Boundless Bio, Inc.

Previous wording

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our unaudited condensed financial statements and notes thereto included elsewhere in this Quarterly Report on Form 10-Q and with our audited financial statements and notes thereto and management’s discussion and analysis of financial condition and results of operations for the year ended December 31, 2025, included in our 2025 10-K. This discussion and analysis contains forward-looking statements that involve risks and uncertainties, including those described in the section titled “Special Note Regarding Forward Looking Statements and Market and Industry Data.” As a result of many factors, including those factors set forth in the “Risk Factors” section of this Quarterly Report and our 2025 10-K, our actual results and the timing of events could differ materially from the results and timing described in or implied by the forward-looking statements contained in the following discussion and analysis. Unless the context requires otherwise, references in this report to “Boundless Bio,” the “Company,” “we,” “us,” and “our” refer to Boundless Bio, Inc. prior to consummation of the Merger. In addition, in this report we refer to our extrachromosomal DNA directed therapeutic candidates as “ecDTx,” which until recently were under clinical or preclinical investigation and which have not yet been approved for marketing by the FDA or any other regulatory authority.

Current wording

The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our unaudited condensed financial statements and notes thereto included elsewhere in this Quarterly Report on Form 10-Q and with our audited financial statements and notes thereto and management’s discussion and analysis of financial condition and results of operations for the year ended December 31, 2025, included in our 2025 10-K. This discussion and analysis contains forward-looking statements that involve risks and uncertainties, including those described in the section titled “Special Note Regarding Forward Looking Statements and Market and Industry Data.” As a result of many factors, including those factors set forth in the “Risk Factors” section of our Q2 2026 10-Q and our 2025 10-K, our actual results and the timing of events could differ materially from the results and timing described in or implied by the forward-looking statements contained in the following discussion and analysis. Unless the context requires otherwise, references in this report to “Boundless Bio,” the “Company,” “we,” “us,” and “our” refer to Boundless Bio, Inc. prior to consummation of the Merger. In addition, in this report we refer to our extrachromosomal DNA directed therapeutic candidates as “ecDTx,” which until recently were under clinical or preclinical investigation and which have not yet been approved for marketing by the FDA or any other regulatory authority.

Previous wording

We are 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 by interrogating extrachromosomal DNA (ecDNA), a root cause of oncogene amplification observed in 14 to 17% of cancer patients.

Current wording

We are 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 by interrogating extrachromosomal DNA (ecDNA), a root cause of oncogene amplification observed in 14% to 17% of cancer patients.

Previous wording

Our lead ecDTx, BBI-940, is a novel, oral, selective degrader that targets a previously undrugged kinesin involved in DNA segregation, including ecDNA segregation during mitosis. In February 2026, we initiated the KOMODO-1 trial, a Phase 1, open-label, multicenter, first-in-human clinical trial of BBI-940 in patients with estrogen receptor positive and human epidermal growth factor receptor 2 negative, or ER+/HER2-, breast cancer who have progressed following treatment with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6 inhibitor) plus endocrine therapy, as well as patients with triple-negative breast cancer luminal androgen receptor subtype (TNBC-LAR). In June 2026, we announced that based on preliminary exposure data obtained in the early dose escalation cohorts of the KOMODO-1 clinical trial, we believed that the observed pharmacokinetic exposure data, indicating that human oral bioavailability of BBI-940 was significantly lower than what had been predicted based on preclinical studies, did not support continued clinical development of BBI-940.

Current wording

We had been investigating BBI-355, a novel, oral, selective inhibitor of checkpoint kinase 1 designed to target replication stress in oncogene amplified cancers, and BBI-825, a novel, oral, selective inhibitor of ribonucleotide reductase, in the clinic in the POTENTIATE trial and the STARMAP trial. As previously reported, we made decisions to cease enrollment in each of these trials, and, accordingly, we also do not plan to invest further in the development of ECHO, which is an ecDNA diagnostic clinical trial assay used in the POTENTIATE trial. We have completed winding down both the STARMAP trial and the POTENTIATE trial. In January 2026, we focused our research and development activities on BBI-940, a novel, oral, selective degrader that targets a previously undrugged kinesin involved in DNA segregation, including ecDNA segregation during mitosis. In February 2026, we initiated the KOMODO-1 trial, a Phase 1, open-label, multicenter, first-in-human clinical trial of BBI-940 in patients with estrogen receptor positive and human epidermal growth factor receptor 2 negative, or ER+/HER2-, breast cancer who had progressed following treatment with a cyclin-dependent kinase 4/6 inhibitor (CDK4/6 inhibitor) plus endocrine therapy, as well as patients with triple-negative breast cancer luminal androgen receptor subtype (TNBC-LAR). In June 2026, we announced that based on preliminary exposure data obtained in the early dose escalation cohorts of the KOMODO-1 clinical trial, we believed that the observed pharmacokinetic exposure data, indicating that human oral bioavailability of BBI-940 was significantly lower than what had been predicted based on preclinical studies, did not support continued clinical development of BBI-940. For additional information, see “Other Programs” in Part I, Item 1., “Business,” of our 2025 10-K.

Previous wording

Spyglass is our internal proprietary platform used to identify new targets. We utilized Spyglass to identify targets that exploit cellular vulnerabilities of oncogene amplified cancers. Our target identification efforts revealed multiple distinct nodes of vulnerability within the lifecycle of ecDNA. In addition to the program described above, we have preclinically validated multiple additional targets and have historically initiated ecDTx drug discovery efforts to identify potential candidates against such targets.

Current wording

Spyglass is our internal proprietary platform that we used to identify new targets. We utilized Spyglass to identify targets that exploit cellular vulnerabilities of oncogene amplified cancers. Our target identification efforts revealed multiple distinct nodes of vulnerability within the lifecycle of ecDNA. In addition to the programs described above, we preclinically validated multiple additional targets and have historically initiated ecDTx drug discovery efforts to identify potential candidates against such targets.

Previous wording

Since we commenced operations in 2018, we have devoted substantially all of our efforts and resources to organizing and staffing our company, business planning, raising capital, building our proprietary Spyglass platform, discovering our ecDTx, developing our diagnostic, establishing our intellectual property portfolio, conducting research, preclinical studies, and clinical trials, establishing arrangements with third parties for the manufacture of our ecDTx and related raw materials, and providing general and administrative support for these operations. During this time, we have incurred significant operating losses and, as of June 30, 2026, we had an accumulated deficit of $296.9 million. We expect to continue to incur losses for the foreseeable future, and, in general, we anticipate these losses will increase substantially in the future if we continue our development of, seek regulatory approval for, and potentially commercialize our current or any future ecDTx, conduct any clinical trials and preclinical studies, utilize third parties to manufacture our ecDTx and related raw materials, leverage Spyglass to potentially identify additional development opportunities for our ecDTx and expand our therapeutic pipeline, seek to expand and protect our intellectual property, as well as incur additional costs associated with being a public company. If we obtain regulatory approval for our ecDTx, we expect to incur significant commercialization expenses related to product sales, marketing, manufacturing, and distribution. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending on the timing of our clinical trials, preclinical studies, and our other research and development activities and capital expenditures.

Current wording

Since we commenced operations in 2018, we have devoted substantially all of our efforts and resources to organizing and staffing our company, business planning, raising capital, building our proprietary Spyglass platform, discovering our ecDTx, developing our diagnostic, establishing our intellectual property portfolio, conducting research, preclinical studies, and clinical trials, establishing arrangements with third parties for the manufacture of our ecDTx and related raw materials, and providing general and administrative support for these operations. During this time, we have incurred significant operating losses and, as of September 30, 2026, we had an accumulated deficit of $302.3 million. We expect to continue to incur losses for the foreseeable future, and, in general, we anticipate these losses will increase substantially in the future if we continue our development of, seek regulatory approval for, and potentially commercialize our current or any future ecDTx, conduct any clinical trials and preclinical studies, utilize third parties to manufacture our ecDTx and related raw materials, leverage Spyglass to potentially identify additional development opportunities for our ecDTx and expand our therapeutic pipeline, seek to expand and protect our intellectual property, as well as incur additional costs associated with being a public company. If we obtain regulatory approval for our ecDTx, we expect to incur significant commercialization expenses related to product sales, marketing, manufacturing, and distribution. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending on the timing of our clinical trials, preclinical studies, and our other research and development activities and capital expenditures.

Previous wording

Through June 30, 2026, we have raised a total of $353.9 million to fund our operations primarily from the gross proceeds from the sale and issuance of our convertible preferred and common stock. In April 2024, we completed our IPO, in which we sold and issued 6,250,000 shares of our common stock for gross proceeds of $100.0 million. In April 2025, we commenced an “at the market” (ATM) offering as defined in Rule 415(a)(4) under the Securities Act, under which we may offer and sell shares of our common stock having an aggregate offering price of up to $14.5 million from time to time through or to our sales agent, as described further under “Liquidity and Capital Resources” below. As of June 30, 2026, we had cash, cash equivalents, and short-term investments of $72.6 million.

Current wording

Through September 30, 2026, we have raised a total of $354.7 million to fund our operations primarily from the gross proceeds from the sale and issuance of our convertible preferred and common stock. In April 2024, we completed our IPO, in which we sold and issued 6,250,000 shares of our common stock for gross proceeds of $100.0 million. In April 2025, we commenced an “at the market” (ATM) offering as defined in Rule 415(a)(4) under the Securities Act, under which we may offer and sell shares of our common stock having an aggregate offering price of up to $14.5 million from time to time through or to our sales agent, as described further under “Liquidity and Capital Resources” below. While the Merger is pending, the Merger Agreement prohibits us from issuing shares of our capital stock, including under the Sales Agreement, without Serapha’s consent (except for Company shares issued upon valid exercise of outstanding Company options). As of September 30, 2026, we had cash, cash equivalents, and short-term investments of $62.9 million.

Previous wording

In response to clinical data and other market considerations, we have made a series of portfolio prioritization decisions and taken steps to streamline operations in connection with those decisions. In January 2026, we focused our research and development activities on BBI-940. In April 2026, we further streamlined our operations by restructuring our facilities footprint, terminating our long-term lease (the 2024 Lease) for approximately 80,168 rentable square feet of laboratory and office space in San Diego effective May 31, 2026, and entering into a new, shorter-term lease for approximately 10,822 rentable square feet at a nearby location commencing June 1, 2026. The 2024 Lease termination involved a cash payment of $10.0 million by us to the landlord, and the landlord’s retention of our security deposit of approximately $0.5 million.

Current wording

In response to clinical data and other market considerations, we have made a series of portfolio prioritization decisions and taken steps to streamline operations in connection with those decisions. In January 2026, we focused our research and development activities on BBI-940. In April 2026, we further streamlined our operations by restructuring our facilities footprint, terminating our long-term lease (the 2024 Lease) for approximately 80,168 rentable square feet of laboratory and office space in San Diego effective May 31, 2026, and entering into a new, shorter-term lease (the 2026 Lease) for approximately 10,822 rentable square feet at a nearby location commencing June 1, 2026. The 2024 Lease termination involved a cash payment of $10.0 million by us to the landlord, and the landlord’s retention of our security deposit of approximately $0.5 million. In June 2026, we announced that based on preliminary exposure data from the KOMODO-1 trial, we believed that the observed pharmacokinetic exposure data, indicating that human oral bioavailability of BBI-940 was significantly lower than what had been predicted based on preclinical studies, did not support continued development of BBI-940. We also entered into the Merger Agreement and announced a reduction in workforce of approximately 75%. In August 2026, we amended the 2026 Lease to pay all remaining amounts due. On September 18, 2026, the landlord exercised its right under the amendment to accelerate the expiration of the lease term and specified an accelerated expiration date of October 4, 2026.

Previous wording

On June 22, 2026, Boundless Bio entered into an Agreement and Plan of Merger (the Merger Agreement) with Serapha Bio, Inc. (Serapha), a privately held biotechnology company advancing SERP-01, an investigational in vivo base editing therapy for Alpha-1 Antitrypsin Deficiency (AATD), and Boulder Merger Sub Corp., a wholly owned subsidiary of Boundless Bio (Merger Sub). Pursuant to the Merger Agreement, among other matters and subject to the satisfaction or waiver of the conditions set forth therein, Merger Sub will merge with and into Serapha, with Serapha continuing as a wholly owned subsidiary of Boundless Bio and the surviving corporation of the merger (the Merger). The Merger is intended to qualify for federal income tax purposes as (1) a tax-free reorganization under the provisions of Section 368(a) of the Internal Revenue Code of 1986, as amended (the Code), and/or (2) an exchange of shares of Serapha capital stock for Boundless Bio common stock under Section 351(a) of the Code.

Current wording

On June 22, 2026, Boundless Bio entered into an Agreement and Plan of Merger and Reorganization (as amended, the Merger Agreement) with Serapha Bio, Inc. (Serapha), a privately held biotechnology company advancing SERP-01, an investigational in vivo base editing therapy for Alpha-1 Antitrypsin Deficiency (AATD), and Boulder Merger Sub Corp., a wholly owned subsidiary of Boundless Bio (Merger Sub). The Merger Agreement was amended on August 28, 2026. Pursuant to the Merger Agreement, among other matters and subject to the satisfaction or waiver of the conditions set forth therein, Merger Sub will merge with and into Serapha, with Serapha continuing as a wholly owned subsidiary of Boundless Bio and the surviving corporation of the merger (the Merger). The Merger is intended to qualify for federal income tax purposes as (1) a “reorganization” within the meaning of Section 368(a) of the Internal Revenue Code of 1986, as amended (the Code), and/or (2) an exchange of shares of Serapha capital stock for Boundless Bio common stock under Section 351(a) of the Code.

Previous wording

Upon closing, Serapha's existing stockholders are expected to own approximately 96.31% of the combined company, and Boundless Bio's existing stockholders are expected to own approximately 3.69%, in each case on a fully diluted basis. Prior to closing, Boundless Bio may declare a special cash dividend to its current stockholders to the extent its net cash is estimated, based on a reasonable, good faith approximation, to exceed zero at closing (as further discussed below).

Current wording

Upon closing, Serapha's existing stockholders are expected to own approximately 96.2% of the combined company, and Boundless Bio's existing stockholders are expected to own approximately 3.8%, in each case on a fully diluted basis. Prior to closing, Boundless Bio expects to declare a special cash dividend to its current stockholders to the extent its net cash is estimated, based on a reasonable, good faith approximation, to exceed zero at closing (as further discussed below).

Previous wording

The transaction requires approval from stockholders of both companies, as well as continued Nasdaq listing of Boundless Bio’s common stock, effectiveness of a Form S-4 registration statement, the receipt of at least $200 million in gross proceeds from related financings by Serapha (as described below), among other closing conditions. In connection with the Merger, Boundless Bio stockholders will also be asked to approve a reverse stock split and an increase in authorized shares. Either party may terminate the agreement under certain circumstances, in which case a termination fee of $1.0 million may be payable by the terminating party.

Current wording

The transaction requires approval from stockholders of both companies, as well as continued Nasdaq listing of Boundless Bio’s common stock, effectiveness of a Form S-4 registration statement (which was declared effective on November 3, 2026), and the receipt of at least $200 million in gross proceeds from related financings by Serapha (as described below), among other closing conditions. In connection with the Merger, Boundless Bio stockholders will also be asked to approve a reverse stock split and an increase in authorized shares. Either party may terminate the agreement under certain circumstances, in which case a termination fee of $1.0 million may be payable by the terminating party.

Previous wording

In connection with the signing of the Merger Agreement, on June 23, 2026, we announced a reduction in workforce of approximately 75%. We recognized a charge of approximately $2.8 million during the three and six months ended June 30, 2026 and estimate aggregate one-time charges of approximately $3.0 million to $5.0 million, with the remainder to be recognized in the second half of 2026. See Note 1 to our unaudited condensed financial statements included elsewhere in this Quarterly Report on Form 10-Q for further information.

Current wording

In connection with the signing of the Merger Agreement, on June 23, 2026, we announced a reduction in workforce of approximately 75%. We recognized charges of approximately $0.9 million and $3.6 million during the three and nine months ended September 30, 2026, respectively, and expect to recognize approximately $0.4 million of additional one-time termination benefits in the fourth quarter of 2026 as the related services are rendered. In addition, approximately $3.8 million of change-in-control severance and bonuses will become payable only upon consummation of the Merger. See Note 1 to our unaudited condensed financial statements included elsewhere in this Quarterly Report on Form 10-Q for further information.

Previous wording

The transaction is expected to close in the fourth quarter of 2026, subject to the satisfaction of certain closing conditions, along with the concurrent Serapha Pre-Closing Financing (as defined below). Following completion of the Merger, the combined company plans to focus on advancing SERP-01 and does not intend to continue development of any of Boundless Bio’s legacy ecDTx. Boundless Bio may continue to evaluate opportunities for its ecDTx, which may include a sale, license, transfer, disposition, divestiture or other monetization transaction to a third party or to a related party so long as the transaction would not result in material post-closing obligations to the combined company without Serapha’s consent. If the Merger is not completed, Boundless Bio may continue to explore development opportunities for its ecDTx and pursue other strategic alternatives, including collaborations, financing opportunities or a transaction similar to the proposed Merger, or liquidation.

Current wording

The Merger is expected to close in the fourth quarter of 2026, subject to the satisfaction of certain closing conditions, along with the concurrent Serapha Pre-Closing Financing (as defined below). Following completion of the Merger, the combined company is expected to be renamed Serapha Bio, Inc., and its common stock is expected to trade on Nasdaq under the symbol “AATD.” The combined company plans to focus on advancing SERP-01 and does not intend to continue development of any of Boundless Bio’s legacy ecDTx. Prior to the closing, Boundless Bio may continue to evaluate opportunities for its ecDTx, which may include a sale, license, transfer, disposition, divestiture or other monetization transaction to a third party or to a related party, so long as the transaction would not result in material post-closing obligations to the combined company without Serapha’s consent. If the Merger is not completed, Boundless Bio may continue to explore development opportunities for its ecDTx and pursue other strategic alternatives, including collaborations, financing opportunities or a transaction similar to the proposed Merger, or liquidation.

Previous wording

Further, prior to the closing of the Merger (the Closing), Boundless Bio expects to declare and set aside the aggregate cash amount to be paid in accordance with a special cash dividend (the Pre-Closing Dividend) to holders of record of outstanding shares of its common stock as of a record date prior to the effective time of the Merger, to be determined by its board of directors. The ex‑dividend date in respect of the Pre-Closing Dividend will be determined by Nasdaq. Boundless Bio’s stockholders of record prior to the ex‑dividend date will be entitled to receive the Pre-Closing Dividend, regardless of whether they beneficially own such shares as of the dividend date. The amount of the Pre-Closing Dividend is expected to be approximately $44 to $48 million in the aggregate.

Current wording

Further, prior to the closing of the Merger (the Closing), Boundless Bio expects to declare and set aside the aggregate cash amount to be paid in accordance with a special cash dividend (the Pre-Closing Dividend) to holders of record of outstanding shares of its common stock as of a record date to be set by its board of directors as close as reasonably practicable to, but not later than, the anticipated Closing. The ex‑dividend date in respect of the Pre-Closing Dividend will be determined by Nasdaq. Boundless Bio stockholders of record who continue to hold their eligible shares until market open on the ex‑dividend date will be entitled to payment of the Pre-Closing Dividend. The Pre-Closing Dividend will be equal in the aggregate to Boundless Bio’s reasonable, good faith approximation of the amount by which its net cash, as determined under the Merger Agreement, is expected to exceed $0 as of the Closing, and is currently expected to be approximately $44 to $48 million, subject to adjustment based on Boundless Bio’s net cash at closing and the terms of the Merger Agreement.

Previous wording

Although, to date, our business has not been materially impacted, the ultimate impact of global economic and market conditions and changes in government agencies, regulations and policies remains highly uncertain and will depend on future developments and factors that continue to evolve. We closely monitor these ongoing developments and the potential impact of these factors on our business, operating expenses, and cash position and, if circumstances warrant, we may make adjustments to our operating plan. For more information regarding these risks and uncertainties, see Item 1A, “Risk Factors,” in Part I of our 2025 10-K.

Current wording

Although, to date, our business has not been materially impacted, the ultimate impact of global economic and market conditions and changes in government agencies, regulations, and policies remains highly uncertain and will depend on future developments and factors that continue to evolve. We closely monitor these ongoing developments and the potential impact of these factors on our business, operating expenses, and cash position and, if circumstances warrant, we may make adjustments to our operating plan. For more information regarding these risks and uncertainties, see Item 1A, “Risk Factors,” in Part II of our Q2 2026 10-Q and Item 1A, “Risk Factors,” in Part I of our 2025 10-K.

Previous wording

Our research and development (R&D) expenses have related primarily to building our Spyglass platform, our ecDTx discovery efforts, our preclinical and clinical development activities, and the development of a diagnostic test. R&D expenses are recognized as incurred, and payments made prior to the receipt of goods or services to be used in R&D are capitalized until the goods or services are received. We use internal resources primarily to conduct our research and discovery activities, as well as for managing our preclinical development, process development, manufacturing, and clinical development activities. We track direct costs on a development program specific basis. Indirect costs are not included in program costs, as these costs are general in nature and benefit all our discovery efforts and development programs.

Current wording

Our research and development (R&D) expenses have related primarily to building our Spyglass platform, our ecDTx discovery efforts, our preclinical and clinical development activities, and the development of a diagnostic test. R&D expenses are recognized as incurred, and payments made prior to the receipt of goods or services to be used in R&D are capitalized until the goods or services are received. We have used internal resources primarily to conduct our research and discovery activities, as well as for managing our preclinical development, process development, manufacturing, and clinical development activities. We tracked direct costs on a development program specific basis. Indirect costs are not included in program costs, as these costs are general in nature and benefit all our discovery efforts and development programs.

Previous wording

The successful development of our ecDTx is highly uncertain. There are numerous factors associated with the successful development of our ecDTx, including future trial design and various regulatory requirements, many of which cannot be determined with accuracy at this time based on our stage of development. In addition, future regulatory factors beyond our control may impact our clinical development programs. Product candidates in later stages of development generally have higher development costs than those in earlier stages of development.

Current wording

The successful development of our ecDTx is highly uncertain. There are numerous factors associated with the successful development of our ecDTx, including future trial design and various regulatory requirements, many of which cannot be determined with accuracy. In addition, future regulatory factors beyond our control may impact our clinical development programs. Product candidates in later stages of development generally have higher development costs than those in earlier stages of development.

Previous wording

Other income, net was $1.6 million and $3.0 million for the six months ended June 30, 2026 and 2025, respectively. The $1.4 million decrease resulted from a reduction in interest income generated by our available-for-sale investment securities portfolio due to a decrease in the amount of cash and cash equivalents available for investing purposes as well as a decline in the market yields available for such investment securities compared to the prior year period.

Current wording

Other income, net was $0.8 million and $1.3 million for the three months ended September 30, 2026 and 2025, respectively. The $0.4 million decrease primarily resulted from a $0.7 million reduction in interest income generated by our available-for-sale investment securities portfolio due to a decrease in the amount of cash and cash equivalents available for investing purposes as well as a decline in the market yields available for such investment securities compared to the prior year period, partially offset by a $0.3 million gain on the disposal of property and equipment.

Previous wording

R&D expenses were $23.7 million and $24.4 million for the six months ended June 30, 2026 and 2025, respectively. The $0.6 million decrease was primarily attributable to (i) a $2.0 million decrease in direct program costs, (ii) a $1.9 million decrease in personnel-related costs, reflecting a decline in ongoing compensation costs resulting from the reduction in workforce, partially offset by severance costs recognized during the second quarter of 2026, and (iii) a $0.8 million decrease in other R&D costs, partially offset by (iv) a $3.0 million increase in facilities-related costs due to the early termination of the 2024 Lease, and (v) a $1.1 million increase related to the impairment of property and equipment as a result of our early termination of the 2024 Lease. The increase in BBI-940 direct program costs for the six months ended June 30, 2026 compared with the same period in 2025 was primarily due to costs relating to the KOMODO-1 clinical trial initiated in early 2026, and the decreases in BBI-355 and BBI-825 direct program costs for the six months ended June 30, 2026 compared with the same period in 2025 were primarily due to our decisions to wind down the POTENTIATE and STARMAP clinical trials, as discussed above.

Current wording

R&D expenses were $25.1 million and $35.0 million for the nine months ended September 30, 2026 and 2025, respectively. The $9.9 million decrease was primarily attributable to (i) a $6.6 million decrease in direct program costs, (ii) a $3.7 million decrease in personnel-related costs, reflecting a decline in ongoing compensation costs resulting from the reduction in workforce, partially offset by severance costs recognized during the second quarter of 2026, and (iii) a $1.7 million decrease in other R&D costs, partially offset by (iv) a $1.0 million increase in facilities-related costs due to the early termination of the 2024 Lease, and (v) a $1.1 million increase related to the impairment of property and equipment as a result of our early termination of the 2024 Lease. The increase in BBI-940 direct program costs for the nine months ended September 30, 2026 compared with the same period in 2025 was primarily due to costs relating to the KOMODO-1 clinical trial initiated in early 2026, and the decreases in BBI-355 and BBI-825 direct program costs for the nine months ended September 30, 2026 compared with the same period in 2025 were primarily due to our decisions to wind down the POTENTIATE and STARMAP clinical trials, as discussed above.

Previous wording

G&A expenses were $10.4 million and $4.8 million for the three months ended June 30, 2026 and 2025, respectively. The $5.6 million increase in G&A expenses was primarily attributable to (i) a $1.7 million increase in personnel-related costs, primarily related to severance costs and stock-based compensation recognized in connection with the amendment of our stock options (see Notes 1 and 9 to our condensed financial statements), (ii) a $2.0 million increase in facilities-related costs due to the early termination of the 2024 Lease, (iii) a $1.4 million increase in professional fees, primarily related to legal fees incurred in connection with the Merger, and (iv) a $0.5 million increase in other G&A costs.

Current wording

G&A expenses were $19.9 million and $14.5 million for the nine months ended September 30, 2026 and 2025, respectively. The $5.4 million increase in G&A expenses was primarily attributable to (i) a $2.7 million increase in professional fees, primarily related to transaction costs incurred in connection with the Merger, (ii) a $2.3 million increase in facilities-related costs due to the early termination of the 2024 Lease, (iii) a $0.3 million increase in personnel-related costs, primarily related to severance costs and stock-based compensation recognized in connection with the amendment of our stock options (see Notes 1 and 10 to our condensed financial statements), partially offset by a decline in ongoing compensation costs resulting from the reduction in workforce, and (iv) a $0.1 million increase in other G&A costs, including the impairment of property and equipment as a result of our early termination of the 2024 Lease.

Previous wording

Other income, net was $0.7 million and $1.4 million for the three months ended June 30, 2026 and 2025, respectively. The $0.7 million decrease resulted from a reduction in interest income generated by our available-for-sale investment securities portfolio due to a decrease in the amount of cash and cash equivalents available for investing purposes as well as a decline in the market yields available for such investment securities compared to the prior year period.

Current wording

Other income (expense), net was $2.4 million and $4.2 million for the nine months ended September 30, 2026 and 2025, respectively. The $1.8 million decrease primarily resulted from a reduction in interest income generated by our available-for-sale investment securities portfolio due to a decrease in the amount of cash and cash equivalents available for investing purposes as well as a decline in the market yields available for such investment securities compared to the prior year period.

Previous wording

On June 22, 2026, Boundless Bio entered into the Merger Agreement pursuant to which, among other matters, Merger Sub will merge with and into Serapha, with Serapha surviving as a wholly owned subsidiary of the Company. The Closing is subject to approval by its stockholders and the stockholders of Serapha and other closing conditions. Boundless Bio’s future operations are highly dependent on the success of the proposed Merger with Serapha.

Current wording

On June 22, 2026, Boundless Bio entered into the Merger Agreement, pursuant to which, among other matters, Merger Sub will merge with and into Serapha, with Serapha surviving as a wholly owned subsidiary of Boundless Bio. The Closing is subject to approval by the stockholders of Boundless Bio and Serapha and other closing conditions. Boundless Bio’s future operations are highly dependent on the success of the proposed Merger with Serapha.

Previous wording

Through June 30, 2026, we have raised a total of $353.9 million to fund our operations primarily from the gross proceeds from the sale and issuance of shares of our convertible preferred stock prior to our IPO and the sale and issuance of 6,250,000 shares of our common stock in our IPO, which closed in April 2024. Our IPO generated gross proceeds of $100.0 million, which resulted in net proceeds to us of approximately $87.7 million, after deducting underwriting discounts and commissions and other offering expenses.

Current wording

Through September 30, 2026, we have raised a total of $354.7 million to fund our operations primarily from the gross proceeds from the sale and issuance of shares of our convertible preferred stock prior to our IPO and the sale and issuance of 6,250,000 shares of our common stock in our IPO, which closed in April 2024. Our IPO generated gross proceeds of $100.0 million, which resulted in net proceeds to us of approximately $87.7 million, after deducting underwriting discounts and commissions and other offering expenses.

Previous wording

In April 2025, we entered into an Open Market Sale Agreement SM (the Sales Agreement) with Jefferies LLC (the Agent), pursuant to which we may, from time to time, sell shares of our common stock in “at-the-market” offerings through or to the Agent, acting as sales agent or principal. See Note 1 to our unaudited condensed financial statements included elsewhere in this Quarterly Report on Form 10-Q under the section entitled “ATM Offering” for further information. We are not obligated to sell any shares under the Sales Agreement, and the Agent is not obligated to buy or sell any shares of our common stock. We cannot provide any assurance that we will sell any shares under the Sales Agreement, or, if we do, as to the prices, amounts, or timing of any such sales. As of June 30, 2026, no shares had been sold under the Sales Agreement.

Current wording

In April 2025, we entered into an Open Market Sale Agreement SM (the Sales Agreement) with Jefferies LLC (the Agent), pursuant to which we may, from time to time, sell shares of our common stock in “at-the-market” offerings through or to the Agent, acting as sales agent or principal. See Note 1 to our unaudited condensed financial statements included elsewhere in this Quarterly Report on Form 10-Q under the section entitled “ATM Offering” for further information. We are not obligated to sell any shares under the Sales Agreement, and the Agent is not obligated to buy or sell any shares of our common stock. We cannot provide any assurance that we will sell any shares under the Sales Agreement, or, if we do, as to the prices, amounts, or timing of any such sales. As of September 30, 2026, no shares had been sold under the Sales Agreement. While the Merger is pending, the Merger Agreement prohibits us from issuing shares of our capital stock, including under the Sales Agreement, without Serapha’s consent (except for Company shares issued upon valid exercise of outstanding Company options).

Previous wording

As of June 30, 2026, we had cash, cash equivalents, and short-term investments of $72.6 million. In April 2026, we terminated the 2024 Lease, and entered into a new, shorter-term lease, the term of which commenced June 1, 2026. The lease termination involved a cash payment of $10.0 million by us to the landlord, and the landlord’s retention of our security deposit of approximately $0.5 million. See Note 7 to our unaudited condensed financial statements included elsewhere in this Quarterly Report on Form 10-Q for further information regarding the lease termination and new lease. Based on our current operating plan, and without giving effect to the anticipated pre-closing cash dividend of approximately $44 to $48 million or the proposed Merger with Serapha described in Note 1 to our unaudited condensed financial statements, we believe that our existing cash, cash equivalents, and short-term investments will be sufficient to fund our operations through the anticipated closing date of the Merger and for a period of at least 12 months from the date hereof. However, our operating plan may change, whether or not the Merger is completed. We have based this estimate on assumptions that may prove to be wrong, and we could deplete our capital resources sooner than we expect. Additionally, the process of conducting preclinical studies, manufacturing any ecDTx or other product candidates, and testing ecDTx or other product candidates in clinical trials is costly, and the timing of progress and expenses in these studies and trials is uncertain.

Current wording

As of September 30, 2026, we had cash, cash equivalents, and short-term investments of $62.9 million. We have no remaining obligations under the 2024 Lease, which we terminated effective May 31, 2026, or the 2026 Lease, which expired on October 4, 2026 after the landlord exercised its right to accelerate the expiration of the lease term. See Note 7 to our unaudited condensed financial statements included elsewhere in this Quarterly Report on Form 10-Q for further information. In connection with the Merger, we expect our principal uses of cash to be the payment of the Pre-Closing Dividend, the remaining costs of completing the Merger, the remaining one-time termination benefits associated with our reduction in workforce, and the costs of winding down our operations. These include approximately $0.9 million of transaction costs that we expect to incur in the fourth quarter of 2026, approximately $0.4 million of additional one-time termination benefits, and approximately $5.9 million of change-in-control severance, bonuses, and transaction costs that will be payable only if the Merger is consummated. Based on our current operating plan, and without giving effect to the anticipated Pre-Closing Dividend of approximately $44 to $48 million or the proposed Merger with Serapha described in Note 1 to our unaudited condensed financial statements, we believe that our existing cash, cash equivalents, and short-term investments will be sufficient to fund our operations through the anticipated closing date of the Merger and for a period of at least 12 months from the date hereof. However, our operating plan may change, whether or not the Merger is completed. We have based this estimate on assumptions that may prove to be wrong, and we could deplete our capital resources sooner than we expect. Additionally, the process of conducting preclinical studies, manufacturing any ecDTx or other product candidates, and testing ecDTx or other product candidates in clinical trials is costly, and the timing of progress and expenses in these studies and trials is uncertain.

Previous wording

Our primary uses of capital were historically compensation and related expenses, research and development costs to support our ecDTx pipeline, legal and other regulatory expenses and general overhead costs. Now that we have suspended and are winding down our research and development activities in anticipation of the Merger with Serapha, our operations will be limited and we expect that Boundless Bio expenses other than those related to the Merger will decrease significantly.

Current wording

Our primary uses of capital were historically compensation and related expenses, research and development costs to support our ecDTx pipeline, legal and other regulatory expenses and general overhead costs. Now that we have suspended and are winding down our research and development activities in anticipation of the Merger with Serapha, our operations will be limited, and we expect that our expenses other than those related to the Merger will decrease significantly.

Previous wording

We have incurred significant operating losses since our inception and, as of June 30, 2026, we had an accumulated deficit of $296.9 million. We expect to continue to incur losses for the foreseeable future, and, in general, we anticipate these losses will increase substantially in the future if we decide to develop, seek regulatory approval for, and potentially commercialize any ecDTx, conduct clinical trials and preclinical studies, utilize third parties to manufacture any ecDTx and related raw materials, leverage Spyglass to potentially identify additional development opportunities for our ecDTx and expand our therapeutic pipeline, seek to expand and protect our intellectual property, as well as incur additional costs associated with being a public company. If we obtain regulatory approval for our ecDTx, we expect to incur significant commercialization expenses related to product sales, marketing, manufacturing, and distribution. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending on the timing of our clinical trials, preclinical studies, and our other research and development activities and capital expenditures.

Current wording

We have incurred significant operating losses since our inception and, as of September 30, 2026, we had an accumulated deficit of $302.3 million. We expect to continue to incur losses for the foreseeable future, and, in general, we anticipate these losses will increase substantially in the future if we decide to develop, seek regulatory approval for, and potentially commercialize any ecDTx, conduct clinical trials and preclinical studies, utilize third parties to manufacture any ecDTx and related raw materials, leverage Spyglass to potentially identify additional development opportunities for our ecDTx and expand our therapeutic pipeline, seek to expand and protect our intellectual property, as well as incur additional costs associated with being a public company. If we obtain regulatory approval for our ecDTx, we expect to incur significant commercialization expenses related to product sales, marketing, manufacturing, and distribution. Our net losses may fluctuate significantly from quarter-to-quarter and year-to-year, depending on the timing of our clinical trials, preclinical studies, and our other research and development activities and capital expenditures.

Previous wording

We have no committed sources of capital. Until we can generate sufficient product revenue to finance our cash requirements, if ever, we expect to finance our future cash needs primarily through equity offerings (including through the Sales Agreement), debt financings, or other capital sources, including potential collaborations, licenses, and other similar arrangements. However, we may be unable to raise additional funds or enter such other arrangements when needed on favorable terms or at all. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders will be, or could be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our common stockholders. Debt financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures, or declaring dividends. If we raise additional funds through other collaborations or licensing arrangements with third parties, we may have to relinquish valuable rights to our future revenue streams, ecDTx, research programs, intellectual property, or proprietary technology, or grant licenses on terms that may not be favorable to us. Our ability to raise additional funds may be adversely impacted by global economic conditions, disruptions to, and volatility in, the credit and financial markets in the United States, inflation, diminished liquidity and credit availability, declines in consumer confidence, declines in economic growth, increases in unemployment rates, and uncertainty about economic stability. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed, we may be required to delay, limit, reduce, or terminate our ecDTx development or other operations, or grant rights to develop and market ecDTx to third parties that we would otherwise prefer to develop and market ourselves, or on less favorable terms than we would otherwise choose.

Current wording

We have no committed sources of capital. Until we can generate sufficient product revenue to finance our cash requirements, if ever, we expect to finance our future cash needs primarily through equity offerings (including, if the Merger is not completed, through the Sales Agreement), debt financings, or other capital sources, including potential collaborations, licenses, and other similar arrangements. However, we may be unable to raise additional funds or enter such other arrangements when needed on favorable terms or at all. To the extent that we raise additional capital through the sale of equity or convertible debt securities, the ownership interest of our stockholders will be, or could be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our common stockholders. Debt financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures, or declaring dividends. If we raise additional funds through other collaborations or licensing arrangements with third parties, we may have to relinquish valuable rights to our future revenue streams, ecDTx, research programs, intellectual property, or proprietary technology, or grant licenses on terms that may not be favorable to us. Our ability to raise additional funds may be adversely impacted by global economic conditions, disruptions to, and volatility in, the credit and financial markets in the United States, inflation, diminished liquidity and credit availability, declines in consumer confidence, declines in economic growth, increases in unemployment rates, and uncertainty about economic stability. If we are unable to raise additional funds through equity or debt financings or other arrangements when needed, we may be required to delay, limit, reduce, or terminate our ecDTx development or other operations, or grant rights to develop and market ecDTx to third parties that we would otherwise prefer to develop and market ourselves, or on less favorable terms than we would otherwise choose.

Previous wording

Net cash used in operating activities was $35.9 million and $26.4 million for the six months ended June 30, 2026 and 2025, respectively. The net cash used in operating activities during the six months ended June 30, 2026 was primarily driven by our reported net loss of $37.2 million, net of noncash charges (including stock-based compensation expense, depreciation, impairment of property and equipment, and right-of-use asset amortization) totaling $14.3 million and a $13.0 million increase of our net operating assets. The net cash used in operating activities during the six months ended June 30, 2025 was primarily driven by our reported net loss of $31.4 million, net of noncash charges (including stock-based compensation expense, depreciation, and right-of-use asset amortization) totaling $4.3 million and a $0.8 million decrease of our net operating assets. The increase in cash used in operations during the six months ended June 30, 2026 in comparison to the six months ended June 30, 2025 was primarily attributable to the $10.0 million cash payment associated with the termination of the 2024 Lease, partially offset by a decrease in third-party spending associated with our discovery, development, and clinical activities.

Current wording

Net cash used in operating activities was $46.8 million and $36.6 million for the nine months ended September 30, 2026 and 2025, respectively. The net cash used in operating activities during the nine months ended September 30, 2026 was primarily driven by our reported net loss of $42.6 million, net of noncash charges (including stock-based compensation expense, depreciation, impairment of property and equipment, and right-of-use asset amortization) totaling $14.4 million and an $18.6 million increase of our net operating assets. The net cash used in operating activities during the nine months ended September 30, 2025 was primarily due to our reported net loss of $45.3 million, net of noncash charges (including stock-based compensation expense, depreciation, and right-of-use asset amortization) totaling $6.1 million and a $2.6 million decrease of our net operating assets. The increase in cash used in operations during the nine months ended September 30, 2026 in comparison to the nine months ended September 30, 2025 was primarily attributable to the $10.0 million cash payment associated with the termination of the 2024 Lease, partially offset by a decrease in third-party spending associated with our discovery, development, and clinical activities.

Previous wording

Investing activities consist primarily of purchases and maturities of investment securities and purchases of property and equipment. Such activities resulted in a net cash inflow of approximately $37.7 million and $14.4 million during the six months ended June 30, 2026 and 2025, respectively, in each case, primarily from the net maturities of our available-for-sale securities portfolio.

Current wording

Investing activities consist primarily of purchases and maturities of investment securities and purchases of property and equipment. Such activities resulted in a net cash inflow of approximately $62.4 million and $24.8 million during the nine months ended September 30, 2026 and 2025, respectively, in each case, primarily from the net maturities of our available-for-sale securities portfolio.

Previous wording

Financing activities during the six months ended June 30, 2026 consisted of less than $0.1 million in proceeds from the sale of common stock under the ESPP and less than $0.1 million in proceeds from the exercise of stock options. Financing activities during the six months ended June 30, 2025 consisted of $0.1 million in proceeds from the sale of common stock under the ESPP.

Current wording

Financing activities during the nine months ended September 30, 2026 consisted of $0.8 million in proceeds from the exercise of stock options and less than $0.1 million in proceeds from the sale of common stock under the ESPP. Net cash provided by financing activities was $0.1 million during the nine months ended September 30, 2025, representing net proceeds from the sale of shares of our common stock under our ESPP.

Previous wording

On April 17, 2026, we entered into a new, shorter-term facility lease for approximately 10,822 square feet of laboratory and office space in La Jolla, California, with an initial term of 12 months commencing June 1, 2026. Monthly base rent payments are approximately $56,000, with two months of base rent abatement during the second and third full calendar months of the lease term. As of June 30, 2026, our remaining obligations under this lease were approximately $0.5 million.

Current wording

On April 17, 2026, we entered into a new, shorter-term facility lease for approximately 10,822 square feet of laboratory and office space in La Jolla, California, with an initial term of 12 months commencing June 1, 2026. Monthly base rent payments were approximately $56,000, with two months of base rent abatement during the second and third full calendar months of the lease term. On August 26, 2026, we amended this lease and paid the landlord total consideration of approximately $0.8 million, including our security deposit of approximately $77,000, which the landlord retained, in full satisfaction of all remaining base rent, our share of direct expenses, restoration costs, and all other amounts payable through the end of the lease term. On September 18, 2026, the landlord exercised its right under the amendment to accelerate the expiration of the lease term, specifying an accelerated expiration date of October 4, 2026. As of September 30, 2026, we had no remaining obligations under this lease, and the lease expired on October 4, 2026.