Boundless Bio Presents Preclinical and Clinical Pharmacodynamic Data on its Lead Extrachromosomal DNA (ecDNA)-Directed Therapy, BBI-355, at the American Association for Cancer Research Annual Meeting 2024 - Seite 3

About BBI-355

Boundless Bio’s lead ecDNA-directed therapy (ecDTx), BBI-355, is a novel, oral, selective inhibitor of checkpoint kinase 1 (CHK1) being studied in the ongoing, first-in-human, Phase 1/2 POTENTIATE clinical trial (NCT05827614) in patients with oncogene amplified cancers. CHK1 is a master regulator of cells’ response to replication stress (RS). RS is elevated in ecDNA-enabled oncogene amplified cancer cells and, because of this, represents a key vulnerability of those cells. BBI-355 was designed to exploit the elevated RS in ecDNA-enabled oncogene amplified cancer cells by disrupting proper CHK1 function in regulating RS and thereby facilitating catastrophic RS to preferentially kill cancer cells relative to healthy cells.

About Boundless Bio

Boundless Bio is a clinical-stage oncology company dedicated to unlocking a new paradigm in cancer therapeutics to address the significant unmet need of patients with oncogene amplified tumors by targeting extrachromosomal DNA (ecDNA), a root cause of oncogene amplification and observed in more than 14% of cancer patients. Boundless Bio is developing the first ecDNA-directed therapy (ecDTx), BBI-355, which is an oral inhibitor of checkpoint kinase 1 (CHK1) and is being evaluated in a Phase 1/2 clinical trial in patients with oncogene amplified cancers. Boundless Bio’s second ecDTx, BBI-825, is an oral inhibitor of ribonucleotide reductase (RNR) and recently entered a Phase 1/2 clinical trial in cancer patients with resistance gene amplifications. Leveraging its Spyglass platform, Boundless Bio has additional programs advancing through preclinical development and discovery. Boundless Bio is headquartered in San Diego, CA.

For more information, visit www.boundlessbio.com.

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Forward-Looking Statements

Boundless Bio cautions you that statements contained in this press release regarding matters that are not historical facts are forward-looking statements. The forward-looking statements are based on our current beliefs and expectations and include, but are not limited to: the potential therapeutic benefits of our ecDTx in treating patients with oncogene amplified cancers; and the possibility to extend potential applicability of ecDTx beyond targeted therapy resistance. Actual results may differ from those set forth in this press release due to the risks and uncertainties inherent in our business, including, without limitation: we are early in our development efforts and our approach to discover and develop ecDTx directed against ecDNA in oncogene amplified cancers is novel and unproven; results from preclinical studies or early clinical trials not necessarily being predictive of future results; potential delays in the commencement, enrollment, data readouts or completion of clinical trials or preclinical studies; our dependence on third parties in connection with clinical trials, preclinical studies, ecDNA diagnostic development, and manufacturing; unfavorable results from clinical trials or preclinical studies; unexpected adverse side effects or inadequate efficacy of our ecDTx that may limit their development, regulatory approval, and/or commercialization; regulatory developments in the United States and foreign countries; and other risks described in our filings with the Securities and Exchange Commission (SEC), including under the heading “Risk Factors” in the final prospectus dated March 27, 2024 that we filed with the SEC and any subsequent filings with the SEC. You are cautioned not to place undue reliance on these forward-looking statements, which speak only as of the date hereof, and we undertake no obligation to update such statements to reflect events that occur or circumstances that exist after the date hereof. All forward-looking statements are qualified in their entirety by this cautionary statement, which is made under the safe harbor provisions of the Private Securities Litigation Reform Act of 1995.