Osisko Development Reports First Quarter 2026 Results

Press Release

HIGHLIGHTS

Q1 2026 (at March 31, 2026)

• Financial: ~$594.3 million in cash and cash equivalents; sold 270 ounces of gold from small-scale mining activities at the Tintic Project; received ~$36.5 million in proceeds from warrant exercises
• Financing: Completed a prospectus offering of common shares for ~US$143.8 million in gross proceeds
• Cariboo Gold Project: Resumed planned site activities under 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 Lowhee Zone (100% of planned drilling now complete, while final assays and reconciliation results remain pending); 11 drill rigs operating at site across various infill and exploration programs
• Corporate: Completed the 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)

Subsequent to Q1 2026

• Corporate: Granted incentive awards; appointed Sarah MacDonald as VP, Construction Contracting and Commercial

MONTREAL, May 11, 2026– Osisko Development Corp. (NYSE: ODV, TSXV: ODV) (“Osisko Development” or the “Company”) reports its financial and operating results for the three months ended March 31, 2026 (“Q1 2026”).

Q1 2026 HIGHLIGHTS

Operating, Financial and Corporate Updates:

• As of March 31, 2026, the Company had approximately $594.3 million in cash and cash equivalents. Approximately $153.2 million (US$109.9 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.
• $2.2 million in revenues (nil in Q1 2025) and $0.7 million in cost of sales (nil in Q1 2025) generated from the sale of 270 gold ounces from small-scale activities including heap leaching of certain tailings and stockpile material and direct shipping of mineralized material at the Tintic Project, generating an operating loss of $9.7 million ($40.8 million loss in Q1 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 January 27, 2026, the Company completed the previously announced sale of its 100% interest in the San Antonio Gold Project located in Sonora State, Mexico, to Axo Copper Corp. through the sale of Sapuchi Minera.
• 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 ($196.3 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. Together with other warrant exercises during Q1 2026, the Company received aggregate proceeds of $36.5 million from warrant exercises.
• 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.

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

• Infill Drilling Program. The 13,000-metre infill drill program within the Lowhee Zone was undertaken as part of the Appian 2025 Financing Facility obligations.
  • A total of 13,684 metres of drilling has been completed, representing 100% of the planned program, of which 11,025 metres have been released with assays. Assay results and associated quality assurance and quality control reviews are pending for unreleased holes. The Company anticipates finalizing the results for the 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 commissioning stages, with full operation expected in the second quarter of 2026.
  • Underground development: To date, approximately 2.1 km 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. The raisebore pad for the first underground ventilation raise started in Q1 2026.
  • Surface infrastructure: Construction of the waste rock storage facility, the sediment control pond, and other critical infrastructure continues. Early works, including tree clearing and geotechnical drilling, commenced in Q1 2026 at the mine site complex, where the primary processing facility will be located.
  • Camp upgrade: The site camp upgrade and expansion to 266 rooms is complete and, together with other Company-controlled accommodations, is expected to provide capacity aligned with peak construction manpower requirements.
• Exploration & Conversion Drilling Programs. A multi-faceted exploration drilling campaign across the Cariboo Gold Project and regional targets is underway. Together with planned infill drilling that has the objective of upgrading inferred mineral resources to higher confidence categories, up to 20 drill rigs are expected to be active at times throughout 2026, as the various programs overlap and advance, representing up to approximately 160,000 metres of planned drilling across all targets. Eleven drill rigs are currently operating across all programs.
  • Eight drill rigs are currently operating on two surface exploration programs, including four surface drill rigs targeting potential mineralization below the current extent of the Cariboo Gold Project deposit to depths of up to 1,000 metres. To date, approximately 10,600 metres of drilling have been completed, with assays pending.
  • A second surface exploration program on the adjacent Proserpine regional target has ramped up to four drill rigs, with approximately 5,750 metres completed to date.
  • Infill and conversion drilling is planned in 2026 with the objective of upgrading inferred mineral resources to higher confidence resource categories and potentially into mineral reserves, after considering applicable modifying factors. The initial targets are within and below the current Cariboo Gold deposit.

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

Figure 2: Sediment control pond (SCP) installed liner and placement of aggregates.

Figure 3: BL water treatment plant commissioning (legacy and expansion).

Figure 4: Mine site complex processing facility site preparation works.

Figure 5: Lowhee Zone ventilation raise bore.

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 and direct shipping of mineralized material which generated sales of 270 ounces of gold. Test mining continued in Q1 2026, with approximately 2,000 tonnes of higher-grade mineralized material stockpiled for direct shipping to a purchaser. Test mining is anticipated to continue in Q2 2026.
• 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, including any additional direct shipping of mineralized material from the Trixie test mine.

2026 OBJECTIVES

Activity		Expected Timing of Completion(2)		Anticipated 2026 Cost(1)
Cariboo Gold Project
Underground Development (including production drilling)		Q4 2026		$39.5 million
Regional surface exploration drilling		Q4 2026		$3.7 million
Mine design, processing, water management, infrastructure and other		Q4 2026		$14.7 million
Underground Infill Drilling to Convert Mineral Resources to Mineral Reserves		Q4 2026		$4.4 million
Surface (Directional) Drilling to expand Mineral Resource Estimate at depth (up to 300 metres below current Mineral Resource Estimate)		Q4 2026		$1.7 million
Surface Drilling to expand geology and mineralization at depth (+700 metres below surface)		Q4 2026		$3.9 million

_______________________________
Note:
(1)	The expenditures disclosed in this table include amounts approved by the Board of Directors as at March 31, 2026, net of amounts already incurred during the first quarter of 2026. Additional expenditures will be required to complete certain of the objectives and are subject to approval by the Board of Directors.
(2)	For the portion of activities to be incurred in 2026.

SUBSEQUENT TO Q1 2026

• On April 1, 2026, the Company granted an aggregate of (i) 1,104,400 stock options of the Company (the “Options”), and (ii) 1,426,600 restricted share units of the Company (“RSUs”) to certain senior officers and non-executive employees (collectively, the “Incentive Awards”), pursuant to the Company’s omnibus equity incentive plan.
• On May 4, 2026, the Company appointed Ms. Sarah MacDonald as Vice President, Construction Contracting and Commercial.

Consolidated Financial Statements

The Company’s unaudited condensed interim consolidated financial statements (the “Financial Statements”) and related management’s discussion and analysis (“MD&A”) for the three months ended March 31, 2026 have been filed with Canadian securities regulatory authorities and 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.

Qualified Persons

The scientific, geological and technical information 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 RoosenPhilip RabenokChairman and CEOVice President, Investor RelationsEmail: sroosen@osiskodev.comEmail: prabenok@osiskodev.comTel: +1 (514) 940-0685Tel: +1 (437) 423-3644

IBF4