What happened
BillionToOne, Inc. (NASDAQ: BLLN) said Chairman and CEO Oguzhan Atay sold 11,000 shares of Class A Common Stock from 2026-10-14 to 2026-10-15. The shares sold for $98.00 to $102.78 each, or about $1.09 million in total. After the sale, Atay held 149,168 shares. The filing was dated 2026-10-16.
The filing says the trades were made under a Rule 10b5-1 trading plan adopted on June 5, 2026. It also says the shares sold came from stock options exercised the same day at a $2.8 strike. The form lists 3,183 options exercised on 10/14/2026 and 5,150 on 10/15/2026. It says the options were fully vested and exercisable. It also shows 473,779 derivative securities after the first exercise and 468,629 after the second.
Key numbers
| Metric | Latest | Change | Source |
|---|---|---|---|
| Shares sold | 11,000 shares | SEC Form 4 | |
| Sale price range | $98.00 to $102.78 per share | SEC Form 4 | |
| Estimated sale value | about $1.09 million | SEC Form 4 | |
| Shares held after sale | 149,168 shares | SEC Form 4 | |
| Option exercise price | $2.8 | SEC Form 4 |
Read more: BillionToOne (BLLN) stock analysis and investment case
Why it matters
OptimistFi's case is that BillionToOne works if its prenatal and oncology molecular tests stay differentiated enough to win orders and reimbursement while scale turns volume into durable cash generation. This filing is mixed for that case because it shows a planned sale by the chairman and CEO, not a clinical or financial update.
OptimistFi calculates the 11,000 shares were about 6.9% of Atay's holding before the trade. The reported sale prices were far above the $2.8 strike, and the filing links the shares to same-day exercises. That points to a liquidity event tied to vesting, not to a change in operations.
The sale was split across multiple transactions, so the weighted average prices matter more than any one print. The filing also shows 473,779 derivative securities after the first exercise and 468,629 after the second. Atay still held 149,168 shares afterward. That leaves him with a large reported stake.
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What's next
The exercised options expire on 06/07/2031, the next dated item in the filing. A later Form 4 showing more sales under the same plan would extend the planned-liquidity signal. If there are no more sales, this stays a narrow insider event.
Any later filing would matter most if the remaining stake falls further.
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Sources
- SEC Form 4 — BillionToOne, Inc. Form 4 filed 2026-10-16 for Oguzhan Atay
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Originally published on OptimistFi, evidence-first equity research. More at optimistfi.com.
