ASSEMBLY BIOSCIENCES, INC.
For the period ended Sep 30, 2025. Filed Nov 10, 2025.
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A company's report for each of its first three quarters. The financial statements are not audited. It shows how the business has moved since the last annual report, and what management says changed.
Sep 30, 2025 · Filed Nov 10, 2025
ASMB$20.42+2.1%Stored close · as of Nov 6, 2026
What changed in Management’s Discussion and Analysis?
Read the current filingPrevious report: 10-Q
Period ended 2025-06-30; filed 2025-08-06.
0000950170-25-104060
Item 2. Management’s Discussion and Analysis of Financial Condition and Results of OperationsCurrent report: 10-Q
Period ended 2025-09-30; filed 2025-11-10.
0001193125-25-274277
Item 2. Management’s Discussion and Analysis of Financial Condition and Results of OperationsThe baseline is this issuer’s latest earlier reporting period of the same form that was filed before the current report. A previous 10-Q is a different quarter, not a year-over-year comparison. Amendments are excluded.
Compared 115 previous paragraphs and 119 current paragraphs.
69 unchanged; 30 reworded; 19 added; 16 removed; 0 previous and 1 current paragraphs rearranged.
Tables are not compared: 9 previous and 9 current tables excluded. Dates, whitespace, punctuation and numbering changes are ignored; changes to financial figures remain significant.
A changed paragraph is not evidence that risk increased or decreased. An unchanged paragraph does not establish that risk stayed the same.
Added paragraphs (19)
Current report
We reported interim data from the Phase 1b portion of the 5366 study in August 2025. 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 samples 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.
Current report
5366 was observed to be well-tolerated at once-a-week oral doses up to 350 mg in participants seropositive for HSV-2 with recurrent genital herpes. Of the treatment-emergent AEs reported, the majority 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. There were three participants with treatment-emergent Grade 3 laboratory abnormalities, all considered unrelated to assigned treatment: an exercise-associated elevation in creatine kinase, a decrease in neutrophils and an elevation of cholesterol in the follow-up period in a participant that had a grade 2 elevation at baseline. There did not appear to be a dose-response relationship in either the frequency or severity of treatment-emergent AEs or laboratory abnormalities. There have been no serious AEs reported to date.
Current report
Enrollment for the Phase 1b portion of the 5366 study is complete. The observed nonclinical pharmacokinetic PK profile continues to support once-weekly dosing and the potential for once-monthly oral dosing regimens. With these data, we expect to move directly into Phase 2 clinical study preparation for a once-weekly treatment regimen in parallel with completion of this Phase 1b study, which includes an ongoing cohort evaluating a monthly oral dosing regimen. The in-life portions of chronic toxicology studies of 5366 are now complete and these studies are expected to support longer-term dosing in Phase 2.
Current report
A late-breaking oral presentation of the interim Phase 1b data reported in August 2025 was presented at the 38 th Congress of the International Union Against Sexually Transmitted Infections – Europe, which took place in October 2025 in Athens, Greece.
Current report
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, and we are preparing for Phase 2 clinical studies in parallel with the completion of ongoing chronic toxicology studies.
Current report
Gilead also participated in a financing transaction in August 2025 on the same 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.
Current report
In October 2025, as required under the registration rights terms of the Investor Rights Agreement, we filed a Registration Statement on Form S-3 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 that can be acquired by exercising the warrants that have been issued and sold to Gilead. The SEC is neither reviewing nor accelerating the effectiveness of registration statements during the ongoing shutdown of the U.S. government.
Current report
In October 2025, we transitioned our discovery and development from ABI-7423 to its parent molecule, ABI-7272, which is currently in regulatory filing-enabling preclinical studies.
Current report
Reflects net amounts refundable to us after the final reconciliation of clinical trial costs received in October 2024 under the Clinical Trial Collaboration Agreement with Arbutus Biopharma Corporation (the Arbutus Biopharma Agreement), which was terminated in February 2023.
Current report
Research and development expenses were $16.6 million for the three months ended September 30, 2025 compared to $13.5 million for the same period in 2024. The $3.1 million increase was primarily driven by higher external program expenses as we advance our pipeline. Most notably, our 1179 and 5366 programs incurred additional costs due to significant patient enrollment in their respective Phase 1b studies. Employee and contractor-related expenses also increased due to the recognition of stock-based compensation expense on previously granted performance-based restricted stock units now deemed probable of vesting. These increases were partially offset by lower expenses for our 4334 program following the completion of its Phase 1b study.
Current report
General and administrative expenses were $5.1 million for the three months ended September 30, 2025 compared to $4.3 million for the same period in 2024. The $0.8 million increase was primarily driven by higher professional fees related to patent filings, commercial planning and market research, as well as an increase in stock-based compensation expense from the recognition of expense on previously granted performance-based restricted stock units now deemed probable of vesting.
Current report
Interest and other income, net was $1.7 million for the three months ended September 30, 2025, compared to $1.3 million for the same period in 2024. The $0.3 million increase was primarily due to more interest earned on marketable securities from having a larger portfolio balance after our financing in August 2025.
Current report
Comparison of the Nine Months Ended September 30, 2025 and 2024
Current report
In October 2025, we transitioned our discovery and development from ABI-7423 to its parent molecule, ABI-7272, which is currently in regulatory filing-enabling preclinical studies.
Current report
Reflects net amounts refundable to us after the final reconciliation of clinical trial costs received in October 2024 under the Arbutus Biopharma Agreement, which was terminated in February 2023.
Current report
Research and development expenses were $47.6 million for the nine months ended September 30, 2025 compared to $41.7 million for the same period in 2024. The $5.9 million increase was primarily driven by higher external program expenses as we advance our pipeline. Most notably, our HSV programs incurred additional costs as both the 5366 and 1179 Phase 1a/b studies were underway during the nine months ended September 30, 2025, compared to only the 5366 Phase 1a study in the same period in 2024. Employee and contractor-related expenses also increased, primarily due to the recognition of stock-based compensation expense on previously granted performance-based restricted stock units now deemed probable of vesting.
Current report
General and administrative expenses were $14.2 million for the nine months ended September 30, 2025 compared to $13.4 million for the same period in 2024. The $0.8 million increase was primarily driven by higher professional fees related to patent filings as well as an increase in stock-based compensation expense from the recognition of expense on previously granted performance-based restricted stock units now deemed probable of vesting.
Current report
In August 2025, we sold to various investors an aggregate of 5,591,840 shares of common stock and pre-funded warrants to purchase up to 1,040,820 shares of common stock. The securities were issued together with accompanying Class A and Class B warrants to purchase up to an aggregated total of 6,632,660 shares of common stock. The combined price per share of common stock with the accompanying Class A and Class B warrants was $19.60, while the combined price per pre-funded warrant with accompanying Class A and Class B warrants was $19.599. In addition, the Company entered into the August 2025 Private Placement with Gilead for the issuance and sale, in a private placement, of 2,295,920 shares of common stock and accompanying Class A and Class B warrants to purchase up to an aggregate of 2,295,920 shares of common stock. The securities were sold together with accompanying warrants at a price of $19.60 per unit. Each pre-funded warrant sold has a nominal exercise price of $0.001 per share, while each Class A and Class B warrant has an exercise price of $21.60 per share. We received aggregate net proceeds of approximately $166.4 million from this financing transaction, after deducting underwriting discounts and commissions and offering expenses payable.
Current report
Funding Requirements
Removed paragraphs (16)
Previous report
We expect interim data from the Phase 1b portion of the 5366 study to be available no later than this fall 2025.
Previous report
Additional studies are planned to explore potential factors associated with these elevations given the role of ABI-6250's target as a bile acid transporter. This assessment is expected to include further pharmacological characterization of ABI-6250 and may incorporate additional cohorts in this Phase 1a study. Assembly Bio expects to conduct these activities in parallel with preparations for Phase 2 clinical studies and the completion of ongoing chronic toxicology studies.
Previous report
Research and development expenses were $16.1 million for the three months ended June 30, 2025 compared to $16.3 million for the same period in 2024. The $0.1 million decrease was primarily driven by a reduction in external program expenses for 6250, which had incurred significant preclinical and start-up activities for the Phase 1a study during the three months ended June 30, 2024. This decrease was largely offset by increased expenses corresponding with the advancement of 5366.
Previous report
General and administrative expenses were $4.6 million for the three months ended June 30, 2025 compared to $4.5 million for the same period in 2024. Overall, expenses remained relatively consistent period over period.
Previous report
Comparison of the Six Months Ended June 30, 2025 and 2024
Previous report
Research and development expenses were $31.0 million for the six months ended June 30, 2025 compared to $28.1 million for the same period in 2024. The increase in research and development expenses was primarily driven by increases in external program expenses from the advancement of our pipeline, primarily due to a $2.6 million increase in 5366.
Previous report
General and administrative expenses were $9.1 million for the six months ended June 30, 2025 compared to $9.1 million for the same period in 2024. Overall, expenses remained relatively consistent period over period.
Previous report
Interest and other income, net was $2.0 million for the six months ended June 30, 2025, compared to $3.1 million for the same period in 2024. The $1.1 million decrease was primarily due to a smaller portfolio balance after using maturing investments to fund operations as well as lower interest rates during the six months ended June 30, 2025 as compared to the same period in 2024.
Previous report
Funding Requirements and Going Concern
Previous report
We evaluated whether there are conditions and events, considered in the aggregate, which raise substantial doubt about our ability to continue as a going concern within one year after the date that this Quarterly Report on Form 10-Q is issued. Since our cash, cash equivalents and marketable securities are not expected to be sufficient to fund operations for at least twelve months following the date this Quarterly Report on Form 10-Q is issued, there is substantial doubt about our ability to continue as a going concern.
Previous report
Our plans to mitigate the conditions that raise substantial doubt about our ability to continue as a going concern include seeking additional funding through public or private equity financings and potential payments from Gilead under the Gilead Collaboration Agreement. However, we cannot assure funding will be available on reasonable terms, if at all. Market volatility, inflation or other factors, such as tariffs, trade wars, barriers or restrictions, or threats of such actions and the related uncertainty thereof, could also adversely impact our ability to access capital when and as needed. Additionally, we may not be successful in the Gilead Collaboration Agreement due to various other factors, including our ability to demonstrate proof of concept in one or more clinical studies so that Gilead will exercise its option to these programs. In addition, even if we demonstrate clinical proof of concept of our candidates, Gilead may choose not to exercise its options. We may obtain additional funding we require through debt financing; however, the availability and amount of such funding is not certain.
Previous report
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 tariffs or the imposition of modified or additional tariffs, market volatility, and potential worsening global economic conditions or economic downturn;
Previous report
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.
Previous report
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 or convertible debt, 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.
Previous report
If we are unable to secure additional funding, we could be forced to reduce staff, delay, scale back or discontinue product development and clinical studies, forego 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.
Previous report
The accompanying condensed consolidated financial statements have been prepared assuming we will continue as a going concern and do not include any adjustments that might result from the outcome of this uncertainty.
Reworded paragraphs (30)
Previous wording
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 helicase-primase inhibitors (HPIs) targeting 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. We currently have corporate and administrative offices and research laboratory space in South San Francisco, California.
Current wording
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 helicase-primase inhibitors (HPIs) targeting herpes simplex virus (HSV) 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. We currently have corporate and administrative offices and research laboratory space in South San Francisco, California.
Previous wording
Since the beginning of 2024, we have initiated: (1) both the Phase 1a and Phase 1b portions of a Phase 1a/b study of ABI-5366 (5366), a long-acting HPI for recurrent genital herpes; (2) both the Phase 1a and Phase 1b portions of a Phase 1a/b study of ABI-1179 (1179), also a long-acting HPI for recurrent genital herpes; (3) a Phase 1a study of ABI-6250 (6250), an orally bioavailable HDV entry inhibitor; and (4) a Phase 1b study of ABI-4334 (4334), a highly potent, next-generation CAM for chronic HBV infection.
Current wording
Since the beginning of 2024, we have initiated: (1) both the Phase 1a and Phase 1b portions of a Phase 1a/b study of ABI-5366 (5366), a long-acting HPI for the treatment of recurrent genital herpes; (2) both the Phase 1a and Phase 1b portions of a Phase 1a/b study of ABI-1179 (1179), also a long-acting HPI for recurrent genital herpes; (3) a Phase 1a study of ABI-6250 (6250), an orally bioavailable HDV entry inhibitor; and (4) a Phase 1b study of ABI-4334 (4334), a highly potent, next-generation CAM for chronic HBV infection.
Previous wording
We announced interim results from the Phase 1a portion of the 5366 study in September 2024, interim results from the Phase 1a portion of the 1179 study in February 2025 and topline results from the Phase 1b study of 4334 in June 2025.
Current wording
We announced interim results from the Phase 1a portion of the 5366 study in September 2024 and interim results from the Phase 1b portion of the 5366 study in August 2025, interim results from the Phase 1a portion of the 1179 study in February 2025, interim results from the Phase 1a study of 6250 in August 2025 and topline results from the Phase 1b study of 4334 in June 2025.
Previous wording
In addition, in December 2024, we identified a development candidate, ABI-7423 (7423), in our broad-spectrum NNPI program targeting transplant-associated herpesviruses, which is currently in regulatory filing-enabling preclinical studies.
Current wording
In addition, in 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 discovery and development from 7423 to its parent molecule, ABI-7272 (7272), which is currently in regulatory filing-enabling preclinical studies.
Previous wording
Genital herpes can be caused by either herpes simplex virus (HSV) type 1 (HSV-1) or HSV 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, 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 individuals may experience more severe and prolonged symptoms due to increased recurrence rates.
Current wording
Genital herpes can be caused by either HSV type 1 (HSV-1) or HSV 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, 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 individuals may experience more severe and prolonged symptoms due to increased recurrence rates.
Previous wording
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 exclusively in-licensed to us as part of our collaboration with Gilead, and also has demonstrated low nanomolar potency in vitro against both HSV-1 and HSV-2 clinical isolates and a favorable nonclinical safety profile in the FDA's GLP toxicology studies, with high safety margins and minimal potential for off-target effects.
Current wording
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. In addition, we are developing a second novel, potent, long-acting HPI for genital herpes, 1179, which was exclusively in-licensed to us as part of our collaboration with Gilead, and also has demonstrated low nanomolar potency in vitro against both HSV-1 and HSV-2 clinical isolates and a favorable nonclinical safety profile in the FDA's GLP toxicology studies.
Previous wording
In September 2024, we announced positive interim data for the Phase 1a portion of a Phase 1a/b clinical study of 5366, and in April 2025, we announced additional data for the Phase 1a portion of the study at the 2025 Congress of the European Society of Clinical Microbiology and Infectious Diseases. Interim results exceeded our objectives for this Phase 1a study and supported 5366’s progression into the Phase 1b portion of the study, 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.
Current wording
In September 2024, we announced positive interim data for the Phase 1a portion of a Phase 1a/b clinical study of 5366, and in April 2025, we announced additional data for the Phase 1a portion of the study at the 2025 Congress of the European Society of Clinical Microbiology and Infectious Diseases and an encore presentation at the STI & HIV World Congress in July 2025. Interim results exceeded our objectives for this Phase 1a study and supported 5366’s progression into the Phase 1b portion of the study, 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 are exploring both once-weekly and once-monthly oral dosing regimens in the Part B (Phase 1b) portion of the study.
Previous wording
In the Part A cohorts, 5366 has been well-tolerated with a favorable safety profile observed when administered orally up to 350 mg, with exposure of 70 to 98 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.
Current wording
In the Part A cohorts, 5366 has been well-tolerated with a favorable safety profile observed when administered orally up to 350 mg, with exposure up to 98 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.
Previous wording
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 pharmacokinetic (PK) and safety profile to date that is supportive of a potential long-acting treatment by once-weekly oral administration. We submitted the Clinical Trial Application 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.
Current wording
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 PK and safety profile to date that is supportive of a potential long-acting treatment by once-weekly oral administration. We submitted the Clinical Trial Application 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.
Previous wording
In all three single-dose Phase 1a cohorts completed to date (50 mg, 100 mg and 300 mg), 1179 has been well-tolerated with a favorable safety profile observed. Treatment-emergent AEs were generally Grade 1 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. A single, self-limited Grade 2 alanine transaminase (ALT) elevation was observed in a subject receiving the highest dose of 300 mg. There were no clinical significant ECG abnormalities, no significant treatment-related laboratory abnormalities and no protocol-defined stopping criteria were met. Plasma concentrations exceeded necessary protein-adjusted EC 50 for inhibition of HSV replication at all dose levels and the observed half-life of approximately four days supports weekly dosing, the target profile for 1179.
Current wording
In all three single-dose Phase 1a cohorts completed to date (50 mg, 100 mg and 300 mg), 1179 has been well-tolerated with a favorable safety profile observed. Treatment-emergent AEs were generally Grade 1 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. A single, self-limited Grade 2 alanine transaminase (ALT) elevation was observed in a subject receiving the highest dose of 300 mg. There were no clinically significant ECG abnormalities, no significant treatment-related laboratory abnormalities and no protocol-defined stopping criteria were met. Plasma concentrations exceeded necessary protein-adjusted EC 50 for inhibition of HSV replication at all dose levels and the observed half-life of approximately four days supports weekly dosing, the target profile for 1179.
Previous wording
The Phase 1b study of 1179 is ongoing concurrently with the ongoing Phase 1b evaluation of 5366, our other long-acting HPI candidate that began dosing in Phase 1b in the fourth quarter of 2024. The Phase 1b studies for 5366 and 1179 use equivalent eligibility criteria and outcome measures for both candidates. We plan to report interim data for both candidates no later than this fall 2025.
Current wording
The Phase 1b study of 1179 is ongoing concurrently with the ongoing Phase 1b evaluation of 5366, our other long-acting HPI candidate that began dosing in Phase 1b in the fourth quarter of 2024. Enrollment for two cohorts of the Phase 1b portion of the 1179 study is complete. We plan to report interim data on two cohorts of weekly dosing of 1179 and one cohort of monthly dosing of 5366 by the end of 2025, which are expected to be presented together once all virology analyses are completed. 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."
Previous wording
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, 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.
Current wording
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, only approximately 33 million, or 13%, of those chronically infected with HBV, 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.
Previous wording
The current standard of care for chronic HBV infection, nucleos(t)ide analog reverse transcriptase inhibitors (NrtIs), are taken life-long and reduce, but do not eliminate, the virus and result in very low cure rates. No new mechanisms of action (MOA) have been approved for the treatment of chronic HBV infection in over 25 years. The focus of our HBV program is to improve outcomes and increase the number of patients diagnosed and treated through the development of finite and curative therapies targeting an orthogonal MOA.
Current wording
The current standard of care for chronic HBV infection, nucleos(t)ide analog reverse transcriptase inhibitors (NrtIs), are taken life-long and reduce, but do not eliminate, the virus and result in very low cure rates. No new mechanisms of action (MOA) have been approved for the treatment of chronic HBV infection in over 25 years. The focus of our
Previous wording
At the European Association for the Study of the Liver's International Liver Congress TMin May 2025, 6250 was featured in a poster presentation highlighting nonclinical data supporting the advancement of 6250 into an ongoing Phase 1a clinical study, which was initiated during the fourth quarter of 2024.
Current wording
At the European Association for the Study of the Liver's International Liver Congress TMin May 2025 and an encore presentation at the 2025 International HBV meeting in September 2025, 6250 was featured in a poster presentation highlighting nonclinical data supporting the advancement of 6250 into an ongoing Phase 1a clinical study, which was initiated during the fourth quarter of 2024.
Previous wording
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.
Current wording
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.
Previous wording
HBV is a DNA virus that infects hepatocytes and establishes a reservoir of covalently closed circular DNA (cccDNA), a unique viral DNA moiety that resides in the nucleus of HBV-infected hepatocytes and is associated with viral persistence and chronic infection. No currently approved oral therapies target cccDNA activity directly. As a result, we have worked to discover and develop compounds targeting the core protein, a viral protein involved in numerous aspects of the HBV replication cycle, including the generation of HBV cccDNA.
Current wording
HBV is a DNA virus that infects hepatocytes and establishes a reservoir of covalently closed circular DNA (cccDNA), a unique viral DNA species that resides in the nucleus of HBV-infected hepatocytes and is associated with viral persistence and chronic infection. No currently approved oral therapies target cccDNA activity directly. As a result, we have worked to discover and develop compounds targeting the core protein, a viral protein involved in numerous aspects of the HBV replication cycle, including the generation of HBV cccDNA.
Previous wording
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 they are active against MOA #1, first-generation CAMs have not demonstrated adequate potency to sufficiently block cccDNA formation (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 they do so incompletely. The chemical scaffold of 4334 is novel and distinct from all our prior CAM candidates.
Current wording
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 they are active against MOA #1, first-generation CAMs have not demonstrated adequate potency to sufficiently block cccDNA formation (MOA #2). Further, the current standard of care, NrtIs, impacts the viral replication cycle after establishment of cccDNA and can only inhibit production of new viral particles, and they do so incompletely. The chemical scaffold of 4334 is novel and distinct from all our prior CAM candidates.
Previous wording
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 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 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 is expected to be presented at a future scientific conference.
Current wording
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 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 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 will be 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."
Previous wording
In December 2024, we nominated 7423 as our development candidate to undergo regulatory filing-enabling studies, which are ongoing.
Current wording
In December 2024, we nominated 7423, a prodrug, as our development candidate to undergo regulatory filing-enabling studies, which are ongoing. In October 2025, we transitioned our discovery and development from 7423 to nominate its parent molecule, 7272, which is currently in regulatory filing-enabling preclinical studies.
Previous wording
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 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, 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.
Current wording
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 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, 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 anniversaries of the collaboration.
Previous wording
Collaboration revenue was $19.0 million for the six months ended June 30, 2025 compared to $14.3 million for the same period in 2024. The $4.7 million increase in collaboration revenue was due to more costs incurred under the Gilead Collaboration Agreement during the six months ended June 30, 2025, as well as an increase in the transaction price from additional funds received under the First Amendment to the Gilead Collaboration Agreement.
Current wording
Collaboration revenue was $10.8 million for the three months ended September 30, 2025 compared to $6.8 million for the same period in 2024. The $3.9 million increase was primarily due to more costs incurred under the Gilead Collaboration Agreement during the three months ended September 30, 2025.
Previous wording
Collaboration revenue was $9.6 million for the three months ended June 30, 2025 compared to $8.5 million for the same period in 2024. The $1.1 million increase in collaboration revenue was due to more costs incurred under the Gilead Collaboration Agreement during the three months ended June 30, 2025, as well as an increase in the transaction price from additional funds received under the First Amendment to the Gilead Collaboration Agreement.
Current wording
Collaboration revenue was $29.8 million for the nine months ended September 30, 2025 compared to $21.2 million for the same period in 2024. The $8.7 million increase was due to more costs incurred under the Gilead Collaboration Agreement during the nine months ended September 30, 2025, as well as an increase in the transaction price from additional funds received under the First Amendment to the Gilead Collaboration Agreement.
Previous wording
Interest and other income, net was $0.9 million for the three months ended June 30, 2025, compared to $1.5 million for the same period in 2024. The $0.6 million decrease was primarily due to a smaller portfolio balance after using maturing investments to fund operations as well as lower interest rates during the three months ended June 30, 2025 as compared to the same period in 2024.
Current wording
Interest and other income, net was $3.7 million for the nine months ended September 30, 2025, compared to $4.5 million for the same period in 2024. The $0.7 million decrease was primarily due to a smaller portfolio balance for most of the period, as we used maturing investments to fund operations prior to our financing transaction in August 2025. Lower interest rates during the nine months ended September 30, 2025 compared to the same period in 2024 also contributed to the decrease.
Previous wording
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 June 30, 2025 principally through equity financings, raising an aggregate of $648.0 million in net proceeds, and strategic collaborations, raising an aggregate of $200.9 million.
Current wording
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 September 30, 2025 principally through equity financings, raising an aggregate of $821.8 million in net proceeds, and strategic collaborations, raising an aggregate of $200.9 million.
Previous wording
Cash Flows for the Six Months Ended June 30, 2025 and 2024
Current wording
Cash Flows for the Nine Months Ended September 30, 2025 and 2024
Previous wording
Net cash used in operating activities was $40.2 million for the six months ended June 30, 2025, compared to $35.5 million for the same period in 2024. The increase in cash used in operations was primarily attributable to increases in operating expenses from the advancement of our clinical pipeline, and the timing of vendor invoicing and payments.
Current wording
Net cash used in operating activities was $55.3 million for the nine months ended September 30, 2025, compared to $50.7 million for the same period in 2024. The increase in cash used in operations was primarily attributable to increases in operating expenses from the advancement of our clinical pipeline.
Previous wording
Net cash provided by investing activities was $23.6 million for the six months ended June 30, 2025, compared to $22.4 million for the same period in 2024. The increase was primarily due to higher proceeds from maturities of our marketable securities required by the increase in our overall expenses.
Current wording
Net cash used in investing activities was $134.7 million for the nine months ended September 30, 2025, compared to net cash provided by investing activities of $46.9 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.
Previous wording
Net cash provided by financing activities was $2.3 million for the six months ended June 30, 2025, compared to $12.5 million for the same period in 2024. The decrease primarily reflects lower proceeds from the sale of our common stock under "at-the-market" offerings during the six months ended June 30, 2025, as compared to the registered direct offering and a private placement to a related party in 2024.
Current wording
Net cash provided by financing activities was $174.2 million for the nine months ended September 30, 2025, compared to $12.5 million for the same period in 2024. The increase was due to larger proceeds from our financing in August 2025, and the subsequent exercise of warrants issued in that transaction, compared to our financing in June 2024.
Previous wording
We have generated significant losses to date, and we expect to continue to generate losses as we develop our product candidates. As of June 30, 2025, we had an accumulated deficit of $844.9 million. Because we do not generate revenue from any of our product candidates, our losses will continue as we further develop and seek regulatory approval for, and commercialize, our product candidates. We expect our future operating expenses to increase over the coming years as we continue to advance our candidates. As a result, our operating losses are likely to be substantial over the next several years 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.
Current wording
We have generated significant losses to date, and we expect to continue to generate losses as we develop our product candidates. As of September 30, 2025, we had an accumulated deficit of $854.1 million. Because we do not generate revenue from any of our product candidates, our losses will continue as we further develop and seek regulatory approval for, and commercialize, our product candidates. We expect our future operating expenses to increase over the coming years as we continue to advance our candidates. As a result, our operating losses are likely to be substantial over the next several years 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.
Previous wording
As of June 30, 2025, we held cash, cash equivalents and marketable securities of $75.0 million. Based on our current operating plan, we believe our existing cash, cash equivalents and marketable securities will be able to fund our operating requirements into the middle of 2026. However, 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.
Current wording
As of September 30, 2025, we held cash, cash equivalents and marketable securities of $232.6 million. Based on our current operating plan, we believe we have sufficient funds to meet our operating requirements into late 2027. This cash runway guidance does not include potential future payments to us under our collaboration with Gilead or from potential warrant exercises, which would further extend our cash runway beyond 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.
Rearranged current paragraphs (1)
Current report — wording carried from elsewhere
HBV program is to improve outcomes and increase the number of patients diagnosed and treated through the development of finite and curative therapies targeting an orthogonal MOA.