[Form 3] Sionna Therapeutics, Inc. Initial Statement of Beneficial Ownership

Rhea-AI Filing Summary

Sionna Therapeutics, Inc. (SION) filed an Initial Statement of Beneficial Ownership (Form 3) for Caroline Stark Beer, who is identified as the company's Chief Business Officer and an officer/director. The form shows the reportable event date of 10/01/2025 and is signed on 10/03/2025. The filing explicitly states: No securities are beneficially owned by the reporting person, and no non‑derivative or derivative holdings are reported.

SEC Form 3

FORM 3

UNITED STATES SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549

INITIAL STATEMENT OF BENEFICIAL OWNERSHIP OF SECURITIES

Filed pursuant to Section 16(a) of the Securities Exchange Act of 1934
or Section 30(h) of the Investment Company Act of 1940

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1. Name and Address of Reporting Person^*

Beer Caroline Stark

(Last) (First) (Middle)

C/O SIONNA THERAPEUTICS, INC.

21 HICKORY DRIVE, SUITE 500

(Street)

WALTHAM MA 02451

(City) (State) (Zip)

2. Date of Event Requiring Statement (Month/Day/Year)
10/01/2025

3. Issuer Name and Ticker or Trading Symbol
Sionna Therapeutics, Inc. [ SION ]

4. Relationship of Reporting Person(s) to Issuer
(Check all applicable)

	Director		10% Owner
X	Officer (give title below)		Other (specify below)
	Chief Business Officer

5. If Amendment, Date of Original Filed (Month/Day/Year)

6. Individual or Joint/Group Filing (Check Applicable Line)

X	Form filed by One Reporting Person
	Form filed by More than One Reporting Person

Table I - Non-Derivative Securities Beneficially Owned
1. Title of Security (Instr. 4)	2. Amount of Securities Beneficially Owned (Instr. 4)	3. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	4. Nature of Indirect Beneficial Ownership (Instr. 5)

Table II - Derivative Securities Beneficially Owned (e.g., puts, calls, warrants, options, convertible securities)
1. Title of Derivative Security (Instr. 4)	2. Date Exercisable and Expiration Date (Month/Day/Year)		3. Title and Amount of Securities Underlying Derivative Security (Instr. 4)		4. Conversion or Exercise Price of Derivative Security	5. Ownership Form: Direct (D) or Indirect (I) (Instr. 5)	6. Nature of Indirect Beneficial Ownership (Instr. 5)
	Date Exercisable	Expiration Date	Title	Amount or Number of Shares

Explanation of Responses:

No securities are beneficially owned.

	Jennifer Fitzpatrick, Attorney-in-Fact	10/03/2025
	** Signature of Reporting Person	Date
Reminder: Report on a separate line for each class of securities beneficially owned directly or indirectly.
* If the form is filed by more than one reporting person, see Instruction 5 (b)(v).
** Intentional misstatements or omissions of facts constitute Federal Criminal Violations See 18 U.S.C. 1001 and 15 U.S.C. 78ff(a).
Note: File three copies of this Form, one of which must be manually signed. If space is insufficient, see Instruction 6 for procedure.
Persons who respond to the collection of information contained in this form are not required to respond unless the form displays a currently valid OMB Number.

FAQ

What does the SION Form 3 filed by Caroline Stark Beer disclose?

The filing identifies Caroline Stark Beer as Chief Business Officer and states that she beneficially owns no securities of Sionna Therapeutics as of 10/01/2025.

When was the Form 3 event date and signature date for the SION filing?

The event date reported is 10/01/2025 and the form is signed by an attorney‑in‑fact on 10/03/2025.

Does the Form 3 list any stock options, warrants, or other derivative securities for SION?

No. The filing contains no entries in Table I or Table II and states No securities are beneficially owned.

Is the Form 3 a joint filing or filed by a single reporting person?

The form indicates it was filed by one reporting person.

Who signed the Form 3 for Caroline Stark Beer?

The form is signed by Jennifer Fitzpatrick, Attorney‑in‑Fact on 10/03/2025.