SEC Form 4
Boundless Bio, Inc. (BOLD) insider trading
In the 12 months to Oct 30, 2026, 3 BOLD insiders reported open-market sales of $134.0K across 3 filings; one 10% owner bought $1.9M.
Latest filing · Last 12 months · Source: SEC EDGAR · How we count
- Open-market sales
- $134.0K
- 3 filings · 3 insiders
- Open-market purchases
- $1.9M
- 8 filings · Kevin Tang, 10% owner
Who traded BOLD, and when
- Purchase
- Sale
BOLD daily close from Oct 30, 2025 to Oct 29, 2026, between $1.05 and $3.00, last $2.48. 3 sale and 8 purchase filings by 3 insiders, marked at their filing dates. Kevin Tang, 10% owner: sold $54.4K and bought $1.9M across 9 filings, first filed Jun 29, 2026, last Oct 26, 2026. ARCH Venture Partners IX Overage, L.P., 10% owner: sold $39.8K across 1 filing, first filed Jul 6, 2026, last Jul 6, 2026. Robert Nelsen, 10% owner: sold $39.8K across 1 filing, first filed Jul 6, 2026, last Jul 6, 2026.
Largest mark · tap a row for others
Kevin Tang · 10% owner
Filing 1 of 2 within a week · $983,648 total
Purchase $714,768
286,333 shares at $2.50 avg
Filed Jun 29, 2026 · traded Jun 25
Close on filing date $2.45
Kevin Tang · 10% owner
10% owner
$54.4K sold$1.9M boughtARCH Venture Partners IX Overage, L.P. · 10% owner
10% owner
$39.8K soldRobert Nelsen · 10% owner
10% owner
$39.8K soldOpen-market trades
11 filings in the last 12 months| Insider | Role | Sold | Bought | Filings | Pre-arranged (10b5-1) | Last filed |
|---|---|---|---|---|---|---|
| Kevin Tang | 10% owner | $54.4K | $1.9M | 9 | — | |
| ARCH Venture Partners IX Overage, L.P. | 10% owner | $39.8K | — | 1 | — | |
| Robert Nelsen | 10% owner | $39.8K | — | 1 | — |
| Filed | Insider | Type | Shares | Avg price | Value | Held after | Source |
|---|---|---|---|---|---|---|---|
traded | Kevin Tang 10% owner | Purchase | 21,640 | $2.39 | $51.6K | 3,011,749 | |
traded | Kevin Tang 10% owner | Purchase | 149,474 | $2.34 | $349.6K | 2,990,109 | |
traded | Kevin Tang 10% owner | Sale | 18,300 | $2.97 | $54.4K | 2,840,635 | |
traded | Kevin Tang 10% owner | Purchase | 4,863 | $2.44 | $11.9K | 2,858,935 | |
traded | Kevin Tang 10% owner | Purchase | 63,969 | $2.43 | $155.6K | 2,854,072 | |
traded | Kevin Tang 10% owner | Purchase | 91,585 | $2.42 | $222.1K | 2,790,103 | |
traded | Kevin Tang 10% owner | Purchase | 57,210 | $2.48 | $141.9K | 2,698,518 | |
traded | ARCH Venture Partners IX Overage, L.P. 10% owner | Sale | 16,000 | $2.49 | $39.8K | 0 | |
traded | Robert Nelsen 10% owner | Sale | 16,000 | $2.49 | $39.8K | 0 | |
traded | Kevin Tang 10% owner | Purchase | 107,463 | $2.50 | $268.9K | 2,641,308 | |
traded | Kevin Tang 10% owner | Purchase | 286,333 | $2.50 | $714.8K | 2,533,068 |
GET /stocks/filings/vX/form-4?tickers=BOLD&filing_date.gte=2025-10-30&sort=filing_date.desc&limit=500{
"status": "OK",
"results": [
{
"tickers": [
"BOLD"
],
"issuer_cik": "0001782303",
"owner_cik": "0001178579",
"accession_number": "0001178579-26-000020",
"form_type": "4",
"filing_date": "2026-10-26",
"period_of_report": "2026-10-22",
"issuer_name": "Boundless Bio, Inc.",
"issuer_trading_symbol": "BOLD",
"owner_name": "TANG KEVIN",
"is_director": false,
"is_officer": false,
"is_ten_percent_owner": true,
"is_other": false,
"security_type": "non_derivative",
"record_type": "transaction",
"security_title": "Common Stock",
"transaction_timeliness": "O",
"aff_10b5_one": false,
"transaction_date": "2026-10-26",
"transaction_code": "P",
"equity_swap_involved": false,
"transaction_shares": 9606,
"transaction_price_per_share": 2.38,
"transaction_acquired_disposed": "A",
"shares_owned_following_transaction": 3011749,
"transaction_value": 22862.28,
"direct_or_indirect": "I",
"nature_of_ownership": "See Footnote",
"footnotes": [
{
"id": "F4",
"description": "These shares were purchased in multiple transactions at prices ranging from $2.37 to $2.40."
},
{
"id": "F2",
"description": "Tang Capital Partners, LP (\"TCP\") beneficially owns 691,177 shares, Tang Capital Partners International, LP (\"TCPI\") beneficially owns 950,804 shares, Tang Capital Partners III, Inc. (\"TCP III\") beneficially owns 691,170 shares, and Tang Capital Partners IV, Inc. (\"TCP IV\") beneficially owns 678,598 shares. Kevin Tang is the sole manager of Tang Capital Management, LLC, which is the general partner of TCP and TCPI. Kevin Tang is the sole director and Chief Executive Officer of TCP III and TCP IV, which are indirectly wholly owned by TCP. Mr. Tang has a pecuniary interest in the shares beneficially held by TCP, TCPI, TCP III and TCP IV."
}
]
},
{
"tickers": [
"BOLD"
],
"issuer_cik": "0001782303",
"owner_cik": "0001178579",
"accession_number": "0001178579-26-000020",
"form_type": "4",
"filing_date": "2026-10-26",
"period_of_report": "2026-10-22",
"issuer_name": "Boundless Bio, Inc.",
"issuer_trading_symbol": "BOLD",
"owner_name": "TANG KEVIN",
"is_director": false,
"is_officer": false,
"is_ten_percent_owner": true,
"is_other": false,
"security_type": "non_derivative",
"record_type": "transaction",
"security_title": "Common Stock",
"transaction_timeliness": "O",
"aff_10b5_one": false,
"transaction_date": "2026-10-22",
"transaction_code": "P",
"equity_swap_involved": false,
"transaction_shares": 5800,
"transaction_price_per_share": 2.4,
"transaction_acquired_disposed": "A",
"shares_owned_following_transaction": 2995909,
"transaction_value": 13920,
"direct_or_indirect": "I",
"nature_of_ownership": "See Footnote",
"footnotes": [
{
"id": "F1",
"description": "The prices reported are weighted-average prices. These shares were purchased in multiple transactions at prices ranging from $2.39 to $2.40. The Reporting Persons undertake to provide the Issuer, any security holder of the Issuer or the SEC staff, upon request, all information regarding the number of shares purchased at each price within the range set forth in Footnotes 1 and 3 through 4."
},
{
"id": "F2",
"description": "Tang Capital Partners, LP (\"TCP\") beneficially owns 691,177 shares, Tang Capital Partners International, LP (\"TCPI\") beneficially owns 950,804 shares, Tang Capital Partners III, Inc. (\"TCP III\") beneficially owns 691,170 shares, and Tang Capital Partners IV, Inc. (\"TCP IV\") beneficially owns 678,598 shares. Kevin Tang is the sole manager of Tang Capital Management, LLC, which is the general partner of TCP and TCPI. Kevin Tang is the sole director and Chief Executive Officer of TCP III and TCP IV, which are indirectly wholly owned by TCP. Mr. Tang has a pecuniary interest in the shares beneficially held by TCP, TCPI, TCP III and TCP IV."
}
]
}
]
}
// trimmed to 2 resultsThe response includes every Form 4 record; this page keeps open-market purchases and sales on common stock and removes duplicate joint-filer rows.
Other insider activity (not market trades) · 2 records
- Option exercises2 records
Reported on Form 4 but not purchases or sales in the market, so not counted in the totals above.
How to read this page
- Open-market purchase or sale
- A buy or sell of the company's stock at market price. Grants, option exercises, shares withheld for tax, gifts and employee stock plan purchases are listed separately and not counted.
- Filing date
- Insiders have two business days to report a trade. Totals and the chart use the filing date, when the trade became public.
- Counted once
- When several owners (a fund and its partners, say) report the same trade, it's counted once. Corrected filings replace the originals.
Frequently asked questions
Has Boundless Bio, Inc.'s CEO sold stock?
No. Zachary Hornby (CEO) made no open-market sales filed as CEO in the last 12 months.
How current is BOLD’s insider data?
These are BOLD Form 4 filings from the last year, refreshed daily. The Massive Form 4 API has the full, continuously updated record.
What counts as an open-market buy or sell?
Only purchases and sales at the market price. Option exercises, grants, gifts, and shares withheld for taxes are reported on Form 4 but are left out of the buy and sell totals.
Build with AI
Track BOLD insider trades with your agent
This page joins two Massive endpoints: Form 4 filings and daily prices. Ask an agent to watch for new filings:
Using the Massive API (massive.com/docs/llms.txt), check Form 4 filings for BOLD every day with transaction_code=P and tell me when an insider files an open-market purchase, with their role, shares, price and the filing link.
Nothing on this page is investment advice. All data and content is provided for informational purposes under our Terms of Service.