Company: BLLN
Filing Date: 2025-08-11
Form Type: DRS/A
Source: 0000950123-25-007483
Chunk: 255

Company: BillionToOne, Inc.
Filing Date: 2025-08-11
Form: DRS/A
Chunk 255
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 to pay the exercise price in cash or, with the consent of the compensation committee:

| • |     | with shares of Class A common stock that the optionee already owns; |

| • |     | by an immediate sale of shares through a broker approved by us; |

| • |     | by instructing us to withhold a number of shares having an aggregate fair market value that does not exceed the exercise 
 price; or                                                                                                                |

| • |     | by other methods permitted by applicable law. |

An optionee who exercises a stock appreciation right receives the increase in value of our Class A common stock over the base price. The base price for stock appreciation rights may not be less than 100% of the fair market value of our Class A common stock on the grant date. The settlement value of a stock appreciation right may be paid in cash, shares of our common stock or a combination. Options and stock appreciation rights vest as determined by the compensation committee. In general, they will vest over a four-year period following the date of grant. Options and stock appreciation rights expire at the time determined by the compensation committee but in no event more than ten years after they are granted. These awards generally expire earlier if the participant’s service terminates earlier. Restricted shares and restricted stock units Restricted shares and restricted stock units may be awarded under our 2025 Plan in return for any lawful consideration, and participants who receive restricted shares or stock units generally are not required to pay cash for their awards. In general, these awards will be subject to vesting. Vesting may be based on length of service, the attainment of performance-based milestones or a combination of both, as determined by the compensation committee. 197

Corporate transactions In the event we are a party to a merger, consolidation or certain change in control transactions, outstanding awards granted under our 2025 Plan, and all shares acquired under our 2025 Plan, will be subject to the terms of the definitive transaction agreement (or, if there is no such agreement, as determined by our compensation committee). Unless an award agreement provides otherwise, such treatment may include any of the following with respect to each outstanding award:

| • |     | the continuation, assumption or substitution of an award by a surviving entity or its parent; |

| • |     | the cancellation of an award without payment of any consideration; |

| • |     | the cancellation of the vested portion of an award (and any portion that becomes vested as of the effective time of the                                                                                                                             
 transaction) in exchange