OSISKO DEVELOPMENT REPORTS EXPLORATION RESULTS AT TRIXIE AND OUTLINES 2023 DRILL PROGRAM AT TINTIC PROJECT 62.82 g/t Au and 231.46 g/t Ag over 6.86 m including 191 g/t Au and 707 g/t Ag over 1.07 m

NYSE: ODV TSXV: ODV NEWS RELEASE

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OSISKO DEVELOPMENT REPORTS EXPLORATION RESULTS AT TRIXIE AND

OUTLINES 2023 DRILL PROGRAM AT TINTIC PROJECT

62.82 g/t Au and 231.46 g/t Ag over 6.86 m including 191 g/t Au and 707 g/t Ag over 1.07 m

Montreal, Québec, May 17, 2023 – Osisko Development Corp. (NYSE: ODV, TSXV: ODV) ("Osisko

Development" or the "Company") is pleased to announce new 2023 underground diamond drilling ("DD")

results at its 100%-owned Trixie test mine ("Trixie"), within the Company's wider Tintic Project ("Tintic" or

the "Tintic Project") and to provide an overview of the ongoing 2023 exploration program at Tintic, located

in the historic East Tintic Mining District in central Utah, U.S.A. In addition, the Company is also reporting

the remaining DD and reverse circulation drilling ("RC") results from its 2022 exploration program.

Chris Lodder, President of Osisko Development, commented, "The underground diamond drilling

results from this year's drill campaign continue to generate targets and understanding of the epithermal

veins and breccias at Trixie. High-grade gold and silver is observed in the footwall of the T2 and T1 zones,

as both disseminated and vein mineralization. As these initial results indicate, the drillholes are intersecting

all zones within the deposit area and continue to build upon the exploration successes achieved in 2022.

We are also excited to launch our initial drill campaign to target copper porphyry potential at Tintic, which

is slated to begin in Q3 2023."

DRILL ASSAY HIGHLIGHTS

This news release includes assays from 22 DD holes and 20 RC holes (refer to Tables 1 and 2). Select

assay highlights include:

• 23.49 grams per tonne ("g/t") gold ("Au") and 58.79 g/t silver ("Ag") over 1.37 meters ("m")

in hole TUG -625-106 (0.69 troy oz per short ton ("oz/t") Au and 1.71 oz/t Ag over 4.50 feet

("ft.")

• 19.54 g/t Au and 58.54 g/t Ag over 1.98 m in hole TRXU -DD-23-001 (0.57 oz/t Au and 1.71

oz/t Ag over 6.5 ft.)

• 43.44 g/t Au and 40.63 g/t Ag over 0.91 m in hole TRXU -DD-23-003 (1.27 oz/t Au and 1.19

oz/t Ag over 3.00 ft.)

• 62.82 g/t Au and 231.46 g/t Ag over 6.86 m in hole TRXU-DD-23-003 (1.83 oz/t Au and 6.75

oz/t Ag over 22.5 ft.) including

o 191.00 g/t Au and 707.00 g/t Ag over 1.07 m (5.57 oz/t Au and 20.62 oz/t Ag over 3.50 ft.)

and

o 117.00 g/t Au and 393.00 g/t Ag over 1.68 m (3.41 oz/t Au and 11.46 oz/t Ag over 5.50 ft.)

• 49.11 g/t Au and 255.00 g/t Ag over 1.07 m in hole TRXU -DD-23-003 (1.43 oz/t Au and 7.44

oz/t Ag over 3.5 ft.)

• 7.95 g/t Au and 26.12 g/t Ag over 7.32 m in hole TRXU-DD-23-005 (0.23 oz/t Au and 0.76 oz/t

Ag over 24.00 ft.)

• 10.67 g/t Au and 38.51 g/t Ag over 4.27 m in hole TRXU -DD-23-005 (0.31 oz/t Au and 1.12

oz/t Ag over 14.00 ft.)

• 28.70 g/t Au and 98.15 g/t Ag over 1.52 m in hole TRXU -DD-23-016 (0.84 oz/t Au and 2.86

oz/t Ag over 5.00 ft.)

• 7.67 g/t Au and 13.43 g/t Ag over 11.58 m in hole TRXU-DD-23-018 (0.22 oz/t Au and 0.39

oz/t Ag over 38.00 ft.) including

o 35.07 g/t Au and 19.47 g/t Ag over 1.07 m (1.02 oz/t Au and 0.57 oz/t Ag over 3.50 ft.)

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• 20.30 g/t Au and 155.00 g/t Ag over 1.52 m in hole TRC121 (0.59 oz/t Au and 4.52 oz/t Ag

over 5.00 ft)

DRILL RESULTS SUMMARY

• In 2022, the Company completed 28 surface RC drill holes near Trixie totalling approximately 8,753

m (28,718 ft.) and 66 underground DD holes in the 625 level at Trixie totalling approximately 2,985

m (9,796 ft.). Assays have now been received for all 2022 holes.

• The high-grade intercepts disclosed in this news release were targeting all domains of the current

Trixie mineral resource estimate ("Trixie MRE") (see Figure 2 and 3).

• The T1 domain consists of Tintic quartzite-hosted mineralization constrained within the footwall of

the T2 and between the T2 and 75-85 structures. The Mineralization observed is both disseminated

and in a series of discrete high-grade fissure veins.

o Hole TRXU-DD-23-003 intersected 62.82 g/t Au and 231.46 g/t Ag over 6. 86 m including

higher grade samples of 191.00 g/t Au and 707.00 g/t Ag over 1.07 m and 117.00 g/t Au

and 393.00 g/t Ag over 1.68 m.

o Hole TRXU-DD-23-005 intersected 7.95 g/t Au and 26.12 g/t Ag over 7.32 m in the T4

stockwork and fissure veins and further downhole intersected 10.67 g/t Au and 38.51 g/t

Ag over 4.27 m in the 75-85 polymetallic vein.

• These drilling results will provide valuable infill data to improve our understanding and the

confidence level of the mineralized zones defined in the Trixie MRE and to support a future mineral

resource update.

• The RC drilling was initially designed to explore ~600 m to the northeast of Trixie. Subsequent RC

holes were planned along strike to test north of the T2 zone, and further to the south to explore for

mineralized structures to be followed up with underground core drilling.

o Several of the exploration holes intersect ed anomalous precious metal values including

0.21 g/t Au and 142.0 g/t Ag over 1.52 m and 0.27 g/t Au and 40.53 g/t Ag over 16.76

meters in hole TRC053A, drilled 250 m north of T2, and potentially showing mineralized

systems along strike.

o Hole TRC121 intersected 20.3 g/t Au and 155.0 g/t Ag over 1.52 m within the T4 zone.

2023 EXPLORATION DRILLING PROGRAM

• The 2023 exploration program consists of an initial ~5,000 m (16,400 ft.) of underground exploration

and delineation drilling of the current Trixie MRE. Additional drilling is also proposed to determine

the extents of the known mineralization.

• To date, the Company has completed 35 DD holes totalling approximately 3,226 m (10,584 ft.).

The drilling is targeting all known mineralized domains and extending into the footwall to the west

to test for parallel mineralized zones. Assay results have been received for 19 DD holes, as

disclosed herein. Results for the remaining holes are pending. Currently there are two underground

diamond drill rigs in operation at Trixie conducting exploration activities.

• Approximately 75% of the 1,390 m (4,550 ft.) of the Trixie portal and underground decline ramp

has been completed to date. The Company anticipates completion of the decline ramp to the main

625 level by Q3 2023, which is expected to significantly improve underground access for

exploration drilling.

• During 2022, the exploration team completed an extensive review and compilation of historical data

on the Tintic Project. 3D models of historic al mine development, drilling, geochemical and

lithological data were integrated and, as a result, a number of high sulphidation epithermal Au-Ag

targets were identified at North Lily and Eureka Standard.

• Copper-molybdenum-gold p orphyry targets were identified at Big Hill with the integration of

historical drilling, surface geochem istry, geophysics and alteration mineralogy that defined a

lithocap approximately 2 km in strike length and 1 km wide indicative of a potential porphyry. A

strong geophysical and geochemical target was also identified to the West and depth below Trixie.

• An initial program of surface diamond drilling is planned to test the Big Hill porphyry target and is

anticipated to commence in Q3 2023. Drilling is also recommended for the Eureka Standard and

North Lily targets and will be a part of the Company’s ongoing exploration efforts.

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• A 3D model of the compilation and targets at Tintic is available by accessing the Company’s VRIFY

page at: https://vrify.com/decks/12801. The Tintic Project exploration presentation on the

Company’s website provides a high-level overview of each target.

About Trixie

The Trixie test mine is one of several gold and base metal targets within the larger Tintic Project consisting

of >17,000 acres of patented mining claims and mineral leases within the historic East Tintic Mining District

of Central Utah, U.S.A. The T2 and T4 structures at Trixie show multi-ounce gold grades associated with

high sulphidation epithermal mineralization, structurally controlled and hosted within quartzites. The T2

structure mineralization consists of native Au, and rare Au-Ag – rich telluride minerals with quartz. The T4

is a mineralized stockwork zone is located in the hanging wall of the T2 and is comprised of Au -Ag rich

mineralization in host rock quartzite with quartz-barite-sulphosalt stockwork veining. Mineralization reports

consistent multi-ounce gold grades along the entire strike length.

Information relating to the Tintic Project and the Trixie MRE is supported by the technical report titled " NI

43-101 Technical Report, Initial Mineral Resource Estimate for the Trixie Deposit, Tintic Project, Utah,

United States of America", dated January 27, 2023 (with an effective date of January 10, 2023) prepared

for the Company by independent representatives of Micon International Limited (the "Tintic Technical

Report"). Reference should be made to the full text of the Tintic Technical Report, which was prepared in

accordance with National Instrument 43-101 – Standards of Disclosure for Mineral Projects ("NI 43-101")

and is available electronically on SEDAR ( www.sedar.com) and on EDGAR (www.sec.gov) under Osisko

Development's issuer profile and on the Company's website at www.osiskodev.com.

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Figure 1: Trixie Project Area

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Figure 2: Trixie Drill Plan Map

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Figure 3: Cross Section of Underground Drilling at 625 L at Trixie

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Table 1: Diamond Drilling Length Weighted Assay Composites at Trixie

METRIC IMPERIAL

Hole ID Depth

from (m)

Depth to

(m) Length (m) Au (g/t) Ag (g/t) Depth

from (ft.)

Depth to

(ft.)

Length

(ft.) Au (oz/t) Ag (oz/t) Target

TUG-625-044 8.99 10.06 1.07 7.07 12.18 29.50 33.00 3.50 0.21 0.36 Expl. hole east of T4

TUG-625-106 3.05 4.42 1.37 23.49 58.79 10.00 14.50 4.50 0.69 1.71 T4

TRXU-DD-23-001 6.71 8.69 1.98 19.54 58.54 22.00 28.50 6.50 0.57 1.71 T4

TRXU-DD-23-001 Including 7.62 8.08 0.46 23.03 65.73 25.00 26.50 1.50 0.67 1.92 T4

TRXU-DD-23-001 and 8.08 8.69 0.61 38.30 99.72 26.50 28.50 2.00 1.12 2.91 T4

TRXU-DD-23-001 12.65 13.87 1.22 13.77 71.13 41.50 45.50 4.00 0.40 2.07 T4

TRXU-DD-23-001 Including 13.41 13.87 0.46 32.29 97.38 44.00 45.50 1.50 0.94 2.84 T4

TRXU-DD-23-001 44.96 45.57 0.61 4.23 13.21 147.50 149.50 2.00 0.12 0.39 T2 FW

TRXU-DD-23-002 No Significant Assays

TRXU-DD-23-003 31.39 32.31 0.91 43.44 40.63 103.00 106.00 3.00 1.27 1.19 T2 FW

TRXU-DD-23-003 38.25 45.11 6.86 62.82 231.46 125.50 148.00 22.50 1.83 6.75 T2 FW/T1

TRXU-DD-23-003 Including 39.47 40.54 1.07 191.00 707.00 129.50 133.00 3.50 5.57 20.62 T2 FW/T1

TRXU-DD-23-003 and 40.54 42.21 1.68 117.00 393.00 133.00 138.50 5.50 3.41 11.46 T2 FW/T1

TRXU-DD-23-003 54.71 55.78 1.07 49.11 255.00 179.50 183.00 3.50 1.43 7.44 75-85

TRXU-DD-23-005 8.53 15.85 7.32 7.95 26.12 28.00 52.00 24.00 0.23 0.76 T4

TRXU-DD-23-005 Including 8.53 9.75 1.22 19.28 55.63 28.00 32.00 4.00 0.56 1.62 T4

TRXU-DD-23-005 and 14.63 15.85 1.22 11.79 36.63 48.00 52.00 4.00 0.34 1.07 T4

TRXU-DD-23-005 23.77 28.04 4.27 10.67 38.51 78.00 92.00 14.00 0.31 1.12 75-85

TRXU-DD-23-005 Including 24.69 25.91 1.22 21.33 48.75 81.00 85.00 4.00 0.62 1.42 75-85

TRXU-DD-23-005 and 25.91 26.82 0.91 10.19 65.16 85.00 88.00 3.00 0.30 1.90 75-85

TRXU-DD-23-006 90.22 90.68 0.46 2.00 22.39 296.00 297.50 1.50 0.06 0.65 T2 FW/T1

TRXU-DD-23-007 21.95 23.47 1.52 4.59 15.65 72.00 77.00 5.00 0.13 0.46 75-85

TRXU-DD-23-008 0.00 1.52 1.52 2.84 41.07 0.00 5.00 5.00 0.08 1.20 T4

TRXU-DD-23-008 2.44 3.96 1.52 2.39 23.33 8.00 13.00 5.00 0.07 0.68 T4

TRXU-DD-23-008 18.59 20.73 2.13 1.98 93.82 61.00 68.00 7.00 0.06 2.74 75-85

TRXU-DD-23-009 Hole abandoned

TRXU-DD-23-010 No Significant Assays

TRXU-DD-23-011 57.45 60.05 2.59 3.21 31.43 188.50 197.00 8.50 0.09 0.92 T4

TRXU-DD-23-012 62.64 63.09 0.46 2.50 38.31 205.50 207.00 1.50 0.07 1.12 75-85 HW

TRXU-DD-23-013 92.66 95.71 3.05 6.59 61.96 304.00 314.00 10.00 0.19 1.81 75-85/T1

TRXU-DD-23-014 No Significant Assays

TRXU-DD-23-015 43.89 46.94 3.05 1.59 65.23 144.00 154.00 10.00 0.05 1.90 T2 FW/T1

TRXU-DD-23-016 123.14 124.66 1.52 28.70 98.15 404.00 409.00 5.00 0.84 2.86 T1

TRXU-DD-23-017 32.92 33.68 0.76 3.52 0.15 108.00 110.50 2.50 0.10 0.00 T4

TRXU-DD-23-018 75.59 77.11 1.52 21.81 26.35 248.00 253.00 5.00 0.64 0.77 T1

TRXU-DD-23-018 75.59 87.17 11.58 7.67 13.43 248.00 286.00 38.00 0.22 0.39 T1

TRXU-DD-23-018 Including 75.59 77.11 1.52 21.81 26.35 248.00 253.00 5.00 0.64 0.77 T1

TRXU-DD-23-018 and 86.11 87.17 1.07 35.07 19.47 282.50 286.00 3.50 1.02 0.57 T1

TRXU-DD-23-019 152.40 156.67 4.27 4.03 21.82 500.00 514.00 14.00 0.12 0.64 T1

TRXU-DD-23-019 Including 152.40 153.62 1.22 7.09 39.62 500.00 504.00 4.00 0.21 1.16 T1

TRXU-DD-23-020 82.9056 84.7344 1.8288 4.41 105.74 272.00 278.00 6.00 0.13 3.08 T2

TRXU-DD-23-020 Including 84.12 84.73 0.61 9.57 200.00 276.00 278.00 2.00 0.28 5.83 T2

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Table 2: Reverse Circulation Length Weighted Assay Composites at Trixie

METRIC IMPERIAL

Hole ID Depth

from (m)

Depth to

(m)

Length

(m) Au (g/t) Ag (g/t) Depth

from (ft.)

Depth to

(ft.)

Length

(ft.) Au (oz/t) Ag (oz/t) Target

TRC038A Hole Abandoned Exploration

TRC038A 359.66 362.71 3.05 3.47 3.55 1180.00 1190.00 10.00 0.10 0.10 Exploration

TRC039 359.66 371.86 12.19 1.41 1.88 1180.00 1220.00 40.00 0.04 0.05 Exploration- 400 m north of T2

TRC043A No Samples Exploration

TRC051 153.92 158.50 4.57 0.37 168.00 505.00 520.00 15.00 0.01 4.90 Exploration

TRC053 Hole Abandoned Exploration

TRC053A 208.79 210.31 1.52 0.22 88.30 685.00 690.00 5.00 0.01 2.58 Exploration

TRC053A 275.84 277.37 1.52 0.21 142.00 905.00 910.00 5.00 0.01 4.14 Exploration

TRC053A 359.66 376.43 16.76 0.27 40.53 1180.00 1235.00 55.00 0.01 1.18 Exploration

TRC053A Including 359.66 361.19 1.52 0.27 98.00 1180.00 1185.00 5.00 0.01 2.86 Exploration

TRC053A and 364.24 365.76 1.52 0.16 61.50 1195.00 1200.00 5.00 0.00 1.79 Exploration

TRC053A and 370.33 371.86 1.52 1.04 62.60 1215.00 1220.00 5.00 0.03 1.83 Exploration

TRC069 No Significant Assays T4

TRC070 No Significant Assays T2-T4

TRC071 Hole Abandoned T2-T4

TRC071A Hole Abandoned T2-T4

TRC087 Hole Abandoned 75-85

TRC088 No Samples Volcanics, ophir shale

TRC094 309.37 310.90 1.52 0.11 37.20 1015.00 1020.00 5.00 0.00 1.09 T4

TRC094A No Significant Assays 75-85

TRC095 No Significant Assays Volcanics

TRC121 225.55 249.94 24.38 2.70 29.29 740.00 820.00 80.00 0.08 0.85 T4

TRC121 Including 248.41 249.94 1.52 20.30 155.00 815.00 820.00 5.00 0.59 4.52 T4

TRC122 No Samples

TRC123 208.79 210.31 1.52 0.36 63.40 685.00 690.00 5.00 0.01 1.85 T4

TRC123 274.32 280.42 6.10 0.17 43.29 900.00 920.00 20.00 0.01 1.26 T4

TRC123 Including 274.32 275.84 1.52 0.42 96.40 900.00 905.00 5.00 0.01 2.81 T4

TRC124 Hole Abandoned T4

TRC124A 268.22 269.75 1.52 0.02 63.10 880.00 885.00 5.00 0.00 1.84 T2 FW/T1

TRC124A 396.24 397.76 1.52 1.50 16.50 1300.00 1305.00 5.00 0.04 0.48 T2 FW/T1