[144] Sionna Therapeutics, Inc. SEC Filing

Rhea-AI Filing Summary

Sionna Therapeutics (SION) reported a Form 144 notice showing a proposed sale of 25,000 common shares—about 0.057% of the 44,139,823 shares outstanding—via Morgan Stanley Smith Barney on 08/20/2025 on NASDAQ. The filer acquired the shares on 08/20/2025 by exercising stock options and paid cash for them. The aggregate market value of the proposed sale is listed as $537,000.00. The filing notes there were no reported sales in the prior three months. The filer certifies they are not aware of any undisclosed material adverse information and includes the standard Rule 144 and Rule 10b5-1 representations.

Positive

• Timely disclosure of proposed sale under Rule 144 demonstrates compliance with SEC reporting requirements
• Transaction funded in cash via option exercise, indicating the sale stems from exercised equity rather than other transfers
• No reported sales in prior three months for the account, suggesting this is not part of a recent pattern of selling

Negative

• Insider sale is disclosed, which some investors may view negatively despite its small size relative to outstanding shares

Insights

Securities Analyst

TL;DR: Routine insider option exercise followed by a small sale; immaterial to market capitalization.

The filing documents a contemporaneous exercise of stock options and a proposed sale of 25,000 shares valued at $537,000, representing roughly 0.06% of outstanding shares. This is a standard disclosure under Rule 144 and does not indicate prior open-market selling activity for this account in the past three months. From a market-impact perspective, the size is small relative to the company’s outstanding shares so near-term price impact is likely limited.

Corporate Governance Expert

TL;DR: Compliance-focused filing showing timely disclosure of insider exercise and planned sale; governance process appears followed.

The notice shows the filer exercised options and intends to sell the resulting shares through Morgan Stanley Smith Barney, with cash payment at acquisition. The form includes the required certification about absence of undisclosed material information and mentions Rule 10b5-1 considerations. This is consistent with standard insider reporting practices and indicates procedural adherence to disclosure rules.

Form 144 Filer Information	UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 Form 144 NOTICE OF PROPOSED SALE OF SECURITIES PURSUANT TO RULE 144 UNDER THE SECURITIES ACT OF 1933
FORM 144

144: Filer Information

Filer CIK
Filer CCC
Is this a LIVE or TEST Filing?	LIVE TEST
Submission Contact Information
Name
Phone
E-Mail Address

144: Issuer Information

Name of Issuer

SEC File Number

Address of Issuer

Phone

Name of Person for Whose Account the Securities are To Be Sold

See the definition of "person" in paragraph (a) of Rule 144. Information is to be given not only as to the person for whose account the securities are to be sold but also as to all other persons included in that definition. In addition, information shall be given as to sales by all persons whose sales are required by paragraph (e) of Rule 144 to be aggregated with sales for the account of the person filing this notice.

Relationship to Issuer

Relationship to Issuer

144: Securities Information

Title of the Class of Securities To Be Sold	Name and Address of the Broker	Number of Shares or Other Units To Be Sold	Aggregate Market Value	Number of Shares or Other Units Outstanding	Approximate Date of Sale	Name the Securities Exchange
Common	Morgan Stanley Smith Barney LLC Executive Financial Services 1 New York Plaza 8th Floor New York NY 10004	25000	537000.00	44139823	08/20/2025	NASDAQ

Furnish the following information with respect to the acquisition of the securities to be sold and with respect to the payment of all or any part of the purchase price or other consideration therefor:

144: Securities To Be Sold

Title of the Class	Date you Acquired	Nature of Acquisition Transaction	Name of Person from Whom Acquired	Is this a Gift?	Date Donor Acquired	Amount of Securities Acquired	Date of Payment	Nature of Payment *
Common	08/20/2025	Exercise of Stock Options	Issuer			25000	08/20/2025	Cash

* If the securities were purchased and full payment therefor was not made in cash at the time of purchase, explain in the table or in a note thereto the nature of the consideration given. If the consideration consisted of any note or other obligation, or if payment was made in installments describe the arrangement and state when the note or other obligation was discharged in full or the last installment paid.

Furnish the following information as to all securities of the issuer sold during the past 3 months by the person for whose account the securities are to be sold.

144: Securities Sold During The Past 3 Months

Nothing to Report

144: Remarks and Signature

Remarks

Date of Notice

Date of Plan Adoption or Giving of Instruction, If Relying on Rule 10b5-1

ATTENTION:

The person for whose account the securities to which this notice relates are to be sold hereby represents by signing this notice that he does not know any material adverse information in regard to the current and prospective operations of the Issuer of the securities to be sold which has not been publicly disclosed. If such person has adopted a written trading plan or given trading instructions to satisfy Rule 10b5-1 under the Exchange Act, by signing the form and indicating the date that the plan was adopted or the instruction given, that person makes such representation as of the plan adoption or instruction date.

Signature

ATTENTION: Intentional misstatements or omission of facts constitute Federal Criminal Violations (See 18 U.S.C. 1001)

FAQ

What does Form 144 filed by SION mean?

Form 144 notifies the market of a proposed sale of restricted or control securities; here it shows a proposed sale of 25,000 SION shares.

When is the SION sale expected to occur?

The filing lists the approximate date of sale as 08/20/2025 on NASDAQ through Morgan Stanley Smith Barney.

How were the 25,000 shares acquired?

The shares were acquired on 08/20/2025 by an exercise of stock options and payment was made in cash.

How large is the proposed sale relative to Sionna's shares outstanding?

The 25,000 shares represent about 0.057% of the 44,139,823 shares outstanding reported in the filing.

What is the aggregate market value of the proposed sale?

The filing lists an aggregate market value of $537,000.00 for the 25,000 shares.