BillionToOne (NASDAQ: BLLN) CPO sells 8,000 shares under 10b5-1 plan

Q: What insider transactions did BLLN Chief Product Officer report on this Form 4?

The Chief Product Officer reported selling 8,000 shares of BillionToOne Class A Common Stock in open-market transactions and exercising stock options for 4,000 shares . These actions reflect both a share disposition and an acquisition through option exercise on the same date.

Q: At what prices did the BLLN insider sell and acquire shares?

The insider sold Class A Common Stock at $110.00 per share and acquired shares by exercising stock options at an exercise price of $8.65 per share . This combination reflects an exercise-and-sell pattern typical of equity compensation usage.

Q: What type of derivative security did the BLLN insider exercise?

The insider exercised a Stock Option (right to buy) covering 4,000 shares of Class A Common Stock at an exercise price of $8.65 per share . The options were fully vested and had an expiration date in 2033 according to the filing.

Filing Impact

(Very High)

Filing Sentiment

(Negative)

Form Type

Rhea-AI Filing Summary

BillionToOne, Inc. Chief Product Officer Sakakibara Shan Riku reported a mix of stock sales and an option exercise in Class A Common Stock. The insider sold a total of 8,000 shares in open-market transactions at $110.00 per share.

On the same date, the insider also exercised stock options to acquire 4,000 shares of Class A Common Stock at an exercise price of $8.65 per share. The filing notes these transactions were carried out under a pre-arranged Rule 10b5-1 trading plan, indicating they were scheduled in advance rather than timed discretionarily.

Insights

Pre-planned sales with a small option exercise look routine.

The Chief Product Officer of BillionToOne executed an exercise-and-sell pattern: exercising options for 4,000 shares at $8.65 per share and selling 8,000 shares of Class A Common Stock at $110.00 per share.

The filing states these trades were made under a Rule 10b5-1 trading plan adopted on March 6, 2026, suggesting the timing was predetermined rather than reactive to short-term news. The options exercised were fully vested and had an expiration date in 2033.

Because the transactions are pre-planned and combine an option exercise with open-market sales, they generally align with routine liquidity and compensation management. Subsequent filings may provide additional context on remaining equity and option holdings.

Insider Trade Summary 10b5-1

Exercise and sale activity reported; no spread calculated

Exercise and Sale 4 txns

Insider Sakakibara Shan Riku

Role Chief Product Officer

Sold 8,000 shs ($880K)

Approx. gross sale proceeds $880K

Approx. exercise cost $35K

Type	Security	Shares	Price	Value
Exercise	Stock Option (right to buy)	4,000	$8.65	$35K
Exercise	Class A Common Stock	4,000	$8.65	$35K
Sale	Class A Common Stock	4,000	$110.00	$440K
Sale	Class A Common Stock	4,000	$110.00	$440K

Holdings After Transaction: Stock Option (right to buy) — 36,000 shares (Direct); Class A Common Stock — 208,000 shares (Direct)

Footnotes (2)

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.
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: $110.00/share Options exercised: 4,000 shares +3 more

6 metrics

Shares sold 8,000 shares Class A Common Stock sold in open-market transactions

Sale price $110.00/share Price per share for Class A Common Stock sales

Options exercised 4,000 shares Shares acquired via stock option exercise

Exercise price $8.65/share Stock option exercise price for Class A Common Stock

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

Option expiration 2033-01-18 Expiration date of the exercised stock options

Key Terms

Rule 10b5-1 trading plan, Stock Option (right to buy), Exercise or conversion of derivative security, open-market sale, +1 more

5 terms

Rule 10b5-1 trading plan regulatory

"The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted..."

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)""

Exercise or conversion of derivative security financial

"transaction_code_description": "Exercise or conversion of derivative security""

open-market sale financial

"transaction_action": "open-market sale""

An open-market sale is when a shareholder sells existing shares directly on a public exchange to any willing buyer, rather than through a private deal. Think of it like putting goods on a busy market stall where price is set by supply and demand; for investors it matters because such sales increase available supply, can put short-term downward pressure on the stock price, and signal changes in liquidity or investor confidence.

Class A Common Stock financial

"security_title": "Class A Common Stock""

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.

FAQ

What insider transactions did BLLN Chief Product Officer report on this Form 4?

The Chief Product Officer reported selling 8,000 shares of BillionToOne Class A Common Stock in open-market transactions and exercising stock options for 4,000 shares. These actions reflect both a share disposition and an acquisition through option exercise on the same date.

At what prices did the BLLN insider sell and acquire shares?

The insider sold Class A Common Stock at $110.00 per share and acquired shares by exercising stock options at an exercise price of $8.65 per share. This combination reflects an exercise-and-sell pattern typical of equity compensation usage.

Were the BLLN insider’s transactions made under a Rule 10b5-1 plan?

Yes, the Form 4 states that the transactions were effected pursuant to a Rule 10b5-1 trading plan adopted on March 6, 2026. Such pre-arranged plans schedule trades in advance, reducing the significance of short-term timing decisions.

What type of derivative security did the BLLN insider exercise?

The insider exercised a Stock Option (right to buy) covering 4,000 shares of Class A Common Stock at an exercise price of $8.65 per share. The options were fully vested and had an expiration date in 2033 according to the filing.

How many BLLN shares did the insider sell in total in this filing?

According to the transaction summary, the insider sold a total of 8,000 shares of Class A Common Stock in open-market transactions coded as “S.” These sales are classified as non-derivative transactions and represent net selling activity in this Form 4.

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 06/26/2026 - 05:20 PM Accepted by SEC EDGAR 06/26/2026 - 05:20 PM

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^*

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)
06/24/2026

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	06/24/2026		M		4,000	A	$8.65	216,000	D
Class A Common Stock	06/24/2026		S⁽¹⁾		4,000	D	$110	212,000	D
Class A Common Stock	06/24/2026		S⁽¹⁾		4,000	D	$110	208,000	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)
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)	$8.65	06/24/2026		M			4,000	⁽²⁾	01/18/2033	Class A Common Stock	4,000	$8.65	36,000	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 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	06/26/2026
	** 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