Company: BLLN
Filing Date: 2025-10-17
Form Type: S-1/A
Source: 0001193125-25-242632
Chunk: 12

Company: BillionToOne, Inc.
Filing Date: 2025-10-17
Form: S-1/A
Chunk 12
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 accelerate our research and development initiatives, expand our commercial footprint, and enable us to bring our life-changing diagnostics to more patients. But this offering is about more than capital. It is about setting the stage for our next phase of growth and impact. It is about building the foundation for a company that will stand among the most consequential healthcare innovators of our time. We are not building just another successful company; we are changing the very landscape of healthcare. Millions of patients whose lives will be transformed may never know our name, but they will benefit from what we have built. We invite you to join us in writing this next chapter of medical history. Sincerely, Oguzhan Atay, PhD Co-Founder & CEO

iv

Glossary

As used in this prospectus, unless we state otherwise or the context otherwise requires:

ACOG: American College of Obstetricians and Gynecologists—the primary medical organization that sets the guidelines, practice advisories, and standard of
care for women’s healthcare

Amplification bias: One of the biases caused by PCR amplification during library preparation for NGS. Amplification bias in
PCR occurs as different DNA sequences across the genome amplify at unequal rates due to slight variations in primer binding efficiency, sequence composition, or template accessibility. Because PCR amplification is exponential—doubling with
each cycle—even small differences in amplification efficiency (e.g., 95% versus 90% per cycle) compound dramatically over 25 to 30 cycles of PCR, potentially causing certain sequences to be overrepresented by multiple folds, which can be
particularly problematic when trying to accurately detect and quantify rare cfDNA fragments that may already constitute less than 1% of the total sample

ASP:
Average selling price—The average payment BillionToOne receives per test (inclusive of any non-payments)

Calling threshold: For early cancer detection tests, this is the specific cutoff value at which a test result is classified as “positive” (cancer detected) rather than “negative” (no cancer detected)

CF: Cystic fibrosis—A genetic disorder that can be detected by UNITY tests

cfDNA: Cell-free DNA—Extracellular DNA in blood plasma that is shed from all tissues into the bloodstream. Due to its short half-life, cfDNA has a unique
capability to provide a real-time snapshot of cellular turnover and can be used to diagnose and monitor disease

CNV: Copy number variant—A variation in
gene copies that Northstar Select can detect

Control spike-in:A