Sionna Therapeutics, Inc.

UNITED STATES

SECURITIES AND EXCHANGE COMMISSION

Washington, D.C. 20549

FORM 10-Q

(Mark One)

For the quarterly period ended June 30, 2026

OR

For the transition period from _____ to _____

Commission file number 001-42504

(Exact name of registrant as specified in its charter)

(617)819-2020

Registrant’s telephone number, including area code

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

Indicate by check mark whether the registrant (1) has filed all reports required to be filed by Section 13 or 15(d) of the Securities Exchange Act of 1934 during the preceding 12 months (or for such shorter period that the registrant was required to file such reports), and (2) has been subject to such filing requirements for the past 90 days. Yes x Noo

Indicate by check mark whether the registrant has submitted electronically every Interactive Data File required to be submitted pursuant to Rule 405 of Regulation S-T (§ 232.405 of this chapter) during the preceding 12 months (or for such shorter period that the registrant was required to submit such files). Yes x Noo

Indicate by check mark whether the registrant is a large accelerated filer, an accelerated filer, a non-accelerated filer, a smaller reporting company, or an emerging growth company. See the definitions of “large accelerated filer,” “accelerated filer,” “smaller reporting company,” and "emerging growth company" in Rule 12b-2 of the Exchange Act.

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

Indicate by check mark whether the registrant is a shell company (as defined in Rule 12b-2 of the Act). Yeso Nox

The number of shares of registrant’s common stock outstanding as of July 31, 2026 was 45,212,399.

CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS

This Quarterly Report on Form 10-Q (the “Quarterly Report”) contains forward-looking statements about us and our industry that involve substantial risks and uncertainties, and which are made pursuant to the safe harbor provisions of Section 27A of the Securities Act of 1933, as amended (the “Securities Act”) and Section 21E of the Securities Exchange Act of 1934, as amended (the “Exchange Act”). All statements other than statements of historical facts contained in this Quarterly Report, including statements regarding our future results of operations and financial position, business strategy, product candidates, preclinical studies and clinical trials, results of preclinical studies and clinical trials, research and development costs, regulatory approvals, commercial strategy, timing and likelihood of success, as well as plans and objectives of management for future operations, are forward-looking statements. Although we believe that the expectations reflected in these forward-looking statements are reasonable, these statements involve known and unknown risks, uncertainties and other important factors that are in some cases beyond our control and may cause our actual results, performance or achievements to be materially different from any future results, performance or achievements expressed or implied by the forward-looking statements.

In some cases, you can identify forward-looking statements 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. Forward-looking statements contained in this Quarterly Report include, but are not limited to, statements about:

•the initiation, timing, progress and results of our research and development programs, preclinical studies and clinical trials;

•the ability of clinical trials to demonstrate safety and efficacy of our product candidates, and other positive results, and the ability of our earlier clinical trials and preclinical studies to predict later clinical trial results;

•the timing, scope and likelihood of regulatory filings and approvals of our product candidates;

•the implementation of our business model, and strategic plans for our business, programs, and current and future product candidates;

•our ability to obtain additional cash and the sufficiency of our existing cash, cash equivalents and investments in marketable securities to fund our future operating expenses and capital expenditure requirements;

•the accuracy of our estimates regarding expenses, future revenue, capital requirements and needs for additional financing;

•the size and growth potential of the markets for our product candidates, and our ability to serve those markets;

•our potential and ability to successfully manufacture and supply our current and future product candidates for clinical trials and for commercial use, if approved;

•the scope of protection we are able to establish and maintain for intellectual property rights covering our product candidates;

•developments relating to our competitors and our industry, including competing product candidates and therapies;

•existing regulations and regulatory developments in the U.S. and other jurisdictions, including changes in U.S. federal policy, such as trade policies or tariffs;

•expectations regarding future events under collaboration and licensing agreements, including potential future payments, as well as our plans and strategies for entering into further collaboration and licensing agreements;

•general economic, industry and market conditions, including elevated interest rates and inflation;

•our ability to attract and retain the continued service of our key personnel and to identify, hire and then retain additional qualified personnel;

•our expectations regarding the period during which we will qualify as an emerging growth company under the Jumpstart Our Business Startups Act of 2012, as amended (the "JOBS Act");

•our expectations regarding the period during which we will qualify as a "smaller reporting company" as defined by Rule 12b-2 of the Exchange Act; and

•our anticipated use of our existing cash, cash equivalents and investments in marketable securities.

We have based these forward-looking statements largely on our current expectations and projections about our business, the industry in which we operate and financial trends that we believe may affect our business, financial condition, results of operations and prospects, and these forward-looking statements are not guarantees of future performance or development. These forward-looking statements speak only as of the date of this Quarterly Report and are subject to a number of risks, uncertainties and assumptions described in the section entitled “Risk Factors” and elsewhere in this Quarterly Report. Because forward-looking statements are inherently subject to risks and uncertainties, some of which cannot be predicted or quantified, you should not rely on these forward-looking statements as predictions of future events. The events and circumstances reflected in our forward-looking statements may not be achieved or occur and actual results could differ materially from those projected in the forward-looking statements. Except as required by applicable law, we do not plan to publicly update or revise any forward-looking statements contained herein, whether as a result of any new information, future events or otherwise.

In addition, statements that “we believe” and similar statements reflect our beliefs and opinions on the relevant subject. These statements are based upon information available to us as of the date of this Quarterly Report, and while we believe such information forms a reasonable basis for such statements, such information may be limited or incomplete, and our statements should not be read to indicate that we have conducted an exhaustive inquiry into, or review of, all potentially available relevant information. These statements are inherently uncertain, and you are cautioned not to unduly rely upon these statements.

You should read this Quarterly Report and the documents that we reference herein or incorporated by reference as exhibits hereto with the understanding that our actual future results, levels of activity, performance and events and circumstances may be materially different from what we expect.

NOTE REGARDING TRADEMARKS

Sionna Therapeutics, Inc. is the owner of the trademarks SIONNA and SIONNA THERAPEUTICS, as well as certain other trademarks, including design versions of some of these trademarks. The symbols ™ and ® are not used in connection with the presentation of these trademarks in this Quarterly Report and their absence does not indicate a lack of trademark rights. Certain other trademarks used in this Quarterly Report are the property of third-party trademark owners and may be presented with or without trademark symbols.

All brand names or trademarks appearing in this Quarterly Report are the property of their respective owners. Unless the context requires otherwise, references in this report to “Sionna,” the “Company,” “we,” “us” and “our” refer to Sionna Therapeutics, Inc. and its subsidiary.

SUMMARY OF MATERIAL RISKS ASSOCIATED WITH OUR BUSINESS

We are subject to numerous risks and uncertainties, including those further described below in the section entitled “Risk Factors” in this Quarterly Report, as well as in other documents that we file with the U.S. Securities and Exchange Commission (“SEC”). The following considerations, among others, may offset our competitive strengths or have a negative effect on our business strategy, which could materially adversely affect our business, financial conditions, results of operations and future growth prospects:

•We are a clinical-stage biopharmaceutical company and have incurred significant operating losses since inception and anticipate that we will continue to incur significant operating losses for the foreseeable future.

•We will need to raise substantial additional funding. We may be unable to raise capital on acceptable terms, if at all, and, as a result, we may be required to delay, reduce or eliminate our product development programs or future commercialization efforts.

•We are substantially dependent on the success of at least one of our nucleotide binding domain 1 ("NBD1") stabilizers. If we are unable to advance an NBD1 stabilizer product candidate into later-stage clinical development or unable to obtain regulatory approval and commercialize a product candidate, or experience significant delays in doing so, our business will be materially harmed.

•Targeting the NBD1 domain of the cystic fibrosis transmembrane conductance regulator protein is novel, and the time, cost of development and likelihood of successful product development is difficult to predict.

•We intend to develop a proprietary dual combination of an NBD1 stabilizer with a complementary modulator, and/or an NBD1 stabilizer as an add-on to the standard of care. Developing combination treatments increases complexity and risk, including risks of drug-drug interactions, unforeseen side effects or failures in our clinical trials that could delay or prevent their regulatory approval or limit the commercial profile of an approved label.

•We may incur additional costs and experience delays in completing, or ultimately be unable to complete, the development and commercialization of our product candidates.

•Positive results from our preclinical studies or prior clinical trials are not necessarily predictive of the results of later clinical trials of our current or future product candidates. If we cannot replicate the positive results from our earlier preclinical studies or clinical trials of our current or potential future product candidates, or if we suffer any other significant setbacks in our later clinical trials, we may be unable to successfully develop, obtain regulatory approval for and commercialize our current or potential future product candidates.

•Our preclinical studies and clinical trials may fail to demonstrate the safety and efficacy of our product candidates, or serious or unacceptable adverse side effects or unexpected toxicology findings may be identified during the development of our product candidates, which could prevent or delay further clinical development, regulatory approvals and commercialization, impact the product’s labeling, if approved, increase our costs or necessitate the abandonment or limitation of the development of some of our product candidates.

•We rely, and in the future expect to rely, on third parties to conduct our ongoing and planned clinical trials for our current and future product candidates. If these third parties do not successfully carry out their contractual duties, comply with regulatory requirements or meet expected deadlines, or if we experience delays or difficulties in the initiation of, or enrollment of patients in, clinical trials, obtaining necessary regulatory approvals could be delayed or prevented.

•The regulatory approval processes of the U.S. Food and Drug Administration and comparable foreign authorities are lengthy, time-consuming and inherently unpredictable. If we are not able to obtain the required regulatory approval for any product candidate, our business will be substantially harmed.

•We may not be successful in our efforts to identify or discover additional product candidates, or we may expend our limited resources to pursue a particular product candidate or indication and fail to capitalize on product candidates or indications that may be more profitable or for which there is a greater likelihood of success.

•We are dependent on licensed intellectual property. If we were to lose our rights to licensed intellectual property, we may not be able to continue developing or commercializing our product candidates, if approved. If we breach any of the agreements under which we license the use, development and commercialization rights to our product candidates from third parties or, in certain cases, we fail to meet certain development deadlines, we could lose license rights that are important to our business.

•We contract with third parties for the manufacture of our product candidates for clinical drug supply and expect to continue to do so for commercialization, if our product candidates are approved. This reliance on third parties increases the risk that we will not have sufficient quantities of our product candidates or obtain such quantities at an acceptable cost or quality, which could delay, prevent or impair our development or commercialization efforts.

•If we or our licensors are unable to obtain, maintain and enforce intellectual property rights relating to any of our product candidates, or if the scope of the protection obtained is not sufficiently broad, our competitors or other third parties could develop and commercialize products similar or identical to ours, our ability to successfully commercialize our product candidates may be adversely affected and we may not be able to compete effectively in our markets.

•We face substantial competition. Our main competitor in the CF market holds substantial market share and has substantially greater resources than we do. We may not be able to compete successfully in this environment and, in particular, against a much larger competitor.

•The trading price of the shares of our common stock may be volatile, and investors could lose all or part of their investment.

The summary risk factors described above should be read together with the text of the full risk factors in the section titled “Risk Factors” and the other information set forth in this Quarterly Report, as well as in other documents that we file with the SEC. The risks summarized above or described in full elsewhere in this Quarterly Report are not the only risks that we face. Additional risks and uncertainties not presently known to us, or that we currently deem to be immaterial may also materially adversely affect our business, financial condition, results of operations and future growth prospects.