BillionToOne CTO David Tsao sells 20,000 shares

Q: What were the terms of David Tsao's BLLN option exercise?

He exercised options for 20,000 Class A shares at $2.80 per share on November 2, 2026. The options were fully vested and exercisable, with an expiration date of June 7, 2031.

The chief technology officer's options were fully vested and exercisable; the transactions were effected pursuant to a Rule 10b5-1 plan adopted June 5, 2026.

Available on EDGAR 11/04/2026 - 08:42 PM EST Accepted by SEC EDGAR 11/04/2026 - 08:42 PM EST

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Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) Chief Technology Officer and director David Tsao exercised options for 20,000 Class A shares at $2.80 per share on November 2, 2026, and sold 20,000 shares that day. The transactions were effected pursuant to a Rule 10b5-1 trading plan adopted June 5, 2026; the options were fully vested and exercisable.

Insider Trade Summary 10b5-1

Exercise and Sale: 20,000 shares ($2.13M approx. pre-tax spread)

Exercise and Sale 18 txns

Insider Tsao David

Role Chief Technology Officer

Sold 20,000 shs ($2.18M)

Approx. gross sale proceeds $2.18M

Approx. exercise cost $56K

Approx. pre-tax spread $2.13M

Type	Security	Shares	Price	Value
Exercise	Stock Option (right to buy) ^F14	10,000	$2.80	$28K
Exercise	Stock Option (right to buy) ^F14	10,000	$2.80	$28K
Exercise	Class A Common Stock ^F1	10,000	$2.80	$28K
Exercise	Class A Common Stock ^F1	10,000	$2.80	$28K
Sale	Class A Common Stock ^{F1, F2}	917	$107.3129	$98K
Sale	Class A Common Stock ^{F1, F3}	2,320	$108.2354	$251K
Sale	Class A Common Stock ^{F1, F4}	3,241	$109.0441	$353K
Sale	Class A Common Stock ^{F1, F5}	1,992	$110.129	$219K
Sale	Class A Common Stock ^{F1, F6}	1,130	$110.7704	$125K
Sale	Class A Common Stock ^{F1, F7}	300	$112.19	$34K
Sale	Class A Common Stock ^F1	100	$113.165	$11K
Sale	Class A Common Stock ^{F1, F8}	1,063	$107.3322	$114K
Sale	Class A Common Stock ^{F1, F9}	2,450	$108.3851	$266K
Sale	Class A Common Stock ^{F1, F10}	3,234	$109.1527	$353K
Sale	Class A Common Stock ^{F1, F11}	2,389	$110.3056	$264K
Sale	Class A Common Stock ^{F1, F12}	633	$111.1379	$70K
Sale	Class A Common Stock ^{F1, F13}	208	$112.0125	$23K
Sale	Class A Common Stock ^F1	23	$113.165	$3K

Holdings After Transaction: Stock Option (right to buy) — 516,667 contracts (Direct); Class A Common Stock — 1,000 shares (Direct)

Footnotes (14)

F1. The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person on June 5, 2026.
F2. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $106.620 to $107.595 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.
F3. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $107.635 to $108.610 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.
F4. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $108.650 to $109.640 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.
F5. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $109.650 to $110.640 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.
F6. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $110.650 to $111.320 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.
F7. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $111.950 to $112.370 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.
F8. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $106.750 to $107.635 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.
F9. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $107.785 to $108.750 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.
F10. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $108.790 to $109.775 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.
F11. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $109.800 to $110.785 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.
F12. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $110.840 to $111.730 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.
F13. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $111.950 to $112.080 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.
F14. The options are fully vested and exercisable.

Key Figures

Options exercised: 20,000 Class A shares Exercise price: $2.80 per share Shares sold: 20,000 Class A shares +2 more

5 metrics

Options exercised 20,000 Class A shares November 2, 2026

Exercise price $2.80 per share Options exercised November 2, 2026

Shares sold 20,000 Class A shares November 2, 2026

Option expiration June 7, 2031 Expiration date stated for the options

Rule 10b5-1 plan adoption June 5, 2026 Adoption date of the plan for the reported transactions

Key Terms

Rule 10b5-1 trading plan, weighted average price, fully vested and exercisable

3 terms

Rule 10b5-1 trading plan regulatory

"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.

fully vested and exercisable technical

"The options are fully vested and exercisable."

FAQ

AI-generated questions and answers. How Rhea-AI works. Not financial advice.

How many BLLN shares did David Tsao sell?

David Tsao, BillionToOne's chief technology officer and a director, reported sales totaling 20,000 Class A shares on November 2, 2026. The transaction rows show per-share prices from $107.3129 to $113.1650; footnotes identify several prices as weighted averages for sales within separately stated ranges.

What were the terms of David Tsao's BLLN option exercise?

He exercised options for 20,000 Class A shares at $2.80 per share on November 2, 2026. The options were fully vested and exercisable, with an expiration date of June 7, 2031.

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

Form 4 Insider Transactions: What Each Field Means →

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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)
11/02/2026

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	11/02/2026		M⁽¹⁾		10,000	A	$2.8	11,000	D
Class A Common Stock	11/02/2026		M⁽¹⁾		10,000	A	$2.8	21,000	D
Class A Common Stock	11/02/2026		S⁽¹⁾		917	D	$107.3129⁽²⁾	20,083	D
Class A Common Stock	11/02/2026		S⁽¹⁾		2,320	D	$108.2354⁽³⁾	17,763	D
Class A Common Stock	11/02/2026		S⁽¹⁾		3,241	D	$109.0441⁽⁴⁾	14,522	D
Class A Common Stock	11/02/2026		S⁽¹⁾		1,992	D	$110.129⁽⁵⁾	12,530	D
Class A Common Stock	11/02/2026		S⁽¹⁾		1,130	D	$110.7704⁽⁶⁾	11,400	D
Class A Common Stock	11/02/2026		S⁽¹⁾		300	D	$112.19⁽⁷⁾	11,100	D
Class A Common Stock	11/02/2026		S⁽¹⁾		100	D	$113.165	11,000	D
Class A Common Stock	11/02/2026		S⁽¹⁾		1,063	D	$107.3322⁽⁸⁾	9,937	D
Class A Common Stock	11/02/2026		S⁽¹⁾		2,450	D	$108.3851⁽⁹⁾	7,487	D
Class A Common Stock	11/02/2026		S⁽¹⁾		3,234	D	$109.1527⁽¹⁰⁾	4,253	D
Class A Common Stock	11/02/2026		S⁽¹⁾		2,389	D	$110.3056⁽¹¹⁾	1,864	D
Class A Common Stock	11/02/2026		S⁽¹⁾		633	D	$111.1379⁽¹²⁾	1,231	D
Class A Common Stock	11/02/2026		S⁽¹⁾		208	D	$112.0125⁽¹³⁾	1,023	D
Class A Common Stock	11/02/2026		S⁽¹⁾		23	D	$113.165	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	11/02/2026		M			10,000	⁽¹⁴⁾	06/07/2031	Class A Common Stock	10,000	$2.8	526,667	D
Stock Option (right to buy)	$2.8	11/02/2026		M			10,000	⁽¹⁴⁾	06/07/2031	Class A Common Stock	10,000	$2.8	516,667	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 June 5, 2026.

2. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $106.620 to $107.595 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 $107.635 to $108.610 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.

4. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $108.650 to $109.640 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 $109.650 to $110.640 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 $110.650 to $111.320 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 $111.950 to $112.370 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 $106.750 to $107.635 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 $107.785 to $108.750 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 $108.790 to $109.775 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 $109.800 to $110.785 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 $110.840 to $111.730 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 reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $111.950 to $112.080 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.

14. The options are fully vested and exercisable.

Remarks:

	/s/ Thomas P. Lynch, Attorney-in-Fact	11/04/2026
	** 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)

Source: View Original Filing on SEC EDGAR