Windward Bio Group: DRS filing (amended)

Cover page 7 changes

As confidentially submitted to the U.S. Securities and Exchange Commission on August 27, September 21, 2026.

This Amendment No. 1 2 to the draft registration statement has not been filed publicly with the U.S. Securities and Exchange Commission and all information contained herein remains confidential.

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Amendment No. 1 2 to Form F-1

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Latham & Watkins LLP

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New York, New York 10020

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Investing in our common shares involves

involves a high degree of risk. Before buying any common shares, you should carefully read the discussion of material risks of investing in our common shares in " Risk Factors " beginning on page 15 16 of this prospectus.

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Presentation of financial information 2 changes

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We have made rounding adjustments to some of the figures

We have made rounding adjustments to some of the figures included in this prospectus. Accordingly, numerical figures shown as totals in some tables may not be an arithmetic aggregation of the figures that preceded them.

Prospectus summary 29 changes

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We are a clinical-stage biotechnology company developing long-acting and ultra-long-acting antibody medicines for patients with serious respiratory and dermatologic diseases, including asthma, chronic obstructive pulmonary disease, or COPD, and atopic dermatitis. We estimate these diseases collectively represent a $60 billion peak market opportunity for biologic therapies, as we believe the majority of patients eligible to receive biologic treatment for these diseases remain untreated. and there are Our product candidates can potentially address this significant unmet needs to treat need, allow for treatment of a broader population of patients, improve efficacy, and improve dosing convenience and adherence to treatment. We estimate that these diseases collectively affect more than 100 million people in the United States, EU5 (France, Germany, Italy, Spain, and the United Kingdom), and Japan and more than 8 million are eligible for biologics treatment.

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being evaluated in POLARIS-1, a Phase 2/3 study in severe uncontrolled asthma. A second Phase 3 asthma study, POLARIS-2, is planned, and a Phase 2 study of WIN378 in COPD, SIRIUS, was initiated in June 2026. We expect that the next data readout for WIN378 will be a Phase 2 interim analysis in the second half of 2026.

is currently in a Phase 1 healthy volunteer study with INDs open in the United States, Australia and the People's Republic of China, or the PRC, assessing safety and pharmacokinetics. We expect that the next data readout for WIN027 will be the full Phase 1 results in the first half of 2027. We also plan to initiate two global Phase 2 studies with our partner Qyuns Therapeutics Co., Ltd., or Qyuns—a Phase 2 dose-ranging study in COPD, fully powered on the registrational endpoint of exacerbation rate ratio, is planned to begin in the first half of 2027, and an atopic dermatitis study is planned to begin the second half of 2026.

WIN378 is an ultra-long-acting and potentially novel fully human monoclonal antibody that is designed to inhibit thymic stromal lymphopoietin, or TSLP. TSLP is positioned upstream of multiple inflammatory pathways and is a clinically validated target in respiratory disease. WIN378 is currently being evaluated in POLARIS-1, a Phase 2/3 study in severe uncontrolled asthma. A second Phase 3 asthma study, POLARIS-2, is planned, and a Phase 2 study of WIN378 in COPD, SIRIUS, was initiated in June 2026. A pre-planned analysis of the Phase 2 portion of POLARIS-1 was completed in the second half of 2026. This model-informed Phase 2 portion characterized the dose-response relationship and enrolled 147 patients, exceeding the enrollment target of 120 patients. WIN378 was well-tolerated with favorable safety results — there were no treatment-related serious adverse events, withdrawals or discontinuations observed to date. Adverse events were balanced between active arms and placebo, with low rates of injection site reactions and antidrug antibodies. WIN378 had an observed half-life of up to 75 days and produced improvements in lung function and biomarkers of airway inflammation at week 24, which we believe support twice-yearly subcutaneous dosing and the potential for improved clinical outcomes. Two twice-yearly dose levels were selected, and the Phase 3 portion of POLARIS-1 was initiated in September 2026. We expect that the next data readout for WIN378 will be the Phase 2 primary results at week 24 in the first half of 2027.

WIN027 is an ultra-long-acting bispecific antibody that simultaneously targets TSLP and interleukin-13, or IL-13, two clinically validated drivers of inflammatory disease. We believe that dual inhibition of these pathways has the potential to deliver deeper and more durable disease control than targeting either pathway alone. WIN027 is currently in a Phase 1 healthy volunteer study with INDs open in the United States, Australia and the People's Republic of China, or the PRC, assessing safety and pharmacokinetics. In an interim analysis of the Phase 1 study, we observed a 62-day half-life, low immunogenicity, and favorable safety results, with full pharmacokinetic and immunogenicity data expected in the first half of 2027. We plan to initiate a global Phase 2 study in COPD fully powered on the registrational endpoint of exacerbation rate ratio and a second Phase 2 study in atopic dermatitis in the first half of 2027. Additionally, based on our knowledge, our partner Qyuns Therapeutics Co., Ltd., or Qyuns, is planning to conduct Phase 2 studies in asthma, chronic rhinosinusitis with nasal polyps, or CRSwNP, and atopic dermatitis in the PRC in the second half of 2026, with topline results expected in 2027 and 2028.

Our goal is to develop, obtain regulatory approval, and

regulatory approval, and commercialize potentially novel immunology therapeutics for patients underserved by today's standard of care in asthma, COPD, atopic dermatitis, and other immunological conditions. Key elements of our novel approach, which we believe has the potential to improve the outcomes of the current generation of biologics in inflammatory lung and skin diseases for these patients, are below.

We target clinically validated biologic drivers of disease including TSLP and IL-13.

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The following summarizes our programs, their mechanisms, targeted indications, development stage and our commercial rights.

Windward Bio holds global rights to WIN378 excluding Greater China and certain Asian markets ** Exclusivity based on pending applications and anticipated patent extensions *** Asthma and CRSwNP Phase 2 studies are planned in the PRC only, conducted and funded by Qyuns Therapeutics **** Lead optimization stage with potential in respiratory and dermatology; see "—Additional bispecific programs" for more information IP=intellectual property, mAb=monoclonal antibody WIN378 is an ultra-long-acting and potentially novel fully human monoclonal antibody that is designed to inhibit the TSLP ligand. WIN378 has been engineered to achieve half-life extension and silenced effector function. In preclinical studies, WIN378 has been observed to have greater potency than the currently approved anti-TSLP treatment, has two binding sites to TSLP and fully overlaps the same binding site as Tezspire , tezepelumab. WIN378 has been studied in a Phase 1 trial, which evaluated an extended half-life that we believe may support twice-yearly dosing, demonstrated a low rate of antidrug antibodies, and was well tolerated up to the highest dose tested.

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POLARIS-1, a Phase 2/3 study in severe, uncontrolled asthma. We expect A pre-planned interim results analysis from such the Phase 2 portion of the study was completed in the second half of 2026. If successful, Following dose selection based on the interim analysis, we plan to initiate a initiated the Phase 3 portion of POLARIS-1 in the second half of September 2026, with topline results expected in the second half of 2028, and we also plan to initiate a second Phase 3 study (POLARIS-2) in the first half of 2027 with topline results expected in the second half of 2029. Separately, a Phase 2 study of WIN378 in COPD, SIRIUS, was initiated in June 2026 and we expect topline results in the second half of 2027. We have observed the following results in the Phase 1 clinical trial for WIN378: an extended half-life supporting twice-yearly subcutaneous dosing, a low rate of antidrug antibodies, and favorable safety and tolerability results up to the highest dose tested. While these results may not translate to similar safety or efficacy results in our ongoing POLARIS Phase 2/3 study in patients with asthma or our SIRIUS The preplanned interim analysis of the Phase 2 study in patients with COPD, we believe WIN378 is differentiated from currently approved treatments primarily through its potential for twice-yearly subcutaneous dosing. portion of POLARIS-1 demonstrated the following results:

Half-life of up to 75 days, with clinical effects consistent with twice-yearly dosing.

Significant and sustained effects on FEV1 (up to 174 mL mean increase, placebo-adjusted mean increases up to 256 mL, p=0.033), FeNO and blood eosinophils, key biomarkers that correlate with asthma exacerbations. These effects were rapid and sustained through Week 24 after a single dose of WIN378.

WIN378 was well tolerated with favorable safety results—there were no treatment-related serious adverse events, withdrawals or discontinuations observed to date;

adverse events were balanced between active arms and placebo, with low rates of injection site reactions (<1%) and antidrug antibodies (2.2%).

results may not translate to similar safety or efficacy results in the ongoing Phase 3 portions of our POLARIS studies in patients with asthma or our SIRIUS Phase 2 study in patients with COPD, we believe WIN378 is differentiated from currently approved treatments primarily through its potential for twice-yearly subcutaneous dosing.

Based on published and public statements from other companies as well as results from trials to date in which WIN378 was well tolerated in patients and no serious adverse events deemed to be study-related were reported, we believe that WIN378, if it produces favorable safety and efficacy data in future pivotal trials, has the potential to be the first ultra-long-active ultra-long-acting treatment targeting TSLP to seek approval in the United States. However, the results from early trials of a product candidate may not be predictive of the results that will be obtained in later stage trials of the product candidate.

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WIN027 is a long-acting, an ultra-long-acting, potentially novel, humanized bispecific monoclonal antibody with high-binding affinity for TSLP and IL-13, two well-validated targets in immunological conditions. WIN027 has been engineered to achieve an extended half-life that enables less frequent dosing. Through this dual, long-acting inhibition, WIN027 is designed to treat conditions such as COPD and atopic dermatitis, potentially delivering deeper and more durable disease control than existing biologics. WIN027 has the potential to expand our portfolio to dermatological diseases, including atopic dermatitis.

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WIN027 is currently in a Phase 1 healthy volunteer study with

volunteer study with INDs open in the United States, Australia and the PRC assessing safety and pharmacokinetics. Based on blinded interim data as of June 2026, we have observed a 62-day half-life, low immunogenicity, and favorable safety results, with full pharmacokinetic and immunogenicity data expected in the first half of 2027. If successful, we plan to initiate a global, Phase 2 study in COPD, fully powered on the registrational endpoint of exacerbation rate ratio, as well as a Phase 2 study in atopic dermatitis.

Our development plans for WIN378 and WIN027 include ten Phase 2 and Phase 3 clinical readouts through 2029, not including four additional readouts for WIN027 based on studies conducted by our partner, Qyuns Therapeutics.

AD=atopic dermatitis, COPD=chronic obstructive pulmonary disease, HV=healthy volunteer, TLR=topline results, W=week Additional bispecific programs are in the lead optimization phase. The current program is a next-generation bispecific targeting T2 and non-T2 pathways, with two complementary cytokines. Work to date has included the evaluation of various formats, production at small scale, and the evaluation of productivity, purity and light chain mispairing. Further work has characterized the blocking of both cytokines and a HELA cell-based potency assay has been developed and used to compare the bispecifics' potencies to monospecific benchmarks. Of the three formats evaluated, a lead pre-clinical target format has been identified and selected, with potential across skin and respiratory indications, including atopic dermatitis, asthma, and COPD and other inflammatory and fibrotic skin and lung diseases. We expect to initiate Phase 1 clinical development for these potential skin and respiratory indications in the next 18 months, subject to standard regulatory requirements. The lead format demonstrating benchmark-comparable affinity, cellular potency and manufacturability has been selected and is currently being engineered for half-life extension prior to characterization in nonhuman primate studies.

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We were founded in 2024 and launched in January

January 2025. Our executive team has held leadership positions in drug discovery and development, global commercialization, finance, business development, and corporate strategy spanning multiple companies and therapeutic areas, including immunology. They have developed and commercialized numerous products and have built biotechnology companies from inception through public offerings and strategic acquisitions.

Our management team is led by our founder, Chief Executive Officer and Chairman, Luca Santarelli, M.D., who has more than 25 years of academic and biopharmaceutical research and development experience and previously co-founded and served as Chief Executive Officer of VectivBio, which was acquired by Ironwood Pharmaceuticals in 2023 for $1.2 billion, and Therachon, which was acquired by Pfizer in 2019 for up to $810 million.

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Our business is subject to numerous

Our business is subject to numerous risks and uncertainties of which you should be aware before making an investment decision. You should carefully consider all of the information set forth in this prospectus and, in particular, evaluate the specific factors set forth in the section titled "Risk Factors" before making an investment decision. These risks include, but are not limited to, the following:

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Approximately $ million to fund our Phase 2 trials of WIN027 in COPD and atopic dermatitis;

Approximately $ million to fund our planned global Phase 2b trial of WIN027 in COPD, our planned Phase 2 trial of WIN027 in atopic dermatitis; and related research and development activities, including clinical development, regulatory affairs, quality, research, translational sciences, clinical supply, and drug substance and drug product manufacturing;

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Risk factors 5 changes

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We anticipate that our expenses will

that our expenses will increase substantially if, and as, we:

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Kelun-HBM Agreement and the Qyuns Agreement, we are obligated to make significant payments to our licensors across the full development and commercialization lifecycle of WIN378 and WIN027. Under the Kelun-HBM Agreement, we may be required to pay Kelun and HBM aggregate development milestone payments of up to $330 million for WIN378, aggregate sales milestone payments of up to $600 million per product upon achievement of specified annual net sales thresholds, and low single-digit to low double-digits tiered royalties (a spread of not more than 5 percentage points) on net sales of WIN378 in our licensed worldwide territory (excluding Greater China and several Southeast and West Asian countries). In addition, under the Kelun-HBM Agreement, following the completion of this offering, we may elect, subject to certain conditions, to satisfy up to 50% of the remaining of each of our first seven development milestone payments, which is up to $73.75 million, payable under the Kelun-HBM Agreement by issuing our common shares, rather than in cash; provided that each of Kelun and HBM may not hold, in the aggregate, 20% or more of our outstanding share capital on a fully diluted basis as a result of such equity issuance. Any such issuance of common shares in satisfaction of milestone payments would dilute the ownership interests of our existing shareholders. Under the Qyuns Agreement, we may be required to pay Qyuns aggregate development milestone payments of up to $100 million for WIN027, aggregate sales milestone payments of up to $570 million upon achievement of specified annual net sales thresholds, and mid-single digit to high-single digit tiered royalties on net sales of WIN027 in our licensed worldwide territory (excluding Greater China).

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rules that require investors to disclose their interest in a company if they reach, exceed or fall below certain ownership thresholds only applies to issuers that have a listing for their equity securities in Switzerland. Since our common shares are listed exclusively on , a U.S. market, the disclosure obligations regarding major shareholdings according to art. 120 of the Swiss Financial Markets Infrastructure Act and its implementing provisions do not apply to us.

rules that require investors to disclose their interest in a company if they reach, exceed or fall below certain ownership thresholds only applies to issuers that have a listing for their equity securities in Switzerland. Since our common shares are listed exclusively on Nasdaq, a U.S. market, the disclosure obligations regarding major shareholdings according to art. 120 of the Swiss Financial Markets Infrastructure Act and its implementing provisions do not apply to us. Likewise, the Swiss takeover regime does not apply to us. In particular, the duty to make a mandatory bid offer for all outstanding listed equity securities of a company by any person or group of persons that acquires more than one third of a company's voting rights does not apply to us. In addition, the Swiss takeover regime imposes certain restrictions and obligations on bidders in a voluntary public takeover offer that are designed to protect shareholders. However, these protections are applicable only to issuers that list their equity securities in Switzerland and, because our common shares will be listed exclusively on Nasdaq, will not be applicable to us.

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Use of proceeds 2 changes

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Approximately $ million to fund our Phase 2 trials of WIN027 in COPD and atopic dermatitis through ;

Approximately $ million to fund our planned global Phase 2b trial of WIN027 in COPD, our planned Phase 2 trial of WIN027 in atopic dermatitis; and related research and development activities, including clinical development, regulatory affairs, quality, research, translational sciences, clinical supply, and drug substance and drug product manufacturing;

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Capitalization 4 changes

The following table sets forth our cash and cash equivalents and marketable securities and total capitalization as of June 30, 2026:

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Cash, cash equivalents and marketable securities

Cash and cash equivalents

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Preferred shares (Series A preferred shares, Series A junior preferred shares and Series B preferred shares), par value CHF 0.01 per share; 53,429,037 shares issued and outstanding, actual; shares issued and outstanding, pro forma and shares issued and outstanding, pro forma as adjusted 265,724 Common shares, par value CHF 0.01 per share; 15,542,386 shares issued, and outstanding, actual; shares issued, and outstanding, pro forma and shares issued, and outstanding, pro forma as adjusted Share capital Treasury shares (Common shares, par value CHF 0.01 per share; 50,700 shares) (1 (93,195 ) Reserves 358,087 Accumulated losses 265,724 (93,195 ) Total shareholders' equity $ 265,724 $ $ Total capitalization 290,736 $ 265,724 $ $ (1) CHF amounts contained in this table have been translated into U.S. dollars at the rate of CHF1.00 to $ , solely for the convenience of the reader, which was the noon buying rate of the Federal Reserve Bank of New York on June 30, 2026.

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MD&A 34 changes

Our product candidates,

the following discussion of our financial condition and results of operations in conjunction with our audited consolidated financial statements as of December 31, 2025 and 2024 and for the year ended December 31, 2025 and for the period from July 5, 2024 (inception) to December 31, 2024, and the related notes thereto included elsewhere in this prospectus and in conjunction with our unaudited condensed consolidated interim financial statements as of June 30, 2026 and for the six months ended June 30, 2026 and 2025 and the related notes included elsewhere in this prospectus. In addition to historical information, the following discussion and analysis contains forward-looking statements that reflect our plans, estimates and beliefs. Our actual results and the timing of events could differ materially from those anticipated in the forward-looking statements. Factors that could cause or contribute to these differences include those discussed below and elsewhere in this prospectus, particularly in sections titled "Risk Factors" and "Special Note Regarding Forward-Looking Statements." The audited consolidated financial statements as of December 31, 2025 and 2024 and for the year ended December 31, 2025 and for the period from July 5, 2024 (inception) to December 31, 2024, or the 2024 period, and the unaudited condensed consolidated interim financial statements as of June 30, 2026 and for the six months ended June 30, 2026 and 2025, were prepared in accordance with the IFRS, as issued by the IASB and IAS 34, respectively. As permitted by the applicable rules of the SEC for foreign private issuers, using IFRS, as issued by the IASB, we do not reconcile our consolidated financial statements to U.S. GAAP.

We are a clinical-stage biotechnology company developing long-acting and ultra-long-acting antibody medicines for patients with serious respiratory and dermatologic diseases, including asthma, COPD, and atopic dermatitis. We estimate these diseases collectively represent a $60 billion peak market opportunity for biologic therapies, as we believe that the majority of patients eligible to receive biologic treatment for these diseases remain untreated. and there are Our product candidates can potentially address this significant unmet needs to treat need, allow for treatment of a broader population of patients, improve efficacy, and improve dosing convenience and adherence to treatment. We estimate that these diseases collectively affect more than 100 million people in the United States, EU5, and Japan and more than 8 million are eligible for biologics treatment.

Our product candidates, WIN378 and WIN027, target clinically validated disease pathways and are engineered to remain in the body for extended periods of time, enabling less frequent dosing than currently available treatments. This design feature is combined with additional properties including enhanced target affinity, dual target binding or effector function silencing. We believe our product candidates have the potential to deliver better clinical outcomes while offering the convenience of less frequent dosing than currently available treatments.

WIN378 is currently being

WIN378 is currently being evaluated in POLARIS-1, a Phase 2/3 study in severe uncontrolled asthma. A second Phase 3 asthma study, POLARIS-2, is planned, and a Phase 2 study of WIN378 in COPD, SIRIUS, was initiated in June 2026. We expect that the next data readout for WIN378 will be a Phase 2 interim analysis in the second half of 2026.

WIN027 is currently in a Phase 1 healthy volunteer study with INDs open in the United States, Australia and the PRC, assessing safety and pharmacokinetics. We plan to initiate two global Phase 2 studies with our partner Qyuns— a in the first half of 2027—a global Phase 2 dose-ranging study in COPD fully powered on the registrational endpoint of exacerbation rate ratio is planned to begin in the first half of 2027, and an a second Phase 2 study in atopic dermatitis. study is planned to begin the second half of 2026. We expect that the next data readout for WIN027 will be the full Phase 1 results in the first half of 2027.

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During the year ended

During the year ended December 31, 2025, we generated a net loss of $48.3 million. For the six months ended June 30, 2026, we have generated a net loss of $42.6 million, and a net loss of $22.8 million in the six months ended June 30, 2025. We expect to continue to incur significant losses and that our expenses and operating losses will continue to increase for the foreseeable future if and as we:

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On June 9, 2026, we achieved the second

second development milestone associated with the WIN378 License, which required us to make a payment to Kelun and HBM, in total, of $5.0 million. The second development milestone payment of $5.0 million was paid in July 2026.

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Additionally, we may be required to pay mid-single digit to high-single digit tiered royalties to Qyuns.

We may be required to make additional payments to

payments to Qyuns based on the occurrence or non-occurrence of future events, including development milestones of up to $100.0 million, as well as sales-related milestones of up to $570.0 million. Additionally, we may be required to pay mid-single digit to high-single digit tiered royalties to Qyuns.

Factors Affecting the

Affecting the Comparability of Results of Operations

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At this time, we cannot reasonably

reasonably estimate or know the nature, timing, or estimated costs of the efforts that will be necessary to complete the development of our product candidates. Currently, the Company does not track research and development expenses by program or product candidate. This is because our current activities remain in the discovery phase, where resources, personnel and external costs are shared across multiple research efforts and are not yet attributable to specific programs or product candidates in a systematic manner. We manage our research and development efforts dynamically, taking into account activities needed to support, expand and develop our product candidates. These activities include product formulation, preclinical testing, clinical studies, data analysis, pharmacovigilance and regulatory submissions. As our development programs transition into the preclinical stage and final product candidates are selected, we will begin tracking research and development expenses by product candidate.

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Our general and administrative expenses are primarily related to operating expenses such as insurance costs, travel expenses and facility expenses not otherwise included in research and development expenses , as well as expenses of external advisors, including professional fees for legal, accounting, audit, and tax services. These expenses also include salaries and benefits for our general and administrative personnel, including share-based compensation for the personnel in our executive, finance, accounting, legal, human resources, business development, information technology and other administrative areas. Depreciation expense is recognized on our assets used in supporting our general and administrative functions.

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Financial income (expense) and foreign exchange differences, net

Our Financial income (expense) and foreign exchange differences, net financial income (expense) consists primarily of interest income earned on our money market funds and other interest-bearing deposits, fair value gains (both realized and unrealized) on our financial assets measured at fair value through profit or loss, and interest expense on our lease liabilities. The financial assets measured at fair value through profit or loss include our investment in money market funds and high-grade corporate bonds.

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Payroll expenses and share-based

share-based compensation increased by $9.0 million in the year ended December 31, 2025 compared to the period from July 5, 2024 to December 31, 2024. This increase was primarily driven by the hiring of our first employees who focus on research and development activities, as we built out our research and development capabilities as well as the establishment of our equity incentive plans for research and development employees to allow them to participate in our equity.

Depreciation expense increased by $0.1 million in the year ended December 31, 2025, compared to the period from July 5, 2024 to December 31, 2024. This increase was primarily driven by the acquisition of additional assets required to carry out our research and development activities, including equipment used in clinical trials.

This increase was primarily driven by the acquisition of additional assets required to carry out our research and development activities, including equipment used in clinical trials.

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The following table provides information regarding our

Since our inception, we have incurred significant operating losses and negative cash flows from our operations. We have not commercialized any of our product candidates and we do not expect to be able to generate any revenue from product sales for the next several years, if ever. Our operations have been primarily financed through the issuance of our Preferred Shares. As of the date of this prospectus, we have received gross proceeds of $310.0 million from the issuance of our Preferred Shares. As of June 30, 2026, we had cash, cash equivalents and marketable securities of $207.3 million.

The following table provides information regarding our cash flows for the periods presented (in thousands):

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Financing Activities

During the year ended December 31, 2025,

During the year ended December 31, 2025, financing activities provided $197.0 million of cash. The cash inflows primarily related to the proceeds received from closing both the first and second tranche of our Series A financing round for a total inflow of $200.0 million, partially offset by the payment of $2.2 million of transaction costs and payments on lease obligations of $0.8 million.

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We expect our future funding requirements

requirements to continue to increase over time in connection with our ongoing research and development activities related to our product candidates. To the extent we obtain regulatory approval for any of our product candidates, we also expect to incur significant expenses to market, sell and distribute our approved products. Additionally, upon successful completion of this offering, we will incur additional costs associated with operating as a public company.

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has been no public market for our common shares to the date of this prospectus, we have determined the estimated fair value of our common shares as of the date of each grant. Key considerations impacting the fair value of our common shares include the underlying equity value of the Company, as determined using either an option pricing model, or OPM, or a hybrid method. Key considerations underlying these valuations included the equity value of our company and the respective rights and preferences of our common shares and Preferred Shares, including their dividend rights and liquidation preferences.

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Business 186 changes

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long-acting and ultra-long-acting antibody medicines for patients with serious respiratory and dermatologic diseases, including asthma, COPD, and atopic dermatitis. We estimate these diseases collectively represent a $60 billion peak market opportunity for biologic therapies, as we believe the majority of patients eligible to receive biologic treatment for these diseases remain untreated. Our product candidates can potentially address this significant unmet need, allow for treatment of a broader population of patients, improve efficacy, and improve dosing convenience, outcomes and adherence to treatment. We estimate that these diseases collectively affect more than 100 million people in the United States, EU5, and Japan, and more than 8 million patients are eligible for biologics treatment.

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Our lead program, WIN378, is a an ultra-long-acting and potentially novel fully human monoclonal antibody that inhibits thymic stromal lymphopoietin, or TSLP. TSLP is positioned upstream of multiple inflammatory pathways and is a clinically validated target in respiratory disease. We believe WIN378 has the potential to be a differentiated treatment in asthma and COPD based on a number of factors:

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We have completed a Phase 1 clinical study of WIN378 and are advancing it through active clinical development programs, with multiple data readouts expected across asthma and COPD over the next 24 months.

We use the term "ultra-long-acting" to refer to biologics engineered to remain in the body substantially longer than conventional antibodies. which we anticipate to have A preplanned interim analysis of the Phase 2 portion of the POLARIS-1 study demonstrated a half-life of at least 65 up to 75 days, enabling dosing as infrequently as twice a year, compared with the every-two-week to monthly dosing intervals required by most approved biologic therapies in respiratory disease.

WIN378 has Fc engineering, which involves targeted modifications to the antibody's tail region that switch off unwanted immune-cell recruitment and extend how long the drug stays in the body. In addition to engineering that significantly extends the half-life of the drug, WIN378 has a silenced effector function, achieved through the Fc engineering. This minimizes the potential for negative immune responses such as inflammation and the development of antidrug antibodies (ADAs), which often impact repeat dosing and efficacy. Because antidrug antibodies can alter drug clearance and produce inter-patient PK variability, the low observed ADA rate, being 2 of 40 WIN378-treated participants in the Phase 1 study and 2 of 90 (2.2%) in the interim analysis of the Phase 2 portion of POLARIS-1, combined with the FcRn-mediated half-life extension, supports more consistent and sustained drug exposure and more reliable coverage of the TSLP target between doses.

WIN378 binds a broad epitope footprint on TSLP that spans both its receptor interfaces. To our knowledge, it is the only known investigational drug that blocks TSLP signaling by simultaneously blocking Site 1 (TSLPR) and Site 2 (IL-7R a ) binding to two different sites on TSLP, interfering with and preventing binding of TSLP to both of its co-receptors on the cell surface of epithelial cells and blocking downstream signaling.

It has two-fold improved in vitro potency relative to Tezspire , tezepelumab. In a cell-based assay using human blood cells, WIN378 was approximately twice as potent as Tezspire , tezepelumab, at blocking TSLP-driven release of the inflammatory marker TARC. Based on the interim analysis of the Phase 2 portion of POLARIS-1, WIN378 was four times more potent than Tezspire based on the EC 50 for FeNO. This is an indirect comparison and does not represent results from a head-to-head study; cross-trial comparisons should be interpreted with caution.

We believe that WIN378 is the only therapy that collectively has all of these attributes, and we anticipate to have a half-life of at least 65 days distinguishing it from other marketed and investigational therapies targeting TSLP and potentially contributing to its differentiated clinical profile.

We have completed a Phase 1 clinical study of WIN378 and a pre-planned interim analysis of the phase 2 portion of POLARIS-1. The model-informed Phase 2 portion characterized the dose-response relationship and enrolled 147 patients, exceeding the enrollment target of 120 patients. Following the interim analysis of the first 98 patients that reached at least week 12 of the study, we initiated the Phase 3 portion of POLARIS-1 in September 2026. We are advancing WIN378 through active clinical development programs, with multiple data readouts expected across asthma and COPD through 2029.

WIN378 completed a Phase 1 study, which we anticipate to have demonstrated a half-life of at least 65 days, supporting twice-yearly subcutaneous dosing. In the Phase 1 study, WIN378 demonstrated a low incidence of antidrug antibodies and was well tolerated well-tolerated up to the highest dose studied. No injection site reactions were reported.

WIN378 is currently being evaluated in POLARIS-1, a Phase 2/3 study in severe uncontrolled asthma. A pre-planned interim analysis from the Phase 2 portion of the study was completed in September 2026. The study enrolled a total of 147 patients, exceeding the initial enrollment target of 120 patients, with the interim analysis conducted on the first 98 patients. The interim analysis supports the twice-yearly dosing potential of WIN378. The analysis demonstrated the following at week 24 after a single dose of WIN378:

WIN378 was well tolerated with favorable safety results, and there were no treatment-related serious adverse events, withdrawals or discontinuations observed as of the cut-off date. Adverse events were balanced between active arms and placebo.

Less than 1% of participants experienced injection site reactions and 2.2% developed antidrug antibodies, or ADAs. ADAs had no impact on the pharmacology of WIN378 and were not associated with any clinical signals.

Dose-dependent mean increases in FEV 1 (forced expiratory

volume in one second, a key measure of lung function) of up to 174 mL (placebo-adjusted mean increase up to 256 mL, p=0.033).

Dose-dependent reductions in FeNO (fraction of exhaled nitric oxide, a marker of airway inflammation) of up to 24 ppb (or -43% change, p=0.006). Reductions in FeNO are correlated with reductions in asthma exacerbations.

Reductions in blood eosinophil count, or EOS, of up to 200 cells/ L (or -51% change, p<0.0001).

Near maximal effects seen as early as week 2 and sustained through week 24.

Population pharmacokinetics, or PopPK, demonstrated a half-life of up to 75 days.

Pharmacokinetic-pharmacodynamic modeling demonstrated the enhanced potency of WIN378, which achieved an EC 50 of 0.63 mg/ml for FeNO reduction, a marker of airway inflammation.

WIN378 is currently being evaluated in POLARIS-1, a Phase 2/3 study in severe uncontrolled asthma. An interim analysis from The Phase 2 portion of the study is expected in the second half of 2026 and the primary study results at week 24 are expected in the first half of 2027. The final study results at week 48 will are expected to be available in the second half of 2027. If successful, we plan to initiate Two twice-yearly dose levels were selected for the Phase 3 portion of POLARIS-1, which was initiated in the second half of September 2026 with topline results at week 48 expected in the second half of 2028. and We also plan to initiate a second Phase 3 study (POLARIS-2) in the first half of 2027, with topline results expected in the second half of 2029.

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Based on published and public statements from other companies as well as results from trials to date in which WIN378 was well tolerated well-tolerated in patients and no serious adverse events deemed to be study-related were reported, we believe that WIN378, if it produces favorable safety and efficacy data in future pivotal trials, has the potential to be the first ultra-long-active ultra-long-acting treatment targeting TSLP to seek approval in the United States. However, the results from early trials of a product candidate may not be predictive of the results that will be obtained in later stage trials of the product candidate.

Our second clinical-stage program, WIN027, is a long-acting an ultra-long-acting bispecific antibody that simultaneously targets TSLP and interleukin-13 (IL-13), two clinically validated drivers of inflammatory disease. We believe that dual inhibition of these pathways has the potential to deliver deeper and more durable disease control than targeting either pathway alone. We plan to evaluate this approach across multiple immunological diseases, including COPD and atopic dermatitis. WIN027 has been engineered for a long circulating half-life, with a target dosing interval of every three months or less frequently.

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We believe the central roles of TSLP and IL-13 in

If the Phase 1 healthy volunteer study is successful, We plan to initiate multiple Phase 2 studies, including a globally conducted, dose-ranging study in COPD fully powered on the registrational endpoint of exacerbation rate ratio, in the first half of 2027. Our Phase 2b trial is designed with registrational-quality features, including treatment period, exacerbations as primary endpoint, appropriate key secondary endpoints including lung functional, function, hierarchical type 1 error control, independent data and safety monitoring, and a population aligned with the intended indication. If the Phase 1 healthy volunteer study is successful, We also plan to initiate an a global atopic dermatitis study conducted in the first half of 2027 with our partner Qyuns topline results expected in the second half of 2026. 2028. Additionally, based on our knowledge, Qyuns plans to initiate their Phase 2 studies in asthma, and CRSwNP, and atopic dermatitis in the PRC in the second half of 2026, with topline results expected in 2027 and 2028.

We believe the central roles of TSLP and IL-13 in epithelial-driven inflammation position us to expand our franchise beyond our initial focus on asthma, COPD, and atopic dermatitis, both through entry into adjacent indications and through broader use across the severity spectrum within our core diseases. Potential future indications supported by the underlying biology include chronic rhinosinusitis with nasal polyps, eosinophilic esophagitis, chronic spontaneous urticaria, and other type-2-mediated allergic and inflammatory diseases, as well as combination or sequencing strategies across WIN378 and WIN027.

Our development plans for WIN378 and WIN027 include ten Phase 2 and Phase 3 clinical readouts through 2029, not including four additional readouts for WIN027 based on studies conducted by our partner, Qyuns.

AD=atopic dermatitis, COPD=chronic obstructive pulmonary disease, HV=healthy volunteer, TLR=topline results, W=week Additional bispecific programs are in the lead optimization phase. The current program is a next-generation bispecific targeting T2 and non-T2 pathways, with two complementary cytokines. Work to date has included the evaluation of various formats, production at small scale, and the evaluation of productivity, purity and light chain mispairing. Further work has characterized the blocking of both cytokines and a HELA cell-based potency assay has been developed and used to compare the bispecifics' potencies to monospecific benchmarks. Of the three formats evaluated, a lead pre-clinical target format has been identified and selected, with potential across skin and respiratory indications, including atopic dermatitis, asthma, and COPD and other inflammatory and fibrotic skin and lung diseases. We expect to initiate Phase 1 clinical development for these potential skin and respiratory indications in the next 18 months, subject to standard regulatory requirements. The lead format demonstrating benchmark-comparable affinity, cellular potency and manufacturability has been selected and is currently being engineered for half-life extension prior to characterization in nonhuman primate studies.

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We plan to initiate a Phase 2 study in atopic dermatitis in the second half of 2026 with topline results in the second half of 2027. We also plan to initiate a Phase 2b in COPD, fully powered on the registrational endpoint of exacerbation rate ratio, in the first half of 2027.

We integrate commercial strategy into our development

We integrate commercial strategy into our development programs to maximize the value of our molecules. We holistically evaluate the scientific, technical, clinical, and commercial strategy and plans for each of our programs and our portfolio to ensure we are advancing differentiated programs to address the significant unmet needs in immunology.

mission is to transform the treatment paradigm for patients living with chronic inflammatory diseases through the development of differentiated biologic therapies targeting validated disease pathways. We are advancing a portfolio of long-acting and ultra-long-acting antibody-based product candidates designed to improve clinical outcomes, increase convenience for patients and expand access to biologic treatment across large, underserved patient populations, with an initial focus on respiratory and dermatological diseases. The key elements of our strategy include:

Advance WIN378, our lead ultra-long-acting anti-TSLP monoclonal antibody, through clinical development for the treatment of asthma, a severe disease with low adherence to short-acting biologics. We believe WIN378 has the potential to be a differentiated anti-TSLP therapy based on its potent inhibition of a clinically validated target, twice-yearly dosing profile, low immunogenicity and unique dual-site binding to the TSLP ligand. Through our ongoing Phase 2/3 POLARIS-1 asthma study, we aim to establish WIN378 as a differentiated treatment option for patients with severe asthma, including those with low eosinophil counts who remain underserved by current biologic therapies. We expect The pre-planned interim results from analysis of the phase 2 portion of POLARIS-1 demonstrated significant improvements in the second half lung function and airway inflammation with twice-yearly dosing of 2026 WIN378. Near maximal effects were seen as early as week 2 and sustained through week 24. WIN378 was well tolerated with favorable safety results — there were no treatment-related serious adverse events, withdrawals or discontinuations; adverse events were balanced between active arms and placebo, with low rates of injection site reactions and antidrug antibodies. The pharmacology analysis demonstrated a half-life of up to 75 days, with clinical effects consistent with twice-yearly dosing. The next data readout is the primary analysis at week 24 in the first half of 2027. The final study results at week 48 will be available in the second half of 2027. The Phase 3 portion of the study is expected to begin was initiated in the second half of September 2026 evaluating two twice-yearly dose levels of WIN378, with topline results at week 48 expected in the second half of 2028. A second Phase 3 study in asthma (POLARIS-2) is planned to begin in the first half of 2027 with topline results expected in the second half of 2029.

Progress WIN378 through clinical development for the treatment of COPD, an underserved patient population with significant unmet need . COPD remains a highly prevalent and difficult-to-treat disease with limited biologic treatment options and low biologic utilization. We believe TSLP is a compelling target in COPD based on emerging clinical evidence from Tezspire , tezepelumab's recent Phase 2a proof-of-concept data supporting the role of upstream epithelial inflammation in disease exacerbations and progression. Currently, we are evaluating WIN378 in our Phase 2 SIRIUS trial for COPD with topline results expected in the second half of 2027.

Advance WIN027, our long-acting anti-TSLP anti-IL-13 bispecific antibody, through clinical development for the treatment of COPD and atopic dermatitis, diseases in which there is the potential for significant improvement over currently approved biologics . We believe dual blockade of TSLP and IL-13 may provide deeper and more durable disease control than inhibition of either pathway alone. We are advancing WIN027 through an ongoing Phase 1 trial in healthy volunteers. Based on blinded interim data as of June 2026, we have observed a 62-day half-life, low immunogenicity, and favorable safety results, with full pharmacokinetic and immunogenicity data expected in the first half of 2027. We plan to initiate a global Phase 2b in COPD, fully powered on the registrational endpoint of exacerbation rate ratio, in the first half of 2027. Topline results are expected in the first half of 2029. We also plan to initiate a Phase 2 study in atopic dermatitis in the first half of 2027 with topline results expected in the second half of 2028. Additionally, based on our knowledge, Qyuns plans to initiate their Phase 2 studies in asthma, CRSwNP, and atopic dermatitis in the PRC in the second half of 2026, with topline results expected in 2027 and 2028.

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Our decision to pursue any

Our decision to pursue any of these opportunities will depend on the outcome of our ongoing and planned clinical trials, further clinical evaluation in the relevant indications, and regulatory feedback.

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Windward Bio holds global rights to WIN378 excluding Greater China and certain Asian markets ** Exclusivity based on pending applications and anticipated patent extensions *** Asthma and CRSwNP Phase 2 studies are planned in the PRC only, conducted and funded by Qyuns Therapeutics **** Lead optimization stage with potential in respiratory and dermatology; see "—Additional bispecific programs" for more information IP=intellectual property, mAb=monoclonal antibody WIN378 is an ultra-long-acting and potentially novel fully human monoclonal antibody that is designed to inhibit the TSLP ligand. This clinically validated target plays a key role in the development and progression of a wide array of immunological diseases, including asthma and COPD. WIN378 has been engineered to achieve half-life extension and silenced effector function. In preclinical studies, WIN378 has been observed to have greater potency than the currently approved anti-TSLP treatment, has two binding sites to TSLP and fully overlaps the same binding site as Tezspire , tezepelumab.

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Based on published and public statements

WIN378 is currently being evaluated in POLARIS-1, a Phase 2/3 study in severe uncontrolled asthma. An A pre-planned interim analysis from the Phase 2 dose-finding portion of the study is expected was completed in the second half of 2026, and the primary study results at week 24 are expected in the first half of 2027. The final study results at week 48 will be available in the second half of 2027. If successful, Following dose selection based on the interim analysis, we plan to initiate a initiated the Phase 3 portion of POLARIS-1 in the second half of September 2026 with topline results expected in the second half of 2028 and, we also plan to initiate a second Phase 3 study (POLARIS-2) in the first half of 2027 with topline results expected in the second half of 2029. Separately, a Phase 2 study of WIN378 in COPD, SIRIUS, was initiated in June 2026 with topline results expected in the second half of 2027. We have observed the following results in the Phase 1 clinical trial for WIN378: an extended half-life supporting twice-yearly subcutaneous dosing, a low rate of antidrug antibodies, and favorable safety and tolerability results up to the highest dose tested. In the interim analysis of the Phase 2 portion of POLARIS-1, WIN378 demonstrated significant improvements in lung function and airway inflammation with twice-yearly dosing of WIN378. Near maximal effects were seen as early as Week 2 and sustained through Week 24. While these results may not translate to similar safety or efficacy results in our the ongoing POLARIS Phase 2/3 study 3 portions of our POLARIS studies in patients with asthma or our SIRIUS Phase 2 study in patients with COPD, we believe WIN378 is differentiated from currently approved treatments primarily through its potential for twice-yearly subcutaneous dosing.

Based on published and public statements from other companies as well as results from trials to date in which WIN378 was well tolerated in patients and no serious adverse events deemed to be study-related were reported, we believe that WIN378, if it produces favorable safety and efficacy data in future pivotal trials, has the potential to be the first ultra-long-active ultra-long-acting treatment targeting TSLP to seek approval in the United States. However, the results from early trials of a product candidate may not be predictive of the results that will be obtained in later stage trials of the product candidate.

We have licensed the global rights

We have licensed the global rights (excluding Greater China and certain Asian countries) for WIN378 from Kelun-Biotech (also known as SKB378) and HBM (also known as HBM9378). Both companies equally own the underlying WIN378 intellectual property, are equal parties to the license agreement with Windward Bio and share equal rights in their territory. We retain all decision-making in our territory and have certain decision rights in their territory.

WIN027 is a long-acting, an ultra-long-acting, potentially novel, humanized bispecific monoclonal antibody with high-binding affinity for TSLP and IL-13, two well-validated targets in immunological conditions. WIN027 has been engineered to achieve an extended half-life that enables less frequent dosing. Through this dual, long-acting inhibition, WIN027 is designed to treat conditions such as COPD and atopic dermatitis, potentially delivering deeper and more durable disease control than existing biologics. WIN027 has the potential to expand our portfolio to dermatological diseases, including atopic dermatitis.

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WIN027 is currently in a Phase 1 HV study with INDs open in the

WIN027 is currently in a Phase 1 HV study with INDs open in the United States, Australia and the PRC assessing safety and pharmacokinetics. We expect that the next data readout for WIN027 will be the full Phase 1 results in the first half of 2027. Based on blinded interim data as of June 2026, we have observed a 62-day half-life, low immunogenicity, a low rate of injection site reactions, and favorable safety and tolerability results, with full pharmacokinetic and immunogenicity data expected in the first half of 2027. We plan to initiate multiple Phase 2 studies. We are conducting plan to conduct a global, dose range finding study in COPD, fully powered on the registrational endpoint of exacerbation rate ratio, which we plan to initiate in the first half of 2027. Topline results are expected in the first half of 2029. Our Phase 2b trial is designed with registrational-quality features, including treatment period, exacerbations as primary endpoint, appropriate key secondary endpoints including lung functional, hierarchical type 1 error control, independent data and safety monitoring, and a population aligned with the intended indication. Together with our partner Qyuns, We also plan to initiate an additional Phase 2 study in atopic dermatitis in the second first half of 2026 2027 with initial data expected in the second first half of 2027 2028 . Additionally, based on our knowledge, Qyuns plans to initiate their Phase 2 studies in asthma, and CRSwNP, and atopic dermatitis in the PRC in the second half of 2026, with topline results expected in 2027 and 2028.

Additional bispecific programs are in the lead optimization phase. The current program is a next-generation bispecific targeting T2 and non-T2 pathways, with two complementary cytokines. Work to date has included the evaluation of various formats, production at small scale, and the evaluation of productivity, purity and light chain mispairing. Further work has characterized the blocking of both cytokines and a HELA cell-based potency assay has been developed and used to compare the bispecifics' potencies to monospecific benchmarks. Of the three formats evaluated, a lead pre-clinical target format has been identified and selected, with potential across skin and respiratory indications, including atopic dermatitis, asthma, and COPD and other inflammatory and fibrotic skin and lung diseases. We expect to initiate Phase 1 clinical development for these potential skin and respiratory indications in the next 18 months, subject to standard regulatory requirements. The lead format demonstrating benchmark-comparable affinity, cellular potency and manufacturability has been selected and is currently being engineered for half-life extension prior to characterization in nonhuman primate studies.

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Despite the relatively limited utilization of

utilization of biologic therapies in severe asthma, the asthma biologic therapeutics market is already substantial and is expected to grow as use of advanced therapies expands. In 2025, we estimate global sales of biologics for severe asthma were approximately $14 billion and we estimate they will reach $30 billion at peak in combination with COPD biologic treatment. We believe that atopic dermatitis represents a portfolio expansion opportunity beyond asthma and COPD. In 2025, global sales of biologics and novel oral treatments for atopic dermatitis were approximately $15 billion and we estimate they will reach $30 billion at peak as more eligible patients receive treatment.

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1. Package inserts 2. Maddux et al. Persistence of

of Asthma Biologic Use in a US Claims Database. Ann Allergy Asthma Immunol. 2021 December; 127(6): 648–654 3. Two-year persistence and compliance with osteoporosis therapies among postmenopausal women in a commercially insured population in the United States.Arch. Osteoporos.2017,12, 22. 4. www.leqviohcp.com 5. Adherence to and Persistence with Disease-Modifying Therapies for Multiple Sclerosis Over 24 Months: A Retrospective Claims Analysis. Neurol Ther, 2022 11:337–351 Poor persistency can result in worse outcomes for patients with severe asthma, including increased exacerbations and suboptimal symptom control. A study demonstrated that patients who discontinued asthma biologics had a 47% increase in emergency department visits and a 71% increase in hospitalizations compared to patients who were fully adherent to treatment. Discontinuation of treatment also resulted in significantly increased costs. WIN378 may be able to deliver improved real-world outcomes through improved persistency that reduces the risk of exacerbations.

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1. IQVIA Rx analysis 2. Amgen and AstraZeneca reported sales

1. Amgen and AstraZeneca reported sales

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We believe that WIN027 offers a differentiated opportunity

We believe that WIN027 offers a differentiated opportunity to move beyond single-pathway inhibition by simultaneously neutralizing TSLP and IL-13, while offering the convenience of a minimum of every three months dosing. By blocking two mediators that operate at distinct points in the type-2 inflammatory cascade, an upstream epithelial alarmin together with a key downstream effector cytokine, WIN027 has the potential to achieve more complete suppression of airway inflammation than agents directed at either target alone. The addition of direct IL-13 neutralization is designed to address the tissue-level consequences of type-2 inflammation that upstream blockade alone may not fully resolve, including goblet cell metaplasia and mucus hypersecretion that drive mucus plugging, airway smooth muscle dysfunction and hyperresponsiveness, and the structural remodeling and small airways involvement that contribute to persistent airflow obstruction and disease progression. We believe this dual-pathway design may extend clinical benefit across both type-2 high and type-2 low patients, and its extended half-life format is intended to support infrequent administration, positioning WIN027 to be a differentiated therapy for patients inadequately controlled on current biologics or with more advanced lung disease.

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blockade has demonstrated meaningful reductions in exacerbations in both asthma and, more recently, COPD, supporting TSLP as a clinically validated target. Based on the results observed in separate clinical studies, Tezspire , tezepelumab, reductions in annualized asthma exacerbation rates were directionally higher relative to dupilumab in all key sub-populations defined by eosinophilic counts.

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been engineered to have a significantly enhanced half-life over clinically approved antibodies and to be dosed twice-yearly. Ordinarily, proteins taken up into cells are routed to the lysosome and degraded, which is what limits the lifespan of most circulating proteins. Immunoglobulins escape this fate: after an antibody is taken into a cell, its Fc region binds the neonatal Fc receptor, or FcRn, inside the acidic environment of the early endosome. This binding diverts the antibody away from degradation and returns it to the cell surface, where the neutral pH of the blood releases it back into circulation intact. This pH-dependent capture and release, tight binding in the acidic endosome, release at the neutral pH of plasma, is what gives IgG antibodies their characteristically long half-life of several weeks, far longer than most other proteins.

Engineering the Fc to bind FcRn more tightly at the acidic pH of the endosome improves the recycling that protects antibodies from degradation, extending serum half-life and enabling less frequent dosing. WIN378 uses an N434A substitution in the Fc portion of the molecule to achieve a meaningfully higher affinity to FcRn than the unmodified comparator (K D 5.7 nM versus 13.8 nM). When engineered into WIN378, we anticipate Consistent with this modification to have a human terminal design, the observed half-life of at least 65 WIN378 was up to 75 days based on the pre-planned interim analysis of the Phase 2 portion of POLARIS-1. This molecular modification was used previously in approved antibodies such as crovalimab and satralizumab demonstrating that this particular form of FcRn engineering translates reliably from design into an approved product with extended dosing intervals.

WIN378 has been engineered for low

WIN378 has been engineered for low immunogenicity and a potentially enhanced safety, tolerability and pharmacokinetic variability. For an anti-TSLP neutralizing antibody like WIN378, the therapeutic role is performed entirely by the antigen-binding end of the molecule: it captures soluble TSLP and prevents it from engaging its receptor. The antibody's Fc region is the tail of the molecule that normally recruits the rest of the immune system by binding the Fc g receptor expressed by immune cells as well as activating complement. This interaction plays no useful part in the therapeutic mechanism of WIN378 and leaving it active carries risk because TSLP is produced by, and can be found associated with, epithelial and immune cells. This could in principle provoke unwanted inflammation, none of which is required to neutralize the cytokine.

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results demonstrated that WIN378 was generally well tolerated, as all treatment-emergent adverse events were Grade 2 or lower, showed no trend of increasing frequency with dose, and were reported at a comparable overall rate in the WIN378 and placebo groups, and showed no trend of increasing frequency with dose. The pharmacokinetics, or PK, was linear, and exposures increased in an approximately dose-proportional manner. The observed serum half-life was up to 66 65 days and population-pharmacokinetic modeling supports dosing as infrequently as twice a year. The antidrug-antibody incidence was also observed to be low (4%), and only 2 of 40 WIN378-treated participants, one of which was a transient response, were observed to have antidrug antibodies. There were no associated safety signals reported and no observed effect on pharmacokinetics.

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is designed for efficient use of patients to generate information to select doses to be used in the pivotal program. It is a randomized, double-blind, placebo-controlled dose-ranging study enrolling approximately 136 participants, randomized in an overall 3:1:1:3 ratio to receive doses of WIN378, or placebo, administered as two subcutaneous doses 24 weeks apart over a 48-week period. Population pharmacokinetic and pharmacodynamic modeling supports our twice a year dosing by projecting steady-state concentrations associated with predicted exacerbation-rate reductions as well as changes in relevant biomarkers.

Our Phase 2 asthma study (POLARIS-1, WB-2101) is a model-informed dose-finding design, summarized below.

Our planned first pivotal Phase 3 asthma study (POLARIS-1) is summarized below.

The Phase 2 portion of the study

study is designed for efficient use of patients to generate information to select doses to be used in the pivotal program. It is a randomized, double-blind, placebo-controlled dose-ranging study, randomized in an overall 3:1:1:3 ratio to receive doses of WIN378, or placebo, administered as two subcutaneous doses 24 weeks apart over a 48-week period. The randomization ratio is based on our application of the MCP-Mod (Multiple Comparison Procedure – Modeling) methodology. to the dose-ranging analysis of our Phase 2 programs. MCP-Mod is a statistical approach for the design and analysis of dose-finding studies that combine multiple comparison procedures with dose-response modeling. MCP-Mod makes more efficient use of dose-ranging data and supports more robust dose selection than conventional pairwise comparisons. The methodology has been formally qualified by the European Medicines Agency and is recognized by the U.S. Food and Drug Administration as a fit-for-purpose approach to dose finding.

The Phase 2 is designed to characterize the pharmacokinetics, safety, immunogenicity, and pharmacodynamic activity of WIN378, including its effects on biomarkers of airway inflammation, such as fractional exhaled FeNO and EOS, and on lung function as measured by FEV1. as well as blood eosinophil count (BEC), a serum marker of inflammation. Data from Phase 2 will was used to inform selection of the dose levels to be carried into the Phase 3 portion of POLARIS-1 and into the subsequent second Phase 3 (POLARIS-2). The first POLARIS-1 Phase 2 participant was randomized in August July 2025, and a total of 147 participants had been were randomized by May 2026, exceeding the initial enrollment target of 120 patients. A pre-planned interim analysis is scheduled to occur was completed in the second half of 2026 and after the first 98 patients had reached at least week 12. The primary study results at week 24 are expected in the first half of 2027. The final study results at week 48 will be available in the second half of 2027.

Interim Results from the Phase 2 Portion of POLARIS-1

time of the interim analysis, 57 participants were randomized to placebo and 17, 17, and 56 participants randomized to WIN378 150 mg, 300 mg, and 600 mg, respectively. Baseline demographics and disease characteristics were consistent with an uncontrolled, moderate-to-severe asthma population with persistent airway obstruction despite treatment with medium- to high-dose inhaled corticosteroids and at least one additional controller medication.

Study design of the Phase 2 portion of POLARIS-1, a model-informed dose-finding design, is summarized below.

Ly N, et al. J Clin Pharmacol 2021;61(7):901–912. Tezepelumab PK/PD modelling to guide Phase 3 dose selection.

WIN378 was well tolerated with favorable safety results, and there were no treatment-related serious adverse events, withdrawals or discontinuations observed as of the cut-off date. Adverse events were balanced between active arms and placebo. Less than 1% of participants experienced injection site reactions and 2.2% developed antidrug antibodies (ADAs), a measure of immunogenicity. ADAs had no impact on the pharmacology of WIN378 .

The observed half-life of WIN378 in the Phase 2 population was up to 75 days . The pharmacokinetics of WIN378 were linear.

WIN378 produced rapid and sustained, dose-dependent improvements in markers of airway inflammation and in lung function through Week 24. Mean changes in FeNO from baseline to week 24 of up to -24.4 ppb compared with -6.0 ppb for placebo (placebo-adjusted differences of -18.3 ppb; p<0.01). Reductions in FeNO occurred as early as Week 2 and were sustained through Week 2.

Pre-bronchodilator FEV1 improved from baseline to Week 24 by up to 174 mL compared with a decline of 93 mL for placebo (placebo-adjusted differences of 256 mL;

p<0.05). Increases in FEV 1 occurred as early as Week 2 and were sustained through week 24.

Reductions in blood eosinophil count (EOS) of up to 200 cells/ L (or -51% change, p<0.0001) were also seen at the interim analysis.

The pharmacodynamic effects observed in the interim analysis were consistent with the improved potency of WIN378 predicted by preclinical assays. Based on the observed FeNO response, the half-maximal effective concentration, or EC50, of WIN378 was 0.63 g/mL, approximately four-fold lower than the 2.5 g/mL reported for tezepelumab, the currently approved anti-TSLP antibody. This is an indirect comparison and does not represent results from a head-to-head study; cross-trial comparisons should be interpreted with caution. In addition, 100% of patients taking the 300mg and 600mg dose of WIN378 had a 90% FeNO response at Cavg.ss after the first dose over 24 weeks versus approximately 50% of patients receiving the approved dose of tezepelumab.

The observed pharmacokinetics

and pharmacodynamics support twice-yearly dosing. Two twice-yearly dose levels were selected for Phase 3.

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and 106 more changes in the filing

Management 10 changes

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Our audit committee will assist our board of directors in

in overseeing the integrity of our financial statements, the appointment, qualifications, independence and performance of our external auditors, our internal control and risk management processes, the design and implementation of our internal audit function, the reports of the external auditors as well as the compliance by us with legal and regulatory requirements as set forth in the charter of the audit committee.

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Our compensation committee

committee will review and propose to our board of directors our compensation principles as well as the compensation for the members of the board of directors, the Chief Executive Officer and other members of the executive committee. Pursuant to our articles of association, our compensation committee consists of no less than members of our board of directors.

Following the completion of the offering, our

offering, our compensation committee will consist of , and . will serve as chair of the compensation committee. Under Swiss law, the members of our compensation committee must be elected by our general meeting of shareholders and the aggregate amount of compensation of our board of directors and of our executive committee must be approved by our general meeting of shareholders, in each case commencing with our first annual general meeting of shareholders as a public company to be held in 2027. Our board of directors appoints the chair of the compensation committee and in case of any vacancies may appoint substitute members from among the members of the board of directors, in each case until completion of the next annual general meeting of shareholders.

The compensation committee's

committee's principal duties and responsibilities will include, among others:

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Share Reserve . Our ESPP authorizes the issuance of

Share Reserve . Our ESPP authorizes the issuance of common shares under purchase rights granted to our employees or to employees of any of our designated affiliates. The number of common shares reserved for issuance will automatically increase on January 1 of each year for a period of ten years, beginning on January 1, 2027 and continuing through January 1, 2036, by the lesser of (i) % of the total number of our common shares outstanding on December 31 of the immediately preceding year; and (ii) common shares, except before the date of any such increase, our board of directors may determine that such increase will be less than the amount set forth in clauses (i) and (ii).

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Shares eligible for future sale 2 changes

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All of our directors and executive officers and certain shareholders have agreed, subject to limited exceptions, with the underwriters not to offer, pledge, announce the intention to sell, sell, contract to sell, sell any option or contract to purchase, purchase any option or contract to sell, grant any option, right or warrant to purchase or otherwise dispose of, directly or indirectly, or enter into any swap or other agreement that transfers, in whole or in part, any of the economic consequences of ownership of our common shares or such other securities for a period of 180 days after the date of this prospectus, without the prior written consent of Jefferies LLC, TD Securities (USA) LLC and Piper Sandler & Co. See "Underwriting." Following the lock-up periods set forth in the agreements described above, and assuming that the representatives of the underwriters do not release any parties from these agreements, all of the common shares that are held by these parties as of the date of this prospectus will be eligible for sale in the public market in compliance with Rule 144 under the Securities Act.

In general, persons who have beneficially owned common shares for at least six months are entitled to sell their securities without registration with the SEC under an exemption from registration provided by Rule 144 under the Securities Act.

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Plan of distribution 9 changes

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Prior to this offering, there has not been a public market for our common shares. Consequently, the initial public offering price for our common shares will be determined by negotiations between us and the representatives. Among the factors to be considered in these negotiations will be prevailing market conditions, our financial information, market valuations of other companies that we and the underwriters believe to be comparable to us, estimates of our business potential, the present state of our development and other factors deemed relevant.

We offer no assurances that the initial public offering price will correspond to the price at which the common shares will trade in the public market subsequent to the offering or that an active trading market for the common shares will develop and continue after the offering.

We have applied to list our common shares on the Nasdaq under the trading symbol "WWB".

on the Nasdaq under the trading symbol "WWB".

If you purchase common shares offered in this prospectus, you may be required to pay stamp taxes and other charges under the laws and practices of the country of purchase, in addition to the offering price listed on the cover page of this prospectus.

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We have granted to the underwriters an

We have granted to the underwriters an option, exercisable for 30 days from the date of this prospectus, to purchase, from time to time, in whole or in part, up to an aggregate of shares from us at the public offering price set forth on the cover page of this prospectus, less underwriting discounts and commissions. If the underwriters exercise this option, each underwriter will be obligated, subject to specified conditions, to purchase a number of additional shares proportionate to that underwriter's initial purchase commitment as indicated in the table above. This option may be exercised only if the underwriters sell more shares than the total number set forth on the cover page of this prospectus.

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We, our officers, directors and holders of

We, our officers, directors and holders of all or substantially all our outstanding share capital have agreed, subject to specified exceptions, not to directly or indirectly:

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Note 1: Organization and business 3 changes

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Company has two wholly owned subsidiaries (directly or indirectly) (the "Subsidiaries"), Windward Bio AG and Windward Bio Inc (collectively "Windward Bio" or the "Group"). The Group also controls LE2025 Therapeutics AG ("LE2025") through contractual arrangements. The Company is the ultimate parent of Windward Bio. Windward Bio is a clinical-stage biotechnology company with deep discovery, development, and commercialization expertise, committed to transforming the treatment of people living with advanced immunological conditions. Its lead program is WIN378, a potentially novel, long-acting, anti-TSLP monoclonal antibody. The pipeline also includes WIN027, a clinical-stage, long-acting anti-TSLPxIL-13 bi-specific, which has broad therapeutic application across immunological diseases.

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The financial position

position and performance of Windward Bio was particularly affected by the following events and transactions during the year ended December 31, 2025 and period from July 5, 2024 to December 31, 2024. The parties in the License and Collaboration Agreements below are individually defined as a "Licensor" and collectively as "Licensors":

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Note 7: Intangible assets (including IPR&D) 2 changes

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Additional payments to Qyuns may be required, contingent on the occurrence or non-occurrence of future events. These events include certain development-related milestones of up to $100.0 million and sales-related milestones of up to $570.0 million as well as mid-single digit to high-single digit tiered royalties to Qyuns.

As of December 31, 2025, the assets are not yet ready for use as neither of the assets have obtained regulatory approval in any markets. The carrying amount and net book value are detailed below:

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Note 24: Subsequent events 10 changes

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Consolidated Interim Statement of Profit or Loss and Other

(In thousands of USD, except per share data)

CONSOLIDATED STATEMENT OF PROFIT OR LOSS

Research and development expenses

General and administrative expenses

Foreign exchange differences, net

Loss before income taxes

Other comprehensive income or loss, net of income tax

Items that will not be reclassified subsequently to profit or loss:

Consolidated Interim Statement of Profit or Loss and Other Comprehensive (In thousands of USD, except per share data) NOTES FOR THE SIX MONTHS ENDED JUNE 30, 2026 FOR THE SIX MONTHS ENDED JUNE 30, 2025 CONSOLIDATED STATEMENT OF PROFIT OR LOSS Research and development expenses (30,133 ) (13,325 ) General and administrative expenses (14,539 ) (9,951 ) Operating loss (44,672 ) (23,276 ) Financial income 2,164 Financial expense (7 ) (2 ) Foreign exchange differences, net (166 ) (145 ) Loss before income taxes (42,681 ) (22,750 ) Income taxes — Net loss (42,636 ) (22,750 ) Other comprehensive income or loss, net of income tax Items that will not be reclassified subsequently to profit or loss:

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Exhibits 1 change

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Previously submitted.

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