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Osisko Development Intercepts 54.95 G/T GOLD over 2.59 Meters IN Underground Drilling at Trixie, Tintic Project; Commences Underground Porphyry Exploration Drilling

Drill Results Exploration Programs

NYSE | TSXV: ODV NEWS RELEASE

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OSISKO DEVELOPMENT INTERCEPTS 54.95 G/T GOLD OVER 2.59 METERS IN

UNDERGROUND DRILLING AT TRIXIE, TINTIC PROJECT; COMMENCES UNDERGROUND

PORPHYRY EXPLORATION DRILLING

Montreal, Québec, October 11, 2023 – Osisko Development Corp. (NYSE: ODV, TSXV: ODV) ("Osisko

Development" or the "Company") is pleased to announce underground infill and exploration diamond

drilling ("DD") results as part of the ongoing 2023 exploration program at the Company's 100%-owned Trixie

test mine ("Trixie"), 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.

Chris Lodder, President of Osisko Development, commented, "We are excited to announce the results

of the most-recent phase of our Trixie exploration program, highlighting areas outside of our initial resource

area, and the start of our porphyry drilling campaign with an initial hole from underground at Trixie. Based

on our surface and underground geological and geochemical compilation, we have identified this as a high

priority target as a potential magmatic source to known high-grade gold and silver epithermal systems and

the surrounding anomalous copper in structures and hydrothermally altered host rocks. This target is one

of several porphyry targets we will be testing in the coming year , with the target being a non -outcropping

Bingham style porphyry copper-gold system."

DRILL ASSAY HIGHLIGHTS

This news release includes assays from 17 DD holes (refer to Table 1). Select assay highlights include:

• 7.66 grams per tonne (" g/t") gold ("Au") and 4.00 g/t silver ("Ag") over 7.32 meters ("m") in

TRXU-DD-23-035 (0.22 troy ounce per short ton ("oz/t") Au and 0.12 oz/t Ag over 24.00 feet ("ft."))

including

o 38.03 g/t Au and 7.96 g/t Ag over 1.22 m in TRXU-DD-23-035 (1.11 oz/t Au and 0.23 oz/t

Ag over 4.00 ft.)

• 14.85 g/t Au and 34.87 g/t Ag over 5.49 m in TRXU-DD-23-035 (0.43 oz/t Au and 1.02 oz/t Ag over

18.00 ft.) including

o 27.02 g/t Au and 25.70 g/t Ag over 1.83 m in TRXU-DD-23-035 (0.79 oz/t Au and 0.75 oz/t

Ag over 6.00 ft.)

• 22.54 g/t Au and 2,301.00 g/t Ag over 0.46 m in TRXU-DD-23-041 (0.66 oz/t Au and 67.11 oz/t Ag

over 1.50 ft.)

• 54.95 g/t Au and 1,143.21 g/t Ag over 2.59 m in TRXU-DD-23-045 (1.60 oz/t Au and 33.34 oz/t Ag

over 8.50 ft.) including

o 130.00 g/t Au and 2,715.00 g/t Ag over 1.07 m in TR XU-DD-23-045 (3.79 oz/t Au and

79.19 oz/t Ag over 3.50 ft.)

DRILL RESULTS SUMMARY

• In 2023, the Company has drilled 72 holes for a total of 6,125 m (20,095 ft.) at Trixie. To date,

assays have been received for 51 DD holes, with assays pending for the remaining holes. This

portion of the 2023 exploration drill program is now complete.

• Approximately 25% of the drilling to date consists of delineation of domains within the area of the

current Trixie MRE (as defined herein) and 75% is exploration drilling adjacent to the area of the

Trixie MRE, including step outs down dip, down plunge and along strike testing for mineralized

structures.

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• The focus of these recent holes was to test for mineralization along one of the priority target areas

south on strike from the known T2 domain, towards the Sioux Ajax fault (see Figure 2). A highlight

from this area includes 54.95 g/t Au and 1,143.21 g/t Ag over 2.59 m in hole TRXU -DD-23-045

(1.60 oz/t Au and 33.34 oz/t Ag over 8.50 ft.).

• A down dip highlight in the T1 domain includes 7.66 g/t Au and 4.00 g/t Ag over 7.32 m in TRXU-

DD-23-035 (0.22 oz/t Au and 0.12 oz/t Ag over 24.00 ft.). This intercept is approximately 25 m (75

ft.) from the known Trixie MRE deposit boundary.

• The 75-85 domain consists of a discrete, north -south striking, moderate to steeply west -dipping

structure in the footwall of the T4domain that was historically mined prior to the discovery of the T2

domain. See Figure 3 for domain geometry and relationships.

• The T1 domain consists of Tintic quartzite-hosted disseminated mineralization interpreted as a halo

to the T2 domain.

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

confidence level of the mineralized zones d efined in the area of the Trixie MRE and to support a

an updated mineral resource estimate ("MRE") in the future.

• The exploration results will assist with understanding the extent of mineralized structures and

support future underground exploration.

TRIXIE PORPHYRY DRILLING

• The Company is pleased to announce that drilling of the Trixie West high-priority copper-gold-

molybdenum potential porphyry target from underground at Trixie commenced in early October

2023 (see Figure 5).

• The Tintic District, located 65 km (40 miles) from Rio Tinto's Bingham Canyon Mine, has historically

been recognized as an area prospective for porphyry style copper-gold-molybdenum

mineralization. Styles of mineralization and alteration present within the Tintic District support an

interpretation of a classic porphyry-epithermal system with a high degree of rheologic and structural

control on mineralization style and distribution (Figure 4).

• The objective of the drill program is to test a new area below the Trixie deposit for a potential

porphyry style copper-gold-molybdenum mineral system that may have been the source of the

significant high -grade gold and silver epithermal mineralization and past producing carbonate

silver-lead-zinc replacement deposits.

• Two large lithocaps, presented as anomalous surface geochemical footprints, a type of high heat

signature indicative of significant potential subsurface volcanic activity, have been identified within

the Company's Tintic Project property (Figure 5), namely in the Big Hill and Silver Pass areas.

Drilling in these areas is expected to commence in Q4 2023 subject to permits.

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.

A 3D model and virtual site tour of Trixie and the wider Tintic Project is accessible on the Company's VRIFY

page at: https://vrify.com/decks/12801.

Information relating to the Tintic Project and the current MRE for the Trixie deposit (the "Trixie MRE") is

supported by the technical report entitled "NI 43-101 Technical Report, Initial M ineral 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 I nstrument 4 3-101 – Standards of

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Disclosure for Mineral Projects ("NI 43-101") and 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 www.osiskodev.com.

Figure 1: Tintic Project – Trixie Area

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Figure 2: Trixie Underground Long Section

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Figure 3: Trixie Long Section Sample Highlights

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Figure 4: Generalized Deposit Model of a high sulphidation epithermal porphyry system

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Figure 5: Lithocap Highlights Porphyry Target Areas

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Table 1: 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) Comments

TRXU-DD-23-035 66.75 67.21 0.46 2.27 11.20 219.00 220.50 1.50 0.07 0.33 Exploration T2 T4

TRXU-DD-23-035 72.54 79.86 7.32 7.66 4.00 238.00 262.00 24.00 0.22 0.12 Exploration T2 T4

TRXU-DD-23-035 Including 76.81 78.03 1.22 38.03 7.96 252.00 256.00 4.00 1.11 0.23 Exploration T2 T4

TRXU-DD-23-035 83.52 89.00 5.49 14.85 34.87 274.00 292.00 18.00 0.43 1.02 Exploration T2 T4

TRXU-DD-23-035 Including 84.67 85.50 0.82 17.28 17.01 277.80 280.50 2.70 0.50 0.50 Exploration T2 T4

TRXU-DD-23-035 and 85.50 85.95 0.46 11.09 111.00 280.50 282.00 1.50 0.32 3.24 Exploration T2 T4

TRXU-DD-23-035 and 87.17 89.00 1.83 27.02 25.70 286.00 292.00 6.00 0.79 0.75 Exploration T2 T4

TRXU-DD-23-036 Hole Abandoned

TRXU-DD-23-037 8.38 9.75 1.37 0.52 143.00 27.50 32.00 4.50 0.02 4.17 Infill T2 T4

TRXU-DD-23-038 52.43 53.49 1.07 3.12 96.25 172.00 175.50 3.50 0.09 2.81 Infill T4, 75-85

TRXU-DD-23-039 24.99 26.52 1.52 2.46 76.95 82.00 87.00 5.00 0.07 2.24 Infill 75-85

TRXU-DD-23-039 44.20 45.72 1.52 6.66 46.60 145.00 150.00 5.00 0.19 1.36 Infill 75-85

TRXU-DD-23-040 No significant assays Exploration

TRXU-DD-23-041 11.89 13.26 1.37 0.46 164.00 39.00 43.50 4.50 0.01 4.78 Exploration

TRXU-DD-23-041 37.34 40.54 3.20 5.21 735.35 122.50 133.00 10.50 0.15 21.45 Exploration

TRXU-DD-23-041 Including 38.40 38.86 0.46 22.54 2301.00 126.00 127.50 1.50 0.66 67.11 Exploration

TRXU-DD-23-042 0.00 1.37 1.37 2.98 11.15 0.00 4.50 4.50 0.09 0.33 Exploration

TRXU-DD-23-042 79.40 80.77 1.37 2.43 4.35 260.50 265.00 4.50 0.07 0.13 Exploration

TRXU-DD-23-043 No significant assays Exploration

TRXU-DD-23-044 No significant assays Exploration

TRXU-DD-23-045 36.42 39.01 2.59 54.95 1143.21 119.50 128.00 8.50 1.60 33.34 Exploration 75-85

TRXU-DD-23-045 Including 36.42 37.49 1.07 130.00 2715.00 119.50 123.00 3.50 3.79 79.19 Exploration 75-85

TRXU-DD-23-046 No significant assays Exploration

TRXU-DD-23-047 No significant assays Exploration

TRXU-DD-23-048 15.70 17.68 1.98 0.24 82.64 51.50 58.00 6.50 0.01 2.41 Exploration T4, 75-85

TRXU-DD-23-048 48.16 50.29 2.13 1.51 37.07 158.00 165.00 7.00 0.04 1.08 Exploration T4, 75-85

TRXU-DD-23-049 No significant assays Exploration

TRXU-DD-23-050 54.10 56.24 2.13 1.11 35.51 177.50 184.50 7.00 0.03 1.04 Exploration T4

TRXU-DD-23-051 No significant assays Exploration