The Sionna Therapeutics, Inc. (Nasdaq: SION) SEC filings page on Stock Titan provides access to the company’s regulatory disclosures as filed with the U.S. Securities and Exchange Commission. Sionna describes itself as a clinical-stage biopharmaceutical company focused on developing CFTR-targeted therapies for cystic fibrosis, and its filings offer detail on this business and its financial position.
Among the key documents available are current reports on Form 8-K, where Sionna furnishes press releases announcing quarterly financial results and business highlights. For example, the company has used Form 8-K to present information on research and development expenses, general and administrative expenses, net loss, cash and cash equivalents, and progress across its clinical pipeline of NBD1 stabilizers and complementary CFTR modulators.
In addition to 8-Ks, investors typically look to annual reports on Form 10-K and quarterly reports on Form 10-Q for broader discussions of risk factors, research and development activities, and the company’s focus on cystic fibrosis therapies. These filings can also describe Sionna’s status as an emerging growth company, its operating segment dedicated to CF drug development, and other structural aspects of the business.
Stock Titan enhances access to SION filings by pairing real-time updates from the EDGAR system with AI-powered summaries that explain the significance of each document in clear language. Users can quickly identify items related to clinical trial progress, financial condition, and other material events, and can review insider and management-related disclosures where applicable. This page serves as a central location for reviewing Sionna’s regulatory history and understanding how its CF-focused strategy is reflected in formal SEC documents.
Sionna Therapeutics (SION): RA Capital–affiliated reporting persons disclosed open‑market sales of common stock. Trades occurred on 10/24/2025 at $39.50 and on 10/28/2025 at a weighted average price of $39.58, with individual transactions ranging from $39.50 to $39.81.
Following the 10/28 transactions, indirect holdings reported included 6,905,625 shares (RA Capital Healthcare Fund, L.P.) and 715,988 shares (RA Capital Nexus Fund, L.P.), plus 2,240,708 shares (Nexus Fund III) and 209,391 shares (a separately managed account). The filing identifies the reporting persons as Director and 10% Owner where indicated, and notes that a partner of the adviser serves on the board.
Sionna Therapeutics (SION) President & CEO (also a Director) reported option exercises and open‑market sales on 10/21/2025 under a pre‑established Rule 10b5‑1 trading plan adopted on May 21, 2025.
The executive exercised non‑qualified stock options at $6.11 per share and sold the resulting shares at weighted average prices of $34.44, $35.63, $36.60, and $37.31 (each comprising multiple trades within stated ranges). Following these transactions, the reporting person directly owned 547,343 shares. The options exercised were from grants expiring on March 1, 2032, with vesting in forty‑eight equal monthly installments following February 2, 2022.
Sionna Therapeutics (SION): Director Form 4 discloses Rule 10b5‑1 sales. On 10/21/2025, indirect holdings associated with the reporting person sold multiple blocks of common stock via pre‑planned trades. Examples include 22,339 shares at a weighted average $32.69, 19,948 shares at $33.87, 5,763 shares at $34.91, and 25,327 shares at $35.69. Prices reflect weighted averages from disclosed ranges. Following these transactions, shares indirectly held by funds were 2,309,035 for Atlas Venture Fund XI, L.P. and 686,567 for Atlas Venture Opportunity Fund II, L.P., as reported.
Sionna Therapeutics (SION) director reported open‑market sales of common stock executed under Rule 10b5‑1 trading plans. The filings list multiple sales on 10/16/2025, 10/17/2025, and 10/20/2025 at weighted average prices disclosed for each tranche.
Examples include 73,296 shares at $32.84 and 45,117 shares at $31.69 by Atlas Venture Fund XI, L.P., and 15,384 shares at $32.84 and 9,470 shares at $31.69 by Atlas Venture Opportunity Fund II, L.P. Following the reported transactions, Atlas Venture Fund XI, L.P. held 2,382,495 shares and Atlas Venture Opportunity Fund II, L.P. held 701,985 shares, each reported as indirect holdings.
The footnotes state the plans were adopted on February 25, 2025 and that prices reflect weighted averages across ranges for each trade date.
Sionna Therapeutics (SION) — insider transaction update: The President & CEO, who also serves as a director, reported option exercises and corresponding open‑market sales under a Rule 10b5‑1 trading plan adopted on May 21, 2025.
On 10/15/2025, 14,775 shares were acquired via option exercise at $6.11 and sold the same day at a weighted average price of $31.1108. On 10/16/2025, 10,225 shares were acquired via option exercise at $6.11 and sold at a weighted average price of $31.4612, and an additional 200 shares were exercised at $6.11 and sold at $34. Following these transactions, common stock beneficially owned directly was 547,343 shares. Derivative holdings show 152,942 non‑qualified stock options beneficially owned following the reported transactions.
Sionna Therapeutics (SION) disclosed insider activity on a Form 4. A director reported open‑market sales of common stock on 10/10, 10/13, 10/14, and 10/15/2025, executed under Rule 10b5‑1 trading plans adopted on February 25, 2025 by Atlas Venture Fund XI, L.P. and Atlas Venture Opportunity Fund II, L.P.
Examples: on 10/15, Atlas Venture Fund XI, L.P. sold 65,726 shares at a weighted average price of $30.37 (range $29.95–$30.94) and 30,032 shares at $31.12 (range $30.95–$31.30). Atlas Venture Opportunity Fund II, L.P. sold 13,795 shares at $30.37 and 6,303 shares at $31.12. Following the reported transactions, indirect holdings were 2,619,185 shares (Atlas Venture Fund XI, L.P.) and 751,664 shares (Atlas Venture Opportunity Fund II, L.P.).
Sionna Therapeutics, Inc. submitted a Form 144 reporting a proposed sale of 3,511 common shares with an aggregate market value of $99,536.85, representing part of the holder's holding against 44,139,823 shares outstanding. The filing names Merrill Lynch as the broker and lists an approximate sale date of 10/10/2025. The securities were acquired in a private placement on 03/04/2024 and paid for in cash.
The filing also discloses multiple securities sales by affiliated funds over the prior three months: Atlas Venture Opportunity Fund II and Atlas Venture Fund XI executed several transactions between 09/29/2025 and 10/06/2025, with individual gross proceeds ranging from $1,048.25 to $1,644,065.58. The filer certifies no undisclosed material adverse information and includes the standard Rule 144 attestation language.
Sionna Therapeutics filed a Form 144 notifying a proposed sale of 16,727 shares of common stock through Merrill Lynch on 10/10/2025 with an aggregate market value of $474,210.45. The shares were acquired in a private placement on 03/04/2024 and were paid for in cash. The filing also lists multiple open-market sales by affiliated funds in the prior three months, including several trades between 09/29/2025 and 10/06/2025 totaling tens of thousands of shares and gross proceeds in the low millions.
The filer certifies they know of no material nonpublic information and notes the statutory warning about false statements. The notice identifies Merrill Lynch as the broker and NASDAQ as the exchange for the planned sale.
Insider sales by a director were disclosed for Sionna Therapeutics (SION). The Form 4 shows Director Bruce Booth reported multiple sales under Rule 10b5-1 trading plans on 10/03/2025 and 10/06/2025
On 10/03/2025 the filing reports sales of 31,198 and 6,548 shares at a weighted price around $30. On 10/06/2025 it reports sales of 9,753 and 2,047 shares at a weighted price around $29.95. The reported beneficial ownership after the transactions is 2,780,301 shares held by Atlas Venture Fund XI, L.P. and 785,480 shares held by Atlas Venture Opportunity Fund II, L.P.
The filing notes the shares sold were held indirectly by the two Atlas Venture funds and that the reporting person disclaims beneficial ownership except for any pecuniary interest. The transactions were executed pursuant to trading plans adopted on 02/25/2025 and the Form is signed by an attorney-in-fact on 10/07/2025.
Sionna Therapeutics, Inc. (SION) filed a Form 144 reporting a proposed sale of 2,047 common shares through Merrill Lynch with an aggregate market value of $61,430.47. The filing lists total outstanding shares as 44,139,823, and an approximate sale date of 10/06/2025. The shares were acquired in a private placement on 03/04/2024 for cash.
The notice also discloses recent related sales by affiliated funds: Atlas Venture Opportunity Fund II and Atlas Venture Fund XI sold multiple blocks between 09/29/2025 and 10/03/2025, including a 54,637-share sale generating $1,644,065.58. The filer certifies no undisclosed material adverse information and includes the standard Rule 10b5-1 and signature attestations.