As of April 17, 2026, Day One Biopharmaceuticals's top three insider holders are Day1 Llc Ai (TenPercentOwner, 12.93Mn shares), Day1 Llc Ai (TenPercentOwner, 12.93Mn shares), Xi L.P. Canaan (TenPercentOwner, 6.96Mn shares).
| Holder | Position | Shares (Direct) | Shares (Indirect) | Report Date |
|---|---|---|---|---|
| Day1 Llc Ai | - | 12,929,322 | 0 | 20 Oct, 2023 |
| Day1 Llc Ai | - | 12,929,322 | 0 | 20 Oct, 2023 |
| Xi L.P. Canaan | - | 6,964,301 | 0 | 22 Sep, 2022 |
| Pharmaceutical Co Ltd Takeda | - | 0 | 6,120,124 | 09 Dec, 2021 |
| Venture Fund Xi, L.P. Atlas | - | 6,008,534 | 0 | 14 Dec, 2022 |
| Samuel C. Blackman | Head Of Rd | 1,034,015 | 0 | 12 Dec, 2024 |
| Samuel C. Blackman | Chief Medical Officer | 0 | 1,000,000 | 03 Dec, 2021 |
| Jeremy Bender | Chief Executive Officer | 0 | 808,285 | 26 Nov, 2025 |
| Venture Opportunity Fund I, L.P. Atlas | - | 793,116 | 0 | 06 Jul, 2022 |
| Venture Opportunity Fund Ii, L.P. Atlas | - | 766,667 | 0 | 22 Jun, 2022 |
| Michael Gladstone | - | 0 | 766,667 | 22 Jun, 2022 |
| Charles N Ii York | Coo And Cfo | 312,025 | 0 | 18 Feb, 2026 |
| Jeremy Bender | Chief Executive Officer | 204,603 | 0 | 18 Feb, 2026 |
| Adam Dubow | Gen Counsel Secretary | 72,694 | 0 | 18 Feb, 2026 |
| Lauren Merendino | Chief Commercial Officer | 60,157 | 0 | 18 Feb, 2026 |
| Jeremy Bender | Chief Executive Officer | 0 | 18,197 | 14 Jul, 2025 |
| Michael Vasconcelles | Head Of Research And Dev. | 4,397 | 0 | 18 Feb, 2026 |
* Please note that the shares above only reflect shares from the fund portfolio and the institutional portfolio. Shares from the personal portfolio are excluded from this Institutional Ownership Page. See these insiders' latest transactions here on Insider Page.
| Transaction Date | Insider Name | Security Class | Transaction Type | Shares Traded | Price | Shares Remaining | Ownership | Code |
|---|---|---|---|---|---|---|---|---|
| 15 Feb, 2026 | Charles N Ii York | Common Stock | A | 2,250 | - | 296,965 | D | M |
| 15 Feb, 2026 | Michael Vasconcelles | Common Stock | A | 7,125 | - | 7,125 | D | M |
| 15 Feb, 2026 | Jeremy Bender | Common Stock | A | 4,750 | - | 181,915 | D | M |
| 15 Feb, 2026 | Lauren Merendino | Common Stock | A | 3,162 | - | 53,971 | D | M |
| 15 Feb, 2026 | Adam Dubow | Common Stock | A | 2,963 | - | 65,589 | D | M |
| 15 Feb, 2026 | Charles N Ii York | Common Stock | A | 6,625 | - | 303,590 | D | M |
| 17 Feb, 2026 | Michael Vasconcelles | Common Stock | D | 2,728 | $11.60 | 4,397 | D | S |
| 15 Feb, 2026 | Jeremy Bender | Common Stock | A | 11,688 | - | 193,603 | D | M |
| 15 Feb, 2026 | Lauren Merendino | Common Stock | A | 3,688 | - | 57,659 | D | M |
| 15 Feb, 2026 | Adam Dubow | Common Stock | A | 1,750 | - | 67,339 | D | M |
| 15 Feb, 2026 | Charles N Ii York | Common Stock | A | 6,625 | - | 310,215 | D | M |
| 15 Feb, 2026 | Lauren Merendino | Common Stock | A | 3,687 | - | 61,346 | D | M |
| 15 Feb, 2026 | Jeremy Bender | Common Stock | A | 11,687 | - | 205,290 | D | M |
| 15 Feb, 2026 | Michael Vasconcelles | Restricted Stock Unit (RSU) | D | 7,125 | $0.00 | 106,875 | D | M |
| 15 Feb, 2026 | Adam Dubow | Common Stock | A | 3,688 | - | 71,027 | D | M |
| 15 Feb, 2026 | Charles N Ii York | Common Stock | A | 7,875 | - | 318,090 | D | M |
| 15 Feb, 2026 | Lauren Merendino | Common Stock | A | 4,625 | - | 65,971 | D | M |
| 15 Feb, 2026 | Jeremy Bender | Common Stock | A | 14,812 | - | 220,102 | D | M |
| 15 Feb, 2026 | Adam Dubow | Common Stock | A | 3,687 | - | 74,714 | D | M |
| 15 Feb, 2026 | Adam Dubow | Common Stock | A | 4,375 | - | 79,089 | D | M |