Summary

• Results released below are from holes IM-21-155 to IM-21-203. Figures 1 and 2 illustrate drillhole location maps.
• A total of 60,272 meters were drilled in 163 holes at the Shaft Zone on Island Mountain in 2021. A total of 10,355 m were drilled in 40 holes at Mosquito Creek on Island Mountain. The final Mosquito Results were reported in a news release on December 7, 2021.
• All holes reported were collared on Shaft Zone, and six holes intersected the Valley Zone deposit at depth, on the east side of the Jack of Clubs fault. See Figure 2 for deposit outlines and Table 1 for detailed results.
• Shaft Zone highlights include 81 g/t Au over 9.80 meters in hole IM-21-184 including a high grade sample of 193.00 g/t Au over 0.90 meter.
• Drillhole IM-21-201, collared on Shaft Zone, but drilling through to Valley zone at a depth of 391 meters down hole (250 meters from surface) intersected a mineralized vein corridor at Valley that assayed 55 g/t Au over 9.65 meters including a high grade sample of 224.00 g/t Au over 0.55 meters.
• Additional high grade samples include 00 g/t Au over 0.50 meter, 159.00 g/t Au over 0.55 meter, 105.00 g/t Au over 0.50 meter, 104.00 g/t Au over 0.50 meter, 130.00 g/t Au over 0.80 meter, 102.50 g/t Au over 0.55 meter and 187.00 g/t Au over 0.60 meter.
• The drill results show continuity of vein corridors from Shaft Zone to Valley Zone along the south east of Shaft, at depth and down plunge into Valley Zone. The Shaft and Valley Zones are separated by the Jack of Clubs fault however mineralized vein corridors are continuous across the fault within the prospective sandstone unit.
• Detailed drilling results and a drill hole location plan map are presented at the end of this release.

Assay Highlights

·         85.35 g/t Au over 1.00 meter in hole IM-21-155 including

·         101.00 g/t Au over 0.50 meter

·         18.80 g/t Au over 6.70 meters in hole IM-21-159 including

·         159.00 g/t Au over 0.55 meter

·         39.87 g/t Au over 1.65 meters in hole IM-21-159 including

·         53.50 g/t Au over 1.15 meters

·         33.44 g/t Au over 2.10 meters in hole IM-21-161 including

·         75.80 g/t Au over 0.90 meter

·         10.22 g/t Au over 7.90 meters in hole IM-21-165

·         12.35 g/t Au over 5.50 meters in hole IM-21-166 including

·         105.00 g/t Au over 0.50 meter

·         65.90 g/t Au over 0.90 meter in hole IM-21-166

·         21.14 g/t Au over 5.70 meters in hole IM-21-170 including

·         104.00 g/t Au over 0.50 meter

·         37.76 g/t Au over 2.00 meters in hole IM-21-171 including

·         91.20 g/t Au over 0.70 meter

·         10.09 g/t Au over 5.00 meters in hole IM-21-171

·         54.04 g/t Au over 1.25 meters in hole IM-21-174 including

·         85.50 g/t Au over 0.75 meter

·         12.93 g/t Au over 4.75 meters in hole IM-21-176

·         14.10 g/t Au over 7.80 meters in hole IM-21-176

·         23.61 g/t Au over 5.80 meters in hole IM-21-176 including

·         130.00 g/t Au over 0.80 meter

·         30.43 g/t Au over 2.05 meters in hole IM-21-178

·         16.14 g/t Au over 3.35 meters in hole IM-21-181

·         26.94 g/t Au over 2.40 meters in hole IM-21-182 including

·         102.50 g/t Au over 0.55 meter

·         19.81 g/t Au over 9.80 meters in hole IM-21-184 including

·         193.00 g/t Au over 0.90 meter

·         58.60 g/t Au over 1.00 meter in hole IM-21-185

·         20.04 g/t Au over 4.75 meters in hole IM-21-190

·         40.70 g/t Au over 1.50 meters in hole IM-21-191

·         71.85 g/t Au over 2.05 meters in hole IM-21-192 including

·         187.00 g/t Au over 0.60 meter

·         24.55 g/t Au over 9.65 meters in hole IM-21-201 including

·         224.00 g/t Au over 0.55 meter and

·         68.90 g/t Au over 1.15 meters

Maggie Layman, Vice President of Exploration of Osisko Development commented: “We are pleased to report the remaining drill results from our 2021 exploration and category conversion drill campaign. The Shaft Zone and the Valley Zone are separated by the Jack of Clubs fault, a brittle fault structure striking north east and dipping approximately 50 degrees to the west. The 2021 drill campaign indicated vein corridors continuous on both sides of the fault and mineralized zones within the fault, indicating that the Shaft Zone vein corridors continue down plunge within the sandsone and are currently modelled to a depth of 560 meters from surface. The mineralized system remains open down plunge within the sandstone.”

Vein corridors are defined as high-density networks of mineralized quartz veins within the axis of the deposit’s last folding event. These mineralized structures are predominantly hosted within a brittle meta-sandstone or calcareous meta-sandstone. Vein corridors are modelled at a minimum thickness of 2.00 meters and average approximately 4.50 meters true width. Individual mineralized veins within these corridors have widths varying from centimeters to several meters and strike lengths from a few meters to over 50 meters. These corridors have been defined from surface to a vertical depth averaging 300 meters and remain open for expansion at depth and along strike. Gold grades are intimately associated with quartz vein-hosted pyrite as well as pyritic, intensely silicified wall rock vein selvages.

True widths are estimated to be 60% to 75 % of reported core length intervals. Intervals not recovered by drilling were assigned zero grade. Top cuts have not been applied to high grade assays. Complete assay highlights are presented in Table 1 and drill hole locations are listed in Table 2.

Qualified Persons

Per National Instrument 43-101 Standards of Disclosure for Mineral Projects, Maggie Layman, P.Geo. Vice President Exploration of Osisko Development Corp., is a Qualified Person and has prepared, validated, and approved the technical and scientific content of this news release.

Quality Assurance – Quality Control

Once received from the drill and processed, all drill core samples are sawn in half, labelled and bagged.  The remaining drill core is subsequently stored on site at a secured facility in Wells, BC.  Numbered security tags are applied to lab shipments for chain of custody requirements.  Quality control (“QC”) samples are inserted at regular intervals in the sample stream, including blanks and reference materials with all sample shipments to monitor laboratory performance. The QAQC program was designed and approved by Lynda Bloom, P.Geo. of Analytical Solutions Ltd.

Drill core samples are submitted to ALS Geochemistry’s analytical facility in North Vancouver, British Columbia for preparation and analysis. The ALS facility is accredited to the ISO/IEC 17025 standard for gold assays and all analytical methods include quality control materials at set frequencies with established data acceptance criteria. The entire sample is crushed, and 250 grams is pulverized. Analysis for gold is by 50g fire assay fusion with atomic absorption (“AAS”) finish with a lower limit of 0.01 ppm and upper limit of 100 ppm. Samples with gold assays greater than 100 ppm are re-analyzed using a 1,000g screen metallic fire assay. A selected number of samples are also analyzed using a 48 multi-elemental geochemical package by a 4-acid digestion, followed by Inductively Coupled Plasma Atomic Emission Spectroscopy (“ICP-AES”) and Inductively Coupled Plasma Mass Spectroscopy (“ICP-MS”).

About Osisko Development Corp.

Osisko Development Corp. is uniquely positioned as a premier gold development company in North America to advance the Cariboo Gold Project and other properties in the USA and Mexico, with the objective of becoming the next mid-tier gold producer. The Cariboo Gold Project, located in central British Columbia, Canada, is Osisko Development’s flagship asset. The considerable exploration potential at depth and along strike distinguishes the Cariboo Gold Project relative to other development assets. Osisko Development’s project pipeline is complemented by its interest in the San Antonio gold project, located in Sonora, Mexico and the Trixie gold test mine, located in Utah, U.S.A.

For further information about Osisko Development (ODV: TSX-V, NYSE), please visit www.osiskodev.com or contact Osisko Development Corp.:

Jean Francois Lemonde
VP Investor Relations
jflemonde@osiskodev.com
Tel: 514-299-4926

In Europe:
Swiss Resource Capital AG
Jochen Staiger
info@resource-capital.ch
www.resource-capital.ch

Forward-looking Statements

Certain statements contained in this news release may be deemed "forward-looking statements" within the meaning of the United States Private Securities Litigation Reform Act of 1995 and "forward-looking information" within the meaning of applicable Canadian securities legislation. These forward‐looking statements, by their nature, require Osisko Development to make certain assumptions and necessarily involve known and unknown risks and uncertainties that could cause actual results to differ materially from those expressed or implied in these forward‐looking statements. Forward‐looking statements are not guarantees of performance. Words such as "may", "will", "would", "could", "expect", "believe", "plan", "anticipate", "intend", "estimate", "continue", or the negative or comparable terminology, as well as terms usually used in the future and the conditional, are intended to identify forward‐looking statements. Information contained in forward‐looking statements is based upon certain material assumptions that were applied in drawing a conclusion or making a forecast or projection, including management’s perceptions of historical trends, current conditions and expected future developments, results of further exploration work to define and expand mineral resources, and that the deposit remains open for expansion at depth and down plunge, as well as other considerations that are believed to be appropriate in the circumstances, and any other information herein that is not a historical fact may be "forward looking information". Material assumptions also include, management’s perceptions of historical trends, current conditions and expected future developments, results of further exploration work to define or expand any mineral resources, as well as other considerations that are believed to be appropriate in the circumstances. Osisko Development considers its assumptions to be reasonable based on information currently available, but cautions the reader that their assumptions regarding future events, many of which are beyond the control of Osisko Development, may ultimately prove to be incorrect since they are subject to risks and uncertainties that affect Osisko Development and its business. Such risks and uncertainties include, among others, risks relating to capital market conditions, the ability to continue current production, regulatory framework, the ability of exploration activities (including drill results) to accurately predict mineralization; errors in management’s geological modelling; the ability of to complete further exploration activities, including drilling; property and stream interests in the Project; the ability of the Company to obtain required approvals; the results of exploration activities; risks relating to exploration, development and mining activities; the global economic climate; metal prices; dilution; environmental risks; and community and non-governmental actions and the responses of relevant governments to the COVID-19 outbreak and the effectiveness of such responses. Readers are urged to consult the disclosure provided under the heading "Risk Factors" in the Company’s annual information form for the year ended December 31, 2021, as amended, which has been filed on SEDAR (www.sedar.com) under Osisko Development’s issuer profile and on the SEC’s EDGAR website (www.sec.gov), for further information regarding the risks and other factors applicable to the exploration results. Although the Company’s believes the expectations conveyed by the forward-looking statements are reasonable based on information available at the date of preparation, no assurances can be given as to future results, levels of activity and achievements. The Company disclaims any obligation to update any forward-looking statements, whether as a result of new information, future events or results or otherwise, except as required by law. There can be no assurance that these forward-looking statements will prove to be accurate, as actual results and future events could differ materially from those anticipated in such statements. Accordingly, readers should not place undue reliance on forward-looking statements.

Neither the TSX Venture Exchange nor its Regulation Services Provider (as that term is defined in the policies of the TSX Venture Exchange) accepts responsibility for the adequacy or accuracy of this news release. No stock exchange, securities commission or other regulatory authority has approved or disapproved the information contained herein.