Y Combinator Startup Podcast This Startup Wants To Catch Cancer Before It Spreads
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Apr 6, 2026 
David Tsao, BillionToOne co-founder and biotech researcher, joins Oguzhan Atay, the company’s co-founder and CEO in molecular diagnostics. They talk about spotting tiny DNA fragments in blood, turning messy biology into math, building a prenatal test at scale, fixing a rough go-to-market strategy, and pushing toward blood tests that could catch cancer before it spreads.
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The Breakthrough Required True Cross Disciplinary Founders
- David Tsao and Oguzhan Atay believe their edge came from combining chemistry intuition with data-analysis skill in the same founders.
- They argue most teams saw either biased sequencing data or wet-lab chemistry, but not both together.
From Half a Bench to a Commercial Test
- They built the first test in six months on half a shared lab bench, then raised the first $300,000 in painful $10,000 increments.
- After launch, only one doctor sent one or two tests weekly until Oguzhan Atay forced a rapid sales hiring push.
Patients Helped Unlock the Sales Motion
- When physician outreach stalled, Oguzhan Atay tried pulling patients in first and teaching them how the test differed so they could persuade doctors.
- One in five patients called back, and those conversations created enough traction to recruit better sales reps.