Sionna Therapeutics, Inc.

Previous wording

We believe our robust pipeline of NBD1 stabilizers and complementary CFTR modu lators provide multiple potential pathways to achieving our goal, either in combination with each other to produce a proprietary combination CF therapy, or an NBD1 stabilizer in combination with the current standard of care ("SOC") for CF.

Current wording

We believe our robust pipeline of NBD1 stabilizers and complementary CFTR modu lators provide multiple potential pathways to achieving our goal, either in combination with each other to produce a proprietary dual combination CF therapy, or an NBD1 stabilizer in combination with the current standard of care for CF.

Previous wording

In June 2025, we announced positive topline data from our two randomized, double-blinded, placebo-controlled Phase 1 clinical trials evaluating SION-719 and SION-451, our lead NBD1 stabilizer product candidates, in over 200 healthy volunteers. The trials assessed the safety, tolerability, and pharmacokinetics ("PK") of single and multiple ascending doses of each product candidate, as well as food effect and tablet bioequivalence.

Current wording

In June 2025, we announced positive topline data from our two randomized, double-blinded, placebo-controlled Phase 1 clinical trials evaluating SION-719 and SION-451, our lead NBD1 stabilizer product candidates, in over 200 healthy volunteers, and our plans to advance both compounds to the next phase of clinical development. The trials assessed the safety, tolerability, and pharmacokinetics ("PK") of single and multiple ascending doses of each product candidate, as well as food effect and tablet bioequivalence.

Previous wording

Both SION-719 and SION-451 were generally well tolerated in these trials, with no serious adverse events, treatment emergent adverse events that led to discontinuation of drug, or dose-limiting toxicities observed. The Phase 1 data also supported the use of a tablet formulation in future trials and indicated that both compounds could be dosed in a fed or fasted state. Both NBD1 stabilizers met exposure thresholds that we believe, based on our preclinical CF human bronchial epithelial ("CFHBE") model, have the potential to provide clinically meaningful benefit if administered as an add-on to SOC or in proprietary dual combinations with complementary modulators.

Current wording

Both SION-719 and SION-451 were generally well tolerated in these trials, with no serious adverse events, treatment emergent adverse events that led to discontinuation of drug, or dose-limiting toxicities observed. The Phase 1 data also supported the use of a tablet formulation in future trials and indicated that both compounds could be dosed in a fed or fasted state. Both NBD1 stabilizers met target exposure thresholds. Based on the Phase 1 data and our preclinical CF human bronchial epithelial ("CFHBE") model, we believe our NBD1 stabilizers have the potential to provide clinically meaningful benefit, including the potential to restore CFTR function up to wild-type levels, when SION-719 is administered as an add-on to the standard of care or when SION-451 is used in proprietary dual combinations with one of our complementary modulators.

Previous wording

We plan to progress SION-719 into a Phase 2a proof-of-concept trial in CF patients evaluating the compound as an add-on to SOC, pending completion of a drug-drug interaction study to confirm that SION-719 can be dosed with the SOC according to its label. We are on track to initiate the Phase 2a trial in the second half of 2025. SION-451 will advance to a Phase 1 dual combination trial in healthy volunteers evaluating SION-451 in dual combinations with each of galicaftor (SION-2222) and SION-109, two of our complementary CFTR modulators. The trial will evaluate the safety, tolerability, and PK of varying doses of the dual combinations. Initiation is anticipated in the second half of 2025.

Current wording

In October 2025, we announced the initiation of a Phase 2a proof-of-concept trial in CF patients evaluating SION-719 as an add-on to the standard of care. The Phase 2a trial, called PreciSION CF, is designed to evaluate the safety, tolerability, and PK of SION-719 when administered with the standard of care for CF, Vertex Pharmaceuticals, Inc.'s Trikafta, and to assess change in CFTR function as measured by sweat chloride levels. Prior to initiation, we completed a drug-drug interaction study, which confirmed SION-719 can be dosed with Trikafta according to its label. Additionally, in August 2025, we announced the initiation of a Phase 1 dual combination trial in healthy volunteers evaluating SION-451 in dual combinations with each of galicaftor (SION-2222) and SION-109, two of our complementary CFTR modulators. The trial will evaluate the safety, tolerability, and PK of varying doses of the dual combinations and will inform selection of a dual combination for further development. Topline data from both trials are anticipated in mid-2026.

Previous wording

Our portfolio of complementary CFTR modulator candidates are designed to work synergistically with our NBD1 stabilizers to improve CFTR function, as seen in preclinical models. During 2024, we in-licensed three clinical-stage compounds from AbbVie Global Enterprises Ltd. (“AbbVie”) to expand our portfolio of combination product opportunities, including galicaftor (SION-2222), a complementary modulator which targets CFTR’s transmembrane domain 1 (“TMD1”), and has completed Phase 2 clinical trials. In addition, in December 2024, we completed a Phase 1 clinical trial evaluating another complementary modulator, SION-109, which targets CFTR’s intracellular loop 4 (“ICL4”) region.

Current wording

Our portfolio of complementary CFTR modulator candidates are designed to work synergistically with our NBD1 stabilizers to improve CFTR function, as seen in preclinical models. During 2024, we in-licensed three clinical-stage compounds from AbbVie Global Enterprises Ltd. (“AbbVie”) to expand our portfolio of combination product opportunities, including galicaftor (SION-2222), a complementary modulator which targets CFTR’s transmembrane domain 1 (“TMD1”), and has completed Phase 2 clinical trials. In addition, in December 2024, we completed a Phase 1 clinical trial evaluating another complementary modulator, SION-109, which targets CFTR’s intracellular loop 4 (“ICL4”) region. Galicaftor (SION-2222) and SION-109 are currently being evaluated in combination with SION-451 in our ongoing Phase 1 dual combination trial in healthy volunteers.

Previous wording

Due to our significant research, development and manufacturing expenditures, we have accumulated substantial losses and negative cash flows since our inception, including net losses of $34.6 million and $20.4 million for the six months ended June 30, 2025, and 2024, respectively. As of June 30, 2025, we had an accumulated deficit of $215.6 million.

Current wording

Due to our significant research, development and manufacturing expenditures, we have accumulated substantial losses and negative cash flows since our inception, including net losses of $54.8 million and $45.8 million for the nine months ended September 30, 2025, and 2024, respectively. As of September 30, 2025, we had an accumulated deficit of $235.9 million.

Previous wording

As of June 30, 2025, we had cash, cash equivalents and marketable securities of $337.3 million. Based upon our current operating plans, we believe that with our existing cash, cash equivalents and marketable securities, will be sufficient to fund our operations into 2028. We have based this estimate on assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we expect. In addition, we could utilize our available capital resources sooner than we expect. See the sections titled “—Liquidity and Capital Resources” and “Risk Factors—Risks Related to Our Limited Operating History, Financial Condition and Need for Additional Capital” included elsewhere in this Quarterly Report.

Current wording

As of September 30, 2025, we had cash, cash equivalents and marketable securities of $325.0 million. Based upon our current operating plans, we believe that with our existing cash, cash equivalents and marketable securities, will be sufficient to fund our operations into 2028. We have based this estimate on assumptions that may prove to be wrong, and we could exhaust our available capital resources sooner than we expect. In addition, we could utilize our available capital resources sooner than we expect. See the sections titled “—Liquidity and Capital Resources” and “Risk Factors—Risks Related to Our Limited Operating History, Financial Condition and Need for Additional Capital” included elsewhere in this Quarterly Report.

Previous wording

•the costs to acquire in-process research and development with no alternative future use acquired in an asset acquisition;

Current wording

•the costs to acquire in-process research and development ("IPR&D") with no alternative future use acquired in an asset acquisition;

Previous wording

General and administrative expenses consist primarily of personnel-related costs, including salaries, payroll tax, bonuses, benefits and stock-based compensation charges for those individuals in executive, legal, finance, human resources, information technology and other administrative functions. Other significant costs include legal fees relating to intellectual property and corporate matters, professional fees for auditing, accounting, tax and consulting services, office and information technology costs, insurance costs and facilities, depreciation and other general and administrative expenses that are allocated. We recognize general and administrative expenses in the periods in which they are incurred.

Current wording

General and administrative expenses consist primarily of personnel-related costs, including salaries, payroll tax, bonuses, benefits and stock-based compensation charges for those individuals in executive, legal, finance, human resources, information technology and other administrative functions. Other significant costs include legal fees relating to intellectual property and corporate matters, professional fees for auditing, accounting, tax and consulting services. Lastly, corporate overhead expenses such as information technology, insurance, facilities, and depreciation that are not allocated to the Company’s research and development activities are included in general and administrative expenses. We recognize general and administrative expenses in the periods in which they are incurred.

Previous wording

•direct research and development expenses increased by $5.4 million primarily due to an increase in clinical programs and combination development activities; and

Current wording

•direct research and development expenses increased by $3.1 million primarily due to an increase in clinical programs and combination development activities; and

Previous wording

•unallocated research and development expenses increased by $1.8 million primarily due to a $1.4 million increase in personnel-related expenses including stock-based compensation, driven by an increase in the size of our workforce to support our clinical pipeline.

Current wording

•unallocated research and development expenses decreased by $11.6 million primarily due to IPR&D acquisition costs incurred in connection with our license agreement with AbbVie of $13.6 million in the third quarter of 2024, partially offset by a $1.5 million increase in personnel-related expenses including stock-based compensation, driven by an increase in the size of our workforce to support our clinical pipeline.

Previous wording

General and administrative expenses increased by $3.5 million to $6.5 million for the three months ended June 30, 2025, from $3.1 million for the three months ended June 30, 2024. The increase in general and administrative expenses was primarily due to:

Current wording

General and administrative expenses increased by $4.4 million to $7.8 million for the three months ended September 30, 2025, from $3.4 million for the three months ended September 30, 2024. The increase in general and administrative expenses was primarily due to:

Previous wording

•$2.3 million increase in personnel-related expenses including stock-based compensation, driven by an increase in the size of our workforce; and

Current wording

•$3.0 million increase in personnel-related expenses including stock-based compensation, driven by an increase in the size of our workforce; and

Previous wording

•$1.0 million increase in fees related to the increased use of consultants and professional service organizations.

Current wording

•$1.2 million increase in fees related to the increased use of consultants and professional service organizations.

Previous wording

Interest income increased by $1.1 million to $3.7 million for the three months ended June 30, 2025, from $2.6 million for the three months ended June 30, 2024, primarily driven by an increased investment in debt securities due to the proceeds received from the initial public offering and the amortization of discounts on our investment activity.

Current wording

Interest income increased by $1.1 million to $3.5 million for the three months ended September 30, 2025, from $2.4 million for the three months ended September 30, 2024, primarily driven by an increased investment in debt securities due to the proceeds received from the initial public offering and the amortization of discounts on our investment activity.

Previous wording

Other income was $0.2 million for the three months ended June 30, 2025, and 2024, due to sublease income in connection with our subleasing agreement.

Current wording

Other income was $0.1 million and $0.2 million for the three months ended September 30, 2025, and 2024, respectively, due to sublease income in connection with our subleasing agreement.

Previous wording

•direct research and development expenses increased by $7.3 million primarily due to an increase in clinical programs and combination development activities; and

Current wording

•direct research and development expenses increased by $10.4 million primarily due to an increase in clinical programs and combination development activities; and

Previous wording

•unallocated research and development expenses increased by $3.3 million primarily due to a $2.6 million increase in personnel-related expenses including stock-based compensation, driven by an increase in the size of our workforce to support our clinical pipeline.

Current wording

•unallocated research and development expenses decreased by $8.3 million primarily due IPR&D acquisition costs incurred in connection with our license agreement with AbbVie of $13.6 million in the third quarter of 2024, partially offset by a $4.1 million increase in personnel-related expenses including stock-based compensation, driven by an increase in the size of our workforce to support our clinical pipeline.

Previous wording

General and administrative expenses increased by $6.5 million to $12.5 million for the six months ended June 30, 2025, from $6.0 million for the six months ended June 30, 2024. The increase in general and administrative expenses was primarily due to:

Current wording

General and administrative expenses increased by $10.9 million to $20.3 million for the nine months ended September 30, 2025, from $9.4 million for the nine months ended September 30, 2024. The increase in general and administrative expenses was primarily due to:

Previous wording

•$2.1 million increase in fees related to the increased use of consultants and professional service organizations.

Current wording

•$3.3 million increase in fees related to the increased use of consultants and professional service organizations.

Previous wording

Interest income increased by $3.0 million to $6.7 million for the six months ended June 30, 2025, from $3.7 million for the six months ended June 30, 2024, primarily driven by an increased investment in debt securities due to the proceeds received from the initial public offering and the amortization of discounts on our investment activity.

Current wording

Interest income increased by $4.0 million to $10.1 million for the nine months ended September 30, 2025, from $6.1 million for the nine months ended September 30, 2024, primarily driven by an increased investment in debt securities due to the proceeds received from the initial public offering and the amortization of discounts on our investment activity.

Previous wording

Other income was $0.3 million for the six months ended June 30, 2025, and 2024, due to sublease income in connection with our subleasing agreement.

Current wording

Other income was $0.4 million and $0.5 million for the nine months ended September 30, 2025, and 2024, respectively, due to sublease income in connection with our subleasing agreement.

Previous wording

As of June 30, 2025, we had $337.3 million in cash, cash equivalents and marketable securities.

Current wording

As of September 30, 2025, we had $325.0 million in cash, cash equivalents and marketable securities.

Previous wording

For the six months ended June 30, 2025, net cash used in operating activities was $34.4 million primarily due to our net loss of $34.6 million and changes in operating assets and liabilities of $4.2 million, partially offset by $4.4 million of net non-cash charges, which includes stock-based compensation, depreciation, non-cash operating lease expense and amortization of discounts on marketable securities.

Current wording

For the nine months ended September 30, 2025, net cash used in operating activities was $49.7 million primarily due to our net loss of $54.8 million and changes in operating assets and liabilities of $2.4 million, partially offset by $7.5 million of net non-cash charges, which includes stock-based compensation, depreciation, non-cash operating lease expense and amortization of discounts on marketable securities.

Previous wording

For the six months ended June 30, 2024, net cash used in operating activities was $23.3 million primarily due to our net loss of $20.4 million and changes in operating assets and liabilities of $4.6 million, partially offset by $1.7 million of net non-cash charges, which includes stock-based compensation, depreciation, non-cash operating lease expense and amortization of discounts on marketable securities.

Current wording

For the nine months ended September 30, 2024, net cash used in operating activities was $41.0 million primarily due to our net loss of $45.8 million and changes in operating assets and liabilities of $6.2 million, partially offset by $11.0 million of net non-cash charges, which includes stock-based compensation, depreciation, non-cash operating lease expense, non-cash expense related to IPR&D acquisition and amortization of discounts on marketable securities.

Previous wording

Net cash used in investing activities was $164.4 million during the six months ended June 30, 2025, which was primarily driven by purchases of marketable securities of $228.0 million, partially offset by maturities of marketable securities of $63.7 million.

Current wording

Net cash used in investing activities was $141.3 million during the nine months ended September 30, 2025, which was primarily driven by purchases of marketable securities of $282.1 million and purchases of property and equipment of $0.2 million, partially offset by maturities of marketable securities of $141.0 million.

Previous wording

Net cash used in investing activities was $152.5 million during the six months ended June 30, 2024, due to purchases of marketable securities.

Current wording

Net cash used in investing activities was $142.1 million during the nine months ended September 30, 2024, due to purchases of marketable securities of $175.6 million, partially offset by maturities of marketable securities of $33.5 million.

Previous wording

Net cash provided by financing activities was $202.1 million during the six months ended June 30, 2025, as compared to $181.4 million during the six months ended June 30, 2024. During the six months ended June 30, 2025, and 2024, the Company closed its IPO and Series C Financing, respectively.

Current wording

Net cash provided by financing activities was $180.4 million during the nine months ended September 30, 2024, during which time the Company closed its Series C Financing.

Previous wording

As of June 30, 2025, we had cash, cash equivalents and marketable securities of $337.3 million. Based upon our current operating plans, we believe that our existing cash, cash equivalents and investments in marketable securities, will be sufficient to fund our operations into 2028. However, our forecast for the period of time through which our financial resources will be adequate to support our operations is a forward-looking statement that involves risks and uncertainties, and actual results could vary materially. Additionally, conducting preclinical studies and clinical trials is costly, and the timing of progress and expenses in these studies and trials is uncertain. We will need to raise substantial additional capital in the future.

Current wording

As of September 30, 2025, we had cash, cash equivalents and marketable securities of $325.0 million. Based upon our current operating plans, we believe that our existing cash, cash equivalents and investments in marketable securities, will be sufficient to fund our operations into 2028. However, our forecast for the period of time through which our financial resources will be adequate to support our operations is a forward-looking statement that involves risks and uncertainties, and actual results could vary materially. Additionally, conducting preclinical studies and clinical trials is costly, and the timing of progress and expenses in these studies and trials is uncertain. We will need to raise substantial additional capital in the future.

Previous wording

During the six months ended June 30, 2025, there were no material changes to our contractual obligations and commitments described under "Management’s Discussion and Analysis of Financial Condition and Results of Operations" in the Annual Report.

Current wording

During the nine months ended September 30, 2025, there were no material changes to our contractual obligations and commitments described under "Management’s Discussion and Analysis of Financial Condition and Results of Operations" in the Annual Report.

Previous wording

During the six months ended June 30, 2025, there were no material changes to our critical accounting estimates described under "Management’s Discussion and Analysis of Financial Condition and Results of Operations" in the Annual Report.

Current wording

During the nine months ended September 30, 2025, there were no material changes to our critical accounting estimates described under "Management’s Discussion and Analysis of Financial Condition and Results of Operations" in the Annual Report.

Previous wording

We will remain an emerging growth company until the earlier of (1) the last day of the fiscal year (a) following the fifth anniversary of the completion of our IPO, (b) in which we have total annual gross revenue of at least $1.235 billion or (c) in which we are deemed to be a “large accelerated filer” under the rules of the SEC, which means, among other things, the market value of our common stock that is held by non-affiliates exceeds $700.0 million as of the last business day of our most recently completed second fiscal quarter and (2) the date on which we have issued more than $1.0 billion in non-convertible debt during the prior three-year period.

Current wording

We will remain an emerging growth company until the earlier of (1) the last day of the fiscal year (a) following the fifth anniversary of the completion of our IPO, (b) in which we have total annual gross revenue of at least $1.235 billion or (c) in which we are deemed to be a “large accelerated filer” under the rules of the SEC, which means, among other things, the market value of our common stock that is held by non-affiliates exceeds