In September 2023 Vir Biotechnology announced that the first participant in a Phase I trial has been dosed. The trial of VIR-1388 will evaluate the safety, reactogenicity, and immunogenicity of the investigational novel T cell vaccine for the prevention of human immunodeficiency virus (HIV). Initial data from the trial are expected in the latter half of 2024.  


VIR-1388 is an investigational subcutaneously administered HIV T cell vaccine based on the human cytomegalovirus (HCMV) vector platform. It is designed to elicit “abundant” T cells that recognise several HIV proteins in a different way to that of previous vaccine efforts. VIR-1388 applies lessons from VIR-1111, an investigational proof-of-concept vaccine, with the goal of creating a safe and effective HIV vaccine.  

The vector is a weakened version of the virus, designed to deliver the vaccine material to the immune system “without causing disease” in participants. HCMV has been present in “much of the global population for centuries”, with most people experiencing no symptoms and being unaware of infection. It remains detectable in the body for life. Thus, the team at Vir believe it could deliver and help the body retain vaccine material for a long period.  

The trial 

The Phase I trial is randomised, double-blind, and placebo-controlled evaluation of the safety, reactogenicity, and immunogenicity of three different doses of VIR-1388 compared with placebo. It is expected to enrol around 95 participants between the ages of 18 and 55 who are not living with HIV, with existing antibodies specific to HCMV, and in overall good health.  

The study comprises two parts; Part A is a lead-in phase enrolling a limited number of HCMV-positive patients of non-childbearing potential with a frequent safety monitoring schedule. The second part, Part B, expands enrolment to a broader population of HCMV-positive patients, including persons of childbearing potential. An optional long-term follow-up study will increase participation for up to three years after the first dose.  

The trial is supported by NIAID and the Bill & Melinda Gates Foundation. It takes place across international sites within the federally funded HIV Vaccine Trials Network (HVTN).  

A major challenge and a clinical milestone 

UNAIDS estimates that in 2021 around 1.5 million people were newly infected with HIV, with around 650,000 dying from AIDS-related deaths. Dr Carey Hwang, Vir’s Senior Vice President, Clinical Research, Head of Chronic Infection, describes HIV as a continued “major global public health challenge” that persists despite “decades of research efforts”.  

“The initiation of our first clinical trial evaluating VIR-1388 is an important clinical milestone in our pursuit of developing an HIV vaccine.”  

Dr Hwang hopes that the “unique approach” will “help close the longstanding public health gap in HIV prevention”.  

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