Mr. Keith Bodnarchuk of Cosa reports

COSA INTERSECTS UP TO 1.7% U3O8 WITHIN INTERVAL OF 5.0 M OF 0.55% U3O8 AT MURPHY LAKE NORTH JOINT VENTURE WITH DENISON MINES

Chemical assays have confirmed previously announced radioactive intersections include up to 1.7 per cent U3O8 (triuranium octoxide) within a broader interval of 5.0 metres of 0.55 per cent U3O8 at Cosa Resources Corp.'s Murphy Lake North (MLN) project. Muphy Lake North is a joint venture between Cosa and Denison Mines Corp. and is located three kilometres east of IsoEnergy's Hurricane deposit, in the eastern Athabasca basin in Saskatchewan. Cosa is the project operator and holds a 70-per-cent interest, with Denison holding a 30-per-cent interest.

Highlights:

• Uranium mineralization confirmed in three holes featuring a best intercept in MLN26-013 of 5.0 metres averaging 0.55 per cent U3O8, including 0.5 metre 1.7 per cent U3O8 along the Cyclone trend;
• The 5.0-metre uranium intersection in MLN26-013 also contains 4.1 per cent nickel and 1.7 per cent cobalt, consistent with multiple polymetallic eastern Athabasca uranium deposits, including Cigar Lake, Key Lake and Hurricane;
• Uranium mineralization is shallow at 265 metres depth and remains open along strike for 600 metres to the west and 600 metres to the east;
• Joint venture is in final stages of planning its largest drill program to date to follow up these results.

Keith Bodnarchuk, president and chief executive officer, commented: "This is a significant result for Cosa, with the assays confirming that Cyclone hosts uranium mineralization comparable to discovery intersections from multiple Athabasca uranium deposits. The Cyclone trend is an extensive corridor of strong structure and alteration that now features uranium mineralization that is open along strike for 600 metres in both directions. We expect to update the market in the coming days with plans for our largest drill program to date as a company. We appreciate the continued support and participation from our largest shareholder and joint venture partner, Denison, and we have never been more excited to return to site and resume drilling."

Andy Carmichael, vice-president of exploration, commented: "Winter drilling showed that the Cyclone sandstone alteration patterns, basement lithologies and faulting are strikingly similar to those at the nearby Hurricane deposit. Chemical assays indicate that Cyclone uranium mineralization contains significant quantities of nickel and cobalt, consistent with Hurricane and current- and past-producing mines like Key Lake and Cigar Lake. We are very encouraged that results have continued to improve as exploration advances and we are eager to continue follow-up both on section and along strike."

Murphy Lake North geochemical assays

Chemical assays confirm uranium mineralization is the source of anomalous radioactivity intersected in three of five winter drill holes at the Murphy Lake North joint venture announced April 13, 2026 (Table 1). The strongest uranium mineralization is in MLN26-013, which intersected up to 1.7 per cent U3O8 over 0.5 metre (310.5 to 311.0 metres) within a broader interval averaging 0.55 per cent U3O8 over 5.0 metres (308.5 to 313.5 metres). Like sandstone-hosted uranium deposits such as Hurricane, Key Lake and Cigar Lake, the mineralization is polymetallic and includes significant quantities of nickel and cobalt.

The 1.0-metre mineralized interval directly below the unconformity in MLN26-016 is immediately north of the strongest basement faulting intersected at Cyclone and 40 metres north of the nearest hole on section, suggesting a potential near-miss of the ideal target with significant space for additional mineralization.

All mineralized intersections remain open along strike for at least 600 metres to the east and 600 metres to the west.

Next steps

The company is currently finalizing summer drill plans, which it plans to announce shortly. Drilling is expected to commence in mid-June.

About Murphy Lake North

MLN covers a portion of the Larocque Lake trend and is located 2.7 kilometres east of the Hurricane deposit. Hurricane is the world's highest-grade indicated uranium resource and was discovered and delineated for IsoEnergy Ltd. by current members of Cosa's team. The Larocque Lake trend also hosts the high-grade Larocque Lake zone, Yelka prospect and Alligator Lake zone. MLN contains the along-strike extension of basement geology underlying the Hurricane deposit (the Hurricane trend) as well as a parallel conductive trend to the south (the Cyclone trend). Cosa's winter 2026 drill program intersected several metres of basement-hosted uranium mineralization within a broader zone of strong structure and alteration at the Cyclone trend. Following up these results is the primary objective for the remainder of 2026 at MLN.

About Cosa Resources Corp.

Cosa Resources is a Canadian uranium exploration company operating in Northern Saskatchewan. The portfolio comprises roughly 237,000 hectares across multiple underexplored 100-per-cent-owned and Cosa-operated joint venture projects in the Athabasca basin region, the majority of which reside within or adjacent to established uranium corridors.

In January, 2025, the company entered a transformative strategic collaboration with Denison that has secured access to several additional highly prospective eastern Athabasca uranium exploration projects. As Cosa's largest shareholder, Denison gains exposure to Cosa's potential for exploration success and its pipeline of uranium projects.

The company's primary focus through the remainder of 2026 will be drilling at the Murphy Lake North and Darby projects in the eastern Athabasca basin. Drilling at Murphy Lake North will follow up uranium mineralization within an extensive zone of strong structure and hydrothermal alteration at the Cyclone trend. Drilling at Darby will follow up on intersections of anomalous geochemistry, structure and zones of hydrothermal alteration from both winter 2026 drilling and historical drilling.

Cosa's award-winning management team has a record of success in Saskatchewan. In 2022, members of the Cosa team were awarded the AME Colin Spence Award for the discovery of the Hurricane uranium deposit. Cosa personnel led teams or had integral roles in the discovery of Denison's Gryphon deposit and held key roles in the founding of both NexGen and IsoEnergy.

Technical disclosure

Historical drilling and geophysical results for MLN were sourced from the Saskatchewan Mineral Assessment Database (SMAD). SMAD sources for MLN and adjacent projects include file numbers 64L05-0161, 64L05-0180, 74I-0060, 74I-0066, 74I-0067, 74I01-0114, 74I08-0056, 74I09-0053, 74I09-0057, 74I09-0061, 74I09-0064, 74I09-0066, 74I09-0071, 74I09-0077, 74I09-0079, 74I09-0087, 74I09-0088, 74I09-0090, 74I09-0091, 74I09-0092, 74I09-0098, MAW00510, MAW01939, MAW02327, MAW02599 and MAW02395. Data and reports related to the 2020 ground EM (electromagnetic) survey completed by Denison are not presently available through SMAD and were supplied to Cosa by Denison.

Verification of historical drilling results included confirming historical drill hole collar locations from air photos and ground checking selected collars with a hand-held GPS (Global Positioning System) unit. Basement and lower sandstone sections from most historical drill holes were relogged in 2024 and 2025 by Cosa.

Verification of historical geophysical results included confirming the locations of geophysical survey grids from air photos, compiling survey data and interpretations, and evaluating whether interpreted geophysical results could be reasonably explained by historical and current drilling results. For MLN, Cosa engaged a consultant to reinterpret historical geophysical surveys to validate selected previous interpretations.

Anomalous radioactivity in drill core was measured by removing 0.5-metre intervals of drill core to an area of background radioactivity and scanning it with an RS-125 hand-held spectrometer to determine average counts per second. Sampling was completed by collecting half-core splits measuring 0.5 metre in length with intervals that align with radioactive measurement intervals. Samples were transported to SRC Geoanalytical Laboratories (SRC) in Saskatoon, Sask. (ISO/IEC 17025:2005 accredited), for U3O8 assay and multielement analysis. Cosa inserts certified reference material (CRM) blanks and standards into the split core sample series as a quality assurance/quality control measure. SRC conducts a QA/QC program, which includes repeat analyses and insertion of CRM standards CAR218, BL4A, and BL2A. SRC's CRM results are verified by Cosa staff. U3O8 assay results are compared with RS-125 hand-held scintillometer readings and downhole gamma-probe results to verify chemical assays and measured radioactivity align.

Qualified person

The company's disclosure of technical or scientific information in this press release has been reviewed and approved by Andy Carmichael, PGeo, vice-president, exploration, for Cosa. Mr. Carmichael is a qualified person as defined under the terms of National Instrument 43-101. This news release refers to neighbouring properties in which the company has no interest. Mineralization on those neighbouring properties does not necessarily indicate mineralization on the company's properties.

We seek Safe Harbor.