Company: BLLN
Filing Date: 2025-10-07
Form Type: S-1
Source: 0001193125-25-233697
Chunk: 214

Company: BillionToOne, Inc.
Filing Date: 2025-10-07
Form: S-1
Chunk 214
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 presence / absence determined as early as 9 weeks 40% fetal RhD not detected: Rho(D) immune globulin not indicated UNITY Fetal Antigen NIPT Alloimmunization occurs when a pregnant individual’s immune system produces antibodies against fetal red blood cell (RBC) antigens. This can happen when a RhD negative pregnant mother carrying an RhD positive fetus does not receive RhIG. This can also happen with other rare RBC antigens are present, such as Kell, especially due to a blood transfusion prior to the pregnancy. This can lead to HDFN, a condition that can cause

| 56 |     | Wynn, J., Rego, S., Fang, J., Alford, B., Carter, R., & Hoskovec, J. (2024). Performance Characteristics of a Next Generation Sequencing-Based cfDNA Assay for Common Aneuploidies in a General Risk Population. Annals 
 of Gynecology and Obstetrics Research, 7(1), 1027.                                                                                                                                                                      |

| 57 |     | Percentage based on an internal validation report we issued in January 2025 conducted by an independent third party lab. |

| 58 |     | Rego, S., Balogun, O. A., Emanuel, K., Overcash, R., Gonzalez, J. M., Denomme, G. A., Hoskovec, J., King, H., Wilson, A., Wynn, J., & Moise, K. J. Jr. (2024). Cell-free DNA analysis for the determination of fetal 
 red blood cell antigen genotype in individuals with alloimmunized pregnancies. Obstetrics & Gynecology, 144(4), 436-443.                                                                                             |

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severe anemia, hydrops fetalis, or fetal demise. Managing these pregnancies is challenging. The current methods to determine fetal antigen status, such as amniocentesis, are often invasive. These invasive procedures could cause maternal and fetal blood to mix, which would exacerbate HDFN. As a result, many patients experience undue anxiety, unnecessary and expensive weekly monitoring, frequent antibody titer checks, and intensive surveillance. In approximately 65% of these pregnancies, the fetus is negative for the antigen and therefore there is no fetal risk. 59 To address this issue, we launched UNITY Fetal Antigen NIPT in 2022. Our UNITY Fetal Antigen NIPT addresses a critical