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OSISKO DEVELOPMENT REPORTS UNDERGROUND SAMPLING RESULTS AT TRIXIE, TINTIC PROJECT, INCLUDING: 4,757.42 g/t Au and 528.90 g/t Ag over 1.22 m (138.76 oz/t Au and 15.43 oz/t Ag over 4.00 ft.)

Drill Results Sampling & Geoscience Results

NYSE: ODV TSXV: ODV NEWS RELEASE

Page 1 of 20

OSISKO DEVELOPMENT REPORTS UNDERGROUND SAMPLING RESULTS

AT TRIXIE, TINTIC PROJECT, INCLUDING: 4,757.42 g/t Au and 528.90 g/t Ag over 1.22 m

(138.76 oz/t Au and 15.43 oz/t Ag over 4.00 ft.)

Montreal, Québec, November 30, 2022 – Osisko Development Corporation (NYSE: ODV, TSXV: ODV)

("Osisko Development" or the "Company") is pleased to announce sampling results from its ongoing

underground exploration program at its 100%-owned Trixie test mine ("Trixie"), within the Company's wider

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

ASSAY HIGHLIGHTS:

Assay highlights include 702 chip samples from 177 mine faces at Trixie. A length-weighted composite for

each face Site ID is presented in Table 1 and individual higher-grade samples are also identified within the

composites. Samples are collected in feet ("ft.") and assays are reported in grams per tonne ("g/t") gold

("Au") and silver ( "Ag"). Conversions to metric and imperial measurements are rounded to two decimal

places. Selected assay highlights include:

• 340.36 g/t Au and 69.94 g/t Ag over 2.19 meters ("m") (9.93 troy ounce per short ton ( "oz/t") Au

and 2.04 oz/t Ag over 7.20 ft.) including

o 1,017.01 g/t Au and 209.81 g/t Ag over 0.73 m (29.66 oz/t Au and 6.12 oz/t Ag over 2.40 ft.)

• 912.28 g/t Au and 5.17 g/t Ag over 2.53 m (26.61 oz/t Au and 0.15 oz/t Ag over 8.30 ft.)

• 4,186.46 g/t Au over 0.55 m (122.11 oz/t Au over 1.80 ft.)

• 5,197.77 g/t Au and 6,698.97 g/t Ag over 0.61 m (151.60 oz/t Au and 195.39 oz/t Ag over 2.00 ft.)

• 1,553.07 g/t Au and 1,224.91 g/t Ag over 1.52 m (45.30 oz/t Au and 35.73 oz/t Ag over 5.00 ft.)

• 2,873.05 g/t Au and 2,263.41 g/t Ag over 0.82 m (83.80 oz/t Au and 66.02 oz/t Ag over 2.70 ft.)

• 2,800.11 g/t Au and 315.99 g/t Ag over 2.07 m (81.67 oz/t Au and 9.22 oz/t Ag over 6.80 ft. )

including

o 4,757.42 g/t Au and 528.9 g/t Ag over 1.22 m (138.76 oz/t Au and 15.43 oz/t Ag over 4.00 ft.)

• 683.53 g/t Au and 42.51 g/t Ag over 1.04 m (19.94 oz/t Au and 1.24 oz/t Ag over 3.40 ft.) including

o 1,769.33 g/t Au and 102.40 g/t Ag over 0.40 m (51.61 oz/t Au and 2.99 oz/t Ag over 1.30 ft.)

• 856.54 g/t Au and 608.09 g/t Ag over 0.94 m (24.98 oz/t Au and 17.74 oz/t Ag over 3.10 ft.)

including

o 2,202.85 g/t Au and 1,559.99 g/t Ag over 0.37 m (64.25 oz/t Au and 45.50 oz/t Ag over 1.20 ft.)

• 482.30 g/t Au and 409.81 g/t Ag over 2.59 m (14.07 oz/t Au and 11.95 oz/t Ag over 8.50 ft.)

including

o 1,277.05 g/t Au and 1,086.13 g/t Ag over 0.98 m (37.25 oz/t Au and 31.68 oz/t Ag over 3.20 ft.)

• 226.00 g/t Au and 83.40 g/t Ag over 2.50 m (6.59 oz/t Au and 2.43 oz/t Ag over 8.20 ft.) including

o 903.57 g/t Au and 323.83 g/t Ag over 0.61 m (26.35 oz/t Au and 9.45 oz/t Ag over 2.00 ft.)

• 193.24 g/t Au and 140.79 g/t Ag over 2.74 m (5.64 oz/t Au and 4.11 oz/t Ag over 9.00 ft.)

• 367.54 g/t Au and 141.38 g/t Ag over 3.54 m (10.72 oz/t Au and 4.12 oz/t Ag over 11.60 ft.)

• 2,352.18 g/t Au and 911.10 g/t Ag over 0.55 m (68.61 oz/t Au and 26.57 oz/t Ag over 1.80 ft.)

• 543.03 g/t Au and 1,005.97 g/t Ag over 2.56 m (15.84 oz/t Au and 29.34 oz/t Ag over 8.40 ft.)

including

o 1,381.60 g/t Au and 2,546.06 g/t Ag over 1.01 m (40.30 oz/t Au and 74.26 oz/t Ag over 3.30 ft.)

• 386.04 g/t Au and 747.10 g/t Ag over 1.37 m (11.26 oz/t Au and 21.79 oz/t Ag over 4.50 ft.)

including

o 848.82 g/t Au and 1,665.65 g/t Ag over 0.61 m (24.76 oz/t Au and 48.58 oz/t Ag over 2.00 ft.)

Page 2 of 20

EXPLORATION SUMMARY:

• Current underground test mining activities at Trixie are directed by the exploration sampling and

drilling results.

• Exploration and underground activities are focused around the 625 level at Trixie, over a strike

length of 220 m (720 ft.) and a depth extent of 45 m (150 ft) (see Figures 2 and 3).

• Approximately 20% of the main Trixie area has been explored to date and additional potential for

high grade gold exists along strike, at depth down dip and down plunge and along fault zones

known to be fluid pathways for gold mineralization (Figure 2).

• High-grade gold results greater than 100 g/t are present throughout the entire sampled area, on all

levels, including recent development (see Figure 3 long section and Figure 4 grade distribution).

• Exploration cross cuts in the T4 intersect mineralized material up to 25 m ( 80 ft .) wide and

continuous between levels. High-grade gold mineralization similar to that of T2 is also present in

this zone (see Figure 5 cross section of T2 and T4 zones).

Chris Lodder, President of Osisko Development , commented, "Tintic continues to deliver high grade

sampling results as our exploration efforts expand the area of mineralization in and around Trixie. As we

continue to drive development to reach deeper levels of the mine beyond the main 625 level towards the

end of 2023, we are very excited to test exploration potential of target areas located adjacent to historic

mine workings that have previously not been tested to date. In addition to Trixie, our greater understanding

of the controls on the various styles of precious and base metal mineralization opens up years of potential

exploration growth and excitement for our shareholders."

Next Steps

Approximately 7,315 m (24,000 ft.) of surface reverse circulation ("RC") drilling and 1,274 m (4,180 ft.)1,898

ft. of underground diamond ("DD") drilling has been completed to November 15, 2022, which, together with

the continuous face and back sampling results, will support the completion of an initial mineral resource

estimate expected in the first quarter of 2023 (the "Trixie MRE"). The Trixie MRE is expected to encompass

the T2, T4 and 75 -85 mineral zones only, representing a small footprint adjacent to the 625 underground

level, to support near-term underground activities. The Company continues to be impacted by industry-wide

delays in assay turnaround time due to bottlenecks in the processing ability of assay labs. As a result, assay

results remain pending for a portion of the RC and DD drilling noted above.

The Company's primary focus remains on the completion of the Trixie portal and decline, which is

approximately 30% complete to date and is expected to be completed to the 625 underground level by the

second quarter of 2023 . Once fully comp lete, the decline will significantly improve access to the

underground workings , expand potential underground exploration target areas and provide sufficient

flexibility to complete additional programs targeting mineral resource growth beyond the 625 underground

level. The Company expects to provide an update on its 2023 exploration program plans in the first quarter

of 2023.

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 , USA. The T2 and T4 structures at Trixie sh ow multi-ounce gold grades associated with

high sulphidation epithermal mineralization, structurally controlled and hosted within quartzites. High grade

mineralized material from the T2 and T4 structures is currently being processed via vat leaching on sit e.

The T2 structure is approximately 0.3 m to 2.4 m (1 to 8 ft.) wide and mineralization consists of native Au,

and rare Au-Ag – rich telluride minerals with quartz. The T4 is a mineralized stockwork zone ranging from

approximately 3 m to 25 m (10 to 80 ft.) and 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

currently defined over 220 m (720 ft.) in strike and reports consistent multi -ounce gold grades along the

entire strike length.

Page 3 of 20

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 1.0 m (3 ft.) in length. The

face is washed for safety, and for better identification of mineralization, alteration and structures. The

hanging wall and footwall of the structures are marked up on the face and back, samples intervals are

marked up and follow lithological contacts.

For further information on the Tintic Project, please refer to the technical report titled "Technical Report on

the Tintic Project, East Tintic Mining District, Utah County, Utah, USA" , dat ed June 10, 2022 (with an

effective date of June 7, 2022) and prepared for the Company by Dr. Thomas A. Henr icksen, QP, C.P.G.

(the "Tintic Technical Report"). Reference should be made to the full text of the Tin tic 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) under Osisko

Development's issuer profile.

Figure 1: Tintic Project Area

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Figure 2: Trixie Long Section

Page 5 of 20

Figure 3: Trixie long section: detailed area of current development and sampling (625 level)

Page 6 of 20

Figure 4: Trixie long section, grade distribution (625 level)

Page 7 of 20

Figure 5: Cross Section of 75-85, T2 and T4 at Trixie (625 level)

Page 8 of 20

Table 1: 2022 Length Weighted Assay Composites at Trixie

METRIC IMPERIAL

Site 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)

CH1000 0.00 1.37 1.37

32.10 45.11 0.00 4.50 4.50 0.94 1.32

CH1000 Including 0.00 0.52 0.52

51.97 85.74 0.00 1.70 1.70 1.52 2.50

CH1000 and 0.52 0.76 0.24

49.06 50.22 1.70 2.50 0.80 1.43 1.46

CH1001 0.00 1.83 1.83

1.12 9.09 0.00 6.00 6.00 0.03 0.27

CH1002 0.00 1.68 1.68

1.73 1.82 0.00 5.50 5.50 0.05 0.05

CH1002 Including 1.04 1.25 0.21

5.34 14.25 3.40 4.10 0.70 0.16 0.42

CH1003 0.00 0.91 0.91

6.45 6.96 0.00 3.00 3.00 0.19 0.20

CH1004 0.00 0.91 0.91

7.84 29.72 0.00 3.00 3.00 0.23 0.87

CH1004 Including 0.30 0.43 0.12

37.61 138.43 1.00 1.40 0.40 1.10 4.04

CH1005 0.00 1.98 1.98

22.57 18.93 0.00 6.50 6.50 0.66 0.55

CH1005 Including 1.37 1.98 0.61

73.19 55.64 4.50 6.50 2.00 2.13 1.62

CH1006 0.00 1.37 1.37

386.04 747.10 0.00 4.50 4.50 11.26 21.79

CH1006 Including 0.76 1.37 0.61

848.82 1,665.65 2.50 4.50 2.00 24.76 48.58

CH1007 0.00 2.56 2.56

543.03 1,005.97 0.00 8.40 8.40 15.84 29.34

CH1007 Including 1.55 2.56 1.01

1,381.60 2,546.06 5.10 8.40 3.30 40.30 74.26

CH1008 0.00 0.91 0.91

0.59 5.12 0.00 3.00 3.00 0.02 0.15

CH1009 0.00 2.74 2.74

57.47 107.82 0.00 9.00 9.00 1.68 3.14

CH1009 Including 2.29 2.74 0.46

340.76 625.85 7.50 9.00 1.50 9.94 18.25

CH1010 0.00 1.22 1.22

0.02 13.76 0.00 4.00 4.00 0.00 0.40

CH1011 0.00 3.54 3.54

367.54 141.38 0.00 11.60 11.60 10.72 4.12

CH1011 Including 1.77 2.32 0.55

2,352.18 911.10 5.80 7.60 1.80 68.61 26.57

CH1012 0.00 1.28 1.28

0.49 16.35 0.00 4.20 4.20 0.01 0.48

CH1013 0.00 1.46 1.46

69.57 155.41 0.00 4.80 4.80 2.03 4.53

CH1013 Including 0.70 0.85 0.15

649.74 1,491.10 2.30 2.80 0.50 18.95 43.49

CH1014 0.00 1.16 1.16

26.01 215.62 0.00 3.80 3.80 0.76 6.29

CH1014 Including 0.67 0.94 0.27

106.96 900.34 2.20 3.10 0.90 3.12 26.26

CH1015 0.00 1.83 1.83

13.86 33.24 0.00 6.00 6.00 0.40 0.97

CH1015 Including 1.01 1.31 0.30

57.35 156.02 3.30 4.30 1.00 1.67 4.55

CH1016 0.00 1.52 1.52

5.18 15.64 0.00 5.00 5.00 0.15 0.46

CH1016 Including 0.00 0.30 0.30

24.17 51.32 0.00 1.00 1.00 0.70 1.50

CH1017 0.00 1.52 1.52

63.28 106.11 0.00 5.00 5.00 1.85 3.09