ORBIMED ADVISORS LLC - 07 Jul 2026 Form 4 Insider Report for Sionna Therapeutics, Inc. (SION)

Reporting relationship: Director
Issuer ticker: SION
Reported as of: 07 Jul 2026
Net transaction value: -$3,854,281
SEC form: 4
Accepted by SEC: 09 Jul 2026, 16:44:00 UTC
Prior SEC filing: 02 Jul 2026
Next SEC filing: 23 Jul 2026
Source filing: View source filing
Reporting owner signature: /s/ Carl L. Gordon, Member of OrbiMed Advisors LLC

Key filing fact

ORBIMED ADVISORS LLC filed Form 4 for Sionna Therapeutics, Inc. (SION) on 09 Jul 2026.

Key facts

This page summarizes ORBIMED ADVISORS LLC's Form 4 filing for Sionna Therapeutics, Inc. (SION).
1 reported transaction and 0 derivative rows are listed below.
Accepted by SEC: 09 Jul 2026, 16:44.

Change

Previous filing in this sequence was filed on 02 Jul 2026.
Current net transaction value: -$3,854,281.

Research use

This tells you what this filing adds before you inspect full transaction and derivative tables.
You can trace every row back to the original SEC filing document.

Evidence

Filed on Form 4

Ownership activity is grounded in SEC Form 4 disclosures.

View source filing

Reporting Owners (2)

CIK 0001055951 Primary reporting owner

ORBIMED ADVISORS LLC

Relationship: Director
Address: 601 LEXINGTON AVENUE, 54TH FLOOR, NEW YORK
Signature: /s/ Carl L. Gordon, Member of OrbiMed Advisors LLC
Signature date: 09 Jul 2026

CIK 0001845804

OrbiMed Capital GP VIII LLC

Relationship: Director
Address: 601 LEXINGTON AVENUE, 54TH FLOOR, NEW YORK
Signature: /s/ Carl L. Gordon, Member of OrbiMed Capital GP VIII LLC
Signature date: 09 Jul 2026

Reported non-derivative transactions

Shares, units, or other non-derivative securities reported in this filing.

SION transaction

Common Stock

Sale

Transaction value: $3,854,281
Shares: -85,918
Change %: -3.4%
Price: $44.86
Shares after: 2,469,959
Date: 07 Jul 2026
Ownership: See footnotes
Footnotes: F1, F2, F3

SION transaction

Common Stock

Sale

Transaction value: $3,854,281
Shares: -85,918
Change %: -3.4%
Price: $44.86
Shares after: 2,469,959
Date: 07 Jul 2026
Ownership: See footnotes
Footnotes: F1, F2, F3

^* marks a reported price that did not pass the local price check.

Additional SEC filing notes

Filing notes and footnotes

Rule 10b5-1 trading plan

These transactions were reported as open-market trades under a Rule 10b5-1 plan. The plan lets an insider set trading instructions in advance, which can reduce the risk of trading while in possession of material nonpublic information.

Original filing language: transaction made pursuant to a contract, instruction, or written plan intended to satisfy Rule 10b5-1(c).

Explanation of responses 3 footnotes

Footnote F1

These securities were sold pursuant to a 10b5-1 plan.

Footnote F2

These securities are held of record by OrbiMed Private Investments VIII, LP ("OPI VIII"). OrbiMed Capital GP VIII LLC ("GP VIII") is the general partner of OPI VIII and OrbiMed Advisors LLC ("OrbiMed Advisors") is the managing member of GP VIII. By virtue of such relationships, GP VIII and OrbiMed Advisors may be deemed to have voting and investment power with respect to the shares held by OPI VIII and as a result may be deemed to have beneficial ownership of such shares. OrbiMed Advisors exercises investment and voting power through a management committee comprised of Carl L. Gordon, Sven H. Borho, and W. Carter Neild, each of whom disclaims beneficial ownership of the shares held by OPI VIII.

Footnote F3

This report on Form 4 is jointly filed by OrbiMed Advisors and GP VIII. Each of the Reporting Persons disclaims beneficial ownership of the securities reported herein for purposes of Rule 16a-1(a) under the Securities Exchange Act of 1934, as amended (the "Exchange Act"), except to the extent of its pecuniary interest therein, if any. The Reporting Persons have designated a representative, Peter A. Thompson, a member of OrbiMed Advisors, to serve on the Issuer's board of directors. This report shall not be deemed an admission that any such entity or person is a beneficial owner of such securities for purposes of Section 16 of the Exchange Act, or for any other purpose.