The prospectus, dated November 5, 2025 and filed as a Form 424B4 on November 6, 2025, disclosed estimated net proceeds to the company of approximately $248.4 million based on the base offering, or approximately $286.4 million assuming full exercise of the overallotment option, after underwriting discounts and commissions and estimated offering expenses. The underwriting discount was $4.20 per share, totaling $19,114,620 on the base offering and $21,981,813 assuming full exercise of the option, consistent with the actual outcome since the option was exercised in full.
J.P. Morgan Securities LLC, Piper Sandler & Co., Jefferies LLC, and William Blair & Company, L.L.C. acted as joint book-running managers and representatives of the underwriters. The prospectus's underwriting table disclosed specific share allocations among the syndicate: J.P. Morgan Securities LLC (1,592,885 shares), Piper Sandler & Co. (910,220 shares), Jefferies LLC (682,665 shares), William Blair & Company, L.L.C. (523,377 shares), Stifel, Nicolaus & Company, Incorporated (318,577 shares), Wells Fargo Securities, LLC (295,822 shares), and BTIG, LLC (227,554 shares), totaling 4,551,100 shares. The company also reserved up to 5 percent of the shares offered for sale at the IPO price to officers, directors, employees, and certain individuals identified by management through a directed share program.
The company stated that it intends to use the net proceeds from the offering, together with existing cash and cash equivalents, for working capital and other general corporate purposes, including funding growth, research and development initiatives, technology development, and operating expenses. The prospectus specifically disclosed that the company does not currently have specific planned uses for the proceeds and may use a portion to acquire or invest in complementary products, technologies, or businesses, though it had no agreements or commitments for any such transactions as of the prospectus date.
On a dilution basis, the prospectus disclosed that the company's historical net tangible book value deficit as of June 30, 2025 was $(22.46) per share, and its pro forma net tangible book value (reflecting preferred stock conversion and related reclassifications occurring immediately prior to the offering) was $4.25 per share. After giving effect to the sale of 4,551,100 shares at $60.00 per share, pro forma as adjusted net tangible book value was $9.43 per share, representing an immediate increase of $5.18 per share to existing stockholders and immediate dilution of $50.57 per share to new investors in the base offering. Assuming full exercise of the overallotment option, pro forma as adjusted net tangible book value would increase to $10.12 per share, with dilution to new investors of $49.88 per share.
As this was the company's initial public offering, there was no prior public trading price against which to measure a premium or discount at pricing; the $60.00 per share price was set through the IPO bookbuilding process rather than relative to an existing market price.
On the legal side, the prospectus disclosed that Gunderson Dettmer Stough Villeneuve Franklin & Hachigian, LLP of San Francisco passed on the validity of the shares being offered on behalf of BillionToOne, while Cooley LLP of San Francisco represented the underwriters in connection with the offering.
On the closing timeline, BillionToOne filed its registration statement on Form S-1 on October 7, 2025, amended it on October 17, 2025, registered its Class A common stock for listing on Nasdaq via Form 8-A12B on November 3, 2025, priced the offering with the final prospectus dated November 5, 2025 (filed as a 424B4 on November 6, 2025), and completed the IPO closing on November 7, 2025, as confirmed in a Form 8-K filed November 10, 2025. In that closing 8-K, the company also reported that it filed its amended and restated certificate of incorporation and that its amended and restated bylaws became effective in connection with the IPO closing. Based on this closing 8-K, the offering has fully closed; it is not pending regulatory review as previously indicated.