GSK Initiates Phase 3 Study of RSV Maternal Vaccine Candidate

GSK recently announced that it will begin a Phase 3 study investigating the safety and efficacy of its Respiratory Syncytial Virus (RSV) vaccine candidate for maternal immunization. 

The double-blind Phase 3 study will enroll 10,000 pregnant women aged 18 to 49 years to uncover if a single dose of GSK’s RSV Maternal unadjuvanted vaccine candidate, GSK3888550A, can prevent RSV-associated lower respiratory tract infections (LRTI) in newborn infants. 

Researchers will study the candidate in vaccinated mothers as well, with interim results anticipated by the second half of 2022.

“RSV burden is high amongst young infants – a vaccine which protects them from birth would represent significant progress in addressing the burden of RSV, preventing infant illness and families’ distress, as well as reducing the associated burden for society,” Emmanuel Hanon, senior vice president and head of vaccines research and development at GSK, said in the announcement. 

“Advancing our portfolio of RSV vaccine candidates based on robust available data is a major step towards GSK’s goal of reducing the RSV-associated disease burden around the world,” he continued.

The initiation of the Phase 3 study comes on the heels of positive safety, reactogenicity, and immunogenicity results from a Phase 2/3 study of the vaccine candidate. The results were released last month. 

Specifically, GSK found that its vaccine candidate was generally well tolerated in older adults, eliciting a robust humoral and cellular immunity compared with baseline. 

Researchers also found a nearly ten-fold increase in protective antibodies in the group vaccinated with GSK3888550A.

In an additional study released in October, data showed that GSK3888550A was well-tolerated and able to boost the pre-existing immunity in 502 non-pregnant women, leading to a high level of protecting neutralizing antibodies. 

Notably, there was a 14-fold increase in RSV-A and RSV-B observed just one week after immunization, researchers said. 

RSV is the leading cause of respiratory infections, including bronchiolitis and viral pneumonia in infants.

About 33 million cases of RSV occur in children under five years old globally, with 1.4 million hospitalizations of infants under six months of age, GSK said. 

GSK3888550A is part of a portfolio of RSV vaccine candidates that GSK is currently developing, which are all based on different technologies and tailored to the needs of target populations.

The Phase 3 study for the older adult’s RSV vaccine candidate is anticipated to start in the coming months, while the phase 1/2 study with the pediatric RSV candidate vaccine is ongoing, GSK said. 

Because there is no preventative vaccine or antiviral treatments currently available for RSV, top pharmaceutical companies are continuing to join the fight to develop a treatment and ensure care for millions of people. 

Back in August 2018, Denmark-based biotechnology company, Bavarian Nordic, announced that its RSV vaccine candidate was durable and remained elevated compared to baseline in at least 60 percent of the participants enrolled in a Phase 2 clinical trial. 

T-cell responses were also elevated at one-year post-vaccination in half of the participants.

Currently, the vaccine is still showing promise, but the company recently stated that the COVID-19 pandemic may slow production. 

Last September, Janssen Pharmaceuticals also announced that FDA granted Breakthrough Therapy Designation for the company’s investigational prophylactic RSV vaccine to be used in adults aged 60 years or older.

FDA granted the Breakthrough Therapy Designation based on clinical data that showed that Janssen’s vaccine may demonstrate substantial improvement compared to standard of care. 

But other companies, such as Novavax, did not have success in developing an RSV vaccine.

In February 2019, the company announced results from the Prepare Phase 3 clinical trial of ResVax, an aluminum adjuvanted RSV fusion protein recombinant nanoparticle vaccine.

Specifically, the treatment was only 39 percent effective against medically significant RSV LRTI, 44 percent effective against RSV LRTI infection hospitalizations, and 48 percent effective against RSV LRTI with severe hypoxemia.