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Osisko Development Files Technical Report ON Mineral Resource

Resource Estimates Technical Reports (NI 43-101)

NYSE | TSXV: ODV NEWS RELEASE

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OSISKO DEVELOPMENT FILES TECHNICAL REPORT ON MINERAL RESOURCE

ESTIMATE FOR THE TRIXIE DEPOSIT, TINTIC PROJECT

Montreal, Québec, April 26 , 202 4 – Osisko Development Corp. (NYSE: ODV, TSXV: ODV)

("Osisko Development" or the "Company") announces the filing of a technical report (the "Technical

Report") for the updated mineral resource estimate (" MRE") on its 100%-owned underground Trixie

deposit (the " 2024 Trixie MRE"), within the Company's wider Tintic Project (" Tintic" or the " Tintic

Project"), located in the historic East Tintic Mining District in central Utah, U.S.A . Highlights from the

previously-announced 2024 Trixie MRE disclosed in the Company's news release dated March 15, 2024

are presented below, and are consistent with the Technical Report.

The Technical Report, titled "NI 43 -101 Technical Report, Mineral Resource Estimate for the Trixie

Deposit, Tintic Project, Utah, United States of America" and dated April 25, 2024 (with an effective date

of March 14 , 202 4), was prepared for the Company by independent representatives of Micon

International Limited in accordance with National Instrument 43 -101 – Standards of Disclosure for

Mineral Projects ("NI 43-101"). Reference should be made to the full text of the Technical Report,

which is available electronically on SEDAR+ (www.sedarplus.ca) and on EDGAR ( www.sec.gov) under

Osisko Development's issuer profile and on the Company's website at https://osiskodev.com/tintic-

project.

2024 TRIXIE MINERAL RESOURCE ESTIMATE

Table 1: 2024 Trixie MRE (all zones) – March 14, 2024

Classification Tonnes

(000's)

Au Grade

(g/t)

Contained

Gold

(000's oz)

Ag Grade

(g/t)

Contained

Silver

(000's oz)

Measured 120 27.36 105 61.73 238

Indicated 125 11.17 45 59.89 240

Measured and Indicated 245 19.11 150 60.80 478

Inferred 202 7.80 51 48.55 315

Notes (applicable to Tables 1, 2, and 3)

1. Effective date of the 2024 Trixie MRE is March 14, 2024.

2. Each of Mr. William Lewis , P.Geo., of Micon International Limited and Alan J . San Martin, MAusIMM(CP), of Micon

International Limited (i) has reviewed and validated the 2024 Trixie MRE, (ii) is considered to be independent of the

Company for purposes of Section 1.5 of National Instrument 43 -101 – Standards of Disclosure for Mineral Projects ("NI

43-101"), and (iii) is a "qualified person" within the meaning of NI 43-101.

3. The mineral resources were estimated using the Canadian Institute of Mining (" CIM"), Metallurgy and Petroleum's "CIM

Definition Standards on Mineral Resources and Mineral Reserves" adopted by the CIM council.

4. Mineral resources are reported when they are within potentially mineable shapes derived from a stope optimizer algorithm,

assuming an underground longhole stoping mining method with stopes of 6.1 m x 6.1 m x minimum 1.5 m dimensions.

5. Mineral resources that are not mineral reserves do not have demonstrated economic viability.

6. Geologic modelling was completed by Osisko Development modeling geologist Jody Laing, P.Geo, using Leapfrog Geo

software. The 2024 Trixie MRE was completed by Osisko Development chief resource geologist, Daniel Downton, P.Geo

using Datamine Studio RM 2.0 software. William Lewis and Alan J. San Martin of Micon International Limited independently

reviewed and validated the mineral resource model.

7. The estimate is reported for an underground mining scenario and with USD assumptions. The cut -off grade of 4.32 g/t Au

was calculated using a gold price of US $1,750/oz, a CAD:USD exchange rate of 1.3 0; total mining, processing and G&A

costs of US $168.04/imperial ton ; a refining cost of US $2.65/ounce; a combined royalty of 4.5 0%; and an average

metallurgical gold recovery of 80%.

8. The stope optimizer algorithm evaluated the resources based on a gold equivalent grade which incorporates the silver grade

estimate and assumes a silver price of US$23/oz and metallurgical silver recovery of 45%.

9. The 2024 Trixie MRE is comprised of six zones within the greater Trixie area: T2, T3, T4, Wild Cat, 40 Fault and 75 -85.

10. Average bulk density values in the mineralized domains were assigned to the T2 (2.955 T/m 3), T3 (2.638 T/m3), T4(2.618

T/m3), Wild Cat, and 40 Fault (2.621 T/m3), and 75-85 (2.617 T/m3) domains.

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11. Inverse Distance Squared interpolation method was used with a parent block size of 1.2 m x 2.4 m x 2.4 m.

12. The 2024 Trixie MRE results are presented in -situ. Calculations used metric units (metres, tonnes, g/t). The number of

tonnes is rounded to the nearest thousand. Any discrepancies in the totals are due to rounding effects.

13. Neither the Company nor Micon International Limited is aware of any known environmental, permitting, legal, title-related,

taxation, socio-political, marketing or other relevant issue that could materially affect the mineral resource estimate other

than disclosed in this news release.

14. Technical information in this news release differs from similar information made public by U.S. companies subject to the

reporting and disclosure requirements of the U.S. Securities and Exchange Commission. See below under "Cautionary

Statement to U.S. Investors".

Table 2: 2024 Trixie MRE Separated by Domain – March 14, 2024

Domain Category Tonnes Grade

(Au g/t)

Contained

Gold (oz)

Grade

(Ag g/t)

Contained

Silver (oz)

T2

Measured 22,678 106.27 77,484 115.99 84,572

Indicated 11,939 23.19 8,902 51.07 19,602

M+I 34,617 77.62 86,387 93.60 104,173

Inferred 1,996 9.82 630 61.38 3,938

T3

Measured 2,385 9.46 725 75.34 5,776

Indicated 970 5.47 171 57.32 1,787

M+I 3,355 8.30 896 70.13 7,564

Inferred 139 6.27 28 63.14 282

T4 +

Wild

Cat +

40 FLT

Measured 94,784 8.93 27,227 48.41 147,520

Indicated 51,827 6.48 10,795 37.59 62,637

M+I 146,611 8.07 38,023 44.58 210,156

Inferred 104,676 6.57 22,127 38.57 129,792

75-85

Measured - - -

Indicated 60,008 12.93 24,943 80.95 156,185

M+I 60,008 12.93 24,943 80.95 156,185

Inferred 94,793 9.12 27,784 59.28 180,666

Total

Measured 119,847 27.36 105,437 61.73 237,868

Indicated 124,743 11.17 44,811 59.89 240,211

M+I 244,590 19.11 150,248 60.80 478,078

Inferred 201,603 7.80 50,569 48.55 314,678

Refer to notes described under Table 1, which are also applicable to Table 2 in their entirety.

Table 3: Trixie MRE Cut-Off Grade ("COG") Sensitivity (Base Case in Bold) – March 14, 2024

Classification Tonnes COG Grade

(Au g/t)

Contained

Gold (oz)

Grade

(Ag g/t)

Contained

Silver (oz)

Measured +

Indicated

366,130 2.50 13.79 162,348 50.18 590,666

324,251 3.00 15.23 158,722 53.31 555,740

291,005 3.50 16.64 155,716 56.19 525,681

261,219 4.00 18.14 152,350 58.95 495,091

244,590 4.32 19.11 150,248 60.80 478,078

237,143 4.50 19.58 149,266 61.52 469,058

217,327 5.00 20.99 146,677 64.07 447,646

198,538 5.50 22.55 143,909 66.19 422,504

182,842 6.00 24.01 141,164 68.57 403,074

165,955 6.50 25.81 137,734 71.39 380,902

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152,986 7.00 27.55 135,503 74.34 365,663

Inferred

438,189 2.50 5.26 74,056 34.46 485,528

342,880 3.00 5.99 66,034 38.38 423,112

279,722 3.50 6.65 59,767 41.84 376,306

224,039 4.00 7.42 53,438 46.31 333,578

201,603 4.32 7.80 50,569 48.55 314,678

190,002 4.50 8.02 49,009 49.90 304,803

163,894 5.00 8.60 45,313 53.08 279,718

141,728 5.50 9.16 41,742 55.92 254,818

123,472 6.00 9.71 38,532 58.70 233,028

106,080 6.50 10.35 35,291 60.43 206,087

91,725 7.00 10.99 32,397 61.91 182,579

Note: Micon International Limited' s "qualified person" (for purposes of NI 43 -101) has reviewed the COG used in the sensitivity

analysis relating to the 2024 Trixie MRE and is of the opinion that the individual cut -off grades used in the sensitivity analysis meet

the test of reasonable prospects of economic extraction. The numbers in bold represent the current 2024 Trixie MRE.

Table 4: Trixie MRE Cut-off Grade Calculation Breakdown

PARAMETERS VALUES

Mining Cost ($/ST) $74.33

G&A ($/ST) $52.71

Heap Leach ($/ST) $41.00

Total Refining Cost/ OZ $2.65

Gold Price $1,750

Royalty (Combination) 4.50%

Heap Leach Au Recovery 80.0%

Cut-off Grade (COG) 4.32

Qualified Persons

The scientific and technical information contained in this news release has been reviewed and approved

by Maggie Layman, P.Geo., Vice President, Exploration of Osisko Development, and a "qualified person"

within the meaning of NI 43-101 ("QP").

The independent QPs for the 2024 Trixie MRE, within the meaning of NI 43-101, are William Lewis,

P.Geo. and Alan J. San Martin MAusIMM(CP) of Micon International Limited. Each QP is independent of

Osisko Development within the meaning of NI 43 -101 and has reviewed and approved the content in

this news release.

Quality Assurance (QA) – Quality Control (QC)

All drill core and exploration samples are dispatched to ALS Geochemistry or SGS Canada for offsite

sample preparation and analysis. Both labs are ISO/IEC 17025 certified, and ALS Geochemistry is also

ISO 9001 certified. Samples are assigned a unique sample ID. All geological and sampling information

is entered into a Datamine Fusion database. Core is sawn in half and half is sampled. Certified standards

and blanks are inserted into all sample dispatches. Samples are collected by Old Dominion

Transportation and dispatched to SGS Canada 's laboratory in Burnaby, British Columbia or ALS

Geochemistry’s laboratories in Elko, Nevada or Twin Falls, Idaho. Sample submission forms accompany

the samples, and digital copies are emailed to the destination lab.

Core sample preparation is completed by ALS Geochemistry or SGS Canada, including drying, crushing,

and pulverizing of samples. Analytical assays include gold by 30 -gram fire assay with AAS finish, and

gold overlimits by fire assay with gravimetric finish. Screen metallic analyses are performed on selected

samples. Multielement analysis (including silver) is by four-acid digest with ICP-AES/ICP-MS finish. The

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pulps are returned to Osisko Development and coarse rejects are disposed after 90 days. Assays are

reported to Osisko Development and then loaded into Datamine Fusion. Quality Assurance -Quality

Control samples are checked, and assays are merged with sample information for future reporting.

Underground face samples are collected by Company geologists from each of the active mining faces,

with samples transported by the geologists from Trixie to the on-site Company laboratory located at the

Burgin administrative complex. Underground samples are dried, crushed to <10 mm and a 250 g split

is taken. The split is pulverized, and a 30 g Fire Assay with gravimetric finish is completed to determine

gold and silver grades, reported in oz/short ton and g/t.

The Company's Burgin laboratory is not a certified analytical laboratory, but the facility is managed by

a qualified laboratory manager with annual auditing by technical staff. The laboratory has been

independently audited by Qualit ica Consulting and Micon International Limited's QP with

recommendations implemented. Inter-laboratory check assays using ALS Geochemistry as a third-party

independent analysis of samples is routinely carried out as part of ongoing QA/QC work. Certified OREAS

QC standards and bla nks are inserted at regular intervals in the sample stream to monitor laboratory

performance.

True width is estimated to be approximately 0.5 m - 3 m (1.6 - 10 ft) for all fissure veins and discrete

structures (T2, T3, 75-85, Wildcat and 40 Fault) and the T4 zone is modelled at an average width of 90

m (300 ft) and encompasses disseminated mineralization and discontinuous veins ranging from several

cm to 1 m (3 ft).

ABOUT OSISKO DEVELOPMENT CORP.

Osisko Development Corp. is a North American gold development company focused on past -producing

mining camps located in mining friendly jurisdictions with district scale potential. The Company 's

objective is to become an intermediate gold producer by advancing its 100%-owned Cariboo Gold

Project, located in central B .C., Canada, the Tintic Project in the historic East Tintic mining district in

Utah, U.S.A., and the San Antonio Gold Project in Sonora, Mexico. In addition to considerable brownfield

exploration potential of these properties, that benefit from significant hi storical mining data, existing

infrastructure and access to skilled labour, the Company 's project pipeline is complemented by other

prospective exploration properties. The Company 's strategy is to dev elop attractive, long-life, socially

and environmentally sustainable mining assets, while minimizing exposure to development risk and

growing mineral resources.

For further information, visit our website at www.osiskodev.com or contact:

Sean Roosen Philip Rabenok

Chairman and CEO Director, Investor Relations

Email: [email protected] Email: [email protected]

Tel: +1 (514) 940-0685 Tel: +1 (437) 423-3644

CAUTIONARY STATEMENTS

Cautionary Statement Regarding Estimates of Mineral Resources

This news release uses the terms measured, indicated and inferred mineral resources as a relative measure of the level of confidence

in the resource estimate. Readers are cautioned that mineral resources are not mineral reserves and that the economic viabi lity of

resources that are not mineral reserves has not been demonstrated. The mineral resource estimate disclosed in this news relea se

may be materially affected by geology, environmental, permitting, legal, title, socio-political, marketing or other relevant issues. The

mineral resource estimate is classified in accordance with the Canadian Institute of Mining, Metallurgy and Petroleum's "CIM Definition

Standards on Mineral Resources and Mineral Reserves" incorporated by reference into NI 43-101. Under NI 43 -101, estimates of

inferred mineral resources may not form the basis of feasibility or pre -feasibility studies or economic studies except for preliminary

economic assessments. Readers are cautioned not to assume that further work on the stated resources will lead to mineral reserves

that can be mined economically.

Cautionary Statement Regarding Test Mining Without Feasibility Study

The Company cautions that its prior decision to commence small -scale underground mining activities and batch vat leaching at the

Trixie test mine was made without the benefit of a feasibility study, or reported mineral resources or mineral reserves, demonstrating

economic and technical viability, and, as a result there may be increased uncertainty of achieving any particular level of re covery of

material or the cost of such recovery. The Company cautions that historically, such projects have a much higher risk of economic and

technical failure. Small scale test -mining at Trixie was suspended in December 2022 , resumed in the second quarter of 2023 , and

suspended once again in December 2023 . If and when small-scale test-mining recommences at Trixie, there is no guarantee that

production will continue as anticipated or at all or that anticipated production costs will be achieved. The failure to continue production

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may have a material adverse impact on the Company's ability to generate revenue and cash flow to fund operations. Failure to

achieve the anticipated production costs may have a material adverse impact on the Company's cash flow and potential profitab ility.

In continuing operations at Trixie after closing, the Company has not based its decision to continue such operations on a feasibility

study, or reported mineral resources or mineral reserves demonstrating economic and technical viability.

Cautionary Statement to U.S. Investors

The Company is subject to the reporting requirements of the applicable Canadian securities laws and as a result reports infor mation

regarding mineral properties, mineralization and estimates of mineral reserves and mineral resources, including the information in its

technical reports, financial statements, MD&A and this news release, in accordance with Canadian reporting requirements, whic h are

governed by NI 43-101. As such, such information concerning mineral properties, mineralization and estimates of mi neral reserves

and mineral resources, including the information in its technical reports, financial statements, MD&A and this news release, is not

comparable to similar information made public by U.S. companies subject to the reporting and disclosure requi rements of the U.S.

Securities and Exchange Commission ("SEC").

CAUTION REGARDING 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 (together, "forward -looking statements"). 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 condit ional,

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 the assumptions,

qualifications and limitations relating to the significance of the high -priority target drilling; the utility of mod ern exploration

techniques; the potential for parallel high -grade gold fissure zones; the potential of Tintic to host a copper -gold porphyry center;

the significance of regional exploration potential; the results of the 2024 Trixie MRE; the capital resourc es available to Osisko

Development; the ability of the Company to execute its planned activities; the ability of the Company to obtain future financing and

the terms of such financing; management's perceptions of historical trends, current conditions and e xpected future developments;

the utility and significance of historic data, including the significance of the district hosting past producing mines; futur e mining

activities; unique mineralization at Trixie; the potential of high -grade gold mineralization on Trixie; the potential for unknown

mineralized structures to extend existing zones of mineralization; category conversion; the timing and status of permitting; the

results (if any) of further exploration work to define and expand mineral resources; the ability of exploration work (including drilling

and chip sample assays, and face sampling methodologies) to accurately predict mineralization; the ability to generate additi onal

drill targets; the ability of management to understand the geology and potentia l of the Company's properties; the ability of the

Company to expand mineral resources beyond current mineral resource estimates; the ability of the Company to complete its

exploration objectives for its projects in 2024 in the timing contemplated (if at all); the ongoing advancement of the deposits on the

Company's properties; the deposit remaining open for expansion at depth and down plunge; the ability to realize upon any

mineralization in a manner that is economic; the ability to adapt to changes in gold prices, estimates of costs, estimates of planned

exploration and development expenditures; the ability of the Company to obtain further capital on reasonable terms; assay res ults

presented in this news release; the profitability (if at all) of the Company 's operations; the Company being a well -positioned gold

development company in Canada, USA and Mexico; sustainability and environmental impacts of operations at the Company's

properties; as well as other considerations that are believed to be appropriate i n 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, the ability of exploration (including drilling and chip sample assays, and face sampling) to accurately

predict mineralization, budget constraints and access to capital on terms acceptable to the Company, current conditions and expected

future developments, regulatory framework remaining defined and underst ood, 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. Osisk o

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 Osi sko Development and its business. Such risks and

uncertainties include, among others, risks relating to capital market conditions and the Company's ability to access capital on terms

acceptable to the Company for the contemplated exploration and developmen t at the Company's properties; the ability to continue

current operations and exploration; regulatory framework and presence of laws and regulations that may impose restrictions on

mining; the ability of exploration activities (including drill and chip sam pling, and face sampling results) to accurately predict

mineralization; errors in management's geological modelling; the ability to expand operations or complete further exploration

activities, including drilling and chip sample assays and face sampling; t he timing and ability of the Company to obtain required

approvals and permits; the results of exploration activities; risks relating to exploration, development and mining activitie s; the

global economic climate; metal and commodity prices; fluctuations in the currency markets; dilution; environmental risks; and

community, non-governmental and governmental actions and the impact of stakeholder actions. Readers are urged to consult the

disclosure provided under the heading "Risk Factors" in the Company's ann ual information form for the year ended December 31,

2023 as well as the financial statements and MD&A for the year ended December 31, 202 3, which have been filed on SEDAR+

(www.sedarplus.ca) 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 ava ilable as of the date hereof, no

assurances can be given as to future results, levels of activity and achievements. The Company disclaims any obligation to up date

any forward-looking statements, whether as a result of new information, future events or resu lts or otherwise, except as required

by law. Forward-looking statements are not guarantees of performance and there can be no assurance that these forward -looking

statements will prove to be accurate, as actual results and future events could differ materi ally 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.