BLLN insider ownership: who sold, why, and what they still hold

What stands out

Two directors bought shares: Thomas Bremner (24K shares, $1.4M) and Akshay Rai (2.5K shares, $150K). These are the first purchases by current officers or directors in the filings on record.Thomas Bremner: purchase, Nov 7, 2025 · Akshay Rai: purchase, Nov 7, 2025

Selling picked up in the last 90 days: officers and directors sold 248K shares, against an average of 58K per 90 days earlier in the period. Most of it was Oguzhan Atay (102K shares in the last 90 days) and David Tsao (63K shares in the last 90 days); 100% of these sales were under disclosed plans.Oguzhan Atay: largest recent sale, Aug 5, 2026 · David Tsao: largest recent sale, Aug 25, 2026

A share of stake is shown for 0 of the 6 officers and directors who sold. 13 are left out

Left out: David Tsao, Oguzhan Atay, Shan Sakakibara, Bosch ten, Nancy Johnson, Thomas Lynch, Thomas Bremner, Krishna Kolluri, John Lister, Firat Ileri, Ross Taylor, Akshay Rai and Anthony Pagano (share of stake is being verified).

Disclosed company stock is not an insider's whole wealth.

Who sold, and how much of their stake

Officers and directors, past 12 months. Their share of stake is being verified and is not shown yet; amounts and trading plans are below.

Oguzhan Atay

Chairman and CEO, Director

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$23.0MDisclosed plan

David Tsao

Chief Technology Officer, Director

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$11.0MDisclosed plan

Thomas Lynch

General Counsel, Chief Compliance Officer and Secretary

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$5.9MDisclosed plan

Nancy Johnson

Senior Vice President of Sales and Commercial Operations

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$3.3MDisclosed plan

Shan Sakakibara

Chief Product Officer

Not confirmed

Share of stake not shown: share of stake is being verified. Why

$3.2MDisclosed plan

All 6 sellers

Selling by month

Officers and directors, Oct 2025 to Oct 2026. Each sale is counted once: under a disclosed plan, else to cover taxes, else no plan disclosed.

Disclosed planOne dollar scale for every month; the tallest bar is labeled

Recent activity

Past 30 days, Sep 14, 2026 to Oct 13, 2026

Oct 5, 20262 executives sold 23K shares ($2.5M) under a disclosed trading plan. 20K shares came in from vesting or option exercises the same day, so their combined holdings fell by 2.8K net.

Who	Shares	Price	% of total stake	Total stake after	Trade date	Filed
David Tsao Chief Technology Officer, Director	20,000	$108.15	n/a	n/a	Oct 5, 2026	Oct 7, 2026
Bosch ten SVP of Laboratory Operations	2,834	$105.15	n/a	n/a	Oct 5, 2026	Oct 7, 2026

Sep 28, 2026Oguzhan Atay sold 11K shares ($1.3M) under a disclosed trading plan. 8.3K shares came in from vesting or option exercises the same day, so the holding fell by 2.7K net.

Who	Shares	Price	% of total stake	Total stake after	Trade date	Filed
Oguzhan Atay Chairman and CEO, Director	10,999	$120.64	n/a	n/a	Sep 28, 2026	Sep 30, 2026

Sep 24, 20262 executives sold 4.7K shares ($587K) under a disclosed trading plan. 3.3K shares came in from vesting or option exercises the same day, so their combined holdings fell by 1.4K net.

Who	Shares	Price	% of total stake	Total stake after	Trade date	Filed
David Tsao Chief Technology Officer, Director	3,333	$125.00	n/a	n/a	Sep 24, 2026	Sep 28, 2026
Bosch ten SVP of Laboratory Operations	1,416	$120.00	n/a	n/a	Sep 24, 2026	Sep 28, 2026

Sep 21, 2026Bosch ten sold 1.4K shares ($151K) under a disclosed trading plan.

Who	Shares	Price	% of total stake	Total stake after	Trade date	Filed
Bosch ten SVP of Laboratory Operations	1,416	$106.61	n/a	n/a	Sep 21, 2026	Sep 23, 2026

Sep 17, 2026Thomas Lynch sold 35K shares ($3.9M) under a disclosed trading plan. 35K shares came in from vesting or option exercises the same day, so the holding rose by 0 net.

Who	Shares	Price	% of total stake	Total stake after	Trade date	Filed
Thomas Lynch General Counsel, Chief Compliance Officer and Secretary	35,112	$110.33	n/a	n/a	Sep 17, 2026	Sep 21, 2026

Show all 6 events

Sep 14, 2026Oguzhan Atay sold 30K shares ($3.0M) under a disclosed trading plan. 25K shares came in from vesting or option exercises the same day, so the holding fell by 5.3K net.

Who	Shares	Price	% of total stake	Total stake after	Trade date	Filed
Oguzhan Atay Chairman and CEO, Director	30,331	$99.91	n/a	n/a	Sep 14, 2026	Sep 16, 2026

"% of total stake" is the shares in an event against all the vested shares the person held that day, across every share class and holding entity, after that day's vesting. "n/a" means the person's holdings are not confirmed, or the row is a purchase. "Holdings record incomplete" means more shares were sold than the filings show the person held that day, so a percentage would be wrong.

Outside holders, reported separately

Humming Bird Ventures Management NV, NeoTribe Ventures I, L.P. and Firat Ileri and 2 more reported no open-market sales in the past 12 months. Large shareholders and the funds or companies that board members represent are not part of management, so they are left out of the figures above.

Details

Common questions

Is the BillionToOne, Inc. CEO selling stock?

Yes. Oguzhan Atay sold 192K shares ($23.0M) in the past 12 months, all of it under a trading plan disclosed in the filings.

Why are BillionToOne, Inc. insiders selling?

Filings rarely give a reason, and we don't guess at one. What they show is how the sales were made: 100% of sales by value ran under 10b5-1 trading plans disclosed in the filings. A trading plan schedules sales in advance.

Are any BillionToOne, Inc. insiders buying?

Yes. 2 officers or directors reported 6 purchases in the past 12 months (Form 4 code P; rows the filings describe as reinvested dividends, plan purchases, private deals or moves into the person's own trust are not counted).

The evidence

Who sold6 officers and directors: amount, % of holdings, trading plan

Who sold	Amount	% of holdings	Trading plan
Oguzhan Atay Chairman and CEO, Director	$23.0M 192K shares	Not confirmed share of stake is being verified. Why	Disclosed plan
David Tsao Chief Technology Officer, Director	$11.0M 103K shares	Not confirmed share of stake is being verified. Why	Disclosed plan
Thomas Lynch General Counsel, Chief Compliance Officer and Secretary	$5.9M 55K shares	Not confirmed share of stake is being verified. Why	Disclosed plan
Nancy Johnson Senior Vice President of Sales and Commercial Operations	$3.3M 29K shares	Not confirmed share of stake is being verified. Why	Disclosed plan
Shan Sakakibara Chief Product Officer	$3.2M 28K shares	Not confirmed share of stake is being verified. Why	Disclosed plan
Bosch ten SVP of Laboratory Operations	$2.0M 18K shares	Not confirmed share of stake is being verified. Why	Disclosed plan

Board members representing outside shareholders, reported separately: Firat Ileri, Krishna Kolluri, Thomas Bremner. Details

Outside holder, reported separately: Humming Bird Ventures Management NV (a 10% owner, not part of management). No open-market sales reported in the period. Latest filing

Outside holder, reported separately: NeoTribe Ventures I, L.P. (a 10% owner, not part of management). No open-market sales reported in the period. Latest filing

The full ownership picture0 of 13 officers and directors confirmed

Vested shares across all share classes, held directly and through trusts, LLCs and family members, as reported on SEC Forms 3, 4 and 5. Unvested awards and options are never counted as owned shares.

Insider

Held Oct 13, 2025

Sold

Held Oct 13, 2026

Still held

David Tsao

Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for David Tsao are complete.

Chief Technology Officer, Director

n/a

−103K

n/a

Vesting, gifts, unvested awards and holding lines for David Tsao

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for David Tsao are complete; balances and unit counts will be added when the check is finished.

−20Kgifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
536,667	$2.80	Jun 7, 2031	$54.9M
501,551	$20.04	Jun 18, 2035	$42.7M

Estimate: options held × ($105.15 − strike price), using the most recent insider trade price on Form 4 (Oct 5, 2026), not a market close.

Oguzhan Atay

Chairman and CEO, Director

n/a

−192K

n/a

Vesting, gifts, unvested awards and holding lines for Oguzhan Atay

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Oguzhan Atay are complete; balances and unit counts will be added when the check is finished.

−30Kgifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
493,629	$2.80	Jun 7, 2031	$50.5M
1,003,102	$20.04	Jun 18, 2035	$85.4M

Estimate: options held × ($105.15 − strike price), using the most recent insider trade price on Form 4 (Oct 5, 2026), not a market close.

Shan Sakakibara

Chief Product Officer

n/a

−28K

n/a

Vesting, gifts, unvested awards and holding lines for Shan Sakakibara

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Shan Sakakibara are complete; balances and unit counts will be added when the check is finished.

−3.5Kgifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
50,000	$2.80	Jun 7, 2031	$5.1M
35,826	$8.65	Jan 18, 2033	$3.5M
61,174	$30.78	Sep 30, 2035	$4.5M

Estimate: options held × ($105.15 − strike price), using the most recent insider trade price on Form 4 (Oct 5, 2026), not a market close.

Bosch ten

SVP of Laboratory Operations

n/a

−18K

n/a

Vesting, gifts, unvested awards and holding lines for Bosch ten

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Bosch ten are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
28,500	$0.56	Sep 30, 2030	$3.0M
20,000	$2.80	Jun 7, 2031	$2.0M
15,000	$10.92	Aug 1, 2032	$1.4M
30,000	$15.17	Jun 5, 2034	$2.7M
37,500	$30.78	Sep 30, 2035	$2.8M

Estimate: options held × ($105.15 − strike price), using the most recent insider trade price on Form 4 (Oct 5, 2026), not a market close.

Nancy Johnson

Senior Vice President of Sales and Commercial Operations

n/a

−29K

n/a

Vesting, gifts, unvested awards and holding lines for Nancy Johnson

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Nancy Johnson are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
125,000	$0.45	Aug 20, 2029	$13.1M
25,000	$2.80	Jun 7, 2031	$2.6M
40,000	$11.55	Oct 17, 2033	$3.7M
20,000	$17.12	Oct 16, 2034	$1.8M
40,000	$30.78	Sep 30, 2035	$3.0M

Estimate: options held × ($105.15 − strike price), using the most recent insider trade price on Form 4 (Oct 5, 2026), not a market close.

Thomas Lynch

General Counsel, Chief Compliance Officer and Secretary

n/a

−55K

n/a

Vesting, gifts, unvested awards and holding lines for Thomas Lynch

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Thomas Lynch are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
48,974	$8.65	Jan 18, 2033	$4.7M
4,063	$11.55	Oct 17, 2033	$380K
5,417	$17.12	Oct 16, 2034	$477K
30,834	$30.78	Sep 30, 2035	$2.3M

Estimate: options held × ($105.15 − strike price), using the most recent insider trade price on Form 4 (Oct 5, 2026), not a market close.

Thomas Bremner

Director

n/a

Vesting, gifts, unvested awards and holding lines for Thomas Bremner

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Thomas Bremner are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Krishna Kolluri

Director

n/a

Vesting, gifts, unvested awards and holding lines for Krishna Kolluri

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Krishna Kolluri are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

John Lister

Chief Administrative Officer

n/a

Vesting, gifts, unvested awards and holding lines for John Lister

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for John Lister are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
133,300	$23.15	Aug 4, 2035	$10.9M

Estimate: options held × ($105.15 − strike price), using the most recent insider trade price on Form 4 (Oct 5, 2026), not a market close.

Firat Ileri

Director

n/a

Vesting, gifts, unvested awards and holding lines for Firat Ileri

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Firat Ileri are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Ross Taylor

Chief Financial Officer

n/a

Vesting, gifts, unvested awards and holding lines for Ross Taylor

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Ross Taylor are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Stock options (not counted as shares):

Options held	Strike price	Expires	Intrinsic value (estimate)
175,000	$11.55	Jan 13, 2034	$16.4M
75,000	$30.78	Sep 30, 2035	$5.6M

Estimate: options held × ($105.15 − strike price), using the most recent insider trade price on Form 4 (Oct 5, 2026), not a market close.

Akshay Rai

Director

n/a

Vesting, gifts, unvested awards and holding lines for Akshay Rai

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Akshay Rai are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Anthony Pagano

Director

n/a

Vesting, gifts, unvested awards and holding lines for Anthony Pagano

Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Anthony Pagano are complete; balances and unit counts will be added when the check is finished.

0gifted (net of own trusts)

Holdings and share of stake for BillionToOne, Inc. are being verified, so no balances, unit counts or percentages are shown. Sales, proceeds, plan and tax status, titles and dates come straight from individual filings.

What explains the selling$48.4M of sales by plan status, purpose, seller and month

Officer and director open-market sales: $48.4M across 425,729 shares. Plan status and stated purpose are separate questions, and a sale can have both.

By plan status

Disclosed plan · $48.4M · 100%

Purchases · 2 buyers (6 trades)

2 officers and directors bought shares in this period, in 6 trades(Form 4 code P, leaving out rows the filings describe as reinvested dividends, plan purchases, private deals or moves into the person's own trust). Across all their filings on record there are 6 purchase trades.

Seller	Shares sold	Proceeds	Under a disclosed plan	Share of total	Sales dates
Oguzhan Atay Chairman and CEO, Director	192K	$23.0M	100%	47%	Jun 8, 2026 to Sep 28, 2026
David Tsao Chief Technology Officer, Director	103K	$11.0M	100%	23%	Jun 15, 2026 to Oct 5, 2026
Thomas Lynch General Counsel, Chief Compliance Officer and Secretary	55K	$5.9M	100%	12%	Sep 8, 2026 to Sep 17, 2026
Nancy Johnson Senior Vice President of Sales and Commercial Operations	29K	$3.3M	100%	7%	Jun 8, 2026 to Jul 16, 2026
Shan Sakakibara Chief Product Officer	28K	$3.2M	100%	7%	Jun 8, 2026 to Jul 31, 2026
Bosch ten SVP of Laboratory Operations	18K	$2.0M	100%	4%	Jun 15, 2026 to Oct 5, 2026

Sales by month

Month	Sale proceeds	Disclosed plan	To cover taxes	No plan disclosed
Oct 2025	$0	$0	$0	$0
Nov 2025	$0	$0	$0	$0
Dec 2025	$0	$0	$0	$0
Jan 2026	$0	$0	$0	$0
Feb 2026	$0	$0	$0	$0
Mar 2026	$0	$0	$0	$0
Apr 2026	$0	$0	$0	$0
May 2026	$0	$0	$0	$0
Jun 2026	$9.4M	$9.4M	$0	$0
Jul 2026	$12.8M	$12.8M	$0	$0
Aug 2026	$10.7M	$10.7M	$0	$0
Sep 2026	$13.1M	$13.1M	$0	$0
Oct 2026	$2.5M	$2.5M	$0	$0

Board members representing outside shareholders (3)Listed and sourced; not part of the management totals or the answer line

Directors whose reported holdings sit mostly in an investment fund or a corporate shareholder they represent, not in their own name, with beneficial ownership disclaimed except for their own financial interest. Listed and sourced here; not part of the management totals or the answer line. Shares a fund hands to its own investors are distributions, not sales.

Board member	Held Oct 13, 2025	Sold	Held Oct 13, 2026	Still held
Firat Ileri ! Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Firat Ileri are complete. Director	n/a	0	n/a	n/a
Vesting, gifts, unvested awards and holding lines for Firat Ileri Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Firat Ileri are complete; balances and unit counts will be added when the check is finished. 0gifted (net of own trusts)
Krishna Kolluri ! Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Krishna Kolluri are complete. Director	n/a	0	n/a	n/a
Vesting, gifts, unvested awards and holding lines for Krishna Kolluri Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Krishna Kolluri are complete; balances and unit counts will be added when the check is finished. 0gifted (net of own trusts)
Thomas Bremner ! Holdings and share of stake are being verified. Share-of-stake figures and holdings for this company are held back while they are verified. Sales and other transactions for Thomas Bremner are complete. Director	n/a	0	n/a	n/a
Vesting, gifts, unvested awards and holding lines for Thomas Bremner Holdings and share of stake are being verified. Sales, proceeds, plan and tax status and dates for Thomas Bremner are complete; balances and unit counts will be added when the check is finished. 0gifted (net of own trusts)

Krishna Kolluri: 1.34M shares were distributed in kind to the fund's own investors. These are distributions, not sales.

Known gaps and uncertainty13 officers and directors not confirmed

Holdings and share of stake are being verified. Balances, unit counts and every share-of-stake figure for BillionToOne, Inc. are held back until that check is finished. Sales, proceeds, plan and tax status, titles and dates come straight from individual filings and are complete.

External context: we only cite outside events when a documented connection exists. None is shown for this period.

Sources and methodology76 filings on record, 76 filed in the 12-month period, and how we read them

All 76 Forms 3, 4 and 5 on record for BillionToOne, Inc. (SEC CIK 2070849), filed from Nov 5, 2025 to Oct 7, 2026; 76 of them were filed in the 12 months this page covers, retrieved from SEC EDGAR on Oct 13, 2026. Prices are the ones reported in each filing, often weighted averages.

Holdings. Each holding line (a share class plus an owner, such as a trust or LLC) carries its last reported balance forward. Entities first reported during the period start at zero, so transfers between an insider's own trusts don't count as selling. Lines not reported for three years or more are listed separately and left out of totals.

Sales. A sale counts as under a 10b5-1 plan if its footnote cites one or the filing's Rule 10b5-1 box is checked, and as tax-related if its footnote cites tax obligations or sell-to-cover. Shares withheld by the company for taxes are listed separately. Sales with neither attribute are labeled "no plan disclosed".

Full methodology

Spotted something wrong on this page? Report an error. We check every report against the SEC filing and list what we fix in the corrections log.

BillionToOne, Inc. insiders sold $48.4M in the past 12 months. How much of their stake is that?

What stands out

Who sold, and how much of their stake

Selling by month

Recent activity

Outside holders, reported separately

Common questions

Is the BillionToOne, Inc. CEO selling stock?

Why are BillionToOne, Inc. insiders selling?

Are any BillionToOne, Inc. insiders buying?

The evidence

Purchases · 2 buyers (6 trades)

Sales by month