What SEC filings does Boundless Bio, Inc. submit to the SEC?

Boundless Bio, Inc. (BOLD) submits several types of SEC filings including Form 4 (insider transactions), Form 144 (proposed insider sales), 8-K reports (material events such as earnings releases, acquisitions, leadership changes), and periodic reports — the 10-Q (quarterly) and 10-K (annual). All filings are publicly available through SEC EDGAR.

What does a Form 4 filing tell me about BOLD?

A Form 4 for BOLD discloses a transaction by a company insider — typically a director, officer, or 10%+ shareholder. It shows the source-reported date, number of shares, price, and updated ownership. These facts do not establish motive or predict future returns.

How do I interpret an 8-K filing from Boundless Bio, Inc.?

An 8-K signals a material event requiring prompt disclosure. Common triggers include earnings pre-announcements, acquisitions, leadership appointments or departures, credit changes, or regulatory actions. Read the item codes inside the filing to understand exactly what was disclosed before drawing conclusions.

What is the difference between a 10-K and 10-Q for BOLD?

The 10-K is Boundless Bio, Inc.'s annual report with fully audited financial statements, comprehensive MD&A, and complete risk factor disclosures — filed 60–90 days after fiscal year-end. The 10-Q is a lighter quarterly report with unaudited financials filed for the first three quarters. Together they provide a continuous financial picture of the company.

Where can I see all BOLD SEC filings directly on EDGAR?

You can view all historical Boundless Bio, Inc. filings on the SEC EDGAR company page for BOLD. Each filing card on this page links directly to the original SEC document.

How often does Boundless Bio, Inc. file with the SEC?

Boundless Bio, Inc. files one 10-K per year and up to three 10-Qs per year. Form 4 insider transactions must be reported within two business days of each trade, so the frequency depends on how often insiders are buying or selling BOLD shares. 8-K filings occur whenever a material event happens — which can be several times per quarter for an active company.

BOLD SEC Filing News — Boundless Bio, Inc.

Latest SEC filings for Boundless Bio, Inc. (BOLD) explained in plain English. Covers insider buying and selling (Form 4), proposed insider sales (Form 144), material company events (8-K), and quarterly & annual reports (10-Q / 10-K). StrongBuyAnalytics provides navigation and brief excerpts or summaries; original filings remain at the SEC/source links and were authored by their filers, not StrongBuyAnalytics. Filing dates shown are source dates. Coverage and detection can be delayed or incomplete because of SEC availability, amendments, parsing, caching, or outages. Latest source filing date shown: 2026-08-28.

Boundless Bio, Inc., a clinical-stage oncology company, develops interrogating extrachromosomal DNA (ecDNA) directed therapies for treating patients with oncogene amplified cancers. Its lead product candidate is BBI-940, an ecDNA-directed therapeutic candidate (ecDTx) that is in Phase 1/2 clinical trial in patients with estrogen receptor positive and human epidermal growth factor receptor 2 negative breast cancer, as well as patients with triple-negative breast cancer luminal androgen receptor s…

Sector: Healthcare Industry: Biotechnology Market Cap: $53.4M

Total Filings

Bullish Classifications

Bearish Classifications

Insider Transactions

Material Events (8-K)

Periodic Reports

Rule-based classifications for BOLD currently lean bullish. Of the 20 displayed SEC filing records, 6 carry bullish classifications versus 3 bearish classifications. These labels summarize filing attributes; they are not recommendations, probabilities, or evidence of future price direction. There were 13 insider transactions (Form 4) in this period.

BOLD Filing Activity Snapshot 2026-04-13 — 2026-08-28

Insider Transactions (Form 4)

6 buys vs 3 sells

Net insider buying in this period — more purchases than sales reported.

Largest Form 144 Filing

$714.8K

TANG KEVIN (10% Owner) · 2026-06-29

286,333 shares · Form 4

Insider Transactions 13 · Forms 3, 4 and 5

A Form 4 is filed within two business days of a company insider — an officer, a director, or a holder of more than ten percent of the stock — changing their position in the shares. All 13 filings in this group are Form 4s for Boundless Bio, Inc.

The difficulty with reading these filings as a group is that a single form type covers transactions that mean entirely different things. An executive spending their own money to buy stock and an executive having shares withheld to pay tax on a vesting grant both appear as a Form 4. Every filing below is therefore tagged with the nature of the underlying transaction, taken from the transaction code reported on the form itself.

Across the 13 insider filings shown, the breakdown is 6 open-market purchase, 4 compensation award and 3 open-market sale. 9 of them involved a discretionary open-market trade; the rest are compensation and administrative mechanics.

What each transaction type means

Open-market purchase ×6: The insider bought shares on the open market with their own money. This is the only Form 4 category that requires a discretionary cash outlay at the prevailing price.
Compensation award ×4: Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.
Open-market sale ×3: The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Form 4 Open-market sale Insider Selling 2026-08-28

BOLD insider TANG KEVIN (10% Owner) sold 18,300 shares (~$54.4K)

TANG KEVIN, listed as 10% Owner at Boundless Bio, Inc., reported an open-market sale of 18,300 BOLD shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`S`	Open-market sale	18,300	$2.97	$54.4K

Filing: Form 4 (Insider Transaction) Insider: TANG KEVIN (10% Owner) Shares: 18,300 Est. Value: $54.4K

View on SEC EDGAR → Open Filing Document →

Form 4 Open-market purchase Insider Buying 2026-07-21

BOLD insider TANG KEVIN (10% Owner) bought 4,863 shares (~$11.9K)

TANG KEVIN, listed as 10% Owner at Boundless Bio, Inc., reported an open-market purchase of 4,863 BOLD shares in a Form 4 filing. Insider buying is often treated as a bullish signal because company insiders are committing their own capital.

The insider bought shares on the open market with their own money. This is the only Form 4 category that requires a discretionary cash outlay at the prevailing price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`P`	Open-market purchase	265	$2.44	$646.60
`P`	Open-market purchase	1,623	$2.44	$4.0K
`P`	Open-market purchase	2,975	$2.44	$7.3K

Filing: Form 4 (Insider Transaction) Insider: TANG KEVIN (10% Owner) Shares: 4,863 Est. Value: $11.9K

View on SEC EDGAR → Open Filing Document →

Form 4 Open-market purchase Insider Buying 2026-07-16

BOLD insider TANG KEVIN (10% Owner) bought 63,969 shares (~$155.6K)

TANG KEVIN, listed as 10% Owner at Boundless Bio, Inc., reported an open-market purchase of 63,969 BOLD shares in a Form 4 filing. Insider buying is often treated as a bullish signal because company insiders are committing their own capital.

The insider bought shares on the open market with their own money. This is the only Form 4 category that requires a discretionary cash outlay at the prevailing price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`P`	Open-market purchase	43,878	$2.43	$106.6K
`P`	Open-market purchase	1,600	$2.44	$3.9K
`P`	Open-market purchase	18,491	$2.44	$45.1K

Filing: Form 4 (Insider Transaction) Insider: TANG KEVIN (10% Owner) Shares: 63,969 Est. Value: $155.6K

View on SEC EDGAR → Open Filing Document →

Form 4 Open-market purchase Insider Buying 2026-07-13

BOLD insider TANG KEVIN (10% Owner) bought 91,585 shares (~$222.1K)

TANG KEVIN, listed as 10% Owner at Boundless Bio, Inc., reported an open-market purchase of 91,585 BOLD shares in a Form 4 filing. Insider buying is often treated as a bullish signal because company insiders are committing their own capital.

The insider bought shares on the open market with their own money. This is the only Form 4 category that requires a discretionary cash outlay at the prevailing price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`P`	Open-market purchase	7	$2.48	$17.36
`P`	Open-market purchase	43,367	$2.43	$105.4K
`P`	Open-market purchase	48,211	$2.42	$116.7K

Filing: Form 4 (Insider Transaction) Insider: TANG KEVIN (10% Owner) Shares: 91,585 Est. Value: $222.1K

View on SEC EDGAR → Open Filing Document →

Form 4 Open-market purchase Insider Buying 2026-07-08

BOLD insider TANG KEVIN (10% Owner) bought 57,210 shares (~$141.9K)

TANG KEVIN, listed as 10% Owner at Boundless Bio, Inc., reported an open-market purchase of 57,210 BOLD shares in a Form 4 filing. Insider buying is often treated as a bullish signal because company insiders are committing their own capital.

The insider bought shares on the open market with their own money. This is the only Form 4 category that requires a discretionary cash outlay at the prevailing price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`P`	Open-market purchase	27,062	$2.49	$67.4K
`P`	Open-market purchase	15,810	$2.48	$39.2K
`P`	Open-market purchase	14,338	$2.46	$35.3K

Filing: Form 4 (Insider Transaction) Insider: TANG KEVIN (10% Owner) Shares: 57,210 Est. Value: $141.9K

View on SEC EDGAR → Open Filing Document →

Form 4 Open-market sale Insider Selling 2026-07-06

BOLD insider CRANDELL KEITH (10% Owner) sold 16,000 shares (~$39.8K)

CRANDELL KEITH, listed as 10% Owner at Boundless Bio, Inc., reported an open-market sale of 16,000 BOLD shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`M`	Option exercise	16,000	$1.03	$16.5K
`S`	Open-market sale	16,000	$2.49	$39.8K
`M`	Option exercise derivative · Stock Option (right to buy)	16,000	—	—

Filing: Form 4 (Insider Transaction) Insider: CRANDELL KEITH (10% Owner) Shares: 16,000 Est. Value: $39.8K

View on SEC EDGAR → Open Filing Document →

Form 4 Open-market sale Insider Selling 2026-07-06

BOLD insider ARCH Venture Fund IX, L.P. (10% Owner) sold 16,000 shares (~$39.8K)

ARCH Venture Fund IX, L.P., listed as 10% Owner at Boundless Bio, Inc., reported an open-market sale of 16,000 BOLD shares in a Form 4 filing. This is a confirmed insider sale, not just a proposed sale notice.

The insider sold shares on the open market. Sales may be discretionary or executed automatically under a pre-arranged Rule 10b5-1 trading plan, and a Form 4 does not always make clear which applies.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`M`	Option exercise	16,000	$1.03	$16.5K
`S`	Open-market sale	16,000	$2.49	$39.8K
`M`	Option exercise derivative · Stock Option (right to buy)	16,000	—	—

Filing: Form 4 (Insider Transaction) Insider: ARCH Venture Fund IX, L.P. (10% Owner) Shares: 16,000 Est. Value: $39.8K

View on SEC EDGAR → Open Filing Document →

Form 4 Open-market purchase Insider Buying 2026-07-02

BOLD insider TANG KEVIN (10% Owner) bought 107,463 shares (~$268.9K)

TANG KEVIN, listed as 10% Owner at Boundless Bio, Inc., reported an open-market purchase of 107,463 BOLD shares in a Form 4 filing. Insider buying is often treated as a bullish signal because company insiders are committing their own capital.

The insider bought shares on the open market with their own money. This is the only Form 4 category that requires a discretionary cash outlay at the prevailing price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`P`	Open-market purchase	25,930	$2.54	$65.9K
`P`	Open-market purchase	100	$2.50	$250.00
`P`	Open-market purchase	71,612	$2.49	$178.3K
`P`	Open-market purchase	9,821	$2.49	$24.5K

Filing: Form 4 (Insider Transaction) Insider: TANG KEVIN (10% Owner) Shares: 107,463 Est. Value: $268.9K

View on SEC EDGAR → Open Filing Document →

Form 4 Open-market purchase Insider Buying 2026-06-29

BOLD insider TANG KEVIN (10% Owner) bought 286,333 shares (~$714.8K)

TANG KEVIN, listed as 10% Owner at Boundless Bio, Inc., reported an open-market purchase of 286,333 BOLD shares in a Form 4 filing. Insider buying is often treated as a bullish signal because company insiders are committing their own capital.

The insider bought shares on the open market with their own money. This is the only Form 4 category that requires a discretionary cash outlay at the prevailing price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`P`	Open-market purchase	145,880	$2.48	$361.8K
`P`	Open-market purchase	510	$2.56	$1.3K
`P`	Open-market purchase	75,047	$2.55	$191.4K
`P`	Open-market purchase	134	$2.54	$340.36
`P`	Open-market purchase	63,985	$2.47	$158.0K
`P`	Open-market purchase	777	$2.48	$1.9K

Filing: Form 4 (Insider Transaction) Insider: TANG KEVIN (10% Owner) Shares: 286,333 Est. Value: $714.8K

View on SEC EDGAR → Open Filing Document →

Form 4 Compensation award Tax / Compensation Filing 2026-06-15

BOLD insider Form 4 filed for equity award, exercise, or tax withholding

Whiting Nancy (Director) filed a Form 4 covering compensation-related activity such as stock awards, option exercises, conversions, or tax withholding. These filings are usually neutral.

Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`A`	Compensation award derivative · Stock Option (right to buy)	32,000	—	—

Filing: Form 4 (Insider Transaction) Insider: Whiting Nancy (Director)

View on SEC EDGAR → Open Filing Document →

Form 4 Compensation award Tax / Compensation Filing 2026-06-15

BOLD insider Form 4 filed for equity award, exercise, or tax withholding

Lim Jonathan E (Director) filed a Form 4 covering compensation-related activity such as stock awards, option exercises, conversions, or tax withholding. These filings are usually neutral.

Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`A`	Compensation award derivative · Stock Option (right to buy)	48,000	—	—

Filing: Form 4 (Insider Transaction) Insider: Lim Jonathan E (Director)

View on SEC EDGAR → Open Filing Document →

Form 4 Compensation award Tax / Compensation Filing 2026-06-15

BOLD insider Form 4 filed for equity award, exercise, or tax withholding

Christensen James (Director) filed a Form 4 covering compensation-related activity such as stock awards, option exercises, conversions, or tax withholding. These filings are usually neutral.

Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`A`	Compensation award derivative · Stock Option (right to buy)	32,000	—	—

Filing: Form 4 (Insider Transaction) Insider: Christensen James (Director)

View on SEC EDGAR → Open Filing Document →

Form 4 Compensation award Tax / Compensation Filing 2026-06-15

BOLD insider Form 4 filed for equity award, exercise, or tax withholding

Lew Jennifer (Director) filed a Form 4 covering compensation-related activity such as stock awards, option exercises, conversions, or tax withholding. These filings are usually neutral.

Shares were granted as compensation rather than purchased. No cash changed hands, so the filing reflects a pay decision by the company, not a judgement about the price.

Transactions reported on this filing
Code	Nature	Shares	Price	Value
`A`	Compensation award derivative · Stock Option (right to buy)	32,000	—	—

Filing: Form 4 (Insider Transaction) Insider: Lew Jennifer (Director)

View on SEC EDGAR → Open Filing Document →

Material Events 5 · Form 8-K

An 8-K reports a material event in the window between scheduled reports. There are 5 in this period for Boundless Bio, Inc. Each 8-K names the item number it is filed under, and that number is the fastest way to tell a routine disclosure from a consequential one.

Item 2.02 is an earnings release, Item 5.02 is a change of directors or officers, and Item 1.01 or 2.01 covers a material agreement or a completed acquisition. Item 7.01 and Item 8.01 are the general-purpose disclosure items and carry no fixed meaning on their own.

Form 8-K Material Company Update 2026-08-28

BOLD filed 8-K — material company event

Boundless Bio, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)

View on SEC EDGAR → Open Filing Document →

Form 8-K Material Company Update 2026-06-23

BOLD filed 8-K — material company event

Boundless Bio, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)

View on SEC EDGAR → Open Filing Document →

Form 8-K Material Company Update 2026-06-17

BOLD filed 8-K — material company event

Boundless Bio, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)

View on SEC EDGAR → Open Filing Document →

Form 8-K Material Company Update 2026-05-08

BOLD filed 8-K — material company event

Boundless Bio, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)

View on SEC EDGAR → Open Filing Document →

Form 8-K Material Company Update 2026-04-13

BOLD filed 8-K — material company event

Boundless Bio, Inc. filed an 8-K with the SEC reporting a material event. Summary unavailable — view the original SEC filing for the full text.

Filing: 8-K (Material Event)

View on SEC EDGAR → Open Filing Document →

Periodic Reports 2 · Forms 10-K and 10-Q

The periodic reports are where the audited and reviewed financial statements live. This period contains 2 quarterly reports (10-Q) for Boundless Bio, Inc.

The two are not equivalent in weight. A 10-K is audited by an external firm and includes the full risk factor disclosure, business description and management discussion; a 10-Q is unaudited, reviewed rather than examined, and much shorter. When a figure in a quarterly report is later revised, the annual report is usually where the correction appears.

An amended report — 10-K/A or 10-Q/A — restates or corrects something in the original filing, and is worth reading against the version it replaces.

Form 10-Q Quarterly Report 2026-08-07

BOLD filed Quarterly Report (10-Q)

Boundless Bio, Inc. filed its quarterly report with the SEC. This report includes unaudited financial statements and management discussion for the quarter.

Filing: 10-Q (Quarterly Report)

View on SEC EDGAR → Open Filing Document →

Form 10-Q Quarterly Report 2026-05-08

BOLD filed Quarterly Report (10-Q)

Boundless Bio, Inc. filed its quarterly report with the SEC. This report includes unaudited financial statements and management discussion for the quarter.

Filing: 10-Q (Quarterly Report)

View on SEC EDGAR → Open Filing Document →

How we classify Boundless Bio, Inc.'s filings

Straight from EDGAR

Each displayed record links to an original source document. StrongBuyAnalytics provides navigation and brief excerpts or summaries, not the filing itself. Parsing may omit context or contain errors, so read the original document in full.

Transaction codes, not guesswork

The nature shown on each insider filing comes from the transaction code the filer entered on the form itself — P for an open-market purchase, A for a compensation award, F for shares withheld to pay tax, M for an option exercise. Where one filing contains several codes, the transaction table lists them line by line.

Why the distinction matters

Insider activity is routinely summarised as buying or selling, which flattens together decisions that mean very different things. Shares withheld for tax on a vesting grant are an automatic administrative step; shares bought on the open market are someone committing their own money at the current price.

What this page does not tell you

A filing records what happened, not why. Form 4 does not always disclose whether a sale was executed under a pre-arranged Rule 10b5-1 plan, and no single filing is a basis for a decision on BOLD. Read these alongside the fundamentals rather than in isolation.

Frequently Asked Questions — BOLD SEC Filings

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Publisher, sources & limitations — September 15, 2026. StrongBuyAnalytics provides navigation and brief excerpts or summaries for educational use. Original filings remain at SEC EDGAR or other displayed source links; StrongBuyAnalytics does not author them. Filing dates are source dates, not publication dates for this page. Coverage can be delayed, incomplete, amended, or unavailable because of SEC/source availability, parsing, caching, or outages. Verify every material statement in the original filing.

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