hVIVO Regulatory News (HVO)

REACH

27 November 2025

hVIVO plc

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

MSD to acquire Cidara following Positive Results from Phase IIb Trial

hVIVO plc (AIM: HVO), a full-service early phase Contract Research Organisation (CRO) and the world leader in human challenge clinical trials, congratulates its client Cidara Therapeutics, Inc ("Cidara" or the "partner") which has entered into a definitive agreement under which Merck Sharp & Dohme LLC ("MSD"), through a subsidiary, will acquire Cidara for a total transaction value of approximately $9.2 billion. This transaction underscores the value of hVIVO's unique capabilities in accelerating drug development and validates the Company's strategic role in supporting breakthrough therapies.

Cidara's lead candidate, CD388 is an investigational, long-acting, strain-agnostic antiviral agent designed to prevent influenza infection in individuals at higher risk of complications and offers protection against both influenza A and B. CD388 is currently in Phase III clinical development and has received Breakthrough Therapy Designation and Fast Track Designation from the U.S. FDA.

hVIVO has partnered with Cidara throughout the development of CD388, delivering critical data that enabled its progression from early proof-of-concept to late-stage trials. Completed in 2023, hVIVO conducted a randomized, double-blind influenza human challenge study in healthy volunteers, providing early proof-of-concept data for CD388 ahead of later stage trials. 59 study participants were enrolled into the study and the primary efficacy analysis comparing the total viral load (area under the curve / AUC) showed a reduction in the CD388 treated arm compared to placebo. Similarly, the peak viral loads measured by both qPCR and cell culture were lowered in CD388 treated participants compared to placebo.

Building on this success hVIVO continued to support the development of CD388, participating as the only UK site in Cidara's Phase IIb field study conducted over the 2024 / 2025 flu season assessing the protective efficacy of CD388 in healthy adults. During the study, hVIVO delivered its largest-ever number of participants enrolled into a field trial, screening more than 1,100 participants and dosing 817 within six weeks, achieving the highest recruiting numbers of all sites across the globe. This achievement demonstrated hVIVO's ability to execute large-scale field studies with speed and precision. The Phase IIb data read-out showed that all the primary and secondary endpoints were met. The Company continues to support Cidara through Phase III development, acting as a major clinical site for the ongoing multi-site trial.

In addition, hVIVO has acted as the central Virology Laboratory for both of Cidara's CD388 Phase IIb and Phase III programs. As part of this service provision hVIVO has provided scientific consultancy, assembled sample collection kits, managed global virology sample logistics, and is responsible for multiple virology and immunology assays including the primary endpoint analysis.

Dr Yamin 'Mo' Khan, Chief Executive Officer of hVIVO, said: "We congratulate Cidara on this landmark transaction in the infectious disease space with MSD. For hVIVO, this demonstrates that our human challenge trial expertise can indeed lead to significant downstream value creation. It also validates hVIVO's diversification into field studies and standalone laboratory services, facilitated by our highly efficient patient recruitment and site services along with our extensive infectious disease knowledge and capabilities. We are proud to have supported CD388 from early proof-of-concept through Phase IIb and into Phase III, and we look forward to patients benefitting from this innovative therapy."

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Notes to Editors

hVIVO plc (Ticker: HVO) is full-service early phase Contract Research Organisation (CRO) and the global leader in human challenge trials. The company delivers end-to-end clinical development services to a diverse and expanding client base, including seven of the world's ten largest biopharma companies.

hVIVO specialises in conducting human challenge trials across multiple infectious and respiratory indications, leveraging its state-of-the-art quarantine facility in London-the largest of its kind worldwide. The Company also offers comprehensive virology and immunology laboratory services under the hLAB brand.

Through its German subsidiary, CRS, hVIVO operates a 120-bed capacity across Mannheim and Kiel, providing early-phase clinical trial services, including first-in-human and proof-of-concept studies. Its second subsidiary, Venn Life Sciences, offers Early Drug Development Consulting and Biometry services to the biopharma sector.

The Group provides fully integrated drug development solutions from preclinical stages through Phase II trials, alongside patient recruitment via FluCamp. Additionally, its five clinical sites support outpatient Phase II and III trials, ensuring a seamless and efficient pathway from discovery to late-stage development.