Osisko Metals Incorporated announced an updated Mineral Resource Estimate (MRE" for the Gaspe Copper Project, located near Murdochville in the Gaspe Peninsula of Quebec. The updated MRE includes pit-constrained resources comprising 824 million tonnes grading 0.34% CuEq of Indicated category and 670 million tonnes grading 0.38% CuEq of Inferred category. This MRE represents a 53% increase in copper-equivalent metal content over the previously reported Indicated Resource and a 100-fold increase in copper-equivalent metal content in Inferred Resources.

At 4.91 billion pounds (2.23 million tonnes) of contained copper (Table 1), as well as significant molybdenum (274 million pounds) and silver (46.0 million ounces), the latest Gaspé Copper in-pit Indicated Resource hosts by far the largest undeveloped copper-molybdenum deposit in Eastern North America, exclusive of Inferred resources. Potential for resource expansion: Building upon the information released in this updated MRE, a minimum 70,000 metre drill program is planned to commence in May 2025 that will aim to 1) convert Inferred resources to Indicated category by reducing drill spacing to 100 metres or less within the pit volume, 2) better define higher-grade (0.5 to 1.5% % Cu) mineralization within pit boundaries in the B-Zone and C-Zone skarn horizons, 3) extend up-dip, shallower B-Zone and C-Zone skarn mineralization (near Needle Mountain) beyond current pit boundaries and 4) test shallower (above 600 m depth) portions of the high grade (2%-3% Cu) E-Zone skarn for inclusion into the pit volume. Implications of larger open pit resource at Gaspé Copper: The current modelled Whittle pit shell extends from the current flooded Copper Mountain pit towards the base of Needle Mountain to the south.

Further drilling, geological modelling and pit optimization will be required to refine pit boundaries. The Company will evaluate future pit limits and the possibility of reconfiguring the current layout of the site to minimize disturbance and ensure the protection and safety of the residents of Murdochville and the surrounding environment. General parameters of the updated Mineral Resource Estimate: This MRE is pit-constrained and includes stockwork mineralization surrounding the past-producing Copper Mountain open pit mine as well as disseminated, stratiform mineralization in both skarn and potassic-altered hornfels (porcellanite) that extends up-dip from Copper Mountain towards Needle Mountain to the south.

The MRE uses, amongst other parameters, a long-term price of USD 4.00/lb copper, a lower cut-off of 0.12% Cu for pit shell modelling and a lower cut-off grade of 0.12% copper for base case in-pit resource estimation. The resource was estimated using data from historical drilling completed between the 1950s and 2019 and 42,100 metres of drilling completed by the Company between 2022 and 2024. Cautionary Statement Regarding Copper Equivalent Grades: Copper Equivalent grades are expressed for purposes of simplicity and are calculated taking into account: 1) metal grades; 2) estimated long-term prices of metals: USD 4.00/lb copper, $20.00/lb molybdenum and USD 24/oz silver; 3) estimated recoveries of 92%, 70% and 70% for Cu, Mo and Ag respectively; and 4) net smelter return value of metals as percentage of the price, estimated at 86.5%, 90.7% and 75.0% for Cu, Mo and Ag respectively.