Form 8-K

8-K — Sionna Therapeutics, Inc.

Accession: 0001628280-26-033870

Filed: 2026-05-12

Period: 2026-05-12

CIK: 0002036042

SIC: 2834 (PHARMACEUTICAL PREPARATIONS)

Item: Results of Operations and Financial Condition

Item: Financial Statements and Exhibits

Documents

8-K — sion-20260512.htm (Primary)

EX-99.1 (sion1q26earningsrelease_fi.htm)

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8-K

8-K (Primary)

Filename: sion-20260512.htm · Sequence: 1

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0002036042FALSE00020360422026-05-122026-05-12

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

__________________________

FORM 8-K

__________________________

CURRENT REPORT

Pursuant to Section 13 or 15(d)

of the Securities Exchange Act of 1934

Date of Report (date of earliest event reported): May 12, 2026

__________________________

SIONNA THERAPEUTICS, INC.

(Exact name of registrant as specified in its charter)

__________________________

Delaware 001-42504 84-2801521

(State or other jurisdiction

of incorporation) (Commission

File Number) (I.R.S. Employer

Identification No.)

SIONNA THERAPEUTICS, INC.

21 Hickory Drive, Suite 500

Waltham, MA02451

(Address of principal executive offices, including zip code)

617-819-2020

(Registrant’s telephone number, including area code)

Not Applicable

(Former Name or Former Address, if Changed Since Last Report)

__________________________

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☐ Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐ Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐ Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐ Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class Trading

Symbol(s) Name of each exchange

on which registered

Common Stock, $0.001 par value per share SION The Nasdaq Global Market

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company x

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. o

Item 2.02 Results of Operations and Financial Condition.

On May 12, 2026, Sionna Therapeutics, Inc. issued a press release announcing its financial results and business highlights for the three months ended March 31, 2026. The full text of the press release is furnished as Exhibit 99.1 to this Current Report on Form 8-K.

The information set forth under this Item 2.02 and in Exhibit 99.1 attached hereto is intended to be furnished and shall not be deemed “filed” for purposes of Section 18 of the Securities Exchange Act of 1934, as amended (the “Exchange Act”), or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933 or the Exchange Act, except as expressly set forth by specific reference in such filing.

Item 9.01 Financial Statements and Exhibits.

(d) Exhibits

99.1

Press Release of Sionna Therapeutics, Inc. dated May 12, 2026.

104 Cover Page Interactive Data File (embedded within the Inline XBRL document).

SIGNATURE

Pursuant to the requirements of the Securities Exchange Act of 1934, as amended, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

Sionna Therapeutics, Inc.

Date: May 12, 2026

By: /s/ Jennifer Fitzpatrick

Name: Jennifer Fitzpatrick

Title: Chief Legal Officer

EX-99.1

Filename: sion1q26earningsrelease_fi.htm · Sequence: 2

Document

Sionna Therapeutics Reports First Quarter 2026 Financial Results

Enrollment completed in the PreciSION CF Phase 2a proof-of-concept trial evaluating NBD1 stabilizer SION-719 as an add-on to standard of care in participants with cystic fibrosis; topline data on track for the summer of 2026

Ongoing Phase 1 trial evaluating NBD1 stabilizer SION-451 in proprietary dual combinations with SION-2222 and with SION-109 in healthy volunteers is also on track for topline data in the summer of 2026

Maintained strong cash position with approximately $289.9 million in cash and cash equivalents, expected to fund operations into 2028

WALTHAM, Mass., May 12, 2026 (GLOBE NEWSWIRE) – Sionna Therapeutics, Inc. (Nasdaq: SION), a clinical-stage biopharmaceutical company on a mission to revolutionize the current treatment paradigm for cystic fibrosis (CF) today reported financial results for the first quarter ended March 31, 2026, and provided a business update.

“We entered 2026 with strong execution across our programs, highlighted by the recent completion of enrollment in our proof-of-concept Phase 2a trial of SION-719, an important milestone for Sionna,” said Mike Cloonan, President and Chief Executive Officer of Sionna. “With both of our clinical stage NBD1 stabilizer programs on track for topline readouts this summer, we remain focused on advancing these first-in-class product candidates that could expand therapeutic options for people with CF.”

Pipeline Updates

NBD1 Stabilizers

•Enrollment Completed in PreciSION CF Phase 2a Proof-of-Concept Trial with SION-719; Topline Data On Track: In April 2026, Sionna announced it had completed enrollment in the PreciSION CF Phase 2a proof-of-concept (POC) trial (NCT07108153) evaluating SION-719 as an add-on to standard of care (SOC) in CF patients. The trial is evaluating the safety, tolerability, and pharmacokinetics (PK) of SION-719 when administered with SOC and assessing change in CFTR function as measured by sweat chloride levels. Topline data from this trial are anticipated in the summer of this year.

•Ongoing Phase 1 Dual Combination Trial with SION-451 and Complementary Modulators; Topline Data On Track: The Phase 1 trial (NCT07035990) is evaluating SION-451 in proprietary dual combinations with SION-2222 (galicaftor), a transmembrane domain 1 (TMD1)-directed CFTR corrector, and with SION-109, an intracellular loop 4 (ICL4)-directed CFTR corrector, in healthy volunteers. Topline data from this trial are anticipated in the summer of this year.

•Encore Data to be Presented at 49th European Cystic Fibrosis Conference: Encore data previously presented at the 2025 North American Cystic Fibrosis Conference (NACFC) will be featured in an oral and ePoster presentation at the European Cystic Fibrosis Society’s (ECFS) 49th European Cystic Fibrosis Conference, being held June 3-6, 2026, in Lisbon, Portugal.

Details of the presentations are as follows:

Abstract Title: Safety, tolerability, and pharmacokinetics of novel NBD1 stabilizers SION-719 and SION-451 from two Phase 1 first-in-human studies

Abstract number: EPS07.01

Presenting Author: Jason H. Maley, MD, MS, Senior Director, Clinical Development, Sionna Therapeutics

Oral ePoster Session Title: Old and new – exploring the portfolio for CF treatment

Date and Time: Friday, June 5, 2026, 2:00-2:06 p.m. CEST/9:00-9:06 a.m. ET

Abstract Title: Clinical-stage NBD1 stabilizers can increase F508del-CFTR protein half-life to wild-type levels when used alone or in combination with other CFTR modulators

Abstract ID: WS15.3

Presenting Author: Greg Hurlbut, Ph.D., Co-Founder and Senior Vice President, Discovery Research, Sionna Therapeutics

Session Title: Workshop 15: Novel approaches, future therapies

Date and Time: Friday, June 5, 2026, 5:30-5:45 p.m. CEST/11:30-11:45 a.m. ET

Financial Results for the Quarter Ended March 31, 2026

Research and Development Expenses: Research and development expenses were $19.0 million for the first quarter of 2026, compared to $13.7 million for the first quarter of 2025. These increases were mainly driven by development expenses to support the advancement of Sionna’s clinical pipeline and personnel-related costs, including stock-based compensation expenses, to support the Company’s continued growth and operational activities.

General and Administrative Expenses: General and administrative expenses were $10.6 million for the first quarter of 2026, compared to $6.0 million for the first quarter of 2025. These increases were primarily due to personnel-related costs, including stock-based compensation expenses, to support the Company’s continued growth and operational activities.

Net Loss: Net loss was $26.8 million for the first quarter of 2026, compared to a net loss of $16.5 million for the first quarter of 2025.

Cash and Cash Equivalents: Cash, cash equivalents and marketable securities totaled $289.9 million as of March 31, 2026. Sionna expects its current cash position to fund operations into 2028.

About Sionna Therapeutics

Sionna Therapeutics is a clinical-stage biopharmaceutical company on a mission to revolutionize the current treatment paradigm for cystic fibrosis (CF) by developing novel medicines that normalize the function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein. Sionna’s goal is to deliver differentiated medicines for people living with CF that can restore their CFTR function to as close to normal as possible by directly stabilizing CFTR’s nucleotide binding domain 1 (NBD1), which Sionna believes is central to potentially unlocking dramatic improvements in clinical outcomes and quality of life for people with CF. Leveraging more than a decade of the co-founders’ research on NBD1, Sionna is advancing a pipeline of small molecules engineered to correct the defects caused by the F508del genetic mutation, which occurs in NBD1. Sionna is also developing a portfolio of complementary CFTR

modulators that are designed to work synergistically with its NBD1 stabilizers to improve CFTR function. For more information about Sionna, visit www.sionnatx.com.

Sionna intends to use its Investor Relations website as a means of disclosing material nonpublic information and for complying with its disclosure obligations under Regulation FD. Accordingly, investors should monitor Sionna’s Investor Relations website, in addition to following Sionna’s press releases, SEC filings, public conference calls, presentations, and webcasts.

Cautionary Note Regarding Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995, as amended, including, without limitation, implied and express statements about Sionna’s beliefs and expectations regarding: its goal of transforming the treatment paradigm for CF and providing clinically meaningful benefit for CF patients; the potential of Sionna’s product candidates to expand therapeutic options for people with CF; the initiation, timing, progress and results of Sionna’s research and development programs, clinical trials and studies, including the timing of topline data from Sionna’s Phase 2a proof-of-concept trial and Phase 1 dual combination trial; the ability of clinical trials to demonstrate safety and efficacy of Sionna’s product candidates; the ability of Sionna’s preclinical studies or earlier clinical trials to predict later clinical trial results; and financial projections and expectations regarding the time period in which Sionna’s capital resources will be sufficient to fund its anticipated operations, including cash runway, use of capital, expenses and other financial results. In some cases, the forward-looking statements can be identified by terms such as “may,” “will,” “should,” “would,” “expect,” “plan,” “anticipate,” “could,” “intend,” “target,” “project,” “believe,” “estimate,” “predict,” “potential” or “continue” or the negative of these terms or other similar expressions. Any forward-looking statements in this press release are based on management’s current expectations and beliefs and are subject to a number of risks, uncertainties and important factors that may cause actual events or results to differ materially from those expressed or implied by the forward-looking statements contained in this press release. Factors that could cause actual results to differ include, but are not limited to, risks and uncertainties inherent in the development of product candidates, including uncertainties concerning the initiation, timing, progress, and results of Sionna’s ongoing, planned and future clinical trials and studies; the Company’s ability to replicate positive results from earlier preclinical studies or clinical trials in current or future clinical trials; Sionna’s ability to demonstrate that its NBD1 stabilizers, complementary CFTR modulators, and any potential future product candidates are safe and effective for their proposed indications; regulatory developments in the United States and foreign countries; and general economic, industry and market conditions. These risks and uncertainties are described in the section entitled “Risk Factors” in Sionna’s most recent Annual Report on Form 10-K as well as any subsequent filings with the Securities and Exchange Commission. The events and circumstances reflected in the forward-looking statements may not be achieved or occur. In addition, any forward-looking statements represent Sionna’s views only as of today and should not be relied upon as representing its views as of any subsequent date. Sionna explicitly disclaims any obligation to update any forward-looking statements except as required by law. No representations or warranties (expressed or implied) are made about the accuracy of any such forward-looking statements.

Media Contact

Sarah Spencer

media@sionnatx.com

Investor Contact

Juliet Labadorf

ir@sionnatx.com

Three Months Ended

March 31,

2026

2025

Operating expenses:

Research and development

18,963

13,668

General and administrative

10,636

5,991

Total operating expenses

29,599

19,659

Loss from operations

(29,599)

(19,659)

Other income:

Interest income

2,820

3,000

Other income

177

Total other income

2,820

3,177

Net loss

(26,779)

(16,482)

Net loss per share, basic and diluted

(0.60)

(0.62)

Weighted-average common shares outstanding, basic and diluted

44,921,984

26,596,059

Sionna Therapeutics, Inc.

Selected Consolidated Balance Sheet Data

(In thousands)

(Unaudited)

March 31,

December 31,

2026

2025

Cash, cash equivalents, and marketable securities

289,931

310,302

Working capital1

211,183

229,707

Total assets

305,039

325,953

Total stockholders’ equity

288,208

306,833

1Sionna defines working capital as current assets minus current liabilities.

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