Denison Acquires Interests in Russell Lake Properties Adjacent to Wheeler River

• Denison acquires initial interests ranging from 20% to 70% in four property joint ventures covering land adjacent to Wheeler River Project
• Total consideration of $18 million includes $2 million upfront payment and $16 million in deferred payments due before 31 December 2025
• Earn-in options allow Denison to increase ownership to 70% in Wheeler North and Getty East through exploration expenditures
• Wheeler North covers 16,409 hectares, Russell Lake spans 53,192 hectares, Getty East comprises 3,105 hectares, and Wheeler River Inliers total 608 hectares
• Transaction expected to close on or before 21 December 2025, subject to TSX Venture Exchange approval

Denison Mines Corp. (TSX:DML; NYSE American:DNN) is a uranium mining, development, and exploration company with interests in the Athabasca Basin region of northern Saskatchewan, Canada. The company holds a 95% interest in the Wheeler River Uranium Project, the largest undeveloped uranium project in the eastern portion of the Athabasca Basin.

Russell Lake Property Acquisition and Joint Venture Structure

The agreement divides Skyharbour's Russell Lake Uranium Project into four property joint ventures with varying ownership structures. Wheeler North comprises 16,409 hectares over eight claims along the northeast boundary of Wheeler River, with Denison acquiring a 49% initial interest and Skyharbour retaining 51%. Russell Lake consists of 53,192 hectares across 16 claims east of Wheeler River, where Denison takes a 20% stake and Skyharbour maintains 80% and operational control.

Wheeler River Inliers represents 608 hectares of inlaying claims within Wheeler River's boundaries, with Denison holding 70% and assuming operator responsibilities. Getty East is a single claim of 3,105 hectares located less than 10 kilometres southeast of Wheeler River, bordering Cameco's Cree Zimmer property near Key Lake operations. Denison acquires a 30% interest whilst Skyharbour retains 70% and remains operator.

David Cates, President and CEO of Denison, stated:

"Given its proximity to Wheeler River, Denison has had an interest in adding Russell to our property portfolio for much of my nearly two decades with the Company."

Denison will maintain its initial interest in Russell Lake by funding its pro rata share of up to C$10 million in total project expenditures. The agreement also grants Denison priority access to Skyharbour's existing Russell exploration camp near Highway 914, with Denison paying usage fees and a 7% administrative fee.

Transaction Terms and Consideration Payments

Denison agreed to pay Skyharbour total consideration of $18 million, structured as a $2 million cash payment upon execution of the agreement and deferred consideration of $16 million. The deferred amount consists of two tranches of $8 million each, payable before 31 December 2025. Denison may elect to pay the deferred consideration in cash or common shares.

The first deferred payment of $8 million is due on or before the fifth business day prior to 21 December 2025. The second deferred payment of $8 million is due within 10 days of 21 December 2025. Closing is expected to occur on or before 21 December 2025.

Jordan Trimble, President and CEO of Skyharbour, stated:

"This is a transformative transaction for Skyharbour and our shareholders as it represents a major stamp of approval for Russell. We are very pleased to expand upon our long-standing relationship with Denison."

The transaction requires customary approvals, including TSX Venture Exchange approval, and will be considered a reviewable transaction under TSX Venture Exchange policies as David Cates serves as a director of both companies.

Earn-In Option Agreements for Wheeler North and Getty East

The earn-in agreements establish pathways for Denison to increase its ownership in Wheeler North and Getty East to 70%. For Wheeler North, Denison can acquire an additional 11% interest (reaching 60% total) by incurring $10 million in exploration expenditures within 48 months of closing, including $2.5 million within the first 24 months, plus making a $1.5 million cash payment to Skyharbour within 48 months.

Phase 2 of the Wheeler North earn-in requires completion of Phase 1 plus an additional $15 million in exploration expenditures within seven years of closing and a further $2 million cash payment to Skyharbour within seven years. This would increase Denison's ownership to 70%. Denison becomes the operator of Wheeler North upon completing Phase 1 requirements.

Phase 1 of the Getty East earn-in requires $5 million in exploration expenditures within 48 months of closing, with $1.5 million within the first 24 months. This would increase Denison's ownership to 49%. Phase 2 requires completion of Phase 1 plus an additional $10 million in exploration expenditures within seven years of closing, increasing Denison's ownership to 70%. Completion of Phase 2 provides Denison the option to become the operator of Getty East.

Next Steps and Timeline

The transaction is expected to close on or before 21 December 2025, subject to customary approvals including TSX Venture Exchange approval. Upon closing, Denison will assume operational control of Wheeler North (after completing Phase 1 earn-in requirements) and Wheeler River Inliers joint ventures.

The transaction timing coincides with Denison's permitting progress at Wheeler River, where the project's environmental assessment received provincial approval in July 2025. Canadian Nuclear Safety Commission hearings for federal environmental assessment approval and project construction licence commenced in October 2025, with continuation scheduled for the week of 8 December 2025. The Russell Lake properties are located adjacent to Wheeler River, which hosts the Phoenix and Gryphon deposits.

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