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

We and our collaborators are not permitted to market or promote any products in the United States, Europe, China or other countries before we receive regulatory approval from the FDA or comparable foreign regulatory authorities, and we may never receive such regulatory approval for our current product candidates. We have not submitted aan new drug application (NDA) to the FDA or comparable applications to other regulatory authorities and do not expect to be in a position to do so in the near future.

All our product candidates are in clinical development or in varying stages of nonclinical development. Data supporting our clinical development programs are derived from nonclinical data that support our early stage clinical programs, which will determine whether larger, pivotal studies are appropriate. These pivotal studies are necessary to support regulatory approval, and it may be years before these larger, pivotal studies are completed, if ever.

We do not have any approved products, and we have a history of losses. We expect to continue to incur substantial operating and capital expenditures to advance our current product candidates through clinical development, continue research and discovery efforts to identify potential additional product candidates and seek regulatory approvals for our current and future product candidates. All operations and capital expenditures will be funded from cash on hand, securities offerings, debt financings and payments we may receive from out-licenses, collaborations or other strategic arrangements. Adverse geopolitical and macroeconomic developments, such as potential worsening global economic conditions or economic downturn, ongoing military conflicts, related sanctions, actual and anticipated changes in interest rates, economic inflation and the responses by central banking authorities to control such inflation, and tariffs or the imposition and enforceability of tariffs, trade wars, barriers or restrictions, or threats of such actions and the related uncertainty thereof including uncertainties regarding the ability to obtain refunds for previously paid tariffs that have subsequently been invalidated, could affect our ability to access capital as and when needed.

There is no assurance that we will be successful in raising any necessary additional capital on terms that are acceptable to us, or at all. If we are unable to develop and commercialize any product candidates and generate sufficient revenue or raise capital, we could be forced to reduce staff, delay, scale back or discontinue product development and clinical studies, sacrifice attractiveforego business opportunities, cease operations entirely and sell, or otherwise transfer, all or substantially all of our remaining assets, which would likely have a material adverse impact on our business, results of operations, financial condition and share price.

In October 2023, we entered into the Gilead Collaboration Agreement with Gilead, whereby Gilead exclusively licensed to us its HPI program and NNPI program, while retaining opt-in rights to these programs, and has an option to take an exclusive license, on a program-by-program basis, to all of our other current and future pipeline programs during the collaboration term. In connection with the entry into the Gilead Collaboration Agreement, we and Gilead also entered into a common stock purchase agreement and an investor rights agreement, which were both amended in June 2024. Also in June 2024, we and Gilead subsequently entered into a securities purchase agreement and warrant agreement. In December 2024, Gilead purchased additional shares of our common stock at a premium pursuant to the terms of the common stock purchase agreement, and we amended the Gilead Collaboration Agreement in connection with an updated development plan for 6250. In August 2025, Gilead purchased additional shares of our common stock and warrants to purchase additional shares of our common stock. In December 2025, Gilead exercised its option and took an exclusive license to our HPI program, and in March 2026, Gilead declined to exercise its option to license 4334 or defer its option until completion of Phase 2 studies. Our agreements and relationship with Gilead pose a number of risks, including, but not limited to, the following:

We will be heavily dependent on Gilead for further development and commercialization of the investigational products from the programs that it opts into.into, including our HPI program, and transition of these programs to Gilead could delay these programs' clinical and approval timelines.

The results of nonclinical studies may not be representative of diseasethe product candidates' behavior in a clinical setting and may not be predictive of the outcomes of our clinical studies. In addition, the results of early clinical studies of product candidates may not be predictive of the results of later-stage clinical studies.

insufficient quantities of qualified materials made using current good manufacturing practice (cGMP) for use in clinical studies due to manufacturing challenges, delays or interruptions in the supply chain;

fewer available study sites and academic lab facilities due to changes in government funding of clinical research;

We do not have sufficient facilities or resources to conduct all our anticipated nonclinical and clinical studies internally. As a result, we contract with CROs to conduct a significant portion of the nonclinical and clinical studies required for regulatory approval for our product candidates. Our reliance on CROs reduces our control over these activities but does not relieve us of our responsibilities. For example, we are responsible for ensuring that each of our studies is conducted in accordance with the applicable protocol, legal and regulatory requirements and scientific standards, including, in the case of clinical studies, good clinical practices,CGPs, even if the study is conducted by a CRO. In the event CROs fail to perform their duties in such a fashion or we are unable to retain or continue with CROs on acceptable terms, we may be unable to complete our clinical studies and may fail to obtain regulatory approval for our product candidates.

In addition, these CROs may also have relationships with other entities, some of which may be our competitors. CRO personnel are not our employees, and except for remedies available to us under our agreements with such third parties, we cannot control whether they devote sufficient time and resources to our clinical and nonclinical studies. If these CROs do not successfully carry out their contractual duties or obligations or meet expected deadlines, if they need to be replaced or if the quality or accuracy of the clinical data they obtain is compromised due to the failure to adhere to our clinical protocols, regulatory requirements, including good clinical practices,GCPs, or for other reasons, our research, nonclinical or clinical studies may be extended, delayed or terminated and we may not be able to obtain, or may be delayed in obtaining, regulatory approvals for our product candidates, any of which could materially harm our business, prospects, financial condition and results of operations.

business interruptions resulting from geopolitical actions such as the war between Russia and Ukraine, the conflicts in the Middle East, including the risingrecent hostilities involving Iran, and in Venezuela, tensions between China and Taiwan, as well as tariffs,trade tension and/or the imposition and enforceability of tariffs (including tariffs that have been or may be in the future imposed by the United States and other countries and uncertainties regarding the ability to obtain refunds for previously paid tariffs that have subsequently been invalidated), other wars, acts of terrorism, natural disasters or outbreaks of disease;

differentincreased regulatory requirements for drug approvalsscrutiny or increased scrutinyprohibitions on CROs located in foreign countries, including China;

Changeschanges in trade, economic or other policies by the U.S. or foreign governments, which may result in new or unexpected changes in tariffs, trade wars, barriers or restrictions, or regulatory requirements;

Each of these risks could delay our development efforts, nonclinical studies and clinical studies or the approval, if any, of our product candidates by the FDA or applicable non-U.S. regulatory authorities and the commercialization of our product candidates. Furthermore, workforce reductions in workforce at the FDAFDA, and any future reductions of staffing or other resources at the FDA, may lead to delays in inspecting facilities and, in turn, delayed FDA approvals for manufacturing changes. This could result in higher costs or deprive us of potential product revenues and materially harm our business, financial condition and results of operations.

The clinical and commercial success of our potential products will depend in part on the public and clinical communities’ acceptance of novel classes of product candidates. Moreover, our success depends upon physicians prescribing, and their patients being willing to receive, treatments that involve the use of our product candidates we may develop in lieu of, or in addition to, existing treatments with which they are already familiar and for which more clinical data may be available. Adverse events (AEs) in our nonclinical or clinical studies or those of our competitors or of academic researchers utilizing the same MOA as our product candidates, even if not ultimately attributable to our product candidates, and any resulting publicity could result in increased governmental regulation, larger, more complex, or an increased number of clinical trial requirements, unfavorable public perception, potential regulatory delays in the testing or approval of our product candidates, stricter labeling requirements for our product candidates that are approved, if any, and a decrease in demand for any such products.

Under Sections 382 and 383 of the Internal Revenue Code of 1986, as amended (the Code), a corporation that undergoes an “ownership change” (generally defined as a greater than 50% change (by value) in its equity ownership over a three-year period) is subject to annual limitations on its ability to use its pre-change net operating loss carryforwards and other pre-change tax attributes (such as research tax credits) to offset its post-change income or taxes. We have experienced ownership changes in the past, most recently in August 2025, and future equity issuances may result in additional ownership change. Accordingly, some of our net operating losses or credits could expire unutilized, and our ability to utilize our net operating losses or credits to offset U.S. federal taxable income could be limited, which would result in increased future tax liability to us. We may also be subject to similar limitations at the state level.

Our product candidates are subject to extensive and rigorous domestic government regulation, including regulation by the FDA, the Centers for Medicare and Medicaid Services, other divisions of the U.S. Department of Health and Human Services,Services (HHS), the U.S. Department of Justice, state and local governments, and their respective foreign equivalents. Both before and after approval of any product, we and our collaborators, suppliers, contract manufacturers and clinical investigators are subject to extensive regulation by governmental authorities in the United States and other countries, covering, among other things, testing, manufacturing, quality control, clinical studies, post-marketing studies, labeling, advertising, promotion, distribution, import and export, governmental pricing, price reporting and rebate requirements. Failure to comply with applicable requirements could result in one or more of the following actions: warning or untitled letters; unanticipated expenditures; delays in approval or refusal to approve a product candidate; voluntary or mandatory product recall; product seizure; interruption of manufacturing or clinical studies; operating or marketing restrictions; injunctions; criminal prosecution and civil or criminal penalties, including fines and other monetary penalties; exclusion from federal health care programs such as Medicare and Medicaid; adverse publicity; and disruptions to our business.

The ability of the FDA to review and approve new products canhas been in the past and may in the future be affected by a variety of factors, including government budget and funding levels, authorization and payment of user fees, the ability to hire and retain key personnel, as well as other statutory, regulatory and policy changes. In addition, funding of other government agencies that support research and development activities that pertain to FDA review, such as research to understand new technologies or establish new standards, can shift in response to changing administrative policies and priorities. Such policy shifts, includingincluding, for example, the recent efforts to downsize the federal workforce,workforce removeby jobrestructuring eliminationthe protectionsHHS and eliminating positions at the FDA, including teams critical to the FDA's ability to conduct regular inspections, reviews and other regulatory activities, such as issuing guidance for federal workers, limit certain communications,industry and potentiallyregulations, interfereand withother userfederal fee reauthorization,agencies, may affect the timelines, completeness or duration of the FDA review process. In addition, the HHS may change the user fee reauthorization process andor fail to reauthorize user fee programs. As a result, average review times at the FDA may fluctuatefluctuate, asand athe result.outcome Ifof aany such review process may be impacted. A prolonged government shutdown or a widespread freeze on federal funding occurs,could it couldalso significantly impact the ability of the FDA to timely review and process our regulatory submissions,submissions and the National Institutes of Health to conduct research or provide grants, or cause other agencies that support the FDA to slow their work. In addition, if future legislation or administrative action or changes in FDA policy prevent the FDA or other regulatory authorities from conducting routine inspections, reviews, or other regulatory activities, it could significantly impact the ability of the FDA to timely review and process our regulatory submissions, which could have a material adverse effect on our business. Delays in obtaining regulatory approvals might: delay commercialization of, and our ability to derive product revenues from, our product candidates; impose costly procedures on us; and diminish any competitive advantages that we might otherwise enjoy.

We and our collaborators may be subject, directly or indirectly, to applicable U.S. federal and state anti-kickback, false claims laws, physician payment transparency laws, other fraud and abuse laws or similar healthcare and security laws and regulations, and health information privacy and security laws, which could expose us or them to criminal sanctions, civil penalties, exclusion or suspension from federal and state healthcare programs, contractual damages, reputational harm and diminished profits and future earnings.

Healthcare providers, physicians and others play a primary role in the recommendation and prescription of any products for which we obtain regulatory approval. If we obtain FDA approval for any of our drug candidates and begin commercializing those drugs in the United States, our operations may be subject to various federal and state fraud and abuse laws, including the federal Anti-Kickback Statute, the federal False Claims Act, and physician payment sunshine laws and regulations. Additionally, we are subject to state and non-U.S. equivalents of each of the healthcare laws described above, among others, some of which may be broader in scope and may apply regardless of the payor. These laws may impact, among other things, our proposed sales, marketing and education programs. For example, there are federal and state healthcare laws and regulations that govern prescription drug marketing practices, including off-label promotion, and increased scrutiny of direct-to-consumer advertisements. In addition, we may be subject to patient privacy regulation by both the federal government and the states and foreign jurisdictions in which we conduct our business. If we fail to comply with any applicable federal, state or foreign legal requirement, we could be subject to penalties.

Our employees, independent contractors, consultants, collaborators and CROs may engage in misconduct or other improper activities, including noncompliance with regulatory standards and requirements,requirements for which we may be held responsible and which could result in significant liability for us and harm our reputation.

The price of our common stock mighthas in the past and may continue to fluctuate significantly, and you could lose all or part of your investment.

The price of our common stock fluctuates widely. Continued volatility in the market price of our common stock might prevent a stockholder from being able to sell shares of our common stock at or above the price paid for such shares. The trading price of our common stock has in the past and may continue to be volatile and subject to wide price fluctuations in response to various factors, many of which are beyond our control, such as the progress, results and timing of our clinical and nonclinical studies and other studies involving our product candidates, the success or failure of our product candidates, the receipt or loss of required regulatory approvals for our product candidates, the availability of capital or the other risks discussed in this “Risk Factors” section.

We are a biotechnology company developing innovative therapeutics targeting serious viral diseases with the potential to improve the lives of patients worldwide. Our pipeline includes multiple clinical-stage investigational therapies, including: (1) two long-acting helicase-primase inhibitors (HPI) targetingfor the treatment of recurrent genital herpes; (2) an orally bioavailable hepatitis delta virus (HDV) entry inhibitor; and (3) a highly potent next-generation capsid assembly modulator (CAM) designed to disrupt the replication cycle of hepatitis B virus (HBV) at several key points. Our pipeline also includes a novel, oral broad-spectrum non-nucleoside polymerase inhibitor (NNPI) targetingfor the treatment of transplant-related herpesviruses, which is currently undergoing studies to enable a regulatory filing, and we have additional research programs against multiple antiviral targets. In December 2025, pursuant to our collaboration with Gilead Sciences, Inc. (Gilead and the Gilead Collaboration), Gilead exercised its option to license our HPI program for the treatment of recurrent genital herpes, including our long-acting investigational candidates ABI-1179 (1179) and ABI-5366 (5366). For additional information regarding Gilead’s exercise of its option, see “Collaboration and License Agreement—Gilead Sciences, Inc.—Option Exercise.”

Genital herpes can be caused by either herpes simplex virus type 1 (HSV-1) or herpes simplex virus type 2 (HSV-2). HSV-1 and HSV-2 are acquired by oral or genital contact either during symptomatic or asymptomatic reactivation of the virus. Both viruses replicate in neurons, where they can remain latent for the rest of the individual’s life and periodically reactivate, with the virus spreading, replicating and causing disease in epithelial tissues. Initial infection can be asymptomatic or can be marked by serious symptoms, including painful skin lesions, swelling of lymph nodes and urinary problems that can persist for two to three weeks. While genital herpes can be caused by either HSV-1 or HSV-2, recurrences are more likely to be experienced by individuals infected by HSV-2. Genital herpes recurrence can cause painful genital lesions that can lead to increased transmission and debilitate patients,individuals, and symptoms may become more serious with additional episodes. Additional complications include increased risk of HIV infection, as 30% of HIV infections acquired through sexual transmission are attributable to HSV-2 infection. In addition, people with recurrent genital herpes often experience associated psychosocial impacts, including anxiety, concerns about transmission, depression and social stigma. Immunocompromised patientsindividuals may experience more severe and prolonged symptoms due to increased recurrence rates.

Most people with initial symptomatic genital herpes who are infected with HSV-2 have frequent recurrences, generally between three and 15 per year, includingimpacting over four million people in the United States and France, Germany, Italy and Spain (collectively, the EU4) and the United Kingdom (UK). Currently, there are three antiviral drugs (all nucleoside analogs) that have been approved in the United States and the EU4/UK for the treatment of genital herpes. However, no new drugs have been approved in these regions to treat genital herpes for more than 25 years. In addition to the approved nucleoside analogs, agents such as local anesthetics or analgesics may be used to alleviate local symptoms of minor pain and discomfort.

Nucleoside analogs can be administered as episodic therapy as individual outbreaks arise or daily as chronic suppressive therapy for those with high post-exposure recurrences. However, these agents are only partially effective at controlling the infection or reducing transmission risk. With current nucleoside analog therapies, only one out of three people with recurrent genital herpes with six or more recurrences per year are able to make it through a year of treatment without a recurrence. There are still high titer (greater than 104 HSV-2 DNA copies/mL) shedding episodes under this current standard of care for recurrent genital herpes, which can lead to recurrent episodes and transmission of genital herpes. In addition, nucleoside analogs also carry a high pill burden as a lifelong daily treatment, with doses ranging from one to three times daily. There is also high treatment variability among those taking nucleoside analogs, as many seeking care may not consistently receive suppressive therapy.

Based on the limitations of current therapies, we see a path to advancing the treatment paradigm for people suffering from recurrent genital herpes. To reach that goal, we discovered and arebegan developingthe clinical development of a novel, potent, long-acting HPI for recurrent genital herpes, 5366, which demonstrated low nanomolar potency in vitro against both HSV-1 and HSV-2 clinical isolates and a favorable nonclinical safety profile in the U.S. Food and Drug Administration's (FDA) Good Laboratory Practice (GLP) toxicology studies, with high safety margins and minimal potential for off-target effects.studies. In addition, we arebegan developingdevelopment of a second novel, potent, long-acting HPI for genital herpes, 1179, which was in-licensed to us as part of our collaboration with Gilead. As Gilead has exercised its option to exclusively license our HPI program, including 5366 and 1179, development will be in Gilead’s sole control following completion of the Phase 1a/b studies of 5366 and 1179, which we are managing until they are complete. For additional information regarding the option exercise, see “Collaboration and License Agreements—Gilead Sciences, Inc.—Option Exercise.”

During the first quarter of 2024, we filed a Clinical Trial Application (CTA) to support initiation of a Phase 1a/b clinical study for 5366, which was approved in April 2024, and we dosed our first participant in the Phase 1a portion of this study during the second quarter of 2024.

In addition to 5366, we arehave also advancingbegun the clinical development of 1179, a structurally-differentiated HPI with single digit nanomolar potency against HSV-1 and HSV-2 and a nonclinical PK and safety profile to date that is supportive of a potential long-acting treatment by once-weekly oral administration. We submitted the CTA for a Phase 1a/bthe study of 1179 in September 2024, which was approved in October 2024. We dosed our first participant in the Phase 1a portion of this study during the fourth quarter of 2024.

The World Health Organization (WHO) estimates that 254 million people worldwide are chronically infected with HBV as of 2022, and 1.2 million new infections occur each year. HBV is a leading global cause of chronic liver disease and liver transplants, and the WHO estimates that 1.1 million people died in 2022 from HBV, mostly due to cirrhosis and hepatocellular carcinoma. As of 2022, ofOf the 254 million people living with chronic HBV infection, only approximately 33 million, or 13%, were aware of their infection, and only approximately 7 million, or 3%, of those diagnosed received treatment. HBV is a highly prevalent disease that infects almost three times the number of people infected with hepatitis C virus and HIV infections combined, according to the WHO.

HDV is a “satellite virus” of HBV because it can only infect people (1) who are already infected with HBV or (2) at the same time as a person is infected with HBV. HDV affects a subset of approximately 12 to 72 million HBV infected people. These individuals infected with HDV, which comprise an estimated 4.5% of hepatitis B surface antigen (HBsAg) positive individuals, experience a substantially increased disease burden, as they account for 18% of cirrhosis and 20% of hepatocellular carcinoma associated with HBV. HDV is considered the most severe form of hepatitis, as 70% of individuals infected with HDV progress to cirrhosis within ten years. While HDV is less prevalent in the United States, it is a significant and serious health problem with inadequate treatment in many parts of Europe, Africa, the Middle East, East Asia and parts of South America. HDV may be significantly underdiagnosed, because there were no HDV-targeted therapies approved until very recently, and the first therapy approved is only approved in Europe.European Union (EU), Australia and Canada. HDV is known to accelerate disease progression and increase the incidence of liver cirrhosis and liver cancer, which results in higher morbidity and mortality rates than HBV alone.

The current standard of care treatment for HDV is off-label pegylated interferon-α (IFN-α) injected weekly or, in Europe,the EU, Australia and Canada, a large, complex peptide inhibitor that requires daily injections, bulevirtide. There are no approved HDV treatments in the United States, and the large, complex peptide blocker is the only approved HDV treatment in the Europe.States. We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for people living with HDV, who face a significant and immediate disease burden.

The inhibition of HBV and HDV infection by molecules that bind NTCP has been demonstrated in vitro, in animal models and clinically. Notably, bulevirtide, a peptide blocker of NTCP, is the only approved therapy for HDV (approved in Europe).HDV. 6250 useshas the same clinically-validated MOA as bulevirtide. The binding of NTCP-targeted HBV/HDV entry inhibitors to NTCP has also been shown to inhibit the transport of certain bile acids into cells, which results in plasma elevations of bile acids; this effect has been well-tolerated clinically and may serve as a biomarker of pharmacologically active concentrations of drug in the plasma. In nonclinical studies in non-human primates, clinically-relevant doses of 6250 elevated bile acids to levels similar to those seen in humans with bulevirtide.

As a next-generation CAM, 4334 was optimized to potently disrupt viral replication (MOA #1) and prevent the establishment and replenishment of new cccDNA (MOA #2). In contrast, while active against MOA #1, first-generation CAMs have not demonstrated adequate potency to sufficiently block cccDNA formation (MOA #2).2. Further, the current standard of care, NrtIs, impacts the viral life cycle after establishment of cccDNA and can only inhibit production of new viral particles, and it does so incompletely. The chemical scaffold of 4334 is novel and distinct from all our prior CAM candidates.

A Phase 1a study demonstrated that 4334 was well-tolerated when administered orally as single or multiple doses. In addition, the PK data support 4334 as a once daily oral therapy and predicts best-in-class activity against both MOA #1 and MOA #2. During the second quarter of 2024, we dosed our first participant in a Phase 1b clinical study of 4334. We reported interim clinical results from the initial 150 mg cohort in December 2024, whichand topline clinical results including a subsequent 400 mg cohort in June 2025. In both the 150 mg and 400 mg cohorts, 4334 continued to show a half-life supportive of once-daily oral dosing. In addition, results for both cohorts indicated that 4334 maintained clinical exposures multiple folds above those anticipated to be required for potent viral activity and inhibition of cccDNA formation. AMean mean declinedeclines in HBV DNA of 2.9 log10 IU/mL wasand 3.2 log10 IU/mL were observed over 28 days in a population of predominately HBeAg negative participants.participants receiving 150 mg and 400 mg, respectively. Among the subset of participants with detectable HBV RNA at baseline, a mean declinedeclines of 2.5 log10 U/mL forand HBV2.3 RNAlog10 wasU/mL observed.were observed over 28 days in the participants receiving 150 mg and 400 mg, respectively. As anticipated, limited changes in viral antigens were observed for the study population over the 28-day treatment period. These initial antiviral data are consistent with the high potency seen preclinically for 4334. The interim safety data also demonstrated that 4334 was well-tolerated with a favorable safety profile observed. Enrollment is ongoing for the second cohort, evaluating an oral once-daily 400 mg dose of 4334. Based on the strong antiviral activity observed in the first cohort, we expect that theThe 400 mg cohort will bewas the final cohort for this Phase 1b study.study Weand anticipate releasingfinal data fromwas presented at the 400American mgAssociation cohortfor the Study of Liver Disease, The Liver Meeting® in theNovember first2025. halfThe completion of 2025.the Phase 1b study of 4334 constitutes an option triggering point under the terms of the Gilead Collaboration Agreement, as defined below under "Collaboration and License Agreement — Gilead Sciences, Inc."

In a transplant setting, when patients are experiencing immunosuppression, they are at high risk of uncontrolled viral replication and severe disease brought on by one or more herpesviruses, including cytomegalovirus (CMV), HSV-1, HSV-2, varicella zoster virus (VZV) and Epstein-Barr virus (EBV). Each of these herpesviruses are highly prevalent, as approximately (1) 60% of transplant patients are CMV-positive; (2) 60% of transplant patients are HSV-positive; (3) 80% of transplant patients are VZV-positive and (4) 45% of transplant patients are EBV-positive. These viruses establish lifelong latent infections and frequently reactivate in transplant patients due to the use of immunosuppressive drugs following transplantation. These uncontrolled viralherpesvirus infections increase the risk of severe disease and serious complications, including organ rejection, graft loss and death, and impacted approximately 95,000 people receiving transplants in 2021 in the United States and Europe.

In December 2024, we nominated 74237423, a prodrug, as our development candidate to undergo CTA-enablingregulatory studies,filing-enabling studies. In October 2025, we transitioned our discovery and development from 7423 to its parent molecule, 7272, which areis ongoing.currently in regulatory filing-enabling nonclinical studies.

In addition to our investigational therapy programs that have nominated development candidates and have advanced into clinical studies or CTA-enablingregulatory-filing enabling studies, our research team continues to actively focus on proprietary research to discover and developnominate novel antivirals to treat serious viral diseases.

In October 2023, we entered into an Option, License and Collaboration agreement (the Gilead Collaboration Agreement) with Gilead pursuant to which Gilead (1) exclusively licensed to us its HPI program and its NNPI program, while retaining opt-in rights to these programsprograms, and (2) has an option to take an exclusive license, on a program-by-program basis, to all of our other current and future pipeline programs. During the 12-year collaboration term (subject to payment of certain extension fees) and for a specified period thereafter, Gilead may exercise its opt-in rights, on a program-by-program basis, at one of two timepoints—completion of a certain Phase 1 study oror, upon payment of a deferral fee and completion of a certain Phase 2 study for the first product within the program—upon payment of an opt-in fee ranging from $45.0 million to $125.0 million per program depending on the type of program and when the option is exercised. Pursuant to the Gilead Collaboration Agreement, Gilead made an $84.8 million upfront cash payment to us. In December 2024, we and Gilead entered into the First Amendment to the Gilead Collaboration Agreement, which restructured the timing of specific options exercisable and the fees payable to us under the terms of the Gilead Collaboration Agreement due to an agreed upon development plan for 6250. To facilitate this development plan, (1) we received a payment of $10.0 million from Gilead and (2) the opt-in fee payable by Gilead in connection with 6250 was restructured, though it remains in the range of opt-in fees detailed above. The $10.0 million payment received in connection with the First Amendment to the Gilead Collaboration Agreement is creditable towards future collaboration-related payments payable by Gilead. This credit was applied toward Gilead’s opt-in fee paid for the HPI program in December 2025.

If Gilead exercises its opt-in right to any current or future program under the collaboration, we are eligible to receive up to $330.0 million in potential regulatory and commercial milestones on that program, in addition to royalties ranging from the high single-digits to high teens, depending on the clinical stage of the program at the time of the opt-in. Following Gilead’s exercise of its option for each program, we may opt inopt-in to cover 40% of the research and development costs in the United States and share 40% of the profits and operating loss in the United States for products within the program in lieu of receiving milestones and royalties for that program in the United States, unless we later opt out of the cost/profit share for the program. Prior to Gilead’s potential exercise of its opt-in, we are primarily responsible for all discovery, research and development on both our programs and the two Gilead-contributed programs. Following Gilead’s opt-in, Gilead will control the further discovery, research, development,development and commercialization on any optioned programs.programs, and is responsible for all related costs unless we opt in to share 40% of all costs and profits in the United States. During the term, Gilead will continue to support the collaboration through extension fees of $75.0 million in each of the third, fifth and seventh yearsanniversaries of the collaboration.

In October 2023, we entered into the Gilead Collaboration Agreement with Gilead, whereby Gilead exclusively licensed to us its HPI program and NNPI program, while retaining opt-in rights to these programs, and has an option to take an exclusive license, on a program-by-program basis, to all of our other current and future pipeline programs during the collaboration term. In connection with the entry into the Gilead Collaboration Agreement, we and Gilead also entered into a common stock purchase agreement and an investor rights agreement, which were both amended in June 2024. Also in June 2024, we and Gilead subsequently entered into a securities purchase agreement and warrant agreement. In December 2024, Gilead purchased additional shares of our common stock at a premium pursuant to the terms of the common stock purchase agreement, and we amended the Gilead Collaboration Agreement in connection with an updated development plan for 6250. In August 2025, Gilead purchased additional shares of our common stock and warrants to purchase additional shares of our common stock, and in May 2026, Gilead purchased additional shares of our common stock. In December 2025, Gilead exercised its option and took an exclusive license to our HPI program, and in March 2026, Gilead declined to exercise its option to license 4334 or defer its option until completion of Phase 2 studies. Our agreements and relationship with Gilead pose a number of risks, including, but not limited to, the following:

Gilead has the right to designate (and has designated) two directors for appointment to our board of directors pursuant to the terms of the investor rights agreement and ownsowned approximately 28%25.1% of our outstanding common stock.stock as of June 30, 2026. Gilead also has the right to acquire additional shares in the open market, up to an amount resulting in Gilead owning a total of 35% of our outstanding common stock. As a result, Gilead may be able to exert significant influence over us.

business interruptions resulting from geopolitical actions such as the war between Russia and Ukraine, the conflicts in the Middle East, including the recent hostilities involving Iran, and in Venezuela, tensions between China and Taiwan, as well as trade tension and/or the imposition and enforceability of tariffs (including tariffs that have been or may be in the future imposed by the United States and other countries and uncertainties regarding the ability to obtain refunds for previously paid tariffs that have subsequently been invalidated), other wars, acts of terrorism, natural disasters or outbreaks of disease;

The pharmaceutical and biotechnology industries are intensely competitive. In addition, the clinical and commercial landscapes for recurrent genital herpes, HDV, CLD, HBV and transplant-related herpesviruses are rapidly changing; we expect new data from commercial and clinical-stage products to continue to emerge. We compete with organizations, some with significantly more resources, who are developing competitive product candidates. If our competitors develop effective treatments for recurrent genital herpes, HDV, CLD, HBV and transplant-related herpesviruses or any other indication or field we might pursue, and successfully commercialize those treatments, our business and prospects could be materially harmed.

We are a biotechnology company developing innovative therapeutics targeting serious viral and liver diseases with the potential to improve the lives of patients worldwide. Our pipeline includes multiple clinical-stage investigational therapies, including: (1) two long-acting helicase-primase inhibitors (HPI) for the treatment of recurrent genital herpes, ABI-5366GS-5366 (5366) and ABI-1179GS-1179 (1179), which have been exclusively licensed to Gilead Sciences, Inc. (Gilead); (2) an orally bioavailable sodium taurocholate co-transporting peptide (NTCP) inhibitor, ABI-6250 (6250), for the treatment of (a) chronic hepatitis delta virus (HDV) entryinfection inhibitor, ABI-6250and (6250b) primary biliary cholangitis (PBC) and primary sclerosing cholangitis (PSC), both cholestatic liver diseases (CLD); and (3) a highly potent next-generation capsid assembly modulator (CAM) designed to disrupt the replication cycle of hepatitis B virus (HBV) at several key points, ABI-4334 (4334). Our pipeline also includes a novel, oral broad-spectrum non-nucleoside polymerase inhibitor (NNPI) for the treatment of transplant-related herpesviruses, ABI-7272 (7272), which is currently undergoing studies to enable a regulatory filing, and we have additional research programs against multiple antiviralviral and liver disease targets. In December 2025, pursuant to our collaboration with Gilead Sciences, Inc. (Gilead and the Gilead Collaboration), Gilead exercised its option to license our HPI program for the treatment of recurrent genital herpes, including our long-acting investigational candidates 1179 and 5366. For additional information regarding Gilead’s exercise of its option, see “Collaboration and License Agreement—Gilead Sciences, Inc.—Option Exercise.”

6250HDV – All participants in the Phase 1a study have completed dosing and follow up. Chronic toxicology studies have been completed, establishing supportPreparation for anticipateda Phase 2 doses. Preparation for Phase 2 clinical studiesstudy is on-going, with initiation expected in the fourth quarter of 2026.

4334 – InitiatedContinuing process to identify potential partners that was initiated in the first quarter; we do not plan to advance 4334 further without a partner.

Based on the limitations of current therapies, we see a path to advancing the treatment paradigm for people suffering from recurrent genital herpes. To reach that goal, we discovered and began the clinical development of a novel, potent, long-acting HPI for recurrent genital herpes, 5366, which demonstrated low nanomolar potency in vitro against both HSV-1 and HSV-2 clinical isolates and a favorable nonclinical safety profile in the U.S. Food and Drug Administration's (FDA)FDA's Good Laboratory Practice (GLP) toxicology studies. In addition, we began development of a second novel, potent, long-acting HPI for genital herpes, 1179, which was in-licensed to us as part of our collaboration with Gilead. As Gilead has exercised its option to exclusively license our HPI program, including 5366 and 1179, development willis benow in Gilead’s sole control following completion of the Phase 1a/b studies of 5366 and 1179, which we are managing until they are complete.1179. For additional information regarding the option exercise, see “Collaboration and License Agreements—Gilead Sciences, Inc.—Option Exercise.”

We reported interim data from the Phase 1b portion of the 5366 study in August 2025, focused on two different oral doses of 5366 administered on a once-weekly basis. For the powered antiviral endpoint, HSV-2 shedding rate, highly potent antiviral activity was observed with a 94% reduction compared to placebo (p<0.01) over the 29-day evaluation period in the cohort evaluating a 350 mg weekly dose. This reduction exceeded our target for the study of an 80-85% reduction in the rate of HSV-2 shedding. For a secondary clinical endpoint of virologically confirmed genital lesion rate, a 94%97% reduction compared to placebo (p<0.010.05) was observed with the 350 mg weekly dose. The rate of genital swabs with high viral load (i.e., >104 copies/mL HSV DNA), a potential surrogate for HSV-2 transmission and a secondary endpoint, was reduced by 98% compared to placebo (p<0.05) in this cohort.

All participants in the Phase 1b portion of the 5366 study have completed dosing and follow up. The observed PK profile continues to support once-weekly dosing and the potential for once-monthly oral dosing regimens. Additionally, all chronic toxicology studies have been completed. With these data, 5366 is ready to move into a Phase 2 clinical study.study; however, 5366 development is in Gilead's sole control and Gilead does not intend to develop 5366 further at this time.

The 5366 data reported in August and December 2025 waswere presented in an oral presentation and two poster presentations at the Congress of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) in Munich, Germany in April 2026.

InWe additionalso toconducted 5366,a Phase 1a/b clinical study of 1179, a structurally-differentiated HPIHPI, withwhich has single digit nanomolar potency against HSV-1 and HSV-2 and a nonclinical PK and safety profile to date that is supportive of a potential long-acting treatment by once-weekly oral administration is also in clinical development.administration. We reported interim data from two oral weekly dose cohorts in the Phase 1b portion of the 1179 study in December 2025. For the powered antiviral endpoint, HSV-2 shedding rate, highly potent antiviral activity was observed with a 98% reduction in HSV-2 shedding rate compared to placebo (p<0.01) over the 29-day evaluation period in the 50 mg weekly dose cohort. This reduction exceeded our target for the study of an 80-85% reduction in HSV-2 shedding rate. Further, data revealed a 91% reduction in virologically confirmed lesion rate compared to placebo (p<0.01) with the 50 mg weekly dose. There was also a >99% reduction in the number of samples with high viral load, a potential surrogate for HSV-2 transmission and a secondary endpoint.

All participants in the Phase 1b portion of the 1179 study have completed dosing and follow up. With these data, 1179 can move directly into a Phase 2 enabling studiesstudy for a once-weekly treatment regimen, subject to the completion of chronic toxicology studies, which are underway. The 1179 data reported in December 2025 was presented in a poster presentation at ESCMID in April 2026.

In December 2025, Gilead exercised its option early to license our HPI program for the treatment of recurrent genital herpes, including 5366 and 1179. We expect to receivereceived Gilead’s clinical development plan and budget for the HPI program andin makeJune our2026. The plan indicates that 1179 has been selected to advance, with a Phase 2 clinical study in participants with recurrent genital herpes expected to initiate by the end of 2026. Gilead is also considering the possible evaluation of 1179 as part of a combination strategy with HIV PrEP. Our decision regarding the Profit-Share (as defined below) bywill mid-2026.be Wemade anticipateafter Gileadreceipt and review of Gilead's commercial cost estimates, which will initiate a Phase 2 clinical study forcomplete the HPIopt-in program in 2026.package. For more information regarding Gilead’s exercise of its option, see “Collaboration and License Agreement—Gilead Sciences, Inc.—Option Exercise.”

Our HBVLiver and HDVDisease Programs

The World Health Organization (WHO) estimates that 254240 million people worldwide arewere chronically infected with HBV as of 2022,2024, and 1.20.9 million new infections occur each year. HBV is a leading global cause of chronic liver disease and liver transplants, and the WHO estimates that 1.1 million people died in 20222024 from HBV, mostly due to cirrhosis and hepatocellular carcinoma.carcinoma (primary liver cancer). Of the 254240 million people living with chronic HBV infection, only approximately 3365 million, or 13%,27%, were aware of their infection, and only approximately 710 million, or 3%,4%, of those diagnosed received treatment. HBV is a highly prevalent disease that infects almost three times the number of people infected with hepatitis C virus and HIV infections combined, according to the WHO.

HDV is a “satellite virus” of HBV because it can only infect people (1) who are already infected with HBV or (2) at the same time as a person is infected with HBV. HDV affects a subset of approximately 12 to 72 million HBV infected people. These individuals infected with HDV, which comprise an estimated 4.5%nearly 5% of hepatitis B surface antigen (HBsAg) positive individuals, experience a substantially increased disease burden, as they account for 18% of cirrhosis and 20% of hepatocellular carcinoma associated with HBV. HDV is considered the most severe form of hepatitis, as 70% of individuals infected with HDV progress to cirrhosis within ten years. While HDV is less prevalent in the United States, it is a significant and serious health problem with inadequate treatment in many parts of Europe, Africa, the Middle East, East Asia and parts of South America. HDV may be significantly underdiagnosed, because there were no HDV-targeted therapies approved until very recently, and the first HDV-targeted therapy approved is only approved in the European Economic Area (EEA), the UK, Switzerland, AustraliaAustralia, Canada and Canada.the United States. HDV is known to accelerate disease progression and increase the incidence of liver cirrhosis and liver cancer, which results in higher morbidity and mortality rates than HBV alone.

The current standard of care treatment for HDV is off-label pegylated interferon-α (IFN-α) injected weekly or, in the EEA, the UK, Switzerland, AustraliaAustralia, Canada and Canada,the United States, a large, complex peptide inhibitor that requires daily injections, bulevirtide. There are no approved HDV treatments in the United States. We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for people living with HDV, who face a significant and immediate disease burden.

HDV is a small RNA virus that encodes just two viral proteins and relies on host enzymes as well as the HBsAg from HBV to replicate, which limits the number of HDV-specific antiviral targets. Similar to HBV, HDV utilizes HBsAg to enter hepatocytes by binding the cellular transmembrane proteinprotein, sodium taurocholate co-transporting peptide (NTCP).NTCP. NTCP is highly expressed on human hepatocytes, where it serves as one of several proteins involved in the transport of bile acids. The binding of specific small or large molecules to NTCP has been shown to effectively inhibit the interaction of HBsAg with NTCP, which prevents HBV and HDV from infecting hepatocytes.

The inhibition of HBV and HDV infection by molecules that bind NTCP has been demonstrated in vitro, in animal models and clinically. Notably, bulevirtide, a peptide inhibitor of NTCP, is the only approved therapy for HDV. 6250 has the same clinically-validated MOA as bulevirtide. The binding of NTCP-targeted HBV/HDV entry inhibitors to NTCP has also been shown to inhibit the transport of certain bile acids into cells, which results in plasma elevations of bile acids; this effect has been well-tolerated clinically and may serve as a biomarker of pharmacologically active concentrations of drug in the plasma.

A Phase 1aTop-line clinical studydata, of 6250 was initiated in the fourth quarter of 2024, and in August 2025, we announced interimincluding PK, biomarker and safety data fromfor single-ascendingthe andPhase multiple-ascending1a dosesstudy of 6250 was presented at the European Association for the Study of the Liver Congress that took place in Barcelona, Spain in May 2026. Across all cohorts in healthy participants. Across the cohorts evaluated to date,, a mean half-life of approximately four days was observed for 6250 when dosed orally, supporting the once-daily oral dosing profile target. Given this half-life, accumulation was observed in the multiple-dose cohorts with exposures on the last day of dosing generally reaching six- to seven-foldeight-fold higher than the exposure seen after the first dose.

One Grade 2 alanine transminase (ALT) elevation was observed in the cohort evaluating the highest single-dose level of 25 mg. In this cohort, off-target engagement of other liver transporters was also seen as indicated by elevated CP-1 levels. Grade 1 ALT elevations were observed at a low frequency across the other cohorts.cohorts, including placebo. All ALT elevations were self-limited, and none were accompanied with elevations in bilirubin or other markers of liver injury. The elevations resolved in the study period with ongoing drug exposure due to 6250's four-day half-life.

All participants in the Phase 1a study have completed dosing and follow up. The chronic toxicology studies to enable longer term dosing are complete, and we are preparing for Phase 2 clinical studies, with Phase 2 initiation expected in the fourth quarter of 2026. In addition, we expect to initiate additional Phase 1 pharmacology studies to support labeling anticipated to start in the fourth quarter of 2026.

A Phase 1a study demonstrated that 4334 was well-tolerated when administered orally as single or multiple doses. During the second quarter of 2024, we dosed our first participant in a Phase 1b clinical study of 4334. We reported interim clinical results from the initial 150 mg cohort in December 2024, and topline clinical resultsresults, including a subsequent 400 mg cohort in June 2025. In both the 150 mg and 400 mg cohorts, 4334 continued to show a half-life supportive of once-daily oral dosing. In addition, results for both cohorts indicated that 4334 maintained clinical exposures multiple folds above those anticipated to be required for potent viral activity and inhibition of cccDNA formation. Mean declines in HBV DNA of 2.9 log10 IU/mL and 3.2 log10 IU/mL were observed over 28 days in a population of predominately HBeAg negative participants receiving 150 mg and 400 mg, respectively. Among the subset of participants with detectable HBV RNA at baseline, mean declines of 2.5 log10 U/mL and 2.3 log10 U/mL were observed over 28 days in the participants receiving 150 mg and 400 mg, respectively. As anticipated, limited changes in viral antigens were observed for the study population over the 28-day treatment period. These antiviral data are consistent with the high potency seen preclinically for 4334. The safety data also demonstrated that 4334 was well-tolerated with a favorable safety profile observed. The 400 mg cohort was the final cohort for this Phase 1b study and final data was presented at the American Association for the Study of Liver Disease, The Liver Meeting® in November 2025.

In March 2026, Gilead declined to either exercise its option to license 4334 or defer its option until completion of Phase 2 studies. As a result, we retain full control of 4334, including the right to evaluate partnering opportunities for 4334 outside of the Gilead Collaboration. We are actively evaluating partnering opportunities for 4334 and have initiated a process to find potential partners. We do not plan to advance 4334 further without a partner.

In addition to our investigational therapy programs that have nominated development candidates and have advanced into clinical studies or regulatory-filing enabling studies, our research team continues to actively focus on proprietary research to discover and nominate novel antiviralsmolecules to treat serious viral and liver diseases.

In October 2023, we entered into an Option, License and Collaboration agreement (the Gilead Collaboration Agreement) with Gilead pursuant to which Gilead (1) exclusively licensed to us its HPI program and its NNPI program, while retaining opt-in rights to these programs, and (2) has an option to take an exclusive license, on a program-by-program basis, to all of our other current and future pipeline programs. During the 12-year collaboration term (subject to payment of certain extension fees) and for a specified period thereafter, Gilead may exercise its opt-in rights, on a program-by-program basis, at one of two timepoints—completion of a certain Phase 1 study or, upon payment of a deferral fee and completion of a certain Phase 2 study for the first product within the program—upon payment of an opt-in fee ranging from $45.0 million to $125.0 million per program depending on the type of program and when the option is exercised. Pursuant to the Gilead Collaboration Agreement, Gilead made an $84.8 million upfront cash payment to us. In December 2024, we and Gilead entered into the First Amendment to the Gilead Collaboration Agreement, which restructured the timing of specific options exercisable and the fees payable to us under the terms of the Gilead Collaboration Agreement due to an agreed upon development plan for 6250. To facilitate this development plan, (1) we received a payment of $10.0 million from Gilead and (2) the opt-in fee payable by Gilead in connection with 6250 was restructured, though it remains in the range of opt-in fees detailed above. The $10.0 million payment received in connection with the First Amendment to the Gilead Collaboration Agreement iswas creditable towards future collaboration-related payments payable by Gilead.Gilead This creditand was applied toward Gilead’s opt-in fee paid for the HPI program in December 2025.

As of MarchJune 31,30, 2026, Gilead held (1) approximately 28.4%25.1% of our outstanding common stock, (2) a warrant to purchase up to 179,500 shares of our common stock at a price of $17.00 per share, which was acquired in a financing transaction in 2024 (the 2024 Warrant), (3) a Class A warrant to purchase up to 1,147,960 shares of our common stock at a price of $21.60 per share (Class A Warrant), which was acquired in a financing transaction in 2025 (the 2025 Financing) and (4) a Class B Warrant to purchase up to 1,147,960 shares of our common stock at a price of $21.60 per share (Class B Warrant), which was also acquired in the 2025 Financing. The 2024 Warrant is exercisable and expires on June 18, 2029. The Class A Warrant is also exercisable and expires on or prior to the earlier of (a) August 11, 2030 (five years from the date of issuance) and (b) the date that is 30 days after the public announcement that we have completed enrollment of at least 200 patients for our Phase 2 clinical study evaluating 5366 versus valacyclovir. The Class B Warrant is exercisable between November 15, 2026 and December 31, 2026, provided that if, prior to November 15, 2026, we publicly announce that we have received at least $75.0 million in the aggregate of non-dilutive capital in connection with a collaboration agreement, then the Class B Warrant automatically terminates in full.

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

Collaboration revenue was $8.2$13.4 million for the three months ended MarchJune 31,30, 2026 compared to $9.4$9.6 million for the same period in 2025. The $1.2$3.7 million decreaseincrease reflects the timing of activities performed and progress toward completion of services under the Gilead Collaboration Agreement.Agreement, and includes a $5.1 million cumulative catch-up adjustment recognized during the three months ended June 30, 2026 related to updated estimates of future activities under the collaboration.

Research and development expenses consist primarily of employee-related expenses, fees paid to contract resourceresearch organizations and contract manufacturing organizations, lab supplies and other third-party expenses that support our research and discovery, nonclinical and clinical activities. External program costs represent a significant portion of our research and development expenses, which we track by product candidate once it has been nominated. We use our employee and infrastructure resources, as well as certain third-party costs, across multiple research and development programs, and we do not specifically allocate these costs to our programs.

Research and development expenses remained flat atwere $14.9 million for both the three months ended MarchJune 31,30, 2026 andcompared to $16.1 million for the same period in 2025. Employee-relatedThe expenses$1.2 increasedmillion due to higher headcount, annual salary adjustments, and stock-based compensation expense associated with performance-based restricted stock units granted in mid-2025. This increasedecrease was partiallyprimarily offsetdriven by lower external program expenses, whichparticularly mostlyfor decreased5366, due toreflecting the completion of clinical trials,trials and lower manufacturing and toxicology study costs, partially offset by increases in our research and discovery efforts.efforts and higher employee-related expenses due to increased headcount, annual salary adjustments and stock-based compensation expense related to performance-based restricted stock units granted in mid-2025.

General and administrative expenses were $4.7$4.8 million for the three months ended MarchJune 31,30, 2026 compared to $4.5$4.6 million for the same period in 2025. The $0.2 million increase was primarily driven by an increase inhigher stock-based compensation expense associated with performance-based restricted stock units granted in mid-2025.mid-2025, partially offset by lower professional fees related to patent filings.

Interest and other income, net was $2.3$2.5 million for the three months ended MarchJune 31,30, 2026, compared to $1.1$0.9 million for the same period in 2025. The $1.2$1.6 million increase was primarily due to a larger portfolio balance followingresulting from the investment of cash proceeds from our financing transactiontransactions completed in August 2025,2025 asand wellMay as2026 proceeds received fromand the $35.0collaboration milliontransaction payment from Gilead for an exclusive license to our HPI programcompleted in December 2025.