Biggest changeOur 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, market volatility and risk of recession; 45 • 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; • our ability to manufacture, and to contract with third parties to manufacture, adequate supplies of our product candidates for our clinical studies and any eventual commercialization; • the costs, timing and outcome of regulatory review of our product candidates; • 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; and • our ability to establish and maintain collaborations on favorable terms, if at all.
Biggest changeWe also enter into contracts in the normal course of business with CROs for clinical trials and CMOs for clinical supply manufacturing and with vendors for nonclinical research studies and other services and products for operating purposes, which generally provide for termination within 30 days of notice. 44 Our future capital requirements will depend on many factors, including: • 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; • our ability to raise capital despite macroeconomic and geopolitical events impacting financial markets, such as rising inflation, market volatility and risk of recession; • our ability to realize future potential benefits pursuant to the Gilead Collaboration and maintain the collaboration; • our ability to manufacture, and to contract with third parties to manufacture, adequate supplies of our product candidates for our clinical studies and any eventual commercialization; • the costs, timing and outcome of regulatory review of our product candidates; and • 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.
In addition, multiple contraindications limit its use, and it requires weekly injections that result in systemic exposure for up to a year. By focusing exposure on the liver, our investigational IFNAR agonist program aims to engage interferon-α’s validated antiviral and immune modulatory mechanisms, retaining the efficacy of IFN-α while reducing systemic exposure to improve tolerability.
In addition, multiple contraindications limit its use, and it requires weekly injections that result in systemic exposure for up to a year. By focusing exposure on the liver, our investigational IFNAR agonist program aims to engage IFN-α’s validated antiviral and immune modulatory mechanisms, retaining the efficacy of IFN-α while reducing systemic exposure to improve tolerability.
Our commercial revenues, if any, will 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.
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.
Item 7. Management’s Discussion and Analysis o f Financial Condition and Results of Operation The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our consolidated financial statements and the related notes thereto and other financial information appearing elsewhere in this Annual Report on Form 10-K.
Item 7. Management’s Discussion and Analysis o f Financial Condition and Results of Operations The following discussion and analysis of our financial condition and results of operations should be read in conjunction with our consolidated financial statements and the related notes thereto and other financial information appearing elsewhere in this Annual Report on Form 10-K.
Research and Development Expense 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.
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.
General and Administrative Expense General and administrative expenses consist primarily of salaries and other related costs for personnel in executive, finance, accounting, business development, information technology, legal and human resources functions.
General and Administrative Expenses General and administrative expenses consist primarily of salaries and other related costs for personnel in executive, finance, accounting, business development, information technology, legal and human resources functions.
Other significant costs include facility costs not otherwise included in research and development expenses, insurance costs, legal fees relating to patents and corporate matters and fees for accounting and consulting services.
Other 43 significant costs include facility costs not otherwise included in research and development expenses, insurance costs, legal fees relating to patents and corporate matters and fees for accounting and consulting services.
IFN-α is a subcutaneous injectable immune modularity therapy approved for HBV that has demonstrated functional cure in some HBV patients, but its poor tolerability profile significantly limits its use. Substantial side effects include flu-like symptoms, cytopenias, serious depression and psychiatric effects.
IFN-α is a subcutaneous injectable immune modulatory therapy approved for HBV that has demonstrated functional cure in some HBV patients, but its poor tolerability profile significantly limits its use. Substantial side effects include flu-like symptoms, cytopenias, serious depression and psychiatric effects.
Our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in our reporting changes in estimates in any particular period. Adjustments to prior period estimates have not been material for the years ended December 31, 2022 and 2021.
Our understanding of the status and timing of services performed relative to the actual status and timing of services performed may vary and may result in our reporting changes in estimates in any particular period. Adjustments to prior period estimates have not been material for the years ended December 31, 2023 and 2022.
To the extent that we raise additional capital through the sale of equity or convertible debt securities, 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.
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.
Examples of estimated amortized or accrued research and development expenses include fees to: • contract research organizations (CROs) and other service providers in connection with clinical studies; • contract manufacturing organizations (CMOs) in connection with the production of clinical trial materials; and • vendors in connection with preclinical development activities.
Examples of estimated amortized or accrued research and development expenses include fees to: • contract research organizations (CROs) and other service providers in connection with clinical studies; • contract manufacturing organizations (CMOs) in connection with the production of clinical trial materials; and • vendors in connection with nonclinical development activities.
No currently approved oral therapies target cccDNA activity directly, which makes molecules that can modulate cccDNA generation or disrupt its function highly sought in the HBV field. 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.
No currently approved oral therapies target cccDNA activity directly, which makes molecules that can modulate cccDNA generation or disrupt its function. 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.
These patients, which only comprise an estimated 4.5% of hepatitis B surface antigen (HBsAg) positive patients, experience a substantially increased disease burden, as they account for 18% of cirrhosis and 20% of hepatocellular carcinoma associated with HBV.
HDV affects a subset of approximately 12 million HBV infected patients. These patients, which comprise an estimated 4.5% of hepatitis B surface antigen (HBsAg) positive patients, experience a substantially increased disease burden, as they account for 18% of cirrhosis and 20% of hepatocellular carcinoma associated with HBV.
Transplant-Associated Herpesviruses In a transplant setting, when patients are experiencing immunosuppression, they are at high risk of uncontrolled viral replication and severe disease brought on by one or more members of the herpesvirus family of viruses including cytomegalovirus (CMV), herpes simplex virus type 1, HSV-2 and varicella zoster virus (VZV).
In a transplant setting, when patients are experiencing immunosuppression, they are at high risk of uncontrolled viral replication and severe disease brought on by one or more herpesviruses, including cytomegalovirus (CMV), HSV-1, HSV-2 and varicella zoster virus (VZV).
We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for patients living with HDV.
We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for patients living with HDV, which face a significant and immediate disease burden.
Each of these herpesviruses are highly prevalent, as approximately (1) 60% of the population is CMV-positive; (2) 60% of the population is HSV-positive; and (3) 80% of the population is VZV-positive. These viruses establish lifelong latent infections and frequently reactivate in transplant patients due to immune suppression.
Each of these herpesviruses are highly prevalent, as approximately (1) 60% of transplant patients are CMV-positive; (2) 60% of transplant patients are HSV-positive; and (3) 80% of transplant patients are VZV-positive. These viruses establish lifelong latent infections and frequently reactivate in transplant patients due to the use of immunosuppressive drugs following the transplant.
The following table summarizes the period-over-period changes in our interest and other income, net (in thousands, except for percentages): Year Ended December 31, $ Change % Change 2022 2021 2022 vs. 2021 2022 vs. 2021 Interest and other income, net $ 1,022 $ 302 $ 720 238 % 44 Interest and other income, net was $1.0 million for the year ended December 31, 2022, compared to $0.3 million for the year ended December 31, 2021.
The following table summarizes the period-over-period changes in our interest and other income, net (in thousands, except for percentages): Year Ended December 31, $ Change % Change 2023 2022 2023 vs. 2022 2023 vs. 2022 Interest and other income, net $ 3,451 $ 1,022 $ 2,429 238 % Interest and other income, net was $3.5 million for the year ended December 31, 2023, compared to $1.0 million for the year ended December 31, 2022.
Net cash provided by investing activities for the year ended December 31, 2021 was $26.5 million. This was due to proceeds of $27.3 million from sales and maturities of marketable securities, net of purchases, and proceeds of $1.5 million from the sale of Microbiome assets.
Net cash provided by investing activities for the year ended December 31, 2022 was $90.6 million. This was due to proceeds of $89.2 million from sales and maturities of marketable securities, net of purchases, and proceeds of $1.5 million received in 2022 from the sale of Microbiome assets in 2021.
Of the 296 million people living with chronic HBV infection as of 2019, only approximately 30 million were aware of their infection, and only approximately 6.6 million of those diagnosed received treatment.
Of the 296 million people living with chronic HBV infection, only approximately 30.4 million, or 10.5%, were aware of their infection, and only approximately 6.6 million, or 22%, of those diagnosed received treatment.
A benchmark for therapeutic agents aiming to decrease cccDNA levels is the use of several key viral antigens as surrogate biomarkers of active cccDNA. The same biomarkers can be used in both primary human hepatocyte cells and patients. On this basis, our CIs have shown preclinical proof of principle.
A benchmark for therapeutic agents aiming to decrease cccDNA levels is the use of several key viral antigens as surrogate biomarkers of active cccDNA. The same biomarkers can be used in both primary human hepatocytes and patients. On this basis, our next-generation CAM, ABI-4334 (4334), has shown nonclinical proof of principle.
Our HBV and HDV Programs The World Health Organization (WHO) estimates that 296 million people worldwide are chronically infected with HBV as of 2019, and 1.5 million new infections occur each year.
GLP toxicology studies are underway and clinical studies are expected to begin by the end of 2024. Our HBV and HDV Programs The World Health Organization (WHO) estimates that 296 million people worldwide are chronically infected with HBV as of 2019, and 1.5 million new infections occur each year.
HBV/HDV Entry Inhibitor In March 2022, we announced our research program focused on a novel, orally bioavailable small molecule approach to inhibit entry of HBV and HDV.
In March 2022, we announced our research program focused on a novel, orally bioavailable small molecule approach to inhibit entry of HBV and HDV by targeting NTCP, and in September 2023, we nominated ABI-6250 (6250).
This was primarily due to our net loss of $93.1 million, adjusted for $6.6 million recognized for stock-based compensation expense. Net cash used in operating activities was $93.4 million for the year ended December 31, 2021.
This was primarily due to our net loss of $93.1 million, adjusted for $6.6 million recognized for stock-based compensation expense. 45 Investing Activities Net cash used in investing activities for the year ended December 31, 2023 was $69.1 million primarily due to purchases of marketable securities, net of maturities.
In a variety of cell culture models, CIs have demonstrated the ability to reduce production of viral HBV DNA levels as well as the surrogate markers for cccDNA establishment: HBV e antigen (HBeAg), HBV core-related antigen (HBcrAg) and viral pre-genomic RNA (pgRNA). Our research and development organizations are advancing next-generation CIs through clinical development.
In a variety of cell culture models, 4334 has demonstrated the ability to reduce production of viral HBV DNA levels as 37 well as the surrogate markers for cccDNA establishment: HBV e antigen (HBeAg), HBV core-related antigen (HBcrAg) and viral pre-genomic RNA (pgRNA).
The following table summarizes the period-over-period change in our general and administrative expenses (in thousands, except for percentages): Year Ended December 31, $ Change % Change 2022 2021 2022 vs. 2021 2022 vs. 2021 General and administrative expenses $ 24,134 $ 28,780 $ (4,646 ) (16 %) General and administrative expenses were $24.1 million for the year ended December 31, 2022, compared to $28.8 million for the year ended December 31, 2021.
The following table summarizes the period-over-period change in our general and administrative expenses (in thousands, except for percentages): Year Ended December 31, $ Change % Change 2023 2022 2023 vs. 2022 2023 vs. 2022 General and administrative expenses $ 22,909 $ 24,134 $ (1,225 ) (5 %) General and administrative expenses were $22.9 million for the year ended December 31, 2023, compared to $24.1 million for the year ended December 31, 2022.
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 is considered the most severe form of hepatitis, as 70% of HDV patients progress to cirrhosis within ten years. While HDV is less prevalent in the United States, it is a significant and serious health problem with inadequate treatment in many parts of Europe, Africa, the Middle East, East Asia and parts of South America.
As of December 31, 2022, we had an accumulated deficit of $724.5 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.
As of December 31, 2023, we had an accumulated deficit of $785.7 million primarily as a result of research 40 and development expenses and general and administrative expenses. 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.
If we are unable to raise additional funds through equity or debt financings when needed, we may be required to delay, limit, reduce or terminate our product development or future commercialization efforts or grant rights to develop and market product candidates that we would otherwise prefer to develop and market ourselves.
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.
Critical Accounting Estimates Our management’s discussion and analysis of our financial condition and results of operations is based on our consolidated financial statements, which we have prepared in accordance with accounting principles generally accepted in the United States.
We are unable to predict the extent of any future losses or when we will become profitable, if at all. Critical Accounting Estimates Our management’s discussion and analysis of our financial condition and results of operations is based on our consolidated financial statements, which we have prepared in accordance with accounting principles generally accepted in the United States.
Net Cash Provided by Financing Activities Net cash provided by financing activities for the year ended December 31, 2022 was $0.6 million resulting from the net proceeds of $0.3 million from the sale of 300,827 shares of our common stock under the 2020 ATM and $0.3 million from the issuance of 225,832 shares of common stock under the Assembly Biosciences Amended and Restated 2018 Employee Stock Purchase Plan (2018 ESPP).
Net cash provided by financing activities for the year ended December 31, 2022 was $0.6 million resulting from the net proceeds of $0.3 million from the sale of 25,068 shares of our common stock under the 2020 ATM and $0.3 million from the issuance of 18,819 shares of common stock under the 2018 ESPP. 46 Item 7A.
As a result of these limitations, we identified an opportunity to develop an oral pan-herpes NNPI for these transplant-associated herpesvirus infections, which would greatly simplify treatment. Our research team has discovered multiple series of potent, broad-spectrum herpesvirus polymerase inhibitors.
However, currently approved antivirals are not broad spectrum 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 pan-herpes NNPI for these transplant-associated herpesvirus infections, which could greatly advance treatment. Our research team has discovered multiple chemical series of potent, broad-spectrum herpesvirus polymerase inhibitors.
As a result, our operating losses are likely to be substantial over the next several years as we continue the development of our product candidates and thereafter if none are 39 approved or successfully launched. We are unable to predict the extent of any future losses or when we will become profitable, if at all.
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.
Core Inhibitors 35 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 cell nucleus of HBV-infected hepatocytes and is associated with viral persistence and chronic infection.
We expect to initiate Phase 1a clinical studies of 6250 by the end of 2024. Capsid Assembly Modulator 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.
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.
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. 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.
These license agreements may also include contingent consideration in the form of cash payments to be made for future milestone events. We assess whether such contingent consideration meets the definition of a derivative and to date we have determined that such contingent consideration are not derivatives.
These license agreements may also include contingent consideration in the form of cash payments to be made for future milestone events.
We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for patients living with HDV. Our research team has identified a potential opportunity to develop a safe and effective oral small molecule viral entry inhibitor, which could significantly improve convenience and potentially enhance treatment uptake and diagnosis rates.
We believe a safe and effective oral small molecule entry inhibitor would be a significant innovation for patients living with HDV and could significantly improve treatment uptake and diagnosis rates, especially when compared with currently available injectable products.
HBV is a highly prevalent disease that infects more than three times the number of people infected with hepatitis C virus and HIV infections combined, according to the WHO, and has a higher morbidity and mortality rate.
HBV is a highly prevalent disease that infects more than three times the number of people infected with hepatitis C virus and HIV infections combined, according to the WHO. HDV is a “satellite virus,” because it can only infect people (1) who are already infected with HBV or (2) at the same time as a person is infected with HBV.
Operations We currently have corporate and administrative offices and research laboratory space in South San Francisco, California as well as registrational offices, but no employees, in China.
The termination of the License Agreement will be effective on April 11, 2024, 90 days following the delivery of the termination notice. Operations We currently have corporate and administrative offices and research laboratory space in South San Francisco, California as well as a registrational office, but no employees, in China.
The increase of $0.7 million was primarily due to more interest income earned on marketable securities caused by multiple interest rate increases in 2022.
The increase of $2.4 million was primarily due to more interest income earned on marketable securities caused by multiple interest rate increases in 2023 and a larger portfolio balance after the receipt of $100.0 million upon entering into the Gilead Collaboration in October 2023.
Cash Flows A summary of our cash flows for the periods presented was as follows (in thousands): Year Ended December 31, 2022 2021 Operating activities $ (84,463 ) $ (93,396 ) Investing activities 90,640 26,515 Financing activities 614 53,064 Net increase (decrease) in cash and cash equivalents $ 6,791 $ (13,817 ) Net Cash Used in Operating Activities Net cash used in operating activities was $84.5 million for the year ended December 31, 2022.
Cash Flows The following table summarizes our cash flows for the periods presented (in thousands): Year Ended December 31, 2023 2022 Operating activities $ 22,743 $ (84,463 ) Investing activities (69,138 ) 90,640 Financing activities 13,818 614 Net (decrease) increase in cash and cash equivalents $ (32,577 ) $ 6,791 Operating Activities Net cash provided by operating activities was $22.7 million for the year ended December 31, 2023.
From time to time, we opportunistically raise capital and have done so numerous times since our initial public offering by issuing equity securities. We expect to continue to raise capital when and as needed and at the time and in the manner most advantageous to us.
We monitor our cash needs and the status of the capital markets on a continuous basis. From time to time, we opportunistically raise capital and have done so numerous times since our initial public offering by issuing equity securities.
Research and Development Expense and Accruals As part of the process of preparing our consolidated financial statements, we are required to estimate certain research and development expenses.
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. Research and Development Expense and Accruals As part of the process of preparing our consolidated financial statements, we are required to estimate certain research and development expenses.
These candidates, which exhibit multiple MOAs, have been optimized to potently disrupt both viral replication (MOA #1) and, importantly, prevent the establishment and replenishment of new cccDNA (MOA #2). cccDNA is the viral reservoir that drives HBV’s life-long persistence in patients. First-generation CIs have not demonstrated adequate potency to sufficiently block its formation.
As a next-generation CAM, 4334 has been 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).
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 IFN-α injected weekly or, in some regions, a large, complex molecule that requires daily injections.
The current standard of care treatment for HDV is off-label pegylated IFN-α injected weekly or, in some regions, a large, complex molecule that requires daily injections. There are no approved HDV treatments in the United States, and there is only one approved HDV treatment in Europe.
This resulted in the entire write-off of our goodwill and IPR&D asset of $12.6 million and $29.0 million, respectively. Interest and Other Income, Net Interest income consists of interest earned on our cash and cash equivalents and available-for-sale securities.
Interest and Other Income, Net Interest income consists of interest earned on our cash and cash equivalents and available-for-sale securities.
We believe that 4334 has a best-in-class preclinical profile, with single-digit nanomolar potency 37 against the production of new virus and the formation of cccDNA. Preclinically to date, 4334 has also demonstrated pan-genotypic activity, an improved resistance profile and a favorable safety profile. Preclinical characterization of 4334 was shared in a poster presentation at AASLD in November 2021.
We believe that 4334 has a best-in-class nonclinical profile, with single-digit nanomolar potency against MOA #1 and MOA #2, pan-genotypic activity, an improved resistance profile and a favorable safety profile.
The following table summarizes the period-over-period changes in our research and development expenses (in thousands, except for percentages): Year Ended December 31, $ Change % Change 2022 2021 2022 vs. 2021 2022 vs. 2021 External expenses: Research and discovery $ 10,338 $ 6,274 4,064 65 % 3733 8,165 2,335 5,830 250 % VBR 6,962 16,012 (9,050 ) (57 %) 4334 5,195 2,796 2,399 86 % 2158 2,440 9,916 (7,476 ) (75 %) Microbiome — (2,579 ) (1) 2,579 (100 %) Total external expenses 33,100 34,754 (1,654 ) (5 %) Employee and contractor-related expenses 31,052 26,423 4,629 18 % Facility and other expenses 5,828 7,347 (1,519 ) (21 %) Total research and development expenses $ 69,980 $ 68,524 $ 1,456 2 % (1) Microbiome external expenses in 2021 include a $3.0 million gain on the sale of Microbiome assets.
The following table summarizes the period-over-period changes in our research and development expenses (in thousands, except for percentages): Year Ended December 31, $ Change % Change 2023 2022 2023 vs. 2022 2023 vs. 2022 External expenses: Research and discovery $ 9,741 $ 10,338 $ (597 ) (6 %) 3733 3,383 8,165 (4,782 ) (59 %) 5366 2,869 — 2,869 100 % 4334 1,947 5,195 (3,248 ) (63 %) VBR 1,755 6,962 (5,207 ) (75 %) 6250 421 — 421 100 % 2158 226 2,440 (2,214 ) (91 %) Total external expenses 20,342 33,100 (12,758 ) (39 %) Employee and contractor-related expenses 22,956 31,052 (8,096 ) (26 %) Facility and other expenses 5,602 5,828 (226 ) (4 %) Total research and development expenses $ 48,900 $ 69,980 $ (21,080 ) (30 %) Research and development expenses were $48.9 million for the year ended December 31, 2023 compared to $70.0 million for the year ended December 31, 2022.
Net cash provided by financing activities for the year ended December 31, 2021 was $53.1 million resulting from the net proceeds of $52.8 million from the sale of 11,234,207 shares of our common stock under the 2020 ATM and $0.3 million from the issuance of 88,820 shares of common stock under the 2018 ESPP. 47 Item 7A.
Financing Activities Net cash provided by financing activities for the year ended December 31, 2023 was $13.8 million resulting from the net proceeds of $9.1 million from the sale of 1,089,472 shares of our common stock in accordance with the Gilead Equity Agreements, $4.5 million from the sale of 261,170 shares of our common stock under our "at-the-market" offering program (the 2020 ATM) and $0.1 million from the issuance of 14,453 shares of common stock under the Assembly Biosciences Amended and Restated 2018 Employee Stock Purchase Plan (2018 ESPP).
Collaboration revenue for the year ended December 31, 2021 consists of the recognition of deferred revenue allocated to 2158 under our collaboration agreement with BeiGene, Ltd. (the BeiGene Agreement) upon discontinuing development of 2158.
Additionally, collaboration revenue includes the recognition of $2.7 million of deferred revenue allocated to 3733 under the BeiGene Agreement upon discontinuing development of 3733, following entering into the Gilead Collaboration, as we prioritize 4334. There was no revenue for the year ended December 31, 2022.
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. We are also progressing two programs with potential application against HDV.
No new mechanisms of action (MOA) have been approved for 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.
They inhibit the viral protein complex consisting of helicase, primase, and cofactor subunits, which have functions that are essential for viral DNA replication. These agents are not nucleoside analogues and do not require phosphorylation by the HSV thymidine kinase (TK) to become active drugs; therefore, helicase-primase inhibitors are active immediately upon reactivation of latent HSV.
Unlike nucleoside analogs, these compounds do not require phosphorylation by the HSV thymidine kinase (TK) and ongoing viral replication to become active drugs. As a result, HPIs are active immediately upon reactivation of latent HSV-1 and HSV-2. Furthermore, HPIs are active 35 against TK-deficient HSV-1 and HSV-2, which is a major mechanism of resistance to nucleoside analogs.
We expect our existing cash, cash equivalents and marketable securities will enable us to fund our operating expenses and capital expenditure requirements for at least the next twelve months. Our contractual obligations include operating lease obligations totaling $3.5 million as of December 31, 2022, of which $3.4 million are short-term.
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 operating expenses and capital expenditure requirements into the second half of 2025.
Comparison of the Years Ended December 31, 2022 and 2021 Collaboration Revenue The following table summarizes the period-over-period changes in our collaboration revenue (in thousands, except for percentages): Year Ended December 31, $ Change % Change 2022 2021 2022 vs. 2021 2022 vs. 2021 Collaboration revenue $ — $ 6,254 $ (6,254 ) (100 %) There was no collaboration revenue for the year ended December 31, 2022.
We assess whether such contingent consideration meets the definition of a derivative and to date we have determined that such contingent consideration are not derivatives. 42 Results of Operations Comparison of the Years Ended December 31, 2023 and 2022 Collaboration Revenue The following table summarizes the period-over-period changes in our collaboration revenue (in thousands, except for percentages): Year Ended December 31, $ Change % Change 2023 2022 2023 vs. 2022 2023 vs. 2022 Collaboration revenue $ 7,163 $ — $ 7,163 100 % Collaboration revenue for the year ended December 31, 2023 includes the recognition of $4.4 million for services performed under the Gilead Collaboration Agreement entered into in October 2023.
These uncontrolled viral infections increase risk of serious complications, including organ rejection and death. As with HSV-2, there are approved antivirals that are administered in a transplant setting, but they are limited by a narrow spectrum (no approved drug is effective against all of the herpesviruses indicated above), potentially serious side effects and significant drug-drug interactions.
These uncontrolled viral infections increase the risk of severe disease and serious complications, including organ rejection, graft loss and death, and impacted approximately 60,000 patients in 2018 in the United States and EU4/UK. While there are approved antivirals that are administered in a transplant setting.
The current standard of care for chronic HBV infection, NrtIs, are taken life-long and reduce, but do not eliminate, the virus and result in very low cure rates, leaving an enormous unmet need. No new mechanisms of action (MOA) have been approved for chronic HBV infection in over 25 years.
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. 36 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.
Based on current progress, our aim is to nominate a product candidate for development in 2023. At AASLD 2022, we presented the preclinical characterization of our novel class of highly potent small molecule HBV/HDV entry inhibitors.
At the European Association for the Study of the Liver's (EASL) International Liver Congress TM in June 2023 and the International HBV Meeting in September 2023, we presented nonclinical characterization of the potencies and properties of our novel class of highly potent, small molecule, orally-bioavailable entry inhibitors.
This was primarily due to our net loss of $129.9 million, which included the recognition of $41.6 million in non-cash charges for the impairment of our goodwill and indefinite-lived intangible asset and $6.3 million in collaboration revenue from deferred revenue allocated to 2158 under the BeiGene Agreement upon discontinuing development of 2158. 46 Net Cash Provided by Investing Activities Net cash provided by investing activities for the year ended December 31, 2022 was $90.6 million due to proceeds of $89.2 million from sales and maturities of marketable securities, net of purchases, and proceeds of $1.5 million received in 2022 from the sale of Microbiome assets in 2021.
This was primarily due to proceeds of $90.7 million from the upfront payment under the Gilead Collaboration Agreement. This was partially offset by our net loss of $61.2 million, adjusted for $5.1 million recognized for stock-based compensation expense. Net cash used in operating activities was $84.5 million for the year ended December 31, 2022.