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Boundless Bio, Taiho Oncology Partner to Study CHK1 Inhibitor, Lytgobi in Solid Tumors

NEW YORK – Boundless Bio on Monday announced a clinical trial collaboration agreement with Taiho Oncology to study its CHK1 inhibitor BBI-355 with Taiho's FGFR inhibitor Lytgobi (futibatinib) in advanced solid tumors with specific oncogene amplifications.

The Phase I/II trial, called POTENTIATE or Precision Oncology Trial Evaluating Novel Therapeutic Interrupting Amplifications Tied to ecDNA, will include patients with extrachromosomal DNA (ecDNA)-driven cancers, which typically have oncogene amplifications. The trial will have three parts: a BBI-355 monotherapy portion, a dose-escalation combination portion where BBI-355 will be studied with other targeted therapies such as Taiho's Lytgobi, and a dose expansion portion of the BBI-355 combinations that will also use a diagnostic to detect oncogenes amplified on ecDNA.

BBI-355 is a synthetic lethal drug for cancers that have ecDNA replication stress, as the cancer cells rely on CHK1 to manage elevated replication stress. In Boundless' preclinical studies, when CHK1 was inhibited with BBI-355 in these cells, it led to the inhibition of tumor growth and tumor regression.

Under the collaboration agreement, Taiho will supply Lytgobi to the POTENTIATE trial at no cost.

"FGFR inhibitors given as monotherapy have to date demonstrated less clinical benefit in patients with cancer harboring FGFR amplifications than in patients with other FGFR driver alteration types," Boundless CEO Zachary Hornby said in a statement. "We believe that BBI-355, when combined with Taiho's futibatinib, has the potential to demonstrate meaningful anti-tumor activity for patients with cancer and FGFR amplifications."

Boundless, based in San Diego, is also developing other treatments for ecDNA-driven cancers, including drugs targeting ecDNA assembly and repair and ecDNA segregation, and is developing a diagnostic in partnership with Sophia Genetics to detect ecDNA.