MERENDINO LAUREN (Chief Commercial Officer) sold 8.8% of their position (5.81K shares) of DAY ONE BIOPHARMACEUTICALS, INC. on the open market

Open‑market sale worth $67.4K — a moderate reduction. Review remaining holdings and any 10b5‑1 plan disclosures.

S · 1 sale

MERENDINO LAUREN

Filed: 2/18/2026ACC: 0001855298-26-000004

InsiderMERENDINO LAURENCIK 1855298

→

IssuerDAY ONE BIOPHARMACEUTICALS, INC.CIK 1845337

Officer· Chief Commercial Officer

Since Feb 2026

-5.81K

Net shares

Net seller

$67.4K

Total sold

Open market trades

0B · 1S

Total transactions

15.16K acquired · 20.98K disposed

Non-Derivative Transactions5

Common Stock

Direct

M · Option Exercise

+3.16K

Price / share

—

Trade value

—

% of position

6.2%

2/15/2026

50.81K→53.97K

Common Stock

Direct

M · Option Exercise

+3.69K

Price / share

—

Trade value

—

% of position

6.8%

2/15/2026

53.97K→57.66K

Common Stock

Direct

M · Option Exercise

+3.69K

Price / share

—

Trade value

—

% of position

6.4%

2/15/2026

57.66K→61.35K

Common Stock

Direct

M · Option Exercise

+4.63K

Price / share

—

Trade value

—

% of position

7.5%

2/15/2026

61.35K→65.97K

Common Stock

Direct

S · Sale

−5.81K

Price / share

$11.60

Trade value

$67.45K

% of position

8.8%

2/17/2026

65.97K→60.16K

Total

Net shares

+9.35K

Net value

-$67.45K

Security	Date	Type	Shares	Price / Share	Trade Value	% of Position	Held Before	Held After
Common Stock Direct	2/15/2026	M · Option Exercise	+3.16K	—	—	6.2%	50.81K	53.97K
Common Stock Direct	2/15/2026	M · Option Exercise	+3.69K	—	—	6.8%	53.97K	57.66K
Common Stock Direct	2/15/2026	M · Option Exercise	+3.69K	—	—	6.4%	57.66K	61.35K
Common Stock Direct	2/15/2026	M · Option Exercise	+4.63K	—	—	7.5%	61.35K	65.97K
Common Stock Direct	2/17/2026	S · Sale	−5.81K	$11.60	$67.45K	8.8%	65.97K	60.16K
Total			+9.35K		-$67.45K

Derivative Transactions4

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

3.16K shares

−3.16K

Strike price

Held after

18.98K

Exercisable

—

2/15/2026

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

3.69K shares

−3.69K

Strike price

Held after

25.82K

Exercisable

—

2/15/2026

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

3.69K shares

−3.69K

Strike price

Held after

40.56K

Exercisable

—

2/15/2026

Restricted Stock Units (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

4.63K shares

−4.63K

Strike price

Held after

69.38K

Exercisable

—

2/15/2026

Security	Converts To	Date	Type	Shares	Exercisable	Held After
Restricted Stock Unit (RSU) Direct	Common Stock3.16K shares	2/15/2026	M · Option Exercise	−3.16K	—	18.98K
Restricted Stock Unit (RSU) Direct	Common Stock3.69K shares	2/15/2026	M · Option Exercise	−3.69K	—	25.82K
Restricted Stock Unit (RSU) Direct	Common Stock3.69K shares	2/15/2026	M · Option Exercise	−3.69K	—	40.56K
Restricted Stock Units (RSU) Direct	Common Stock4.63K shares	2/15/2026	M · Option Exercise	−4.63K	—	69.38K