BENDER JEREMY (Chief Executive Officer) sold 8.2% of their position (15.89K shares) of DAY ONE BIOPHARMACEUTICALS, INC. on the open market

Open‑market sale worth $141.7K — a moderate reduction. Review remaining holdings and any 10b5‑1 plan disclosures.

S · 1 sale

BENDER JEREMY

Filed: 11/18/2025ACC: 0001863107-25-000005

InsiderBENDER JEREMYCIK 1863107

→

IssuerDAY ONE BIOPHARMACEUTICALS, INC.CIK 1845337

DirectorOfficer· Chief Executive Officer

Since May 2021

-15.89K

Net shares

Net seller

$141.7K

Total sold

Open market trades

0B · 1S

Total transactions

31.69K acquired · 47.59K disposed

Non-Derivative Transactions5

Common Stock

Direct

M · Option Exercise

+3.57K

Price / share

—

Trade value

—

% of position

2.2%

11/15/2025

161.37K→164.94K

Common Stock

Direct

M · Option Exercise

+4.75K

Price / share

—

Trade value

—

% of position

2.9%

11/15/2025

164.94K→169.69K

Common Stock

Direct

M · Option Exercise

+11.69K

Price / share

—

Trade value

—

% of position

6.9%

11/15/2025

169.69K→181.37K

Common Stock

Direct

M · Option Exercise

+11.69K

Price / share

—

Trade value

—

% of position

6.4%

11/15/2025

181.37K→193.06K

Common Stock

Direct

S · Sale

−15.89K

Price / share

$8.91

Trade value

$141.69K

% of position

8.2%

11/17/2025

193.06K→177.16K

Total

Net shares

+15.80K

Net value

-$141.69K

Security	Date	Type	Shares	Price / Share	Trade Value	% of Position	Held Before	Held After
Common Stock Direct	11/15/2025	M · Option Exercise	+3.57K	—	—	2.2%	161.37K	164.94K
Common Stock Direct	11/15/2025	M · Option Exercise	+4.75K	—	—	2.9%	164.94K	169.69K
Common Stock Direct	11/15/2025	M · Option Exercise	+11.69K	—	—	6.9%	169.69K	181.37K
Common Stock Direct	11/15/2025	M · Option Exercise	+11.69K	—	—	6.4%	181.37K	193.06K
Common Stock Direct	11/17/2025	S · Sale	−15.89K	$8.91	$141.69K	8.2%	193.06K	177.16K
Total			+15.80K		-$141.69K

Derivative Transactions4

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

3.57K shares

−3.57K

Strike price

Held after

0.00

Exercisable

—

11/15/2025

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

4.75K shares

−4.75K

Strike price

Held after

19K

Exercisable

—

11/15/2025

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

11.69K shares

−11.69K

Strike price

Held after

93.50K

Exercisable

—

11/15/2025

Restricted Stock Unit (RSU)

Direct

M · Option Exercise

Converts to

Common Stock

11.69K shares

−11.69K

Strike price

Held after

140.25K

Exercisable

—

11/15/2025

Security	Converts To	Date	Type	Shares	Exercisable	Held After
Restricted Stock Unit (RSU) Direct	Common Stock3.57K shares	11/15/2025	M · Option Exercise	−3.57K	—	0.00
Restricted Stock Unit (RSU) Direct	Common Stock4.75K shares	11/15/2025	M · Option Exercise	−4.75K	—	19K
Restricted Stock Unit (RSU) Direct	Common Stock11.69K shares	11/15/2025	M · Option Exercise	−11.69K	—	93.50K
Restricted Stock Unit (RSU) Direct	Common Stock11.69K shares	11/15/2025	M · Option Exercise	−11.69K	—	140.25K

Non-Derivative Holdings (Post-Transaction)5

Common Stock

Indirect

Shares owned1.41M

Common Stock

Indirect

Shares owned14.45K

Common Stock

Indirect

Shares owned147.70K

Common Stock

Indirect

Shares owned18.20K

Common Stock

Indirect

Shares owned20.20K

Total

1.61M indirect1.61M

Security Title	Shares Owned	Ownership Type
Common Stock	1.41M	Indirect
Common Stock	14.45K	Indirect
Common Stock	147.70K	Indirect
Common Stock	18.20K	Indirect
Common Stock	20.20K	Indirect
Total	1.61M	1.61M indirect

Derivative Holdings (Post-Transaction)0

No derivative holdings reported