BillionToOne (BLLN) CTO logs 20K share sale and option exercise under 10b5-1 plan

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Filing Sentiment

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Form Type

Rhea-AI Filing Summary

BillionToOne, Inc. director and Chief Technology Officer David Tsao reported a mix of stock sales and option exercises in Class A Common Stock. He completed open-market sales totaling 20,000 shares on June 15, 2026 at weighted average prices generally around $100–$104 per share, in multiple tranches.

On the same date, he exercised stock options to acquire 20,000 shares at an exercise price of $2.80 per share. After these transactions, Tsao directly holds 19,296 shares of Class A Common Stock and 630,000 stock options with a $2.80 exercise price expiring on June 7, 2031. The filing states the transactions were carried out under a pre-arranged Rule 10b5-1 trading plan adopted on March 6, 2026.

Insider Trade Summary 10b5-1

Net Seller: 20,000 shares ($2,045,326)

Net Sell 15 txns

Insider Tsao David

Role Chief Technology Officer

Sold 20,000 shs ($2.05M)

Type	Security	Shares	Price	Value
Exercise	Stock Option (right to buy)	10,000	$2.80	$28K
Exercise	Stock Option (right to buy)	10,000	$2.80	$28K
Exercise	Class A Common Stock	10,000	$2.80	$28K
Exercise	Class A Common Stock	10,000	$2.80	$28K
Sale	Class A Common Stock	1,704	$100.3718	$171K
Sale	Class A Common Stock	2,361	$101.5524	$240K
Sale	Class A Common Stock	2,816	$102.7739	$289K
Sale	Class A Common Stock	2,889	$103.6843	$300K
Sale	Class A Common Stock	230	$104.472	$24K
Sale	Class A Common Stock	600	$98.7417	$59K
Sale	Class A Common Stock	1,000	$100.053	$100K
Sale	Class A Common Stock	2,461	$101.3707	$249K
Sale	Class A Common Stock	2,978	$102.5988	$306K
Sale	Class A Common Stock	2,398	$103.6289	$249K
Sale	Class A Common Stock	563	$104.3167	$59K

Holdings After Transaction: Stock Option (right to buy) — 630,000 shares (Direct, null); Class A Common Stock — 11,000 shares (Direct, null)

Footnotes (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 $100.000 to $100.9175 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 $101.120 to $102.020 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 $102.185 to $103.150 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 $103.250 to $104.200 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. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $104.360 to $104.610 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 $98.160 to $99.080 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 $99.840 to $100.280 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 $100.860 to $101.800 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 $101.980 to $102.970 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 $103.140 to $104.130 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 $104.160 to $104.540 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: 20,000 shares Shares from option exercise: 20,000 shares Exercise price: $2.80 per share +4 more

7 metrics

Shares sold 20,000 shares Total Class A Common Stock sold on June 15, 2026

Shares from option exercise 20,000 shares Common shares acquired via option exercise on June 15, 2026

Exercise price $2.80 per share Stock option exercise price for 20,000 shares

Post-transaction share holdings 19,296 shares Direct Class A Common Stock held after transactions

Remaining stock options 630,000 options Stock options outstanding after transactions

Option expiration date June 7, 2031 Expiration for $2.80 stock options

Example sale price $100.0530 per share One tranche sale price for 1,000 shares

Key Terms

Rule 10b5-1 trading plan, weighted average price, Stock Option (right to buy), Class A Common Stock, +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 by the reporting person on March 6, 2026."

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)""

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.

derivative exercise/conversion financial

"transaction_action": "derivative exercise/conversion""

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Form 4 Insider Transactions: What Each Field Means →

06/17/2026 - 04:47 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^*

Tsao David

(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)
	Chief Technology Officer

2a. Foreign Trading Symbol

3. Date of Earliest Transaction (Month/Day/Year)
06/15/2026

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	06/15/2026		M⁽¹⁾		10,000	A	$2.8	11,000	D
Class A Common Stock	06/15/2026		M⁽¹⁾		10,000	A	$2.8	21,000	D
Class A Common Stock	06/15/2026		S⁽¹⁾		1,704	D	$100.3718⁽²⁾	19,296	D
Class A Common Stock	06/15/2026		S⁽¹⁾		2,361	D	$101.5524⁽³⁾	16,935	D
Class A Common Stock	06/15/2026		S⁽¹⁾		2,816	D	$102.7739⁽⁴⁾	14,119	D
Class A Common Stock	06/15/2026		S⁽¹⁾		2,889	D	$103.6843⁽⁵⁾	11,230	D
Class A Common Stock	06/15/2026		S⁽¹⁾		230	D	$104.472⁽⁶⁾	11,000	D
Class A Common Stock	06/15/2026		S⁽¹⁾		600	D	$98.7417⁽⁷⁾	10,400	D
Class A Common Stock	06/15/2026		S⁽¹⁾		1,000	D	$100.053⁽⁸⁾	9,400	D
Class A Common Stock	06/15/2026		S⁽¹⁾		2,461	D	$101.3707⁽⁹⁾	6,939	D
Class A Common Stock	06/15/2026		S⁽¹⁾		2,978	D	$102.5988⁽¹⁰⁾	3,961	D
Class A Common Stock	06/15/2026		S⁽¹⁾		2,398	D	$103.6289⁽¹¹⁾	1,563	D
Class A Common Stock	06/15/2026		S⁽¹⁾		563	D	$104.3167⁽¹²⁾	1,000	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)	$2.8	06/15/2026		M			10,000	⁽¹³⁾	06/07/2031	Class A Common Stock	10,000	$2.8	630,000	D
Stock Option (right to buy)	$2.8	06/15/2026		M			10,000	⁽¹³⁾	06/07/2031	Class A Common Stock	10,000	$2.8	620,000	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 $100.000 to $100.9175 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 $101.120 to $102.020 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 $102.185 to $103.150 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 $103.250 to $104.200 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 $104.360 to $104.610 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 $98.160 to $99.080 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 reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.840 to $100.280 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.

9. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.860 to $101.800 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.

10. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $101.980 to $102.970 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.

11. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $103.140 to $104.130 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.

12. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $104.160 to $104.540 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.

13. The options are fully vested and exercisable.

Remarks:

	/s/ Thomas P. Lynch, Attorney-in-Fact	06/17/2026
	** 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

FAQ

What did BillionToOne (BLLN) CTO David Tsao report in this Form 4?

David Tsao reported a combination of stock sales and option exercises. He sold 20,000 shares of Class A Common Stock and exercised options for 20,000 shares, updating his direct holdings and remaining option position in BillionToOne.

How many BillionToOne (BLLN) shares did David Tsao sell and at what prices?

David Tsao sold 20,000 shares of Class A Common Stock in multiple open-market transactions. Weighted average sale prices ranged roughly from about $98.74 to $104.61 per share, with detailed price ranges disclosed for each trade tranche in the Form 4 footnotes.

What options did BillionToOne (BLLN) CTO David Tsao exercise in this filing?

Tsao exercised stock options covering 20,000 shares of Class A Common Stock. The options carried an exercise price of $2.80 per share, converting derivative positions into common shares while leaving a substantial remaining option position outstanding after the transactions.

What are David Tsao’s BillionToOne (BLLN) holdings after these transactions?

Following the reported trades, David Tsao directly holds 19,296 shares of BillionToOne Class A Common Stock. He also holds 630,000 stock options with a $2.80 exercise price that remain outstanding and are scheduled to expire on June 7, 2031.

Were David Tsao’s BillionToOne (BLLN) stock sales pre-planned?

Yes. The Form 4 discloses that the reported transactions were executed under a Rule 10b5-1 trading plan. This plan was adopted on March 6, 2026, indicating the trades were pre-arranged rather than discretionary timing decisions in the open market.

What is the significance of the weighted average prices in the BLLN Form 4?

Each reported sale price represents a weighted average across multiple trades. The filing explains that individual transactions occurred within specified price ranges, and the holder will provide detailed trade-by-trade pricing information upon written request as noted in the footnotes.