BillionToOne (NASDAQ: BLLN) CEO exercises options, sells 12,500 shares under 10b5-1 plan

Rhea-AI Filing Summary

BillionToOne, Inc. Chairman and CEO Atay Oguzhan exercised options to acquire 12,500 shares of Class A Common Stock at $2.80 per share and on the same date executed open-market sales of 12,500 shares in multiple transactions at weighted average prices between $125.00 and $128.295 per share. Following these trades, he held no shares of Class A Common Stock directly but continued to hold 575,000 stock options. The transactions were carried out under a Rule 10b5-1 trading plan, and the options are reported as fully vested and exercisable.

Filing Explained

The disclosed effect is on the CEO’s holdings: direct Class A ownership is 0 after the July 9 transactions, while 575,000 options remain.

The July 13, 2026 Form 4 reports transactions by BillionToOne Chairman and CEO Atay Oguzhan dated July 9, 2026: an option exercise of 12,500 shares at $2.8 and four reported sales of 7,489, 2,002, 2,657, and 352 Class A shares.

The disclosed ownership consequence is that his direct Class A holdings are shown as 0 after the transactions, while the filing reports 575,000 options remaining.

Under the supplied Form 4 definitions, code M identifies an option or derivative exercise and code S identifies an open-market sale.

The filing states that the transactions were made under a Rule 10b5-1 plan adopted on March 6, 2026; that type of plan is adopted in advance to execute trades on a schedule or formula, and its disclosure gives the adoption date rather than reasons for individual trades.

The reported sale prices are weighted averages: $125.4264, $126.4839, $127.4366, and $128.2318, with the filing providing a separate price range for each sale.

The filing also states that the remaining options are fully vested and exercisable and expire on June 7, 2031.

Insider Trade Summary 10b5-1

Net Seller: 12,500 shares ($1,576,276)

Net Sell 6 txns

Insider Atay Oguzhan

Role Chairman and CEO

Sold 12,500 shs ($1.58M)

Type	Security	Shares	Price	Value
Exercise	Stock Option (right to buy)	12,500	$2.80	$35K
Exercise	Class A Common Stock	12,500	$2.80	$35K
Sale	Class A Common Stock	7,489	$125.4264	$939K
Sale	Class A Common Stock	2,002	$126.4839	$253K
Sale	Class A Common Stock	2,657	$127.4366	$339K
Sale	Class A Common Stock	352	$128.2318	$45K

Holdings After Transaction: Stock Option (right to buy) — 575,000 shares (Direct); Class A Common Stock — 12,500 shares (Direct)

Footnotes (1)

1. The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 6, 2026. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $125.000 to $125.910 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. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $126.085 to $127.040 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. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $127.100 to $128.060 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. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $128.180 to $128.295 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. The options are fully vested and exercisable.

Key Figures

Shares sold: 12,500 shares Sale prices (weighted averages): $125.4264, $126.4839, $127.4366, $128.2318 per share Option exercise price: $2.80 per share +4 more

7 metrics

Shares sold 12,500 shares Total Class A Common Stock sold in open-market transactions on July 9, 2026

Sale prices (weighted averages) $125.4264, $126.4839, $127.4366, $128.2318 per share Weighted average prices for four sale tranches of Class A Common Stock

Option exercise price $2.80 per share Exercise price for 12,500 stock options converted into Class A Common Stock

Options exercised 12,500 options Stock options exercised into Class A Common Stock on July 9, 2026

Options remaining 575,000 options Stock options (right to buy Class A Common Stock) held after the reported transactions

Option expiration date June 7, 2031 Expiration date of the reported stock option grant

Post-transaction common stock 0 shares Directly held Class A Common Stock after all sales on July 9, 2026

Key Terms

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

4 terms

Rule 10b5-1 trading plan regulatory

"The transactions reported ... were 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.

Stock Option (right to buy) financial

"security_title: "Stock Option (right to buy)" for the derivative transaction."

fully vested and exercisable financial

"The options are fully vested and exercisable."

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 07/13/2026 - 04:40 PM Accepted by SEC EDGAR 07/13/2026 - 04:39 PM Learn about SEC filing dates

FAQ

What did BLLN Chairman and CEO Atay Oguzhan report in this Form 4?

Atay Oguzhan reported exercising options for 12,500 shares of BillionToOne Class A Common Stock at $2.80 per share and selling all 12,500 shares in open-market transactions on July 9, 2026.

How many BillionToOne (BLLN) shares did the CEO sell and at what prices?

The CEO sold 12,500 shares of BillionToOne Class A Common Stock in multiple trades at weighted average prices of $125.4264, $126.4839, $127.4366, and $128.2318 per share, within price ranges from $125.00 to $128.295.

Does the BillionToOne (BLLN) CEO still hold common stock after these transactions?

After the reported transactions, Atay Oguzhan held 0 shares of BillionToOne Class A Common Stock directly, according to the post-transaction holdings shown for the non-derivative securities on the transaction date.

What derivative holdings does the BillionToOne (BLLN) CEO retain after this Form 4?

Following the exercise, Atay Oguzhan retained 575,000 stock options (rights to buy Class A Common Stock) with an exercise price of $2.80 per share and an expiration date of June 7, 2031.

Were the BLLN CEO’s share sales under a Rule 10b5-1 trading plan?

Yes. A footnote states the transactions were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 6, 2026, indicating the sales were pre-arranged rather than discretionary trades.

Why are the reported BLLN sale prices described as weighted averages?

Footnotes explain each reported sale price is a weighted average price for multiple trades. Individual trades occurred within specified ranges, and the holder undertakes to provide full price breakdowns upon written request.

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)
07/09/2026

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	07/09/2026		M(1)		12,500	A	$2.8	12,500	D
Class A Common Stock	07/09/2026		S(1)		7,489	D	$125.4264(2)	5,011	D
Class A Common Stock	07/09/2026		S(1)		2,002	D	$126.4839(3)	3,009	D
Class A Common Stock	07/09/2026		S(1)		2,657	D	$127.4366(4)	352	D
Class A Common Stock	07/09/2026		S(1)		352	D	$128.2318(5)	0	D

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	07/09/2026		M			12,500	(6)	06/07/2031	Class A Common Stock	12,500	$2.8	575,000	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 March 6, 2026.

2. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $125.000 to $125.910 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 $126.085 to $127.040 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 $127.100 to $128.060 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 $128.180 to $128.295 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 options are fully vested and exercisable.

Remarks:

	/s/ Thomas P. Lynch, Attorney-in-Fact	07/13/2026
	** 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)