Company: BLLN
Filing Date: 2025-10-07
Form Type: S-1
Source: 0001193125-25-233697
Chunk: 278

Company: BillionToOne, Inc.
Filing Date: 2025-10-07
Form: S-1
Chunk 278
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 As of June 30, 2025, we have reserved 12,409,025 shares of our common stock for issuance under the 2018 Plan, all of which may be issued as incentive stock options. Unissued shares subject to awards that expire or 209

become unexercisable without being exercised in full or are surrendered pursuant to an option exchange program and shares that are forfeited, cancelled, reacquired by us or withheld in payment of the purchase price or exercise price of an award or in satisfaction of withholding taxes will again become available for issuance under the 2018 Plan or, following completion of this offering, under the 2025 Plan. Administration Our Board of Directors, or a committee thereof, has administered the 2018 Plan since its adoption; however, following this offering, the compensation committee of our Board of Directors will generally administer the 2018 Plan. The administrator has complete discretion to make all decisions relating to the 2018 Plan and outstanding awards. Eligibility Our employees, non-employee membersof our Board of Directors and consultants, including those of our affiliates, are eligible to participate in the 2018 Plan. However, only our direct employees are eligible to receive incentive stock options. Options The exercise price for options granted under the 2018 Plan is determined by the administrator, but, in the case of ISOs, may not be less than 100% of the fair market value of our common stock on the grant date. Optionees may pay the exercise price in cash or cash equivalents or by one, or any combination of, the following forms of payment, as permitted by the administrator in its sole discretion:

| • |     | Delivery of a promissory note, with the recourse, interest, security and redemption provisions determined by the 
 administrator to the extent permitted under and in accordance with applicable law;                               |

| • |     | Cancellation of indebtedness; |

| • |     | Surrender of shares of common stock that the optionee already owns; or |

| • |     | If our shares of common stock are publicly traded, through a sale of shares subject to the option through a securities 
 broker; or Other methods permitted under applicable laws.                                                              |

Options vest as determined by the administrator. In general, we have granted options that vest over a four-year period. Options expire at the time determined by the administrator, but in no event more than ten years after they are granted, and generally expire earlier if the optionee’s service terminates. Restricted shares