Funding advances BBI-355, a potentially best-in-class checkpoint kinase 1 (CHK1) inhibitor, through meaningful clinical data readouts in Phase 1/2 POTENTIATE clinical trial

Boundless Bio, a clinical stage, next-generation precision oncology company developing innovative therapeutics directed against extrachromosomal DNA (ecDNA) for patients with oncogene amplified cancers, today announced the closing of a $100 million Series C financing co-led by Leaps by Bayer, the impact investment arm of Bayer AG, and RA Capital Management, with participation from additional new investors, Sectoral Asset Management and Piper Heartland Healthcare Capital. Boundless Bio will use the financing to advance BBI-355, the first ecDNA-directed therapy (ecDTx), through meaningful clinical readouts from its ongoing Phase 1/2 clinical trial in patients with oncogene-amplified cancers.

Historically, targeted therapies and immunotherapies have been largely ineffective in treating patients with oncogene amplified cancers. Boundless Bio is the first company wholly dedicated to developing novel therapeutics for patients with oncogene amplified cancers, specifically those enabled by ecDNA. Absent in normal healthy tissue, ecDNA have been observed in 14% of early-stage cancers and up to 40% of metastatic cancers and drive both oncogenesis as well as resistance to current therapeutic approaches. Boundless Bio is leveraging a unique understanding of the vulnerabilities of ecDNA biology with the aim to deliver potentially transformative therapies to the up to 400,000 patients newly diagnosed in the US each year with previously intractable oncogene amplified cancers.

The capital raised will fund initial clinical development of BBI-355, as a single agent and in combination with select therapies, for multiple cancer indications with oncogene amplifications being evaluated in the ongoing Phase 1/2 POTENTIATE clinical trial (NCT05827614). BBI-355 is an orally available, potent, and selective CHK1 inhibitor, which has been shown preclinically to be synthetically lethal to ecDNA-bearing oncogene-amplified cancer cells. The new funds will also support advancement of Boundless Bio’s preclinical pipeline of differentiated ecDTx candidates and its proprietary ecDNA diagnostic clinical trial assay, ECHO (ecDNA Harboring Oncogenes), which is being developed in partnership with SOPHiA GENETICS.

“At Leaps by Bayer, we invest in fundamental breakthroughs in healthcare,” said Juergen Eckhardt, M.D., EVP and Head of Leaps by Bayer. “The ability to address oncogene amplified cancers has remained one of the industry’s greatest challenges in the treatment of cancer. We are thrilled to support Boundless Bio, a company whose innovations have the potential to impact the lives of patients who currently have no effective standard of care.”

The Series C financing included participation from existing investors Fidelity Management & Research Company LLC, ARCH Venture Partners, Nextech Invest, Wellington Management, Vertex Ventures HC, Redmile Group, Surveyor Capital (a Citadel company), GT Healthcare Capital Partners, Alexandria Venture Investments, PFM Health Sciences, Logos Capital, and City Hill Ventures. In conjunction with the financing, Fabio Pucci, Ph.D., Senior Director of Venture Investments Health at Leaps by Bayer, will join the Boundless Bio Board of Directors.

“We are excited to have Leaps by Bayer join our world-class investor syndicate and to welcome Fabio Pucci to our Board of Directors,” said Zachary Hornby, President and Chief Executive Officer of Boundless Bio. “The support from new investors along with the continued commitment of our existing investors emphasizes our momentum and progress in bringing the first ecDNA-directed therapies to patients with oncogene-amplified cancers.”

About BBI-355

BBI-355 is a potentially best-in-class checkpoint kinase 1 (CHK1) inhibitor and the first ecDNA-directed therapy (ecDTx) being investigated to treat patients with oncogene amplified cancer. CHK1 is a master regulator of DNA replication stress (RS), which frequently arises from oncogene amplification on ecDNA. Inhibition of CHK1 by BBI-355 is synthetic lethal in cancer cells with oncogene amplification on ecDNA due to their heightened RS. CHK1 was identified and validated as an ecDNA essential target via Boundless Bio’s proprietary Spyglass research platform, leading Boundless Bio to develop BBI-355, an orally available, potent, and selective CHK1 inhibitor. BBI-355 is being evaluated in a first-in-human trial (“POTENTIATE”: Precision Oncology Trial Evaluating Novel Therapeutic Interrupting Amplifications Tied to ecDNA) designed to evaluate the safety, maximum tolerated dose, and recommended Phase 2 dose of BBI-355 as a single agent and in combination with select therapies in patients with locally advanced or metastatic solid tumors with oncogene amplifications (NCT05827614).

About Boundless Bio

Boundless Bio is a clinical stage, next-generation precision oncology company dedicated to the discovery and development of new drugs targeting a novel area of cancer biology, ecDNA, to deliver transformative therapies intended to improve and extend the lives of patients with oncogene amplified cancers.

For more information, visit www.boundlessbio.com.

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About Bayer

Bayer is a global enterprise with core competencies in the life science fields of health care and nutrition. Its products and services are designed to help people and the planet thrive by supporting efforts to master the major challenges presented by a growing and aging global population. Bayer is committed to driving sustainable development and generating a positive impact with its businesses. At the same time, the Group aims to increase its earning power and create value through innovation and growth. The Bayer brand stands for trust, reliability and quality throughout the world. In fiscal 2021, the Group employed around 100,000 people and had sales of 44.1 billion euros. R&D expenses before special items amounted to 5.3 billion euros. For more information, go to www.bayer.com

About Leaps by Bayer

Leaps by Bayer, a unit of Bayer AG, leads impact investments into solutions to some of today’s biggest challenges in health and agriculture. The investment portfolio includes more than 50 companies. They are all working on potentially breakthrough technologies to overcome some specific challenges such as, e.g., developing a sustainable protein supply, reducing the environmental impact of agriculture, preventing or curing cancer, and others. For more information, go to leaps.bayer.com.

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