Osisko Development announces preliminary economic assessment for the Cariboo Gold Project and refiling certain continuous disclosure documents

The PEA provides a technical and economic update based on the updated underground Mineral Resource Estimate (“MRE”) from the 2021 diamond drill campaign and current costs and economic estimates. The MRE contains 27.1 million tonnes (“Mt”) at an average grade of 4.0 grams per tonne gold (“g/t Au”) for a total of 3.47 million ounces (“M oz”) in the Measured and Indicated Category (consisting of a Measured Resource of eight thousand ounces of gold (47,000 tonnes grading 5.1 g/t Au) and an Indicated Resource of 3.46 million ounces of gold (27 million tonnes grading 4.0 g/t Au)) and 14.4 Mt at a grade of 3.5 g/t Au for a total of 1.6 M oz in the Inferred category (Table 6). These mineral resources have informed an 8,000 tonnes per day (“tpd") scenario over a 12-year operating mine life, which highlights the potential growth of the Cariboo Gold Project. The PEA is available on the Company’s website and the profile of the Company at www.sedar.com. The Company notes that mineral resources are not mineral reserves as they do not have demonstrated economic viability.  The Company notes that a preliminary economic assessment is preliminary in nature, it includes inferred mineral resources that are considered too speculative geologically to have economic consideration applied to them that would enable them to be categorized as mineral reserves, and there is no certainty that the preliminary economic assessment will be realized.

The PEA illustrates potential economics for a low cost, large scale, underground gold mine, with industry leading operating costs. The study outlines total gold production of 2.8 million gold ounces, resulting in an average annual gold production profile of 236,000 ounces with an All-In-Sustaining Cost (“AISC”) per ounce of $1,222 (US$962) (AISC is a non-IFRS measure – please see under the heading "Non-IFRS Measures" below). The Project after-tax net present value (“NPV”) (5% discount rate) is $764 million with an after-tax internal rate of return (“IRR”) of 21.4% at a gold price of $2,223 (US$1,750) per ounce, and $912 million and 24.5% at a spot gold price for May 19, 2022 at $2,343 (US$1,845) per ounce.

The PEA recommends that the Company continues to work towards a feasibility study and completes the following steps:

1. Incorporate all drilling results from 2021 and 2022 currently in progress in the resources.
2. Complete the development of the ramp and extraction of the 10,000-tonne (“t”) bulk sample that will help support the evaluation and testing of the proposed roadheader mining equipment and ore sorting equipment and gain experience to maximize the full potential of these technologies.
3. Integrate the information and experience gained with the bulk sample into the development strategy of the mine and the feasibility study planning.
4. Continue exploration program with drilling (infill and exploration), geological mapping, and grab sampling to test the depth extensions of known high-grade vein corridors and identify new targets.

The Company plans to proceed with a feasibility study in connection with the work plan recommended by the PEA.

The Company advises that this clarifying news release is being issued at the request of the Autorité des marchés financiers following a continuous disclosure review. Certain previous economics described in the Table 1 below in relation to the Project disclosed by the Company were not supported by a technical report prepared in accordance with National Instrument 43-101 Standards of Disclosure for Mineral Projects (“NI 43-101”) and are superseded by the economics set out in the current NI 43-101 report and the Company cautions the reader not to rely on such previous economics. The Company is also filing a restated version of its annual managements‘ discussion and analysis and annual information form to, as applicable, remove the unsupported technical information and qualify other disclosure.

The previous economics were made public by the Company in connection with the environmental assessment for the Cariboo Project.  These economics were prepared in accordance with the requirements for major projects in British Columbia to be assessed for potential environmental, social, economic, health and cultural effects by the Environmental Assessment Office, as required by the Environmental Assessment Act (British Columbia) (the "Environmental Assessment Act").  The previous economics do not include numbers verified to a NI 43-101 standard, and do not include the suite of investor focused economics, including the IRR and NPV for the project. These previous economics were to engineering standards. You will find below a table showing the differences between the previous economics and the economics contained in the PEA.

Further information is attached.