Preferred investors in BillionToOne (NASDAQ: BLLN) report IPO share conversion

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) insiders reported a large structural change in their holdings tied to the company’s initial public offering. Investment entities affiliated with Hummingbird funds and HB&Q NV converted multiple series of preferred stock into common stock on a one-for-one basis automatically immediately prior to the closing of BillionToOne’s IPO of Class A common stock, without any cash changing hands.

Immediately before the IPO, each share of common stock was then automatically reclassified into one share of Class A common stock under a Rule 16b-7–exempt reclassification. After these steps, the Hummingbird-affiliated entities reported Class A common stock positions, including 2,631,664 shares and 2,580,833 shares for certain funds. Humming Bird Ventures Management NV may be deemed to beneficially own shares held by the Hummingbird funds, while its partners, including Firat Ileri, Barend Van den Brande, and Lukas Decoster, disclaim beneficial ownership beyond their economic interests.

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

OMB APPROVAL

OMB Number:			3235-0287
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hours per response:			0.5

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

Check this box to indicate that a transaction was made pursuant to a contract, instruction or written plan for the purchase or sale of equity securities of the issuer that is intended to satisfy the affirmative defense conditions of Rule 10b5-1(c). See Instruction 10.

1. Name and Address of Reporting Person^*

Humming Bird Ventures Management NV

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(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)

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

3. Date of Earliest Transaction (Month/Day/Year)
11/07/2025

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

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

	Form filed by One Reporting Person
X	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)
			Code	V	Amount	(A) or (D)	Price
Common Stock	11/07/2025		C(1)(2)		640,727	A	(2)	640,727	I	See Footnotes(3)(8)
Common Stock	11/07/2025		C(1)(2)		18,845	A	(2)	18,845	I	See Footnotes(4)(8)
Common Stock	11/07/2025		C(1)(2)		2,015,118	A	(2)	2,015,118	I	See Footnotes(5)(8)
Common Stock	11/07/2025		C(1)(2)		2,451,665	A	(2)	2,631,664	I	See Footnotes(6)(8)
Common Stock	11/07/2025		C(1)(2)		2,580,833	A	(2)	2,580,833	I	See Footnotes(7)(8)
Common Stock	11/07/2025		J(9)		640,727	D	(9)	0	I	See Footnotes(3)(8)
Common Stock	11/07/2025		J(9)		18,845	D	(9)	0	I	See Footnotes(4)(8)
Common Stock	11/07/2025		J(9)		2,015,118	D	(9)	0	I	See Footnotes(5)(8)
Common Stock	11/07/2025		J(9)		2,631,664	D	(9)	0	I	See Footnotes(6)(8)
Common Stock	11/07/2025		J(9)		2,580,833	D	(9)	0	I	See Footnotes(7)(8)
Class A Common Stock	11/07/2025		J(9)		640,727	A	(9)	640,727	I	See Footnotes(3)(8)
Class A Common Stock	11/07/2025		J(9)		18,845	A	(9)	18,845	I	See Footnotes(4)(8)
Class A Common Stock	11/07/2025		J(9)		2,015,118	A	(9)	2,015,118	I	See Footnotes(5)(8)
Class A Common Stock	11/07/2025		J(9)		2,631,664	A	(9)	2,631,664	I	See Footnotes(6)(8)
Class A Common Stock	11/07/2025		J(9)		2,580,833	A	(9)	2,580,833	I	See Footnotes(7)(8)

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)
				Code	V	(A)	(D)	Date Exercisable	Expiration Date	Title	Amount or Number of Shares
Series B-2 Convertible Preferred Stock	(2)	11/07/2025		C			640,727	(2)	(2)	Common Stock	640,727	(2)	0	I	See Footnotes(3)(8)
Series B-1 Convertible Preferred Stock	(2)	11/07/2025		C			18,845	(2)	(2)	Common Stock	18,845	(2)	0	I	See Footnotes(4)(8)
Series C Convertible Preferred Stock	(2)	11/07/2025		C			1,569,015	(2)	(2)	Common Stock	1,569,015	(2)	0	I	See Footnotes(5)(8)
Series D Convertible Preferred Stock	(2)	11/07/2025		C			446,103	(2)	(2)	Common Stock	446,103	(2)	0	I	See Footnotes(5)(8)
Series A-1 Convertible Preferred Stock	(2)	11/07/2025		C			20,000	(2)	(2)	Common Stock	20,000	(2)	0	I	See Footnotes(6)(8)
Series A-2 Convertible Preferred Stock	(2)	11/07/2025		C			33,000	(2)	(2)	Common Stock	33,000	(2)	0	I	See Footnotes(6)(8)
Series B-1 Convertible Preferred Stock	(2)	11/07/2025		C			2,261,377	(2)	(2)	Common Stock	2,261,377	(2)	0	I	See Footnotes(6)(8)
Series C Convertible Preferred Stock	(2)	11/07/2025		C			137,288	(2)	(2)	Common Stock	137,288	(2)	0	I	See Footnotes(6)(8)
Series A-6 Convertible Preferred Stock	(2)	11/07/2025		C			2,260,520	(2)	(2)	Common Stock	2,260,520	(2)	0	I	See Footnotes(7)(8)
Series B-2 Convertible Preferred Stock	(2)	11/07/2025		C			320,363	(2)	(2)	Common Stock	320,363	(2)	0	I	See Footnotes(7)(8)

1. Name and Address of Reporting Person^*

Humming Bird Ventures Management NV

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Hummingbird Opportunity Fund II CommV

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Hummingbird Ventures III CommV

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Hummingbird Dragons CommV

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Hummingbird Collective CommV

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

HB&Q NV (HB&Q COMPARTMENT III)

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Van den Brande Barend

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

1. Name and Address of Reporting Person^*

Decoster Lukas

(Last) (First) (Middle)

SQUARE VICTORIA REGAIN 1

(Street)

SINT-JOOST-TEN-NODE C9 1210

(City) (State) (Zip)

Relationship of Reporting Person(s) to Issuer

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

Explanation of Responses:

1. The total represents shares received upon conversion of shares of Series A-1 Convertible Preferred Stock, Series A-2 Convertible Preferred Stock, Series A-6 Convertible Preferred Stock, Series B-1 Convertible Preferred Stock, Series B-2 Convertible Preferred Stock, Series C Convertible Preferred Stock and/or Series D Convertible Preferred Stock.

2. 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.

3. The reported security is directly held by HB&Q NV (HB&Q COMPARTMENT III).

4. The reported security is directly held by Hummingbird Collective CommV.

5. The reported security is directly held by Hummingbird Dragons CommV.

6. The reported security is directly held by Hummingbird Opportunity Fund II CommV.

7. The reported security is directly held by Hummingbird Ventures III CommV.

8. Humming Bird Ventures Management NV is the managing member of Hummingbird Opportunity Fund II CommV, Hummingbird Ventures III CommV, Hummingbird Dragons CommV, Hummingbird Collective CommV, and HB&Q NV (HB&Q COMPARTMENT III) (the Hummingbird Funds) and, as a result, may be deemed to beneficially own shares held by the Hummingbird Funds. Mr. Ileri, Barend Van den Brande, and Lukas Decoster are partners of Hummingbird Ventures Management NV and may be deemed to have shared voting and investment power over the shares held by the Hummingbird Funds. The Reporting Persons disclaim beneficial ownership of these shares except to the extent of their pecuniary interests therein.

9. 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.

	Hummingbird Ventures Management NV /s/ Lukas Decoster 49/9 CommV, represented by its permanent representative Lukas Decoster, Director	01/20/2026
	/s/ Barend Van den Brande	01/20/2026
	/s/ Lukas Decoster	01/20/2026
	Hummingbird Opportunity Fund II CommV /s/ Firat Ileri By: Hummingbird Ventures Management NV, its Manager By: Firat Ileri, Permanent Representative	01/20/2026
	Hummingbird Ventures III CommV /s/ Firat Ileri By: Hummingbird Ventures Management NV, its Manager By: Firat Ileri, Permanent Representative	01/20/2026
	Hummingbird Dragons CommV /s/ Firat Ileri By: Hummingbird Ventures Management NV, its Manager By: Firat Ileri, Permanent Representative	01/20/2026
	Hummingbird Collective CommV /s/ Firat Ileri By: Hummingbird Ventures Management NV, its Manager By: Firat Ileri, Permanent Representative	01/20/2026
	HB&Q NV /s/ Firat Ileri By: Hummingbird Ventures Management NV, its Manager By: Firat Ileri, Permanent Representative	01/20/2026
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 4 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What insider activity did BillionToOne (BLLN) disclose in this Form 4?

The filing shows that investment entities affiliated with the Hummingbird funds and HB&Q NV converted multiple series of preferred stock into BillionToOne common stock, which was then automatically reclassified into Class A common stock in connection with the company’s initial public offering.

Were the preferred shares of BillionToOne converted at a specific ratio?

Yes. The reported preferred securities converted into BillionToOne’s common stock on a one-for-one basis immediately prior to the closing of the IPO of Class A common stock, as described in the footnotes.

Did the insiders pay anything to convert the BillionToOne preferred stock?

No. The footnotes state that the preferred stock converted into the issuer’s common stock without payment of further consideration, meaning there was no additional cash outlay required for the conversion.

What happened to BillionToOne common stock before the IPO?

Immediately prior to completion of the offering, each share of BillionToOne common stock was automatically reclassified into one share of Class A common stock under a reclassification that is described as exempt under Rule 16b-7.

Which entities now hold Class A common stock of BillionToOne (BLLN)?

Class A common shares are reported as held by entities including HB&Q NV (HB&Q COMPARTMENT III), Hummingbird Collective CommV, Hummingbird Dragons CommV, Hummingbird Opportunity Fund II CommV, and Hummingbird Ventures III CommV, with Humming Bird Ventures Management NV as managing member of these funds.

How much Class A common stock do the Hummingbird-related funds report after the reclassification?

After the conversions and reclassification, the filing reports Class A common stock positions for these funds, including 2,631,664 shares and 2,580,833 shares for certain Hummingbird-affiliated entities, alongside additional reported Class A holdings at other funds.

Do individual partners directly own the reported BillionToOne shares?

The footnotes state that Humming Bird Ventures Management NV may be deemed to beneficially own shares held by the Hummingbird funds, and that partners Firat Ileri, Barend Van den Brande, and Lukas Decoster may share voting and investment power, but the reporting persons disclaim beneficial ownership except to the extent of their pecuniary interests.