Scientist holding a DNA sample with the results on a computer screen in a laboratory
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Boundless Bio has announced the closing of a $100 million Series C financing co-led by Leaps by Bayer, an investment arm of Bayer AG, and RA Capital Management. Boundless will use the financing to advance BBI-355 through an ongoing Phase I/II clinical trial in patients with oncogene-amplified cancers. BBI-355 is an extrachromosomal DNA (ecDNA)-based potential therapeutic.

The financing includes participation from new investors, including Sectoral Asset Management and Piper Heartland Healthcare Capital.

“At Leaps by Bayer, we invest in fundamental breakthroughs in healthcare,” said Juergen Eckhardt, MD, 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.”

While they have been very effective in certain cases, targeted therapies and immunotherapies have been largely ineffective in patients with oncogene amplified cancers. Boundless estimates there are up to 400,000 patients newly diagnosed in the US each year with previously intractable oncogene amplified cancers.

ecDNA is a type of extrachromosomal circular DNA, which is the product of genomic instability and involved in many diseases, including cancer.

Boundless, which was founded based on work by Stanford’s Paul Mischel, points out that while absent in normal healthy tissue, ecDNA have been observed in 14% of early-stage cancers and up to 40% of metastatic cancers. ecDNA drive both oncogenesis as well as resistance to current therapeutic approaches.

Boundless says BBI-355 is a potentially best-in-class 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.  The drug is orally available and appears potent and selective.

Inhibition of CHK1 by BBI-355 is synthetic lethal in cancer cells with oncogene amplification on ecDNA due to their heightened RS. Boundless identified and validated CHK1 as an ecDNA essential target via the company’s proprietary Spyglass research platform. It is an orally available, potent, and selective CHK1 inhibitor.

The compound will be tested 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 trial (“POTENTIATE”: Precision Oncology Trial Evaluating Novel Therapeutic Interrupting Amplifications Tied to ecDNA)  clinical trial.

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.

“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,” said Zachary Hornby, President and Chief Executive Officer of Boundless Bio.

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