Boundless Bio, Inc.

PART I

SPECIAL NOTE REGARDING FORWARD-LOOKING STATEMENTS AND MARKET AND INDUSTRY DATA

This Annual Report on Form 10-K contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended (the Securities Act) and Section 21E of the Securities Exchange Act of 1934, as amended (the Exchange Act). All statements other than statements of historical facts contained in this report are forward-looking statements, including statements regarding our future results of operations and financial position, our use of the net proceeds from the initial public offering of our common stock, the sufficiency of our cash position to fund operations and achievement of milestones, including clinical data readouts and regulatory filings, the timing and likelihood of success, plans, and objectives of management for future operations, business strategy, research and development plans, the anticipated timing, costs, design, and conduct of our ongoing and planned clinical trials and preclinical studies for our extrachromosomal DNA (ecDNA) directed therapeutic candidates (ecDTx), ecDNA diagnostic, our other discovery programs, the timing of expected data readouts, the potential safety and therapeutic benefits of our ecDTx, the potential addressable patient populations for our ecDTx, the timing and likelihood of development candidate nominations from our discovery-stage programs, the timing and likelihood of regulatory filings and approvals for our ecDTx, expected regulatory approval pathways for our ecDTx and any ecDNA diagnostic, our ability to commercialize our ecDTx, if approved, the pricing and reimbursement of our ecDTx, if approved, potential competition for our ecDTx, the potential to develop future ecDTx, the potential benefits of strategic collaborations and our intent to enter into any strategic arrangements, our intellectual property and other market exclusivity strategies.

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. Our forward-looking statements are only predictions. We have based our forward-looking statements largely on our current expectations and projections about future events and financial and other trends that we believe may affect our business, financial condition, and results of operations based upon information available to us as of the date of this report. Such information may be limited or incomplete. Forward-looking statements in this report speak only as of the date of this report and are subject to several risks, uncertainties, and assumptions, including those described in Part I, Item 1, “Business,” and Item 1A, “Risk Factors,” and Part II, Item 7, “Management’s Discussion and Analysis of Financial Condition and Results of Operations.” The events and circumstances reflected in our forward-looking statements may not be achieved or occur and our actual results, performance, or achievements could differ materially from those expressed or implied by our forward-looking statements. Moreover, we operate in an evolving environment. New risk factors and uncertainties may emerge from time to time, and it is not possible for management to predict all risk factors and uncertainties. Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified and some of which are beyond our control, you should not place undue reliance on any forward-looking statement. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events, changed circumstances, or otherwise. 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.

In addition, statements that “we believe” and similarly qualified statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this report, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain, and you are cautioned not to rely unduly upon them.

We obtained the industry, market, and competitive position data used in this report from our own internal estimates and research, as well as from independent market research, industry, and general publications and surveys, governmental agencies, and publicly available information in addition to research, surveys, and studies conducted by third parties. The content of these third-party sources, except to the extent specifically set forth in this report, does not constitute a portion of this report and is not incorporated herein. Internal estimates are derived from publicly available information released by industry analysts and third-party sources, our internal research, and our industry experience and are based on assumptions made by us based on such data and our knowledge of our industry and market, which we believe to be reasonable. In some cases, we do not expressly refer to the sources from which this data is derived. In that regard, when we refer to one or more sources of this type of data in any paragraph, you should assume that other data of this type appearing in the same paragraph is derived from the same sources, unless otherwise expressly stated or the context otherwise requires.

In addition, while we are responsible for all of the disclosure contained in this report and we believe the industry, market, and competitive position data included in this report is reliable and based on reasonable assumptions, such data involve risks and uncertainties and are subject to change based on various factors, including those discussed below under the section titled “Risk Factors Summary” and in Part I, Item 1A, “Risk Factors.” These and other factors could cause results to differ materially from those expressed in the estimates made by the independent parties or by us.

RISK FACTORS SUMMARY

Below is a summary of the principal factors that make an investment in our common stock speculative or risky. This summary does not address all of the risks that we face. Additional discussion of the risks summarized in this risk factors summary, and other risks that we face, can be found in Part I, Item 1A., “Risk Factors,” of this Annual Report on Form 10-K, and should be carefully considered, together with other information in this report and our other filings with the U.S. Securities and Exchange Commission (SEC) before making investment decisions regarding our common stock.

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We have a limited operating history, have incurred significant operating losses since our inception and expect to incur significant losses for the foreseeable future. We may never generate any revenue or become profitable or, if we achieve profitability, we may not be able to sustain it.

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We will require substantial additional financing to finance our operations, and a failure to obtain this necessary capital when needed on acceptable terms, or at all, could force us to delay, limit, reduce or terminate our ecDTx development programs, commercialization efforts or other operations.

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We are early in our development efforts and have only one ecDTx in clinical development. All of our other ecDTx programs are still in the preclinical or discovery stage. If we are unable to successfully develop, obtain regulatory approval, and ultimately commercialize any of our current or future ecDTx, or experience significant delays in doing so, our business will be materially harmed.

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Our approach to treating cancer with oncogene amplifications by developing ecDTx directed against ecDNA is unproven, and we do not know whether we will be able to develop any products of commercial value, or if competing approaches will limit the commercial value of our ecDTx.

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Clinical and preclinical development involves a lengthy and expensive process with uncertain timelines and outcomes, and the results of preclinical studies and early clinical trials are not necessarily predictive of future results. Our ecDTx may not achieve favorable results in clinical trials or preclinical studies or receive regulatory approval on a timely basis, if at all.

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Any difficulties or delays in the commencement or completion, or the termination or suspension, of our current or planned clinical trials or preclinical studies could result in increased costs to us, delay or limit our ability to generate revenue, or adversely affect our commercial prospects.

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Use of our ecDTx could be associated with side effects, adverse events, or other properties or safety risks, which could delay or preclude regulatory approval, cause us to suspend or discontinue clinical trials, abandon an ecDTx, limit the commercial profile of an approved label, or result in other significant negative consequences that could severely harm our business, financial condition, results of operations, and prospects.

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If we are unable to successfully develop an ecDNA diagnostic to enable patient selection for our ecDTx, or if we experience significant delays in doing so, we may not realize the full commercial potential of our ecDTx.

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We face significant competition from entities that have developed or may develop product candidates for cancer, including companies developing novel treatments and technology platforms. If our competitors develop and commercialize their product candidates more rapidly than we do, or their technologies or their product candidates are more effective, safer, or less expensive than our ecDTx, our business and our ability to develop and successfully commercialize ecDTx may be adversely affected.

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We rely on third parties to conduct our clinical trials and preclinical studies, to develop an ecDNA diagnostic, and to manufacture our ecDTx, and these third parties may not perform satisfactorily, which could delay, prevent, or impair our development or commercialization efforts

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If we are unable to obtain, maintain, defend, and enforce patent or other intellectual property protection for our ecDTx, ecDNA diagnostic, or technology, or if the scope of the patent or other intellectual property protection obtained is not sufficiently broad, our competitors or other third parties could develop and commercialize products similar or identical to ours, and our ability to successfully commercialize our ecDTx may be adversely affected.

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The trading price of the shares of our common stock could be highly volatile, and purchasers of our common stock could incur substantial losses.