Osisko Development Completes 13,000-METER Infill Drilling Program at Cariboo GOLD Project and Provides Update ON Ongoing Lowhee Underground Drilling; Intercepts Include 44.68 G/T GOLD over 1.5 Meters from 27.9 Meters Downhole, Including 133.62 G/T GOLD over 0.5
ODV NYSE TSXV News Release
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OSISKO DEVELOPMENT COMPLETES 13,000-METER INFILL DRILLING PROGRAM AT
CARIBOO GOLD PROJECT AND PROVIDES UPDATE ON ONGOING LOWHEE
UNDERGROUND DRILLING; INTERCEPTS INCLUDE 44.68 g/t GOLD OVER 1.5
METERS FROM 27.9 METERS DOWNHOLE, INCLUDING 133.62 g/t GOLD OVER 0.5
METERS FROM 28.4 METERS DOWNHOLE
Montreal, Québec, June 9, 2026 – Osisko Development Corp. (NYSE: ODV, TSXV: ODV) ("Osisko
Development" or the "Company") is pleased to announce new infill drilling results from its completed
13,000-meter program on 10 meter drill spacing, as well as new results from additional infill and near
mine exploration activities in the Lowhee Zone of the Company's permitted, 100%-owned Cariboo Gold
Project (the "Project"), located in central British Columbia ("B.C."), Canada. Three of the six drill hole
fans reported herein comprise the final 2,659 meters ("m") of the 13,000 m underground infill program,
bringing the final tally of drilling with full results to 13,684 m. The remaining three fans comprise an
additional 2,995 m of infill and near mine exploration drilling at the L1290-ORE-000 and L1260-ORE-
002 levels. Reconciliation work is underway on an updated localized b lock model, with final results
anticipated in the second quarter of 2026.
Chris Lodder, President, stated , "The completion of the tighter infill drill spacing gives us a better
understanding of vein corridor spatial geometries and local variability specific to this part of the Lowhee
deposit, and gives us confidence going forward to help refine infill drill requirements, production designs
and sequencing in the Lowhee deposit of the Cariboo Gold Project . The additional infill and near mine
exploration intercepts reinforce the importance of continued drilling in underexplored zones."
DRILL ASSAY HIGHLIGHTS
This news release includes assays from fifty-five (55) underground infill and near mine exploration HQ
diamond drill ("DD") holes (63.5-millimeter diameter) totaling 5,654 m with depths ranging from 76.5
to 138 m (see Table 1 and Figure 2). Select photon and fire assay highlights include:
• 44.68 grams per tonne ("g/t") gold ("Au") over 1.5 m in BMU -25-176 from 27.9
downhole, including:
o 133.62 g/t Au over 0.5 m from 28.4 m downhole
• 25.78 g/t Au over 2.5 m in BMU-26-055 from 41.3 m downhole, including:
o 103.47 g/t Au over 0.5 m from 42.8 downhole, and
o 12.51 g/t Au over 1.0 m from 41.8 downhole
HIGHLIGHTS
13,684 m of grid infill drilling completed (2,659 m new results) on 10-m drill spacing in 142 drill
holes from August 2025 representing the entirety of the planned Appian infill program
Highlight intercepts include: 44.68 g/t Au over 1.5 m from 27.9 m downhole (including 133.62 g/t Au
over 0.5 m from 28.4 m downhole), and 25.78 g/t Au over 2.5 m from 41.3 m downhole (including
103.47 g/t Au over 0.5 m from 42.8 m downhole, and 12.51 g/t Au over 1.0 m from 41.8 m downhole)
2,995 m of additional infill and near mine exploration drilling completed as part of ongoing
Lowhee zone underground diamond drilling
Highlight intercepts include: 31.64 g/t Au over 2.0 m from 50.0 m downhole (including 125.24 g/t over
0.5 m from 50.5 m downhole), and 11.21 g/t Au over 4.9 m from 63.3 m downhole (including 58.19 g/t
Au over 0.7 m from 65.0 m downhole, and 17.57 g/t Au over 0.7 m from 63.3 m downhole).
Results to date continue to contribute to a more detailed understanding of sp atial controls and
local variability within Lowhee Zone and give positive indications for near mine potential
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• 31.64 g/t Au over 2 m in BMU-26-034 from 50.0 m downhole, including:
o 125.24 g/t Au over 0.5 m from 50.5 m downhole, and
• 11.21 g/t Au over 4.9 m in BMU-26-031 from 63.3 m downhole, including:
o 58.19 g/t Au over 0.7 m from 65.0 m downhole, and
o 17.57 g/t Au over 0.7 m from 63.3 m downhole
• 21.84 g/t Au over 2.5 m in BMU-26-008 from 79.7 m downhole, including:
o 91.3 g/t Au over 0.5 m from 79.7 m downhole, and
o 6.79 g/t Au over 0.5 m from 81.2 m downhole, and
o 5.97 g/t Au over 0.5 m from 80.7 m downhole, and
o 2.66 g/t Au over 0.5 m from 80.2 m downhole, and
o 2.47 g/t Au over 0.5 m from 81.7 m downhole
• 91.99 g/t Au over 0.5 m in BMU-26-013 from 73.75 m downhole
• 18.59 g/t Au over 2.65 m in BMU-26-006 from 43.35 m downhole, including:
o 48.93 g/t Au over 1.0 m from 43.85 m downhole
• 4.76 g/t Au over 6.05 m in BMU-26-037 from 85.0 m downhole, including:
o 44.79 g/t Au over 0.5 m from 88.5 m downhole, and
o 6.13 g/t Au over 0.5 m from 88.0 m downhole, and
o 4.02 g/t Au over 0.5 m from 87.0 m downhole
• 3.28 g/t Au over 7.3 m in BMU-25-179 from 81.7 m downhole, including:
o 12.73 g/t Au over 0.95 m from 84.85 m downhole, and
o 9.68 g/t Au over 0.9 m from 85.8 m downhole
• 46.37 g/t Au over 0.5 m in BMU-26-022 from 14.0 m downhole
Complete assay highlights, including true width estimates, are presented in Table 1 and drill hole
locations and orientations are listed in Table 2. Intervals not recovered were assigned zero grade. Top
cuts have not been applied to high grade assays.
DISCUSSION OF RESULTS
• Figures 4 -6 ( 1260 level): Cut-off assay composites completing the planned 13,000 m
systematic grid infill program . These last three fans were testing areas peripheral to reserve
stopes, and outside the modeled vein corridors. Intercepts received to date suggest possible
extensions of vein corridors, with potential for resource conversion and upside mineralization.
• Figures 7-8 (1290 Level): Cut-off assay composites from additional infill drilling at the 1290
levels show a degree of spatial correlation with the modelled reserve stopes with intercepts
outside these areas suggesting potential for resource conversion and upside mineralization.
• Figure 9 (1260 Level): Cut-off assay composites from infill and near mine exploration drilling
to the southeast at the 1260 level include several new intercepts outside the current vein
corridors and resource footprint.
• All intercepts will be incorporated in the planned remodelling and mineral resource calculation
process to determine their implications on an updated local block model and any potential
adjustments to planned reserve stopes. In certain areas, this may support the addition of new
planned reserve stopes, subject to the final estimation process outcome.
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Figure 1: Cariboo Gold Project deposit map with Location of Lowhee Zone and Cow Portal underground access.
Figure 2: Location and overview of ongoing Lowhee Zone underground definition infill and near mine exploration
diamond drilling
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Figure 3: Lowhee Zone select underground drilling highlights (plan view).
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Figure 4: L1260-ORE-003 Lowhee Zone grid infill select underground drill assay highlights (this release) with
previously released surface and underground diamond drilling results in cross section by fan. Results from
immediately adjacent fans within slice omitted for visual clarity (20 m slice looking 048°).
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Figure 5: L1260-ORE-003 Lowhee Zone grid infill select underground drill assay highlights (this release) with
previously released surface and underground diamond drilling results in cross section by fan. Results from
immediately adjacent fans within slice omitted for visual clarity (20 m slice looking 060°).
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Figure 6: L1260-ORE-003 Lowhee Zone grid infill select underground drill assay highlights (this release) with
previously released surface and underground diamond drilling results in cross section by fan. Results from
immediately adjacent fans within slice omitted for visual clarity (20 m slice looking 073°).
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Figure 7: L1290-ORE-000 Lowhee Zone infill select underground drill assay highlights (this release) with
previously released surface and underground diamond drilling results in cross section by fan. Results from
immediately adjacent fans within slice omitted for visual clarity (20 m slice looking 017°).