Boundless Bio cuts about one-third of workforce, narrows pipeline, sees cash into 2028

Boundless Bio, Inc. (Nasdaq: BOLD) said on May 23, 2025 that it is cutting about one-third of its workforce, narrowing its pipeline and extending its expected cash runway into the first half of 2028. The company disclosed the changes in a Form 8-K under Items 2.05 and 8.01. Item 2.05 covers costs tied to exit or disposal activities, such as a workforce reduction.

The company expects one-time costs of about $1.2 million for the reduction, mainly termination benefits, some of them contractual. The filing says the reduction is expected to be substantially complete in the second quarter of 2025. It cautions that actual results may differ materially and that other costs may arise.

What it is dropping

The company will stop the current arms of its POTENTIATE trial of BBI-355, an oral, selective CHK1 inhibitor. The filing says BBI-355 showed a narrow therapeutic index with continuous every other day dosing, with hematologic toxicity at or near the doses linked to clinical activity. Combinations with the EGFR inhibitor erlotinib and the FGFR inhibitor futibatinib were not well tolerated at the exposure levels believed to be required. The company believes that narrow therapeutic index makes BBI-355 suboptimal for continued development as a single agent with continuous dosing.

Boundless also has a prior setback. Last year it decided not to advance its STARMAP trial of BBI-825, a ribonucleotide reductase inhibitor, partly because BBI-825 induced its own metabolism with continuous twice daily dosing.

The new plan rests on preclinical data

Boundless now wants to combine BBI-825 with BBI-355 without continuous dosing. Its support is preclinical: synergistic cell killing in cancer cell lines and tumor regression in mouse xenograft models using weekly dosing. The company plans to start clinical development of the combination in 2025 and expects initial proof-of-concept data within the extended runway. It has scheduled a live webcast on Tuesday, May 27, 2025 at 8:00 am ET to present the supporting detail.

The Kinesin program is the other pillar. It targets a kinesin involved in DNA segregation, including extrachromosomal DNA (ecDNA) segregation, during mitosis. Boundless selected BBI-940 as its development candidate and reaffirmed that it expects to file an Investigational New Drug application in the first half of 2026. Its evidence so far is anti-tumor activity in cancer cell lines and tumor regressions in mouse models.

Cash runway

The company reported cash, cash equivalents and short-term investments of $138.3 million as of March 31, 2025. It says the cash, together with the portfolio changes and streamlined operations, extends its runway into the first half of 2028 and through anticipated proof-of-concept readouts for each program.

The company's 10-K for 2024 reported a net loss of $65.4 million, negative operating cash flow of $60.8 million and an accumulated deficit of $201.5 million at December 31, 2024. The forward-looking statements list the risks to the plan. Boundless says it is early in its development efforts and that its approach to ecDNA-directed therapeutics is novel and unproven. It also flags that it may not realize the expected benefits of the prioritization and the workforce reduction, may be unable to retain key personnel, and may use its capital sooner than it expects.

Who signed

Jessica Oien, Chief Legal Officer and Corporate Secretary, signed the 8-K.

What comes next

The next dated items are the May 27, 2025 webcast, the planned start of the combination trial in 2025, and the BBI-940 IND filing in the first half of 2026. The runway depends on the cash balance holding up through those readouts, and the 8-K gives no data for the combination in patients.

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