What changed in this filing

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Item 7. Management’s Discussion and Analysis

2026-03-19 compared with 2025-03-20 · 204 added, 133 removed, 217 unchanged (61% of the section changed)

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Our pipeline includes multiple clinical-stage investigational therapies, including:

(1) two helicase-primase inhibitors (HPI) targeting recurrent genital herpes;

(1) two long-acting helicase-primase inhibitors (HPI) for 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) targeting transplant-related herpesviruses, which is currently undergoing studies to enable a regulatory filing, and we have additional research programs against multiple antiviral targets.

Our pipeline also includes a novel, oral broad-spectrum non-nucleoside polymerase inhibitor (NNPI) for 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.”

Our Clinical Programs and Regulatory Filing-Enabling Program

Since the beginning of 2024, we have initiated:

(1) both the Phase 1a and Phase 1b portions of a Phase 1a/b study of 5366, long-acting HPI for recurrent genital herpes;

(2) the Phase 1a portion of a Phase 1a/b study of 1179, also a long-acting HPI for recurrent genital herpes;

(3) a Phase 1a study of 6250, an orally bioavailable HDV entry inhibitor;

and (4) a Phase 1b study of 4334, a highly potent, next-generation CAM for chronic HBV infection.

We expect to initiate the Phase 1b portion of the Phase 1a/b study of 1179 in the first half of 2025.

We announced interim results from the Phase 1a portion of the 5366 study in September 2024, interim results from the Phase 1b study of 4334 in December 2024 and interim results from the Phase 1a portion of the 1179 study in February 2025.

In addition, during December 2024, we identified a development candidate, 7423, in our broad-spectrum NNPI program targeting transplant-associated herpesviruses.

2025 was a pivotal year for us, as we reported data readouts for 5366, 1179, 4334 and 6250 as follows:

• February 2025:

o 1179 – Positive Phase 1a interim results in the Phase 1a/b study

o 4334 – Positive Phase 1b topline results

• August 2025:

o 5366 – Positive Phase 1b interim results from the weekly dosing cohorts in the Phase 1a/b study

o 6250 – Positive Phase 1a interim results

• December 2025:

o 1179 – Positive Phase 1b interim results in the Phase 1a/b study

o 5366 – Positive Phase 1b interim results from the monthly dosing cohorts in the Phase 1a/b study

In addition, during December 2024, we identified a development candidate, ABI-7423 (7423), in our broad-spectrum NNPI program targeting transplant-associated herpesviruses.

7423 is a prodrug, and in October 2025, we transitioned our development from 7423 to 7272, its parent molecule.

7272 is currently in regulatory filing enabling studies.

Recurrent Genital Herpes/HSV-1 and HSV-2

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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, and symptoms may become more serious with additional episodes.

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 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 patients may experience more severe and prolonged symptoms due to increased recurrence rates.

Immunocompromised individuals may experience more severe and prolonged symptoms due to increased recurrence rates.

HPIs are antiviral agents in development for the treatment of recurrent genital herpes, with a clinically-validated mechanism of action.

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As a result, HPIs are active immediately upon reactivation of latent HSV-1 and HSV-2.

HPIs are active against TK-deficient HSV-1 and HSV-2, which is a major mechanism of resistance to nucleoside analogs.

Most people with initial symptomatic genital herpes who are infected with HSV-2 have frequent recurrences, generally between three and 15 per year, including over four million people in the United States and France, Germany, Italy and Spain (collectively, the EU4) and the United Kingdom (UK).

Furthermore, HPIs are active against TK-deficient HSV-1 and HSV-2, which is a major mechanism of resistance to nucleoside analogs.

Most people with initial symptomatic genital herpes who are infected with HSV-2 have frequent recurrences, generally between three and 15 per year, impacting 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.

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There are still high titer (greater than 10 4 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 are developing 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.

In addition, we are developing a second novel, potent, long-acting HPI for genital herpes, 1179, which was in-licensed to us as part of our collaboration with Gilead.

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 September 2024, we announced positive interim data for the Phase 1a portion of the 5366 study.

Interim results exceeded our objectives for this Phase 1a study and support 5366’s progression into Phase 1b, which we initiated during the third quarter of 2024.

Across the Part A (Phase 1a) cohorts evaluated, 5366 had a mean half-life of approximately 20 days when dosed orally, supporting once-weekly oral dosing, the target profile for 5366, as well as showing the potential for once-monthly oral dosing.

We plan to explore both once-weekly and once-monthly oral dosing regimens in the Part B (Phase 1b) portion of the study.

In the Part A cohorts, 5366 has been well-tolerated with a favorable safety profile observed with exposure of up to 70 days.

Treatment-emergent adverse events (AEs) were all mild to moderate in intensity and all were considered not related to study treatment by the study investigators;

there have been no serious AEs in any dose arm.

There were no treatment-related Grade 3 or 4 laboratory abnormalities and no protocol-defined stopping criteria were met.

There were no clinically significant electrocardiogram (ECG) abnormalities or patterns of AEs or laboratory abnormalities noted.

We expect interim data from the Phase 1b portion of the 5366 study to be available in fall 2025.

In addition to 5366, we are also advancing 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/b 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.

In February 2025, we announced positive interim data for the Phase 1a portion of the 1179 study.

Interim results exceeded our objectives for this Phase 1a study and support 1179’s progression into Phase 1b, and we plan to move directly into the Phase 1b study in participants with recurrent genital herpes.

Across the Part A (Phase 1a) cohorts

evaluated as of the February 13, 2025 data cutoff date, 1179 had a mean half-life of approximately four days when dosed orally, supporting once-weekly oral dosing, the target profile for 1179.

In all cohorts as of the February 13, 2025 data cutoff date, 1179 has been well-tolerated with a favorable safety profile observed.

Treatment-emergent AEs were all mild in intensity and all were considered not related to study treatment by the study investigators;

there have been no serious AEs in any dose cohort.

One self-limited Grade 2 alanine transaminase elevation was observed in a cohort evaluating the highest dose of 300 mg.

There were no treatment-related Grade 3 or 4 laboratory abnormalities and no protocol-defined stopping criteria were met.

There were no clinically significant ECG abnormalities or patterns of AEs or laboratory abnormalities noted.

We expect interim data from the Phase 1b portion of the 5366 study to be available in fall 2025.

The Phase 1b study of 1179 study will be conducted concurrently with the ongoing Phase 1b evaluation of 5366, our other long-acting helicase-primase inhibitor candidate that began dosing in Phase 1b in the fourth quarter of 2024.

The studies are anticipated to be conducted at the same sites using equivalent eligibility criteria and outcome measures for both candidates.

We plan to report interim data for both candidates together in fall 2025.

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) 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 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.

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 genital lesion rate, a 94% reduction compared to placebo (p<0.01) was observed with the 350 mg weekly dose.

The rate of genital swabs with high viral load (i.e., >10 4 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.

We reported additional interim data from the Phase 1b portion of the 5366 study in December 2025, which included data from a monthly oral dosing regimen.

In the 5366 monthly dose cohort, potent antiviral activity was observed, with a 76% reduction in HSV-2 shedding rate compared to placebo (p<0.01) over the 29-day evaluation period.

The majority of positive swabs (89%) were collected in the last two weeks of the evaluation period when drug levels were declining.

We observed an 88% reduction in virologically confirmed genital lesion rate (p=0.01), along with an 81% reduction in the number of samples with high viral load (p<0.01) compared to placebo in the monthly dose cohort.

Across the two weekly oral dose cohorts and the monthly oral dose cohort of the Phase 1b study, 5366 demonstrated a pharmacokinetic (PK) profile that continues to support once-weekly and potentially once-monthly dosing.

5366 was observed to be well-tolerated at all dose levels tested in the Phase 1b portion of the study.

The two weekly oral cohorts are complete and unblinded safety data has been reported;

the oral monthly cohort is ongoing and safety data remains blinded.

Across all cohorts, the proportion of participants reporting treatment-emergent AEs was similar between 5366 and placebo recipients, and all were Grade 1 or Grade 2.

One Grade 3 AE was reported, hypertriglyceridemia, in a participant with relevant medical history who had Grade 4 elevated triglycerides pre-dose on Day 1.

This AE resulted in study discontinuation but was not considered treatment related.

The proportion of participants reporting treatment-emergent lab abnormalities was similar in 5366 and placebo recipients with the majority being Grade 1 or Grade 2.

In the unblinded weekly oral dose cohorts:

there were three participants with treatment-emergent Grade 3 lab abnormalities, all of which are considered unrelated to assigned treatment;

one participant with exercise-associated elevation in creatine kinase (150/30 mg QW);

one participant with an elevation of cholesterol in the follow up period, which participant had a Grade 2 elevation at baseline (350 gm QW);

and one participant, who was dosed with placebo, with decreased neutrophils.

There did not appear to be a dose-response relationship in either the frequency or severity of the treatment-emergent AEs or lab abnormalities.

No serious AEs have been reported to date.

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.

A late-breaking oral presentation of the interim 5366 Phase 1b data reported in August 2025 was presented at the 38th Congress of the International Union Against Sexually Transmitted Infections – Europe, which took place in October 2025 in Athens, Greece.

The 5366 data reported in August and December 2025 will be presented at the Congress of the European Society of Clinical Microbiology and Infectious Diseases (ESCMID) taking place in Munich, Germany in April 2026.

In addition to 5366, we have also begun 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 the study in September 2024, which was approved in October 2024.

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.

Across both oral weekly dose cohorts, 1179 demonstrated a PK profile that continues to support once-weekly dosing.

1179 was observed to be well-tolerated at both doses.

Overall, the proportion of participants reporting treatment-emergent AEs was similar between 1179 and placebo recipients.

Of the treatment-emergent AEs reported, the majority were Grade 1 or Grade 2.

The most common AEs were upper respiratory tract infection and headache.

There have been no serious AEs reported to date.

One Grade 3 AE of migraine was reported in a participant enrolled in the 20 mg/placebo cohort.

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 Phase 2 enabling studies for a once-weekly treatment regimen, subject to the completion of chronic toxicology studies, which are underway.

The completion of the Phase 1b studies of both 5366 and 1179 constitute an option triggering point under the terms of the Gilead Collaboration Agreement, as defined below under "Collaboration and License Agreement — Gilead Sciences, Inc." The 1179 data reported in December 2025 will be presented 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 receive Gilead’s development plan and budget for the HPI program and make our decision regarding the Profit-Share (as defined below) by mid-2026.

We anticipate Gilead will initiate a Phase 2 clinical study for the HPI program in 2026.

For more information regarding Gilead’s exercise of its option, see “Collaboration and License Agreement—Gilead Sciences, Inc.—Option Exercise.”

Our HBV and HDV Programs

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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, of 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.

Of 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.

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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.

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 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, 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.

The current standard of care treatment for HDV is off-label pegylated interferon-α (IFN-α) injected weekly or, in 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.

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.

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Similar to HBV, HDV utilizes HBsAg to enter hepatocytes by binding the cellular transmembrane protein sodium taurocholate co-transporting peptide (NTCP).

NTCP is highly expressed on human hepatocytes, where it serves as one of several proteins involved in the

transport of bile acids.

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 blocker of NTCP, is the only approved therapy for HDV (approved in Europe).

6250 uses the same clinically-validated MOA as bulevirtide.

Notably, bulevirtide, a peptide blocker of NTCP, is the only approved therapy for HDV.

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;

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We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for people living with HDV and could significantly improve treatment uptake and diagnosis rates, especially when compared with currently available injectable products.

In September 2023, we nominated 6250, a novel, orally bioavailable small molecule designed to inhibit entry of HBV and HDV by targeting NTCP.

In nonclinical studies, 6250 demonstrated low nanomolar potency against all tested HBV/HDV genotypes, favorable selectivity for NTCP versus other bile acid transporters, good oral bioavailability and a PK profile in nonclinical species projected to support once-daily oral dosing.

In GLP toxicology studies, 6250 demonstrated a favorable nonclinical safety profile with wide safety margins.

We initiated a Phase 1a clinical study of 6250 during the fourth quarter of 2024, and we expect interim safety, PK and biomarker data from single-ascending and multiple-ascending doses cohorts in healthy participants in the third quarter of 2025.

A Phase 1a clinical study of 6250 was initiated in the fourth quarter of 2024, and in August 2025, we announced interim PK, biomarker and safety data from single-ascending and multiple-ascending doses 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-fold higher than the exposure seen after the first dose.

Dose-dependent elevations of total serum bile acids (TBAs) were observed for both the 5 mg and 25 mg single-dose cohorts, indicative of NTCP target engagement.

In the highest single-dose cohort of 25 mg, coproporphyrin I (CP-1), a biomarker for off-target engagement of the organic anion transporters, OATP1B1 and/or OATP1B3, was also elevated.

CP-1 elevation was not noted at the other doses.

Given the predicted 6250 accumulation driven by the long half-life and the observed elevations of TBAs for the single-dose cohorts, doses at and below 1 mg daily were selected for the multiple-dose cohorts to characterize the lower end of the dose-response curve.

Elevation of TBAs was observed for both the 0.2 mg and 1 mg daily multiple-dose cohorts, consistent with the respective 6250 exposures.

Minimal TBA elevation was observed in the 0.05 mg daily multiple-dose cohort.

Treatment-emergent AEs and laboratory abnormalities were all Grade 1 or 2 in severity with the majority being Grade 1.

There were no serious AEs in any dose cohort.

No protocol defined stopping criteria were met.

There were no clinically significant electrocardiogram abnormalities or patterns of AEs noted.

One Grade 2 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.

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.

We have completed enrollment and the follow-up period in the Phase 1a study, as well as the chronic toxicology studies to enable longer term dosing and we are preparing for Phase 2 clinical studies, with Phase 2 initiation expected in the fourth quarter of 2026.

6250 Phase 1a data will be presented at the European Association for the Study of the Liver (EASL) Congress taking place in Barcelona, Spain in May 2026.

Capsid Assembly Modulator

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On this basis, our next-generation CAM, 4334, has shown nonclinical proof of principle.

In a variety of cell culture models, 4334 has demonstrated the ability to reduce production of HBV DNA levels as well as the surrogate markers for cccDNA establishment:

In a variety of cell culture models, 4334 has demonstrated the ability to reduce production of HBV DNA levels as well as

the surrogate markers for cccDNA establishment:

HBV e antigen (HBeAg), HBV core-related antigen (HBcrAg) and HBV pre-genomic RNA (pgRNA).

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).

In contrast, while active against MOA #1, first-generation CAMs have not demonstrated adequate potency to sufficiently block MOA #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.

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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, which indicated that 4334

maintained clinical exposures multiple folds above those anticipated to be required for potent viral activity and inhibition of cccDNA formation.

A mean decline in HBV DNA of 2.9 log 10 IU/mL was observed in a population of predominately HBeAg negative participants.

Among the subset of participants with detectable HBV RNA at baseline, a mean decline of 2.5 log 10 U/mL for HBV RNA was observed.

We reported interim clinical results from the initial 150 mg cohort in December 2024, and 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.

Mean declines in HBV DNA of 2.9 log 10 IU/mL and 3.2 log 10 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 log 10 U/mL and 2.3 log 10 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 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 the 400 mg cohort will be the final cohort for this Phase 1b study.

We anticipate releasing data from the 400 mg cohort in the first half of 2025.

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.

The completion of 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 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, the Company retains 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 structured process to find potential partners.

We do not plan to advance 4334 further without a partner.

Transplant-Associated Herpesviruses

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These viruses establish lifelong latent infections and frequently reactivate in transplant patients due to the use of immunosuppressive drugs following transplantation.

These uncontrolled viral 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.

These uncontrolled herpesvirus 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.

While there are approved antivirals that are administered in a transplant setting, currently approved antivirals are not active against a broad spectrum of transplant-associated herpesviruses and pose the risk of potentially serious side effects and drug-drug interactions.

As a result of these limitations, we identified an opportunity to develop an oral, broad-spectrum NNPI for transplant-associated herpesvirus infections, which could greatly advance treatment.

In December 2024, we nominated 7423 as our development candidate to undergo CTA-enabling studies, which are ongoing.

In December 2024, we nominated 7423, a prodrug, as our development candidate to undergo regulatory filing-enabling studies.

In October 2025, we transitioned our discovery and development from 7423 to its parent molecule, 7272, which is currently in regulatory filing-enabling nonclinical studies.

Research Programs

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

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 antivirals to treat serious viral diseases.

Collaboration and License Agreement

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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 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.

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.

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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.

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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, and commercialization on any optioned programs.

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 years of the collaboration.

Following Gilead’s opt-in, Gilead will control the further discovery, research, development and commercialization on any optioned 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 anniversaries of the collaboration.

The Gilead Collaboration Agreement is subject to termination by either party for the other party’s uncured, material breach or insolvency.

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We and Gilead also entered into a Common Stock Purchase Agreement and an Investor Rights Agreement (together, the Gilead Equity Agreements), which were both amended in June 2024 in connection with a financing transaction, in which a new investor purchased shares of common stock and was issued a warrant (the 2024 Financing Transaction).

Pursuant to the Gilead Equity Agreements, Gilead made an upfront equity investment of $15.2 million by purchasing from us 1,089,472 shares of our common stock at a purchase price of $13.92 per share.

Pursuant to the Gilead Equity Agreements, Gilead made an upfront equity investment of $15.2 million by purchasing

from us 1,089,472 shares of our common stock at a purchase price of $13.92 per share.

The terms of the Gilead Equity Agreements provided Gilead the right to elect to purchase additional shares of common stock from us at a premium in an amount that results in Gilead owning 29.9% of our then-outstanding voting common stock.

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Subject to certain exceptions, neither Gilead nor its affiliates may exercise any portion of the warrant to the extent that Gilead would own more than 19.9% of the number of our shares of common stock outstanding immediately after giving effect to such exercise.

Gilead also participated in a financing transaction in August 2025 on the same terms as the new investors.

We and Gilead entered into a Securities Purchase Agreement for the issuance and sale, in a private placement, of 2,295,920 shares of our common stock at a combined purchase price of $19.60 per shares and accompanying one-half of one Class A Warrant and one-half of one Class B Warrant (collectively, the August 2025 Private Placement).

The common stock, the Class A Warrant and the Class B Warrant were sold to Gilead pursuant to the terms of the Investor Rights Agreement.

The Class A Warrant and the Class B Warrant each provide for the right to purchase up to 1,147,960 shares of our common stock.

The Class A Warrant has an exercise price of $21.60 per share, became immediately exercisable on the date of issuance and will expire 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 total for our Phase 2 clinical study evaluating 5366 versus valacyclovir.

The Class B Warrant has an exercise price of $21.60 per share and is exercisable between November 15, 2026 and December 31, 2026.

Notwithstanding the foregoing, 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.

In October 2025, as required under the registration rights terms of the Investor Rights Agreement, we filed a registration statement on Form S-3 (the Registration Statement) with the Securities and Exchange Commission (SEC) to register all of the shares of our common stock that have been issued and sold to Gilead, as well as all of the shares of common stock underlying the warrants that have been issued and sold to Gilead.

The SEC declared the Registration Statement effective in November 2025.

Option Exercise

In December 2025, Gilead exercised its option to exclusively license our HPI program for the treatment of recurrent genital herpes, including 5366 and 1179.

This is the first program that Gilead will advance under the Gilead Collaboration.

Under the terms of the Gilead Collaboration Agreement, we received a $35 million payment in connection with Gilead’s exercise of our HPI program.

The $35 million payment reflects a $45 million option fee, net of $10 million in accelerated funding that we received under the First Amendment to the Gilead Collaboration Agreement, which was creditable against future payments.

Gilead received an exclusive license to 5366 and 1179 and will have the sole right and responsibility for further clinical development and commercialization of the HPI program.

We remain eligible to receive up to $330 million in regulatory and commercial milestones, as well as tiered royalties on net sales ranging from the high single-digits to low teens.

We will also have the right to opt in to share 40% of all costs and profits in the United States (the Profit-Share) in lieu of receiving milestones and royalties for that program in the United States after receipt of a development plan and budget from Gilead.

Since our inception, we have had no revenue from product sales and have funded our operations principally through debt financings prior to our initial public offering in 2010 and through equity financings and collaborations since then.

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Additionally, we expect our research and development expenses to increase over the coming years as we continue the development of our product candidates.

As a result, our operating losses are likely to be substantial over the next several years and thereafter if none of our product

candidates are approved or successfully launched.

As a result, our operating losses are likely to be substantial over the next several years and thereafter if none of our product candidates are approved or successfully launched.

We are unable to predict the extent of any future losses or when we will become profitable, if at all.

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For contracts with customers, we apply the following five-step model, each of which requires judgment, in order to determine this amount:

(1) identification of the promised goods or services in the contract;

(2) determination of whether the promised goods or services are performance obligations, including whether they are distinct in the context of the contract;

(1) identification of the contract(s) with a customer;

(2) identification of the performance obligations in the contract, including whether they are distinct in the context of the contract;

(3) measurement of the transaction price, including the constraint on variable consideration;

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We then allocate the total transaction price to each performance obligation based on its SSP and recognize as revenue the amount of the transaction price that is allocated to the respective performance obligation when or as the performance obligation is satisfied.

We account for contract modifications, defined as changes in the scope or price (or both) of a contract that are approved by the parties to the contract, such as a contract amendment, when the parties to a contract approve a modification that either creates new, or changes existing, enforceable rights and obligations of the parties to the contract.

either creates new, or changes existing, enforceable rights and obligations of the parties to the contract.

We use one of the following methods depending on facts and circumstances:

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or (iii) as a cumulative catch-up adjustment to the original contract if the remaining goods or services are not distinct from those transferred before the modification.

For recognition of revenue relating to the Gilead Collaboration Agreement at commencement of the arrangement, we determined the transaction price and allocated it to a single combined performance obligation, the discovery, research and development services during the collaboration term.

We estimated the SSP of extension fees and opt-in rights pursuant to the Gilead Collaboration Agreement using significant estimates, including forecasted revenues and costs, development timelines, discount rates, and probabilities of technical and regulatory success.

We concluded none of the options in the contract are performance obligations at the outset of the arrangement as they are contingent upon

option exercise, are capable of being distinct from the research and development services and are not offered at a discount to their SSP.

We determined the First Amendment to the Gilead Collaboration Agreement represents a contract modification within the scope of the revenue from contracts with customers guidance.

We concluded there continues to be a single combined performance obligation consisting of a series of distinct research and development services, and therefore, the remaining services under the First Amendment to the Gilead Collaboration Agreement are distinct from the research and development services already provided.

Accordingly, we accounted for the First Amendment as a termination of the existing contract and the creation of a new contract and are recognizing the revenue on a prospective basis by reassessing the transaction price and allocating it to the remaining research and development services.

We evaluate each performance obligation to determine if it can be satisfied at a point in time or over time, and we measure the services delivered to the customer, which we periodically review based on the progress of the related program.

We recognize revenue under the Gilead Collaboration Agreement over time using a cost-based input method, which continues to be appropriate following the First Amendment to the Gilead Collaboration Agreement.

We entered into the First Amendment to the Gilead Collaboration Agreement in December 2024 and a letter agreement in July 2025.

We determined each of these amendments to the Gilead Collaboration Agreement represent a contract modification within the scope of the revenue from contracts with customers guidance.

For both contract modifications, we concluded there continues to be a single combined performance obligation consisting of a series of distinct research and development services (R&D Services), and therefore, the remaining services under the modified agreement are distinct from the R&D Services already provided.

Accordingly, we accounted for each modification as a termination of the existing contract and the creation of a new contract and are recognizing the revenue prospectively by reassessing the transaction price and allocating it to the remaining R&D Services.

We estimated the SSP of extension fees and opt-in rights pursuant to the modified Gilead Collaboration Agreement using significant estimates, including forecasted revenues and costs, development timelines, discount rates, and probabilities of technical and regulatory success.

For both modifications, we concluded none of the options in the contract were performance obligations as they were contingent upon option exercise, were capable of being distinct from the R&D Services and were not offered at a discount to their SSP.

In December 2025, Gilead exercised its option to exclusively license our HPI program, which we determined was a new contract under the contracts with customers accounting standard as it was deemed an exercise of a marketing offer made pursuant to the original terms of the Gilead Collaboration Agreement and First Amendment.

We determined the exclusive license granted to Gilead for the HPI program represents a distinct performance obligation because Gilead can benefit from the license together with readily available resources and its ability to sublicense the rights.

The $35.0 million opt-in fee is included in the fixed transaction price.

Variable consideration related to regulatory and commercial milestone payments, royalties and cost reimbursements are constrained because such amounts are highly susceptible to factors outside our influence.

We recognize revenue from R&D Services under the Gilead Collaboration Agreement over time using a cost-based input method, which continues to be appropriate following subsequent contract modifications of the Gilead Collaboration Agreement.

We recognize revenue from exclusive licenses to our programs under the Gilead Collaboration Agreement at a point in time upon transfer of the license, when Gilead obtains the ability to use and benefit from the license.

Revenue related to certain performance obligations that are satisfied over time could be materially impacted as a result of changes in the estimated total research effort required to satisfy those obligations.

A hypothetical 10% change in the total estimated effort required to satisfy the single combined performance obligation related to the Gilead Collaboration Agreement would have changed the related revenue recognized during the year ended December 31, 2024 by as much as $3.5 million.

The effect of any change made to an estimated input component and, therefore revenue recognized, would be recorded as a change in estimate.

In addition, amounts of variable consideration (including regulatory and commercial milestones) are included in the transaction price to the extent that it is probable that a significant reversal in the amount of cumulative revenue recognized will not occur and when the uncertainty associated with the variable consideration is subsequently resolved.

The effect of any change made to an estimated input component or variable consideration and, therefore revenue recognized, would be recorded as a change in estimate.

Such changes in estimate could have a material impact on the revenue recognized in a future period.

In addition, variable consideration (including regulatory and commercial milestones) must be evaluated to determine if it is constrained and, therefore, excluded from the transaction price.

We regularly review our expectations of the extent of progress, including whether any variable consideration was no longer constrained, and, if any changes in estimates were made, we recognized revenue using the cumulative catch-up method.

Research and Development Contract Costs and Accruals

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Year Ended December 31,

Collaboration revenue

Collaboration revenue from a related party

Collaboration revenue was $72.3 million for the year ended December 31, 2025 compared to $28.5 million for the year ended December 31, 2024.

The $21.4 million increase in collaboration revenue was driven by recognizing a full year of revenue in 2024 under the Gilead Collaboration Agreement, which was entered into in October 2023.

Collaboration revenue for 2023 also includes recognizing the remaining $2.7 million of deferred revenue under our Collaboration Agreement with BeiGene, Ltd.

(BeiGene) upon our discontinuing development of ABI-H3733 (3733), which left no products licensed to BeiGene and no remaining performance obligations.

The $43.8 million increase was primarily driven by the recognition of $35.0 million of revenue associated with the exclusive license granted and transferred to Gilead for the HPI program in December 2025.

The increase also reflects the additional $10.0 million payment we received in December 2024 under the First Amendment to the Gilead Collaboration Agreement, which was largely recognized in 2025.

Research and Development Expenses

Research and development expenses consist primarily of employee-related expenses, fees paid to CROs and CMOs, lab supplies and other third-party expenses that support our research and discovery, nonclinical and clinical activities.

External costs represent a significant portion of our research and development expenses, which we track on a program-by-program basis following the nomination of a development candidate.

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.

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Research and discovery

Vebicorvir (VBR)

Total external program expenses

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Total research and development expenses

(1) Reflects net amounts refundable to us after the final reconciliation of costs of the clinical trial conducted pursuant to the Clinical Trial Collaboration Agreement with Arbutus Biopharma Corporation, which was terminated in February 2023.

(1) In October 2025, we transitioned our discovery and development from 7423 to its parent molecule, 7272, which is currently in regulatory filing-enabling preclinical studies.

(2) Reflects net amounts refundable to us after final reconciliation of costs for the clinical trial conducted pursuant to the Clinical Trial Collaboration Agreement with Arbutus Biopharma Corporation, which was terminated in February 2023.

We received the refund in 2025.

Research and development expenses were $64.8 million for the year ended December 31, 2025, compared to $55.9 million for the year ended December 31, 2024.

The $7.0 million increase in research and development expenses was primarily driven by increases in external program expenses from the advancement and expansion of our pipeline, most notably from our recurrent genital herpes programs, 1179 and 5366, as well as our HDV entry inhibitor, 6250.

These increases in external expenses were partially offset by savings from our discontinuation of 3733 and VBR.

We also experienced a $0.9 million increase in employee and contractor-related expenses due to higher headcount and increased travel costs as a result of having an expanded pipeline with more candidates entering the clinic in 2024.

overall increase was further offset by a $1.9 million decrease in our facility and other expenses, reflecting cost savings in rent and related expenses from our corporate headquarters sublease, which commenced in November 2023.

The $8.9 million increase was primarily driven by higher external program expenses as we advanced our pipeline.

Most notably, our HPI program incurred additional costs as both the 1179 and 5366 Phase 1a/b studies were underway during 2025, with more participants enrolled than in 2024.

Employee and contractor-related expenses also increased, reflecting $2.1 million in increased compensation costs driven by annual salary increases and larger bonuses due to strong performance against our 2025 corporate objectives.

The increase additionally reflects $1.1 million of higher stock-based compensation expense associated with performance stock units (PSUs) granted in 2025.

These increases were partially offset by decreases in external program expenses from the completion of our 4334 Phase 1b study in mid-2025.

General and Administrative Expenses

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General and administrative expenses were $19.6 million for the year ended December 31, 2025, compared to $18.0 million for the year ended December 31, 2024.

The $4.9 million decrease in general and administrative expenses was primarily due to higher legal expenses incurred in 2023 related to the Gilead Collaboration, as well as higher stock-based compensation expense in 2023, mainly resulting from the vesting of restricted stock awards with performance based-vesting conditions.

The $1.6 million increase was primarily driven by $1.2 million of higher professional fees related to patent filings as well as an increase of $0.5 million in stock-based compensation expense associated with PSUs granted in 2025.

Interest and Other Income, Net

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Interest and other income, net was $6.0 million for the year ended December 31, 2025, compared to $5.6 million for the year ended December 31, 2024.

The increase of $2.1 million was primarily due to more interest income earned on marketable securities resulting from having a larger portfolio balance after the receipt of $100.0 million upon entering into the Gilead Collaboration in October 2023 and multiple equity financings entered into in 2024.

The $0.4 million increase was primarily driven by a larger investment portfolio balance following our financing transaction in August 2025.

Income Tax Expense

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Income tax expense

There was no income tax expense for the year ended December 31, 2025.

Income tax expense was $0.3 million for the year ended December 31, 2024 due to taxable income incurred from the upfront payments received under the Gilead Collaboration in 2023.

Income tax expense was insignificant during the year ended December 31, 2023.

Liquidity and Capital Resources

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As a result of our significant research and development expenditures and the lack of any FDA-approved products to generate product sales revenue, we have not been profitable and have generated operating losses since we were incorporated in October 2005.

We have funded our operations through December 31, 2024 principally through equity

financings, raising an aggregate of $648.0 million in net proceeds, and strategic collaborations, raising an aggregate of $200.9 million.

Future Funding Requirements

We expect our future operating expenses to increase substantially over the coming years as we continue to advance our candidates into the clinic.

We have funded our operations through December 31, 2025 principally through equity financings, raising an aggregate of $821.8 million in net proceeds, and strategic collaborations, raising an aggregate of $236.2 million.

Funding Requirements

We expect our future operating expenses to increase over the coming years as we continue to expand our pipeline and advance our candidates.

We monitor our cash needs and the status of the capital markets on a continuous basis.

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We expect to continue to raise capital when and as needed and at the time and in the manner most advantageous to us.

We expect our existing cash, cash equivalents and marketable securities will enable us to fund our operations into the middle of 2026.

We have based this estimate on assumptions that may prove to be wrong, and we may utilize our available capital resources sooner than we currently expect.

As of December 31, 2025, we held cash, cash equivalents and marketable securities of $248.1 million.

Based on our current operating plan, we believe we have sufficient funds to meet our operating requirements into 2028.

We have based our estimate on assumptions that may prove to be wrong, and we may utilize our available capital resources sooner than we currently expect.

Our contractual obligations include operating lease obligations totaling $3.2 million as of December 31, 2025, of which $0.8 million are short-term.

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Our future capital requirements will depend on many factors, including:

• our ability to raise capital despite macroeconomic and geopolitical events impacting financial markets, such as rising inflation, potential effects of changes in federal government regulation or policies, including changes in or new tariffs, and market volatility;

• our ability to realize future potential benefits pursuant to the Gilead Collaboration and maintain the collaboration;

• the future development costs we would incur if we elect to participate in the Profit-Share for programs advanced by Gilead under the Gilead Collaboration;

• the scope, progress, results and costs of our ongoing drug discovery, nonclinical development, laboratory testing and clinical studies of our product candidates and any additional clinical studies we may conduct in the future;

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• the costs of preparing, filing and prosecuting patent applications in the United States and abroad, maintaining and enforcing our intellectual property rights and defending intellectual property-related claims.

Identifying potential product candidates and conducting nonclinical testing and clinical studies is a time-consuming, expensive and uncertain process that takes years to complete, and we may never generate the necessary data or results required to obtain marketing approval and achieve product sales.

In addition, our product candidates, if approved, may not achieve commercial success.

Our commercial revenues, if any, will likely be derived from sales of medicines that we do not expect to be commercially available for years, if at all.

Accordingly, we will need to continue to rely on additional financings to achieve our business objectives.

Adequate additional financings may not be available to us on acceptable terms, or at all.

To the extent that we raise additional capital through the sale of equity, the ownership interest of our stockholders will be diluted, and the terms of these securities may include liquidation or other preferences that adversely affect the rights of our common stockholders.

Debt financing, if available, may involve agreements that include covenants limiting or restricting our ability to take specific actions, such as incurring additional debt, making capital expenditures or declaring dividends.

If we are unable to raise additional funds when needed, we may be required to reduce staff, delay, scale back or discontinue our product development and clinical studies or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.

The following table summarizes our cash flows for the periods presented (in thousands):

Year Ended December 31,

Net cash (used in) provided by operating activities

Net cash provided by (used in) investing activities

Net cash used in operating activities

Net cash (used in) provided by investing activities

Net cash provided by financing activities

Net increase (decrease) in cash and cash equivalents

Net increase in cash and cash equivalents

Operating Activities

Net cash used in operating activities for the year ended December 31, 2024 was $51.1 million, compared to net cash provided by operating activities of $22.7 million for the same period in 2023.

The decrease in operating cash flows was primarily due to $90.7 million received under the Gilead Collaboration Agreement in 2023, partially offset by cost savings in rent and related expenses attributable to our corporate headquarters sublease, which commenced in November 2023, and the timing of vendor invoicing and payments.

Net cash used in operating activities was $41.1 million for the year ended December 31, 2025, compared to $51.1 million for the same period in 2024.

The decrease was primarily due to $25.2 million more cash received under the Gilead Collaboration Agreement in 2025 compared to 2024, partially offset by higher operating expenses in 2025 from the advancement of our clinical pipeline, most notably due to costs incurred for our HPI program.

Investing Activities

Net cash provided by investing activities for the year ended December 31, 2024 was $40.2 million, compared to net cash used in investing activities of $69.1 million for the same period in 2023.

The increase in cash flows from investing was due to higher proceeds from maturities of our marketable securities, which exceeded purchases in 2024.

In contrast, in 2023 our purchases of marketable securities exceeded proceeds because of additional funds available to invest from the upfront payment received from Gilead under the Gilead Collaboration Agreement.

Net cash used in investing activities was $113.5 million for the year ended December 31, 2025, compared to net cash provided by investing activities of $40.2 million for the same period in 2024.

The change was primarily due to our purchases of marketable securities following our financing in August 2025, as we invested the proceeds from those offerings.

Financing Activities

Net cash provided by financing activities for the year ended December 31, 2024 was $29.4 million, compared to $13.8 million for the same period in 2023.

The increase in financing cash flows was primarily driven by the sale of 0.6 million more shares of our common stock through multiple equity financings in 2024 and at an increased price per share compared to 2023.

Net cash provided by financing activities was $174.7 million for the year ended December 31, 2025, compared to $29.4 million for the same period in 2024.

The increase was due to larger net proceeds of $166.4 million from our financing in August 2025 and the subsequent exercise of warrants issued in that transaction, totaling $5.5 million, compared to the $27.3 million net proceeds received from our June and December 2024 financings.

Quantitative and Qualitat ive Disclosures about Market Risk

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Compared sentence by sentence after normalising whitespace, quotation marks, case and digits, so re-formatting and restated figures do not read as changed language. Wording changes appear as one removal and one addition. The current filing and the prior one are authoritative.

What changed 10-K

Item 7. Management’s Discussion and Analysis