Registration Statement No. 333-299608

Cover page 2 changes

As filed with the U.S. Securities and Exchange Commission on October 23, 30, 2026.

Registration Statement No. 333- 333-299608

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Prospectus summary 25 changes

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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 no treatment-related serious adverse events were observed. The pre-planned interim analysis of the Phase 2 portion of POLARIS-1 demonstrated the following results:

Windward Bio holds global rights to WIN378 excluding Greater China and certain Asian markets ** Exclusivity based on pending applications and anticipated patent extensions *** Lead optimization stage with potential in respiratory and dermatology; see "—Additional bispecific programs" on page 6 for more information COPD = chronic obstructive pulmonary disease, IP=intellectual property, mAb=monoclonal antibody In addition to the studies we are conducting for WIN027, our partner and licensor, Qyuns, has initiated its Phase 2 program including studies in atopic dermatitis and CRSwNP in September 2026 in the PRC and plans to begin a Phase 2 study in asthma by the end of the year.

WIN378 is an ultra-long-acting and

Windward Bio holds global rights to WIN378 excluding Greater China and certain Asian markets ** Exclusivity based on pending applications and anticipated patent extensions *** These studies are conducted and funded by Qyuns Therapeutics; see "—WIN027" on page 5 for more information **** Lead optimization stage with potential in respiratory and dermatology; see "—Additional bispecific programs" on page 5 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 nonclinical 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.

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 the second half of 2026. Following dose selection based on the interim analysis, we initiated the Phase 3 portion of POLARIS-1 in September 2026, with topline results expected in the first half of 2029. Study start-up activities were initiated in September 2026 for a second Phase 3 study (POLARIS-2), which is planned to begin patient recruitment in the first half of 2027 with topline results expected in the first 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 no treatment-related serious adverse events were observed. The pre-planned interim analysis of the Phase 2 portion of POLARIS-1 demonstrated the following results:

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We have licensed global rights (excluding Greater China) for WIN027 from Qyuns and have the right to use and reference Qyuns' data in connection with our development of WIN027 and our pursuit and maintenance of regulatory approvals outside Greater China. For more information, see the section titled "Business—Intellectual Property" included elsewhere in this prospectus.

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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.

The graph below shows the anticipated timing of certain key clinical development milestones for WIN378 and WIN027, including planned study initiations expected to be funded with the net proceeds from this offering and anticipated clinical data readouts. The timing of these milestones is inherently uncertain and subject to numerous risks, delays and changes. See "Risk Factors" for additional information regarding risks that could delay the development of WIN378 and WIN027 or our achievement of these anticipated milestones.

Qyuns initiated its Phase 2 program including studies in atopic dermatitis and CRSwNP in September 2026 in the PRC and plans to begin a Phase 2 study in asthma by the end of the year. Topline results from these studies are expected over the course of 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 nonclinical target format has been identified and selected, with potential across skin and respiratory indications, including atopic dermatitis, asthma, 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 is currently being engineered for half-life extension prior to characterization in nonhuman primate studies.

Although asthma, COPD and atopic dermatitis encompass

large and growing markets, we estimate that the biologics treatment rate among eligible patients remains low—approximately 20% in severe asthma, approximately 1% in moderate-to-severe COPD, and approximately 15% in moderate-to-severe atopic dermatitis.

Although asthma, COPD and atopic dermatitis encompass large and growing markets, we estimate that the biologics treatment rate among eligible patients remains low—approximately 20% in severe asthma, approximately 1% in moderate-to-severe COPD, and approximately 15% in moderate-to-severe atopic dermatitis. 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, and 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. We believe that therapies such as WIN378 and WIN027 are capable of addressing a broad range of patient types and offering more convenient dosing regimens that can improve adherence to treatment and deliver enhanced real-world outcomes.

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Preliminary Estimated Unaudited Cash, Cash Equivalents and Marketable Securities Based on our current estimates, we had approximately $181.8 million in cash, cash equivalents and marketable securities as of September 30, 2026. However, this estimate is preliminary, unaudited and may change, was prepared by management based on the most current information available to management, and is subject to the completion of our financial closing procedures for the three months ended September 30, 2026.

This estimate should not be viewed as a substitute for financial statements prepared in accordance with IFRS, as issued by the IASB, and is not necessarily indicative of the results to be achieved in any future period. Accordingly, you should not draw any conclusions based on the foregoing estimate and should not place undue reliance on this preliminary estimate. We assume no duty to update this preliminary estimate except as required by law.

The preliminary estimate as of September 30, 2026 set forth above has been prepared by, and is the responsibility of, management. Ernst & Young AG, our independent registered public accounting firm, has not audited, reviewed, compiled or performed any procedures with respect to such preliminary data. Accordingly, Ernst & Young AG does not express an opinion or any other form of assurance with respect thereto.

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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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In addition, foreign private issuers are not required to file their annual report on Form 20-F until four months after the end of each fiscal year, while U.S. domestic issuers that are accelerated filers are required to file their annual report on Form 10-K within 75 days after the end of each fiscal year.

Our status as a foreign

Our status as a foreign private issuer also exempts us from compliance with certain laws and regulations of the SEC and certain regulations of the Nasdaq Global Market, or Nasdaq. Consequently, we are not subject to all of the disclosure requirements applicable to U.S. public companies. For example, we are exempt from certain rules under the Exchange Act that regulate disclosure obligations and procedural requirements related to the solicitation of proxies, consents or authorizations applicable to a security registered under the Exchange Act. Our executive officers, directors and principal shareholders are also exempt from the "short-swing" profit recovery provisions of Section 16(b) of the Exchange Act. Moreover, we are not required to file periodic reports and financial statements with the SEC as frequently or as promptly as U.S. public companies. Accordingly, there may be less publicly available information concerning our company than there is for U.S. public companies.

In addition, foreign private issuers are not required to file their annual report on Form 20-F until four months after the end of each fiscal year, while U.S. domestic issuers that are accelerated filers are required to file their annual report on Form 10-K within 75 days after the end of each fiscal year. Foreign private issuers are also exempt from the Regulation Fair Disclosure, aimed at preventing issuers from making selective disclosures of material information. Additionally, Nasdaq rules allow foreign private issuers to follow home country practices in lieu of certain of Nasdaq corporate governance rules. As a result, our shareholders may not have the same protections afforded to shareholders of companies that are subject to all Nasdaq corporate governance requirements.

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common shares issuable under our 2026 Employee Share Purchase Plan, or the ESPP; and ∎ 50,700 common shares we hold in treasury.

common shares issuable under our 2026 Employee Share Purchase Plan, or the ESPP; and ∎ 50,700 common shares we hold in treasury and an additional number of common shares to be issued in connection with the capital increases as further described in the section titled "Description of Share Capital and Articles of Association" such that the total number of common shares to be held in treasury upon completion of this offering corresponds to 10% of the share capital registered in the commercial register of the Canton of Basel-Stadt, Switzerland, or the Commercial Register, immediately after completion of this offering.

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a -to- reverse split of our registered shares that became effective on no issuance or exercise of outstanding options or settlement of outstanding restricted share units after June 30, the conversion of all our 53,429,037 outstanding preferred shares into the same number of common shares at the same nominal value immediately prior to the completion of this offering, or the Preferred Share Conversion;

the settlement of all of our 397,495 outstanding Series B Warrants for common shares immediately prior to the completion of this offering (based on a cashless exercise at the midpoint of our estimated offering price range), or the Series B Warrant Settlement;

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Risk factors 21 changes

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There has been no public market for our common shares prior to this offering. The initial public offering price for our common shares was determined through negotiations among the underwriters and us and may vary from the market price of our common shares following this offering. An active or liquid market in our common shares may not develop upon closing the completion of this offering or, if it does develop, it may not be sustainable. The lack of an active market may impair the value of your common shares, your ability to sell your common shares at the time you wish to sell them and the prices that you may obtain for your common shares. An inactive market may also impair our ability to raise capital by selling our common shares and our ability to acquire other companies, products, or technologies by using our common shares as consideration.

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in certain cases, allow our board of directors to place up to an additional number of common shares corresponding to 50% of the share capital registered in the Commercial Register immediately after completion of this offering to be issued by way of a capital increase within our capital range, and rights to acquire an additional number of common shares corresponding to % of the share capital registered in the Commercial Register immediately after completion of this offering to be issued out of our conditional capital for financing, acquisitions and other purposes (approximately % and %, respectively, of the expected outstanding share capital after completion of this offering, assuming no exercise of the underwriters' option to purchase additional common shares in the offering) with affiliates or third parties, without existing shareholders having statutory subscription rights in relation to this share placement;

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limit the size of our board of directors to members; and

limit the size of our board of directors to nine members; and require two-thirds of the votes represented at a general meeting of shareholders for amending or repealing the above-mentioned registration and voting restrictions, the provision setting a maximum board size, and the provision for indemnification of the members of our board of directors and our executive committee as set forth in our articles of association, and for dismissing the chairman or any member of our board of directors or any member of our compensation committee before the end of his or her term of office.

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Upon the completion of this offering, common shares will be outstanding (or common shares if the underwriters exercise their option to purchase additional common shares from us in full), based on the number of shares outstanding as of June 30, 2026, assuming the conversion of all outstanding Preferred shares into common shares. Share Conversion and the Series B Warrant Settlement.

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The registration of the

the share capital increases in the Commercial Register of the Canton of Basel-Stadt, Switzerland, may be blocked and the shareholders' resolutions regarding the ordinary share capital increases and the creation of a capital range may be challenged.

This offering is subject to, among other things, approval by our shareholders of resolutions regarding the ordinary share capital increase and the creation of a capital range necessary to source the common shares to be sold in this offering, which was obtained on , 2026. The execution of the ordinary share capital increase and the share capital increase within the capital range (if applicable) by our board of directors and the related filings will be made prior to the completion of this offering and, with regard to the common shares to be issued upon any exercise of the underwriters' option to purchase additional common shares (if any), upon exercise of such option. The issuance of new common shares will become effective upon registration in the Commercial Register. of the Canton of Basel-Stadt, Switzerland. As with all share capital increases in Switzerland, the shareholders' resolutions regarding such share capital increase may be challenged in court within two months after such shareholders' meeting and/or the registration of the capital increases in the Commercial Register of the Canton of Basel-Stadt, Switzerland, may be blocked temporarily by a preliminary injunction or permanently by order of a competent court. Either action would prevent or delay the completion of this offering.

Our issuance of additional shares in

Our issuance of additional shares in connection with financings, acquisitions, investments, our equity incentive plans or otherwise will dilute all other shareholders.

We expect to issue additional shares in the future that will result in dilution to all other shareholders. We expect to grant equity awards to employees, directors and consultants under our equity incentive plans. We may also raise capital through equity financings in the future. As part of our business strategy, we may acquire or make investments in complementary companies, products or technologies and issue equity securities to pay for any such acquisition or investment. Any such issuances of additional shares may cause shareholders to experience significant dilution of their ownership interests and the per share value of our common shares to decline.

Our amended and restated articles of

Our amended and restated articles of association provide for conditional share capital for financing, acquisitions and other purposes, excluding the advance subscription rights and pre-emptive subscription rights of our existing shareholders, which may result in a dilution of our existing shareholders.

Our amended and restated articles of association provide for conditional share capital for financing, acquisitions and other purposes in an amount equal to approximately % of our outstanding share capital registered in the Commercial Register immediately after completion of this offering. Common shares may be issued out of this conditional capital through the exercise or mandatory exercise of conversion, exchange, option, subscription or other rights to acquire shares or through obligations to acquire common shares, which are granted to or imposed on shareholders or third parties alone or in connection with bonds, notes, options, warrants or other financial instruments issued by us or any of our group companies. Our amended and restated articles of association provide for an exclusion of the advance subscription rights of our shareholders in connection with the issuance of any such financial instruments and the exclusion of the pre-emptive subscription rights of our shareholders in connection with the issuance of common shares upon exercise of any such financial instruments. See "Description of Share Capital and Articles of Association—Certain Important Provisions of our Articles of Association, Organizational Regulations and Swiss Law—Our Conditional Share Capital" included elsewhere in this prospectus. Such shares may be issued at a price below the respective stock exchange price, and such financial instruments may be issued below their intrinsic value. As a result, our existing shareholders may experience significant dilution of their ownership interests if and when such financial instruments are issued and subsequently converted into or exercised for our common shares. This may adversely affect the per share value of our common shares.

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We have never declared or paid dividends, whether in cash, in kind or otherwise, since our incorporation.

We have never declared or paid dividends, whether in cash, in kind or otherwise, since our incorporation. Even if future operations lead to significant levels of distributable profits, we currently intend to retain all available funds and any future earnings to support operations and to finance the growth and development of our business. We do not intend to declare or pay any dividends in the foreseeable future, and we may never be able to do so. Any proposal of our board of directors to the general meeting of shareholders to pay future dividends will be at the discretion of our board of directors after taking into account various factors, including our business prospects, cash requirements, financial performance and new product development, and subject to approval by the general meeting of shareholders. In addition, payment of future dividends is subject to certain limitations pursuant to Swiss law. See "Description of Share Capital and Articles of Association—Dividends and Other Distributions" included elsewhere in this prospectus. Also, we are a holding company with no material direct operations. As a result, we would be largely dependent on dividends or other distributions from our subsidiaries in order to pay a dividend. Our subsidiaries are subject to legal requirements of their respective jurisdictions of incorporation that may restrict their paying dividends or making other distributions to us. As a result, investors cannot rely on dividend income from our common shares and any investment return on our common shares will depend upon increases in the value for our common shares, which is not certain.

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Swiss law reserves for approval by

Swiss law reserves for approval by shareholders certain corporate actions over which a board of directors would have authority in some other jurisdictions. For example, the payment of dividends and the cancellation of treasury shares must be approved by shareholders (other than a cancellation of treasury shares within a capital range). Swiss law also requires that our shareholders themselves resolve to, or authorize our board of directors to, increase our share capital or cancel treasury shares. While our shareholders may resolve to create a capital range and thereby authorize our board of directors to issue new shares or cancel treasury shares without additional shareholder approval, Swiss law limits this authorization to 50% of the share capital registered in the Commercial Register of the Canton of Basel-Stadt, Switzerland, at the time of the authorization. The authorization, furthermore, has a limited duration of up to five years and must be renewed by the shareholders from time to time thereafter (or in the event of an earlier lapse of the capital range in accordance with Swiss law) in order to be available for raising capital. Additionally, subject to specified exceptions, including exceptions explicitly described in our articles of association, Swiss law grants subscription rights to existing shareholders to subscribe for new issuances of shares, which may be limited or withdrawn under certain conditions. Swiss law also does not provide as much flexibility in the various rights and regulations that can attach to different classes of shares as do the laws of some other jurisdictions. These Swiss law requirements relating to our capital management may limit our flexibility, and situations may arise where greater flexibility would have provided benefits to our shareholders. See "Description of Share Capital and Articles of Association" included elsewhere in this prospectus.

Swiss law also does not provide as much flexibility in the various rights and regulations that can attach to different classes of shares as do the laws of some other jurisdictions. These Swiss law requirements relating to our capital management may limit our flexibility, and situations may arise where greater flexibility would have provided benefits to our shareholders. See "Description of Share Capital and Articles of Association" included elsewhere in this prospectus.

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Under Swiss corporate law, shareholders may receive

Under Swiss corporate law, shareholders may receive certain subscription rights to subscribe on a pro-rata basis for issuances of equity securities or other securities that are convertible into equity securities. Due to the laws and regulations in certain jurisdictions, however, shareholders who are not residents of the United States may not be able to exercise such rights unless we take action to register or otherwise qualify the rights offering, including, for example, by complying with prospectus requirements under the laws of that jurisdiction. There can be no assurance that we will take any action to register or otherwise qualify an offering of subscription rights or shares under the laws of any jurisdiction other than the United States where the offering of such rights is restricted. If shareholders in such jurisdictions were unable to exercise their subscription rights, their ownership interest in us will be diluted.

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Capitalization 2 changes

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common shares issuable under our 2026 Employee Share Purchase Plan, or the ESPP; and ∎ 50,700 common shares we hold in treasury.

common shares issuable under our 2026 Employee Share Purchase Plan, or the ESPP; and ∎ 50,700 common shares we hold in treasury and an additional number of common shares to be issued in connection with the capital increases as further described in the section titled "Description of Share Capital and Articles of Association" such that the total number of common shares to be held in treasury upon completion of this offering corresponds to 10% of the share capital registered in the Commercial Register.

Dilution 4 changes

If you invest in our common shares during this offering, your ownership interest will be immediately diluted to the extent of the difference between the initial public offering price per share of our common shares and the pro forma as adjusted net tangible book value per share of our common shares immediately after the closing completion of this offering.

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Similarly, each increase or decrease (as applicable) of 1.0 million shares in the number of common shares offered by us would increase or decrease, as applicable our pro forma as adjusted net tangible book value per share after the closing completion of this offering by $ per share, in each case, and increase or decrease (as applicable) the dilution to investors participating in this offering by $ per share, assuming that the assumed initial public offering price remains the same, and after deducting estimated underwriting discounts and commissions and estimated offering expenses payable by us.

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50,700 common shares we hold in treasury.

50,700 common shares we hold in and an additional number of common shares to be issued in connection with the capital increases as further described in the section titled "Description of Share Capital and Articles of Association" such that the total number of common shares to be held in treasury upon completion of this offering corresponds to 10% of the share capital registered in the Commercial Register.

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Business 95 changes

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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.

The graph below shows the anticipated timing of certain key clinical development milestones for WIN378 and WIN027, including planned study initiations expected to be funded with the net proceeds from this offering and anticipated clinical data readouts. The timing of these milestones is inherently uncertain and subject to numerous risks, delays and changes. See "Risk Factors" for additional information regarding risks that could delay the development of WIN378 and WIN027 or our achievement of these anticipated milestones.

Qyuns initiated its Phase 2 program including studies in atopic dermatitis and CRSwNP in September 2026 in the PRC and plans to begin a Phase 2 study in asthma by the end of the year. Topline results from these studies are expected over the course of 2027 and 2028.

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We have not generated any product

Our goal is to develop, obtain regulatory approval, and

We have not generated any product revenue to date and have funded our operations principally through private placements of equity. As of June 30, 2026, we had cash, cash equivalents and marketable securities of $207.3 million.

Our goal is to develop, obtain 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. We estimate that these diseases collectively affect approximately 100 million people in the United States, EU5, and Japan and more than 8 million are eligible for biologics treatment. Based on our internal estimates, we believe this represents an estimated $60 billion peak market opportunity for biologic therapies. 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.

disease including TSLP and IL-13.

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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 low rate of injection site reactions, with full pharmacokinetic and immunogenicity data expected in the first half of 2027. We plan to initiate a global Phase 2b in COPD, 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 global Phase 2 study in atopic dermatitis in the first half of 2027 with topline results expected in the second half of 2028. Qyuns initiated their Phase 2 studies in atopic dermatitis and CRSwNP in September 2026 in the PRC and plans to begin a Phase 2 study in asthma by the end of 2026. Topline results from these studies are expected over the course of 2027 and 2028.

Topline results are expected in the first half of 2029. We also plan to initiate a global Phase 2 study in atopic dermatitis in the first half of 2027 with topline results expected in the second half of 2028. Qyuns initiated their Phase 2 studies in atopic dermatitis and CRSwNP in September 2026 in the PRC and plans to begin a Phase 2 study in asthma by the end of 2026. Topline results from these studies are expected over the course of 2027 and 2028.

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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.

Windward Bio holds global rights to WIN378 excluding Greater China and certain Asian markets ** Exclusivity based on pending applications and anticipated patent extensions *** Lead optimization stage with potential in respiratory and dermatology; see "—Additional bispecific programs" on page 114 for more information COPD = chronic obstructive pulmonary disease, IP=intellectual property, mAb=monoclonal antibody In addition to the studies we are conducting for WIN027, our partner and licensor, Qyuns, has initiated its Phase 2 program including studies in atopic dermatitis and CRSwNP in September 2026 in the PRC and plans to begin a Phase 2 study in asthma by the end of the year.

WIN378 is an ultra-long-acting

Windward Bio holds global rights to WIN378 excluding Greater China and certain Asian markets ** Exclusivity based on pending applications and anticipated patent extensions *** These studies are conducted and funded by Qyuns Therapeutics; see "—WIN027" on page 119 for more information **** Lead optimization stage with potential in respiratory and dermatology; see "—Additional bispecific programs" on page 119 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 nonclinical 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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WIN027 is an ultra-long-acting, potentially

global rights (excluding Greater China) for WIN027 from Qyuns (also known as QX027N) and retain all decision-making rights in our territory. Although we do not conduct or fund, and have no direct economic rights with respect to, Qyuns-sponsored programs in the PRC, the data generated from these clinical trials directly informs the design and conduct of our WIN027 clinical development programs and potential regulatory filings outside Greater China, and more importantly, the potential value of WIN027 outside of Greater China. Results from a trial of WIN027 anywhere in the world will impact and be relevant to the value and potential of WIN027 on a global basis. Under our license and collaboration agreement with Qyuns, Qyuns is required to provide us with copies of and access to data, results and supporting documentation generated from its development activities. We have the right to use and reference such information in connection with our development of WIN027 and our pursuit and maintenance of regulatory approvals outside Greater China, where we hold exclusive development and commercialization rights. Furthermore, pursuant to our license and collaboration agreement with Qyuns, we and Qyuns have established a joint steering committee that oversees and coordinates the development, manufacture and commercialization of compounds and product candidates, including cross-territory clinical trials.

Additional bispecific programs are in the lead

WIN378 is initially being developed for the treatment of

By contrast, biologic use is more established in

Based on published and public statements

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 the safety and efficacy data needed to support approval in future pivotal trials, has the potential to be the first 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

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 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.

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

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 have not observed any treatment-related serious adverse events, with full pharmacokinetic and immunogenicity data expected in the first half of 2027. We plan to initiate multiple Phase 2 studies. We initiated study start-up activities in September 2026 for a global, dose-ranging finding Phase 2 study in COPD, powered on the registrational endpoint of exacerbation rate ratio, which is planned to begin patient recruitment 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 function, hierarchical type 1 error control, independent data and safety monitoring, and a population aligned with the intended indication. We also initiated study start-up activities in September 2026 for an additional Phase 2 study in atopic dermatitis which is planned to begin patient recruitment in the first half of 2027 with topline results expected in the second half of 2028. Qyuns initiated their Phase 2 studies in atopic dermatitis and CRSwNP in September 2026 in the PRC and plans to begin a Phase 2 study in asthma by the end of the year. Topline results from these studies are expected over the course of 2027 and 2028.

We plan to initiate multiple Phase 2 studies. We initiated study start-up activities in September 2026 for a global, dose-ranging finding Phase 2 study in COPD, powered on the registrational endpoint of exacerbation rate ratio, which is planned to begin patient recruitment 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 function, hierarchical type 1 error control, independent data and safety monitoring, and a population aligned with the intended indication. We also initiated study start-up activities in September 2026 for an additional Phase 2 study in atopic dermatitis which is planned to begin patient recruitment in the first half of 2027 with topline results expected in the second half of 2028. Qyuns initiated their Phase 2 studies in atopic dermatitis and CRSwNP in September 2026 in the PRC and plans to begin a Phase 2 study in asthma by the end of the year. Topline results from these studies are expected over the course of 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 nonclinical target format has been identified and selected, with potential across skin and respiratory indications, including atopic dermatitis, asthma, 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 is currently being engineered for half-life extension prior to characterization in nonhuman primate studies.

being developed for the treatment of respiratory diseases with a focus on asthma and COPD. WIN027 is being developed for the treatment of respiratory disease and atopic dermatitis. Although these indications encompass large and growing markets, we estimate that the biologics treatment rate among eligible patients remains low—approximately 20% in severe asthma, approximately 1% in moderate-to-severe COPD, and approximately 15% in moderate-to-severe atopic dermatitis.

By contrast, biologic

use is more established in certain other immune-mediated diseases. We estimate that biologic use among eligible patients averages approximately 40% across Crohn's Disease, Ulcerative Colitis, Rheumatoid Arthritis and Psoriatic Arthritis, driven in part by the length of time biologics have been on the market, the number of available treatment options, and the ability of biologics to address the unmet needs in these diseases. We believe there is potential for the biologic treatment rate to increase in asthma, COPD, and atopic dermatitis over time as more treatments become available, efficacy and dosing convenience standards improve, and treatments are indicated for more sub-populations of patients.

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approximately 440,000 people worldwide died from asthma in 2023, more than 1,000 deaths every day. The prevalence of asthma in the United States is approximately 28 million.

Menzies-Gow A et al. N Engl J Med 2021; Bleecker ER et al. Lancet 2016; FitzGerald JM et al. Lancet 2016; Pavord ID et al. Lancet 2012; Ortega HG et al. N Engl J Med 2014; Busse W et al. J Allergy Clin Immunol 2001; Sol r M et al. Eur Respir J 2001; 2 Bhatt SP et al. N Engl J Med 2023; Bhatt SP et al. N Engl J Med 2024; Singh D et al. Lancet Respir Med 2025; Pavord ID et al. N Engl J Med 2017; Sciurba FC et al. N Engl J Med 2025; Criner GJ et al. N Engl J Med 2019; Sciurba et al. N Engl J Med 2026; 3 Silverberg JI et al. N Engl J Med 2023; Blauvelt A et al. Br J Dermatol 2023; Simpson EL et al. N Engl J Med 2016; Silverberg JI et al. Lancet 2024 benra=benralizumab, dupi=dupilumab, EOS=baseline eosinophil count (cells/ L), mepo=mepolizumab, MOA=mechanism of action, nemo=nemolizumabo, teze=tezepelumab, tozo=tozorakimab Severe Asthma Disease Overview Asthma is a common, chronic and heterogeneous respiratory disease characterized by inflammation of the airways and respiratory symptoms that vary over time and in intensity. It can result in significant morbidity and mortality if not adequately controlled. The World Health Organization estimated that asthma impacted over 360 million people worldwide. Mortality is substantial and, importantly, largely preventable: approximately 440,000 people worldwide died from asthma in 2023, more than 1,000 deaths every day. The prevalence of asthma in the United States is approximately 28 million.

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The most important biological distinction is between type-2 and non-type-2 asthma, which is defined by the kind of inflammation present in the airways. Type-2 asthma is driven by the activation of a type-2 immune response and its signature cytokines, principally IL-4, IL-5, and IL-13. These cytokines increase production of immunoglobulin E, or IgE, the antibody central to allergic reactions; recruit and activate eosinophils, a type of white blood cell that drives airway inflammation;

The most important biological distinction is between type-2 and non-type-2 asthma, which is defined by the kind of inflammation present in the airways. Type-2 asthma is driven by the activation of a type-2 immune response and its signature cytokines, principally IL-4, IL-5, and IL-13. These cytokines increase production of immunoglobulin E, or IgE, the antibody central to allergic reactions; recruit and activate eosinophils, a type of white blood cell that drives airway inflammation; and raise the level of nitric oxide in exhaled breath. Type-2 disease itself takes more than one form. It includes allergic asthma, which is typically allergen-driven and often begins in childhood, and later-onset eosinophilic asthma, which can arise in adulthood without a clear allergic trigger. A number of biologics target this subgroup including the anti-IL-5 class (Nucala , mepolizumab; Fasenra , benralizumab; and Exdensur , depemokimab-ulaa), the anti-IL-4/IL-13 class (Dupixent , dupilumab), the anti-IgE class (Xolair , omalizumab) as well as anti-TSLP (Tezspire , tezepelumab).

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Patients with non-type-2 asthma tend

Patients with non-type-2 asthma tend to respond poorly to inhaled corticosteroids, and they have historically been poor candidates for the available biologics, which act on the type-2 pathway and offer little where type-2 biomarkers are low. The anti-TSLP antibody, Tezspire , tezepelumab, is the only biologic approved for all patients with severe, uncontrolled asthma, including patients with both high-T2 and low-T2 status. Severe non-type-2 asthma therefore remains among the most significant areas of unmet need in respiratory medicine, and it is a central focus of the rationale for our program in addition to addressing the broader severe asthma, where Tezspire , tezepelumab, has demonstrated significant clinical benefit.

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Within this severe segment, our market research indicates several key unmet needs that we believe can be addressed by our programs.

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The following figure summarizes the number of

The following figure summarizes the number of dosing periods per year for approved respiratory biologics alongside real-world persistency.

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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.

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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By contrast, biologic use is more established in

We believe that WIN378 is

By contrast, biologic use is more established in certain other immune-mediated diseases. We believe biologic use among eligible patients averages approximately 40% across Crohn's Disease, Ulcerative Colitis, Rheumatoid Arthritis, and Psoriatic Arthritis. We believe there is potential for biologic penetration to increase in severe asthma over time as more treatments become available, efficacy and dosing convenience standards improve, and treatments are indicated for more sub-populations of patients. Despite relatively modest current penetration of biologic therapies in severe asthma, the biologic therapeutics market is already substantial and is expected to grow. In 2025, global sales of biologics for severe asthma were approximately $14 billion, and we project the market to reach $30 billion at peak in combination with COPD biologic treatment.

We believe that WIN378 is well-positioned to drive this market growth and can achieve a meaningful share of patients treated with biologics.

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COPD is a heterogeneous lung condition

COPD is a heterogeneous lung condition characterized by chronic respiratory symptoms, including shortness of breath, cough, sputum production and disease exacerbations arising from airway abnormalities such as bronchitis or bronchiolitis, and emphysema, which is characterized by damage to the alveoli, the air sacs of the lung where oxygen enters the blood. The result of these symptoms and COPD more generally is a persistent, often progressive airflow obstruction that can produce significant morbidity and mortality, including right-sided heart failure, if not adequately controlled. A systematic review of large population studies estimated that COPD affects approximately 390 million people worldwide, with prevalence continuing to rise. COPD is the third leading cause of death globally, responsible for approximately 3.4 million deaths in 2023.

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IL-4/IL-13 receptor component, became the first approved biologic for COPD in September 2024, based on the Phase 3 BOREAS and NOTUS trials, which demonstrated 30% and 34% reductions, respectively, in annualized moderate-or-severe exacerbation rates versus placebo in patients with BEC ≥ 300 cells/ L on background triple therapy. It is administered 26 times per year. Nucala (mepolizumab), an anti-IL-5 antibody, was subsequently approved in patients with an eosinophilic phenotype based on the Phase 3 MATINEE and METREX trials, which showed statistically significant reductions in annualized exacerbation rates of 21% and 18%, respectively, in patients with BEC ≥ 300 cells/ L (MATINEE) and across a broader eosinophilic range (METREX); mepolizumab's label extends down to BEC ≥ 150 cells/ L. It is administered 12 times per year.

mepolizumab's label extends down to BEC ≥ 150 cells/ L. It is administered 12 times per year.

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We believe WIN027 may

We believe WIN378 is well-positioned to address these unmet needs. Because TSLP acts upstream of eosinophil-driven and non-eosinophil-driven inflammatory pathways, we believe an anti-TSLP therapy such as WIN378 has the potential to address a broader COPD population than currently approved biologics, subject to successful clinical validation in our SIRIUS Phase 2 study and any subsequent pivotal trials. WIN378 has been specifically engineered to be ultra-long-acting, providing dosing twice-yearly, which, if approved, would be a significant improvement upon existing standards of care.

We believe WIN027 may also be able to address these unmet needs. It is a single treatment engineered to potently shut down two central drivers of type-2 inflammation at once—TSLP and IL-13. Because TSLP sits upstream and IL-13 downstream of the same disease pathway, blocking both with one antibody is designed to produce broader, more complete pathway suppression than any single-target biologic. This may be achieved with single-targeted biologics and may be particularly effective in patients with severe disease and lung complications such as mucous plugs.

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The pathophysiology reflects a self-reinforcing interplay

Disease Overview, Unmet Need, and Market Opportunity

Atopic dermatitis, also known as atopic eczema, is a chronic, relapsing inflammatory skin disease driven substantially by type-2 inflammation. It is characterized by recurrent eczematous lesions, dry skin, and intense, persistent itch (pruritus), and it follows a fluctuating course of flares and partial remissions rather than a steady state. It is the most common chronic inflammatory skin disease and, among all skin conditions, carries the largest burden of disability as measured by disability-adjusted life-years.

The pathophysiology reflects a self-reinforcing interplay between epidermal barrier dysfunction and type-2 immune activation, with genetic and environmental factors contributing to both. Barrier impairment is a central feature. The resulting permeability allows increased transepidermal water loss and greater penetration of allergens, irritants, and microbes, which in turn amplifies the immune response. Barrier disruption and external triggers stimulate keratinocytes to release the epithelial alarmins, including TSLP. These alarmins activate dendritic cells and group 2 innate lymphoid cells and polarize naive T cells toward a Th 2 phenotype, positioning TSLP in particular as an upstream initiator that sits proximal to the downstream effector cascade. The Th2 and ILC2 compartments produce the central effector cytokine IL-13, which signals through JAK-STAT pathways to drive IgE eosinophil recruitment, and further suppression of barrier proteins and antimicrobial peptides. IL-13 is the dominant cytokine in lesional skin and is a principal driver of the tissue remodeling and barrier defects that characterize chronic disease.

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TSLP is a signaling protein (a cytokine) released by the

epithelial cells that line the body's barrier surfaces, most importantly, the airways of the lung, the lining of the gastrointestinal tract, and the skin. These surfaces are the body's first point of contact with the outside environment.

TSLP belongs to a small family of cytokines, together with IL-25 and IL-33, that are known as "alarmins" because they act as early warning signals.

TSLP is a signaling protein (a cytokine) released by the epithelial cells that line the body's barrier surfaces, most importantly, the airways of the lung, the lining of the gastrointestinal tract, and the skin. These surfaces are the body's first point of contact with the outside environment. TSLP belongs to a small family of cytokines, together with IL-25 and IL-33, that are known as "alarmins" because they act as early warning signals. Epithelial cells produce TSLP in response to a wide variety of environmental triggers, including allergens, airborne pollutants such as cigarette smoke, viruses, bacteria, and direct physical injury to the tissue. Due to this profile, TSLP is among the first molecules the body releases when a barrier surface is disturbed. Other immune cells that respond to allergens, pollutants and mechanical damage and release TSLP are cells such as dendritic cells, basophils, and mast cells that are responsible for the body's immune defense system.

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Because TSLP sits at the very top of the inflammatory cascade, its relevance is not confined to any single disease, nor to patients with a strong type-2 signature. The epithelial-driven inflammatory diseases in which TSLP is implicated, including asthma and COPD, are increasingly understood not as uniform conditions but as collections of overlapping subtypes, or phenotypes, driven by different combinations of underlying biology. Existing targeted therapies, which typically block a single downstream cytokine, tend to help only the subset of patients whose disease is dominated by that one pathway. A therapy acting further upstream has the potential to reach a broader range of patients.

Existing targeted therapies, which typically block a single downstream cytokine, tend to help only the subset of patients whose disease is dominated by that one pathway. A therapy acting further upstream has the potential to reach a broader range of patients.

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This is of particular consequence in the small

This is of particular consequence in the small airways and in COPD, where remodeling, small-airway obstruction and mucus plugging are central drivers of disease and are among the least well addressed by existing therapies. An upstream mechanism with the potential to modulate not only the inflammatory response but also the structural changes that follow is a meaningful part of the rationale for an anti-TSLP approach across epithelial-driven respiratory diseases, and a further point of differentiation for our program.

Anti-TSLP 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.

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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Both TSLP and IL-13 are elevated in the airways of patients with asthma, and the level of each correlates with disease severity and with impaired lung function. These observations suggest that both cytokines are active participants in human disease rather than incidental markers, and that they operate at different levels of the same pathway. TSLP acts upstream to initiate and shape the type-2 response and IL-13 acts downstream to execute many of its negative consequences.

Adding IL-13 to TSLP

Those effector functions are extensive. In the airway, IL-13 recruits eosinophils into the tissue, promotes the class switching that generates IgE (the antibody central to allergic responses), stimulates the goblet cells that produce airway mucus, and contributes to the structural changes of airway remodeling, including the smooth-muscle and fibrotic changes described above. Both TSLP and IL-13 are elevated in the airways of patients with asthma, and the level of each correlates with disease severity and with impaired lung function. These observations suggest that both cytokines are active participants in human disease rather than incidental markers, and that they operate at different levels of the same pathway.

TSLP acts upstream to initiate and shape the type-2 response and IL-13 acts downstream to execute many of its negative consequences.

Adding IL-13 to TSLP blockade is also designed to reach the more refractory, structurally driven features of advanced airways disease. TSLP blockade acts high in the inflammatory cascade, dampening the initiating alarmin signal. Conversely, much of the fixed, structural pathology of severe and advanced respiratory disease is driven by IL-13 acting directly on airway structural cells, largely downstream of, and in part independently of, upstream alarmin tone. IL-13 is a principal driver of goblet-cell metaplasia and MUC5AC-dominant mucus hypersecretion (and thus of the mucus plugging increasingly recognized as a determinant of airflow obstruction and lost lung function), of airway smooth-muscle contractility and hyperresponsiveness, and, through its actions on fibroblasts and the epithelium, of the peribronchial fibrosis and remodeling that narrow the small airways.

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Additionally, like TSLP, IL-13 contributes to itch, both by amplifying the surrounding inflammation and through effects on sensory nerve signaling. Because IL-13 acts on the skin barrier, the immune response and itch at the effector level, while TSLP acts upstream to initiate and sustain the same processes, the two cytokines represent complementary points of intervention in atopic dermatitis, mirroring their relationship in the airway and reinforcing the rationale for targeting both with WIN027.

to quiet the upstream instigator while also neutralizing its most consequential downstream effector. We believe these complementary and non-redundant mechanisms provide the rationale for targeting both cytokines with a single agent.

TSLP's role at barrier surfaces extends to the skin, where it is produced by keratinocytes and is one of the most consistently elevated cytokines in the lesional skin of patients with atopic dermatitis. It contributes to the disease through several connected routes. A damaged skin barrier prompts keratinocytes to release TSLP, which drives type-2 inflammation that in turn further degrades the barrier, creating a self-perpetuating loop of barrier dysfunction and inflammation. TSLP also acts directly on the sensory nerves of the skin: a subset of itch-transmitting neurons expresses the TSLP receptor, so TSLP can evoke itch not only indirectly through inflammation but also by signaling to the nervous system itself. Since itch drives scratching, which causes further barrier damage and TSLP release, this ties back into the same loop. TSLP therefore sits at the intersection of three core features of atopic dermatitis: barrier dysfunction, type-2 inflammation, and itch. Inhibiting it offers a rationale for addressing the disease more fundamentally than approaches directed at a single downstream effector, and positions TSLP as a shared upstream target across the epithelial surfaces of both skin and airway.

IL-13 is among the principal effector cytokines in atopic

IL-13 is among the principal effector cytokines in atopic dermatitis, and it is now regarded as a dominant driver of the disease. IL-13 is one of the most abundant type-2 cytokines in lesional atopic dermatitis skin, and its effects map onto the core features of the condition. It weakens the skin barrier by suppressing the production of the structural proteins and lipids that keep the barrier intact, such as filaggrin, which both worsens water loss and lets in more allergens and microbes. It reshapes the skin's response to those microbes, contributing to the susceptibility to infection and the disturbed skin microbiome characteristic of the disease. It drives the tissue changes of chronic disease, including the thickening and remodeling seen in long-standing lesions. Additionally, like TSLP, IL-13 contributes to itch, both by amplifying the surrounding inflammation and through effects on sensory nerve signaling. Because IL-13 acts on the skin barrier, the immune response and itch at the effector level, while TSLP acts upstream to initiate and sustain the same processes, the two cytokines represent complementary points of intervention in atopic dermatitis, mirroring their relationship in the airway and reinforcing the rationale for targeting both with WIN027.

This division of labor is the core of the rationale for WIN027. Blocking TSLP alone reduces the initiating signal, but type-2 inflammation, once established, can be sustained by effector cytokines already in circulation, and IL-13 can be produced by cell types that do not depend on TSLP. Blocking IL-13 alone addresses a major effector arm but leaves the upstream alarm signal intact and does not constrain the other cytokines that TSLP drives, such as IL-4, IL-5 and IL-9. Inhibiting both targets simultaneously is designed to close the pathway at two complementary points: to quiet the upstream instigator while also neutralizing its most consequential downstream effector. We believe these complementary and non-redundant mechanisms provide the rationale for targeting both cytokines with a single agent.

The intended consequence is a broader and deeper suppression of type-2 inflammation than either mechanism can achieve alone.

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and 15 more changes in the filing

Management 52 changes

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Prior to the completion of the offering, We intend to adopt have adopted a Code of Business Conduct and Ethics applicable to our and our subsidiaries' employees, independent contractors, executive officers and directors, including our principal executive officer, principal financial officer, principal accounting officer or controller, or persons performing similar functions. Immediately prior to the completion of this offering, our Code of Business Conduct and Ethics will be available on our website at www.windwardbio.com. In addition, we intend to post on our website all disclosures that are required by law or the listing standards of Nasdaq concerning any amendments to, or waivers from, any provision of our Code of Business Conduct and Ethics. Information contained on, or accessible through, our website is not a part of this prospectus, and the inclusion of our website address in this prospectus is only as an inactive textual reference.

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For the year ended December 31, 2025, the aggregate compensation for the members of our board of directors and our executive officers for services in all capacities was $11.3 million.

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During the year ended December 31, 2025,

During the year ended December 31, 2025, share-based payments granted to the members of our board of directors and our executive officers accounted for $14.3 million, of which $7.2 million were recognized as expense in the year ended December 31, 2025. Of those share-based payments, 8,605,800 founder shares were subscribed to by members of our board of directors and our executive officers which includes a total of 4,736,843 of founder shares with certain service vesting conditions and performance vesting conditions considered within the scope of IFRS 2, at a fair value of $3.02. See Note 10 to our audited consolidated financial statements included elsewhere in this prospectus for further details regarding the share-based payments. Share-based payments that are discussed in this paragraph but are outside of the scope of IFRS 2 were not included in Note 10 to our audited consolidated financial statements.

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We will also reimburse our directors for their

We will also reimburse our directors for their reasonable out-of-pocket expenses in connection with attending board and committee meetings.

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Share Reserve . Initially, subject to certain adjustments, the maximum number of our common shares that may be issued pursuant to awards under our 2026 Plan after it becomes effective will equal the sum of (i) common shares, plus (ii) the number of common shares subject to outstanding awards under our 2025 Plan and certain founder share repurchase agreements and restricted share purchase agreements that become available for issuance under our 2026 Plan from time to time in accordance with its terms. In addition, subject to certain adjustments, the number of common shares reserved for issuance under our 2026 Plan 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, in an amount equal to (1) % of the total number of our common shares and any unexercised pre-funded warrants outstanding on December 31 of the immediately preceding year, or (2) a lesser number of common shares determined by our board of directors no later than December 31 of the immediately preceding year. The maximum number of common shares that may be issued on the exercise of ISOs under our 2026 Plan is common shares.

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Under our 2026 Plan, our board of directors also

Plan Administration .

Plan Administration . Our board of directors, or a duly authorized committee of our board of directors, administers our 2026 Plan. Our board of directors may delegate to one or more persons or bodies the authority to (i) designate recipients (other than officers) to receive specified share awards; and (ii) determine the number of shares subject to such share awards. Under our 2026 Plan, our board of directors has the authority to determine share award recipients, the types of share awards to be granted, grant dates, the number of shares subject to each share award, the fair market value of our common shares, and the provisions of each share award, including the period of exercisability and the vesting schedule applicable to a share award.

Under our 2026 Plan, our board of directors also generally has the authority to effect, with the consent of any materially adversely affected participant, (i) the reduction of the exercise, purchase, or strike price of any outstanding option or share appreciation right; (ii) the cancellation of any outstanding option or share appreciation right and the grant in substitution therefor of other awards, cash, or other consideration; or (iii) any other action that is treated as a repricing under IFRS.

Options . ISOs and NSOs are granted under option

Options . ISOs and NSOs are granted under option agreements adopted by the administrator. The administrator determines the exercise price for options, within the terms and conditions of our 2026 Plan, except the exercise price of an option generally will not be less than 100% of the fair market value of our common shares on the date of grant. Options granted under our 2026 Plan will vest at the rate specified in the option agreement as determined by the administrator.

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Unless the administrator provides otherwise, options or share appreciation rights generally are not transferable except by will or the laws of descent and distribution.

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Restricted Share Unit Awards . Restricted share unit awards are granted under restricted share unit award agreements adopted by the administrator. Restricted share unit awards may be granted in consideration for any form of legal consideration that may be acceptable to our board of directors and permissible under applicable law. A restricted share unit award may be settled by cash, delivery of shares, a combination of cash and shares as deemed appropriate by the administrator, or in any other form of consideration set forth in the restricted share unit award agreement. Additionally, dividend equivalents may be credited in respect of shares covered by a restricted share unit award. Except as otherwise provided in the applicable award agreement, or other written agreement between us and the recipient, restricted share unit awards that have not vested will be forfeited once the participant's continuous service ends for any reason.

Restricted Share Awards . Restricted share awards are

Restricted Share Awards . Restricted share awards are granted under restricted share award agreements adopted by the administrator. A restricted share award may be awarded in consideration for cash, check, bank draft or money order, past or future services to us, or any other form of legal consideration that may be acceptable to our board of directors and permissible under applicable law. The administrator determines the terms and conditions of restricted share awards, including vesting and forfeiture terms. If a participant's service relationship with us ends for any reason, we may receive any or all of the common shares held by the participant that have not vested as of the date the participant terminates service with us through a forfeiture condition or a repurchase right.

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Changes to Capital Structure . In the event there is a

Corporate Transactions . In the event of a

Other Share Awards .

Other Share Awards . The administrator may grant other awards based in whole or in part by reference to our common shares. The administrator will set the number of shares under the award (or cash equivalent) and all other terms and conditions of such awards.

Changes to Capital Structure . In the event there is a specified type of change in our capital structure, such as a share split, reverse share split, or recapitalization, appropriate adjustments will be made to (i) the class and maximum number of shares reserved for issuance under our 2026 Plan, (ii) the class and maximum number of shares by which the share reserve may increase automatically each year, (iii) the class and maximum number of shares that may be issued on the exercise of ISOs, and (iv) the class and number of shares and exercise price, strike price, or purchase price, if applicable, of all outstanding share awards.

Corporate Transactions . In the event of a corporate transaction (as defined in the 2026 Plan), the administrator may take one or more of the following actions with respect to awards:

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Share Reserve . Subject to certain adjustments, 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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Acceptable consideration for the purchase of common shares issued upon the exercise of an option includes (i) payment of the exercise price in cash;

In February 2025, our board of directors

In February 2025, our board of directors adopted the 2025 Plan (as amended and restated in June 2025). No further awards will be granted under our 2025 Plan on or after the effectiveness of our 2026 Plan; however, awards outstanding under our 2025 Plan will continue to be governed by their existing terms.

As of September 30, 2026, options to purchase 2,109,516 of our common shares were outstanding under our 2025 Plan, 769,616 restricted share units were granted under our 2025 plan, and 1,860,609 of our common shares remained available for future awards under our 2025 Plan.

Awards . Our 2025 Plan

Awards . Our 2025 Plan provides for the grant of options and restricted share unit awards to our, or any of our affiliate's, employees, directors and consultants. Each option gives such recipient the right to purchase one common share upon exercise, and each restricted share unit gives such recipient the right to receive one common share upon vesting and settlement.

Plan Administration . Our board of directors, a

Plan Administration . Our board of directors, a duly authorized committee of our board of directors, or, for grants other than to our executive committee and directors, our Chief Executive Officer, administers our 2025 Plan. The administrator has the authority to determine award recipients, whether recipients receive restricted share units or options, the number of shares granted for each award, and the terms of each award, including the grant date, the exercise price, the period of exercisability and the vesting schedule applicable to an award.

Options . Options are granted under option agreements adopted by the administrator. The exercise price for options will generally be the nominal value of the underlying common shares, unless otherwise determined by the administrator. Options granted under our 2025 Plan will vest at the rate specified in the option agreement as determined by the administrator. Prior to this offering, vested options are only permitted to be exercised during the exercise windows that occur within the exercise period or on the last day of the exercise period. The exercise windows are each of the full months of January, March, July and September, and any other time as determined by the compensation committee, that occurs during the exercise period. The exercise period starts on the vesting date of the relevant option and expires on the tenth anniversary of the grant date. Following this offering, vested options may be exercised at any time during the exercise period, excluding during black-out periods and subject to other limitations set forth in the 2025 Plan or as may be determined by our board of directors or the plan committee. Options that are not exercised prior to the expiration of the exercise period shall lapse and forfeit in full.

Unless the terms of an optionholder's option agreement provides otherwise, if an optionholder's service relationship with us or any of our affiliates ceases (i) for any reason other than disability, death, or retirement, or cause, the optionholder may generally exercise any vested options for a period of three months following the cessation of service; (ii) for cause, the optionholder may generally exercise any vested options for a period of three months following the date of notice of termination; or (iii) due to death, disability, or retirement, the optionholder may generally exercise any vested options for a period of 12 months following the cessation of service. In the event a participant's service terminates as a result of death or disability, the Company will have the right to repurchase any unvested portion of the participant's awards at fair market value within 90 days following the date of termination, and if the Company does not repurchase the awards, the participant's unvested awards will accelerate and vest in full on the expiration of such 90 day period. In each case, this period may be extended in the event that exercise of the option is prohibited by applicable securities laws. In no event may an option be exercised beyond the expiration of its exercise period.

Acceptable consideration for the purchase of common shares issued upon the exercise of an option includes (i) payment of the exercise price in cash; (ii) in the sole discretion of our board of directors or the duly authorized committee of our board of directors, a cash settlement or net settlement of the option (the latter only following this offering); or (iii) in the sole discretion of our board of directors or the duly authorized committee of our board of directors, a cashless exercise (including a same day sale or sale-to-cover).

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Upon a Change of Control, subject to the Shareholders'

Change of Control . Our 2025 Plan provides

Change of Control . Our 2025 Plan provides that upon a Change of Control (as defined in the 2025 Plan), and for as long as Luca Santarelli is a member of our board of directors, unless our board of directors resolves otherwise with a Qualified Board Majority (as defined in the 2025 Plan) including the positive vote or consent of Mr. Santarelli, all outstanding awards that would be unvested at the effective date of the Change of Control vest in full.

Upon a Change of Control, subject to the Shareholders' Agreement (as defined in the 2025 Plan), participants have the right (and, if demanded by our board of directors, the obligation) to: (i) exercise all vested options (including those vesting solely due to the Change of Control) immediately prior to the effective date and sell the resulting shares to the acquiror at the change of control price of our common shares; (ii) sell all vested options directly to the acquiror at the change of control price of our common shares, which, in the case of an option, is equal to the applicable per-share transaction price less the exercise price of the option; and/or (iii) sell shares resulting from the vesting of vested restricted share units to the acquiror at the change of control price of our common shares.

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Plan Amendment or Termination . Our board of

or Termination . Our board of directors has the authority to amend, suspend, or discontinue our 2025 Plan at any time, provided that such action does not alter or impair the existing rights of any participant without such participant's consent unless required by mandatory law or such participant is fairly compensated by other grants or cash payments. Our board of directors may cancel outstanding awards and replace them with new awards based on the fair market value on the new grant date, provided the terms of a re-grant are not more favorable to the participants than the cancelled awards. As noted above, no further awards will be granted under our 2025 Plan on or after the effectiveness of our 2026 Plan.

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In July 2025, the Company

In July 2025, the Company and Windward Bio AG or Windward Bio, Inc., as applicable, entered into certain restricted share purchase agreements, or RSPA, with certain employees of Windward Bio AG and Windward Bio, Inc., respectively, pursuant to which the Company sold and issued to such employees an aggregate of 930,800 common shares with a nominal value of CHF 0.01 each at a purchase price of CHF 0.01 per share (the restricted shares). These restricted shares were issued in August 2025 by way of a share capital increase within the Company's capital range at an issue price of CHF 0.01 per share, for an aggregate issue price of CHF 9,308.00.

The restricted shares issued under each of these RSPAs are subject to reverse vesting conditions and vest at the rate specified in the relevant RSPA as determined by our Chief Executive Officer who has been authorized by our board of directors to administer the RSPAs. The restricted shares that have not vested in accordance with the relevant RSPA are subject to a repurchase option exercisable, with respect to all or any portion of such restricted shares, by the Company (or any of its affiliates designated by it) in certain events as set forth in such RSPA, including if the service relationship of a holder of restricted shares with us or any of our affiliates ceases.

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Each 2026 FSRA provides that upon a Change of Control

Each 2026 FSRA provides that upon a Change of Control (as defined in the 2026 FSRA), and for as long as Luca Santarelli is a member of our board of directors, unless our board of directors resolves otherwise with a Qualified Board Majority (as defined in the 2026 FSRA) including the positive vote or consent of Mr. Santarelli, all 2026 founder shares that would be unvested at the effective date of the Change of Control vest in full.

Upon a Change of Control, subject to the Shareholders' Agreement (as defined in the 2026 FSRA), the founding shareholders have the right (and, if demanded by our board of directors, the obligation) to sell all vested 2026 founder shares (including those 2026 founder shares that have vested because of the Change of Control) to the acquiror at the change of control price of our common shares. If a founding shareholder did not elect to sell its vested 2026 founder shares into the Change of Control transaction, the Company (or any of its affiliates designated by it) shall have the right (but not the obligation) to repurchase all vested 2026 founder shares (including those 2026 founder shares that have vested because of the Change of Control) at the change of control price of our common shares.

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Under Swiss law, subject to certain

Under Swiss law, subject to certain limitations, a corporation may indemnify and hold harmless directors and other persons entrusted with its management out of the assets of the corporation from and against actions, costs, charges, losses, damages and expenses which they or any of them may incur or sustain by or by reason of any act done, concurred in or omitted, in connection with the execution of their statutory duties, provided that such indemnity (if any) shall not extend to any matter in which any of said persons is found to have committed an intentional or grossly negligent breach of his or her duties. Our articles of association contain provisions governing the indemnification of the members of our board of directors and of our executive committee and the advancing of related defense costs to the extent not included in insurance coverage or paid by third parties and to the extent permitted by Swiss law. In addition, under general principles of Swiss employment law, an employer may be required to indemnify an employee against losses and expenses incurred by such employee in the proper execution of his or her duties under the employment agreement with the employer. See the section of this prospectus titled "Comparison of Shareholder Rights under Swiss and Delaware Corporate Law—Indemnification of Directors and Executive Committee and Limitation of Liability."

We have entered, or intend to enter, as the case may be, into indemnification agreements with each of the members of our board of directors and of our executive committee prior to or in connection with the listing of our common shares on Nasdaq. We maintain directors' and officers' insurance to insure such persons against certain liabilities. See the section of this prospectus titled "Related Party Transactions—Agreements with Our Directors and Officers—Indemnification Agreements."

Insofar as indemnification of

Insofar as indemnification of liabilities arising under the Securities Act may be permitted to our board of directors, executive officers, or persons controlling us pursuant to the foregoing provisions, we have been informed that, in the opinion of the SEC, such indemnification is against public policy as expressed in the Securities Act and is therefore unenforceable.

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The shareholders' agreement will terminate immediately prior to the closing completion of this offering, except for the registration rights granted under our shareholders' agreement, as more fully described in "Description of Share Capital and Articles of Association—Registration Rights." The composition of our board of directors after this offering is described in more detail under "Management—Composition of our Board of Directors."

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Principal stockholders 1 change

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As of September 30, 2026, to our knowledge, common shares, representing % 28.4% of our issued and outstanding shares, were held by 10 U.S. shareholders of record, before giving effect to the Preferred Share Conversion and the Series B Warrant Settlement in connection with this offering.

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Description of the securities 59 changes

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Immediately prior to the

As of September 30, 2026, our share capital as registered

As of September 30, 2026, our share capital as registered in the commercial register of the Canton of Basel-Stadt, Switzerland, or the Commercial Register amounts to CHF 689,714.23 and is divided into 68,971,423 registered shares ( Namenaktien ) with a nominal value of CHF 0.01 each, consisting of 15,542,386 common shares ( Stammaktien ), 31,897,927 Series A preferred shares ( Vorzugsaktien A ), 5,582,139 Series A junior preferred shares ( Vorzugsaktien A Junior ) and 15,948,971 Series B preferred shares ( Vorzugsaktien B ). The preferred shares provide for preferential rights with respect to dividend distributions and/or liquidation proceeds for the Series A preferred shares, the Series A junior preferred shares and the Series B preferred shares, as described in our articles of association. Each issued share is fully paid.

Following the -to- reverse

split of our registered shares, the related issuance of additional registered shares and the issuance of common shares to be held in treasury immediately following the reverse share split, in each case effected on , 2026, our share capital registered in the Commercial Register amounts to CHF and is divided into registered shares with a nominal value of CHF each, consisting of common shares, Series A preferred shares, Series A junior preferred shares and Series B preferred shares.

Immediately prior to the completion of this offering, (i) the then outstanding 31,897,927 Series A preferred shares, 5,582,139 Series A junior preferred shares and 15,948,971 Series B preferred shares will be converted on a 1:1 basis into common shares, and (ii) common shares will be issued delivered out of common shares held in treasury upon cashless exercise of the Series B Warrants in the Series B Warrant Settlement, and (iii) we expect to issue an additional number of common shares to be held in treasury such that the total number of common shares to be held in treasury upon completion of this offering corresponds to 10% of the share capital registered in the Commercial Register immediately after completion of this offering. All shares will rank pari passu with each other and no preferred shares will be outstanding.

Upon the closing completion of this offering, based on the number of registered shares outstanding as of September 30, 2026, the changes to our share capital occurring prior to the completion of this offering and described in the preceding paragraphs, based on an assumed initial public offering price of $ per share, which is the midpoint of the price range set forth on the cover page of this prospectus, our outstanding fully paid-in share capital will consist of common shares (or common shares if the underwriters exercise their option to purchase additional common shares in the offering in full), with a nominal value of CHF 0.01 each.

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As of the date of our incorporation, our share capital

In this section, our share capital and the number and nominal value of shares are presented as of the date of the relevant transaction, without accounting for (i) the conversion -to- reverse split of our preferred shares into common registered shares effected on , 2026, or (ii) the Preferred Share Conversion immediately prior to the completion of this offering.

As of the date of our incorporation, our share capital as registered in the Commercial Register amounted to CHF 100,000, divided into 10,000,000 fully paid-in common shares with a nominal value of CHF 0.01 per share. Since our incorporation, the events described below have changed the number and classes of our issued and outstanding share capital.

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Certain Important Provisions of our Articles of Association, Organizational Regulations and Swiss Law The following is a summary of certain important provisions of our articles of association, organizational regulations and certain related provisions of Swiss law.

In the -to- reverse split of all issued shares effected on , 2026, common shares, Series A preferred shares, Series A junior preferred shares and Series B preferred shares, each with a nominal value of CHF 0.01 per share at an issue price of CHF 0.01 per share, were issued for the purpose of balancing fractions of shares as a result of such reverse share split, and common shares were consolidated into common shares, Series A junior preferred shares were consolidated into Series A junior shares, Series A preferred shares were consolidated into Series A preferred shares and Series B preferred shares were consolidated into Series B preferred shares, each with a nominal value of CHF per share. In addition, immediately after the -to- reverse split of all issued shares, common shares with a nominal value of CHF per share at an issue price of CHF per share were issued, which we intend to hold in treasury for the time being and which we expect to use in part for purposes of the Series B Warrant Settlement. As a result of the foregoing, our share capital as registered in the Commercial Register on , 2026 was increased by CHF .

Certain Important Provisions of our Articles of Association, Organizational Regulations and Swiss Law The following is a summary of certain important provisions of our articles of association, organizational regulations and certain related provisions of Swiss law. Please note that this is only a summary and is not intended to be exhaustive. For a more complete discussion, please refer to our articles of association, organizational regulations and Swiss law.

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Any subscription and

Any subscription and direct or indirect acquisition of new shares either in connection with or under an ordinary capital increase, capital range or conditional share capital and any subsequent transfer of such shares are subject to certain transfer restrictions (for more details see the section of this prospectus titled "Limitations Affecting Shareholders of a Swiss Company—Transfer of Shares and Transfer Restrictions").

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Our amended and restated articles of association provide for a capital range ranging from CHF a lower limit corresponding to CHF 90% of the share capital registered in the Commercial Register immediately after completion of this offering to an upper limit corresponding to 150% of the share capital registered in the Commercial Register immediately after completion of this offering, for various purposes. Within the capital range, our board of directors is authorized to increase or reduce the share capital of the Company once or several times and by any amounts, including through the issuance of up to a corresponding maximum number of fully paid-in registered shares, the cancellation of up to a corresponding maximum number of registered shares, an increase or reduction of the nominal value of existing shares or a simultaneous reduction and re-increase of the share capital, including in connection with an intended takeover. The capital range is in place until , 2031 (unless terminated earlier as a matter of Swiss law if the general meeting of shareholders resolves an ordinary capital increase or capital reduction outside the capital range, or to amend or abolish the capital range).

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purchase up to additional common shares at the public offering price following the completion of this offering, a corresponding number of common shares will be issued out of our capital range. Accordingly, upon the consummation of this offering, and assuming that such option will be exercised in full following the completion of this offering and the corresponding number of common shares will be issued out of the above-described capital range, we expect our board of directors being authorized within our capital range to issue up to common shares and to cancel up to common shares.

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Conditional Share Capital for Financing,

Acquisition and Other Purposes

Our share capital may be increased by a maximum aggregate amount corresponding to % of CHF the share capital registered in the Commercial Register immediately after completion of this offering through the issuance of up to a corresponding number of common shares, which would have to be fully paid-in, with a nominal value of CHF each, through the direct or indirect issuance of shares, or through the exercise or mandatory exercise of rights to acquire shares or through obligations to acquire shares, which were granted to or imposed on members of the board of directors, members of the executive committee, employees, contractors or consultants of the Company or one of its group companies, or other persons providing services to the Company or one of its group companies. Shares, rights or purchase obligations therefor shall be issued pursuant to one or more regulations to be issued by our board of directors, or to the extent delegated to it, our compensation committee, and in each case in accordance with our articles of association. Shares, rights or purchase obligations therefor may be issued at a price or with an exercise price lower than the market price or intrinsic value, as applicable. The pre-emptive subscription rights and advance subscription rights of our shareholders are excluded in connection with the issuance of any shares, options or subscription rights therefor.

Shares, rights or purchase obligations therefor shall be issued pursuant to one or more regulations to be issued by our board of directors, or to the extent delegated to it, our compensation committee, and in each case in accordance with our articles of association. Shares, rights or purchase obligations therefor may be issued at a price or with an exercise price lower than the market price or intrinsic value, as applicable. The pre-emptive subscription rights and advance subscription rights of our shareholders are excluded in connection with the issuance of any shares, options or subscription rights therefor.

Conditional Share Capital for Financing, Acquisition and Other Purposes In addition, our share capital may be increased by a maximum aggregate amount corresponding to % of CHF the share capital registered in the Commercial Register immediately after completion of this offering through the issuance of up to a corresponding number of common shares, which would have to be fully paid-in, with a nominal value of CHF each, through the exercise or mandatory exercise of conversion, exchange, subscription or other rights to acquire shares or through obligations to acquire shares which were granted to or imposed on shareholders or third parties alone or in connection with bonds, notes, options, warrants or other securities or contractual obligations by the Company or any of its group companies, including in connection with an intended takeover. The advance subscription rights of shareholders are excluded in connection with the issuance of any of the aforementioned financial instruments and the pre-emptive subscription rights of shareholders are excluded upon conversion, exchange, exercise or the triggering of any of the aforementioned financial instruments in connection with the issuance of common shares, and the then-current owners of such financial instruments are entitled or obligated to acquire the new common shares upon conversion, exchange, exercise or the triggering of any financial instrument. The issuance of such shares or financial instruments will be made in accordance with one or more resolutions to be issued by the board of directors, by which the board of directors determines the main conditions of such financial instruments. The issuance of such shares may be made at a price below the respective stock exchange price and the issuance of such financial instruments may be made below their intrinsic value.

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Our shares are uncertificated securities

uncertificated securities ( Wertrechte , within the meaning of article 973c of the CO) and, when administered by a custodian ( Verwahrungsstelle , within the meaning of the Federal Act on Intermediated Securities, or FISA) and credited to one or more securities deposit account(s) ( Effektenkonto ), qualify as intermediated securities ( Bucheffekten , within the meaning of the FISA). In accordance with article 973c of the CO, we will maintain a non-public register of uncertificated securities ( Wertrechtebuch ). We may at any time without the approval of our shareholders and at our cost convert shares issued as uncertificated securities into another form (including global certificates) or convert shares issued in one form into another form. Following the entry in the share register, a shareholder may at any time request from us a written confirmation in respect of the shares held by such shareholder. Shareholders are not entitled, however, to request the printing and delivery of certificates or the conversion of the shares in one form into another form.

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General meetings of shareholders must be convened by our

shareholders must be convened by our board of directors at least twenty days before the date of the meeting. The general meeting of shareholders is convened by way of a notice which may, at the election or our board of directors, be validly given by publication in the Swiss Official Gazette of Commerce or in a form that allows proof by text. The notice of a general meeting of shareholders must specify the date, beginning, mode and venue of the meeting, the agenda items, the proposals of our board of directors and the shareholder(s) who requested that a general meeting of shareholders be called or an item or proposal be included on the agenda (if any) (including a brief explanation), in case of elections, the names of the proposed candidates, and the name and address of the independent proxy. Except in the limited circumstances listed below, a resolution may not be passed at a general meeting of shareholders without proper notice. This limitation does not apply to proposals to convene an extraordinary general meeting of shareholders or to initiate a special investigation. No previous notification is required to put proposals to the meeting related to items already on the agenda or for debates of matters on which no resolution is to be taken.

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Pursuant to Swiss law and our articles of

Pursuant to Swiss law and our articles of association, shareholders who alone or together represent at least 0.5% of the share capital or of the votes may request that an item including a specific proposal be included on the agenda or that a specific proposal relating to an item be included in the notice convening a general meeting of shareholders. To be timely, the shareholder's request must be made at least 45 calendar days in advance of the meeting. The request must be made in writing and contain, for each of the agenda items, the following information:

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However, any shareholders already being registered with, and/or having been allocated, more than % of the share capital registered in the Commercial Register prior to the registration with the Commercial Register of our amended and restated articles of association (if any) will remain or will be registered with voting rights for such shares. Furthermore, our board of directors may resolve not to apply, in part or in full, these restrictions or limits by way of exception for justified reasons with the majority vote of two-thirds of all its members.

Our amended and restated

restated articles of association contain provisions that prevent investors from acquiring voting rights exceeding % of our issued share capital. Subject to Swiss law and our articles of association, no person or entity shall be registered in the share register as a shareholder with voting rights for, and no person or entity may directly or indirectly, formally, constructively or beneficially own, or otherwise control or direct, alone or together with third parties, voting rights (whether exercisable or not) with respect to, more than % of the share capital registered in the Commercial Register. Legal entities and partnerships or other groups of persons or joint owners who are interrelated to one another through capital ownership, voting rights, uniform management or otherwise linked as well as individuals, legal entities or partnerships who act in concert or otherwise act in a coordinated manner or acquire shares indirectly shall be treated as one single person. Specifically, if an individual or legal entity acquires common shares and, as a result, directly or indirectly, has voting rights with respect to more than % of the share capital registered in the Commercial Register, the common shares exceeding the limit of % shall be entered in the share register as shares without voting rights.

Specifically, if an individual or legal entity acquires common shares and, as a result, directly or indirectly, has voting rights with respect to more than % of the share capital registered in the Commercial Register, the common shares exceeding the limit of % shall be entered in the share register as shares without voting rights.

This restriction also applies to persons or entities who

who hold or acquire some or all of their shares through nominees, including via Cede & Co., New York (or any successor), as the nominee of The Depository Trust Company, New York, acting in its capacity as clearing nominee. Our board of directors may, in its own discretion, register persons who declare in the registration application that they hold the shares as nominees on behalf of third-party beneficiaries in the share register as shareholders with voting rights. However, if shares are being held by a nominee for third-party beneficiaries, which control or direct (alone or together with third parties) voting rights with respect to more than % of the share capital registered in the Commercial Register, our articles of association provide that our board of directors may cancel the registration of the shares with voting rights held by such nominee in excess of the limit of %. Furthermore, our articles of association contain provisions that allow our board of directors to make the registration with voting rights of shares held by a nominee subject to conditions, limitations and reporting requirements and to impose or adjust such conditions, limitations and requirements once registered. However, any shareholders already being registered with, and/or having been allocated, more than % of the share capital registered in the Commercial Register prior to the registration with the Commercial Register of our amended and restated articles of association (if any) will remain or will be registered with voting rights for such shares. Furthermore, our board of directors may resolve not to apply, in part or in full, these restrictions or limits by way of exception for justified reasons with the majority vote of two-thirds of all its members.

Further, no shareholder may exercise, directly or

exercise, directly or indirectly, voting rights with respect to own or represented shares in excess of % of the share capital registered in the Commercial Register. This voting rights limitation applies equally to parties acting in concert. Our board of directors may resolve not to apply this voting rights limitation by way of exception for justified reasons with the majority vote of two-thirds of all its members. This voting rights limitation does not apply to the exercise of voting rights by shareholders or their proxies to the extent that their shares are validly registered with voting rights in the share register pursuant to our articles of association and they are still in compliance with our articles of association.

Our board of directors may resolve not to apply this voting rights limitation by way of exception for justified reasons with the majority vote of two-thirds of all its members. This voting rights limitation does not apply to the exercise of voting rights by shareholders or their proxies to the extent that their shares are validly registered with voting rights in the share register pursuant to our articles of association and they are still in compliance with our articles of association.

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We are party to a shareholders' agreement that provides that certain holders of our common shares, including certain holders of at least 5% of our common shares and entities affiliated with certain of our directors, have certain registration rights, as set forth below. This shareholders' agreement was entered into in January 2025 and amended and restated in May 2026. The registration of our common shares by the exercise of registration rights described below would enable the holders to sell these shares without restriction under the Securities Act when the applicable registration statement is declared effective. We will pay the registration expenses, other than underwriting discounts and commissions and selling expenses of the holders, of the shares registered pursuant to the demand, piggyback, and Form S-3 or Form F-3 registrations described below. Generally, in an underwritten offering, the managing underwriter, if any, has the right, subject to specified conditions, to limit the number of shares such holders may include.

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The holders of an aggregate

The holders of an aggregate of common shares will be entitled to certain demand registration rights. At any time after 180 days following the effective date of the registration statement of which this prospectus forms a part, such holders are entitled to registration rights under the shareholders' agreement, provided that the holders of a majority of registrable securities then outstanding request that we register 40% of shares subject to such registration rights, with an anticipated aggregate offering price of such shares of at least $25 million, net of selling expenses. The demand registrations shall expire five years after the date of this offering and we will not be obligated to undertake more than two offerings pursuant to a demand registration in any twelve-month period.

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In connection with this offering, the

holders of an aggregate of common shares were entitled to, and the necessary percentage of holders waived, their rights to notice of this offering and to include their shares of registrable securities in this offering.

In connection with this offering, the holders of an aggregate of common shares were entitled to, and the necessary percentage of holders waived, their rights to notice of this offering and to include their shares of registrable securities in this offering. After this offering, in the event that we propose to register any of our securities under the Securities Act, either for our own account or for the account of other security holders, the holders of these shares will be entitled to certain piggyback registration rights allowing such holders to include their shares in such registration, subject to certain marketing and other limitations. As a result, whenever we propose to file a registration statement under the Securities Act, subject to certain exceptions, the holders of these shares are entitled to notice of the registration and have the right to include their shares in the registration, subject to limitations that the underwriters may impose on the number of shares included in the offering. If our proposed registration involves an underwritten offering, the underwriters of such offering have the right to limit the number of shares to be underwritten for reasons related to the marketing of the shares in accordance with the cut-back provisions of the shareholders' agreement.

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Dividends and other distributions (except, in the amount

Dividends and other distributions (except, in the amount permitted under Swiss tax law and subject to certain restrictions, for distributions from reserves from capital contributions or from reductions of the Company's share capital) paid on our common shares are subject to Swiss federal withholding tax. For a discussion of the taxation of dividends, see the section in this prospectus entitled "Swiss Tax Implications for Our Holders."

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If a shareholder has exercised their inspection or

If a shareholder has exercised their inspection or information rights as outlined above, such shareholder may propose to the general meeting of shareholders that specific facts be examined by a special examiner in a special investigation. If the general meeting of shareholders approves the proposal, we or any shareholder may, within 30 calendar days after the general meeting of shareholders, request the competent court to appoint a special examiner. If the general meeting of shareholders rejects the request, one or more shareholders representing at least 5% of the share capital or of the votes may request, within three months after the general meeting of shareholders, that the competent court appoints a special examiner. The competent court will issue such an order if the petitioners can furnish prima facie evidence that our corporate bodies or any member thereof infringed the law or our articles of association and thereby likely caused damage to us or the shareholders. The costs of the investigation would generally be allocated to us and only in exceptional cases to the petitioners.

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For business combinations effected in the

For business combinations effected in the form of a statutory merger or demerger and subject to Swiss law, the Swiss Merger Act provides that if equity rights have not been adequately preserved or compensation payments in the transaction are not adequate, a shareholder may request the competent court to determine an adequate amount of compensation. Shareholders who consider their equity rights not to have been adequately preserved or the compensation received or to be received to be inadequate are entitled to exercise appraisal rights in accordance with the Swiss Merger Act by filing a suit against the surviving corporation with the competent Swiss civil court at the registered office of the surviving corporation or of the transferring corporation. The suit must be filed within two months after the merger or demerger resolution has been published in the Swiss Official Gazette of Commerce. If such a suit is filed, the court must assess whether the equity rights have been adequately preserved or the compensation paid or to be paid to the shareholders is adequate compensation and, should the court consider it to be inadequate, determine any additional adequate compensation. A decision issued by a competent court in this respect can be acted upon by any person who has the same legal status as the claimant. The filing of an appraisal suit will not prevent completion of the merger or demerger.

In addition, under Swiss law, the

In addition, under Swiss law, the sale of all or substantially all of our assets may be construed as a de facto dissolution of the Company, and consequently require the approval of two-thirds of the votes represented at a general meeting of shareholders and the majority of the nominal value of the shares represented at such meeting. Whether a shareholder resolution is required depends on the particular transaction, and the following circumstances are generally deemed relevant in this respect:

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Indemnification of Directors and Executive Management

and Executive Management

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law requires a "say on pay" approval mechanism for the compensation of the board of directors and the executive committee pursuant to which the shareholders must vote on the compensation of the board of directors and the executive committee on an annual basis commencing with our first annual general meeting of shareholders following this offering to be held in 2027. In accordance with these requirements, our articles of association provide that the general meeting of shareholders must, each year, approve separately the proposals of the board of directors regarding the aggregate amounts of:

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Swiss law requires the

Swiss law requires the board of directors to prepare an annual audited compensation report disclosing, amongst other things, the compensation, loans and credits directly or indirectly awarded by the Company to members of the board of directors and the executive committee (and, to the extent not in line with market standards, to former members of and parties related to these bodies) during the past financial year. The compensation awarded to the board of directors has to be disclosed both on an aggregate basis as well as individually on a named basis for each director. The compensation awarded to the executive committee has to be disclosed on an aggregate basis; in addition, the compensation of the highest paid member of the executive committee needs to be disclosed individually on a named basis. In case the company pays compensation out of the supplementary amount as described above, such compensation has to be disclosed on an aggregate basis. In addition, we have to disclose the shares and other equity-linked positions held by members of the board of directors and of the executive committee or persons closely related to them in the compensation report.

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Repurchases of Shares and Purchases of Own Shares

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Shares held by us or our subsidiaries are not entitled to

Shares held by us or our subsidiaries are not entitled to vote at the general meeting of shareholders but are entitled to the economic benefits applicable to the shares generally, including dividends, pre-emptive subscription rights in the case of share capital increases and advance subscription rights.

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Shares eligible for future sale 1 change

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As soon as practicable after the closing completion of this offering, we intend to file with the SEC one or more registration statements on Form S-8 under the Securities Act to register the common shares subject to outstanding share options or reserved for issuance under our equity incentive plans. These registration statements will become effective immediately upon filing. Shares covered by these registration statements will then be eligible for sale in the open market, subject to vesting restrictions, any applicable lock-up agreements described below and Rule 144 limitations applicable to affiliates.

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Index to condensed consolidated interim financial statements 8 changes

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Form of Amended and Restated Articles of Association of the Registrant, to be in effect immediately prior to the closing completion of this offering.

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Pursuant to the requirements of the Securities Act of 1933, the registrant certifies that it has reasonable grounds to believe that it meets all of the requirements for filing on Form F-1 and has duly caused this registration statement to be signed on its behalf by the undersigned, thereunto duly authorized, in Basel, Switzerland on this 23rd 30th day of October, 2026.

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We, the undersigned directors, officers and/or authorized representative in the United States of Windward Bio Group AG, hereby severally constitute and appoint Luca Santarelli, Claudia D'Augusta and Scott Applebaum, and each of them singly, our true and lawful attorneys-in-fact and agents, with full power to any of them, and to each of them singly, to sign for us and in our names in the capacities indicated below the registration statement on Form F-1 filed herewith, and any and all pre-effective and post-effective amendments to said registration statement, under the Securities Act of 1933, as amended, in connection with the registration under the Securities Act of 1933, as amended, of equity securities of Windward Bio Group AG, and to file or cause to be filed the same, with all exhibits thereto and other documents in connection therewith, with the U.S. Securities and Exchange Commission, granting unto said attorneys-in-fact and agents, and each of them, full power and authority to do and perform each and every act and thing requisite and necessary to be done in connection therewith, as fully to all intents and purposes as each of them might or could do in person, and hereby ratifying and confirming all that said attorneys-in fact and agents, and each of them, or their substitute or substitutes, shall do or cause to be done by virtue of this Power of Attorney. Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following person in the capacities and on the date indicated.

Pursuant to the requirements of the Securities Act of 1933, as amended, this Registration Statement has been signed by the following persons in the capacities and on the date indicated.

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/s/ Timothy Anderson

/s/ Naveed I. Siddiqi

/s/ Otello Stampacchia

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Pursuant to the requirements of the Securities Act of 1933, the undersigned, the duly authorized representative in the United States of the registrant has signed this registration statement, on October 23, 30, 2026.

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