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

BillionToOne CEO sells shares, exercises options

BillionToOne, Inc. Chairman and CEO Atay Oguzhan reported a mix of open-market sales and option exercises involving the company’s Class A Common Stock.

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Form Type
4

Rhea-AI Filing Summary

BillionToOne, Inc. Chairman and CEO Atay Oguzhan reported a mix of open-market sales and option exercises involving the company’s Class A Common Stock. The Form 4 shows Rule 10b5-1 plan sales totaling 38,750 shares, including shares held indirectly through his spouse, at weighted average prices generally between about $118 and $125 per share.

On the same date, Oguzhan also exercised stock options to acquire 26,250 shares of Class A Common Stock at an exercise price of $2.80 per share, converting derivative awards into direct share ownership while continuing to hold a remaining common stock position as reflected in the filing’s post-transaction share balances.

Insider Atay Oguzhan
Role Chairman and CEO
Sold 38,750 shs ($4.73M)
Approx. gross sale proceeds $4.73M
Approx. exercise cost $74K
Type Security Shares Price Value
Exercise Stock Option (right to buy) 20,000 $2.80 $56K
Exercise Stock Option (right to buy) 6,250 $2.80 $18K
Exercise Class A Common Stock 20,000 $2.80 $56K
Exercise Class A Common Stock 6,250 $2.80 $18K
Sale Class A Common Stock 1,320 $118.4866 $156K
Sale Class A Common Stock 3,639 $119.365 $434K
Sale Class A Common Stock 1,828 $120.6601 $221K
Sale Class A Common Stock 1,115 $121.8364 $136K
Sale Class A Common Stock 6,223 $123.0714 $766K
Sale Class A Common Stock 5,253 $123.8094 $650K
Sale Class A Common Stock 622 $124.6144 $78K
Sale Class A Common Stock 412 $118.487 $49K
Sale Class A Common Stock 1,138 $119.3648 $136K
Sale Class A Common Stock 570 $120.6596 $69K
Sale Class A Common Stock 349 $121.8357 $43K
Sale Class A Common Stock 1,945 $123.0709 $239K
Sale Class A Common Stock 1,642 $123.8093 $203K
Sale Class A Common Stock 194 $124.6147 $24K
Sale Class A Common Stock 1,034 $118.8074 $123K
Sale Class A Common Stock 591 $119.6744 $71K
Sale Class A Common Stock 444 $120.688 $54K
Sale Class A Common Stock 587 $122.0839 $72K
Sale Class A Common Stock 2,323 $123.2473 $286K
Sale Class A Common Stock 1,221 $124.0448 $151K
Sale Class A Common Stock 50 $124.74 $6K
Sale Class A Common Stock 1,034 $118.8071 $123K
Sale Class A Common Stock 591 $119.6744 $71K
Sale Class A Common Stock 444 $120.688 $54K
Sale Class A Common Stock 586 $122.0845 $72K
Sale Class A Common Stock 2,324 $123.2472 $286K
Sale Class A Common Stock 1,221 $124.0448 $151K
Sale Class A Common Stock 50 $124.74 $6K
Holdings After Transaction: Stock Option (right to buy) — 587,500 contracts (Direct); Class A Common Stock — 0 shares (Direct); Class A Common Stock — 175,000 shares (Indirect, By spouse)
Footnotes (16)
  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.
  2. F2. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $118.050 to $119.020 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.
  3. F3. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $119.055 to $119.970 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.
  4. F4. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $120.225 to $121.160 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 $121.390 to $122.230 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 $122.465 to $123.450 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 $123.475 to $124.455 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 $124.535 to $124.735 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 $118.250 to $119.240 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. Represents shares held by the Reporting Person's spouse.
  11. F11. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $119.305 to $120.2725 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. F12. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $120.380 to $121.020 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.
  13. F13. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $121.555 to $122.490 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. F14. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $122.725 to $123.720 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.
  15. F15. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $123.740 to $124.735 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.
  16. F16. The options are fully vested and exercisable.
Shares sold 38,750 shares Open-market sales of Class A Common Stock on 2026-07-06
Shares from option exercises 26,250 shares Common shares acquired via option exercise on 2026-07-06
Option exercise price $2.80 per share Stock options exercised into Class A Common Stock
Weighted average sale price example $118.050–$119.020 range One sale group’s price range described in a footnote
Another sale price range $123.740–$124.735 range Higher-priced sale group from weighted average footnote
10b5-1 plan adoption date March 6, 2026 Date CEO adopted trading plan governing these sales
Rule 10b5-1 trading plan regulatory
"transactions 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. These shares were sold in multiple transactions"
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)" with an exercise or conversion price of $2.8000"
Class A Common Stock financial
"security_title: "Class A Common Stock" for the reported non-derivative transactions"
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.
indirect ownership financial
"direct_or_indirect: "I" and nature_of_ownership: "By spouse" indicating indirect ownership"

FAQ

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

What insider transactions did BillionToOne (BLLN) report on this Form 4?
The Form 4 reports a combination of open-market sales and stock option exercises by Chairman and CEO Atay Oguzhan, involving Class A Common Stock on a single transaction date.

How many BillionToOne (BLLN) shares did the CEO sell in this filing?
The filing’s transaction summary shows open-market sales totaling 38,750 shares of BillionToOne Class A Common Stock, executed in multiple trades at various weighted average prices around the low- to mid-$120s per share.

Were any BillionToOne (BLLN) shares sold through a Rule 10b5-1 plan?
Yes. A footnote states the reported transactions were effected under a Rule 10b5-1 trading plan adopted by the reporting person on March 6, 2026, indicating the trades were pre-arranged rather than discretionary.

Did the BillionToOne (BLLN) CEO exercise stock options in this Form 4?
Yes. The Form 4 shows option exercises for 26,250 shares of Class A Common Stock at an exercise price of $2.80 per share, converting derivative positions into directly held common shares.

What prices were the BillionToOne (BLLN) CEO’s shares sold at?
Each line item reports a weighted average sale price, with footnotes describing multiple trades within ranges, such as $118.050 to $124.735 per share. The reported column prices reflect these weighted averages for each transaction group.

Do any BillionToOne (BLLN) shares in this Form 4 relate to the CEO’s spouse?
Yes. Several transactions are marked as held indirectly “by spouse,” and a footnote clarifies those shares are owned by the reporting person’s spouse, distinguishing them from his directly held shares.

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

Form 4 Insider Transactions: What Each Field Means →
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Accepted by SEC EDGAR
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)
07/06/2026		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 Stock07/06/2026M(1)20,000A$2.820,000D
Class A Common Stock07/06/2026M(1)6,250A$2.826,250D
Class A Common Stock07/06/2026S(1)1,320D$118.4866(2)24,930D
Class A Common Stock07/06/2026S(1)3,639D$119.365(3)21,291D
Class A Common Stock07/06/2026S(1)1,828D$120.6601(4)19,463D
Class A Common Stock07/06/2026S(1)1,115D$121.8364(5)18,348D
Class A Common Stock07/06/2026S(1)6,223D$123.0714(6)12,125D
Class A Common Stock07/06/2026S(1)5,253D$123.8094(7)6,872D
Class A Common Stock07/06/2026S(1)622D$124.6144(8)6,250D
Class A Common Stock07/06/2026S(1)412D$118.487(2)5,838D
Class A Common Stock07/06/2026S(1)1,138D$119.3648(3)4,700D
Class A Common Stock07/06/2026S(1)570D$120.6596(4)4,130D
Class A Common Stock07/06/2026S(1)349D$121.8357(5)3,781D
Class A Common Stock07/06/2026S(1)1,945D$123.0709(6)1,836D
Class A Common Stock07/06/2026S(1)1,642D$123.8093(7)194D
Class A Common Stock07/06/2026S(1)194D$124.6147(8)0D
Class A Common Stock07/06/2026S(1)1,034D$118.8074(9)186,466IBy spouse(10)
Class A Common Stock07/06/2026S(1)591D$119.6744(11)185,875IBy spouse(10)
Class A Common Stock07/06/2026S(1)444D$120.688(12)185,431IBy spouse(10)
Class A Common Stock07/06/2026S(1)587D$122.0839(13)184,844IBy spouse(10)
Class A Common Stock07/06/2026S(1)2,323D$123.2473(14)182,521IBy spouse(10)
Class A Common Stock07/06/2026S(1)1,221D$124.0448(15)181,300IBy spouse(10)
Class A Common Stock07/06/2026S(1)50D$124.74181,250IBy spouse(10)
Class A Common Stock07/06/2026S(1)1,034D$118.8071(9)180,216IBy spouse(10)
Class A Common Stock07/06/2026S(1)591D$119.6744(11)179,625IBy spouse(10)
Class A Common Stock07/06/2026S(1)444D$120.688(12)179,181IBy spouse(10)
Class A Common Stock07/06/2026S(1)586D$122.0845(13)178,595IBy spouse(10)
Class A Common Stock07/06/2026S(1)2,324D$123.2472(14)176,271IBy spouse(10)
Class A Common Stock07/06/2026S(1)1,221D$124.0448(15)175,050IBy spouse(10)
Class A Common Stock07/06/2026S(1)50D$124.74175,000IBy spouse(10)
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)$2.807/06/2026M20,000 (16)06/07/2031Class A Common Stock20,000$2.8593,750D
Stock Option (right to buy)$2.807/06/2026M6,250 (16)06/07/2031Class A Common Stock6,250$2.8587,500D
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 $118.050 to $119.020 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.
3. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $119.055 to $119.970 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.
4. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $120.225 to $121.160 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 $121.390 to $122.230 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 $122.465 to $123.450 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 $123.475 to $124.455 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 $124.535 to $124.735 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 $118.250 to $119.240 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. Represents shares held by the Reporting Person's spouse.
11. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $119.305 to $120.2725 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 $120.380 to $121.020 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.
13. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $121.555 to $122.490 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 reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $122.725 to $123.720 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.
15. The reported price in Column 4 is a weighted average price. These shares were sold in multiple transactions at prices ranging from $123.740 to $124.735 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.
16. The options are fully vested and exercisable.
Remarks:
/s/ Thomas P. Lynch, Attorney-in-Fact07/08/2026
** 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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