Mr. Sean Roosen reports

OSISKO DEVELOPMENT INTERCEPTS 610 G/T GOLD OVER 0.46 METERS IN UNDERGROUND DRILLING AT TRIXIE, TINTIC PROJECT

Osisko Development Corp. has released the remaining drilling and underground chip sampling results from new development areas as part of its 2023 exploration program at its 100-per-cent-owned Trixie test mine, within the company's wider Tintic project, located in the historic East Tintic mining district in central Utah, United States.

Drill assay highlights

This news release includes assays from 14 underground diamond drill (DD) holes (see the table entitled "Drilling length-weighted assay composites at Trixie"). Select assay highlights include:

• 66.04 grams per tonne (g/t) gold (Au) and 167.64 g/t silver (Ag) over 8.99 metres in TRXU-DD-23-072A (1.93 ounces per ton (oz/ton) Au and 4.89 oz/ton Ag over 29.50 feet (ft)), including:
  • 610 g/t Au and 1,523 g/t Ag over 0.46 m (17.79 oz/ton Au and 44.42 oz/ton Ag over 1.50 ft);
  • 180 g/t Au and 691 g/t Ag over 0.76 m (5.25 oz/ton Au and 20.15 oz/ton Ag over 2.50 ft).
• 23.89 g/t Au and 151.04 g/t Ag over 9.45 m in TRXU-DD-23-068 (0.70 oz/ton Au and 4.41 oz/ton Ag over 31 ft), including:
  • 81.23 g/t Au and 98.14 g/t Ag over 0.76 m (2.37 oz/ton Au and 2.86 oz/ton Ag over 2.50 ft).
• 102.67 g/t Au and 740.43 g/t Ag over 1.07 m in TRXU-DD-23-061 (2.99 oz/ton Au and 21.60 oz/ton Ag over 3.50 ft), including:
  • 281 g/t Au and 1,644 g/t Ag over 0.30 m (8.20 oz/ton Au and 47.95 oz/ton Ag over one ft).
• 10.84 g/t Au and 35.29 g/t Ag over 4.57 m in TRXU-DD-23-066 (0.32 oz/ton Au and 1.03 oz/ton Ag over 15 ft);
• 5.79 g/t Au and 101.98 g/t Ag over 13.72 m in TRXU-DD-23-065 (0.17 oz/ton Au and 2.97 oz/ton Ag over 45 ft).

Drill results summary

• In 2023, the company completed a total of 6,028 m (19,776 ft) of underground drilling in 73 DD holes at Trixie. Assays have now been received for all 2023 holes testing the Trixie high-sulphidation epithermal Au-Ag targets. A new mineral resource estimate (MRE) for the Trixie deposit is in progress and is expected to be released in March, 2024. The Trixie MRE will include all underground drilling and chip sample assays from the 2023 program.
• One additional hole (TRXU-DD-23-073) was drilled to a depth of 759.6 m (2,492 ft) and targeted a copper-gold porphyry target below Trixie. Assays for this hole are pending.
• 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, south toward the Sioux Ajax fault. Results from holes TRXU-DD-23-065 (5.79 g/t Au over 13.72 m), TRXU-DD-23-066 (10.84 g/t over 4.57 m) and TRXU-DD-23-068 (23.89 g/t Au over 9.45 m) indicate that the mineralization appears to be plunging to the south toward the Sioux Ajax fault.
• One diamond drill rig is currently active at surface testing a copper-gold-molybdenum (Cu-Au-Mo) target at Big Hill and is at a current depth of 922 m (3,028 ft). The target depth for this hole is approximately 1,524 m (5,000 ft). Assays are pending for this drill hole.

Underground chip sample assay highlights

Assay highlights include underground chip samples from 55 new development faces at Trixie. Of these, 25 faces had samples with greater than one g/t Au or greater than 50 g/t Ag values (see the table entitled "Face chip sample length-weighted assay composites at Trixie"). The remaining chip samples returned no significant assays. Selected assay highlights include:

• 123.67 g/t Au and 658.46 g/t Ag over 4.27 m in CH01683 (3.61 oz/ton Au and 19.21 oz/ton Ag over 14 ft), including:
  • 717.86 g/t Au and 2,996.98 g/t Ag over 0.61 m (20.94 oz/ton Au and 87.41 oz/ton Ag over two ft).
• 40.84 g/t Au and 67.16 g/t Ag over 3.66 m in CH01694 (1.19 oz/ton Au and 1.96 oz/ton Ag over 12 ft), including:
  • 153.72 g/t Au and 227.32 g/t Ag over 0.91 m (4.48 oz/ton Au and 6.63 oz/ton Ag over three ft).
• 385.26 g/t Au and 1,094.04 g/t Ag over 0.30 m in CH01687 (11.24 oz/ton Au and 31.91 oz/ton Ag over one ft);
• 26.89 g/t Au and 186.63 g/t Ag over 3.05 m in CH01682 (0.78 oz/ton Au and 5.44 oz/ton Ag over 10 ft);
• 28.62 g/t Au and 150.08 g/t Ag over 2.23 m in CH01676 (0.83 oz/ton Au and 4.38 oz/ton Ag over 7.30 ft), including:
  • 62.60 g/t Au and 247.62 g/t Ag over 0.91 m (1.83 oz/ton Au and 7.22 oz/ton Ag over three ft).
• 7.74 g/t Au and 202.67 g/t Ag over 7.62 m in CH01679 (0.23 oz/ton Au and 5.91 oz/ton Ag over 25 ft);
• 18.48 g/t Au and 355.54 g/t Ag over 1.52 m in CH01664 (0.54 oz/ton Au and 10.37 oz/ton Ag over five ft).

Chip sample summary:

• Chip samples were collected in new development areas in the face and walls of exploration crosscuts to explore along all domains of the Trixie deposit on the 625 level, to the north toward the Trixie fault and to the south toward the Sioux Ajax fault.
• The sampling and drilling results indicate that target areas to the north of Trixie and to the south down plunge of the T2 structure are potentially mineralized, and warrant further follow-up exploration drilling and sampling to understand the extent of mineralization.

About Trixie

The Trixie test mine is one of several gold and base metal targets within the larger Tintic project consisting of more than 17,000 acres of patented mining claims and mineral leases (14,200 acres of patented mining claims and a further approximately 3,000 acres of overwhelmingly leased patented mining claims) within the historic East Tintic mining district of central Utah, U.S. The T2 and T4 structures at Trixie show multiounce 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 located in the hangingwall of the T2 and comprises Au-Ag-rich mineralization in host rock quartzite with quartz-barite-sulphosalt stockwork veining. Mineralization reports consistent multiounce gold grades along the entire strike length.

A 3-D model and virtual site tour of Trixie and the wider Tintic project are accessible on the company's VRIFY page.

Information relating to the Tintic project and the current MRE for the Trixie deposit is supported by the technical report titled "NI [National Instrument] 43-101 Technical Report, Initial Mineral Resource Estimate for the Trixie Deposit, Tintic Project, Utah, United States of America," dated Jan. 27, 2023 (with an effective date of Jan. 10, 2023), prepared for the company by independent representatives of Micon International Ltd. 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 and is available electronically on SEDAR+ and on EDGAR under Osisko Development's issuer profile and on the company's website.

Qualified person

The scientific and technical information contained in this news release has been reviewed and approved by Maggie Layman, PGeo, vice-president of exploration for Osisko Development and a qualified person within the meaning of NI 43-101.

Face sampling methodology

As most structures at Trixie are steeply dipping to the east or west, current sampling procedures are designed to sample the structure. Chip samples are collected and do not exceed one m (three ft) in length. The face is washed for safety, and for better identification of mineralization, alteration and structures. The hangingwall and footwall of the structures are marked up on the face and back, samples intervals are marked up and follow lithological contacts.

Samples are collected in feet and assays are reported in grams per tonne and troy ounce per short ton gold and silver. Conversions to metric and imperial measurements are rounded to two decimal places.

Quality assurance/quality control (QA/QC)

All drill core and exploration samples are dispatched to SGS Canada's laboratory in Burnaby, B.C., for off-site sample preparation and analysis. Samples are assigned a unique sample ID. All geological and sampling information is entered into 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, B.C. Sample submission forms accompany the samples, and digital copies are e-mailed to SGS Canada.

All core sample preparation is completed by SGS Canada, including drying, crushing and pulverizing of samples. Analytical assays include gold by 30-gram fire assay with atomic absorption spectroscopy finish (GO_FAA30V10), and gold overlimits by fire assay with gravimetric finish (GO_FAG30V). Multielement analysis (including silver) is by four-acid digest with inductively coupled plasma atomic emission spectroscopy/mass spectrometry finish (GE_ICM40Q12). The 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 less than 10 millimetres and a 250-gram split is taken. The split is pulverized, and a 30-gram 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. Interlaboratory check assays using ALS Laboratory as a third party independent analysis of samples is routinely carried out as part of continuing QA/QC work. Certified OREAS QC standards and blanks are inserted at regular intervals in the sample stream to monitor laboratory performance.

True width determination is estimated to be approximately 0.3 m to 2.4 m (one to eight ft) wide for the T2 structure, approximately three m to 25 m (10 to 80 ft) for the T4 mineralized stockwork zone located in the hangingwall of the T2 structure and 1.5 m to three m (five to nine ft) for the 75-85 structure.

About Osisko Development Corp.

Osisko Development is a premier North American gold development company focused on high-quality past-producing properties located in mining-friendly jurisdictions with district-scale potential. The company's objective is to become an intermediate gold producer by advancing its 100-per-cent-owned Cariboo gold project, located in central B.C., Canada, the Tintic project in the historic East Tintic mining district in Utah, U.S., and the San Antonio gold project in Sonora, Mexico. In addition to considerable brownfield exploration potential of these properties, that benefit from significant historical 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 develop attractive, long-life, socially and environmentally sustainable mining assets, while minimizing exposure to development risk and growing mineral resources.

We seek Safe Harbor.