BillionToOne CEO Oguzhan Atay sells 8,333 shares

Atay's reported post-exercise option position was 460,296 options, while his spouse's reported post-sale position was 146,501 shares.

Available on EDGAR 10/30/2026 - 06:54 PM EDT Accepted by SEC EDGAR 10/30/2026 - 06:54 PM EDT Learn about SEC filing dates

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) Chairman and CEO Oguzhan Atay exercised options that were fully vested and exercisable to acquire 8,333 shares of Class A Common Stock at $2.80 per share on October 28, 2026, then sold 8,333 shares at $118 per share. The common-stock acquisition and direct sale were effected pursuant to a Rule 10b5-1 trading plan adopted June 5, 2026. His spouse separately sold 2,667 shares at $118 per share pursuant to a Rule 10b5-1 trading plan adopted June 7, 2026.

Insider Trade Summary 10b5-1

Exercise and sale activity reported; no spread calculated

Exercise and Sale 4 txns

Insider Atay Oguzhan

Role Chairman and CEO

Sold 11,000 shs ($1.30M)

Approx. gross sale proceeds $1.30M

Approx. exercise cost $23K

Type	Security	Shares	Price	Value
Exercise	Stock Option (right to buy) F4	8,333	$2.80	$23K
Exercise	Class A Common Stock F1	8,333	$2.80	$23K
Sale	Class A Common Stock F1	8,333	$118.00	$983K
Sale	Class A Common Stock F2, F3	2,667	$118.00	$315K

Holdings After Transaction: Stock Option (right to buy) — 460,296 contracts (Direct); Class A Common Stock — 0 shares (Direct); Class A Common Stock — 146,501 shares (Indirect, By spouse)

Footnotes (4)

1. F1. The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 5, 2026.
2. F2. The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person's spouse on June 7, 2026.
3. F3. Represents shares held by the Reporting Person's spouse.
4. F4. The options are fully vested and exercisable.

Key Figures

Options exercised: 8,333 shares Exercise price: $2.80 per share Shares sold by Atay: 8,333 shares +4 more

7 metrics

Options exercised 8,333 shares October 28, 2026

Exercise price $2.80 per share Options exercised October 28, 2026

Shares sold by Atay 8,333 shares October 28, 2026

Shares sold by spouse 2,667 shares October 28, 2026

Sale price $118 per share Atay's and his spouse's reported sales on October 28, 2026

Direct options following exercise 460,296 options Reported following the October 28, 2026 exercise

Spouse's shares following sale 146,501 shares Reported following the October 28, 2026 sale

Key Terms

Rule 10b5-1 trading plan, fully vested and exercisable, Stock Option (right to buy)

3 terms

Rule 10b5-1 trading plan regulatory

"effected pursuant to a Rule 10b5-1 trading plan"

A Rule 10b5-1 trading plan is a pre-arranged schedule that allows company insiders to buy or sell stock at specific times, even if they have inside information. It helps prevent accusations of unfair trading by making these transactions look planned and transparent, rather than sneaky or illegal.

fully vested and exercisable financial

"The options are fully vested and exercisable."

Stock Option (right to buy) financial

"Stock Option (right to buy)"

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

What BLLN shares did Chairman and CEO Oguzhan Atay report exercising and selling?

On October 28, 2026, Oguzhan Atay exercised options to acquire 8,333 shares of Class A Common Stock at $2.80 per share and sold 8,333 shares at $118 per share. His spouse separately sold 2,667 shares at $118 per share. Atay's common-stock acquisition and direct sale were under a Rule 10b5-1 trading plan adopted June 5, 2026; his spouse's sale was under a plan adopted June 7, 2026.

AI-generated analysis. How Rhea-AI works. Not financial advice.

Form 4 Insider Transactions: What Each Field Means →

See more from StockTitan in Google Search and AI answers. Adds StockTitan as a preferred source · opens Google

Add on Google Not now

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
Estimated average burden
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).

X

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^*

Atay Oguzhan

(Last) (First) (Middle)

C/O BILLIONTOONE, INC.

1035 O'BRIEN DRIVE

(Street)

MENLO PARK CALIFORNIA 94025

(City) (State) (Zip)

UNITED STATES

(Country)

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
X	Officer (give title below)		Other (specify below)
	Chairman and CEO

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
10/28/2026

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

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

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

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
Class A Common Stock	10/28/2026		M(1)		8,333	A	$2.8	8,333	D
Class A Common Stock	10/28/2026		S(1)		8,333	D	$118	0	D
Class A Common Stock	10/28/2026		S(2)		2,667	D	$118	146,501	I	By spouse(3)

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
Stock Option (right to buy)	$2.8	10/28/2026		M			8,333	(4)	06/07/2031	Class A Common Stock	8,333	$2.8	460,296	D

Explanation of Responses:

1. The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 5, 2026.

2. The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person's spouse on June 7, 2026.

3. Represents shares held by the Reporting Person's spouse.

4. The options are fully vested and exercisable.

Remarks:

	/s/ Thomas P. Lynch, Attorney-in-Fact	10/30/2026
	** 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.
* Form 4: SEC 1474 (03-26)