Osisko Development Provides Infill Drilling Update on Its 13,000-m Program at Cariboo Gold Project; Intercepts Include 8.56 g/t Au Over 8.5m from 60.5m Depth, and 130.32 g/t Au Over 0.5m from 83.5m Depth

The most recent news, dated December 15, 2025, from Osisko Development Corp. (ODV) provides an update on its 13,000-meter infill drilling program at the Cariboo Gold Project's Lowhee Zone. The company reports that approximately 10,000 meters, or 72%, of the planned drilling has been completed from 62 holes, with results from 38 underground infill holes totaling around 3,704 meters being disclosed.

Key intercepts include: * 8.56 g/t Au over 8.5m from 60.5m depth (hole BMU-25-090) * 16.95 g/t Au over 4m from 80m depth (hole BMU-25-104) * 9.32 g/t Au over 6m from 58m depth (hole BMU-25-092) * 13.22 g/t Au over 2.65m from 87.85m depth (hole BMU-25-108) * High-grade interval of 130.32 g/t Au over 0.5m from 83.5m depth (part of BMU-25-104's 4m interval)

The company states that the results are consistent with the modelled reserve stopes and indicate potential for upside mineralization outside the current reserve outlines. The infill drilling program is on track to conclude in Q1 2026, with the data expected to refine production designs and sequencing.

This infill drilling update is a positive, but routine, development in the context of Osisko Development's overall progress. Over the past year, the company has achieved several significant milestones that have materially de-risked and advanced the Cariboo Gold Project:

1. Optimized Feasibility Study (April 2025): The 2025 FS presented robust economics (C$943M After-Tax NPV5% and 22.1% IRR at US$2,400/oz gold) and confirmed a significant probable mineral reserve of 2.071 million ounces of gold. This was a highly material positive event.
2. Full Project Permitting (Q4 2024): The Cariboo project received key Mines Act and Environmental Management Act permits, classifying it as "fully permitted" and "shovel-ready." This was also a highly material positive event, removing a significant hurdle.
3. Comprehensive Project Financing (July-October 2025):
   • A US$450 million credit facility from Appian Capital Advisory Ltd. was secured (July 2025), with an initial US$100 million draw. This facility provides a substantial portion of the capital needed for Cariboo's development. Appian also received 5.63M warrants at US$4.43.
   • Concurrent private placements (August and October 2025) raised a total of approximately US$203 million and C$82.5 million, respectively. Notably, Double Zero Capital LP invested US$75 million in the August placement, acquiring ~15.4% ownership and securing a board seat, signifying strong strategic investor confidence. These financings significantly bolstered the company's cash position (to C$401.4 million by Q3 2025) and fully funded the remaining initial capital required for construction. This overall financing package was a game-changer.
4. Major Exploration Campaign Launched (December 2025): The recent launch of a fully-funded 70,000-meter exploration drilling campaign targeting resource expansion at depth and new discoveries (Cariboo Deep, Proserpine Mountain) is a significant long-term positive, indicating confidence in future growth.

Against these backdrop events, the December 15, 2025, infill drilling update, while consistently positive with high-grade intercepts and alignment with geological models, serves as a validation of the Cariboo project's resource quality rather than a new material change in the company's fundamental outlook. The completion percentage (72%) and Q1 2026 timeline for the infill program are in line with previous guidance (Q3 2025 results stated 6900m complete and Q1 2026 expected completion). Therefore, this news is a routine positive development that reinforces existing expectations for the Cariboo project.

Osisko Development Corp. (ODV) is a Canadian gold development company primarily focused on advancing its 100%-owned Cariboo Gold Project located in central British Columbia, Canada. The company's strategy revolves around leveraging an operations-driven team to develop past-producing mining camps with district-scale and brownfield exploration potential, aiming to become an intermediate gold producer.

Flagship Project: Cariboo Gold Project The Cariboo Gold Project is Osisko Development's primary asset and focus. It is a fully permitted, feasibility-stage project with robust economics as outlined in its Optimized Feasibility Study (2025 FS).

• Location: Central British Columbia, Canada.
• Ownership: 100% owned.
• Permitting: Achieved full Mines Act and Environmental Management Act permits in Q4 2024, making it "shovel-ready" for construction. Transmission line approvals are ongoing.
• Feasibility Study (2025 FS):
  • Base Case (US$2,400/oz Au, 1.35 CAD:USD): Post-tax NPV5% of C$943 million and an unlevered after-tax IRR of 22.1%.
  • Spot Case (US$3,300/oz Au, 1.40 CAD:USD): Post-tax NPV5% of C$2.1 billion and an unlevered after-tax IRR of 38.0%.
  • Production: Average annual gold production of ~190,000 ounces over a 10-year mine life.
  • Costs: Average All-in Sustaining Costs (AISC) of US$1,157/oz over the life of mine.
  • Capital Costs: Initial capital cost of C$881 million.
  • Mineral Reserves: Probable Mineral Reserves of 2.071 million ounces of gold (17.8 million tonnes grading 3.62 g/t Au).
• Development Status: The project is in the pre-construction phase, with significant underground development (1,172 meters of drift completed) and bulk sample extraction (7,400 tonnes out of 10,000 tonnes target) already undertaken.
• Drilling: An ongoing 13,000-meter infill drilling program aims to refine mine planning, and a substantial 70,000-meter exploration drilling campaign has been launched to test depth extensions and new regional targets, signaling significant future growth potential.

Other Projects: * Tintic Project (Utah, U.S.A.): A 100%-owned project where small-scale heap leach operations have generated modest gold production. Exploration drilling (Phase II) has been completed, but without significant new intercepts. * San Antonio Gold Project (Sonora, Mexico): A 100%-owned project currently under care and maintenance. The company has announced an agreement to divest this non-core asset to Axo Copper Corp. for a combination of shares and contingent cash/share payments, in line with its strategy to focus on Cariboo.