Enanta Pharmaceuticals to Present Topline Results from First-in-Pediatrics Phase 2 Study Evaluating Zelicapavir for Respiratory Syncytial Virus (RSV)

• Conference call and webcast to discuss data on Monday, December 9 at 8:30 a.m. ET

Enanta Pharmaceuticals, Inc. (NASDAQ:ENTA), a clinical-stage biotechnology company dedicated to creating small molecule drugs for virology and immunology indications, today announced the company will hold a conference call and webcast on Monday, December 9 at 8:30 a.m. ET to share topline results from RSVPEDs, a first-in-pediatrics Phase 2 study evaluating zelicapavir in hospitalized and non-hospitalized children aged 28 days to 36 months with respiratory syncytial virus (RSV).

Conference Call and Webcast Information The live webcast on Monday, December 9 at 8:30 a.m. ET can be accessed at "Events & Presentations" in the investors section of Enanta’s website. To participate by phone, please register for the call here. It is recommended that participants register a minimum of 15 minutes before the call. Once registered, participants will receive an email with the dial-in information. The archived webcast will be available on Enanta’s website for approximately 30 days following the event.

About Zelicapavir Zelicapavir, Enanta’s lead N-protein inhibitor, is being developed for the treatment of RSV infection, and has been granted Fast Track designation by the U.S. Food and Drug Administration. Zelicapavir is a nanomolar inhibitor of both RSV-A and RSV-B activity. Zelicapavir is differentiated from RSV fusion inhibitors as the N-protein inhibitor targets the virus’ replication machinery and has demonstrated a high barrier to resistance in vitro. In preclinical studies, zelicapavir maintained antiviral potency across all clinical isolates tested and was active against viral variants resistant to other mechanisms. Zelicapavir demonstrated a favorable safety, pharmacokinetic and drug-drug interaction profile in an extensive Phase 1 program. In a Phase 2 challenge study, zelicapavir achieved highly statistically significant (p<0.001) reductions in RSV viral load and clinical symptoms compared to placebo and was safe and well-tolerated, with infrequent adverse events. Zelicapavir is currently being evaluated in RSVHR, a Phase 2b study in the elderly and/or those with congestive heart failure, chronic obstructive pulmonary disease (COPD) or asthma.

About Respiratory Syncytial Virus RSV is the most common cause of bronchiolitis (inflammation of the small airways in the lung) and pneumonia in children under one year of age in the United States and a significant cause of respiratory illness in older adults and immunocompromised individuals.1 According to the Centers for Disease Control and Prevention, virtually all children in the United States get an RSV infection by the time they are two years old and one to two out of every 100 children younger than six months of age with an RSV infection may need to be hospitalized.2 Globally, there are an estimated 33 million cases of RSV annually in children less than five years of age, with about 3 million hospitalized and up to approximately 100,000 dying each year from complications associated with the infection.3 RSV represents a significant health threat for adults older than 65 years of age, with an estimated 177,000 hospitalizations and 14,000 deaths associated with RSV infections annually in the United States.4

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 with an emphasis on indications in virology and immunology. Enanta’s clinical programs are currently focused on respiratory syncytial virus (RSV) and its earlier-stage immunology pipeline aims to develop treatments for inflammatory diseases by targeting key drivers of the type 2 immune response, including KIT and STAT6 inhibition.

Glecaprevir, a protease inhibitor discovered by Enanta, is part of one of the leading treatment regimens for curing 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 www.enanta.com for more information.

Forward Looking Statements Disclaimer This press release contains forward-looking statements, including with respect to the prospects for further development and advancement of zelicapavir for the treatment of RSV. 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 development risks of early stage discovery efforts in the disease areas in Enanta’s research and development pipeline, such as RSV; the impact of development, regulatory and marketing efforts of others with respect to competitive treatments for RSV; Enanta’s limited clinical development experience; Enanta’s need to attract and retain senior management and key scientific 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; and other risk factors described or referred to in “Risk Factors” in Enanta’s most recent Annual Report on Form 10-K for the fiscal year ended September 30, 2024 and 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. All forward-looking statements contained in this release speak only as of the date on which they were made and are based on management’s assumptions and estimates as of such date. Enanta undertakes no obligation to update such statements to reflect events that occur or circumstances that exist after the date on which they were made, except as required by law.

1. Centers for Disease Control & Prevention – Respiratory Syncytial Virus Last accessed: December 2024.
2. Centers for Disease Control & Prevention – RSV in Infants and Young Children Last accessed: December 2024.
3. Shi, Ting et al. “Global, regional, and national disease burden estimates of acute lower respiratory infections due to respiratory syncytial virus in young children in 2015: a systematic review and modelling study.” Lancet (London, England) vol. 390,10098 (2017): 946-958. doi:10.1016/S0140-6736(17)30938-8
4. Falsey, Ann R et al. “Respiratory syncytial virus infection in elderly and high-risk adults.” The New England Journal of Medicine vol. 352,17 (2005): 1749-59. doi:10.1056/NEJMoa043951

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