Form 8-K

8-K — Sionna Therapeutics, Inc.

Accession: 0001628280-26-053832

Filed: 2026-08-06

Period: 2026-08-06

CIK: 0002036042

SIC: 2834 (PHARMACEUTICAL PREPARATIONS)

Item: Results of Operations and Financial Condition

Item: Financial Statements and Exhibits

Documents

8-K — sion-20260806.htm (Primary)

EX-99.1 (sion2q26earningsrelease_fi.htm)

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8-K

8-K (Primary)

Filename: sion-20260806.htm · Sequence: 1

sion-20260806

0002036042FALSE00020360422026-08-062026-08-06

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): August 06, 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 August 6, 2026, Sionna Therapeutics, Inc. issued a press release announcing its financial results and business highlights for the quarter ended June 30, 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 August 6, 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: August 06, 2026

By: /s/ Jennifer Fitzpatrick

Name: Jennifer Fitzpatrick

Title: Chief Legal Officer

EX-99.1

Filename: sion2q26earningsrelease_fi.htm · Sequence: 2

Document

Sionna Therapeutics Reports Second Quarter 2026 Financial Results

PreciSION CF Phase 2a proof-of-concept trial evaluating NBD1 stabilizer SION-719 as an add-on to standard of care is on track for topline data summer of 2026

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

Maintained strong cash position with $268.3 million in cash and cash equivalents, expected to fund operations into 2028

WALTHAM, Mass., Aug 6, 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 second quarter ended June 30, 2026, and provided a business update.

“We continued to advance our clinical NBD1 stabilizer programs during the second quarter as we approach two important clinical milestones this summer,” said Mike Cloonan, President and Chief Executive Officer of Sionna. “We remain focused on execution and delivering topline data from both our Phase 2a proof-of-concept trial and our Phase 1 dual combination trial. Together, these studies have the potential to further validate our core belief that directly stabilizing NBD1 is central to restoring CFTR function and transforming the treatment paradigm for people living with cystic fibrosis."

Pipeline Updates

•PreciSION CF Phase 2a Proof-of-Concept Trial with SION-719 Is On Track: The PreciSION CF Phase 2a proof-of-concept (POC) trial (NCT07108153) is evaluating SION-719 as an add-on to standard of care (SOC) in CF participants. 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. In April 2026, Sionna announced it had completed enrollment. Topline data from this trial are on track for this summer.

•Phase 1 Dual Combination Trial with SION-451 and Complementary Modulators Is 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 on track for this summer.

•Presented Encore Data at 49th European Cystic Fibrosis Conference: In June 2026, Sionna presented encore clinical and nonclinical data at the 49th European Cystic Fibrosis Conference (ECFS) in Lisbon, Portugal. Presentations highlighted previously reported Phase 1 data for the Company's clinical-stage NBD1 stabilizers, SION-719 and SION-451, and nonclinical data demonstrating the potential of NBD1 stabilizers to increase F508del-CFTR protein half-life up to wild-type levels when used alone or in combination with complementary CFTR modulators. The same data will also be presented at the 16th Australasian Cystic Fibrosis Conference taking place August 7th-9th in Geelong, Australia.

Financial Results for the Quarter Ended June 30, 2026

Research and Development Expenses: Research and development expenses were $21.9 million for the second quarter of 2026, compared to $15.4 million for the second 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 second quarter of 2026, compared to $6.5 million for the second 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 $29.9 million for the second quarter of 2026, compared to a net loss of $18.1 million for the second quarter of 2025.

Cash and Cash Equivalents: Cash, cash equivalents and marketable securities totaled $268.3 million as of June 30, 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 participants; 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 nonclinical 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 nonclinical 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; the competitive landscape for CF treatments, including existing therapies; 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.

Investor Contact

Juliet Labadorf

ir@sionnatx.com

Media Contact

Sarah Spencer

media@sionnatx.com

Sionna Therapeutics, Inc.

Consolidated Statements of Operations

(In thousands, except per share data)

(Unaudited)

Three Months Ended

Six Months Ended

June 30,

2026

2025

2026

2025

Operating expenses:

Research and development

21,864

15,383

40,827

29,051

General and administrative

10,606

6,523

21,242

12,514

Total operating expenses

32,470

21,906

62,069

41,565

Loss from operations

(32,470)

(21,906)

(62,069)

(41,565)

Other income:

Interest income

2,587

3,667

5,407

6,667

Other income (expense), net

(3)

171

(3)

348

Total other income

2,584

3,838

5,404

7,015

Net loss

(29,886)

(18,068)

(56,665)

(34,550)

Net loss per share, basic and diluted

(0.66)

(0.41)

(1.25)

(0.98)

Weighted-average common shares outstanding, basic and diluted

45,148,971

44,116,997

45,306,105

35,404,928

Sionna Therapeutics, Inc.

Selected Consolidated Balance Sheet Data

(In thousands)

(Unaudited)

June 30,

December 31,

2026

2025

Cash, cash equivalents, and marketable securities

268,253

310,302

Working capital1

205,348

229,707

Total assets

283,249

325,953

Total stockholders’ equity

265,775

306,833

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

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