AVIR 10-K & 10-Q changes, risk factors and insider trading

We are a clinical-stage biopharmaceutical company. Our operations to date have been limited to financing and staffing our company, developing our technology, and identifying and developing our product candidates. Our prospects must be considered in light of the uncertainties, risks, expenses and difficulties frequently encountered by biopharmaceutical companies in their early stages of operations. We have not yet demonstrated an ability to successfully develop, obtain marketing approval, manufacture a product aton a commercial-scale, or conduct sales and marketing activities necessary for successful product commercialization, or have third parties to do these activities on our behalf. Consequently, predictions about our future success or viability may not be as accurate as they could be if we had a longer operating history or a history of successfully developing, obtaining marketing approval for and commercializing antiviral therapies.

As we continue to build our business, including beginningcompleting Phase 3 clinical trials and completingpreparing lateand stagepotentially clinicalsubmitting trials,applications seeking marketing approval for our HCV product candidate, we expect our financial condition and operating results may fluctuate significantly from quarter to quarter and year to year due to a variety of factors, many of which are beyond our control. Accordingly, you should not rely upon the results included in this report or reports for any other particular prior quarterly or annual period as indications of future operating performance.

We have incurred significant operating expenses since our inception. For the years ended December 31, 20242025 and 2023,December 31, 2024, our operating expenses were $192.9$180.9 million and $164.2$193.0 million, respectively. As of December 31, 2024,2025, we had an accumulated deficit of $364.2$522.6 million.

In order to obtain the FDA’s or a foreign regulatory authority’s approval to market any product candidate in the US or abroad, respectively, we must submit to the FDA a New Drug Application (“NDA”) or similar application to the foreign regulatory authority demonstrating to the FDA’s or foreign regulatory authority’s satisfaction that the product candidate is safe and effective for its intended use(s). This demonstration requires significant research and extensive data from in vitro and in vivo laboratory experiments and animal tests, which are referred to as nonclinical or preclinical studies, as well as human tests, which are referred to as clinical trials. Additionally, extensive data related to the chemistry and physical characteristics of the product candidate, the intended packaging of the commercial product, the processes to be used for consistently manufacturing the product candidate in commercial quantities in accordance with certified Good Manufacturing Practices (“GMP”) and the results of stability studies to establish shelf life of the product must also be included in the NDA and similar foreign regulatory applications.

Furthermore, the costs of advancing product candidates into each succeeding clinical development phase tend to increase substantially over time. For example, as we advanced and completed the enrollmentcosts of our COVID-19HCV Phase 3 SUNRISE-3development clinicalprogram trial,are substantially greater than the costs we incurred in our operatingPhase expenses2 increased.development Weprogram. anticipateThese thatincreased operatingPhase expenses3 willcosts alsoare increaseattributable to a number of factors including a significantly increased number of patients enrolled in the futurePhase as3 we advanceprogram and completecosts associated with the use of an active comparator in the Phase 3 clinicalprogram trialswhich evaluatingwas not a part of the regimenPhase of2 bemnifosbuvir and ruzasvir for the treatment of HCV as well as any additional late stage clinical trials.program. Because of the numerous risks and uncertainties associated with the development of our product candidates, we are unable to accurately predict the timing or amount of increased expenses or when, or if, we will be able to begin generating revenue from the commercialization of products or again achieve profitability.

successfully complete clinical trials and seek regulatory approval for ourthe regimen of bemnifosbuvir and ruzasvir for the treatment of HCV AT-587 for the treatment of HEV or other product candidates, if any;

establish long-term manufacturing and supply chain capacitycapacity, including US domestic manufacturing capacity, sufficient to provide long term commercial quantities of any product candidates for which we may obtain marketing approval, if any;

hire additional staff, including clinical, scientific, technical, regulatory, operational, financial, commercial and support personnel, to execute our business plan and support our product candidate discovery, development and potential future commercialization efforts;

Furthermore, our ability to successfully develop, commercialize and license any products and generate product revenue is subject to substantial additional risks and uncertainties. Our HCV and HEV product candidatecandidates and any future product candidates we may discover, license or otherwise acquire, will require regulatory approval in not less than one jurisdiction, the securing of manufacturing supply, capacity, distribution channels and expertise, the use of external vendors, the building of or other access to a commercial organization, substantial investment and significant marketing efforts before we generate any revenue from product sales. Additionally, our HCV and HEV product candidatecandidates and any future product candidates will require additional preclinical and clinical development. As a result, we expect to continue to use cash for operating activities and incur operating expenses and operating losses for the foreseeable future. The use of cash and incurrence of operating expenses and operating losses has had, and we expect will continue to have, an adverse effect on our working capital.

The amount of future expenses or losses and our ability to achieve or maintain profitability in future years, if ever, are uncertain. We have no products that have generated any commercial revenue, do not expect to generate revenues from the commercial sale of products in the near term, and might never generate revenues from the sale of products. Our ability to generate product revenue and maintain profitability will depend on, among other things, successful completion of the clinical development of our HCV and HEV product candidatecandidates and other product candidates, if any; obtaining necessary regulatory approvals from the FDA and foreign regulatory authorities; establishing manufacturing and sales capabilities; successfully manufacturing commercial scale quantities of products, market acceptance of our products, if approved, and establishing marketing infrastructure or otherwise arranging to commercialize our product candidates for which we obtain approval; and raising sufficient funds to finance our activities. We might not succeed at any of these undertakings. If we are unsuccessful at some or all of these undertakings in the future, our business, prospects, and results of operations may be materially adversely affected.

Since inception, we have incurred substantial operating expenses. We expect to incur substantial expenses in connection with our current and planned business activities, particularly completing the late stage development of the regimen of bemnifosbuvir and ruzasvir.ruzasvir, the manufacture of commercial launch supply, the preparation and submission of an NDA and other similar applications seeking marketing approval for our HCV product candidate. Also, we anticipate that we may incur substantial expenses in connection with the development of AT-587 for the treatment of HEV, and in connection with the discovery, license or other acquisition and potential development of other product candidates, if any,any. and, ifIf we successfully develop oneand receive regulatory approval to market the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV or moreany other product candidates, we expect we will also incur substantial expenses in connection with the establishment of sales, marketing, internal systems and distribution infrastructure to commercialize anysuch productsproducts. forAdditionally, whichin April 2025, our Board authorized the utilization of up to $25.0 million of cash to repurchase our common stock (“Share Repurchase Program”). As of December 31, 2025, we mayhave obtaincompleted regulatorythe approval.Share Repurchase Program expending the total authorized amount of $25.0 million, net of transaction costs and excise taxes. Under the Share Repurchase Program, we repurchased, retired and returned to authorized but unissued status 7,673,792 shares of common stock.

the timing of and costs associated with the development of AT-587 for the treatment of HEV and the discovery, license or acquisition of a product candidate for the treatment of respiratory or other diseases resulting from infection with single stranded RNA viruses;

the costs, timing and changes in pharmaceutical pricing and reimbursement infrastructure resulting from, among other things, the enactment of the Inflation Reduction Act (“IRA”) and other legislationlegislation, regulations, executive orders and regulationsother initiatives and policies that may be subsequently enacted;

In the future, we may enter into strategic collaborations or other transactions. InWhile we remain open to consideration of a broad range of strategic alternatives, including strategic partnerships, acquisition, merger, or other business combination, sale of assets or other strategic transactions, we believe that it is most likely that actionable alternatives may be available after we receive the fourthresults quarter of 2024, we announced that we had engaged Evercore LLC, a global independent investment bank, to assist us in identifying and exploring potential strategic partnerships related to our regimen offrom the bemnifosbuvircurrently andongoing ruzasvir.HCV WhilePhase this3 processclinical isprogram. ongoing, thereThere is no assurance that itwe will result in the completion ofconclude any specific transaction or outcome. If we do identify suitable collaboration candidates or strategic partners, we may not be able to complete such collaborations or other strategic transactions timely or on favorable terms, or at all. Any collaborations or other strategic transactions may not strengthen our competitive position, and these transactions may be viewed negatively by stock research analysts or investors, and we may never realize the anticipated benefits of such transactions. We may decide to issue our common stock or other equity securities to a strategic partner or collaborator which would reduce the percentage ownership of our existing stockholders. In addition, we may not be able to successfully integrate with any collaborator or strategic partner in an effective, timely and non-disruptive manner. Collaborations or other strategic transactions may also divert management attention from day-to-day responsibilities, lead to a loss of key personnel, increase our expenses and reduce our cash and cash equivalentsinvestments available for operations and other uses. We cannot predict the number, timing or size of future collaborations or strategic partnerships or the effect that any such transactions might have on our operating results.

We incurred a net loss of $168.4$158.3 million for the year ended December 31, 2024.2025. Our ability to achieve and sustain future profitability depends upon our ability to generate revenue from product sales. We have not generated product revenue and we do not expect to generate product revenue unless or until we successfully complete clinical development and obtain regulatory approval of, and then successfully commercialize, at least one of our product candidates. Our HCV and HEV product candidatecandidates and future product candidates, if any, will require additional preclinical and clinical development, regulatory review and approval, substantial investment in and access to sufficient commercial manufacturing capacity and significant marketing efforts before we can generate any revenue from product sales. Currently, we do not anticipate generating revenue from product sales for at least the next few years. Our ability to generate revenue depends on a number of factors, including, but not limited to:

our ability to complete additional investigational drug application (“IND”) enabling studies and successfully submit INDs, clinical trial application (“CTAs”) or comparable applications to allow us to initiate clinical trials for AT-587, our HEV product candidate, and any other product candidates;

whether we are required by the FDA or similar foreign regulatory authorities to conduct additional clinical trials or other studies beyond those planned to support the approval and commercialization of our HCV and HEV product candidatecandidates or any future product candidates;

our ability to demonstrate to the satisfaction of the FDA or similar foreign regulatory authorities the safety and efficacy of our HCV and HEV product candidatecandidates or any future product candidates;

the prevalence, duration and severity of potential side effects or other safety issues experienced with our HCV and HEV product candidatecandidates or future product candidates, if any;

the timely receipt of necessary marketing approvals from the FDAFDA, orEuropean similarMedicines Agency ("EMA") and other foreign regulatory authorities;

the availability, actual and perceived advantages and relative cost, convenience, safety and efficacy of our HCV and HEV product candidatecandidates or other product candidates we may be able to commercialize, compared to other commercially available therapies for the targeted indications, or, in the case of HEV other interventions, as well as the accuracy and sufficiency of clinical evidence supporting any such advantages of our product candidates;

the willingness of physicians, operators of clinics and patients to conduct or participate in clinical trials evaluating our product candidates and, if successfully developed, to utilize or adopt our HCV and HEV product candidatecandidates or any future product candidates, if approved as antiviral therapies;

our ability and the ability of third parties with whom we contract to manufacture adequate clinical and commercial supplies of our HCV and HEV product candidates or future product candidates, remain in good standing with regulatory authorities and develop, validate and maintain commercially viable manufacturing processes that are compliant with current good manufacturing practices (“cGMP”) or similar requirements outside the US;

our ability to successfully establish a commercial strategy and thereafter commercialize our HCV and HEV product candidatecandidates or any future product candidates, in the US and internationally, if approved for marketing, reimbursement, sale and distribution in such countries and territories, whether alone or in collaboration with others; and our ability to establish, maintain, protect and enforce intellectual property rights in and to our HCV and HEV product candidatecandidates or any future product candidates.

Our business is highly dependent on the success of our lead product candidate, the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, which will require significant additional clinical testing, including successful completion of Phase 3 clinical testing, before we can seek regulatory approval and potentially launch commercial sales. If this product candidate fails in clinical development, does not receive regulatory approval or is not successfully commercialized, or is significantly delayed in doing so, our business will be harmed.

During the near termterm, we expect thatto adevote substantial portion of our efforts and expendituresfinancial will be devotedresources to developingcomplete the Phase 3 clinical development of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCVHCV, which will require additional clinical development, management ofmanage clinical, medical affairs and manufacturing activities, obtainingincluding the manufacture of commercial launch supply, seek and obtain regulatory approvals in multiple jurisdictions, securingsecure additional sources of manufacturing supply,supply buildingand ofcapacity, build or otherwise accessingaccess a commercial organization, substantialand investmentengage andin significant marketingpre-launch efforts.

We cannot be certain that our HCV product candidate, our HEV product candidate or any future product candidates will be successful in clinical trials, receive regulatory approval or be successfully commercialized even if we receive regulatory approval. Further, our development of any product candidate may be delayed or suspended, which may affect our ability to successfully commercialize such product candidate. Additionally, our ability to successfully commercialize a product will also be dependent upon our ability to timely manufacture at commercial scale the quantities of product that will satisfy market demand.

Even if we receive approval to market our HCV product candidate, our HEV product candidate or any other product candidate, we cannot be certain that such product candidate will be as or more effective than commercially available alternatives successfully commercialized or widely accepted in the marketplace. There are currently approved and well established oral antiviral HCV products against which we would be required to compete if the regimen of bemnifosbuvir and ruzasvir is approved.approved for the treatment of HCV.

We cannot be certain that, if approved, the safety and efficacy profile of the regimen of bemnifosbuvir and ruzasvir will be consistent with the results observed in clinical trials. If we are not successful in the clinical development of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, if the required regulatory approvals for this product candidate are not obtained, if there are significant delays in the development or approval of this product candidate or in supplying commercial quantities of the regimen of bemnifosbuvir and ruzasvir or any approvedother productsproduct, if approved, on an uninterrupted basis, or if we are otherwise not commercially successful, our business, financial condition and results of operations may be materially harmed.

We have not submitted an NDA for, or obtained regulatory approval of, any product candidate. We must complete additional clinical and preclinical studies to demonstrate the safety and efficacy of our product candidates in humans to the satisfaction of the regulatory authorities before we will be able to obtain these approvals, and it is possible that neithernone of our HCV product candidate nor any product candidates we may seek to develop in the future will ever obtain regulatory approval. Applications for our product candidates could fail to receive regulatory approval for many reasons, including but not limited to the following:

Clinical development, including enrollment of patients in clinical trials, is an expensive, lengthy and uncertain process. We may encounter substantial delays and costs in our clinical trials,trials or may not be able to conduct or complete our clinical trials on the timelines we expect, if at all.

Before obtaining marketing approval from the FDA or other comparable foreign regulatory authorities for the sale of our product candidates, we must complete preclinical development and extensive clinical trials to demonstrate the safety and efficacy of our product candidates. Clinical testing is expensive, time-consuming and subject to uncertainty. A failure of one or more clinical trials can occur at any stage of the process, such as the failure in September 2024 of bemnifosbuvir to meet the primary endpoint in the COVID-19 Phase 3 SUNRISE-3 clinical trial. The outcome of preclinical studies and early-stage clinical trials may not be predictive of the success of later clinical trials. Moreover, preclinical and clinical data, particularly the analysis of exploratory endpoints and analysis of data derived from patient subgroups, including in the case of HCV, patients infected with varying viral genotypesgenotypes, are often susceptible to varying interpretations, and many companies that have believed their product candidates performed satisfactorily in preclinical studies and varying stages of clinical trials have nonetheless failed to obtain marketing approval of their drugs.

To date, we have not successfully concluded any late-stage or pivotal clinical trials for any of our product candidates. We cannot guarantee that any of our planned or ongoing clinical trials will be initiated or conducted as planned or completed on schedule, if at all. We also cannot be sure that submission of any future IND or similar application for AT-587 or any future product candidate will result in the FDA or other regulatory authority, as applicable, allowing future clinical trials to begin in a timely manner, if at all. Moreover, even if thesefor trials begin,that begin or have begun, issues may arise that could cause regulatory authorities to suspend or terminate such clinical trials.

delays in obtaining required institutional review board (“IRB”) or ethics committee approval or positive opinion at each clinical trial site;

developments during the course of a clinical trial that cause the FDA, a foreign regulatory authority or the clinical trial data safety monitoring board (“DSMB”) to find that the investigational protocol or plan is clearly deficient to meet its stated objectives;

clinical trials of our product candidates producing negative or inconclusive results, which may result in our deciding, or regulators requiring us,us to conduct additional clinical trials or abandon development of such product candidates;

transfer of manufacturing processes to larger-scale facilities operated by a contract manufacturing organization (“CMO”) and delays or failure by our CMOs or us to make any necessary changes to such manufacturing process; and third parties being unwilling or unable to satisfy their contractual obligations to us.

Any inability to successfully complete our Phase 3 clinical trials evaluating the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV or the completion of any other planned clinical trials we may initiate for our HEV product candidate or otherwise could result in additional costs to us or impair our ability to seek approval for our HCV and HEV product candidate or any future product candidates and ultimately generate revenue from product sales.

We could also encounter delays if a clinical trial is suspended or terminated by us, by the DSMB for such trial, or by the FDA or any other regulatory authority, or if the IRBsinstitutional review boards of the institutions at which such trials are being conducted suspend or terminate the participation of the clinical investigators and sites subject to their review. Such authorities may suspend or terminate a clinical trial due to a number of factors, including failure to conduct the clinical trial in accordance with regulatory requirements or our clinical protocols, inspection of the clinical trial operations or trial site by the FDA or other regulatory authorities resulting in the imposition of a clinical hold, unforeseen safety issues or adverse side effects, failure to demonstrate a benefit from using a product candidate, changes in governmental regulations or administrative actions or lack of adequate funding to continue the clinical trial.

Further, conducting clinical trials in foreign countries, as we are currently doingcountries for our HCV and HEV product candidatecandidates and otherwise expect to do foror other product candidates, if any, presents additional risks that may delay completion of our clinical trials. These risks include the failure of enrolled patients in foreign countries to adhere to clinical protocol as a result of differences in healthcare services or cultural customs, managing additional administrative burdens associated with foreign regulatory schemes, as well as political and economic risks relevant to such foreign countries. For example, as part of our C-FORWARD HCV Phase 3 clinical trial, we are anticipating that clinical trial sites in Ukraine will enroll patients in the study. To the extent that these patients are not able to complete the study or there is a loss of data related to those patients as a result of the ongoing conflict in that area or otherwise, there may be a delay in completing the study or an adverse impact on the results from the study.

In addition, the FDA’s and other regulatory authorities’ policies with respect to clinical trials being conducted outside North America may change and additional government regulations may be enacted. For instance, with very limited exception for certain EU countries and certain clinical trials, the regulatory landscape related to clinical trials in the EU recently evolved. The EU CTR which was adopted in April 2014 and repeals the EU Clinical Trials Directive (“EU Clinical TrialTrials Directive”), became applicable on January 31, 2022. While the EU Clinical Trials Directive required a separate CTA to be submitted in each member state in which the clinical trial takes place, to both the competent national health authority and an independent ethics committee, the CTR introducesintroduced a centralized process and only requires the submission of a single application for multi-center trials. The CTR allows sponsors to make a single submission to both the competent authority and an ethics committee in each member state, leading to a single decision per member state. The assessment procedure of the CTA has been harmonized as well, including a joint assessment by all member states concerned, and a separate assessment by each member state with respect to specific requirements related to its own territory, including ethics rules. Each member state’s decision is communicated to the sponsor via the centralized EU portal. Once the CTA is approved, clinical study development may proceed. AsWith ofvery Januarylimited 31,exception 2025,for certain EU countries and certain clinical trials, all CTAs and clinical trials conducted in the EU (including those which are ongoing) are subject to the provisions of the CTR. As a result, the CTAs we submithave submitted in connection with the proposed conduct of our HCV Phase 3 clinical trial in the EU mustwere beprepared in compliance with the CTR requirements. We have limited experience submitting applications under the CTR. If we or our third-party service providers, such as CROs, encounter difficulties or are unable to comply with the CTR requirements our developments plans would be adversely impacted.

If the FDA or similar foreign regulatory authorities do not approve the combination agents or revoke theirthe approval thereof, or if safety, efficacy, manufacturing, or supply issues arise with the drugs we choose to evaluate in combination with our product candidates, we may be unable to obtain approval of or market our product candidates for combination therapy regimens.

Our product candidates may be associated with serious adverse events,events (“SAEs”), undesirable side effects or have other properties that could halt their clinical development, prevent their regulatory approval, limit their commercial potential or result in significant negative consequences.

Adverse events (“AEs”) or other undesirable side effects caused by our product candidates could cause us, our collaborators, any DSMB for a trial, or regulatory authorities to interrupt, delay or halt clinical trials and could result in a more restrictive label or the delay or denial of regulatory approval by the FDA or other comparable foreign regulatory authorities.

If any SAEs occur, clinical trials or commercial distribution of any product we successfully develop could be suspended or terminated, and our business could be seriously harmed. Treatment-related side effects could also affect patient recruitment and the ability of enrolled patients to complete the trial or result in potential liability claims. Regulatory authorities could order us to cease further development of, deny approval of, or require us to cease selling any product candidate or product for any or all targeted indications. If we are required to delay, suspend or terminate any clinical trial or commercialization efforts, the commercial prospects of such product candidate or product may be harmed, and our ability to generate revenues from such product or that we develop may be delayed or eliminated. Additionally, if one or more of our product candidates receives marketing approval and we or others later identify undesirable side effects or adverse events caused by such products, a number of potentially significant negative consequences could result, including but not limited to:

Enrollment of patients and timely completion of our clinical trials depends on many factors, including but not limited to:

the risk that patients enrolled in the clinical trial will fail to adhere to the protocol; and other factors outside of our control, such as political unrest, war, terrorism and the occurrence of a global health crisis similarsuch toas COVID-19 which, among other things, created substantial burdens on healthcare providers who were required to prioritize immediate critical patient care over clinical research.

A Fast Track designation by the FDA may not lead to a faster development or regulatory review or approval process,process and does not increase the likelihood that our product candidates will receive marketing approval.

If a product candidate is intended for the treatment of a serious or life-threatening condition and the product candidate demonstrates the potential to address unmet medical needs for such condition, the product candidate sponsor may apply for Fast Track designation. The sponsor of a product candidate that has received Fast Track designation may have opportunities for more frequent interactions with the FDA review team during product development and, once aan NDA is submitted, the NDA may be eligible for priority review. An NDA for a Fast Track designated product candidate may also be eligible for rolling review, where the FDA may consider review of sections of the NDA on a rolling basis before the complete NDA is submitted.

The FDA has broad discretion whether or not to grant Fast Track designation to any particular product candidate. As a result, we may seek such Fast Track designation for otherour product candidates, but cannot assure you that the FDA would decide to grant it. Even if a Fast Track designation has been received, the sponsorwe may not experience a faster development process, review or approval compared to conventional FDA procedures. The FDA may withdraw Fast Track designation if it believes that the designation is no longer supported by data from our clinical development program. Many product candidates that have received Fast Track designation have nevertheless failed to obtain approval.

Part of our strategy involves identifying novel product candidates. For example, we are currently conducting IND/CTA enabling studies of AT-587 for the treatment of HEV and are engaged in internal efforts to identify product candidates for the treatment of respiratory and other diseases resulting from infection with single stranded RNA viruses.

Our efforts to discover such product candidates and any subsequent discovery efforts we initiate to identify other noveladditional product candidates may fail to yield product candidates for clinical development for a number of reasons, including those discussed in these risk factors and also:

potential product candidates may, onin further study, be shown to have harmful side effects, toxicities or other characteristics that indicate that they are unlikely to be products that will receive marketing approval or achieve market acceptance, if approved;

Furthermore, we have limited financial and personnel resources and are placing significant focus on the development of our lead product candidate, the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, and the development of AT-587 for the treatment of HEV and as such, we may forgo or delay pursuit of opportunities with other future product candidates that later prove to have greater commercial potential. Our resource allocation decisions may cause us to fail to capitalize on viable commercial products or profitable market opportunities. Our spending on current and future research and development programs and other future product candidates for specific indications may not yield any commercially viable future product candidates. If we do not accurately evaluate the commercial potential or target market for a particular product candidate, we may relinquish valuable rights to such product candidate through collaboration, licensing or other royalty arrangements in cases in which it would have been more advantageous for us to retain sole development and commercialization rights to such future product candidates.

We are developing our product candidates for the treatment of serious conditions,conditions and therefore may decide to seek approval of such product candidates under the FDA’s accelerated approval pathway. A product candidate may be eligible for accelerated approval if it is designed to treat a serious or life-threatening disease or condition and generally provides a meaningful advantage over available therapies, upon a determination that the product candidate has an effect on a surrogate endpoint or intermediate clinical endpoint that is reasonably likely to predict clinical benefit. The FDA considers a clinical benefit to be a positive therapeutic effect that is clinically meaningful in the context of a given disease, such as irreversible morbidity or mortality. For the purposes of accelerated approval, a surrogate endpoint is a marker, such as a laboratory measurement, radiographic image, physical sign, or other measure that is thought to predict clinical benefit,benefit but is not itself a measure of clinical benefit. An intermediate clinical endpoint is a clinical endpoint that can be measured earlier than an effect on irreversible morbidity or mortality that is reasonably likely to predict an effect on irreversible morbidity or mortality or other clinical benefit.

The accelerated approval pathway may be used in cases in which the advantage of a new drug over available therapy may not be a direct therapeutic advantage,advantage but is a clinically important improvement from a patient and public health perspective. If granted, accelerated approval is usually contingent on the sponsor’s agreement to conduct, in a diligent manner, confirmatory studies to verify and describe the drug’s clinical benefit. If the sponsor fails to conduct such studies in a timely manner, or if such confirmatory studies fail to verify the drug’s predicted clinical benefit, the FDA may withdraw its approval of the drug on an expedited basis. Additionally, as a part of the Food and Drug Omnibus Reform Act of 2022, the FDA obtained statutory authority to mitigate potential risks to patients from continued marketing of ineffective drugs previously granted accelerated approval. Under these provisions, the FDA may require a sponsor of a product seeking accelerated approval to have a confirmatory trial underway prior to such approval being granted.

We are a clinical-stagelate-stage clinical biopharmaceutical company leveraging our deep understanding of antiviral drug development, medicinal chemistry, biology, biochemistry and virology to discoverdiscover, develop and developcommercialize novelnovel, orally administered product candidatesantivirals to treat serious viral diseases. Our leadcurrent product candidate ispipeline aincludes the regimen consisting of bemnifosbuvir and ruzasvir,ruzasvir which we arebelieve developinghas the potential to improve the current standard of care (“SOC”) for the treatment of patients with hepatitis C virus (“HCV”) infection.infection Currently,and AT-587 which we expectbelieve has the potential to commencebe enrollmentthe first direct-acting antiviral (“DAA”) for the treatment of patientspatients, inparticularly animmunocompromised HCVpatients, Phasewith 3chronic programhepatitis evaluatingE thevirus regimen(“HEV”) in April 2025.infection.

The objective of our HCV development program is to improve upon the current standard of care ("SOC") by offering, the regimen ofoffering bemnifosbuvir and ruzasvir, if successfully developed and approved,ruzasvir as a differentiated pan-genotypic protease inhibitor-freeinhibitor-free, therapeuticshort-duration regimen for HCV-infectedpatients patients.infected with HCV, if successfully developed and approved. We believe that a novel treatment,treatment with a profileregimen that can be easily prescribed forwill benefit today’s HCV population, which is predominately young (20-49 years old) and administerednon-cirrhotic, toand today’s population of HCV-infected patients (e.g. young, newly infected, non-cirrhotic)it would be a significant improvement to the current SOC.

Presently, there are no short-course (i.e., 8eight week) nucleosidenucleotide inhibitor-based, pan-genotypic HCV treatment regimens. Results from the clinicalClinical and nonclinical results from studies we have conducted to date, including a global Phase 2 clinical trial which enrolled 275 HCV infected patients, have shown that the regimen of bemnifosbuvir and ruzasvir offershas high potency,potency and has been well tolerated. These studies have also shown that the regimen has a low risk for drug-drug interactions,interactions goodwith tolerabilitymany commonly prescribed medications including proton pump inhibitors and offers the convenience inof thatbeing itable canto be taken with or without foodfood. whichThis is a profile that we believe wouldwill offer a significant improvement to the current SOC, if approved.

The global HCV Phase 3 program we are currentlyconducting initiatingconsists includesof two randomized, open label studies: C-BEYOND which has clinical trial sites in the US and Canada, and C-FORWARD which has clinical trial sites in countries outside of North America. In these Phase 3 trials we are comparing theour regimen of bemnifosbuvir and ruzasvir to an active comparator, the regimen of sofosbuvir and velpatasvirvelpatasvir, in patients with chronic HCV infection. The overall clinical trial design is identical for each trial. Currently, weWe are planningconducting forthe onePhase trial3 program in geographically diverse regions in order to be conducted in the U.S and Canada and one trial to be conducted outside of North America. This global geographic footprint is intended to assist us in enrollingenroll patients with varieda broad array of HCV genotypes.

RespiratoryDiscovery andefforts Otherfor other RNA Virusvirus Infectionsinfections

In addition to a non-refundable upfront payment that we made in February 2022, we will be requiredagreed to pay Merck milestone payments upon our achievement of certain development, regulatory and sales-based milestones. Additionally, we will pay Merck tiered royalties based on annual net sales of Products ranging from high single digits to mid-teens percentages. Our royalty payment obligations will continue until the later of (i) the expiration of the last to expire valid claim of a licensed Merck patent claiming such Product and (ii) a period of years after the first commercial sale of such Product in such country. We may terminate the Merck License Agreement for convenience upon prior written notice. The first milestone,milestone in the amount of $5.0 million became due and payable in April 2025 when we enrolled our first patient in C-BEYOND, the Phase 3 clinical trial that we are currently conducting in the US and Canada evaluating the regimen of bemnifosbuvir and ruzasvir. The Company recognized this milestone payment as research and development expense in the three months ended June 30, 2025. The next potential milestone, in the amount of $10.0 million, is payable upon initiationacceptance by the FDA of a new drug application covering a product candidate including ruzasvir. If we successfully complete the firstongoing clinical trial in ourHCV Phase 3 program.clinical Wetrials currentlyevaluating the regimen of bemnifosbuvir and ruzasvir and are able to complete and submit the NDA to the FDA on our current projected timeline, we anticipate enrollmentthat ofthis patientsnext topotential commencemilestone inmay become due and payable during the Phasethree 3months programended inJune April30, 2025 and we expect this milestone to become payable in conjunction with such event.2027.

We expect that our net cash used in operating activities will remain significant as we advancecomplete ourthe HCVclinical productdevelopment candidateof throughthe preclinicalregimen of bemnifosbuvir and clinicalruzasvir development,for the treatment of HCV, seek regulatory approval, and prepare for and, if approved, manufacture such product at commercial scale and otherwiseprepare for and, if approved, pursue commercialization activities; advance AT-587, our HEV product candidate through preclinical and clinical development; acquire, discover, validate and develop additional product candidates; obtain, maintain, protect and enforce our intellectual property portfolio; and, if necessary, hire additional personnel. In addition, we may incur additional costs as we continue to operate as a public company. We believe that our available cash, cash equivalents and marketable securities will be sufficient to fund our planned operations intothrough 2028.2027. We have based this estimate on assumptions that may prove to be wrong and we could exhaust our available capital resources sooner than we expect.

We do not have any products approved for sale and have not generated any product revenue since inception. We do not anticipate generating any revenue from product sales for the foreseeable future. Our ability to generate product revenue will depend on the successful development, regulatory approval and eventual commercialization of one or more of our product candidates. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through private or public equity or debt financings, collaborative or other arrangements with third parties, or through other sources of financing. Our failure to meet the primary endpoint of our COVID-19 SUNRISE-3 Phase 3 clinical trial may make such financing more difficult. Adequate funding may not be available to us on acceptable terms, or at all. If we fail to raise capital or enter into such agreements as and when needed, we may have to significantly delay, scale back or discontinue the development and commercialization of our product candidates.

conductcomplete the Phase 3 clinical development of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV;

seek market approval and prepare for potential commercialization of anythe productregimen candidatesof thatbemnifosbuvir weand mayruzasvir successfullyfor developthe treatment of HCV;

Substantially all of our resources are focused on the development of our product candidates. We expect our research and development expenses to vary quarter over quarter particularly as we advancecomplete our Phase 3 HCV clinical programprogram, andmanufacture preparecommercial launch supply for the possible commercialization of the combinationregimen of bemnifosbuvir and ruzasvir ifand advance AT-587 for the Phasetreatment 3of clinical development is successful.HEV. Predicting the timing or cost to complete our clinical programs, validate our commercial manufacturing and supply processes and manufacture of product at commercial scale is difficult and delays may occur because of many factors, including factors outside of our control. For example, if the FDA or other regulatory authorities were to require us to conduct clinical trials beyond those that we currently anticipate or the time to complete planned clinical trials is extended due to delays in enrollment or otherwise, we could be required to expend significant additional financial resources and time on the completion of clinical development. Furthermore, we are unable to predict with any certainty when our HCV and HEV product candidatecandidates or any other product candidate we may develop will, if ever, receive regulatory approval. Early stage activities consist of assessing the antiviral activity and other properties of select compounds derived from our compound library against respiratory and other RNA viral infections.

We have incurred significant operating expenses since our inception. For the threesix months ended MarchJune 31,30, 2026 and the year ended December 31, 2025, our operating expenses were $48.0$83.1 million and $180.9 million, respectively. As of MarchJune 31,30, 2026, we had an accumulated deficit of $568.0$600.9 million.

establish a sales, marketing, internal systemsmarketing and distribution infrastructure and internal systems to commercialize any products for which we may obtain regulatory approval, if any, in geographies in which we plan to commercialize our products ourselves or with collaborators;

Since inception, we have incurred substantial operating expenses. We expect to incur substantial expenses in connection with our current and planned business activities, particularly completing the late stage development of the regimen of bemnifosbuvir and ruzasvir, the manufacture of commercial launchdrug supply, the preparation and submission of an NDA and other similar applications seeking marketing approval for our HCV product candidate. Also, we anticipate that we may incur substantial expenses in connection with the development of AT-587 for the treatment of HEV, and in connection with the discovery, license or other acquisition and potential development of other product candidates, if any. If we successfully develop and receive regulatory approval to market the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV or any other product candidates, we expect we will also incur substantial expenses in connection with the establishment of sales, marketing, internal systems and distribution infrastructure to commercialize such products. Additionally, in 2025, our Board authorized and we completed a share repurchase program expending the total authorized amount of $25.0 million, net of transaction costs and excise taxes, in connection with the repurchase of 7,673,792 shares of our common stock.

the scope, progress, results and costs of our preclinical studies and clinical trials, in particular the completion of our Phase 3 development of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV;

the timing of, and the costs involved in, obtaining marketing approvals for our current and future product candidates in regions where we choose to commercialize any products including for example, our anticipated submission to the FDA of an NDA for marketing approval of our HCV product candidate the regimen of bemnifosbuvir and ruzasvir;

In the future, we may enter into strategic collaborations or other transactions. While we remain open to consideration of a broad range of strategic alternatives, including strategic partnerships, acquisition, merger, or other business combination, sale of assets or other strategic transactions, we believe that it is most likely that actionable alternatives may be available after we receive the results from the currently ongoing HCV Phase 3 clinical program. There is no assurance we will conclude any specific transaction or outcome. If we do identify suitable collaboration candidates or strategic partners, we may not be able to complete such collaborations or other strategic transactions timely or on favorable terms, or at all. Any collaborations or other strategic transactions may not strengthen our competitive position, and these transactions may be viewed negatively by stock research analysts or investors, and we may never realize the anticipated benefits of such transactions. We may decide to issue our common stock or other equity securities to a strategic partner or collaborator which would reduce the percentage ownership of our existing stockholders. In addition, we may not be able to successfully integrate with any collaborator or strategic partner in an effective, timely and non-disruptive manner. Collaborations or other strategic transactions may also divert management attention from day-to-day responsibilities, lead to a loss of key personnel, increase our expenses and reduce our cash and investments available for operations and other uses. We cannot predict the number, timing or size of future collaborations or strategic partnerships or the effect that any such transactions might have on our operating results.

We incurred a net loss of $45.4$78.4 million for the threesix months ended MarchJune 31,30, 2026. Our ability to achieve and sustain future profitability depends upon our ability to generate revenue from product sales. We have not generated product revenue and we do not expect to generate product revenue unless or until we successfully complete clinical development and obtain regulatory approval of, and then successfully commercialize, at least one of our product candidates. Our HCV and HEV product candidates and future product candidates, if any, require additional preclinical and clinical development, regulatory review and approval, substantial investment in and access to sufficient commercial manufacturing capacity and significant marketing efforts before we can generate any revenue from product sales. Currently, we do not anticipate generating revenue from product sales for at least the next few years. Our ability to generate revenue depends on a number of factors, including, but not limited to:

timely completion of our clinical trials, including theC-FORWARD, our HCV Phase 3 clinical trialstrial evaluating the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, and the clinical trials of AT-587 for the treatment of HEV, as well as our preclinical studies and other clinical trials, each of which may be significantly slower or more costly than we currently anticipate and will depend substantially upon the performance of third-party contractors;

our ability to complete additional investigational drug application (“IND”) enabling studies and successfully submit INDs, clinical trial application (“CTAs”) or comparable applications to allow us to initiate clinical trials for AT-587, our HEV product candidate, and any other product candidates;

Our business is highly dependent on the success of our lead product candidate, the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, which requires significant additional clinical testing, principally including successful completion of the C-FORWARD Phase 3 clinical testing,trial, before we can seek regulatory approval and potentially launch commercial sales. If this product candidate fails in clinical development, does not receive regulatory approval or is not successfully commercialized, or is significantly delayed in doing so, our business will be harmed.

During the near term, we expect to devote substantial efforts and financial resources to complete the Phase 3 clinical development of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, manage clinical, medical affairs and manufacturing activities, including the manufacture of commercial launch supply, seek and obtain regulatory approvals in multiple jurisdictions, secure additional sources of manufacturing supply and capacity, build or otherwise access a commercial organization, and engage in significant pre-launch efforts.

We cannot be certain that our HCV product candidate,C-FORWARD, our HEVPhase product3 candidateclinical trial evaluating the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, or any futureclinical producttrial candidatesevaluating AT-587 for the treatment of HEV will be successfulsuccessful. inAdditionally, clinicalwe trials,cannot be certain that the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, AT-587 for the treatment of HEV or future product candidates, if any, we may subsequently develop will receive regulatory approval or be successfully commercialized even if we receive regulatory approval. Further, our development of any product candidate may be delayed or suspended, which may affect our ability to successfully commercialize such product candidate. Additionally, our ability to successfully commercialize a product will also be dependent upon our ability to timely manufacture at commercial scale the quantities of product that will satisfy market demand.

We cannot be certain that, if approved, the safety and efficacy profile of the regimen of bemnifosbuvir and ruzasvir will be consistent with the results observed in clinical trials. If we are not successfulable into successfully complete the clinical development of the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV, if the required regulatory approvals for this product candidate are not obtained, if there are significant delays in completing the development or obtaining approval of this product candidate or in supplying commercial quantities of the regimen of bemnifosbuvir and ruzasvir or any other product, if approved, on an uninterrupted basis, or if we are otherwise not commercially successful, our business, financial condition and results of operations may be materially harmed.

The lengthy regulatory process, as well as the unpredictability ofIf the results of C-FORWARD, our HCV Phase 3 clinical trials,trial, are unfavorable or we are otherwise not able to successfully complete our HCV development program, we may result in our failingfail to obtain regulatory approval to market our HCV product candidate and any future product candidates,candidate, which may seriously harm our business. InUnfavorable addition,results from clinical trials evaluating AT-587 or other product candidates, if any, that we may clinically develop, may result in us being unable to obtain regulatory approval for such product candidate. Further, even if we were to obtain approval, regulatory authorities may approve any of our product candidates for fewer or more limited indications than we request, may impose significant limitations in the form of narrow indications, warnings, or a Risk Evaluation and Mitigation Strategy (“REMS”) or similar risk management measures. Regulatory authorities may not approve the price we intend to charge for products we may develop, may grant approval contingent on the performance of costly post-marketing clinical trials, or may approve a product candidate with a label that does not include the labeling claims necessary or desirable for the successful commercialization of that product candidate. Any of the foregoing scenarios could seriously harm our business.

To date, we have not successfully concluded any late-stage or pivotal clinical trials for any of our product candidates. We cannot guarantee that any of our planned or ongoing clinical trials will be initiated or conducted as planned or completed on schedule, if at all. We also cannot be sure that submission of any future IND or similar application for AT-587 or any future product candidate will result in the FDA or other regulatory authority, as applicable, allowing future clinical trials to begin in a timely manner, if at all. Moreover, even for trials that begin or have begun, issues may arise that could cause regulatory authorities to suspend or terminate such clinical trials.

Any inability to successfully complete C-FORWARD, our Phase 3 clinical trialstrial evaluating the regimen of bemnifosbuvir and ruzasvir for the treatment of HCV or the completion of anyour first-in-human Phase 1 and additional planned clinical trials we may initiate for AT-587, our HEV product candidate or otherwisecandidate, could result in additional costs to us or impair our ability to seek approval for our HCV and HEV product candidate or any future product candidates and ultimately generate revenue from product sales.

Further, conducting clinical trials in foreign countries for our HCV and HEV product candidates or other product candidates, if any, presents additional risks that may delay completion of our clinical trials. These risks include the failure of enrolled patients in foreign countries to adhere to clinical protocol as a result of differences in healthcare services or cultural customs, managing additional administrative burdens associated with foreign regulatory schemes, as well as political and economic risks relevant to such foreign countries. For example, as part of our C-FORWARD HCV Phase 3 clinical trial, clinical trial sites in Ukraine are enrollingparticipating in and have enrolled patients in theC-FORWARD, study.our HCV Phase 3 clinical trial. To the extent that these patients are not able to complete the study or there is a loss of data related to those patients as a result of the ongoing conflict in that area or otherwise, there may be a delay in completing the study or an adverse impact on the results from the study.

In addition, the FDA’s and other regulatory authorities’ policies with respect to clinical trials being conducted outside North America may change and additional government regulations may be enacted. For instance, with very limited exception for certain EU countries and certain clinical trials, the regulatory landscape related to clinical trials in the EU recently evolved. The EU CTR which was adopted in April 2014 and repeals the EU Clinical Trials Directive (“EU Clinical Trials Directive”), became applicable on January 31, 2022. While the EU Clinical Trials Directive required a separate CTA to be submitted in each member state in which the clinical trial takes place, to both the competent national health authority and an independent ethics committee, the CTR introduced a centralized process and only requires the submission of a single application for multi-center trials. The CTR allows sponsors to make a single submission to both the competent authority and an ethics committee in each member state, leading to a single decision per member state. The assessment procedure of the CTA has been harmonized as well, including a joint assessment by all member states concerned, and a separate assessment by each member state with respect to specific requirements related to its own territory, including ethics rules. Each member state’s decision is communicated to the sponsor via the centralized EU portal. Once the CTA is approved, clinical study development may proceed. With very limited exception for certain EU countries and certain clinical trials,trials including our first-in-human clinical trial of AT-587, all CTAs and clinical trials conducted in the EU (including those which are ongoing) are subject to the provisions of the CTR. As a result, the CTAs we have submitted in connection with the conduct of our HCV Phase 3 clinical trial in the EU were prepared in compliance with the CTR requirements. We have limited experience submitting applications under the CTR. If we or our third-party service providers, such as CROs, encounter difficulties or are unable to comply with the CTR requirements our developments plans would be adversely impacted.

Adverse events (“AEs”) or other undesirable side effects caused by our product candidates could cause us, our collaborators, any DSMB for a trial, or regulatory authorities to interrupt, delay or halt clinical trials and could result in a more restrictive label or the delay or denial of regulatory approval by the FDA or other comparable foreign regulatory authorities.

Any regulatory approvals that we may receive for our product candidates will require the submission of reports to regulatory authorities and surveillance to monitor the safety and efficacy of the product candidate, may contain significant limitations related to use restrictions for groups specified by, among other things, age or medical condition, warnings, precautions or contraindications, and may include burdensome post-approval study or risk management requirements. For example, the FDA may require a Risk Evaluation and Mitigation Strategy (“REMS”) in order to approve our product candidates, which could entail requirements for a medication guide, physician training and communication plans or additional elements to ensure safe use, such as restricted distribution methods, patient registries and other risk minimization tools. In addition, if any of our product candidates is approved, it will be subject to ongoing regulatory requirements for manufacturing, labeling, packaging, storage, advertising, promotion, sampling, record-keeping, conduct of post-marketing studies and submission of safety, efficacy, and other post-market information, including both federal and state requirements in the US and requirements of comparable foreign regulatory authorities. Manufacturers and manufacturers’ facilities are required to comply with extensive FDA and comparable foreign regulatory authority requirements, including ensuring that quality control and manufacturing procedures conform to cGMP and similar regulations. As such, we and our CMOs will be subject to continual review and inspections to assess compliance with cGMP and similar requirements and adherence to commitments made in any approved marketing application. Accordingly, we and others with whom we work must continue to expend time, money and effort in all areas of regulatory compliance, including manufacturing, production and quality control.

Our HCV product candidate, if approved, is expected to compete directly or indirectly with existing, currently commercialized products. For example, if we successfully develop and receive marketing approval for our HCV product candidate, we anticipate that we will face competition from currently approved oral antiviral HCV products that are well established and widely accepted by physicians, patients and third-party payors, including products marketed and sold by Gilead Sciences, Inc., Asegua Therapeutics LLC, a wholly owned subsidiary of Gilead Sciences, Inc. and AbbVie Inc. Even if approved and commercialized, our HCV product candidate may fail to achieve market acceptance with hospitals, physicians, patients or third-party payors. Hospitals, physicians, patients or third-party payors may conclude that our product is are less safe or effective or otherwise less attractive than existing drugs. If our HCV product candidate or other future product candidates, if any, do not receive market acceptance for any reason, our revenue potential would be diminished, which would materially adversely affect our ability to become profitable. Other product candidates, if any, may also compete with existing products in a similar manner.

Many of our competitors have substantially greater capital resources, access to larger pools of capital, robust product candidate pipelines, established presence in the market, deep and broad commercial infrastructures and greater expertise in research and development, manufacturing, preclinical and clinical testing, obtaining regulatory approvals and reimbursement and marketing approved products than we do. As a result, our competitors may be able to maintain market share or achieve product commercialization or patent or other intellectual property protection earlier than we can. For example, in each of May 2023 and October 2024, the US Patent and Trademark Office (“USPTO”) granted Gilead Sciences patents in the US that mayinclude coverclaims which purportedly covers our compound bemnifosbuvir. IfWhile we believe the claims in these patents are invalid and unenforceable and will expire not later than June 15, 2028, if Gilead Sciences asserts either of these patents in an infringement suit, we may not be successful in convincing a trial court that the patentclaims isare invalid and unenforceable. In that circumstance, if we were selling or offering to sell the regimen of bemnifosbuvir and ruzasvir prior to the expiration of these Gilead Sciences patents, we would need to obtain a license from Gilead Sciences,Sciences covering the then remaining term of the patents, which may not be available on reasonable terms, if at all. If such a license is required and we are unable to obtainagree suchon license,license commercializationterms, ofa approved product candidates, if any, using bemnifosbuvircourt may notimpose belicense able to continue without infringement,terms, which could result in significant cost orfor preventthe usperiod fromwe may be commercializing bemnifosbuvir or regimens containing bemnifosbuvir such as our HCVthe product candidate.prior to the expiration of the patents held by Gilead Sciences.

Any new export or import restrictions, new legislation or shifting approaches in the enforcement or scope of existing regulations, or changes in global, political, regulatory and economic conditions affecting US trade, manufacturing, development or investment, could result in additional restrictions on our ability to manufacture materials for our research programs, preclinical studies, clinical trials and our manufacture of product for commercialization, if approved, or significantly increase our costs. In recent years, the US has instituted or proposed changes in trade policies that include the negotiation or termination of trade agreements, the imposition of higher tariffs on imports into the US, economic sanctions on individuals, corporations or countries, and other government regulations affecting trade between the US and other countries, in particular China, Mexico, Canada and the EU. A number of other nations have proposed or instituted similar measures directed at trade with the US in response. As a result of these developments, there may be greater restrictions and economic disincentives on international trade that could adversely affect our business. Various tariffs enacted by the US federal government in 2025 have been subject to successful legal challenge,challenge leading to some tariffs being refunded, but itthe remains unclear whether andextent to whom those tariffs may be refunded, andwhich the US federal government may attempt to impose new or similar tariffs under alternative statutory mechanisms.mechanisms remains unclear. For example, recently the administration imposed new tariffs under Section 301 of the Trade Act of 1974. As additional trade-related policies are instituted, we may need to modify our business operations to comply and adapt to such developments, which may be time-consuming and expensive.

For example, in March 2021, fourteen years after its priority date, Gilead Sciences first presented a patent claim to the USPTO that purports to cover bemnifosbuvir. On May 9, 2023, the USPTO issued US Patent No. 11,642,361 (“ ‘361 patent”) with an amended claim (“Claim”) to Gilead Sciences that purports to cover bemnifosbuvir. We believe that the ‘361 patent, if valid and enforceable, will expire inon mid-2028.June 15, 2028. On August 7, 2023, we filed a Post Grant Review Petition with the USPTO Patent Trial and Appeal Board (“PTAB”), challenging the issuance of the Claim to Gilead, on the basis that the Claim is not supported by the written description of the ‘361 patent and that the ‘361 patent does not have an enabling disclosure for the Claim. In February 2024, the PTAB denied to exercise its discretion to institute the post grant proceeding. This denial does not stop us from making the same or similar arguments, or additional arguments, nor from bringing the same or new evidence of invalidity or unenforceability in court if Gilead Sciences files an infringement suit. However, while we believe this Claim is invalid and unenforceable, a trial court or an appellate court may disagree and uphold the Claim of the '361 patent, which would require us, prior to commercialization of a product candidate containing bemnifosbuvir to obtain a license from Gilead Sciences to the ‘361 patent. Such a license may not be available on reasonable terms or at all. If a license is required and we are unable to obtain such license, commercialization of approved product candidates, if any, containing bemnifosbuvir may not be able to continue without infringement which could result in significant cost orduring preventthe usperiod fromwe commercializingcommercialize any such product candidate.prior to the expiration of the ‘361 patent.

On October 22, 2024, seventeen years after its priority date, the USPTO issued US Pat. No. 12,121,529 (“ '529 patent”) to Gilead Sciences with claims that again purport to cover bemnifosbuvir. We believe that the '529 patent will expire inon March 15, 2028. While we believe these claims are also invalid and unenforceable, a trial court or an appellate court may disagree and uphold one or more claims of the '529 patent, which would require us to obtain a license from Gilead Sciences to the '529 patent prior to commercialization of a bemnifosbuvir product candidate. Such a license may not be available on reasonable terms or at all. If a license is required and we are unable to obtain such license, commercialization of approved product candidates, if any, containing bemnifosbuvir may not be able to continue without infringement which could result in significant cost orduring preventthe usperiod fromwe commercializingcommercialize any such product candidate.prior to the expiration of the '529 patent.

Our interpretation of the relevance or the scope of a patent or a pending application may be incorrect, which may negatively impact our ability to market our product candidates. To challenge the validity of a US patent, we would need to initiate an action either in federal court or at the PTABPTAB. asAlternatively, wea havechallenge doneto againstvalidity theof '361a patent.US patent could be brought by us in defense to an allegation of infringement by a third party. An action brought before the PTAB must be timely submitted within nine months of the issuance of the patent we are seeking to challenge unless based on published prior art. In either a PTAB or federal court proceeding, there is no assurance that the PTAB or a court of competent jurisdiction would invalidate the claims of any such US patent or, if a PTAB decision is appealed, that a federal court would uphold a PTAB determination of invalidity. If any third-party patents were held by a court of competent jurisdiction to cover the composition of matter of any of our product candidates, the manufacturing process of any of our product candidates or the method of use for any of our product candidates, the holders of any such patents may be able to block our ability to commercialize such product candidate unless we obtain a license under the applicable patents, which may not be available at all or on commercially reasonable terms, or until such patents expire.

For example, we note that Gilead Sciences obtained the US '361 patent sixteen years after its priority datedate, Gilead Sciences obtained the '361 patent that includes a Claim that purportedly covers bemnifosbuvir. We believe that the '361 patent will expire on June 15, 2028. We requested the PTAB Board to institute a post grant review of this patent and it declined to exercise its discretion to do so. This denial does not stop us from making the same or similar arguments, or additional arguments, nor from bringing the same or new evidence of invalidity or unenforceability in court if Gilead files an infringement suit. While we believe this Claim is invalid and unenforceable, a trial court or an appellate court may disagree and uphold the Claim of the '361 patent, which would require us, prior to commercialization of a bemnifosbuvir product candidate to obtain a license from Gilead Sciences to the ‘361 patent.patent Suchfor athe licensetime mayperiod not be available on reasonable terms or at all. If a license is required andthat we are unablecommercializing to obtain such license, commercialization of approveda product candidates,candidate, if any, containing bemnifosbuvir may not be ableprior to continueexpiration withoutof infringementthe '361 patent or pay a court ordered royalty or other damages which could result in significant cost or prevent us from commercializing such product candidate.cost.

Additionally, on October 22, 2024, seventeen years after its priority date, Gilead Sciences obtained US ‘529 patent with claims that also purport to cover bemnifosbuvir. We believe that the '529 patent will expire on March 15, 2028. While we believe these claims are also invalid and unenforceable, a trial court or an appellate court may disagree and uphold one or more claims of the '529 patent, which would require us to obtain a license from Gilead Sciences to the ‘529 patent.patent Suchfor athe licensetime mayperiod not be available on reasonable terms or at all. If a license is required andthat we are unablecommercializing to obtain such license, commercialization of approveda product candidates,candidate, if any, containing bemnifosbuvir may not be ableprior to continuethe withoutexpiration infringementof the '529 patent or pay a court ordered royalty or other damages which could result in significant cost or prevent us from commercializing such product candidate.cost.

Retaining qualified scientific, clinical and manufacturing personnel as well as recruiting qualified sales and marketing personnel if we elect to establish our own commercial organization will be critical to our success. Our ability to identify, hire and retain additional personnel and, if necessary, replace departed executive officers and key employees may be difficult or costly and may take an extended period of time because of the limited number of individuals in our industry with the breadth of skills and experience required to discover or otherwise identify and develop product candidates and gain regulatory approval of and commercialize products successfully. Competition to hire from this limited pool is intense, and we may be unable to hire, train, retain or effectively incentivize these additional key personnel on acceptable terms given the competition among numerous pharmaceutical and biotechnology companies for similar personnel. We also experience competition for the hiring of scientific and clinical personnel from universities and research institutions. In addition, we rely on consultants and advisors, including scientific and clinical advisors, to assist us in formulating our research and development and commercialization strategy. Our consultants and advisors may be engaged by entities other than us and may have commitments under consulting or advisory contracts with other entities that may limit their availability to us.

We may become subject to conflicting laws and regulations related to sustainability and ESG matters. There are requirements that may require us to incur significant additional costs to comply, including the implementation of significant additional internal controls processes and procedures regarding matters that have not been subject to such controls in the past, and impose increased oversight obligations on our management and board of directors. These and other changes in stakeholder expectations may lead to increased costs as well as scrutiny that could heighten all of the risks identified in this risk factor. Additionally, our suppliers and business partners may be subject to similar expectations, which may augment or create additional risks, including risks that may not be known to us.

We are a late-stage clinical biopharmaceutical company leveraging our deep understanding of antiviral drug development, medicinal chemistry, biochemistry and virology to discover, develop and commercialize novel, orally administered antivirals to treat serious viral diseases. Our current product candidate pipeline includes the regimen of bemnifosbuvir and ruzasvir (“BEM/RZR”) which we believe has the potential to improve the current standard of care (“SOC”) for the treatment of patients with hepatitis C virus (“HCV”) infection and AT-587 which we believe has the potential to be the first direct-acting antiviral (“DAA”) for the treatment of patients, particularly immunocompromised patients, with chronic hepatitis E virus (“HEV”) infection.

The objective of our HCV development program is to improve upon the current SOC by offering bemnifosbuvirthe andfixed-dose ruzasvircombination (“FDC”) regimen of BEM/RZR as a differentiated pan-genotypic protease inhibitor-free, short-duration regimen with a low risk of drug-drug interactions for patients infected with HCV, if successfully developed and approved. We believe that a novelnovel, treatmentshorter regimen that can beduration, easily prescribedprescribable treatment will benefit today’s HCV patient population, which is predominately young (20-49 years old) and non-cirrhotic,non-cirrhotic (80-90% of the US population), and it would be a significant improvement to the current SOC.

Presently, there are no short-course (i.e., eight week) nucleotide inhibitor-based, pan-genotypic HCV treatment regimens. Clinical and nonclinical results from studies we conducted prior to date, including a globalour Phase 23 clinical trial which enrolled 275 HCV infected patients,program have shown that the BEM/RZR regimen of bemnifosbuvir and ruzasvir has high antiviral potency and has been well tolerated. These studies have also shown that the BEM/RZR regimen has a low risk for drug-drug interactions with many commonly prescribed medications including proton pump inhibitors and offers the convenience of being able to be taken with or without food. This is a profile that we believe will offer a significant improvement to the current SOC, if approved.

The global HCV Phase 3 program we are conducting consists of two randomized, open label studies: C-BEYOND which has clinical trial sites in the United States (“US”) and Canada, and C-FORWARD which has clinical trial sites in countries outside of North America. In these Phase 3 trialstrials, we are comparing our regimen of bemnifosbuvir and ruzasvirBEM/RZR to an active comparator, the fixed-dose combination regimen of sofosbuvir and velpatasvir,velpatasvir (“SOF/VEL” marketed in the US under the brand Epclusa®), in patients with chronic HCV infection. We are conducting the Phase 3 program in geographically diverse regions in order to enroll patients with a broad array of HCV genotypes.

C-BEYONDIn isJune fully2026, enrolledwe withannounced overthat we completed enrollment of more than 880 patients,HCV andpatients in C-FORWARD. Currently, we expectanticipate to report the topline results mid-2026.from WeC-FORWARD anticipateearly completingin enrollmentthe first quarter of an additional 880 patients in C-FORWARD in mid-2026 and reporting topline C-FORWARD results at year-end 2026.2027. Pending successful results from these Phase 3 clinical trials,C-FORWARD, we are targeting submission to the USU.S. Food and Drug Administration (“FDA”) of a New Drug Application (“NDA”) for marketing approval in Marchthe second quarter of 2027.

WeIn addition to our clinical development activities, we are executing a focused chemistry, manufacturing and controls (“CMC”) strategy to providemanufacture fixedBEM/RZR dose combination (“FDC”) tablets for the completion of the Phase 3 program, to fulfill NDA requirements and to prepare us for potential launch with sufficient commercial supply for projected initial sales if the regimen of bemnifosbuvir and ruzasvir is approved for marketing.launch.

Given the large number of patients currently infected with HCV, which is reported by the US Center for Disease Control and Prevention to be as many as four million persons in the US,HCV and the incidence of newly reported chronic infections continuing to outpace rates of treatment, we expect that a substantial global market will exist for the foreseeable future. In 2025, global net sales of branded HCV therapeutics known in the US as Epclusa® (including the authorized generic copy of Epclusa®) and Mavyret® exceeded $2.5 billion with the US accounting for approximately 50% of these sales.

AT-587 has demonstrated potent nanomolar antiviral activity against HEV in vitro. In single-dose in vivo nonclinical pharmacokinetic studies, high plasma concentrations of the surrogate to the active intracellular triphosphate metabolite were observed in all animal species tested. Results from in vitro toxicology, pharmacology and drug metabolism and pharmacokinetic studies indicate the potential for a favorable clinical profile for AT-587. Currently,In July 2026, we anticipate initiatinginitiated clinical development of AT-587 within a first-in-human Phase 1 studyclinical trial which is designed to evaluate the safety, tolerability and pharmacokinetics of AT-587 in mid-2026.healthy volunteers.

We believe we are well capitalized to advance our current programs. We had $256.0$219.5 million in cash, cash equivalents and marketable securities at MarchJune 31,30, 2026.

We do not have any products approved for sale and have not generated any product revenue since inception. We do not anticipate generating any revenue from product sales for the foreseeable future. Our ability to generate product revenue will depend on the successful development, regulatory approval and eventual commercialization of one or more of our product candidates. Until such time as we can generate significant revenue from product sales, if ever, we expect to finance our operations through private or public equity or debt financings, collaborative or other arrangements with third parties, or through other sources of financing. Our failure to meet the primary efficacy endpoint of our COVID-19 SUNRISE-3 Phase 3 clinical trial may make such financing more difficult. Adequate funding may not be available to us on acceptable terms, or at all. If we fail to raise capital or enter into such agreements as and when needed, we may have to significantly delay, scale back or discontinue the development and commercialization of our product candidates.

Additionally, in April 2025, our Board authorized a program to repurchase shares of our common stock (“Common Stock”). Under this authorization, we returned capital to our stockholders while maintaining the capacity to complete the Phase 3 clinical development of the regimen of bemnifosbuvir and ruzasvirBEM/RZR and execute on our other strategic business plans. Under the share repurchase program, which was fully completed in 2025, we expended $25.5 million (including transaction costs and excise taxes) in connection with the repurchase of 7,673,792 shares of our Common Stock.

Expecting that the results of our HCV Phase 3 clinical development program, if successful, will drive stockholder value and catalyze business development discussions, in November 2025, we concluded the formal engagement to explore strategic partnerships which we previously entered into with Evercore LLC, a global independent investment bank. Currently,As noted above, in July 2026, we reported topline results of C-BEYOND, our Phase 3 clinical trial, comparing our regimen of BEM/RZR against the regimen of SOF/VEL (marketed in the US under the brand Epclusa®). In C-BEYOND, BEM/RZR demonstrated statistical non-inferiority to SOF/VEL meeting both primary and secondary study endpoints. In addition to C-BEYOND, our HCV Phase 3 clinical development program also includes C-FORWARD, a second Phase 3 clinical trial. Patient enrollment in C-FORWARD was completed in June 2026 and we currently expect to report topline results from ourthis Phase 3 C-Beyondclinical trial early in mid-2026the andfirst toplinequarter resultsof from2027. ourIf PhaseC-FORWARD 3is C-Forwardsuccessfully trialcompleted, atwe year-endare 2026. We remain opentargeting to considerationsubmit an NDA to the FDA in the second quarter of strategic2027 transactionsseeking and all other opportunitiesapproval to drivemarket stockholderthe value.regimen.

In addition to a non-refundable upfront payment that we made in February 2022, we agreed to pay Merck milestone payments upon our achievement of certain development, regulatory and sales-based milestones. Additionally, we will pay Merck tiered royalties based on annual net sales of Products ranging from high single digits to mid-teens percentages. Our royalty payment obligations will continue until the later of (i) the expiration of the last to expire valid claim of a licensed Merck patent claiming such Product and (ii) a period of years after the first commercial sale of such Product in such country. We may terminate the Merck License Agreement for convenience upon prior written notice. The first milestone in the amount of $5.0 million became due and payable in April 2025 when we enrolled our first patient in C-BEYOND, the Phase 3 clinical trial that we are currently conducting in the US and Canada evaluating the regimen of bemnifosbuvir and ruzasvirBEM/RZR for the treatment of HCV. The Company recognized this milestone payment as research and development expense in the three months ended June 30, 2025. The next potential milestone, in the amount of $10.0 million, is payable upon acceptance by the FDA of a new drug application covering a product candidate including ruzasvir. If we successfully complete theC-FORWARD, ongoing HCVour Phase 3 clinical trialstrial, and our HCV development program evaluating the regimenBEM/RZR of bemnifosbuvirregimen, and ruzasvir andwe are able to complete and submit the NDA to the FDA on our current projected timeline, we anticipate that this next potential milestone may become due and payable during the three months endedending JuneSeptember 30, 2027.

As of MarchJune 31,30, 2026, we had cash and investments of $256.0$219.5 million. Net cash used in operating activities was $46.4$83.5 million for the threesix months ended MarchJune 31,30, 2026.

Based on our current plans, we anticipate our existing financial resources will allow us to advance our current and planned clinical programs to and through key inflection points, prepare and submit an application for marketing approval of the regimen of bemnifosbuvir and ruzasvir,BEM/RZR, engage in pre-launch activities including the manufacture of the regimen of bemnifosbuvir and ruzasvir in commercial quantities sufficient to meet our initial sales projections and advance to late-stage clinical development of AT-587 for the treatment of HEV.HEV to late-stage clinical development.

We expect that our net cash used in operating activities will remain significant as we complete the clinical development of the regimen of bemnifosbuvir and ruzasvirBEM/RZR for the treatment of HCV, seek regulatory approval, manufacture such product at commercial scale and prepare for and, if approved, pursue commercialization activities; advance AT-587, our HEV product candidate through preclinical and clinical development; acquire, discover, validate and develop additional product candidates; obtain, maintain, protect and enforce our intellectual property portfolio; and, if necessary, hire additional personnel. In addition, we may incur additional costs as we continue to operate as a public company. We believe that our available cash, cash equivalents and marketable securities will be sufficient to fund our planned operations through 2027. We have based this estimate on assumptions that may prove to be wrong and we could exhaust our available capital resources sooner than we expect.

complete the Phase 3 clinical development of the regimen of bemnifosbuvir and ruzasvirBEM/RZR for the treatment of HCV;

complete non-clinical NDA enabling activities,activities including those associated with the manufacture of the regimen of bemnifosbuvir and ruzasvirBEM/RZR at commercial scale;

seek marketing approval and prepare for potential commercialization of the regimen of bemnifosbuvir and ruzasvirBEM/RZR for the treatment of HCV;

initiateadvance the clinical development of AT-587 for the treatment of chronic HEV;

Substantially all of our resources are focused on the development of our product candidates. We expect our research and development expenses to vary quarter over quarter particularly as we complete our Phase 3 HCV clinical program, manufacturecomplete commercialNDA launchassociated supply for the possible commercialization of the regimen of bemnifosbuvir and ruzasviractivities and advance the clinical development of AT-587 for the treatment of HEV. Predicting the timing or cost to complete our clinical programs, validate our commercial manufacturing and supply processes and manufacture of product at commercial scale is difficult and delays may occur because of many factors, including factors outside of our control. For example, if the FDA or other regulatory authorities were to require us to conduct clinical trials beyond those that we currently anticipate or the time to complete planned clinical trials is extended due to delays in enrollment or otherwise, we could be required to expend significant additional financial resources and time on the completion of clinical development. Furthermore, we are unable to predict with any certainty when our HCV and HEV product candidates or any other product candidate we may develop will, if ever, receive regulatory approval.

Comparison of the Three Months Ended MarchJune 31,30, 2026 and 2025

Research and development expenses increaseddecreased by $11.6$4.1 million from $29.6$32.3 million for the three months ended MarchJune 31,30, 2025 to $41.1$28.2 million for the three months ended MarchJune 31,30, 2026. The net increasedecrease was primarily driven by ana increasedecrease in external spend for our HCV Phase 3 clinical development andoffset by an increase in external spend for HEV preclinical development and clinical development startup activities. The increasedecrease in HCV Phase 3 clinical development external spend was partiallyprincipally offsetthe result of the completion of the Week 24 post treatment visits by lowerpatients in our C-BEYOND Phase 3 clinical trial. The decrease in internal research and development expenses was primarily related to lower salaries and wages and lower stock-based compensation expense in the three months ended MarchJune 31,30, 2026.

General and administrative expenses decreased by $2.6$2.1 million from $9.5$9.1 million for the three months ended MarchJune 31,30, 2025 to $6.9$7.0 million for the three months ended MarchJune 31,30, 2026. The net decrease was primarily related to lower salaries and wages, lower stock-based compensation expense and lower professional fees.

Interest income and other, net, decreased by $2.4$2.2 million for the three months ended MarchJune 31,30, 2026 compared to the three months ended MarchJune 31,30, 2025, primarily due to lower investment balances.

Income tax expense was $0.1 and $0.2 million for the three months ended MarchJune 31,30, 2026 and 2025, respectively.

As of MarchJune 31,30, 2026, we had cash, cash equivalents and marketable securities of $256.0$219.5 million. We believe that our available cash and investments will be sufficient to fund our planned operations through 2027 including the completion of the Phase 3 program evaluating the regimen of bemnifosbuvir and ruzasvirBEM/RZR for the treatment of HCV. We have based this estimate on assumptions that may prove to be wrong and we could exhaust our available capital resources sooner than we expect.

We are party to an amended and restated open market sales agreement ("Sales Agreement") with Jefferies LLC ("Jefferies"), pursuant to which we may from time to time offer and sell shares of our Common Stock for an aggregate offering price of up to $200.0 million, through or to Jefferies, acting as sales agent or principal. We have agreed to pay Jefferies a commission of up to 3.0% of the aggregate gross proceeds from each sale of shares, reimburse legal fees and disbursements and provide Jefferies with customary indemnification and contribution rights. As of MarchJune 31,30, 2026, no shares have been issued under the Sales Agreement. The shares will be offered and sold under the Company's shelf registration statement on Form S-3 declared effective by the SEC on November 19, 2024.

To date, we have not generated any product revenue. We do not expect to generate any product revenue unless and until we obtain regulatory approval of and commercialize any of our product candidates and we do not know when, or if, this will occur. We expect to continue to incur significant expenditures for the foreseeable future as we continue the development of, and seek regulatory approvals for, our product candidates, and prepare for and begin to commercialize any approved products. We are subject to all of the risks typically related to the development of new product candidates, and we may encounter unforeseen expenses, difficulties, complications, delays and other unknown factors that may adversely affect our business. Moreover, we expect to incur additional general and administrative costs, including selling costs, as we continue to operate as a public company and potentially expand our organization to support and otherwise initiate additional activities in preparation for potential commercialization of the regimen of bemnifosbuvir and ruzasvir.BEM/RZR.

the scope, timing, rate of progress and costs of our Phase 3 programprogram, including in particular the completion of our Phase 3 clinical trial, C-FORWARD, evaluating the combination of bemnifosbuvir and ruzasvirBEM/RZR for the treatment of HCV and our other drug discovery efforts, preclinical development activities, laboratory testing and clinical trials for other product candidates including AT-587 for the treatment of HEV;

the outcomescope and terms of our search for strategic collaborations we enter into to strengthen our capabilities to commercialize the regimen of bemnifosbuvir and ruzasvir,BEM/RZR, if approved;

the cost, timing and outcome of preparing for and undergoing regulatory review of our regimen of bemnifosbuvir and ruzasvirBEM/RZR for the treatment of HCV and any other product candidates;

the cost and timing associated with commercializing regimen of bemnifosbuvir and ruzasvirBEM/RZR for the treatment of HCV and any other product candidates, if they receive marketing approval;

Net cash used in operating activities for the threesix months ended MarchJune 31,30, 2026 was $46.4$83.5 million. Cash used in operating activities was primarily due to a net loss of $45.4$78.4 million, accretion of premium and discounts on marketable securities of $0.6$1.1 million, a decrease in accounts payable and accrued expenses and other liabilities of $6.2$11.3 million, partially offset by stock-based compensation expense of $3.7 million and a decrease in prepaid expenses and other assets of $2.0$7.1 million.

Net cash used in operating activities for the threesix months ended MarchJune 31,30, 2025 was $30.6$63.4 million. Cash used in operating activities was primarily due to a net loss of $34.3$71.4 million, accretion of premium and discounts on marketable securities of $1.7$3.1 million, and an increase in other assets of $4.2 million, partially offset by stock-based compensation expense of $7.0$11.6 million andmillion, an increase in accounts payable and accrued expenses of $3.3$1.8 million and a decrease in prepaid expenses and other current assets of $1.7 million.

Net cash provided by investing activities for the threesix months ended MarchJune 31,30, 2026 was $29.7$64.1 million and consisted of sales and maturities of marketable securities of $104.3$172.4 million partially offset by purchases of marketable securities of $74.5$108.4 million.

Net cash provided by investing activities for the threesix months ended MarchJune 31,30, 2025 was $85.6$100.9 million and consisted of sales and maturities of marketable securities of $208.2$324.3 million partially offset by purchases of marketable securities of $122.6$223.4 million.

Net cash provided by financing activities for the threesix months ended MarchJune 31,30, 2026 was $0.3 million and consisted of $0.9 million in proceeds from the exercise of stock options and $0.1 million in proceeds from the issuance of our Common Stock under our employee stock purchase plan (“ESPP”) offset by $0.7 million used in connection with the net settlement of vested restricted stock units.

Net cash used in financing activities for the threesix months ended MarchJune 31,30, 2025 was $0.3$14.4 million and consisted of $0.4stock repurchases of $14.1 million related to theand net settlementissuance of vested restricted stock units of $0.5 million, partially offset by proceeds of $0.1 million from the saleissuance of our Commoncommon Stockstock under our employeeESPP stockof purchase$0.1 plan.million.

There have been no material changes to our contractual obligations during the threesix months ended MarchJune 31,30, 2026 from those previously disclosed in our Annual Report on Form 10-K for the year ended December 31, 2025.