Outstanding questions overshadow GSK’s respiratory syncytial virus win

The soon-to-be pure-play pharma company GSK desperately needed a hit in respiratory syncytial virus – the vaccine for older adults is considered its most valuable pipeline project. Relief all round then at news of success for the phase 3 Aresvi 006 trial, though lack of detail makes the extent of the win unknowable. GSK described the result as “statistically significant and clinically meaningful”, adding that the effect size was consistent across secondary endpoints and in those aged 70 and above. The company has previously described efficacy above 50% as clinically meaningful, 70% very good and above 80% outstanding; analysts want to see at least 70%, believing that anything less would leave GSK susceptible to projects coming behind. Durability of response is another consideration, with some analysts concerned that regulators might want to see data over more than one RSV season. GSK is confident that its vaccine, which uses the same adjuvant as Shingrix, will provide long-term protection; this is an issue that all contenders must address, of course, and could be an important differentiator in the long term. With Pfizer and J&J also expecting pivotal readouts later this year, the race to market will soon be on.