Boundless Bio bumps IPO market back to life after sleepy few weeks

Just when it seemed like the biotech IPOs were being lulled back to sleep, Boundless Bio says it plans to hit Wall Street. 

The Arch-, Bayer- and RA-backed company filed an S-1 Wednesday afternoon, potentially becoming the seventh company to go public this year. The precision oncology company targets extrachromosomal DNA, which are double-stranded molecules that can be the source of cancer-driving genes. Boundless describes itself as “the world’s leading ecDNA company” and also as the only biotech working in the space. 

Boundless raised back-to-back nine-digit private financings in 2021 and 2023, most recently hauling in $100 million last May. The sizable cash infusions have brought the company into the clinic, with two programs in phase 1 studies.

The first program, BBI-335, looks to inhibit checkpoint kinase 1 in the hopes of cooling down ecDNA replication. Boundless said in its filing that it plans to have proof-of-concept and anti-tumor activity data on up to 90 patients in the second half of the year. That asset is followed up by BBI-825, which was launched into its first trial last month. Interim study data are expected in the second half of 2025. 

Those results will likely be pivotal for Boundless’ near-term prospects, with an IND for a third program not expected to be filed until the first half of 2026.

It has taken Boundless less than five years to go public since launching in September 2019, thanks in part to research from Paul Mischel, M.D., a pathologist and cancer biologist at Stanford. Boundless hit the scene with a $49 million series A led by Arch Venture Partners and City Hill Ventures.