Form 8-K

8-K — Boundless Bio, Inc.

Accession: 0001193125-26-213269

Filed: 2026-05-08

Period: 2026-05-08

CIK: 0001782303

SIC: 2834 (PHARMACEUTICAL PREPARATIONS)

Item: Results of Operations and Financial Condition

Item: Financial Statements and Exhibits

Documents

8-K — bold-20260508.htm (Primary)

EX-99.1 (bold-ex99_1.htm)

GRAPHIC (img6362560_0.jpg)

XML — IDEA: XBRL DOCUMENT (R1.htm)

8-K

8-K (Primary)

Filename: bold-20260508.htm · Sequence: 1

8-K

0001782303false00017823032026-05-082026-05-08

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): May 08, 2026

Boundless Bio, Inc.

(Exact Name of Registrant as Specified in Its Charter)

Delaware

001-41989

83-0751369

(State or Other Jurisdiction

of Incorporation)

(Commission File Number)

(IRS Employer

Identification No.)

10955 Alexandria Way, Suite 100,

San Diego, California

92121

(Address of Principal Executive Offices)

(Zip Code)

Registrant’s Telephone Number, Including Area Code: (858) 766-9912

N/A

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class

Trading

Symbol(s)

Name of each exchange on which registered

Common Stock, par value $0.0001 per share

BOLD

Nasdaq Global Select Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☒

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

Item 2.02 Results of Operations and Financial Condition.

On May 8, 2026, Boundless Bio, Inc. (the Company) issued a press release announcing its financial results for the quarter ended March 31, 2026. A copy of the press release is attached hereto as Exhibit 99.1 and is incorporated herein by reference.

In accordance with General Instruction B.2 of Form 8-K, the information in this Current Report on Form 8-K, including Exhibit 99.1, shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the Exchange Act), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, or the Exchange Act, whether made before or after the date hereof and regardless of any general incorporation by reference language in any such filing, unless the Company specifically states in such filing that such information, or a portion thereof, is to be considered “filed” rather than furnished or incorporated by reference therein.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits.

Exhibit

Number

Description

99.1

Press Release Issued on May 8, 2026

104

Cover Page Interactive Data File (embedded within the Inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

BOUNDLESS BIO, INC.

Date:

May 8, 2026

By:

/s/ Jessica Oien

Name: Jessica Oien

Title: Chief Legal Officer and Corporate Secretary

EX-99.1

Filename: bold-ex99_1.htm · Sequence: 2

EX-99.1

Exhibit 99.1

Boundless Bio Reports First Quarter 2026

Financial Results and Business Highlights

Enrollment proceeding in KOMODO-1 first-in-human clinical trial of BBI-940

$93 million in cash provides runway through expected clinical proof-of-concept

readout for KOMODO-1

SAN DIEGO, May 8, 2026 – Boundless Bio (Nasdaq: BOLD), a clinical-stage oncology company interrogating extrachromosomal DNA (ecDNA) biology to deliver transformative therapies to patients with previously intractable oncogene amplified cancers, today announced financial results and business highlights for the fiscal quarter ended March 31, 2026.

“We are encouraged by the progress of the KOMODO-1 trial," said Zachary Hornby, President and Chief Executive Officer of Boundless Bio. “We continue to expand the body of evidence supporting BBI-940’s kinesin degradation mechanism, with our recent AACR poster demonstrating anti-tumor activity and tumor regression across multiple ecDNA+ cancer models. These findings further strengthen our confidence in the therapeutic potential of BBI-940 as we advance the program through a first-in-human clinical trial.”

Business Highlights and Upcoming Milestones

BBI-940 Novel Kinesin Degrader Clinical Program

•

Enrollment is ongoing in KOMODO-1 (Kinesin Oral Molecular Degrader for Oncology-1), a first-in-human clinical trial of BBI-940 in patients with estrogen receptor positive and human epidermal growth factor receptor 2 negative (ER+/HER2-) breast cancer who have progressed following treatment with a cyclin-dependent kinase 4 and/or 6 (CDK4/6) inhibitor plus endocrine therapy, as well as patients with triple-negative breast cancer luminal androgen receptor subtype (TNBC-LAR).

•

Initial safety and efficacy clinical proof-of-concept data are expected within the Company’s existing cash runway timeline.

Validating Kinesin Degradation Data Presented at 2026 AACR Annual Meeting

•

In vitro and in vivo study data were presented at the American Association for Cancer Research (AACR) Annual Meeting 2026, which demonstrated that genetic depletion and pharmacologic degradation of a novel kinesin (Kinesin) cause ecDNA mis-segregation, ecDNA reduction, and reduced viability of ecDNA positive (ecDNA+) cancer cells.

•

Further, selective degradation of Kinesin in a panel of tumor cell lines demonstrated sensitivity across multiple tumor types, including 32% of breast cancer cell lines, including those positive for ecDNA and FGFR1 gain. This molecularly defined subgroup for Kinesin degradation sensitivity was further validated in vivo with demonstrated monotherapy tumor regressions in an ecDNA+ TNBC-LAR model, and significant antitumor activity as monotherapy and in combination with fulvestrant in an ecDNA+/FGFR1+ ER+ breast cancer model.

First Quarter 2026 Financial Results

•

Cash Position: Cash, cash equivalents, and short-term investments totaled $92.8 million as of March 31, 2026. The Company expects its cash to fund operations into the second half of 2028.

•

Research and Development (R&D) Expenses: R&D expenses were $9.7 million for the first quarter of 2026 compared to $12.1 million for the same period in 2025.

•

General and Administrative (G&A) Expenses: G&A expenses were $4.7 million for the first quarter of 2026 compared to $5.2 million for the same period in 2025.

•

Net Loss: Net loss totaled $13.6 million for the first quarter of 2026 compared to $15.8 million for the same period in 2025.

About Boundless Bio

Boundless Bio is a clinical-stage oncology company dedicated to unlocking a new paradigm in cancer therapeutics that addresses the significant unmet need in patients with oncogene amplified tumors. Boundless Bio’s research focuses on extrachromosomal DNA (ecDNA), a root cause of oncogene amplification observed in 14% to 17% of cancer patients. Boundless Bio is developing BBI-940, a potentially first-in-class, oral, selective Kinesin degrader as an ecDNA-directed therapeutic candidate (ecDTx). Boundless Bio is headquartered in San Diego, California.

For more information, visit https://boundlessbio.com/and follow us on LinkedIn and X.

Forward-Looking Statements

Boundless Bio, Inc. (the Company) cautions you that statements contained in this press release that are not a description of historical facts are forward-looking statements. In some cases, you can identify forward-looking statements by terms such as “anticipate,” “believe,” “contemplate,” “continue,” “could,” “estimate,” “expect,” “intend,” “may,” “plan,” “potential,” “predict,” “project,” “should,” “would,” “target,” or “will” or the negative of these terms or other similar expressions. Forward-looking statements are based on the Company’s current beliefs and expectations and include but are not limited to statements regarding: plans to continue enrollment in and advance the KOMODO-1 trial through initial clinical proof-of-concept data; the expected timing of an initial clinical proof-of-concept readout from the KOMODO-1 trial; the significance of data from preclinical studies of BBI-940; the Company’s cash runway and the sufficiency thereof to fund operations through the anticipated initial clinical proof-of-concept readout from the KOMODO-1 trial; the potential safety and therapeutic benefits of BBI-940 as a monotherapy and in combination with fulvestrant; and BBI-940’s potential to become a first-in-class drug product. The Company’s actual results and performance may differ materially from those expressed or implied in any forward-looking statement due to substantial known and unknown risks and uncertainties, including, without limitation: potential delays in the enrollment, data readouts, or completion of clinical trials or in regulatory submissions and responses; the Company may use its capital resources sooner than it expects; the Company may be unable to obtain necessary additional funding when needed, on acceptable terms, or at all; the Company is early in its development efforts and its approach to discover and develop ecDTx to treat oncogene

amplified cancers is novel and unproven; clinical and preclinical development of therapeutics involves a lengthy and expensive process with inherently uncertain timelines and outcomes; results from preclinical studies or early clinical trials not necessarily being predictive of future results; unexpected adverse side effects or other safety risks or inadequate efficacy of the Company’s ecDTx that may delay or limit their development, regulatory approval, and/or commercialization; the Company’s ability to retain key personnel; the Company’s dependence on third parties in connection with clinical trials, preclinical studies, and manufacturing; the Company may expend its limited resources to pursue a particular ecDTx or combination therapy and fail to capitalize on ecDTx with greater development or commercial potential; the potential for the Company’s programs and prospects to be negatively impacted by developments relating to its competitors, including the results of studies or regulatory determinations relating to its competitors; regulatory and healthcare reform developments in the United States and foreign countries; disruptions or changes at the U.S. Food and Drug Administration (FDA) or other government agencies that limit the FDA’s ability to perform routine activities or function in the normal course or impact the regulatory approval pathway or commercial potential for the Company’s ecDTx; the Company’s ability to obtain, maintain, defend, and enforce patent or other intellectual property protection for its ecDTx and technology; macroeconomic and geopolitical events and conditions, including international trade policies and tariffs, military conflicts, inflation, supply chain disruptions, market volatility, slowed economic growth or recession; and other risks described in the Company’s filings with the Securities and Exchange Commission (SEC), including under the heading “Risk Factors” in the Company’s annual report on Form 10-K for the year ended December 31, 2025 and any subsequent filings with the SEC. You are cautioned not to place undue reliance on forward-looking statements, which speak only as of the date hereof, and, except as required by law, the Company undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.

Investor Contacts:

James Lee, Boundless Bio

jlee@boundlessbio.com

Jon Nugent, THRUST

jon@thrustsc.com

Media Contact:

Carly Scaduto, THRUST

carly@thrustsc.com

BOUNDLESS BIO, INC.

Financial Information (Unaudited)

Condensed Statements of Operations Data:

Three months ended

March 31,

(In thousands, except per share amounts)

2026

2025

Operating expenses:

Research and development

9,734

12,138

General and administrative

4,741

5,203

Total operating expenses

14,475

17,341

Loss from operations

(14,475

)

(17,341

)

Other income, net:

Interest income

920

1,585

Other expense

—

)

Total other income, net

920

1,583

Net loss

(13,555

)

(15,758

)

Net loss per share, basic and diluted

(0.60

)

(0.71

)

Weighted-average shares used in calculation

22,407

22,300

Condensed Balance Sheet Data:

March 31,

December 31,

(In thousands)

2026

2025

Cash, cash equivalents, and short-term investments

92,847

107,581

Total assets

140,970

157,059

Total liabilities

54,587

58,405

Accumulated deficit

273,224

259,669

Total stockholders' equity

85,033

97,074

Working capital (1)

__________

(1) We define working capital as current assets less current liabilities.

GRAPHIC

Filename: img6362560_0.jpg · Sequence: 3

Binary file (106615 bytes)

Download img6362560_0.jpg

XML — IDEA: XBRL DOCUMENT

XML

Filename: R1.htm · Sequence: 6

v3.26.1

Document And Entity Information

May 08, 2026

Cover [Abstract]

Document Type

8-K

Amendment Flag

false

Document Period End Date

May 08, 2026

Entity Registrant Name

Boundless Bio, Inc.

Entity Central Index Key

0001782303

Entity Emerging Growth Company

true

Entity File Number

001-41989

Entity Incorporation, State or Country Code

Entity Tax Identification Number

83-0751369

Entity Address, Address Line One

10955 Alexandria Way, Suite 100,

Entity Address, City or Town

San Diego

Entity Address, State or Province

Entity Address, Postal Zip Code

92121

City Area Code

(858)

Local Phone Number

766-9912

Entity Information, Former Legal or Registered Name

N/A

Written Communications

false

Soliciting Material

false

Pre-commencement Tender Offer

false

Pre-commencement Issuer Tender Offer

false

Entity Ex Transition Period

false

Title of 12(b) Security

Common Stock, par value $0.0001 per share

Trading Symbol

BOLD

Security Exchange Name

NASDAQ

- Definition

Boolean flag that is true when the XBRL content amends previously-filed or accepted submission.

+ References

No definition available.

+ Details

Name:

dei_AmendmentFlag

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Area code of city

+ References

No definition available.

+ Details

Name:

dei_CityAreaCode

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Cover page.

+ References

No definition available.

+ Details

Name:

dei_CoverAbstract

Namespace Prefix:

dei_

Data Type:

xbrli:stringItemType

Balance Type:

Period Type:

duration

- Definition

For the EDGAR submission types of Form 8-K: the date of the report, the date of the earliest event reported; for the EDGAR submission types of Form N-1A: the filing date; for all other submission types: the end of the reporting or transition period. The format of the date is YYYY-MM-DD.

+ References

No definition available.

+ Details

Name:

dei_DocumentPeriodEndDate

Namespace Prefix:

dei_

Data Type:

xbrli:dateItemType

Balance Type:

Period Type:

duration

- Definition

The type of document being provided (such as 10-K, 10-Q, 485BPOS, etc). The document type is limited to the same value as the supporting SEC submission type, or the word 'Other'.

+ References

No definition available.

+ Details

Name:

dei_DocumentType

Namespace Prefix:

dei_

Data Type:

dei:submissionTypeItemType

Balance Type:

Period Type:

duration

- Definition

Address Line 1 such as Attn, Building Name, Street Name

+ References

No definition available.

+ Details

Name:

dei_EntityAddressAddressLine1

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Name of the City or Town

+ References

No definition available.

+ Details

Name:

dei_EntityAddressCityOrTown

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Code for the postal or zip code

+ References

No definition available.

+ Details

Name:

dei_EntityAddressPostalZipCode

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Name of the state or province.

+ References

No definition available.

+ Details

Name:

dei_EntityAddressStateOrProvince

Namespace Prefix:

dei_

Data Type:

dei:stateOrProvinceItemType

Balance Type:

Period Type:

duration

- Definition

A unique 10-digit SEC-issued value to identify entities that have filed disclosures with the SEC. It is commonly abbreviated as CIK.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b-2

+ Details

Name:

dei_EntityCentralIndexKey

Namespace Prefix:

dei_

Data Type:

dei:centralIndexKeyItemType

Balance Type:

Period Type:

duration

- Definition

Indicate if registrant meets the emerging growth company criteria.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b-2

+ Details

Name:

dei_EntityEmergingGrowthCompany

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Indicate if an emerging growth company has elected not to use the extended transition period for complying with any new or revised financial accounting standards.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Securities Act

-Number 7A

-Section B

-Subsection 2

+ Details

Name:

dei_EntityExTransitionPeriod

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Commission file number. The field allows up to 17 characters. The prefix may contain 1-3 digits, the sequence number may contain 1-8 digits, the optional suffix may contain 1-4 characters, and the fields are separated with a hyphen.

+ References

No definition available.

+ Details

Name:

dei_EntityFileNumber

Namespace Prefix:

dei_

Data Type:

dei:fileNumberItemType

Balance Type:

Period Type:

duration

- Definition

Two-character EDGAR code representing the state or country of incorporation.

+ References

No definition available.

+ Details

Name:

dei_EntityIncorporationStateCountryCode

Namespace Prefix:

dei_

Data Type:

dei:edgarStateCountryItemType

Balance Type:

Period Type:

duration

- Definition

Former Legal or Registered Name of an entity

+ References

No definition available.

+ Details

Name:

dei_EntityInformationFormerLegalOrRegisteredName

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

The exact name of the entity filing the report as specified in its charter, which is required by forms filed with the SEC.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b-2

+ Details

Name:

dei_EntityRegistrantName

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

The Tax Identification Number (TIN), also known as an Employer Identification Number (EIN), is a unique 9-digit value assigned by the IRS.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b-2

+ Details

Name:

dei_EntityTaxIdentificationNumber

Namespace Prefix:

dei_

Data Type:

dei:employerIdItemType

Balance Type:

Period Type:

duration

- Definition

Local phone number for entity.

+ References

No definition available.

+ Details

Name:

dei_LocalPhoneNumber

Namespace Prefix:

dei_

Data Type:

xbrli:normalizedStringItemType

Balance Type:

Period Type:

duration

- Definition

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 13e

-Subsection 4c

+ Details

Name:

dei_PreCommencementIssuerTenderOffer

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 14d

-Subsection 2b

+ Details

Name:

dei_PreCommencementTenderOffer

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Title of a 12(b) registered security.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection b

+ Details

Name:

dei_Security12bTitle

Namespace Prefix:

dei_

Data Type:

dei:securityTitleItemType

Balance Type:

Period Type:

duration

- Definition

Name of the Exchange on which a security is registered.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 12

-Subsection d1-1

+ Details

Name:

dei_SecurityExchangeName

Namespace Prefix:

dei_

Data Type:

dei:edgarExchangeCodeItemType

Balance Type:

Period Type:

duration

- Definition

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as soliciting material pursuant to Rule 14a-12 under the Exchange Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Exchange Act

-Number 240

-Section 14a

-Subsection 12

+ Details

Name:

dei_SolicitingMaterial

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration

- Definition

Trading symbol of an instrument as listed on an exchange.

+ References

No definition available.

+ Details

Name:

dei_TradingSymbol

Namespace Prefix:

dei_

Data Type:

dei:tradingSymbolItemType

Balance Type:

Period Type:

duration

- Definition

Boolean flag that is true when the Form 8-K filing is intended to satisfy the filing obligation of the registrant as written communications pursuant to Rule 425 under the Securities Act.

+ References

Reference 1: http://www.xbrl.org/2003/role/presentationRef

-Publisher SEC

-Name Securities Act

-Number 230

-Section 425

+ Details

Name:

dei_WrittenCommunications

Namespace Prefix:

dei_

Data Type:

xbrli:booleanItemType

Balance Type:

Period Type:

duration