Glecaprevir/Pibrentasvir

Discovery described as a “fundamental shift in antiviral drug development” by an expert peer reviewer; serves as the basis for an armamentarium of broad-spectrum, direct-acting antivirals. SAN DIEGO — Model Medicines , an AI-first biotechnology company developing first-in-class therapeutics against multi-indication biological choke points, today announced the publication of a manuscript that establishes the RNA-dependent RNA polymerase (RdRp) Thumb-1 pocket as a conserved, druggable target for broad-spectrum antiviral development. The Thumb-1 pocket is a cryptic, allosteric site on the viral RdRp that controls an essential conformational change required for polymerase initiation. Pharmaceutical engagement traps the viral polymerase in a catalytically incompetent state, inhibiting replication. “The scientific literature states that conserved, druggable, allosteric viral biology targets do not exist,” said Daniel Haders, PhD, Founder and CEO of Model Medicines. “The broad-spectrum RdRp Thumb-1 pocket disproves decades of dogma that has influenced and continues to influence every antiviral drug program. We discovered a target the field dismissed as impossible. We did this by methodically developing a platform that allows us to do the tedious work of target discovery that others will not do or cannot do.” The preprint, “The RdRp Thumb-1 Pocket is a Conserved Target for Broad-Spectrum Antiviral Development,” is available on bioRxiv . It is accompanied by a companion preprint reporting preclinical proof of concept for MDL-001, the company’s oral, direct-acting antiviral discovered against this target. Model Medicines has been invited to present the RdRp Thumb-1 findings at IDWeek 2026 this October in Washington, D.C. “This is a highly innovative and mechanistically compelling abstract with strong novelty and potential significance for antiviral drug development,” said an IDWeek 2026 expert peer reviewer. “Demonstrates conservation of an allosteric site across viral families, directly contradicting established belief that non-nucleoside antivirals cannot achieve broad-spectrum activity. This is a fundamental shift in antiviral drug development strategy.” Model Medicines has now presented the discovery of the RdRp Thumb-1 site at IDWeek 2025 [1] , AASLD 2025 [2] , HepDART 2025 [3] , CROI 2026 [4] , ESCMID Global 2026 [5] , SERVC 2026 [6] , EASL 2026 [7] , and ASV 2026 [8] . The MDL-001 preprint has also been featured in the recent launch of the Intercept Fund , a $500 million philanthropic initiative, backed by leaders across technology and global health, including Stripe, Anthropic, the OpenAI Foundation, Jane Street, and the Flu Lab. [9] The World Is No Better Prepared for the Next Pandemic Than the Last RNA virus pandemics and epidemics occur regularly and cause widespread death and economic devastation. In the last 25 years, humanity has endured at least six major viral outbreaks: West Nile virus, SARS-CoV-1, swine-origin H1N1 influenza, MERS-CoV, Ebola, and COVID-19. [10] The COVID-19 pandemic caused an estimated 14.8 million deaths, resulted in $13.8 trillion in cumulative economic losses, and pushed 97 million people into extreme poverty. [11] [12] [13] Beyond the threat of the next pandemic, the annual toll is significant. Each winter, clinicians face a recurring tripledemic of influenza, RSV, and SARS-CoV-2 that causes hundreds of millions of infections and hundreds of thousands of deaths worldwide every year. [14] In a non-pandemic year in the U.S. alone, adults experience two to six of these respiratory viral illnesses and children approximately six to eight, at an economic cost exceeding $100 billion. [15] [16] A Parallel Crisis in the Liver and a Different Kind of Need Chronic viral hepatitis is a health crisis of comparable scale. Hepatitis B and C infections persist in 254 million and 50 million people worldwide, respectively. [17] An estimated 12–72 million people also carry hepatitis D, a satellite virus that cannot replicate without hepatitis B. [18] It is estimated that 5–15 million carry both HCV and HBV at once, yet most will never be diagnosed. Only 13% of HBV infections and 36% of HCV infections are identified globally, and fewer than 1% of co-infected patients know their status. Co-infection is not merely additive. Patients carrying both viruses are over 100-fold more likely to develop hepatocellular carcinoma than uninfected individuals. [19] Compounding the danger, every FDA-approved HCV direct-acting antiviral (DAA) carries a black box warning for the risk of hepatitis B virus (HBV) reactivation in patients with current or prior HBV infection. This reactivation can lead to fulminant hepatitis, liver failure, or death. [20] This FDA-mandated warning, added in 2016, applies to all DAA regimens, such as Epclusa, Harvoni, Mavyret, and others. Together, these gaps point to a single, persistent, and largely unaddressed need: one oral agent with broad-spectrum, direct-acting activity across the viruses that drive both crises. A Conserved Target Hidden in Plain Sight Conventional wisdom held that allosteric sites on viral polymerases are too poorly conserved to support pharmaceutical engagement beyond genotype- or species-specific activity. [21] Beclabuvir, the only approved Thumb-1 inhibitor, was developed for hepatitis C and is inactive against a diverse panel of non-HCV viruses, including poliovirus, rhinovirus, coronavirus, coxsackievirus, influenza, and HIV. [22] The Thumb-1 pocket had gone unrecognized because it is cryptic, and Beclabuvir MoA and activity data were misinterpreted. Beclabuvir’s lack of activity across viruses led to the conclusion that the pocket either did not exist or was undruggable on other viruses. This conclusion was seemingly validated because in the polymerase’s resting state the viral Λ1-loop occupies the site, rendering it invisible to conventional virtual screening. Model Medicines followed biology, rather than human dogma. Model Medicines' structural biology agent identified the pocket in viruses beyond HCV. The company then analyzed published HCV inhibitor co-crystal structures to define a fifteen-residue consensus Thumb-1 pocket. Model Medicines then aligned those residues across six coronaviruses spanning both Alphacoronavirus and Betacoronavirus genera to demonstrate that the pocket and its associated Λ1-loop are conserved across RNA viral families. Following the Science to a Novel Drug Class Model Medicines used the molecular-geometric deep-learning model, ChemPrint TM , within its peer-reviewed [23] , experimentally validated GALILEO™ drug discovery platform to find chemistry capable of engaging Thumb-1 across viral families. The company assembled a proprietary, three-tier bioactivity dataset spanning explicit HCV Thumb-1 chemistry and cross-family inhibitor scaffolds, then trained its model to separate HCV-restricted chemistry from genuinely broad-spectrum chemistry. In an accompanying preprint , Model Medicines demonstrates that MDL-001 inhibits Influenza, Coronaviruses, RSV, HCV, HBV, and HDV. MDL-001 is the first Thumb-1 inhibitor demonstrated to cross viral families. These findings establish RdRp Thumb-1 as both a conserved allosteric pocket and a druggable target built to yield successive generations of broad-spectrum, pandemic-ready therapeutics. The Discovery of Novel Druggable Targets is Rare in Virology Prior broad-spectrum drug discovery programs focused on developing nucleoside/nucleotide therapeutics that directly target the viral polymerase active site or host-targeted antivirals. None of the compounds active against these target classes have achieved broad-spectrum FDA approvals for Universal Influenza-like-Illness (ILI) or Universal Chronic Hepatitis. Few recently approved direct-acting antivirals act through clearly new target classes. Notable examples include baloxavir, an influenza cap-dependent endonuclease inhibitor, and lenacapavir, an HIV capsid inhibitor. [24] [25] RdRp Thumb-1 adds a new, broad-spectrum target to that short and commercially significant list. A New Blueprint for Drug Discovery Model Medicines broke with existing drug development paradigms to discover RdRp Thumb-1. In structure-based design, molecules are docked into a target's resolved 3D structure. This method would have failed to detect RdRp Thumb-1, because its pocket is cryptic and remains closed in the polymerase’s resting state. Conversely, similarity-based ligand approaches rank molecules by similarity to known actives and look for close chemical relatives. This method would have failed to discover broad-spectrum RdRp Thumb-1 inhibitors because the search would have kept returning the same narrow HCV-specific chemistry. To discover RdRp Thumb-1, Model Medicines fused the two paradigms. To establish the biology, the team overlaid crystal structures of the HCV RdRp Thumb-1 pocket bound to inhibitors and compared the polymerase across many viral families. This comparison confirmed that the pocket is conserved. The team then ran molecular-dynamics simulations to show how a bound drug displaces the Λ1-loop. To find the chemistry, the team used its GALILEO™ AI engine to train a geometry-aware deep-learning model on a proprietary dataset of small molecules. The model learned the features that make a molecule broad-spectrum rather than the features tied to any single virus. It identified the chemistry responsible for broad-spectrum interaction with the RdRp Thumb-1 pocket. About Model Medicines Model Medicines is an AI-first biotechnology company engineering first-in-class small molecules that target the biological linchpins underlying disease. The company’s research spans infectious disease, oncology, and inflammation, with programs designed around conserved molecular choke points that drive multiple pathologies. Model Medicines has discovered a direct-acting, non-nucleoside, broad-spectrum antiviral (MDL-001) and a potent, selective, and novel BRD4 inhibitor (MDL-4102). Its work demonstrates how large-scale computation can uncover entirely new classes of drugs once thought unreachable. Model Medicines is advancing a new generation of therapeutics that redefine what is possible in modern drug discovery. Learn more at . Media & Investor Contact Patrick O’Neill Head of Partnerships & Investor Relations media@modelmedicines.com [1] MDL-001: A Broad-Spectrum Antiviral Targeting the Thumb-1 Domain of Viral Polymerases, Open Forum Infectious Diseases, Volume 13, Issue Supplement_1, January 2026, ofaf695.084, [2] MDL-001 As A Next Generation HCV Thumb-1 inhibitor With Clinical-Stage Safety, The Liver Meeting: 2025 Abstracts. (2025). Hepatology (Baltimore, Md.), 82(S1), S1–S2308. Abstract 0088. [3] Oral Thumb-1 polymerase inhibitor MDL-001 achieves preclinical HCV and HBV proof-of-concept, including HCV/HBV co-infection and equivalence to sofosbuvir. Paper presented at: HEPDART 2025; December 7–11, 2025 [4] MDL-001, a novel oral thumb-1 polymerase inhibitor, shows efficacy in HCV/HBV in vitro and in vivo. Paper presented at: Conference on Retroviruses and Opportunistic Infections (CROI); February 22–25, 2026; Denver, CO. Abstract 589. / [5] MDL-001, an oral direct-acting Thumb-1 polymerase inhibitor, demonstrates broad-spectrum activity against influenza viruses, respiratory syncytial virus, and SARS-CoV-2 with oral proof-of-concept in mice. Abstract presented at: ESCMID Global 2026; April 18, 2026; Munich, Germany. Abstract 5803 MDL-001, an oral direct-acting Thumb-1 polymerase inhibitor, demonstrates single-agent efficacy against HCV/HBV co-infection in vitro, and achieves HCV and HBV preclinical proof-of-concept. Abstract presented at: ESCMID Global 2026; April 18, 2026; Munich, Germany. Abstract 5778. [6] MDL-001, an oral direct-acting Thumb-1 polymerase inhibitor, demonstrates broad-spectrum activity against influenza viruses, respiratory syncytial virus, and SARS-CoV-2 with oral proof-of-concept in mice. Paper presented at: the 18th Southeastern Regional Virology Conference (SERVC 2026), April 24–26, 2026 [7] MDL-001, an oral direct-acting Thumb-1 polymerase inhibitor, demonstrates efficacy against HCV/HBV co-infection in vitro, and achieves HCV and HBV preclinical proof-of-concept, including equivalence to sofosbuvir, Journal of Hepatology, Volume 84, Supplement 1, May 2026, Pages S877-S878, THU-580. (26)02352-4/abstract [8] MDL-001, an oral Thumb-1 polymerase inhibitor, demonstrates broad-spectrum antiviral activity across six viral families with oral in vivo proof-of-concept. Paper presented at: the 45th Annual Meeting of the American Society for Virology (ASV 2026), July 27–30, 2026 [9] Ransohoff, N., Petty, C., & Sok, D. (2026, June 24). Ending respiratory infections. Intercept. [10] Tian L, Qiang T, Liang C, et al. RNA-dependent RNA polymerase (RdRp) inhibitors: the current landscape and repurposing for the COVID-19 pandemic. Eur J Med Chem. 2021;213:113201. [11] Msemburi W, Karlinsky A, Knutson V, et al. The WHO estimates of excess mortality associated with the COVID-19 pandemic. Nature. 2023;613:130-137. [12] Gopinath, G. (2022, January 25). A disrupted global recovery. IMF Blog. [13] World Bank. Poverty and Shared Prosperity 2020: Reversals of Fortune. Washington, DC: World Bank; 2020. [14] Luong QXT, Hoang PT, Ho PT, Ayun RQ, Lee TK, Lee S. Potential broad-spectrum antiviral agents: a key arsenal against newly emerging and reemerging respiratory RNA viruses. Int J Mol Sci. 2025;26:1481. [15] Rossignol JF. Rethinking methods used to evaluate effectiveness of therapeutics for COVID-19 and other viral respiratory illnesses. Future Virol. 2022;17:67-69. [16] Hanage, W. P., & Schaffner, W. (2025). Burden of Acute Respiratory Infections Caused by Influenza Virus, Respiratory Syncytial Virus, and SARS-CoV-2 with Consideration of Older Adults: A Narrative Review. Infectious diseases and therapy, 14(Suppl 1), 5–37. [17] World Health Organization. Global hepatitis report 2024: action for access in low- and middle-income countries. Geneva: WHO; 2024. [18] 8. Negro F, Lok AS. Hepatitis D: A Review. JAMA. 2023;330(24):2376-2387. [19] Mavilia MG, Wu GY. HBV-HCV coinfection: viral interactions, management, and viral reactivation. J Clin Transl Hepatol. 2018;6:296-305. [20] U.S. Food and Drug Administration. FDA Drug Safety Communication: FDA warns about risk of hepatitis B reactivating in some patients treated with certain direct-acting antiviral medicines for hepatitis C (DAAs). Silver Spring (MD): FDA; 2016 Oct. [21] De Clercq E. Strategies in the design of antiviral drugs. Nat Rev Drug Discov. 2002;1:13-25. [22] Gentles RG. Discovery of beclabuvir: a potent allosteric inhibitor of the hepatitis C virus polymerase. Top Med Chem. 2019;31:193-228. [23] Umansky TJ, Woods VA, Russell SM, Haders DJ. AmesNet: a task-conditioned deep learning model with enhanced sensitivity and generalization in Ames mutagenicity prediction. Chem Res Toxicol. 2026. Published online June 29, 2026. [24] Y., Frutos-Beltrán, E., Kang, D., Pannecouque, C., De Clercq, E., Menéndez-Arias, L., Liu, X., & Zhan, P. (2021). Medicinal chemistry strategies for discovering antivirals effective against drug-resistant viruses.. Chemical Society reviews. [25] Menéndez-Arias, L., & Gago, F. (2024). Antiviral Agents: Structural Basis of Action and Rational Design.. Sub-cellular biochemistry, 105, 745-784 .

Dosing Initiated in LOTUS, a Phase 2b Pediatric Trial of Zelicapavir; Topline Data Expected in 2027 On Track to Initiate RESOLVE, a Registrational Phase 2b/3 High-Risk Adult Trial of Zelicapavir in 4Q 2026; Topline Phase 2b Data Expected in 2027 On Track to Report Topline Data from a Phase 1 Trial of EDP-978, an Oral, Once-Daily KIT Inhibitor in Development for the Treatment of Urticaria, in 4Q 2026 On Track to File an IND for EPS-3903, an Oral, Once-Daily STAT6 Inhibitor and to Select an MRGPRX2 Development Candidate, in 2H 2026 Cash and Marketable Securities Totaling $211.5 Million at June 30, 2026, as well as Continuing Retained Royalties, with Cash Runway Expected to Fund Operations into Fiscal 2029 WATERTOWN, Mass.--(BUSINESS WIRE)-- Enanta Pharmaceuticals, Inc. (NASDAQ:ENTA), a clinical-stage biotechnology company dedicated to creating small molecule drugs for viral infections and immunological diseases, today reported financial results for its fiscal third quarter ended June 30, 2026. “During the quarter, we continued to build momentum across both our RSV and immunology programs,” said Jay R. Luly, Ph.D., President and Chief Executive Officer of Enanta. “Dosing began in LOTUS, our Phase 2b trial of zelicapavir in pediatric patients with RSV in Thailand, with topline data anticipated in 2027. We also announced plans to advance zelicapavir into a registrational Phase 2b/3 trial in high-risk adults with RSV and remain on track to initiate this study, RESOLVE, in the fourth quarter, with initial Phase 2b data expected next year. With no approved antiviral therapies currently available for RSV, we believe zelicapavir is uniquely positioned to address a substantial unmet need across both high-risk adult and pediatric populations. We continue to execute our clinical development plan and aim to deliver what could become the first approved antiviral treatment for RSV. Additionally, in immunology, we are focused on reporting topline data from our Phase 1 study of EDP-978 in the fourth quarter of 2026, while also advancing EPS-3903, our oral, once-daily STAT6 inhibitor, toward an IND filing this year. Further, we are on track to select an MRGPRX2 development candidate in the second half of 2026. With a catalyst rich year ahead, we have multiple opportunities to drive shareholder value and bring important treatments to patients in need.” Fiscal Third Quarter Ended June 30, 2026 Financial Results Total revenue for the three months ended June 30, 2026 was $14.4 million and consisted of royalty revenue from worldwide net sales of AbbVie’s hepatitis C virus (HCV) regimen MAVYRET®/MAVIRET® (glecaprevir/pibrentasvir), compared to $18.3 million for the three months ended June 30, 2025. The decrease in revenue is primarily due to AbbVie’s lower reported HCV sales as compared to the same period in 2025. ezstandalone.cmd.push(function () { ezstandalone.showAds(131); }); A portion (54.5%) of Enanta’s ongoing royalty revenue from AbbVie’s net sales of MAVYRET®/MAVIRET® is paid to OMERS, one of Canada’s largest defined benefit pension plans, pursuant to a royalty sale transaction affecting royalties earned after June 2023. For financial reporting purposes, the transaction was treated as debt, with the upfront purchase payment of $200.0 million recorded as a liability. Each quarter, Enanta records 100% of the royalty earned as revenue and then amortizes the debt liability proportionally as 54.5% of the cash royalty payments are paid to OMERS through June 30, 2032, subject to a cap of 1.42 times the purchase price, after which point 100% of the cash royalty payments will be retained by Enanta. Interest expense was $4.1 million for the three months ended June 30, 2026, as compared to $1.6 million for the period ended June 30, 2025. The increase was due to the increase in forecasted royalty revenue from AbbVie’s net sales of MAVYRET®/MAVIRET®. Research and development expenses totaled $22.1 million for the three months ended June 30, 2026, compared to $27.2 million for the three months ended June 30, 2025. The decrease was due to a decrease in clinical trial expenses for Enanta’s RSV programs, partially offset by increased costs associated with the Company’s immunology programs. General and administrative expenses totaled $9.5 million for the three months ended June 30, 2026, compared to $10.0 million for the three months ended June 30, 2025. The decrease was primarily due to a decrease in stock-based compensation expenses. Interest and investment income, net, totaled $1.9 million for the three months ended June 30, 2026, compared to $2.3 million for the three months ended June 30, 2025. The decrease in interest and investment income was due to lower interest rates year over year. Enanta recorded an income tax expense of less than $0.1 million for the three months ended June 30, 2026 compared to an income tax expense of less than $0.1 million for the three months ended June 30, 2025. Net loss for the three months ended June 30, 2026 was $19.5 million, or a loss of $0.67 per diluted common share, compared to a net loss of $18.3 million, or a loss of $0.85 per diluted common share, for the corresponding period in 2025. Enanta’s cash, cash equivalents and short-term and long-term marketable securities totaled $211.5 million at June 30, 2026. Enanta expects that its current cash, cash equivalents and marketable securities, as well as its retained portion of future royalty revenue, will be sufficient to meet the anticipated cash requirements of its existing business and development programs into fiscal 2029. Virology Enanta’s virology pipeline includes the leading portfolio of RSV treatments in clinical development, consisting of zelicapavir, a once-daily N-protein inhibitor, and EDP-323, a once-daily L-protein inhibitor, both of which received Fast Track designation from the U.S. Food and Drug Administration (FDA). Dosing began in LOTUS, a Phase 2b study of zelicapavir in pediatric patients with RSV. LOTUS will evaluate zelicapavir in approximately 150 hospitalized and non-hospitalized children aged 28 days to 36 months who test positive for RSV and have experienced symptoms for up to 72 hours. Conducted in collaboration with the Penta Foundation and the AMS-PHPT Research Unit at Chiang Mai University, LOTUS is designed to evaluate the efficacy, safety, and antiviral activity of zelicapavir, with topline data expected in 2027. In June, Enanta announced its advancement of zelicapavir into registrational development, following an End-of-Phase 2 meeting with the FDA. Advancement into registrational development through a single Phase 2b/3 trial further highlights zelicapavir’s potential to become the first approved antiviral therapy for RSV and supports Enanta's continued leadership in RSV drug development. RESOLVE, the registrational Phase 2b/3 trial of zelicapavir in high-risk adults with RSV is on track to initiate in the fourth quarter of 2026. RESOLVE will enroll adults with RSV who are at high risk of severe disease, including patients aged 75 years or older and those with COPD or congestive heart failure. The Phase 2b portion of RESOLVE is designed to confirm the treatment effect observed in the prior RSVHR study, which demonstrated a clinically meaningful benefit in this high-risk adult population. Topline Phase 2b data from RESOLVE is expected in 2027. Enanta presented data on zelicapavir at the American Thoracic Society (ATS) International Conference 2026 which was held May 15-20, 2026, in Orlando, Florida and at the European Society of Clinical Microbiology & Infectious Diseases (ESCMID) Global Conference 2026 which was held April 17-21, 2026, in Munich, Germany. The posters and presentations are available on the Company’s website here . Enanta’s second RSV candidate, EDP-323, can be used alone or in combination with other agents, such as zelicapavir, to potentially broaden the treatment window or addressable patient populations. Previously, the Company reported positive results from a Phase 2a challenge study of healthy adults infected with RSV, in which treatment with EDP-323 achieved highly statistically significant reductions in both viral load and clinical symptoms compared to placebo. Immunology Enanta’s immunology pipeline is focused on designing and developing highly potent and selective oral inhibitors for the treatment of inflammatory diseases, by targeting key drivers of the type 2 immune response. Enanta’s lead immunology program, EDP-978, is a potent and selective once-daily oral KIT inhibitor in development for the treatment of chronic urticaria and potentially other mast cell-mediated diseases. In April, the Company announced that the first participant was dosed in a randomized, double-blind, placebo-controlled, first-in-human Phase 1 clinical trial. The trial is expected to enroll approximately 98 healthy adult volunteers ranging in age from 18 to 65 years old to evaluate the safety, tolerability, pharmacokinetics, and pharmacodynamics, including serum tryptase, of EDP-978. The trial includes a single ascending dose phase, with a two-part food-effect cohort, and a multiple ascending dose phase with a 14-day treatment period. The Company expects to report topline data from the trial in the fourth quarter of 2026. Enanta’s second immunology program, EPS-3903, is a novel, potent and selective oral STAT6 inhibitor, in development for the treatment of atopic dermatitis and other diseases currently treated by dupilumab. The Company is currently performing scale-up and IND-enabling activities and is targeting an IND filing in the second half of 2026. Enanta presented posters highlighting data on EPS-3903 at the ATS International Conference 2026 which was held May 15-20, 2026, in Orlando, Florida and at the American Association of Immunology Conference (Immunology 2026™) which was held April 15-19, 2026, in Boston, Massachusetts. The posters are available on the Company’s website here . Enanta’s third immunology program targets MRGPRX2, a non-canonical G-Protein-Coupled-Receptor (GPCR) expressed predominantly on mast cells, as well as peripheral neurons. Inhibiting MRGPRX2 may have potential to address multiple mast-cell driven diseases, as well as having potential in migraine. Currently, the Company is evaluating multiple compounds in preclinical studies and expects to select a development candidate in the second half of 2026. Corporate In June, Enanta announced that its partner AbbVie received European Commission approval of MAVIRET® (glecaprevir/pibrentasvir) for the treatment of acute hepatitis C virus (HCV) infection in adults and children aged three years and older. MAVIRET is now the only treatment approved in the European Union for both acute and chronic HCV infection. Glecaprevir, one of the two direct-acting antivirals in MAVIRET, was discovered by Enanta and is a source of ongoing royalty revenue for the Company. In June, the United States Court of Appeals for the Federal Circuit affirmed the summary judgment decision of the United States District Court for the District of Massachusetts in the Company’s suit against Pfizer Inc. and ruled that the claims of U.S. Patent No. 11,358,953 were invalid. In July, the Company filed a combined petition for panel or en banc rehearing of the Federal Circuit’s decision. A hearing for the patent infringement action against Pfizer in the Unified Patent Court (UPC) of the European Union, and Pfizer’s counterclaim for revocation, has been scheduled for September 29, 2026. Enanta expects a decision from the UPC within weeks after the hearing. Enanta plans to issue its fiscal fourth quarter financial results press release on November 16, 2026. About Enanta Pharmaceuticals, Inc. Enanta is using its robust, chemistry-driven approach and drug discovery capabilities to become a leader in the discovery and development of small molecule drugs for viral infections and immunological diseases. In virology, Enanta’s clinical programs are focused on the development of first-in-disease and best-in-disease treatments for respiratory syncytial virus (RSV). The Company’s immunology pipeline aims to develop treatments for inflammatory diseases by targeting key drivers of the type 2 immune response, with KIT, STAT6 and MRGPRX2 inhibition. Glecaprevir, a protease inhibitor discovered by Enanta, is part of the only treatment approved for curing both acute and chronic hepatitis C virus (HCV) infection and is sold by AbbVie in numerous countries under the tradenames MAVYRET® (U.S.) and MAVIRET® (ex-U.S.) (glecaprevir/pibrentasvir). A portion of Enanta’s royalties from HCV products developed under its collaboration with AbbVie contribute ongoing funding to Enanta’s operations. Please visit for more information. Forward-Looking Statements This press release contains forward-looking statements, including statements with respect to the timeline and prospects for advancement of Enanta’s clinical programs in RSV and KIT inhibition and its preclinical immunology programs, including its programs targeting STAT6 and MRGPRX2 inhibition. Statements that are not historical facts are based on management’s current expectations, estimates, forecasts and projections about Enanta’s business and the industry in which it operates and management’s beliefs and assumptions. The statements contained in this release are not guarantees of future performance and involve certain risks, uncertainties and assumptions, which are difficult to predict. Therefore, actual outcomes and results may differ materially from what is expressed in such forward-looking statements. Important factors and risks that may affect actual results include: the impact of development, regulatory and marketing efforts of others with respect to vaccines and competitive treatments for RSV; the discovery and development risks of Enanta’s programs in virology and immunology; Enanta’s limited clinical development experience; Enanta’s ability to partner its RSV or other programs; Enanta’s need to attract and retain senior management and key research and development personnel; Enanta’s need to obtain and maintain patent protection for its product candidates and avoid potential infringement of the intellectual property rights of others; the outcome of the Federal Circuit rehearing petition and the Unified Patent Court proceedings related to Enanta’s patent claim against Pfizer; and other risk factors described or referred to in “Risk Factors” in Enanta’s Form 10-K for the fiscal year-ended September 30, 2025, and any other periodic reports filed more recently with the Securities and Exchange Commission. Enanta cautions investors not to place undue reliance on the forward-looking statements contained in this release. These statements speak only as of the date of this release, and Enanta undertakes no obligation to update or revise these statements, except as may be required by law. Tables to Follow ENANTA PHARMACEUTICALS, INC. CONDENSED CONSOLIDATED STATEMENTS OF OPERATIONS UNAUDITED (in thousands, except per share amounts) Three Months Ended Nine Months Ended June 30, June 30, 2026 2025 2026 2025 Revenue $ 14,359 $ 18,314 $ 50,133 $ 50,199 Operating expenses Research and development 22,126 27,210 62,428 82,931 General and administrative 9,469 9,997 28,046 34,231 Total operating expenses 31,595 37,207 90,474 117,162 Loss from operations (17,236 ) (18,893 ) (40,341 ) (66,963 ) Interest expense (4,130 ) (1,618 ) (10,529 ) (5,294 ) Interest and investment income, net 1,901 2,285 6,407 7,376 Loss before income taxes (19,465 ) (18,226 ) (44,463 ) (64,881 ) Income tax (expense) benefit (36 ) (29 ) (67 ) 1,692 Net loss $ (19,501 ) $ (18,255 ) $ (44,530 ) $ (63,189 ) Net loss per share Basic $ (0.67 ) $ (0.85 ) $ (1.54 ) $ (2.96 ) Diluted $ (0.67 ) $ (0.85 ) $ (1.54 ) $ (2.96 ) Weighted average common shares outstanding Basic 29,090 21,377 28,958 21,322 Diluted 29,090 21,377 28,958 21,322 ENANTA PHARMACEUTICALS, INC. CONDENSED CONSOLIDATED BALANCE SHEETS UNAUDITED (in thousands) June 30, September 30, 2026 2025 Assets Current assets Cash and cash equivalents $ 33,419 $ 32,298 Short-term marketable securities 156,087 156,566 Accounts receivable 6,534 6,882 Prepaid expenses and other current assets 7,579 8,590 Total current assets 203,619 204,336 Long-term marketable securities 21,987 — Property and equipment, net 31,942 35,395 Operating lease, right-of-use assets 35,852 37,549 Long-term restricted cash 3,360 3,360 Other long-term assets 110 92 Total assets $ 296,870 $ 280,732 Liabilities and Stockholders' Equity Current liabilities Accounts payable $ 3,293 $ 1,948 Accrued expenses and other current liabilities 10,183 12,751 Liability related to the sale of future royalties 36,784 30,710 Operating lease liabilities 3,906 3,146 Total current liabilities 54,166 48,555 Liability related to the sale of future royalties, net of current portion 88,289 111,132 Operating lease liabilities, net of current portion 51,750 54,757 Series 1 nonconvertible preferred stock 1,311 1,311 Other long-term liabilities 286 260 Total liabilities 195,802 216,015 Total stockholders' equity 101,068 64,717 Total liabilities and stockholders' equity $ 296,870 $ 280,732 Contacts Media and Investors Contact: Jennifer Viera jviera@enanta.com