, 2026, resumption of planned site activities was announced, following the successful implementation of a phased gradual reopening plan of surface and underground activities over several preceding weeks, in coordination with and approval from the relevant regulatory authorities, and with a focus on ensuring the health and safety of all employees and contractors.
• On February 2, 2026, the Company appointed Ms. Sarah Harrison as Vice President, Permitting and Compliance.
• On February 3, 2026, the Company completed its previously announced (on January 26, 2026) prospectus offering of common shares of the Company, issuing an aggregate of 40,607,650 common shares at a price of US$3.54 per common share for aggregate gross proceeds of US$143.8 million ($196.2 million).
• On February 9, 2026, the Company entered into a definitive Project and Construction Management Services Agreement with JDS Energy & Mining Inc. for the development of the Cariboo Gold Project.
• On March 9, 2026, the Company announced receipt of approximately $24.9 million from the exercise of 5,625,031 common share purchase warrants of the Company, held by certain funds advised by Appian Capital Advisory Limited.
• On March 16, 2026, the Company announced inclusion in the VanEck Junior Gold Miners ETF (“GDXJ”) announced on March 13, 2026, which became effective at the close of markets on March 20, 2026.
• On March 27, 2026, Osisko Development’s Board of Directors approved certain minor administrative amendments to the Company’s omnibus equity incentive plan to facilitate plan administration. The omnibus incentive plan was last approved by shareholders on May 7, 2025. In accordance with the terms of the omnibus equity incentive plan and applicable TSX Venture Exchange policies, shareholder approval is not required for these amendments. The amended omnibus equity incentive plan remains subject to final acceptance by the TSX Venture Exchange.

2025 Year-End Disclosure Documents

The Company’s annual information form (“AIF”) for the year ended December 31, 2025, audited consolidated financial statements (the “Financial Statements”) and related management’s discussion and analysis (“MD&A”) for the three and twelve months ended December 31, 2025 have been filed with Canadian securities regulatory authorities. Osisko Development has also filed its Annual Report Form 40-F consisting of its AIF, Financial Statements and MD&A for the year ended December 31, 2025 with the U.S. Securities and Exchange Commission.

These filings are available on the Company’s website at www.osiskodev.com, on SEDAR+ (www.sedarplus.ca) and on EDGAR (www.sec.gov) under Osisko Development’s issuer profile. Hard copies of these documents are available to shareholders of the Company upon written request to the Company’s Investor Relations department, 1100, Av. des Canadiens-de-Montreal, Suite 300, Montreal, Quebec, Canada H3B 2S2 or to ir@osiskodev.com.

Qualified Persons

The scientific, geological and technical information contained in this news release has been reviewed and approved by Scott Smith, P. Geo., Vice President, Exploration of Osisko Development, who is considered a “qualified person” within the meaning of National Instrument 43-101 – Standards of Disclosure for Mineral Projects (“NI 43-101”).

Technical Reports

Scientific and technical information relating to the Cariboo Gold Project and the 2025 Feasibility Study on the Cariboo Gold Project is supported by the technical report titled “NI 43-101 Technical Report, Feasibility Study for the Cariboo Gold Project, District of Wells, British Columbia, Canada” and dated June 11, 2025 (with an effective date of April 25, 2025) (the “Cariboo Technical Report”).

Scientific and technical information relating to the Tintic Project and the current mineral resource estimate for the Trixie deposit (the “2024 Trixie MRE”) is supported by the technical report titled “NI 43-101 Technical Report, Mineral Resource Estimate for the Trixie Deposit, Tintic Project, Utah, United States of America” and dated April 25, 2024 (with an effective date of March 14, 2024) (the “Tintic Technical Report” and, together with the Cariboo Technical Report, the “Technical Reports”).

For readers to fully understand the information in the Technical Reports, reference should be made to the full text of the Technical Reports in their entirety, including all assumptions, parameters, qualifications, limitations and methods therein. The Technical Reports are intended to be read as a whole, and sections should not be read or relied upon out of context. The Technical Reports were prepared in accordance with NI 43-101 and are available electronically on SEDAR+ (www.sedarplus.ca) and on EDGAR (www.sec.gov) under Osisko Development’s issuer profile and on the Company’s website at www.osiskodev.com.

ABOUT OSISKO DEVELOPMENT CORP.

Osisko Development Corp. 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%-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, U.S.A., 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.

For further information, visit our website at www.osiskodev.com or contact:

Sean Roosen	Philip Rabenok
Chairman and CEO	Vice President, Investor Relations
Email: sroosen@osiskodev.com	Email: prabenok@osiskodev.com
Tel: +1 (514) 940-0685	Tel: +1 (437) 423-3644

IBF4