Open Orphan PLC (AIM: ORPH) Positive results from RSV Human Challenge Study

Data on Phase 2a study published in New England Journal of Medicine

Open Orphan plc (AIM: ORPH), a rapidly growing specialist contract research organisation (CRO) and world leader in testing infectious and respiratory disease products using human challenge clinical trials, notes the announcement dated February 17 2022 from Enanta Pharmaceuticals, Inc.

(NASDAQ: ENTA), a clinical-stage biotechnology company dedicated to creating small molecule drugs for viral infections and liver diseases, on positive results from a human challenge study assessing its respiratory syncytial virus (“RSV”) antiviral candidate, EDP-938.

The results from this human challenge study have been published in TheNew England Journal of Medicine. hVIVO, a subsidiary of Open Orphan, conducted the Phase 2a, double-blind, placebo-controlled trial using its RSV Human Challenge Study Model.

The trial enrolled 178 healthy adult volunteers across two parts, 18-55 years of age, who were intranasally challenged with RSV-A Memphis 37b (“M37b”). Volunteers received either a dose of EDP-938 or placebo for five days after infection, with different dose levels of EDP-938 being assessed.

The study demonstrated that both viral load and clinical symptoms were significantly lower in volunteers that received EDP-938 than those that received placebo, with similar safety profiles between placebo and the antiviral regimens. Importantly, no serious adverse events occurred.

RSV is a contagious, common respiratory virus that usually causes mild, cold-like symptoms and affects the respiratory tract of children and at-risk older adults; in severe cases, it can cause pneumonia and other life-threatening breathing difficulties. RSV is a significant public health threat and is one of the leading causes of hospitalisation to at-risk older adults.

hVIVO has two decades of experience and expertise in safely conducting challenge studies across a range of respiratory and infectious disease viruses, including various strains of influenza, RSV, HRV, asthma and malaria, etc.

Dr Andrew Catchpole, Chief Scientific Officer of hVIVO said: ” It’s pleasing to see another of our clients getting such positive results from a human challenge study that we conducted, and that the data has been published in The New England Journal of Medicine. EDP-938 is a potentially important medicine that could help reduce the global impact of RSV, and I look forward to following Enanta’s continued progression of the candidate through further clinical trials.”

Cathal Friel, Executive Chairman of Open Orphan, said: “We are delighted to see that this important Phase 2a study of EDP-938 has yielded such positive results. We are a world leader in testing infectious and respiratory disease products using challenge studies such as this, and RSV is just one portion of our portfolio of challenge models, which also includes influenza, HRV, malaria, asthma, and now SARS-CoV-2. We look forward to continue offering our world class services to partners as we look to meet the growing demand from the infectious disease market.”

Interested in becoming a volunteer?

hVIVO recruits many of its volunteers for its challenge study clinical trials through its dedicated volunteer recruitment website, By volunteering to take part in one of our studies in a safe, controlled, clinical environment under expertly supervised conditions you are playing your part to further medical research and help increase the understanding of respiratory illnesses.

Individuals interested in taking part in COVID-19 human challenge study research can learn more at

For further information please contact:

Open Orphan plc

+353 (0) 1 644 0007

Cathal Friel, Executive Chairman

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