Company: BLLN
Filing Date: 2025-08-11
Form Type: DRS/A
Source: 0000950123-25-007483
Chunk: 209

Company: BillionToOne, Inc.
Filing Date: 2025-08-11
Form: DRS/A
Chunk 209
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. As a
result, the patient avoided the need for weekly intensive monitoring by a specialist, invasive procedures, and regular blood draws, significantly reducing healthcare costs and her anxiety. This early identification through the UNITY Fetal Antigen
NIPT provided critical information that guided the management of her pregnancy, ensuring it progressed without complications related to alloimmunization. This case highlights the value of UNITY Fetal Antigen NIPT in streamlining prenatal care,
minimizing unnecessary interventions and risks, and removing the fear of the unknown for the patient.

Northstar patient case study: Northstar Select identified a new ESR1 mutation at a very low VAF in a metastatic breast cancer patient after signs of progression using Northstar Response

A patient was
diagnosed with HR positive/HER2 negative metastatic breast cancer and was heavily pretreated with anastrozole/ribociclib. During the patient’s routine follow-up three years later, the patient began
Northstar Response monitoring, which indicated low baseline tumor burden (TMS=63). Longitudinal monitoring revealed progressively increasing TMS scores with a 390-fold increase found five months
afterwards (TMS=67,000).

Subsequent comprehensive profiling with Northstar Select revealed an ESR1 S463P mutation at a VAF of 0.09%, significantly below
any competing therapy selection test’s limit of detection, confirming the emergence of a resistance mutation to aromatase inhibitor therapy, a common challenge in treating HR-positive metastatic breast
cancer. ESR1 S463P mutations have an FDA-approved therapy, elacestrant, in this indication and provided this patient with an opportunity for treatment.

This case highlights how utilizing both Northstar Select and Response can help physicians first timely detect disease progression and identify more actionable mutations
at greater sensitivity, leading to earlier interventions and better treatment options for patients.

157

Longitudinal Tumor Methylation ScoreTM (TMSTM) 100,000 10,000 1,000 100 25 170 63 Day 0 Treatment anastrozole + ribociclib 67,000 139 286 PROGRESSIVE DISEASE Key Insights from Northstar Baseline TMS Increase: ~3X Profiling Northstar Select GNAS R201H (0.08%) TMS Increase: ~390X Profiling Northstar Select CDK4 amp (8.86 copies) ESR1 S463P (0.09%) ESR1 L536P