Comparable stake leader
FMR LLC
SEC ownership of Boundless Bio, Inc.
Top holders, 13D/G large-stake signals, insider positions, and transaction flow tied to CIK 0001782303.
Disclosed value leader
FMR LLC
Comparable rows
36/50
Latest evidence
31 Mar 2026
- Public ticker
- BOLD on Nasdaq
- Parsed ownership sources
- 13D/G, 13F, and 3/4/5
- Largest SEC-reported holder
- FMR LLC
- Latest 13D/G holder
- FMR LLC
- Latest parsed ownership date
- 31 Mar 2026
- Issuer CIK
- 0001782303
- Issuer location
- San Diego, CA
Ownership snapshot
CIK-linked ownership evidence from parsed SEC filings.
2 signals
Issuer
Names, identifiers, and filing context for this profile.
2 identity fields
Ownership snapshot
Top shareholders of Boundless Bio, Inc. (13F + 13D/G + 3/4/5)
Grouped by holder across the latest SEC ownership disclosures. Start with comparable ownership when available, then verify the linked 13F, 13D/G, or 3/4/5 evidence.
Comparable stake leader
FMR LLC
Disclosed value leader
FMR LLC
Comparable rows
36/50
Latest evidence
31 Mar 2026
13D/G
13F
3/4/5
Lead comparable stake: 12%
14 rows are not safely comparable across share classes.
13D/G row: FMR LLC
Showing 1-8 of 50 holder rows.
Quick read
FMR LLC leads the comparable SEC ownership view at 12%.
36 of 50 rows have a safely comparable ownership percentage. Use this as a filing-backed starting point, then open the detailed table for source links, reporting role, position value, share count, and filing date.
Open SEC evidence
Opens FMR LLC's linked filing trail.
Comparable ownership
Top 5
FMR LLC
12%
CITADEL ADVISORS LLC
6.4%
SECTORAL ASSET MANAGEMENT INC
3%
Stonepine Capital Management, LLC
2.7%
VANGUARD CAPITAL MANAGEMENT LLC
2.7%
Ownership % is shown only when SEC disclosures are safely comparable across share classes.
Detailed SEC evidence table Showing 1-8 of 50 holder rows
| Holder | Evidence | Ownership % | Position | 12M Net Δ | As of |
|---|---|---|---|---|---|
| FMR LLC |
13D/G
13F
Company
|
12%
|
$3,086,625
2,684,022 shares
|
$0 | 31 Dec 2025 |
| CITADEL ADVISORS LLC |
13D/G
13F
Kenneth Griffin · Company
|
6.4%
|
$1,763,067
1,433,388 shares
|
$0 | 26 Nov 2025 |
| SECTORAL ASSET MANAGEMENT INC |
13F
Company
|
3%
|
$746,431
678,574 shares
|
— | 31 Mar 2026 |
| Stonepine Capital Management, LLC |
13F
Company
|
2.7%
|
$657,450
597,682 shares
|
— | 31 Mar 2026 |
| VANGUARD CAPITAL MANAGEMENT LLC |
13F
Company
|
2.7%
|
$656,911
597,192 shares
|
— | 31 Mar 2026 |
| WELLINGTON MANAGEMENT GROUP LLP |
13F
Company
|
2.5%
|
$611,856
556,233 shares
|
— | 31 Mar 2026 |
| RENAISSANCE TECHNOLOGIES LLC |
13F
Company
|
1.8%
|
$438,900
399,000 shares
|
— | 31 Mar 2026 |
| Alyeska Investment Group, L.P. |
13F
Company
|
1.3%
|
$330,000
300,000 shares
|
— | 31 Mar 2026 |
How to read this table
Rows are grouped by holder and ranked first by SEC-reported ownership % when it is safely comparable, then by disclosed holdings value. — indicates unavailable or non-comparable values; "mixed-class rows" means the latest filing spans non-comparable classes.
Forms 3/4/5 flow
Insider trading overview
Insider buy and sell flow is broadly balanced over the last 12 months. No Buy or Sell transactions have been reported since 12 Jun 2025.
Buys
$0
Insiders: 0
Sells
$0
Insiders: 0
Net
$0
Shares: 0
Window
Last 12 months
4 rolling buckets
Buy value
Sell value
Shares: 0
Shares: 0
| Window (months) | Buy shares | Sell shares | Buy value | Sell value | Net value |
|---|---|---|---|---|---|
| 0-3 | 0 | 0 | $0 | $0 | $0 |
| 3-6 | 0 | 0 | $0 | $0 | $0 |
| 6-9 | 0 | 0 | $0 | $0 | $0 |
| 9-12 | 0 | 0 | $0 | $0 | $0 |
Reporting owners
Insider holders from Forms 3/4/5
Showing 1-18 of 18 reporting-owner rows connected to Boundless Bio, Inc.. Open a relationship link for the CIK-to-CIK filing trail.
Rows
18
Largest Forms 3/4/5 holder
Jennifer Lew
Net 12M change
$0
Latest report
23 Jan 2026
Recent insider transactions for Boundless Bio, Inc.
Showing up to 300 recent insider transactions from the last 12 months.
| Insider | Symbol | Class | Transaction | % | SEC-reported value | SEC-reported price | Shares | Shares owned | Date | Ownership |
|---|---|---|---|---|---|---|---|---|---|---|
| Robert Doebele | BOLD | Stock Option (right to buy) | Award | 230,000 | 230,000 | 23 Jan 2026 | Direct | |||
| Jessica Oien | BOLD | Stock Option (right to buy) | Award | 220,000 | 220,000 | 23 Jan 2026 | Direct | |||
| Ph.D. Christian Hassig | BOLD | Stock Option (right to buy) | Award | 230,000 | 230,000 | 23 Jan 2026 | Direct | |||
| Zachary Hornby | BOLD | Stock Option (right to buy) | Award | 600,000 | 600,000 | 23 Jan 2026 | Direct | |||
| David A. Hinkle | BOLD | Stock Option (right to buy) | Award | 140,000 | 140,000 | 23 Jan 2026 | Direct | |||
| Christine Brennan | BOLD | Stock Option (right to buy) | Award | 16,000 | 16,000 | 23 Jun 2025 | Direct | |||
| James Christensen | BOLD | Stock Option (right to buy) | Award | 16,000 | 16,000 | 23 Jun 2025 | Direct | |||
| Jennifer Lew | BOLD | Stock Option (right to buy) | Award | 16,000 | 16,000 | 23 Jun 2025 | Direct | |||
| Jonathan E. Lim | BOLD | Stock Option (right to buy) | Award | 24,000 | 24,000 | 23 Jun 2025 | Direct | |||
| Kristina Burow | BOLD | Stock Option (right to buy) | Award | 16,000 | 16,000 | 23 Jun 2025 | Direct | |||
| Nancy Whiting | BOLD | Stock Option (right to buy) | Award | 16,000 | 16,000 | 23 Jun 2025 | Direct |
* marks a reported price that did not pass the local price check.