hVIVO plc

("hVIVO", the "Company" or the "Group")

Positive results from RSV antiviral human challenge trial conducted by hVIVO

Larger human challenge trial provides valuable insights for candidate development

hVIVO plc (AIM: HVO), a fast-growing specialist contract research organisation (CRO) and world leader in testing infectious and respiratory disease products using human challenge clinical trials, notes the announcement by Enanta Pharmaceuticals ("Enanta"), reporting positive topline results from a Phase 2a Respiratory Syncytial Virus ("RSV") human challenge trial ("HCT") in healthy adults conducted by hVIVO for EDP-323, its second RSV antiviral candidate.

EDP-323, a novel, oral, direct-acting antiviral in development for RSV infection, has made impressive strides, achieving U.S. Food and Drug Administration (FDA) Fast Track designation. The topline results from the HCT involving 142 healthy adult volunteers demonstrate the effectiveness of EDP-323. With participants split into three cohorts (47 receiving a high dose, 47 receiving a low dose and 47 receiving a placebo), the study showed that EDP-323 was generally safe, well-tolerated, and demonstrated a rapid and sustained antiviral effect. The results show an 85-87% reduction in viral load area under the curve (AUC) by qRT-PCR (p<0.0001), a 97-98% reduction in infectious viral load AUC by viral culture (p<0.0001), and a 66-78% reduction of total clinical symptoms score AUC (p<0.0001) compared to placebo.

These positive results highlight the significant role human challenge trials play in accelerating efficacy data collection and reducing the risks associated with later stage clinical development. With three decades of experience and expertise in safely conducting human challenge studies, hVIVO is proud to support groundbreaking research like this across a range of respiratory viruses, including RSV, influenza, human rhinovirus (HRV - common cold virus), and COVID-19. The Company looks forward to seeing continued success for Enanta and EDP-323 in the future.

Enanta's full announcement is available here. EDP-323 is Enanta's second RSV candidate. Zelicapavir (EDP-938), Enanta's first candidate, has already shown impressive results in an earlier RSV HCT and is in later stage clinical development.

Dr Andrew Catchpole, Chief Scientific Officer of hVIVO, said: "Enanta's trial demonstrates the depth of actionable insights a comprehensive human challenge trial can provide. We congratulate Enanta on these impressive results, which mark a significant step forward in the development of new medicines to treat respiratory infections such as RSV. Achieving such positive outcomes underscores the potential of this novel RSV treatment to make a meaningful impact on patient care. We are proud to provide world leading human challenge trials to support the development of exciting drug candidates which hold the potential to have a positive impact on global health."

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Notes to Editors

About hVIVO

hVIVO plc (ticker: HVO) is a fast-growing specialist contract research organisation (CRO) and the world leader in testing infectious and respiratory disease vaccines and therapeutics using human challenge clinical trials. The Group provides end-to-end early clinical development services to its large, established and growing repeat client base, which includes four of the top 10 largest global biopharma companies.

The Group's fast-growing services business includes a unique portfolio of 11 human challenge models, with a number of new models under development, to test a broad range of infectious and respiratory disease products. The Group has world class challenge agent manufacturing capabilities, specialist drug development and clinical consultancy services via its Venn Life Sciences brand, and a lab offering via its hLAB brand, which includes virology, immunology biomarker and molecular testing. The Group also offers additional clinical field trial services such as patient recruitment and clinical trial site services.

hVIVO runs challenge trials in London - its new state-of-the-art facilities in Canary Wharf opened in 2024 and is the world's largest commercial human challenge trial unit, with highly specialised on-site virology and immunology laboratories, and an outpatient unit. To recruit volunteers / patients for its studies, the Group leverages its unique clinical trial recruitment capability via its FluCamp volunteer screening facilities in London and Manchester.