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  4. [Form 4] BillionToOne, Inc. Insider Trading Activity

BillionToOne CEO sells 30,331 shares in plan

BillionToOne’s CEO exercised vested options and sold shares in open-market trades executed under pre-arranged Rule 10b5-1 plans.

Filing Impact
(Very High)
Filing Sentiment
(Negative)
Form Type
4

Rhea-AI Filing Summary

BillionToOne, Inc. (BLLN) reports that Chairman and CEO Atay Oguzhan exercised stock options covering 24,999 shares of Class A Common Stock at an exercise price of $2.80 per share on September 14, 2026, and that he sold 30,331 shares of Class A Common Stock in multiple transactions that day.

The company states that these sales, including sales of shares held by his spouse, occurred at weighted average prices generally between $98.060 and $101.820 per share, were effected in open-market transactions pursuant to Rule 10b5-1 trading plans adopted on June 5, 2026 and June 7, 2026, and involved fully vested stock options expiring on June 7, 2031.

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Insider Atay Oguzhan
Role Chairman and CEO
Sold 30,331 shs ($3.03M)
Approx. gross sale proceeds $3.03M
Approx. exercise cost $70K
Type Security Shares Price Value
Exercise Stock Option (right to buy) F12 16,666 $2.80 $47K
Exercise Stock Option (right to buy) F12 8,333 $2.80 $23K
Exercise Class A Common Stock F1 16,666 $2.80 $47K
Exercise Class A Common Stock F1 8,333 $2.80 $23K
Sale Class A Common Stock F1, F2 4,465 $98.6314 $440K
Sale Class A Common Stock F1, F3 2,456 $99.5713 $245K
Sale Class A Common Stock F1, F4 2,531 $100.5809 $255K
Sale Class A Common Stock F1, F5 7,214 $101.4407 $732K
Sale Class A Common Stock F1, F6 1,680 $98.6358 $166K
Sale Class A Common Stock F1, F7 1,500 $99.5683 $149K
Sale Class A Common Stock F1, F8 2,010 $100.7756 $203K
Sale Class A Common Stock F1, F9 3,143 $101.4919 $319K
Sale Class A Common Stock F10, F11 2,666 $98.00 $261K
Sale Class A Common Stock F10, F11 2,666 $98.00 $261K
Holdings After Transaction: Stock Option (right to buy) — 501,962 contracts (Direct); Class A Common Stock — 0 shares (Direct); Class A Common Stock — 157,168 shares (Indirect, By spouse)
Footnotes (12)
  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 June 5, 2026.
  2. F2. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.060 to $99.055 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. F3. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.060 to $100.055 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. F4. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.060 to $101.040 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. F5. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $101.085 to $101.805 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. F6. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $98.140 to $99.010 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. F7. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $99.160 to $100.130 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.
  8. F8. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.230 to $101.200 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.
  9. F9. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $101.250 to $101.820 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. F10. The transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person's spouse on June 7, 2026.
  11. F11. Represents shares held by the Reporting Person's spouse.
  12. F12. The options are fully vested and exercisable.
Options exercised 24,999 shares Stock options exercised into Class A Common Stock on September 14, 2026
Option exercise price $2.80 per share Exercise price for the stock options converted into Class A Common Stock
Shares sold 30,331 shares Class A Common Stock sold in open-market transactions on September 14, 2026
Overall sale price range $98.060–$101.820 per share Weighted average sale price ranges disclosed for the September 14, 2026 transactions
Spouse sales 5,332 shares Class A Common Stock sold by the CEO’s spouse at $98.00 per share on September 14, 2026
Option expiration date June 7, 2031 Expiration date of the fully vested stock options that were exercised
Rule 10b5-1 trading plan regulatory
"transactions reported on this Form 4 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.
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.
Class A Common Stock financial
"underlying security title is 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.
Stock Option financial
"Stock Option (right to buy) reported as a derivative security"
A stock option is a contract that gives you the right to buy or sell a company's stock at a specific price within a certain time frame. People use them to potentially make money if the stock's price moves favorably or to protect against losses. It's like holding a coupon that can be used to buy or sell stock at a set price later on.

FAQ

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

What did BLLN’s CEO do on September 14, 2026 according to this Form 4?
On September 14, 2026, BillionToOne CEO Atay Oguzhan exercised options for 24,999 shares of Class A Common Stock at $2.80 per share and sold 30,331 shares of Class A Common Stock in multiple open-market transactions.

How many BillionToOne (BLLN) shares were sold and at what prices?
The filing reports 30,331 shares of Class A Common Stock sold on September 14, 2026 at weighted average prices within disclosed ranges, which overall span from about $98.060 to $101.820 per share across the different sale groupings.

What stock options did the BLLN CEO exercise in this Form 4?
Atay Oguzhan exercised fully vested stock options covering 24,999 shares of Class A Common Stock at an exercise price of $2.80 per share. The options are disclosed as fully vested and exercisable and have an expiration date of June 7, 2031.

Were the BLLN insider transactions made under a Rule 10b5-1 plan?
Yes. The company states that the CEO’s transactions were effected under a Rule 10b5-1 trading plan adopted on June 5, 2026, and that the spouse’s transactions were effected under a Rule 10b5-1 trading plan adopted on June 7, 2026.

What transactions in BLLN stock involved the CEO’s spouse?
The filing shows the CEO’s spouse indirectly sold 5,332 shares of Class A Common Stock (two blocks of 2,666 shares) at a reported price of $98.00 per share, held in the spouse’s name and executed under a separate Rule 10b5-1 trading plan.

Did the Form 4 disclose the nature of prices as weighted averages for BLLN sales?
Yes. Several sale entries state that the reported prices are weighted average prices, with underlying trades executed in ranges such as $98.060 to $99.055 per share and up to $101.250 to $101.820 per share, with full breakdowns available on request.

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 4UNITED 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*
Atay Oguzhan
(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)
XDirector10% Owner
XOfficer (give title below)Other (specify below)
Chairman and CEO
2a. Foreign Trading Symbol
3. Date of Earliest Transaction (Month/Day/Year)
09/14/2026		6. Individual or Joint/Group Filing (Check Applicable Line)
XForm 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)
CodeVAmount(A) or (D)Price
Class A Common Stock09/14/2026M(1)16,666A$2.816,666D
Class A Common Stock09/14/2026M(1)8,333A$2.824,999D
Class A Common Stock09/14/2026S(1)4,465D$98.6314(2)20,534D
Class A Common Stock09/14/2026S(1)2,456D$99.5713(3)18,078D
Class A Common Stock09/14/2026S(1)2,531D$100.5809(4)15,547D
Class A Common Stock09/14/2026S(1)7,214D$101.4407(5)8,333D
Class A Common Stock09/14/2026S(1)1,680D$98.6358(6)6,653D
Class A Common Stock09/14/2026S(1)1,500D$99.5683(7)5,153D
Class A Common Stock09/14/2026S(1)2,010D$100.7756(8)3,143D
Class A Common Stock09/14/2026S(1)3,143D$101.4919(9)0D
Class A Common Stock09/14/2026S(10)2,666D$98159,834IBy spouse(11)
Class A Common Stock09/14/2026S(10)2,666D$98157,168IBy spouse(11)
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)
CodeV(A)(D)Date ExercisableExpiration DateTitleAmount or Number of Shares
Stock Option (right to buy)$2.809/14/2026M16,666 (12)06/07/2031Class A Common Stock16,666$2.8510,295D
Stock Option (right to buy)$2.809/14/2026M8,333 (12)06/07/2031Class A Common Stock8,333$2.8501,962D
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 $98.060 to $99.055 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 $99.060 to $100.055 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 $100.060 to $101.040 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 $101.085 to $101.805 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 $98.140 to $99.010 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 $99.160 to $100.130 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.
8. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $100.230 to $101.200 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.
9. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $101.250 to $101.820 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 transactions reported on this Form 4 were effected pursuant to a Rule 10b5-1 trading plan adopted by the reporting person's spouse on June 7, 2026.
11. Represents shares held by the Reporting Person's spouse.
12. The options are fully vested and exercisable.
Remarks:
/s/ Thomas P. Lynch, Attorney-in-Fact09/16/2026
** Signature of Reporting PersonDate
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

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