[144] Sionna Therapeutics, Inc. SEC Filing

Rhea-AI Filing Summary

Sionna Therapeutics (SION) Form 144 shows a proposed sale of 25,000 common shares through Morgan Stanley Smith Barney LLC with an aggregate market value of $601,500. The securities were acquired and are scheduled for sale on 08/26/2025 following an exercise of stock options paid in cash. The filing also records a prior Rule 10b5-1 sale of 25,000 shares on 08/20/2025 that generated $568,715 in gross proceeds. The filing lists total shares outstanding as 44,139,823. The notice includes the standard attestation that the seller does not possess undisclosed material adverse information and references reliance on a 10b5-1 plan where applicable.

Insights

Securities Analyst

TL;DR: Insider exercised options and plans to sell 25,000 shares; transaction size is small relative to outstanding stock.

The filing documents an option exercise and proposed sale of 25,000 SION common shares on 08/26/2025 via Morgan Stanley Smith Barney LLC at an aggregate market value of $601,500. With 44,139,823 shares outstanding, the position represents a de minimis fraction of the equity base. A prior 10b5-1 sale of 25,000 shares on 08/20/2025 produced $568,715, indicating recent liquidity events by the same account. This disclosure is routine for insiders exercising and liquidating option-derived shares and, based on the quantities reported, is unlikely by itself to be materially informative for valuation.

Corporate Governance Expert

TL;DR: Proper procedural disclosure appears made; seller attests to absence of undisclosed material information.

The Form 144 includes the required attestation regarding material non-public information and references a Rule 10b5-1 instruction for prior sales. The record shows acquisition and sale on the same date (08/26/2025) via exercise of stock options with cash payment, which is a common insider liquidity event. Documentation of broker and transaction dates is present, supporting compliance with Rule 144 notice requirements. No governance red flags or departures from standard disclosure practices are apparent within the filing content provided.

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	601500.00	44139823	08/26/2025	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	08/26/2025	Exercise of Stock Options	Issuer			25000	08/26/2025	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

Name and Address of Seller	Title of Securities Sold	Date of Sale	Amount of Securities Sold	Gross Proceeds
10b5-1 Sales for MICHAEL CLOONAN 21 Hickory Drive, Suite 500 Waltham MA 02451	Common	08/20/2025	25000	568715.00

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 shares does the Form 144 for SION report?

The filing reports a proposed sale of 25,000 common shares.

When is the proposed sale date listed in the SION Form 144?

The approximate date of sale is listed as 08/26/2025.

How many shares outstanding does the filing show for Sionna Therapeutics (SION)?

The filing lists 44,139,823 shares outstanding.

How were the 25,000 shares acquired according to the filing?

They were acquired on 08/26/2025 by exercise of stock options and paid in cash.

Did the filer make any recent 10b5-1 sales prior to this Form 144?

Yes, a 10b5-1 sale of 25,000 shares occurred on 08/20/2025 generating $568,715 gross proceeds.