Boundless Bio is a clinical stage, next-generation precision oncology company developing innovative therapeutics directed against extrachromosomal DNA (ecDNA) for patients with oncogene amplified cancers.


The oversubscribed Series C financing is 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. The capital raised will fund initial clinical development of BBI-355, a checkpoint kinase 1 (CHK1) inhibitor and the first ecDNA-directed therapy


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).