Vancouver, British Columbia, September 16, 2026 – Cosa Resources Corp. (TSX-V: COSA) (OTCQB: COSAF) (FSE: SSKU) (“ Cosa ” or the “ Company ”) is pleased to announce commencement of drilling at the Company’s Darby (“ Darby ”) project (Figure 1). Darby is a joint venture (the “ Joint Venture ”) between Cosa and Denison Mines Corp. (“ Denison ”) (TSX: DML) (NYSE American: DNN) and is located 10 kilometres west of Cameco’s Cigar Lake Mine. Cosa is the project operator and holds a 70% interest with Denison holding a 30% interest.
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Beyond Boundaries
Keith Bodnarchuk, President and CEO, commented: “Having recently completed an encouraging and productive drilling program at Murphy Lake North, we are excited to be back drilling at the Darby Joint Venture with our partner and largest shareholder, Denison Mines. Viewed by Cosa as a discovery-ready Project, Darby boasts an exceptional pipeline of high-upside drill targets in proximity to structure, alteration, and historical uranium mineralization. With $16 million in the treasury, we are fully funded for the summer program and follow-up in 2027. While our core focus remains on advancing the Murphy Lake North and Darby joint ventures with Denison, we are finalizing plans for a 100% partner funded drilling program expected to[AC1.1] commence at our Aurora project in the coming days.”
Andy Carmichael, VP Exploration, commented: “In addition to intersecting basement-hosted uranium mineralization, winter drilling and reinterpretation of historical results at Darby further upgraded multiple trends, notably at Gamma and Bravo. The exceptional geochemical anomalism, numerous intersections of graphitic structure, and significant untested strike length across virtually all major trends at Darby continues to make for an exciting drill season. At Gamma, drilling will further test a broad zone of structure and alteration defined during the winter program that is also on trend with multiple occurrences of historical mineralization. At Bravo, drilling will follow up prospective geology and uranium mineralization intersected by multiple historical drill holes that lie within a magnetic low trend interpreted[JR2.1] to extend to the Cigar Lake uranium Mine area.”
Darby Summer Drilling
Up to 2,500 metres of drilling is planned to test multiple targets at each of the Gamma and Bravo trends (Figure 2). At Gamma, drilling will build on positive results from the winter campaign where drill hole DB24-41 defined a 100+ metre wide zone hosting graphitic basement faulting associated with 30+ metres of unconformity relief, sandstone and basement alteration, and elevated to anomalous uranium geochemistry in the basal sandstone. Uranium mineralization has been intersected by multiple historical drill holes on the Gamma trend immediately north of the Project. At Bravo, drilling will target the trend along-strike of encouraging historical results including graphitic structure, alteration, and uranium mineralization associated with more than 25 metres of unconformity relief. The Bravo trend is interpreted to lie within a magnetic low trend extending through the Cigar Lake uranium Mine to the northeast.
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About Darby
Located 10 kilometres west of the Cigar Lake Mine, Darby contains multiple prospective conductive trends and several intersections of weak uranium mineralization (Figures 1 and 2). Historical drilling indicates that many of these trends are highly prospective for uranium deposits characteristic of the eastern Athabasca Basin, yet most of the strike length has not been effectively evaluated. Work by Cosa in 2025 prioritized these trends and identified several historical drill holes with results that suggest proximity to uranium mineralization (See Cosa’s news releases dated October 14, 2025 and January 21, 2026).
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About Cosa Resources Corp.
Cosa Resources is a Canadian uranium exploration company operating in northern Saskatchewan. The portfolio comprises roughly 237,000 ha across multiple underexplored 100% 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 2025, the Company entered a transformative strategic collaboration with Denison (TSX: DML) (NYSE American: DNN) 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.
Cosa’s award-winning management team has a track 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 Darby were sourced from the Saskatchewan Mineral Assessment Database (SMAD). SMAD sources for Darby include file numbers 74H14-0021, 74H14-0023, 74H15-0041, 74H15-0053, 74H15-0055, 74H15-0056, 74H15-0066, 74H15-0067, 74I02-0031, 74I02-0042, 74I02-0053, 74I02-0080, 74I02-0095, and MAW00516. Some confidential data and reports not presently available via SMAD 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 handheld GPS unit. Basement and lower sandstone sections from most historical drill holes were relogged in 2024 and 2025 by Cosa. Verification of geochemical results for drill holes completed between 2008 and 2010 was facilitated by the reissuance of analytical certificates to Cosa by the Saskatchewan Research Council (SRC). Cosa thanks the SRC for its valued assistance in increasing confidence in the historical dataset.
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.
Samples from Cosa’s drilling were transported to SRC Geoanalytical Laboratories (SRC) in Saskatoon, Saskatchewan (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 QA/QC measure. SRC conducts a QA/QC programme which includes repeat analyses and insertion of CRM standards CAR218, BL4A, and BL2A, as appropriate. SRC’s CRM results are verified by Cosa staff.
Qualified Person
The Company’s disclosure of technical or scientific information in this press release has been reviewed and approved by Andy Carmichael, P.Geo., 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.
Contact
Keith Bodnarchuk, President and CEO
info@cosaresources.ca
+1 888-899-2672 (COSA)
Cautionary Statements
This press release contains forward-looking information within the meaning of Canadian securities laws (collectively “forward-looking statements”). Forward-looking statements are typically identified by words such as: believe, expect, anticipate, intend, estimate, plans, postulate and similar expressions, or are those, which, by their nature, refer to future events. All statements that are not statements of historical fact are forward-looking statements. These forward-looking statements or information may relate to anticipated exploration, development and/or expansion activities, including exploration of the Company’s current Projects; the collaboration with Denison, including the Joint Venture, and the anticipated benefits thereof; and the outlook regarding Cosa’s business plans and objectives.
Such forward-looking information and statements are based on numerous assumptions, including among others, that the results of planned exploration activities are as anticipated, the cost of planned exploration activities are as anticipated, that general business and economic conditions will not change in a material adverse manner, that financing will be available if and when needed and on reasonable terms, that third party contractors, equipment and supplies and governmental and other approvals required to conduct Cosa’s planned exploration activities will be available on reasonable terms and in a timely manner. Although the assumptions made by Cosa in providing forward-looking information or making forward-looking statements are considered reasonable by management at the time, there can be no assurance that such assumptions will prove to be accurate.
By their nature, forward-looking statements involve known and unknown risks, uncertainties and other factors which may cause our actual results, performance or achievements, or other future events, to be materially different from any future results, performance or achievements expressed or implied by such forward-looking statements. Such factors and risks include, among others: Cosa may require additional financing from time to time in order to continue its operations which may not be available when needed or on acceptable terms and conditions acceptable; Cosa may not be able to maintain compliance with its contractual obligations with third parties; Cosa may not be able to maintain compliance with extensive government regulation applicable to its operations; domestic and foreign laws and regulations could adversely affect Cosa’s business and results of operations; the stock markets have experienced volatility that often has been unrelated to the performance of companies and these fluctuations may adversely affect the price of Cosa’s securities, regardless of its operating performance; the ongoing military conflict in Ukraine, and other risk factors set out in Cosa’s public disclosure documents.
The forward-looking information contained in this news release represents the expectations of Cosa as of the date of this news release and, accordingly, is subject to change after such date. Readers should not place undue importance on forward-looking information and should not rely upon this information as of any other date. Cosa does not undertake any obligation to update these forward-looking statements in the event that management's beliefs, estimates or opinions, or other factors, should change.
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