SEC FORM 4

SEC Form 4

FORM 4

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

STATEMENT OF CHANGES IN BENEFICIAL OWNERSHIP

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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Check this box if no longer subject to Section 16. Form 4 or Form 5 obligations may continue. See Instruction 1(b).

1. Name and Address of Reporting Person^*

Bremner Thomas S

(Last)

(First)

(Middle)

1 NORTH WACKER DRIVE, SUITE 2200

(Street)

CHICAGO

60606-2807

(City)

(State)

(Zip)

2. Issuer Name and Ticker or Trading Symbol
BillionToOne, Inc. [ BLLN ]

5. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

X	Director	10% Owner
	Officer (give title below)	Other (specify below)

3. Date of Earliest Transaction (Month/Day/Year)
11/06/2025

4. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Acquired, Disposed of, or Beneficially Owned
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	3. Transaction Code (Instr. 8)		4. Securities Acquired (A) or Disposed Of (D) (Instr. 3, 4 and 5)			5. Amount of Securities Beneficially Owned Following Reported Transaction(s) (Instr. 3 and 4)	6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Security (Instr. 3)	2. Transaction Date (Month/Day/Year)	2A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	Amount	(A) or (D)	Price		6. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	7. Nature of Indirect Beneficial Ownership (Instr. 4)
Common Stock	11/06/2025		A		8,333⁽¹⁾	A	$0	8,333	D
Common Stock	11/07/2025		C⁽²⁾⁽³⁾		152,440	A	⁽³⁾	152,440	I	See Footnotes⁽⁴⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		C⁽²⁾⁽³⁾		155,711	A	⁽³⁾	155,711	I	See Footnotes⁽⁵⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		C⁽²⁾⁽³⁾		176,271	A	⁽³⁾	176,271	I	See Footnotes⁽⁶⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		C⁽²⁾⁽³⁾		269,918	A	⁽³⁾	269,918	I	See Footnotes⁽⁷⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		C⁽²⁾⁽³⁾		240,072	A	⁽³⁾	240,072	I	See Footnotes⁽⁸⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		C⁽²⁾⁽³⁾		675,352	A	⁽³⁾	675,352	I	See Footnotes⁽⁹⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		C⁽²⁾⁽³⁾		277,508	A	⁽³⁾	277,508	I	See Footnotes⁽¹⁰⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		J⁽¹³⁾		8,333	D	⁽¹³⁾	0	D
Common Stock	11/07/2025		J⁽¹³⁾		152,440	D	⁽¹³⁾	0	I	See Footnotes⁽⁴⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		J⁽¹³⁾		155,711	D	⁽¹³⁾	0	I	See Footnotes⁽⁵⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		J⁽¹³⁾		176,271	D	⁽¹³⁾	0	I	See Footnotes⁽⁶⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		J⁽¹³⁾		269,918	D	⁽¹³⁾	0	I	See Footnotes⁽⁷⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		J⁽¹³⁾		240,072	D	⁽¹³⁾	0	I	See Footnotes⁽⁸⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		J⁽¹³⁾		675,352	D	⁽¹³⁾	0	I	See Footnotes⁽⁹⁾⁽¹¹⁾⁽¹²⁾
Common Stock	11/07/2025		J⁽¹³⁾		277,508	D	⁽¹³⁾	0	I	See Footnotes⁽¹⁰⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		J⁽¹³⁾		8,333	A	⁽¹³⁾	8,333	D
Class A Common Stock	11/07/2025		J⁽¹³⁾		152,440	A	⁽¹³⁾	152,440	I	See Footnotes⁽⁴⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		J⁽¹³⁾		155,711	A	⁽¹³⁾	155,711	I	See Footnotes⁽⁵⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		J⁽¹³⁾		176,271	A	⁽¹³⁾	176,271	I	See Footnotes⁽⁶⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		J⁽¹³⁾		269,918	A	⁽¹³⁾	269,918	I	See Footnotes⁽⁷⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		J⁽¹³⁾		240,072	A	⁽¹³⁾	240,072	I	See Footnotes⁽⁸⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		J⁽¹³⁾		675,352	A	⁽¹³⁾	675,352	I	See Footnotes⁽⁹⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		J⁽¹³⁾		277,508	A	⁽¹³⁾	277,508	I	See Footnotes⁽¹⁰⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		P		4,016	A	$60	156,456	I	See Footnotes⁽⁴⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		P		4,084	A	$60	159,795	I	See Footnotes⁽⁵⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		P		3,462	A	$60	179,733	I	See Footnotes⁽⁶⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		P		5,446	A	$60	275,364	I	See Footnotes⁽⁷⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		P		6,867	A	$60	246,939	I	See Footnotes⁽⁸⁾⁽¹¹⁾⁽¹²⁾
Class A Common Stock	11/07/2025		P		17,791	A	$60	693,143	I	See Footnotes⁽⁹⁾⁽¹¹⁾⁽¹²⁾

Table II - Derivative Securities Acquired, Disposed of, or Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	4. Transaction Code (Instr. 8)		5. Number of Derivative Securities Acquired (A) or Disposed of (D) (Instr. 3, 4 and 5)		6. Date Exercisable and Expiration Date (Month/Day/Year)		7. Title and Amount of Securities Underlying Derivative Security (Instr. 3 and 4)		8. Price of Derivative Security (Instr. 5)	9. Number of derivative Securities Beneficially Owned Following Reported Transaction(s) (Instr. 4)	10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
1. Title of Derivative Security (Instr. 3)	2. Conversion or Exercise Price of Derivative Security	3. Transaction Date (Month/Day/Year)	3A. Deemed Execution Date, if any (Month/Day/Year)	Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares	8. Price of Derivative Security (Instr. 5)		10. Ownership Form: Direct (D) or Indirect (I) (Instr. 4)	11. Nature of Indirect Beneficial Ownership (Instr. 4)
Series A-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			1,352	⁽³⁾	⁽³⁾	Common Stock	1,352	⁽³⁾	0	I	See Footnotes⁽⁴⁾⁽¹¹⁾⁽¹²⁾
Series C Convertible Preferred Stock	⁽³⁾	11/07/2025		C			114,117	⁽³⁾	⁽³⁾	Common Stock	114,117	⁽³⁾	0	I	See Footnotes⁽⁴⁾⁽¹¹⁾⁽¹²⁾
Series C-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			16,747	⁽³⁾	⁽³⁾	Common Stock	16,747	⁽³⁾	0	I	See Footnotes⁽⁴⁾⁽¹¹⁾⁽¹²⁾
Series D Convertible Preferred Stock	⁽³⁾	11/07/2025		C			20,224	⁽³⁾	⁽³⁾	Common Stock	20,224	⁽³⁾	0	I	See Footnotes⁽⁴⁾⁽¹¹⁾⁽¹²⁾
Series C Convertible Preferred Stock	⁽³⁾	11/07/2025		C			121,688	⁽³⁾	⁽³⁾	Common Stock	121,688	⁽³⁾	0	I	See Footnotes⁽⁵⁾⁽¹¹⁾⁽¹²⁾
Series C-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			17,858	⁽³⁾	⁽³⁾	Common Stock	17,858	⁽³⁾	0	I	See Footnotes⁽⁵⁾⁽¹¹⁾⁽¹²⁾
Series D Convertible Preferred Stock	⁽³⁾	11/07/2025		C			16,165	⁽³⁾	⁽³⁾	Common Stock	16,165	⁽³⁾	0	I	See Footnotes⁽⁵⁾⁽¹¹⁾⁽¹²⁾
Series A-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			1,562	⁽³⁾	⁽³⁾	Common Stock	1,562	⁽³⁾	0	I	See Footnotes⁽⁶⁾⁽¹¹⁾⁽¹²⁾
Series C Convertible Preferred Stock	⁽³⁾	11/07/2025		C			131,888	⁽³⁾	⁽³⁾	Common Stock	131,888	⁽³⁾	0	I	See Footnotes⁽⁶⁾⁽¹¹⁾⁽¹²⁾
Series C-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			19,355	⁽³⁾	⁽³⁾	Common Stock	19,355	⁽³⁾	0	I	See Footnotes⁽⁶⁾⁽¹¹⁾⁽¹²⁾
Series D Convertible Preferred Stock	⁽³⁾	11/07/2025		C			23,466	⁽³⁾	⁽³⁾	Common Stock	23,466	⁽³⁾	0	I	See Footnotes⁽⁶⁾⁽¹¹⁾⁽¹²⁾
Series A-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			1,864	⁽³⁾	⁽³⁾	Common Stock	1,864	⁽³⁾	0	I	See Footnotes⁽⁷⁾⁽¹¹⁾⁽¹²⁾
Series C Convertible Preferred Stock	⁽³⁾	11/07/2025		C			157,404	⁽³⁾	⁽³⁾	Common Stock	157,404	⁽³⁾	0	I	See Footnotes⁽⁷⁾⁽¹¹⁾⁽¹²⁾
Series C-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			23,100	⁽³⁾	⁽³⁾	Common Stock	23,100	⁽³⁾	0	I	See Footnotes⁽⁷⁾⁽¹¹⁾⁽¹²⁾
Series D Convertible Preferred Stock	⁽³⁾	11/07/2025		C			87,550	⁽³⁾	⁽³⁾	Common Stock	87,550	⁽³⁾	0	I	See Footnotes⁽⁷⁾⁽¹¹⁾⁽¹²⁾
Series A-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			652	⁽³⁾	⁽³⁾	Common Stock	652	⁽³⁾	0	I	See Footnotes⁽⁸⁾⁽¹¹⁾⁽¹²⁾
Series C Convertible Preferred Stock	⁽³⁾	11/07/2025		C			55,091	⁽³⁾	⁽³⁾	Common Stock	55,091	⁽³⁾	0	I	See Footnotes⁽⁸⁾⁽¹¹⁾⁽¹²⁾
Series C-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			8,084	⁽³⁾	⁽³⁾	Common Stock	8,084	⁽³⁾	0	I	See Footnotes⁽⁸⁾⁽¹¹⁾⁽¹²⁾
Series D Convertible Preferred Stock	⁽³⁾	11/07/2025		C			176,245	⁽³⁾	⁽³⁾	Common Stock	176,245	⁽³⁾	0	I	See Footnotes⁽⁸⁾⁽¹¹⁾⁽¹²⁾
Series A-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			5,988	⁽³⁾	⁽³⁾	Common Stock	5,988	⁽³⁾	0	I	See Footnotes⁽⁹⁾⁽¹¹⁾⁽¹²⁾
Series C Convertible Preferred Stock	⁽³⁾	11/07/2025		C			505,570	⁽³⁾	⁽³⁾	Common Stock	505,570	⁽³⁾	0	I	See Footnotes⁽⁹⁾⁽¹¹⁾⁽¹²⁾
Series C-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			74,195	⁽³⁾	⁽³⁾	Common Stock	74,195	⁽³⁾	0	I	See Footnotes⁽⁹⁾⁽¹¹⁾⁽¹²⁾
Series D Convertible Preferred Stock	⁽³⁾	11/07/2025		C			89,599	⁽³⁾	⁽³⁾	Common Stock	89,599	⁽³⁾	0	I	See Footnotes⁽⁹⁾⁽¹¹⁾⁽¹²⁾
Series A-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			1,078	⁽³⁾	⁽³⁾	Common Stock	1,078	⁽³⁾	0	I	See Footnotes⁽¹⁰⁾⁽¹¹⁾⁽¹²⁾
Series C Convertible Preferred Stock	⁽³⁾	11/07/2025		C			91,003	⁽³⁾	⁽³⁾	Common Stock	91,003	⁽³⁾	0	I	See Footnotes⁽¹⁰⁾⁽¹¹⁾⁽¹²⁾
Series C-1 Convertible Preferred Stock	⁽³⁾	11/07/2025		C			13,355	⁽³⁾	⁽³⁾	Common Stock	13,355	⁽³⁾	0	I	See Footnotes⁽¹⁰⁾⁽¹¹⁾⁽¹²⁾
Series D Convertible Preferred Stock	⁽³⁾	11/07/2025		C			122,072	⁽³⁾	⁽³⁾	Common Stock	122,072	⁽³⁾	0	I	See Footnotes⁽¹⁰⁾⁽¹¹⁾⁽¹²⁾

Explanation of Responses:

1. Each restricted stock unit ("RSU") represents a contingent right to receive one share of the Issuer's Common Stock. The RSUs shall vest over three years in equal annual installments on the anniversary of November 6, 2025, subject to the Reporting Person's continuous service to the Issuer through each such vesting date.

2. The total represents shares received upon conversion of shares of Series A-1 Convertible Preferred Stock, Series C Convertible Preferred Stock, Series C-1 Convertible Preferred Stock and/or Series D Convertible Preferred Stock.

3. The reported security converted into the Issuer's Common Stock on a one-for-one basis automatically immediately prior to the closing of the Issuer's initial public offering of Class A common stock (the "Offering") without payment of further consideration. The shares have no expiration date.

4. The reported security is directly held by Adams Street 2019 Direct Growth Equity Fund LP.

5. The reported security is directly held by Adams Street 2020 Direct Growth Equity Fund LP.

6. The reported security is directly held by Adams Street 2021 Direct Growth Equity Fund LP.

7. The reported security is directly held by Adams Street 2022 Direct Growth Equity Fund LP.

8. The reported security is directly held by Adams Street Private Equity Navigator Fund LLC (f/k/a Adams Street Global Private Markets Fund LP).

9. The reported security is directly held by Adams Street Growth Equity Fund VII LP.

10. The reported security is directly held by FCPR GF - Lumyna Private Equity World Fund.

11. Adams Street Partners, LLC is the managing member of the general partner of each of Adams Street 2019 Direct Growth Equity Fund LP, Adams Street 2020 Direct Growth Equity Fund LP, Adams Street 2021 Direct Growth Equity Fund LP, Adams Street 2022 Direct Growth Equity Fund LP, Adams Street Growth Equity Fund VII LP, and Adams Street Private Equity Navigator Fund LLC (f/k/a Adams Street Global Private Markets Fund LP) (collectively, the U.S. Funds) and, as a result, may be deemed to beneficially own the shares held by the U.S. Funds. Furthermore, Adams Street Partners, LLC, is the Sous-Delegataire Financier of the Delegataire Financier of the management company of FCPR GF - Lumyna Private Equity World Fund (Lumyna and together with the U.S. Funds, the Funds) and, as a result, may be deemed to beneficially own the shares held by Lumyna.

12. (Continued from footnote 11) Thomas S. Bremner, Jeffrey T. Diehl, Brian Dudley, Elisha P. Gould, Robin Murray and Fred Wang, each of whom is a partner of Adams Street Partners, LLC (or a subsidiary thereof), may be deemed to have shared voting, investment and dispositive power over the shares held by the Funds. The Reporting Person disclaims beneficial ownership of these shares except to the extent of his pecuniary interest therein.

13. Pursuant to a reclassification exempt under Rule 16b-7, each share of Common Stock was automatically reclassified into one share of Class A common stock immediately prior to the completion of the Offering.

	/s/ Thomas P. Lynch, Attorney-in-Fact	11/10/2025
	** Signature of Reporting Person	Date
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