[Part I - Financial Information](index=8&type=section&id=Part%20I%20-%20Financial%20Information) [Financial Statements (Unaudited)](index=8&type=section&id=Item%201.%20Financial%20Statements%20(Unaudited)) The company significantly strengthened its balance sheet post-IPO, though operating losses continued to grow due to increased R&D and G&A expenses - In February 2025, the company completed its IPO, raising net proceeds of approximately **$199.6 million** and converting all outstanding redeemable convertible preferred stock to common stock[40](index=40&type=chunk) Condensed Consolidated Balance Sheet Highlights (in thousands) | Account | March 31, 2025 | December 31, 2024 | | :--- | :--- | :--- | | Cash and cash equivalents | $82,695 | $37,788 | | Marketable securities (current & noncurrent) | $271,993 | $130,255 | | **Total Assets** | **$369,674** | **$185,752** | | Total liabilities | $17,905 | $19,097 | | Total convertible preferred stock | $0 | $330,368 | | **Total stockholders' equity (deficit)** | **$351,769** | **($163,713)** | Condensed Consolidated Statements of Operations (in thousands) | Account | Three Months Ended March 31, 2025 | Three Months Ended March 31, 2024 | | :--- | :--- | :--- | | Research and development | $13,668 | $10,220 | | General and administrative | $5,991 | $2,927 | | Loss from operations | ($19,659) | ($13,147) | | Interest income | $3,000 | $1,132 | | **Net loss** | **($16,482)** | **($11,847)** | Condensed Consolidated Statements of Cash Flows Highlights (in thousands) | Cash Flow Activity | Three Months Ended March 31, 2025 | Three Months Ended March 31, 2024 | | :--- | :--- | :--- | | Net cash used in operating activities | ($16,288) | ($13,175) | | Net cash used in investing activities | ($141,194) | ($123,927) | | Net cash provided by financing activities | $202,389 | $181,333 | [Management's Discussion and Analysis of Financial Condition and Results of Operations (MD&A)](index=22&type=section&id=Item%202.%20Management's%20Discussion%20and%20Analysis%20of%20Financial%20Condition%20and%20Results%20of%20Operations) The company's net loss grew to $16.5 million in Q1 2025, but its post-IPO cash position of $354.7 million is expected to fund operations into 2028 - The company's mission is to revolutionize CF treatment by developing medicines that normalize CFTR protein function, focusing on stabilizing the **NBD1 domain**[69](index=69&type=chunk) - **Topline data** from Phase 1 trials of NBD1 stabilizers SION-719 and SION-451 are expected in Q2 2025, with a proof-of-concept trial planned for H2 2025[71](index=71&type=chunk)[72](index=72&type=chunk) - As of March 31, 2025, the company had **$354.7 million** in cash, cash equivalents, and marketable securities, sufficient to support operations into 2028[84](index=84&type=chunk)[113](index=113&type=chunk) - The **$3.4 million increase in R&D expenses** was primarily due to a $1.9 million increase in direct costs for clinical programs and a $1.2 million increase in personnel-related expenses[101](index=101&type=chunk) - The **$3.1 million increase in G&A expenses** was driven by a $2.0 million increase in personnel-related costs and a $1.0 million increase in professional services fees[102](index=102&type=chunk)[108](index=108&type=chunk) Comparison of Operating Expenses (in thousands) | Expense Category | Q1 2025 | Q1 2024 | Change | | :--- | :--- | :--- | :--- | | Research and development | $13,668 | $10,220 | $3,448 | | General and administrative | $5,991 | $2,927 | $3,064 | | **Total operating expenses** | **$19,659** | **$13,147** | **$6,512** | [Quantitative and Qualitative Disclosures About Market Risk](index=31&type=section&id=Item%203.%20Quantitative%20and%20Qualitative%20Disclosures%20About%20Market%20Risk) The company is exempt from providing market risk disclosures as it qualifies as a smaller reporting company under SEC regulations - As a **"smaller reporting company,"** Sionna Therapeutics is exempt from providing the disclosures required by Item 305 of Regulation S-K[124](index=124&type=chunk) [Controls and Procedures](index=31&type=section&id=Item%204.%20Controls%20and%20Procedures) Management concluded that disclosure controls and procedures were effective as of March 31, 2025, with no material changes to internal controls during the quarter - Management's evaluation concluded that the company's disclosure controls and procedures were **effective** at a reasonable assurance level as of the end of the period covered by the report[125](index=125&type=chunk) - **No changes** in internal control over financial reporting occurred during the quarter that have materially affected, or are reasonably likely to materially affect, these controls[126](index=126&type=chunk) [Part II - Other Information](index=32&type=section&id=Part%20II%20-%20Other%20Information) [Legal Proceedings](index=32&type=section&id=Item%201.%20Legal%20Proceedings) The company is not currently involved in any material legal proceedings, nor is management aware of any pending or threatened material legal matters - The company's management is currently not aware of any legal matters that could have a **material effect** on its financial position, results of operations, or cash flows[128](index=128&type=chunk) [Risk Factors](index=32&type=section&id=Item%201A.%20Risk%20Factors) The company faces significant financial, developmental, competitive, and third-party dependency risks, including a history of losses and reliance on novel drug candidates - The company is a clinical-stage biopharmaceutical company with significant operating losses (**$16.5 million for Q1 2025**) and an accumulated deficit of **$197.6 million** as of March 31, 2025[130](index=130&type=chunk)[131](index=131&type=chunk) - The business is substantially dependent on the success of its **NBD1 stabilizer product candidates** (e.g., SION-719, SION-451), which target a novel protein domain, making development inherently risky[145](index=145&type=chunk)[180](index=180&type=chunk) - The company faces substantial competition from established players, with its main competitor, **Vertex**, holding a significant market share and possessing greater resources[314](index=314&type=chunk)[315](index=315&type=chunk) - Sionna is dependent on intellectual property licensed from third parties like **Sanofi and AbbVie** and relies on CROs and CDMOs for clinical trials and manufacturing[214](index=214&type=chunk)[215](index=215&type=chunk)[219](index=219&type=chunk)[223](index=223&type=chunk) - **Lock-up agreements** covering approximately 35.3 million shares of common stock from the IPO will expire in August 2025, potentially leading to significant sales and stock price volatility[357](index=357&type=chunk) [Unregistered Sales of Equity Securities and Use of Proceeds](index=88&type=section&id=Item%202.%20Unregistered%20Sales%20of%20Equity%20Securities%20and%20Use%20of%20Proceeds) The company's IPO in February 2025 generated net proceeds of $199.6 million, with no material change in the planned use of these funds - The company's IPO registration statement (File No. 333-284352) became effective on **February 6, 2025**[411](index=411&type=chunk) - There has been **no material change** in the planned use of the net proceeds from the IPO as described in the final prospectus[412](index=412&type=chunk) Initial Public Offering (IPO) Details | Metric | Value | | :--- | :--- | | Shares Sold (incl. underwriter option) | 12,176,467 | | Price per Share | $18.00 | | Aggregate Net Proceeds | ~$199.6 million | [Defaults Upon Senior Securities](index=89&type=section&id=Item%203.%20Defaults%20Upon%20Senior%20Securities) The company reports no defaults upon senior securities - None[415](index=415&type=chunk) [Mine Safety Disclosures](index=89&type=section&id=Item%204.%20Mine%20Safety%20Disclosures) This item is not applicable to the company - Not applicable[416](index=416&type=chunk) [Other Information](index=89&type=section&id=Item%205.%20Other%20Information) No directors or executive officers of the company adopted, modified, or terminated a Rule 10b5-1 trading plan during the first quarter of 2025 - During the quarter ended March 31, 2025, none of the company's directors or executive officers adopted, modified, or terminated any trading plan intended to satisfy the conditions of **Rule 10b5-1(c)**[417](index=417&type=chunk) [Exhibits](index=90&type=section&id=Item%206.%20Exhibits) This section lists exhibits filed with the report, including corporate governance documents, stock plans, and required officer certifications - The report includes key corporate governance documents, such as the **Fifth Amended and Restated Certificate of Incorporation** and **Amended and Restated Bylaws**[420](index=420&type=chunk) - Compensatory plans filed as exhibits include the **2025 Stock Option and Incentive Plan**, the **2025 Employee Stock Purchase Plan**, and the **Senior Executive Cash Incentive Bonus Plan**[420](index=420&type=chunk) - **Certifications by the Principal Executive Officer and Principal Financial Officer** pursuant to Sections 302 and 906 of the Sarbanes-Oxley Act of 2002 are included as exhibits[420](index=420&type=chunk)

[Sionna Therapeutics Q1 2025 Financial Results and Business Update](index=1&type=section&id=Sionna%20Therapeutics%20Reports%20First%20Quarter%202025%20Financial%20Results) [Business and Pipeline Update](index=1&type=section&id=Business%20and%20Pipeline%20Update) Sionna Therapeutics completed Phase 1 dosing for NBD1 stabilizers, anticipating **Q2 2025** topline data and initiating Phase 2a and dual combination trials in **H2 2025**, bolstered by a **$219 million** IPO - Phase 1 dosing for NBD1 stabilizers SION-719 & SION-451 is complete, with both compounds being generally well-tolerated. Topline data is anticipated in the current quarter (**Q2 2025**)[2](index=2&type=chunk)[4](index=4&type=chunk) - The company is on track to initiate a Phase 2a proof-of-concept trial and at least one dual combination MAD trial in the **second half of 2025**, with topline data for both anticipated in **mid-2026**[2](index=2&type=chunk)[4](index=4&type=chunk) - In February 2025, Sionna completed an upsized IPO, raising approximately **$219 million** in gross proceeds[5](index=5&type=chunk) - The company will present preclinical data on its NBD1 stabilizers in combination with other modulators at the European Cystic Fibrosis Conference in June 2025[6](index=6&type=chunk) [Q1 2025 Financial Results](index=2&type=section&id=Financial%20Results%20for%20the%20Quarter%20Ended%20March%2031%2C%202025) Sionna reported a Q1 2025 net loss of **$16.5 million**, an increase from the prior year, with cash and equivalents rising to **$354.7 million** post-IPO, expected to fund operations into **2028** Q1 2025 vs Q1 2024 Operating Results (in millions) | Metric | Q1 2025 | Q1 2024 | Change | | :--- | :--- | :--- | :--- | | Research and Development Expenses | $13.7 | $10.2 | +$3.5 | | General and Administrative Expenses | $6.0 | $2.9 | +$3.1 | | **Net Loss** | **$16.5** | **$11.8** | **+$4.7** | Key Balance Sheet Data (in millions) | Metric | March 31, 2025 | December 31, 2024 | | :--- | :--- | :--- | | Cash, cash equivalents, and marketable securities | $354.7 | $168.0 | | Total stockholders' equity (deficit) | $351.8 | $(163.7) | - The current cash position of **$354.7 million** is expected to fund operations into **2028**[2](index=2&type=chunk)[9](index=9&type=chunk) [Consolidated Statements of Operations](index=4&type=section&id=Consolidated%20Statements%20of%20Operations) Sionna's Q1 2025 net loss increased to **$16.5 million** ($0.62 per share) from **$11.8 million** in Q1 2024, primarily due to higher operating expenses Consolidated Statements of Operations (Unaudited, in thousands) | | Three Months Ended March 31, | | :--- | :--- | :--- | | | **2025** | **2024** | | **Operating expenses:** | | | | Research and development | $13,668 | $10,220 | | General and administrative | $5,991 | $2,927 | | **Total operating expenses** | **$19,659** | **$13,147** | | Loss from operations | $(19,659) | $(13,147) | | **Other income:** | | | | Interest income | $3,000 | $1,132 | | **Net loss** | **$(16,482)** | **$(11,847)** | | Net loss per share, basic and diluted | $(0.62) | $(3.84) | | Weighted-average common shares outstanding | 26,596,059 | 3,082,635 | [Selected Consolidated Balance Sheet Data](index=4&type=section&id=Selected%20Consolidated%20Balance%20Sheet%20Data) Post-IPO, Sionna's balance sheet as of March 31, 2025, shows cash and equivalents at **$354.7 million** and total stockholders' equity at **$351.8 million**, a significant improvement Selected Consolidated Balance Sheet Data (Unaudited, in thousands) | | March 31, 2025 | December 31, 2024 | | :--- | :--- | :--- | | Cash, cash equivalents, and marketable securities | $354,688 | $168,043 | | Working capital | $264,153 | $140,573 | | Total assets | $369,674 | $185,752 | | Total stockholders' equity (deficit) | $351,769 | $(163,713) |

Summary of Sionna Therapeutics (SION) 2025 Conference Call Company Overview - **Company**: Sionna Therapeutics - **CEO**: Mike Clunan - **Founded**: 2019 as a spin-out from Sanofi, with historical ties to Genzyme [5][6] Industry Focus - **Industry**: Life Sciences, specifically targeting cystic fibrosis (CF) [2][4] - **Market Opportunity**: The current market for CF treatments is valued at $11 billion and is expected to grow [7] Core Points and Arguments 1. **Unmet Need in Cystic Fibrosis**: - Despite advancements by Vertex Pharmaceuticals, a significant unmet need remains in CF treatment [6] - Only one-third of patients on the standard of care, TRIKAFTA, achieve normal CFTR function, indicating a large opportunity for Sionna [6][48] 2. **Targeting NBD1**: - Sionna is focusing on NBD1, a previously considered "undruggable" target, to enhance CFTR correction [7][8] - NBD1 stabilization could potentially deliver clinical benefits comparable to the triple combination therapy of Trikafta [13][23] 3. **Predictive CF HBE Assay**: - The CF HBE assay is a gold standard in vitro assay that is highly predictive of clinical outcomes [8][9] - This assay is used for early screening of compounds and determining exposure targets for clinical trials [9] 4. **Pipeline Development**: - Two NBD1 compounds, 719 and 451, are in Phase 1 trials, with encouraging interim data expected soon [14][15] - Sionna has licensed three complementary mechanisms from AbbVie to enhance their portfolio [10][20] 5. **Combination Strategies**: - The company plans to prioritize two combination assets, Galacaftor and ICL4 corrector (109), to work alongside NBD1 [16][39] - The goal is to create a dual combination that provides meaningful clinical benefits over existing treatments [18][19] 6. **Financial Position**: - Sionna raised $219 million in its IPO, providing financial flexibility and a runway into 2028 [20][46] 7. **Upcoming Milestones**: - Top-line data from Phase 1 studies is expected soon, followed by a Phase 2a proof of concept study to demonstrate the efficacy of NBD1 as an add-on to Trikafta [41][44] - Combination studies with healthy volunteers are also planned to assess tolerability and pharmacokinetics [45] Additional Important Content - **Clinical Endpoint Correlation**: - There is a strong correlation (0.96) between chloride transport and FEV1, with a target of at least a 10 millimole improvement in sweat chloride to demonstrate clinical benefit [53] - **Strategic Flexibility**: - Sionna's unique approach to targeting NBD1 allows for multiple strategies in the market, including layering NBD1 on top of existing therapies [17][18] - **Patient Impact**: - The company aims to shift the treatment paradigm in CF by providing more options and improving patient outcomes [50][49] This summary encapsulates the key points discussed during the conference call, highlighting Sionna Therapeutics' strategic focus, market opportunities, and upcoming milestones in the development of its cystic fibrosis treatments.

Company Overview - Sionna Therapeutics, Inc. is a clinical-stage biopharmaceutical company focused on revolutionizing the treatment of cystic fibrosis (CF) by developing novel medicines that normalize the function of the cystic fibrosis transmembrane conductance regulator (CFTR) protein [3] - The company aims to deliver differentiated medicines that restore CFTR function to near-normal levels by directly stabilizing CFTR's nucleotide-binding domain 1 (NBD1), which is believed to be crucial for improving clinical outcomes and quality of life for CF patients [3] Pipeline and Research Focus - Sionna is advancing a pipeline of small molecules engineered to correct defects caused by the F508del genetic mutation located in NBD1 [3] - The company is also developing a portfolio of complementary CFTR modulators designed to work synergistically with its NBD1 stabilizers to enhance CFTR function [3] Upcoming Events - Management will present at The Citizens Life Sciences Conference on May 7, 2025, at 12:30 p.m. ET [1] - A live webcast of the presentation will be available on the company's Investor Relations website, with a replay accessible for 90 days post-event [2]

Table of Contents UNITED STATES SECURITIES AND EXCHANGE COMMISSION Washington, D.C. 20549 FORM 10-K __________________________ (Mark One) x ANNUAL REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 For the fiscal year ended December 31, 2024 OR o TRANSITION REPORT PURSUANT TO SECTION 13 OR 15(d) OF THE SECURITIES EXCHANGE ACT OF 1934 FOR THE TRANSITION PERIOD FROM____ to Commission file number 001-42504 _________________________________________________ SIONNA THERAPEUTICS, INC. (E ...

Exhibit 99.1 Sionna Therapeutics Reports Fourth Quarter and Full Year 2024 Financial Results Phase 1 MAD dosing completed for SION-451 and final MAD cohort of SION-719 planned; Interim data in healthy volunteers show potential to provide clinically meaningful benefit to CF patients. Topline data anticipated in first half of 2025 On track to initiate NBD1 Phase 2a proof-of-concept trial in combination with SOC in CF patients and combination MAD trials of an NBD1 stabilizer with a complementary modulator in h ...