Boundless Bio Inc

Item 1A. Risk Factors.

Investing in our common stock involves a high degree of risk. You should carefully consider the risks and uncertainties described in Part I, Item 1A,Risk Factors, of our 2025 10-K, together with all of the information in this Quarterly Report be, including the risk factors set forth below, before making an investment decision to purchase or sell shares of our common stock. If any of those risks are realized, our business, financial condition, results of operations, and prospects could be materially and adversely affected. In that event, the trading price of our common stock could decline, and you could lose all or part of your investment. TheExcept as set forth below, there have been no material changes to the risk factors set forth in Part I, Item 1A of our 2025 10-K.

Risks Related to the Proposed Merger

Failure to complete, or delays in completing, the potential Merger with Serapha could materially and adversely affect Boundless Bios results of operations, business, financial results and/or common stock price.

On June 22, 2026, Boundless Bio entered into the Merger Agreement with Serapha pursuant to which, among other matters, and subject to the satisfaction or waiver of the conditions set forth in the Merger Agreement, 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. Boundless Bio following the Merger is referred to herein as the Combined Company. Completion of the Merger is subject to certain closing conditions, a number of which are not within Boundless Bios control. Any failure to satisfy these required conditions to closing may prevent, delay or otherwise materially adversely affect the completion of the transaction. Boundless Bio cannot predict with certainty whether or when any of the required closing conditions will be satisfied or if another uncertainty may arise and cannot assure you that it will be able to successfully complete the Merger as currently contemplated under the Merger Agreement or at all.

Boundless Bios efforts to complete the Merger could cause substantial disruptions in, and create uncertainty surrounding, its business, which may materially adversely affect its results of operation and its business. Uncertainty as to whether the Merger will be completed in a timely manner or at all may affect Boundless Bios ability to retain and motivate existing employees or could adversely affect Boundless Bios business and its relationship with consultants, suppliers, vendors, regulators and other business partners. The adverse effects of the pendency of the transaction could be exacerbated by any delays in completion of the transaction or termination of the Merger Agreement.

If the conditions to the Merger are not satisfied or waived, the Merger may not occur.

Even if the Merger is approved by the stockholders of Serapha and Boundless Bio, specified conditions must be satisfied or, to the extent permitted by applicable law, waived to complete the Merger. These conditions are set forth in the Merger Agreement. Boundless Bio cannot assure you that all of the conditions to the completion of the Merger will be satisfied or waived. If the conditions are not satisfied or waived, the Merger may not occur or the closing may be delayed.

Boundless Bio and Serapha may mutually agree to waive the Nasdaq listing condition under the Merger Agreement, and if such condition is waived, the Combined Companys stock may not be listed on Nasdaq following completion of the Merger.

Pursuant to the Merger Agreement, Boundless Bio agreed to use commercially reasonable efforts to maintain the listing of Boundless Bios common stock (Boundless Bio Common Stock) on Nasdaq until the Effective Time and, to the extent required by the rules and regulations of Nasdaq, to cause the shares of Boundless Bio Common Stock to be issued in connection with the Contemplated Transactions (as defined in the Merger Agreement) to be approved for listing on Nasdaq. The Merger Agreement also requires the parties, to the extent required by Nasdaq Marketplace Rule 5110, to use commercially reasonable efforts to cause the initial listing application for the Boundless Bio Common Stock and Boundless Bio preferred stock (together, the Boundless Bio Capital Stock) on Nasdaq (including any Boundless Bio Common Stock issuable upon conversion thereof) (the Nasdaq Listing Application) to be conditionally approved prior to the Effective Time (as defined in the Merger Agreement). Additionally, under the Merger Agreement, each of Boundless Bios and Seraphas obligation to complete the Merger is subject to the satisfaction or waiver 

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by each of the parties of various conditions, including that the Nasdaq Listing Application has been approved by Nasdaq. In the event that the Nasdaq Listing Application is not approved by Nasdaq, it is possible (although not likely) that Boundless Bio and Serapha may mutually agree to waive the applicable condition and nonetheless proceed with completing the Merger. If such condition is waived, Boundless Bio will not recirculate an updated proxy statement/prospectus to the one that will be provided in connection with matters related to the Merger, nor will it solicit a new vote of stockholders prior to proceeding with the Merger. If Boundless Bio proceeds with the Merger in these circumstances, the Combined Companys stock may not be listed on Nasdaq.

If the Combined Companys stock is not listed on Nasdaq following completion of the Merger, trading of the shares could be conducted in the overthecounter market or on an electronic bulletin board established for unlisted securities such as the Pink Sheets or the OTC Bulletin Board. In such event, it is likely that there would be significantly less liquidity in the trading of the Combined Company common stock, decreases in institutional and other investor demand for the shares, a reduction in coverage by securities analysts, a decrease in market making activity and information available concerning trading prices and volume, and fewer broker dealers willing to execute trades in the Combined Company common stock. Also, it may be difficult for the Combined Company to raise additional capital if the Combined Company common stock is not listed on a major exchange. The occurrence of any of these events could result in a further decline in the market price of the Combined Company common stock and could have a material adverse effect on the Combined Company.

The Exchange Ratio for the Merger will not change or otherwise be adjusted based on the market price of Boundless Bio Common Stock.

Each then-outstanding share of Serapha common stock (Serapha Common Stock) and Serapha preferred stock (together, Serapha Capital Stock) (including shares of Serapha Common Stock issued in the Serapha Pre-Closing Financing), excluding any shares to be cancelled pursuant to the Merger Agreement, will be converted into the right to receive a number of shares of Boundless Bio Common Stock, equal to the Exchange Ratio (as defined in the Merger Agreement), (ii) each then-outstanding Serapha Option will be converted into and become an Assumed Option (as defined in the Merger Agreement) on the existing terms and conditions (including with respect to vesting and accelerated vesting), subject to adjustment as set forth in the Merger Agreement, and (iii) each then-outstanding Serapha warrant, including any Serapha pre-funded warrant issued pursuant to the Serapha Pre-Closing Financing, will be converted into an Assumed Warrant (as defined in the Merger Agreement), subject to adjustment as set forth in the Merger Agreement and the form of warrant. Applying the Exchange Ratio, the former Serapha securityholders immediately before the Merger are expected to own approximately 96.31% of the aggregate number of shares of the Combined Companys capital stock following the Merger (on a fullydiluted basis, and subject to dilution from any equity issued by Serapha after June 22, 2026 and before the closing), and Boundless Bio securityholders immediately before the Merger are expected to own approximately 3.69% of the aggregate number of shares of the Combined Company capital stock following the Merger (on a fullydiluted basis), subject to certain assumptions, including, but not limited to, that Boundless Bio Net Cash (as defined in the Merger Agreement) as of Closing will be approximately $0, after giving effect to the Pre-Closing Dividend, which is expected to be approximately $44 to $48 million.

Any changes in the market price of Boundless Bio Common Stock before the completion of the Merger will not affect the number of shares Serapha stockholders will be entitled to receive pursuant to the Merger Agreement. However, the Exchange Ratio remains subject to equitable adjustment as set forth in the Merger Agreement for certain changes in the capitalization of Boundless Bio or Serapha, including any stock dividend, subdivision, reclassification, recapitalization, stock split, including the Nasdaq Reverse Split (as defined in the Merger Agreement) to the extent not previously taken into account in calculating the Exchange Ratio, combination or exchange of shares or other similar change. Therefore, if before the completion of the Merger, the market price of Boundless Bio Common Stock increases from the market price on the date of the Merger Agreement, then Serapha stockholders could receive merger consideration with substantially more value for their shares of Serapha Capital Stock than the parties had negotiated when they established the Exchange Ratio. Similarly, if before the completion of the Merger, the market price of Boundless Bio Common Stock declines from the market price on the date of the Merger Agreement, then Serapha stockholders could receive merger consideration with substantially lower value. The Merger Agreement does not include a pricebased termination right.

The issuance of Boundless Bio Common Stock, including the shares of Boundless Bio Common Stock issued in exchange for shares of Serapha Common Stock issued in the Serapha PreClosing Financing, to Serapha stockholders pursuant to the Merger Agreement and the resulting change in control from the Merger, and the Nasdaq Reverse Split, must be approved by Boundless Bio stockholders, and the Merger Agreement and transactions contemplated thereby must be approved by the Serapha stockholders. Failure to obtain these approvals would prevent the closing of the Merger.

Before the Merger can be completed, Boundless Bio stockholders must approve, among other things, the Boundless Bio Stockholder Matters (as defined in the definition of Parent Stockholder Matters in the Merger Agreement), including the issuance of shares of Boundless Bio Common Stock representing (or convertible into) more than 20% of the shares of Boundless Bio Common Stock outstanding immediately prior to the Effective Time to Serapha stockholders in connection with the Contemplated Transactions, the change of control of Boundless Bio resulting from the Contemplated Transactions, the Nasdaq Reverse Split and the increase in 

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authorized shares contemplated by the Parent Charter Amendment (as defined in the Merger Agreement). In addition, Serapha stockholders must adopt the Merger Agreement and approve the Merger and the related transactions. Failure to obtain the required stockholder approvals may result in a material delay in, or the abandonment of, the Merger. Any delay in completing the Merger may materially adversely affect the timing and benefits that are expected to be achieved from the Merger.

The Merger may be completed even though a material adverse effect may result from the announcement of the Merger, industrywide changes or other causes.

In general, neither Boundless Bio nor Serapha is obligated to complete the Merger if there is a material adverse effect (as defined in the Merger Agreement) affecting the other party between June 22, 2026, the date of the Merger Agreement, and the closing of the Merger. However, certain types of causes are excluded from the concept of a material adverse effect. Such exclusions include, but are not limited to, changes in general economic or political conditions, industrywide changes, changes resulting from the announcement of the Merger, natural disasters, pandemics, other public health events or force majeure events and changes in U.S. generally accepted accounting principles. Certain of these exclusions are subject to a limitation and will not apply to the extent Boundless Bio or Serapha, as applicable, is disproportionately affected relative to other similarly situated companies in the industries in which they operate. Therefore, if any of these events were to occur and adversely affect Boundless Bio or Serapha, the adverse effect may not constitute a material adverse effect under the Merger Agreement, and the other party may still be required to complete the closing of the Merger notwithstanding such material adverse effect. If any such adverse effects occur and Boundless Bio completes the closing of the Merger, the stock price of the Combined Company may suffer. This in turn may reduce the value of the Merger to the stockholders of Boundless Bio, Serapha or both.

If the Merger is not completed, Boundless Bios stock price may decline significantly.

The market price of Boundless Bio Common Stock is subject to significant fluctuations. Market prices for securities of pharmaceutical, biotechnology and other life science companies have historically been particularly volatile. In addition, the market price of Boundless Bio Common Stock will likely be volatile based on whether stockholders and other investors believe that Boundless Bio can complete the Merger or otherwise raise additional capital to support Boundless Bios operations if the Merger is not completed and another strategic transaction cannot be identified, negotiated and completed in a timely manner, if at all. The volatility of the market price of Boundless Bio Common Stock has been and may be exacerbated by low trading volume.

Additional factors that may cause the market price of Boundless Bio Common Stock to fluctuate include:

announcements of the results of its clinical trials, discussions with regulators, and regulatory approval decisions;

the entry into, or termination of, key agreements, including commercial partner agreements;

announcements by commercial partners or competitors of new commercial products, clinical progress or lack thereof, significant contracts, commercial relationships or capital commitments;

the loss of key employees;

future sales of Boundless Bio Common Stock;

general and industryspecific economic conditions that may affect Boundless Bios research and development expenditures; and

periodtoperiod fluctuations in financial results.

Moreover, the stock markets in general have experienced substantial volatility that has often been unrelated to the operating performance of individual companies. These broad market fluctuations may also adversely affect the trading price of Boundless Bio Common Stock. In the past, following periods of volatility in the market price of a companys securities, stockholders have often instituted class action securities litigation against such companies.

If Boundless Bio completes the Merger, the Combined Company will need to raise additional capital, including by potentially issuing equity securities or incurring debt, which may cause significant dilution to the Combined Companys stockholders or restrict the Combined Companys operations.

In connection with the execution and delivery of the Merger Agreement, Serapha completed the Series A Financing, raising aggregate gross proceeds of approximately $138 million, and has entered into the Securities Purchase Agreement to complete the Serapha Pre-Closing Financing for aggregate gross proceeds of approximately $92 million. The closing of the Serapha PreClosing Financing is a condition to the Closing, and the closing of the Serapha PreClosing Financing is also conditioned upon satisfaction or 

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waiver of the conditions to the Closing, as well as certain other conditions. The shares of Serapha Common Stock and the Serapha prefunded warrants issued in the Serapha PreClosing Financing will result in dilution to all securityholders of the Combined Company (i.e., both Boundless Bios preMerger securityholders and former Serapha securityholders). 

Additional or alternative financing may not be available to the Combined Company when it is needed or may not be available on favorable terms. To the extent that the Combined Company raises additional capital by issuing equity securities, such financing will cause additional dilution to all securityholders of the Combined Company, including Boundless Bios preMerger securityholders and Seraphas former securityholders. It is also possible that the terms of any new equity securities may have preferences over the Combined Company common stock. Any debt financing the Combined Company enters into may involve covenants that restrict its operations. These restrictive covenants may include limitations on additional borrowing and specific restrictions on the use of the Combined Companys assets, as well as prohibitions on its ability to create liens, pay dividends, redeem its stock or make investments. In addition, if the Combined Company raises additional funds through licensing arrangements, it may be necessary to grant licenses on terms that are not favorable to the Combined Company.

Some of Boundless Bios and Seraphas directors and executive officers have interests in the Merger that are different from yours and that may influence them to support or approve the Merger without regard to your interests.

Directors and executive officers of Boundless Bio and Serapha have interests in the Merger that are different from, or in addition to, the interests of other Boundless Bio stockholders generally. These interests with respect to Boundless Bios directors and executive officers may include, among others, retention bonus payments, acceleration of previously issued equity awards, severance payments if employment is terminated in a qualifying termination in connection with the Merger and rights to continued indemnification, expense advancement and insurance coverage.

Further, certain current members of the Serapha Board of Directors may continue as directors of the Combined Company after the Effective Time, and, following the closing of the Merger, would be eligible to be compensated as nonemployee directors of the Combined Company. These interests, among other factors, may have influenced the directors and executive officers of each company to support or approve the Merger.

The Boundless Bio Board of Directors was aware of and considered those interests, among other matters, in reaching their decisions to approve and adopt the Merger Agreement, approve the Merger, and recommend the approval of the Merger Agreement to Boundless Bio stockholders. These interests, among other factors, may have influenced the directors and executive officers of each company to support or approve the Merger.

Boundless Bio stockholders and Serapha stockholders may not realize a benefit from the Merger commensurate with the ownership dilution they will experience in connection with the Merger, including the conversion of Serapha Common Stock issued in the Serapha PreClosing Financing.

If the Combined Company is unable to realize the full strategic and financial benefits currently anticipated from the Merger, Boundless Bio stockholders and Serapha stockholders will have experienced substantial dilution of their ownership interests without receiving any commensurate benefit, or only receiving part of the commensurate benefit to the extent the Combined Company is able to realize only part of the strategic and financial benefits currently anticipated from the Merger.

Boundless Bio securityholders will generally have a reduced ownership and voting interest in, and will exercise less influence over the management of, the Combined Company following the completion of the Merger as compared to their current ownership and voting interests in the respective companies.

After the completion of the Merger, Boundless Bios current stockholders will generally own a smaller percentage of the Combined Company than their ownership of Boundless Bio prior to the Merger. Immediately after the Merger, Boundless Bio securityholders as of immediately prior to the Merger are expected to own approximately 3.69% of the outstanding shares of capital stock of the Combined Company (on a fullydiluted basis, and subject to dilution from any equity issued by Serapha after June 22, 2026 and before the closing), and former holders of Serapha securities are expected to own approximately 96.31% of the outstanding shares of capital stock of the Combined Company (on a fullydiluted basis), subject to certain assumptions, including, but not limited to, Boundless Bio Net Cash as of closing being approximately $0, after giving effect to the Pre-Closing Dividend, which is expected to be approximately $44 to $48 million.

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Certain provisions of the Merger Agreement may discourage third parties from submitting competing proposals, including proposals that may be superior to the transactions contemplated by the Merger Agreement.

While the Merger Agreement is in effect, each of Boundless Bio and Serapha is generally prohibited from, among other things, soliciting, initiating or knowingly encouraging, inducing or facilitating the communication, making, submission or announcement of any acquisition proposal or acquisition inquiry. In addition, Boundless Bios current directors and executive officers have entered into support agreements pursuant to the terms of the Merger Agreement, and as an inducement to Seraphas willingness to enter into the Merger Agreement, by which they have agreed to vote all of their shares of Boundless Bio Capital Stock in favor of the Contemplated Transactions and against any competing proposals, subject to certain limited exceptions. These provisions could discourage a potential competing acquirer from considering or proposing an acquisition or merger, even if it were prepared to pay consideration with a higher value than that implied by the merger consideration in the combination.

Because the lack of a public market for Serapha Common Stock makes it difficult to evaluate the fair market value of its capital stock, the value of Boundless Bio Common Stock to be issued to Serapha stockholders may be more or less than the fair market value of Serapha Common Stock.

The outstanding capital stock of Serapha is privately held and is not traded on any public market. The lack of a public market makes it difficult to determine the fair market value of Serapha capital stock. Because the percentage of Boundless Bios equity to be issued to Serapha stockholders was determined based on negotiations between the parties, it is possible that the value of Boundless Bio Common Stock to be issued to Serapha stockholders will be more or less than the fair market value of Serapha Capital Stock.

Lawsuits may be filed against Boundless Bio, Serapha, or any of the members of their respective boards of directors arising out of the Merger, which may delay or prevent the Merger.

Putative stockholder complaints, including stockholder class action complaints, and other complaints may be filed against Boundless Bio, the Boundless Bio Board of Directors, Serapha, the Serapha Board of Directors and others in connection with the transactions contemplated by the Merger Agreement. The outcome of litigation is uncertain, and Boundless Bio or Serapha may not be successful in defending against any such future claims. Lawsuits that may be filed against Boundless Bio, the Boundless Bio Board of Directors, Serapha, or the Serapha Board of Directors could delay or prevent the Merger, divert the attention of Boundless Bios and Seraphas management and employees from their daytoday business and otherwise adversely affect Boundless Bio and Serapha financially.

Boundless Bio has never paid and, other than in connection with the Merger with Serapha, does not intend to pay any cash dividends in the foreseeable future.

Boundless Bio has never paid cash dividends on any of its capital stock. Other than the Pre-Closing Dividend in connection with the Merger, Boundless Bio does not currently anticipate declaring or paying cash dividends on its capital stock in the foreseeable future.

The amount of the Pre-Closing Dividend may change based on the timing to complete the Merger, changes in operating expense levels and other factors.

The Pre-Closing Dividend, which is expected to be approximately $44 to $48 million, is based on Boundless Bio's estimate of the amount by which Boundless Bio Net Cash, as determined pursuant to the terms of the Merger Agreement, will exceed $0. The actual amount of the Pre-Closing Dividend may be higher or lower than the estimated amount and is subject to change based on the timing to complete the Merger, changes in Boundless Bio's operating expense levels, transaction-related costs and expenses, and other adjustments to the components of Boundless Bio Net Cash as set forth in the Merger Agreement. There can be no assurance that the actual amount of the Pre-Closing Dividend will not materially differ from the current estimate.

If Boundless Bio does not successfully complete the Merger or another strategic transaction, the Boundless Bio Board of Directors may decide to pursue a dissolution and liquidation of Boundless Bio. In such an event, the amount of cash available for distribution to Boundless Bio stockholders will depend heavily on the timing of such liquidation as well as the amount of cash that will need to be reserved for commitments and contingent liabilities, as to which Boundless Bio can give you no assurance.

There can be no assurance that the Merger will be completed. If the Merger is not completed, the Boundless Bio Board of Directors may decide to pursue a dissolution and liquidation of Boundless Bio. In such an event, the amount of cash available for distribution to Boundless Bio stockholders will depend heavily on the timing of such decision and, ultimately, such liquidation, since the amount of cash available for distribution continues to decrease as Boundless Bio funds its operations while pursuing the Merger. In addition, if the Boundless Bio Board of Directors were to approve and recommend, and Boundless Bio stockholders were to 

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approve, a dissolution and liquidation of Boundless Bio, Boundless Bio would be required under Delaware law to pay Boundless Bios outstanding obligations, as well as to make reasonable provision for contingent and unknown obligations, prior to making any distributions in liquidation to stockholders. Boundless Bios commitments and contingent liabilities may include obligations under Boundless Bios employment and related agreements with certain employees that provide for severance and other payments following a termination of employment occurring for various reasons, including a change in control of Boundless Bio, litigation against Boundless Bio, and other various claims and legal actions arising in the ordinary course of business, and other unexpected and/or contingent liabilities. As a result of this requirement, a portion of Boundless Bios assets would need to be reserved pending the resolution of such obligations.

In addition, Boundless Bio may be subject to litigation or other claims related to a dissolution and liquidation of Boundless Bio. If a dissolution and liquidation were to be pursued, the Boundless Bio Board of Directors, in consultation with Boundless Bios advisors, would need to evaluate these matters and make a determination about a reasonable amount to reserve. Accordingly, holders of Boundless Bio Common Stock could lose all or a significant portion of their investment in the event of liquidation, dissolution or winding up of Boundless Bio. A liquidation would be a lengthy and uncertain process with no assurance of any value ever being returned to Boundless Bio stockholders.

Boundless Bio and its stockholders will not have any right to make damage claims against Serapha for the breach of any representation, warranty or covenant made by Serapha in the Merger Agreement.

The Merger Agreement provides that all of the representations, warranties and covenants of the parties contained therein shall not survive the Closing, except for those covenants contained therein that by their terms survive the Closing. Accordingly, there are no remedies available to the parties with respect to any breach of the representations, warranties, covenants or agreements of the parties to the Merger Agreement after the Closing, except for covenants that by their terms survive the Closing. As a result, Boundless Bio and its stockholders will have no remedy available to it if the Merger is completed and it is later revealed that there was a breach of any of the representations, warranties and covenants made by Serapha at the time of the Merger.

Additionally, Boundless Bio cannot assure you that the due diligence conducted in relation to Serapha has identified all material issues or risks associated with Serapha, its business or the industry in which it competes. Furthermore, Boundless Bio cannot assure you that factors outside of its or Seraphas control will not later arise, or that any previously identified risks will not materialize in a manner inconsistent with the preliminary analysis. As a result of these factors, following the Closing, the Combined Company may be exposed to liabilities and incur additional costs and expenses and it may be forced to later writedown or write off assets, restructure its operations, or incur impairment or other charges. Boundless Bio and its stockholders have no indemnification rights against Serapha or its stockholders under the Merger Agreement. Accordingly, any stockholders of Boundless Bio that remain stockholders of the Combined Company following the Merger could suffer a reduction in the value of their securities. Such stockholders are unlikely to have a remedy for such reduction in value unless they are able to successfully claim that the reduction was due to the breach by Boundless Bios directors or officers of a duty of care or other fiduciary duty owed to them, or if they are able to successfully bring a private claim under securities laws that the registration statement or proxy statement/prospectus relating to the Merger contained an actionable material misstatement or material omission.