NEW YORK, December 31, 2025, 15:27 ET — Regular session.
Shares of BillionToOne (BLLN.O) fell about 4% on Wednesday, sliding $3.49 to $81.61 in afternoon trading. The stock has traded between $81.25 and $89.36, with about 243,000 shares changing hands.
The move came on the final trading day of 2025, when liquidity is typically thin and price swings can look bigger than the underlying news. “It’s perfectly fine in any bull market to have moments of cost,” said Giuseppe Sette, co-founder and president of Reflexivity, pointing to profit-taking when liquidity is low. U.S. markets are closed on Thursday for New Year’s Day. 1
Diagnostics peers were steadier: Natera was down about 0.4%, while Guardant Health was up about 1.7% and Exact Sciences was flat. That left BillionToOne lagging its closest public comps into the close.
Company-specific catalysts were sparse on Wednesday’s calendar. BillionToOne’s most recent disclosures were a quarterly report filed on Dec. 10 and an 8-K filed on Dec. 9, a company search on the SEC’s EDGAR database showed; the company’s fiscal year ends Dec. 31. 2
In its latest earnings update, the company reported third-quarter revenue of $83.5 million, up 117% from a year earlier, and operating income of $9.6 million — a measure of profit from the core business before interest and taxes. BillionToOne forecast full-year 2025 revenue of $293 million to $299 million and fourth-quarter revenue of $84 million to $90 million, and said it expects positive GAAP operating income for both the quarter and the year. Prenatal testing accounted for $74.1 million of third-quarter revenue, while oncology testing revenue was $8.7 million, the company said. 3
BillionToOne priced its upsized initial public offering at $60 per share and said the shares were expected to start trading on Nasdaq on Nov. 6 under the ticker BLLN. The company said gross proceeds were expected to be about $273.1 million before any exercise of the underwriters’ option for additional shares. 4
Next up, management plans to present at the J.P. Morgan Healthcare Conference on Jan. 12 from 9:45 a.m. to 10:25 a.m. Pacific time, with a webcast available through the company’s investor site, BillionToOne said. 5
Investors will be looking for updated commentary on demand for its prenatal testing business and the pace of adoption in oncology, where blood-based “liquid biopsy” tests search for tumor signals without a tissue sample. Those updates can matter for near-term revenue growth and for long-term expansion into new indications.
Margin trends are another focus. Gross margin is the share of revenue left after direct costs, and it can move quickly in diagnostics based on test mix and payer reimbursement.
