GSK culls phase 2 RSV vaccine in kids, as feladilimab flops again in lung cancer

GlaxoSmithKline is shutting down development of a vaccine to prevent respiratory syncytial virus in infants after early stage studies showed it did not protect against the common condition that can become severe in some children. 

The RSV vaccine, GSK3389245A, also known as ChAd155-RSV, is a recombinant chimpanzee adenovirus vector vaccine that GSK developed with the Oxford Vaccine Group—also known for working on AstraZeneca’s COVID-19 jab. The vaccine is based on three RSV viral proteins encoded by the vector and was expected to engage both the humoral and cellular arms of the immune system against the pathogen.

GSK began a phase 1/2 trial in RSV-positive infants aged 12 to 23 months in 2016. Another phase 1/2 study in infants aged six and seven months who were unlikely to have previously been exposed to RSV got underway in 2019 and reached the point of primary completion in January.

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That is as far as GSK3389245A is going to get as an RSV prophylactic in the pediatric population. GSK revealed the discontinued development “following assessment that target efficacy profile was unlikely to be met” as part of the release of second-quarter results on Wednesday.

The U.K. pharma giant said in an emailed statement that development in the three to seven months population has been shut down "after preliminary data suggested that the vaccine candidate does not induce high levels of vaccine efficacy in the prevention of RSV disease."

"GSK remains committed to addressing the burden of RSV disease through our maternal and older adult vaccine candidates, which use different technologies ... and are both progressing in phase 3 trials," a spokesperson said. "We remain confident in the potential of our viral vector technology, and our therapeutic hepatitis B virus development program continues as planned."

News of the discontinuation comes months after GSK began a late-stage study of another vaccine for RSV, GSK3888550A. By giving the vaccine to pregnant women, GSK is aiming to protect babies from the virus during their first months of life. 

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GSK disclosed the discontinuation of the pediatric RSV program alongside another update on its ICOS agonist feladilimab. A combination of the investigational asset and the chemotherapy docetaxel failed to hit the primary endpoint in a phase 2 lung cancer study at the interim analysis.

Analysts at Jefferies said the failure was “not unexpected.” The flop follows the April decision to stop enrolling head and neck squamous cell carcinoma patients in a phase 2 feladilimab study.