BillionToOne CPO trades stock under 10b5-1 plan

Rhea-AI Filing Summary

BillionToOne, Inc. Chief Product Officer Shan Riku Sakakibara reported open‑market sales of Class A Common Stock totaling 8,000 shares at $125.00 per share on July 9, 2026. On the same date, Sakakibara exercised stock options for 4,000 shares of Class A Common Stock at exercise prices of $30.78 and $8.65 per share. The company notes these trades were effected under a Rule 10b5‑1 trading plan and that the options exercised were fully vested and exercisable.

Filing Explained

The July 9 plan-based trades changed the CPO’s disclosed holdings: options were exercised, shares were sold, and 204,000 direct shares remained.

This July 13 Form 4 reports that BillionToOne’s Chief Product Officer exercised stock options and sold Class A common stock on July 9; the disclosed direct holding after the reported transactions was 204,000 shares.

The filing identifies the option exercises with transaction code M and the sales with code S; the supplied Form 4 definitions map those codes to option or derivative exercise and open-market sale.

The reported exercise prices were $8.65 and $30.78, while each reported sale price was $125.

The filing states that the transactions were effected under a Rule 10b5-1 plan adopted on March 6, 2026; such a plan is written in advance and executes trades under a schedule or formula.

The direct-share column reports 208,174 after one exercise, 212,000 after the listed exercises, and 204,000 after the listed sales.

The derivative table shows remaining option holdings of 35,826, 63,883, 62,528, and 61,174, with expiration dates of January 18, 2033 or September 30, 2035; the filing describes the options as fully vested and exercisable.

Insider Trade Summary 10b5-1

Exercise and sale activity reported; no spread calculated

Exercise and Sale 13 txns

Insider Sakakibara Shan Riku

Role Chief Product Officer

Sold 8,000 shs ($1.00M)

Approx. gross sale proceeds $1.00M

Approx. exercise cost $119K

Type	Security	Shares	Price	Value
Exercise	Stock Option (right to buy) F2	174	$8.65	$2K
Exercise	Stock Option (right to buy) F2	1,117	$30.78	$34K
Exercise	Stock Option (right to buy) F2	1,355	$30.78	$42K
Exercise	Stock Option (right to buy) F2	1,354	$30.78	$42K
Exercise	Class A Common Stock F1	174	$8.65	$2K
Exercise	Class A Common Stock F1	1,117	$30.78	$34K
Exercise	Class A Common Stock F1	1,355	$30.78	$42K
Exercise	Class A Common Stock F1	1,354	$30.78	$42K
Sale	Class A Common Stock F1	4,000	$125.00	$500K
Sale	Class A Common Stock F1	174	$125.00	$22K
Sale	Class A Common Stock F1	1,117	$125.00	$140K
Sale	Class A Common Stock F1	1,355	$125.00	$169K
Sale	Class A Common Stock F1	1,354	$125.00	$169K

Holdings After Transaction: Stock Option (right to buy) — 97,000 shares (Direct); Class A Common Stock — 204,000 shares (Direct)

Footnotes (2)

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 March 6, 2026.
2. F2. The options are fully vested and exercisable. The terms of the underlying option grant are as previously reported on the Reporting Person's Form 3 filed on November 5, 2025.

Key Figures

Shares sold: 8,000 shares Sale price: $125.00 per share Options exercised: 4,000 shares +4 more

7 metrics

Shares sold 8,000 shares Total Class A Common Stock sold in open-market transactions on July 9, 2026

Sale price $125.00 per share Price for each reported Class A Common Stock sale transaction

Options exercised 4,000 shares Total Class A shares underlying options exercised on July 9, 2026

Option exercise price $30.78 per share Exercise price for several Stock Option (right to buy) tranches

Lower exercise price $8.65 per share Exercise price for one Stock Option (right to buy) tranche

Exercise transactions 4 exercises Number of derivative exercises (M code) reported in transaction summary

Net share change (buy/sell) -8,000 shares Net buy/sell shares across reported non-derivative transactions

Key Terms

Rule 10b5-1 trading plan, Stock Option (right to buy), derivative security, 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.

Stock Option (right to buy) financial

"security_title: Stock Option (right to buy) ... underlying security: Class A"

derivative security financial

"transaction_code_description: Exercise or conversion of derivative security"

A derivative security is a financial contract whose value comes from the price or performance of something else, such as a stock, bond, commodity, or market index. For investors it acts like an insurance policy or a wager: it can be used to protect against losses, lock in prices, or amplify gains and losses, so it can change a portfolio’s risk and potential return without owning the underlying asset directly.

fully vested and exercisable financial

"The options are fully vested and exercisable. The terms of the underlying"

FAQ

What insider transactions did BLLN’s Chief Product Officer report on July 9, 2026?

The Chief Product Officer reported selling 8,000 Class A shares at $125.00 and exercising options for 4,000 shares at $30.78 and $8.65 per share, all on July 9, 2026.

Were the BLLN insider stock sales by Shan Riku Sakakibara pre-planned?

Yes. The filing states the transactions were effected under a Rule 10b5‑1 trading plan adopted on March 6, 2026, indicating the trades were pre‑scheduled rather than discretionary market‑timing decisions.

How many BLLN shares did the Chief Product Officer sell and at what price?

Sakakibara sold a total of 8,000 shares of BillionToOne Class A Common Stock at an average price of $125.00 per share, through multiple open‑market sale transactions reported for July 9, 2026.

What stock options did the BLLN insider exercise in this Form 4?

The insider exercised options covering 4,000 shares of Class A Common Stock, including tranches at a $30.78 exercise price and a tranche at $8.65 per share. The filing notes these options were fully vested and exercisable.

What does the Rule 10b5-1 plan mean for these BLLN insider trades?

The filing explains the trades occurred under a Rule 10b5‑1 trading plan, meaning quantities and timing were set in advance on March 6, 2026, reducing the significance of short‑term market conditions in interpreting these transactions.

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

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^*

Sakakibara Shan Riku

(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)

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

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)		174	A	$8.65	208,174	D
Class A Common Stock	07/09/2026		M(1)		1,117	A	$30.78	209,291	D
Class A Common Stock	07/09/2026		M(1)		1,355	A	$30.78	210,646	D
Class A Common Stock	07/09/2026		M(1)		1,354	A	$30.78	212,000	D
Class A Common Stock	07/09/2026		S(1)		4,000	D	$125	208,000	D
Class A Common Stock	07/09/2026		S(1)		174	D	$125	207,826	D
Class A Common Stock	07/09/2026		S(1)		1,117	D	$125	206,709	D
Class A Common Stock	07/09/2026		S(1)		1,355	D	$125	205,354	D
Class A Common Stock	07/09/2026		S(1)		1,354	D	$125	204,000	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)	$8.65	07/09/2026		M			174	(2)	01/18/2033	Class A Common Stock	174	$8.65	35,826	D
Stock Option (right to buy)	$30.78	07/09/2026		M			1,117	(2)	09/30/2035	Class A Common Stock	1,117	$30.78	63,883	D
Stock Option (right to buy)	$30.78	07/09/2026		M			1,355	(2)	09/30/2035	Class A Common Stock	1,355	$30.78	62,528	D
Stock Option (right to buy)	$30.78	07/09/2026		M			1,354	(2)	09/30/2035	Class A Common Stock	1,354	$30.78	61,174	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 options are fully vested and exercisable. The terms of the underlying option grant are as previously reported on the Reporting Person's Form 3 filed on November 5, 2025.

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)