Tsao: NorthStar Select found actionable cancer targets missed by tissue biopsy
David Tsao · BillionToOne Is Solving One of Biotech’s Hardest Problems · Y Combinator · Apr 6, 2026 · at 14:30
David Tsao, co-founder and CTO of BillionToOne, discusses a clinical case study showing how their liquid biopsy test found actionable mutations in a terminal cancer patient after tissue biopsy failed.
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“We ended up testing this person using our North Star Select test. We identified that this person was eligible for A therapy called immunotherapy based on identifying microsatellite instability in the tumor DNA that was in that patient's bloodstream, and this was a little bit like a last-ditch effort because they had already done the tumor testing, and there's no kind of indication from the tumor test that this type of therapy would work, but because of how the tumor had mis-sized into many different locations, probably what happened was the exact location of the biopsy was done just didn't happen to have that alteration, but the other Places and the cancer sites did.”
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