What We Do

A New Approach To Cancer Treatment


We develop ecDNA-directed therapies (ecDTx) intended to transform the lives of patients with aggressive gene amplified cancers.

Our Pipeline

BBio Pipeline Diagram Spyglass

Through our proprietary Spyglass platform, Boundless Bio has identified three distinct vulnerabilities of ecDNA-driven cancers: (1) ecDNA Replication Stress, (2) ecDNA Assembly and Repair, and (3) ecDNA Segregation

ecDNA Replication Stress

Cancer cells with oncogene amplifications on ecDNA exhibit elevated levels of replication stress (RS), a cellular condition where the DNA replication process is dysregulated and leads to potentially toxic DNA damage to cells.  As a consequence, ecDNA amplified tumor cells undergoing elevated RS invoke certain cellular RS response factors, which renders them hypersensitive to inhibition of those factors.

Our first ecDTx, BBI-355, is a novel, potent, selective, oral drug that inhibits checkpoint kinase 1 (CHK1), one of cells’ master regulators of RS arising from ecDNA-based oncogene amplification.  Inhibition of CHK1 by BBI-355 is synthetic lethal in ecDNA-enabled oncogene amplified cancer cells due to their exquisite reliance on CHK1 to manage their intrinsically elevated RS.  This results in tumor growth inhibition and tumor regressions in multiple oncogene amplified mouse tumor xenograft models.  BBI-355 is currently being tested in a first-in-human Phase 1/2 study in patients with oncogene amplified tumor-agnostic cancers. The study is called POTENTIATE (Precision Oncology Trial Evaluating Novel Therapeutic Interrupting Amplifications Tied to ecDNA).

To learn more about the POTENTIATE study, please visit ClinicalTrials.gov Study Identifier  NCT05827614.

In addition, we have developed a 2nd generation, brain penetrant CHK1 inhibitor, BBI-098, that is potent, selective, and orally available.  BBI-098 has the potential to be developed in the future as a treatment for patients with central nervous system cancers such as glioblastoma or brain metastases.

ecDNA Assembly and Repair

In order to maintain ecDNA, ecDNA-enabled cancer cells have increased demand for the raw materials normally used for DNA synthesis and replication.  As a consequence, disruption of the supply of raw materials necessary for ecDNA assembly and repair can lead to cancer cell death.

Our second ecDTx, BBI-825, is a novel, potent, selective, oral drug that inhibits ribonucleotide reductase (RNR), a rate-limiting enzyme essential for the production of deoxyribonucleotide triphosphates (dNTP) required for ecDNA assembly and repair.  Accordingly, inhibition of RNR represents a synthetic lethality of ecDNA-enabled cancer cells. BBI-825 has demonstrated preclinical proof of concept in multiple tumor types across different ecDNA-enabled settings, including both driver oncogene and resistance .   IND-enabling studies for BBI-825 are underway.

ecDNA Segregation

ecDNA lack centromeres, the structural component of chromosomes that is required for proper segregation during cell division.  Thus, segregation and subsequent inheritance of ecDNA is dependent on alternative cellular mechanisms that Boundless Bio has begun to uncover.  We have identified and validated a novel protein target essential for ecDNA segregation whose inhibition is synthetic lethal to ecDNA-enabled cancer cells. We have a drug discovery effort directed to this novel target (ecDTx 3) with the intention to identify a first in class development candidate.

New ecDNA Targets and Mechanisms

Beyond the three ecDTx described above we continue to leverage our Spyglass platform to identify additional targets required for ecDNA-enabled oncogene amplified tumors.

Boundless Bio, with its world leading understanding of ecDNA, is the only company delivering new therapeutic options to improve and extend the lives of patients with oncogene amplified cancers enabled by ecDNA.

What are ecDNA?


ecDNA are a primary site for activating oncogene amplifications in cancer. 

ecDNA are large units of circular DNA that reside within the nuclei of cells yet are physically distinct from chromosomal DNA. They often range in size from 1-3 mega base pairs in length and can encode one or more full-length genes and regulatory regions. ecDNA have accessible chromatin and are highly transcribed, meaning they are fully functional and often more active than chromosomally located genes. ecDNA are one of the primary locations for high copy number focal oncogene amplifications in cancer cells; in fact, more than half of all high copy number amplifications in cancer occur on ecDNA.

Spyglass: the only-in-class platform built to identify vulnerabilities of ecDNA in cancer

BBI Spyglass

Boundless Bio’s Spyglass platform consists of a comprehensive suite of proprietary ecDNA+/- models across tumor types and oncogene amplifications.  Leveraging innovative molecular analytical technologies and imaging techniques, Spyglass enables characterization of ecDNA in cancer cells and provides a synthetic lethality-based approach to targeting ecDNA-bearing cancers.  Through the use of Spyglass, Boundless Bio scientists have thus far identified and validated four distinct and druggable cellular targets that are essential to the function of ecDNA in cancer cells.

ecDNA are a cancer specific phenomenon

Absent in normal healthy tissue, ecDNA are found in over 20% of primary and metastatic cancers.

Driving high copy number gene amplifications and non-Mendelian genomic adaptation, ecDNA enable tumors to rapidly evolve and switch their oncogene dependency when under therapeutic pressure, thereby rendering current targeted and immunotherapy approaches largely ineffective in patients with gene amplified cancers.

ecDNA are the next frontier of precision medicine


ECHO (ecDNA Harboring Oncogenes) is a proprietary software system for detecting the presence of ecDNA oncogene amplifications using routine clinical next-generation sequencing (NGS).  ECHO is the first portable precision medicine tool for identifying ecDNA amplified oncogenes and built to be deployable at clinical trial sites or commercial laboratories.

In our mission to deliver transformative precision therapies to patients with aggressive oncogene amplified cancers, ECHO is a vital tool in the development of our ground-breaking ecDTx candidates.

The rapidly growing field of ecDNA cancer biology helps explain why some oncogene amplified cancers are so aggressive and why traditional approaches to treatment are not working for many patients. This new understanding of ecDNA shines light onto innovative and differentiated therapeutic approaches to help those affected by the most aggressive tumors. I am thrilled that Boundless Bio has assembled a world class team that has been able to leverage ecDNA biology to develop a host of innovative drug candidates that have the chance to improve the lives of patients with oncogene amplified cancer.

Paul Mischel, M.D.

Scientific Co-Founder and Chairman of the Scientific Advisory Board

P. Mischel

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