BillionToOne CEO exercises options, sells shares

Q: How many BLLN shares did Oguzhan Atay acquire through option exercises?

Atay exercised options for 3,183 Class A common shares on October 14, 2026, and 5,150 shares on October 15, at an exercise price of $2.8000 per share.

Q: How many BLLN shares did Oguzhan Atay's spouse sell?

Atay's spouse sold 2,667 Class A common shares on October 14, 2026, at $98.0000 per share under a Rule 10b5-1 plan adopted June 7, 2026; the reported resulting holding was 149,168 shares.

Q: When do Atay's exercised BLLN options expire?

The reported options have an expiration date of June 7, 2031. The options are fully vested and exercisable.

The chairman and CEO's transactions and his spouse's sale were made under separate Rule 10b5-1 plans adopted June 5 and June 7, 2026, respectively.

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Form Type

Rhea-AI Filing Summary

BillionToOne, Inc. Chairman and CEO Oguzhan Atay exercised options for 3,183 Class A common shares on October 14, 2026, and 5,150 shares on October 15, at $2.8000 per share. He also reported multiple share sales on both dates, including 3,083 shares sold on October 14 at a weighted average price of $98.3198 per share. His spouse separately sold 2,667 shares at $98.0000 per share that day, with a reported resulting holding of 149,168 shares. Atay’s transactions were made under a Rule 10b5-1 trading plan adopted June 5, 2026; his spouse’s sale was under a separate plan adopted June 7, 2026.

Insights

Analyzing...

Insider Trade Summary 10b5-1

Exercise and sale activity reported; no spread calculated

Exercise and Sale 12 txns

Insider Atay Oguzhan

Role Chairman and CEO

Sold 11,000 shs ($1.09M)

Approx. gross sale proceeds $1.09M

Approx. exercise cost $23K

Type	Security	Shares	Price	Value
Exercise	Stock Option (right to buy) ^F10	5,150	$2.80	$14K
Exercise	Class A Common Stock ^F1	5,150	$2.80	$14K
Sale	Class A Common Stock ^{F1, F3}	900	$98.4328	$89K
Sale	Class A Common Stock ^{F1, F4}	1,861	$99.8438	$186K
Sale	Class A Common Stock ^{F1, F5}	1,276	$100.6029	$128K
Sale	Class A Common Stock ^{F1, F6}	980	$101.7871	$100K
Sale	Class A Common Stock ^{F1, F7}	133	$102.7766	$14K
Exercise	Stock Option (right to buy) ^F10	3,183	$2.80	$9K
Exercise	Class A Common Stock ^F1	3,183	$2.80	$9K
Sale	Class A Common Stock ^{F1, F2}	3,083	$98.3198	$303K
Sale	Class A Common Stock ^F1	100	$99.00	$10K
Sale	Class A Common Stock ^{F8, F9}	2,667	$98.00	$261K

Holdings After Transaction: Stock Option (right to buy) — 468,629 contracts (Direct); Class A Common Stock — 0 shares (Direct); Class A Common Stock — 149,168 shares (Indirect, By spouse)

Footnotes (10)

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.
F2. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.000 to $98.990 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F3. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.000 to $98.770 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F4. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.270 to $100.250 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F5. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.270 to $101.200 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F6. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $101.370 to $102.140 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F7. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $102.765 to $102.830 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.
F8. 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.
F9. Represents shares held by the Reporting Person's spouse.
F10. The options are fully vested and exercisable.

Key Figures

Options exercised: 3,183 shares Options exercised: 5,150 shares Exercise price: $2.8000 per share +3 more

6 metrics

Options exercised 3,183 shares October 14, 2026

Options exercised 5,150 shares October 15, 2026

Exercise price $2.8000 per share Options exercised October 14 and 15, 2026

Reported weighted average sale price $98.3198 per share 3,083 shares sold October 14, 2026

Spouse's sale 2,667 shares at $98.0000 per share October 14, 2026

Spouse's resulting holding 149,168 shares Following the October 14, 2026 transaction

Key Terms

Rule 10b5-1 trading plan, weighted average price, fully vested and exercisable

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.

weighted average price financial

"The reported price in Column 4 is a weighted average price"

Weighted average price is the average price of a security where each trade or component is counted according to its size, so bigger trades pull the average more than smaller ones. Think of it like calculating the average cost of a grocery haul where items you bought more of have greater influence on the final per-item cost. Investors use it to understand the true average price paid or received, judge execution quality, and compare trading performance against market movement.

fully vested and exercisable financial

"The options are fully vested and exercisable"

FAQ

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

How many BLLN shares did Oguzhan Atay acquire through option exercises?

Atay exercised options for 3,183 Class A common shares on October 14, 2026, and 5,150 shares on October 15, at an exercise price of $2.8000 per share.

How many BLLN shares did Oguzhan Atay's spouse sell?

Atay's spouse sold 2,667 Class A common shares on October 14, 2026, at $98.0000 per share under a Rule 10b5-1 plan adopted June 7, 2026; the reported resulting holding was 149,168 shares.

When do Atay's exercised BLLN options expire?

The reported options have an expiration date of June 7, 2031. The options are fully vested and exercisable.

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

Form 4 Insider Transactions: What Each Field Means →

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Available on EDGAR 10/16/2026 - 07:00 PM EDT Accepted by SEC EDGAR 10/16/2026 - 07:00 PM EDT

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).

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)
10/14/2026

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)
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)
Class A Common Stock	10/14/2026		M⁽¹⁾		3,183	A	$2.8	3,183	D
Class A Common Stock	10/14/2026		S⁽¹⁾		3,083	D	$98.3198⁽²⁾	100	D
Class A Common Stock	10/14/2026		S⁽¹⁾		100	D	$99	0	D
Class A Common Stock	10/15/2026		M⁽¹⁾		5,150	A	$2.8	5,150	D
Class A Common Stock	10/15/2026		S⁽¹⁾		900	D	$98.4328⁽³⁾	4,250	D
Class A Common Stock	10/15/2026		S⁽¹⁾		1,861	D	$99.8438⁽⁴⁾	2,389	D
Class A Common Stock	10/15/2026		S⁽¹⁾		1,276	D	$100.6029⁽⁵⁾	1,113	D
Class A Common Stock	10/15/2026		S⁽¹⁾		980	D	$101.7871⁽⁶⁾	133	D
Class A Common Stock	10/15/2026		S⁽¹⁾		133	D	$102.7766⁽⁷⁾	0	D
Class A Common Stock	10/14/2026		S⁽⁸⁾		2,667	D	$98	149,168	I	By spouse⁽⁹⁾

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)
Stock Option (right to buy)	$2.8	10/14/2026		M			3,183	⁽¹⁰⁾	06/07/2031	Class A Common Stock	3,183	$2.8	473,779	D
Stock Option (right to buy)	$2.8	10/15/2026		M			5,150	⁽¹⁰⁾	06/07/2031	Class A Common Stock	5,150	$2.8	468,629	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 reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.000 to $98.990 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

3. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.000 to $98.770 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

4. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.270 to $100.250 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

5. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.270 to $101.200 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

6. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $101.370 to $102.140 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

7. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $102.765 to $102.830 per share, inclusive. The holder undertakes to provide, upon written request, full information regarding the number of shares sold at each separate price within the range set forth in this footnote.

8. 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.

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

10. The options are fully vested and exercisable.

Remarks:

	/s/ Thomas P. Lynch, Attorney-in-Fact	10/16/2026
	** 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)

Source: View Original Filing on SEC EDGAR