BillionToOne (BLLN) CPO sells 4,000 shares under Rule 10b5-1 plan

Rhea-AI Filing Summary

BillionToOne, Inc. Chief Product Officer Sakakibara Shan Riku sold 4,000 shares of Class A Common Stock on July 31, 2026 at $140.21 per share. Following this open-market sale, the executive directly holds 200,000 shares, with the transaction effected under a Rule 10b5-1 trading plan adopted March 6, 2026.

Insider Trade Summary 10b5-1

Net Seller: 4,000 shares

Net Sell 1 txn

Insider Sakakibara Shan Riku

Role Chief Product Officer

Sold 4,000 shs ($561K)

Type	Security	Shares	Price	Value
Sale	Class A Common Stock F1	4,000	$140.21	$561K

Holdings After Transaction: Class A Common Stock — 200,000 shares (Direct)

Footnotes (1)

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.

Key Figures

Shares sold: 4,000 shares Sale price per share: $140.21 Shares held after transaction: 200,000 shares +2 more

5 metrics

Shares sold 4,000 shares Class A Common Stock sold on July 31, 2026

Sale price per share $140.21 Price per share for the 4,000 shares sold

Shares held after transaction 200,000 shares Directly owned Class A Common Stock following the sale

Net shares sold in filing 4,000 shares Net-sell direction as reported in transaction summary

10b5-1 plan adoption date March 6, 2026 Date the Rule 10b5-1 trading plan was adopted

Key Terms

Rule 10b5-1 trading plan, Class A Common Stock, Sale in open market or private transaction

3 terms

Rule 10b5-1 trading plan financial

"were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person"

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.

Class A Common Stock financial

"security_title: Class A Common Stock for the reported sale transaction"

Class A common stock is a category of a company’s shares that carries a specific set of ownership rights—most commonly defined voting power and claims on dividends—set out in the company’s charter. For investors it matters because the class determines how much influence you have over corporate decisions, the share’s likely dividend and trading behavior, and how it compares in value to other share classes, like choosing a particular seat with different privileges at the company’s decision-making table.

Sale in open market or private transaction financial

"transaction_code_description: Sale in open market or private transaction"

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

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Form 4 Insider Transactions: What Each Field Means →

Available on EDGAR 08/04/2026 - 04:33 PM Accepted by SEC EDGAR 08/04/2026 - 04:32 PM Learn about SEC filing dates

FAQ

What insider transaction did BLLN disclose for July 31, 2026?

BillionToOne, Inc. (BLLN) disclosed that Chief Product Officer Sakakibara Shan Riku sold 4,000 shares of Class A Common Stock on July 31, 2026 at $140.21 per share in a direct ownership transaction under a Rule 10b5-1 trading plan.

Who is Sakakibara Shan Riku in relation to BillionToOne (BLLN)?

Sakakibara Shan Riku is the Chief Product Officer of BillionToOne, Inc. (BLLN) and is an officer but not a director or 10% owner, as reflected in the Form 4 insider transaction report for the reported stock sale.

How many BLLN shares does the insider hold after the reported sale?

After selling 4,000 shares, Chief Product Officer Sakakibara Shan Riku directly holds 200,000 shares of BillionToOne, Inc. (BLLN) Class A Common Stock, as stated in the post-transaction ownership column of the Form 4 filing.

Was the BLLN insider stock sale made under a Rule 10b5-1 plan?

Yes. The Form 4 for BillionToOne, Inc. (BLLN) states that the reported transactions were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on March 6, 2026, and the 10b5-1 checkbox is marked.

Is the BLLN Form 4 transaction a purchase or a sale?

The Form 4 for BillionToOne, Inc. (BLLN) reports a sale transaction. The insider disposed of 4,000 shares of Class A Common Stock, coded as a sale in an open market or private transaction, with no purchases reported in this filing.

What price was received per share in the BLLN insider sale?

The BillionToOne, Inc. (BLLN) Form 4 reports that the 4,000 shares of Class A Common Stock were sold at a price of $140.21 per share, with the price identified as a per-share transaction value in the filing data.

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)
07/31/2026

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	07/31/2026		S(1)		4,000	D	$140.21	200,000	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

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.

Remarks:

	/s/ Thomas P. Lynch, Attorney-in-Fact	08/04/2026
	** 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)