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#ORPH Open Orphan – Omicron human challenge model

  Vaxart becomes the first client of the programme to test its oral COVID-19 vaccine candidate

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, announces that  hVIVO , a subsidiary of Open Orphan, is developing the world’s first Omicron human challenge model. hVIVO has signed an agreement with Vaxart Inc. (“Vaxart”), (NASDAQ: VXRT) to develop the model with the intent to conduct a subsequent Omicron human challenge study in 2023 to test the efficacy of Vaxart’s oral vaccine candidate, VXA-CoV2-1.


To develop the model, hVIVO will manufacture a new SARS-CoV-2 (COVID-19) challenge agent based on the Omicron variant. The Good Manufacturing Practice (“GMP”) compliant virus manufacturing activities will commence immediately and are expected to complete by Q4 2022. Following manufacture of the challenge agent, the Company intends to conduct a characterisation study. Subject to the successful completion of the characterisation study and receipt of relevant regulatory approvals, hVIVO expects to conduct Omicron human challenge studies in 2023.

The characterisation study will establish a dose of the Omicron challenge agent that will cause a safe and reliable infection in healthy volunteers. The study will enrol healthy male and female volunteers who have previously been vaccinated against or infected with SARS-CoV-2, with no known risk factors for severe COVID-19 and low levels of serum neutralising antibodies (and therefore still likely to become infected following inoculation).

hVIVO has two decades of experience and expertise in challenge agent manufacture and clinical characterisation across a range of respiratory viruses including various strains of influenza, respiratory syncytial virus (RSV), human rhinovirus (hRV – common cold virus), as well as the initial circulating SARS-CoV-2 virus and variants which have since emerged. hVIVO leads the Challenge Agent Manufacture Consortium, which has developed international standards that pertain to challenge agent manufacture and storage, to ensure safety, quality and consistency.

Yamin Khan, Chief Executive Officer of Open Orphan, said: “With our leading end-to-end human challenge expertise, we are delighted to be developing the world’s first Omicron human challenge model and to welcome Vaxart as the first client of this programme.

“hVIVO’s fight against the pandemic continues with the development of this new challenge agent. The benefits to Vaxart are immense, and we have already been contacted by a number of biopharma companies looking to test the efficacy of their products using this challenge virus. I have no doubt that the successful completion of the world’s first COVID-19 characterisation, which was published in Nature Medicine earlier this year, has given our customers the confidence to move forward with the less severe yet more infective Omicron challenge model.”

Dr. James Cummings, Chief Medical Officer of Vaxart, said: “A human challenge study of our oral tablet COVID-19 vaccine candidate against the Omicron variant of SARS-CoV-2 is the most rapid and direct way to assess the efficacy of this candidate against a highly prevalent viral strain.

“hVIVO has pioneered COVID-19 characterization and the Omicron human challenge model, and the use of this model in our planned Phase II human challenge trial will rapidly generate robust, controlled data on the ability of our COVID-19 vaccine candidate to prevent infection and the development of symptomatic disease, as well as its effect on viral shedding, which plays a critical role in the spread of infection from one person to another. The results of this study will inform the next steps in the development of our COVID-19 vaccine candidate, which has the potential to transform personal and public health approaches to controlling the global pandemic.”

Dr Andrew Catchpole, Chief Scientific Officer of hVIVO, said: “The team and I at hVIVO are excited to begin work to manufacture an Omicron challenge agent, the follow-on characterisation, and future human challenge trials. We have unparalleled expertise in SARS-CoV-2 challenge agent manufacturing, having completed work on both the original Wuhan strain and the subsequent Delta variant, in addition to our prior experience in successfully conducting the world’s first COVID-19 characterisation study, and our decades of experience in conducting human challenge trials. We are delighted to be working with Vaxart on this programme and look forward to the opportunity to subsequently test the efficacy of their exciting novel vaccine.”

Interested in becoming a volunteer?


hVIVO recruits many of its volunteers for its challenge study clinical trials through its dedicated  volunteer recruitment website,  www.flucamp.com . 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.


For further information please contact:


Open Orphan plc

+44 (0) 20 7756 1300

Yamin Khan, Chief Executive Officer

Liberum Capital (Nominated Adviser and Joint Broker)

 +44 (0) 20 3100 2000

Ben Cryer/ Edward Mansfield/ Phil Walker/ Will King

finnCap plc (Joint Broker)

+44 (0) 20 7220 0500

Geoff Nash / James Thompson / Richard Chambers

Davy (Euronext Growth Adviser and Joint Broker)

+353 (0) 1 679 6363

Anthony Farrell

Walbrook PR (Financial PR & IR)

Paul McManus / Sam Allen / Louis Ashe-Jepson

+44 (0)20 7933 8780 or  openorphan@walbrookpr.com

+44 (0)7980 541 893 / +44 (0) 7502 558 258 /

+44 (0)7747 515393

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