Apr 6, 2026 · 20m · y-combinator
BillionToOne Is Solving One of Biotech’s Hardest Problems · Y Combinator
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Host Jared Friedman tours BillionToOne with co-founders Oguzhan Atay and David Tsao to explore how the company revolutionized cell-free DNA diagnostics using Quantitative Counting Templates (QCTs). The episode highlights their trajectory from Y Combinator startup to a multi-billion-dollar public company expanding from prenatal screening to life-saving cancer liquid biopsy products.
How this conversation actually went
Every chapter scored 0–10 on four independent dynamics. Hover any point for the reasoning behind the score. The partners hold 25.3% of the talking time here. How this is scored →
The partners as informed peer 3.4 Guest teaching 2.2 Guest disagreement 0.2 The partners pushing back 0.2
speaking balance: gold is the partners, purple is the guest (3 minute bins)
Sharpest disagreement ▶ 16:59 Nuancing the Tesla master plan analogy
Ozan mildly pushes back on Jared's Tesla analogy, emphasizing that unlike high-end consumer luxury cars, diagnostic healthcare products cannot start at elite price points.
Hardest push from the partners ▶ 18:54 Questioning feasibility of early detectionJared presses the founders on why early cancer detection has eluded the entire biotech industry despite decades of immense capital investment.
Biggest teaching moment ▶ 3:17 Explaining synthetic DNA noise reductionOzan systematically explains how PCR introduces massive background noise and how spiked synthetic molecules turn a messy biological challenge into a mathematical calibration problem.
The partners hold their own ▶ 4:31 Detailed explanation of QCT error correctionJared exhibits strong technical domain knowledge by synthesizing and clarifying the precise machine learning and error-subtraction pipeline for the audience.
the scores for every segment, with the reasoning behind each
| Chapter | Topic | The partners as informed peer | Guest teaching | Guest disagreement | The partners pushing back | Why |
|---|---|---|---|---|---|---|
| BillionToOne Overview & Market Scale | 5 | 3 | 0 | 0 | Jared sets up the technical premise and delivers a detailed breakdown of how synthetic DNA spike-ins remove amplification noise. Ozan explains their quantitative counting template approach in an informative, non-adversarial manner. | |
| Founding Story & First-Principles Approach | 3 | 1 | 0 | 0 | The conversation is an aligned retrospective on the early struggles of the company, from sharing half a lab bench to overhauling commercial sales. The host facilitates the story with supportive follow-ups. | |
| Behind-the-Scenes Tour: Clinical Lab Sample Workflow | 3 | 3 | 0 | 0 | Jared tours the clinical lab and observes the sample pooling process, framing it as computational magic. Ozan clarifies the specific barcoding and sequencing workflow used across multiplexed patient samples. | |
| Strategic Expansion into Oncology & Liquid Biopsy | 2 | 2 | 0 | 0 | Jared asks how the fetal DNA detection technology translates to liquid biopsy in oncology. David shares a compelling clinical case study of metastatic colorectal cancer treatment matching. | |
| Interdisciplinary Hiring & Autonomous R&D Culture | 4 | 2 | 1 | 1 | Jared draws an analogy between BillionToOne's multi-stage strategy and Tesla's secret master plan. Ozan gently qualifies the comparison by highlighting that healthcare tests must be broadly affordable from day one. |
Statements from this episode (17)
Friedman: BillionToOne Went Public at Over $4 Billion Valuation
“Late last year, they took the company public at a valuation over four billion dollars.”
Bilgen: BillionToOne Processes Over 600,000 Tests Annually With ~20% Market Share
“We are processing more than 600,000 tests a year, and in terms of the overall market share, We are close to 20% market share there.”
Friedman: Most genetic abnormalities previously required invasive amniocentesis for detection
“Before Billion to One, most genetic abnormalities could only be detected via amniocentesis, an invasive procedure that is only used in high-risk pregnancies.”
Bilgen: Synthetic DNA removes PCR amplification noise from sequencing data
“So what we have done is to add a synthetic DNA into the patient sample that we get before any amplification happens. These synthetic DNA Allow us to know how much amplification happened at different genomic locations. You know, what are the errors that are bei…”
Bilgen: Chemistry experts rarely possess data science and bioinformatics skills
“People who understand chemistry Tend to be not the kind of data scientists and bioinformaticians that analyze the data.”
Bilgen: BillionToOne raised initial $300,000 in $10k checks over six months
“First 300,000 dollars that, you know, I've raised was, you know, really, really difficult. It took, you know, six months, and it was, you know, 10,000 dollars at a time”
Bilgen: BillionToOne had only one doctor ordering tests two months post-launch
“Launched in June, only person that is using the test, you know, two months later is this one Physician, and who is sending, like, maybe one or two tests per week.”
Bilgen: Current facility can scale to nearly two million tests annually
“We believe that we can expand into close to two million tests per year just using this facility. That would be, you know, around essentially every one in three babies that would be tested with our tests.”
Bilgen: Founders planned three-stage expansion from prenatal to early-stage cancer
“One year into the company, it is actually laid out that, you know, we would start at prenatal genetics, then go into late stage cancers, and then go into early stage cancers in this way.”
Bilgen: Fetal and tumor cell-free DNA are fundamentally identical to detect
“And, you know, we realized that, you know, fundamentally there is nothing different about, you know, cell-free fetal DNA and cell-free tumor DNA, and the same technology can be applied to both of them.”
Bilgen: Starting in oncology would have made initial commercialization far harder
“Because if we started, I think, on the oncology side, it would have been far more difficult to achieve that initial successful commercialization that gave us more resources to be able to build, you know, new tests and improve the existing tests.”
Tsao: NorthStar Select found actionable cancer targets missed by tissue biopsy
“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 w…”
Bilgen: Interdisciplinary scientists accelerate R&D by an order of magnitude
“We have found that having that iterative cycle within one scientist actually accelerates the work that they do by an order of magnitude.”
Bilgen: Small R&D teams own products and report directly to co-founders
“We actually have very small you know, research teams. It is essentially principal investigators, like a scientist who is interdisciplinary, who has a small team of, you know, two or three research associates, and they all directly report to David and me, and t…”
Bilgen: 20% of early-stage cancer surgery patients retain undetectable microscopic residue
“The problem is that in about 20% of these patients, actually, there is a microscopic residue remaining, and they cannot be detected by scans.”
Bilgen: MRD cancer detection shares same technical challenge as population screening
“If you can detect a microscopic level of DNA and be able to say that that is actually cancer, that is the same really technical problem as being able to detect those in healthy patients or, you know, general population.”