Company: DAWN
Filing Date: 2025-01-10
Form Type: S-8
Source: 0001193125-25-004434
Chunk: 2

Company: Day One Biopharmaceuticals, Inc.
Filing Date: 2025-01-10
Form: S-8
Chunk 2
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 this 10th day of January, 2025.

| DAY ONE BIOPHARMACEUTICALS, INC. |     |                                  |
| By:                              |     | /s/ Jeremy Bender, Ph.D., M.B.A. |
|                                  |     | Jeremy Bender, Ph.D., M.B.A      |
|                                  |     | Chief Executive Officer          |

POWER OF ATTORNEY KNOW ALL PERSONS BY THESE PRESENTS, that each person whose signature appears below hereby constitutes and appoints Jeremy Bender and Charles N. York II, and each of them, as his or her true and lawful attorney-in-factand agent with full power of substitution, for him or her in any and all capacities, to sign any and all amendments (including post-effective amendments) to this Registration Statement on Form S-8,and to file the same, with all exhibits thereto and other documents in connection therewith, with the Securities and Exchange Commission, granting unto said attorney-in-factand agent full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully for all intents and purposes as he might or could do in person, hereby ratifying and confirming all that said attorney-in-factand agent, or his or her substitute, may lawfully do or cause to be done by virtue hereof. Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following persons on behalf of the Registrant in the capacities and on the date indicated.

| Name                             
 /s/ Jeremy Bender, Ph.D., M.B.A. 
 Jeremy Bender, Ph.D., M.B.A.     
 /s/ Charles N. York II, M.B.A.   
 Charles N. York II, M.B.A.       |     | Title                                               
 Chief Executive Officer and Director                
 (Principal Executive Officer)                       
 Chief Operating Officer and Chief Financial Officer 
 (Principal Financial and Accounting Officer)        |     | Date             
 January 10, 2025 
 January 10, 2025 |
|:---------------------------------|:----|:----------------------------------------------------|:----|:-----------------|
| /s/ Garry Nicholson              
 Garry Nicholson                  |     | Chair and Director                                  |     | January 10, 2025 |
| /s/ Habib Dable                  
 Habib Dable                      |     | Director                                            |     | January 10, 2025 |
| /s