# BBI-355

Source: https://onco.cc/drugs/bbi-355/  
OnCo record `bbi-355` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

BBI-355 is an oral small-molecule inhibitor from Boundless Bio that reached phase 1 for solid tumours with oncogene amplifications; development has stopped.

## Summary

BBI-355 is an oral small-molecule inhibitor from Boundless Bio. An oral selective inhibitor of checkpoint kinase 1, designed to target replication stress in oncogene-amplified cancers. Its furthest stage is phase 1, for solid tumours with oncogene amplifications. ClinicalTrials.gov registers it in one study linked below. Monotherapy and third-party combination arms of POTENTIATE stopped May 2025; enrolment of the BBI-355 + BBI-825 combination ceased January 2026; wind-down ongoing (10-Q). Registry NCT05827614 TERMINATED. Whether it works in people has not been established unless a trial below reports it.

## Fields

- Kind: Treatment
- Status: phase-1
- Last checked: 2026-11-03
- Tags: pipeline; ctgov-ingest; discontinued
- Code: BBI-355
- Modality: Oral small-molecule inhibitor
- Mechanism: An oral selective inhibitor of checkpoint kinase 1, designed to target replication stress in oncogene-amplified cancers.

## Sources

- Boundless Bio: sec.gov: https://www.sec.gov/Archives/edgar/data/0001782303/000119312526339093/bold-20260630.htm
- Boundless Bio: sec.gov: https://www.sec.gov/Archives/edgar/data/0001782303/000119312526339093/bold-20260630.htm
- Boundless Bio: clinicaltrials.gov: https://clinicaltrials.gov/study/NCT05827614
- ClinicalTrials.gov: trials of BBI-355: https://clinicaltrials.gov/search?intr=BBI-355

## Connected records

- cancers: [Metastatic cancer (cancer that has spread)](https://onco.cc/cancers/metastatic-cancer/)
- targets: [CHEK1](https://onco.cc/targets/chek1/)
- companies: [Boundless Bio](https://onco.cc/companies/boundless-bio/)
- trials: [Study of the CHK1 Inhibitor BBI-355, an ecDNA-directed Therapy (ecDTx), and the RNR Inhibitor BBI-825, in Subjects With Tumors With Oncogene Amplifications](https://onco.cc/trials/nct05827614/)

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