Ark Biopharmaceutical’s bet on one of the less congested parts of the respiratory syncytial virus (RSV) space has delivered phase 3 results. Having picked up an antiviral prospect from Roche, ArkBio has now reported a late-phase study in infants hospitalized with RSV has met its primary endpoint.
Roche discovered ziresovir but in 2014 it chose to offload the RSV fusion inhibitor to ArkBio for clinical development rather than take it forward internally. ArkBio went to deliver phase 1 and 2 data, leading to the initiation of a phase 3 trial at 30 pediatric clinical centers in China in 2020. The study randomized 311 infants hospitalized with RSV infection to receive ziresovir or placebo twice a day for five days.
ArkBio’s study met its primary endpoint, linking ziresovir to a significant reduction on a bronchiolitis sign and symptom score. After two days, the first time point measured, ArkBio saw a 30% reduction in the ziresovir score versus placebo, causing the trial to hit its primary endpoint with a p-value of 0.002. A 55% reduction was seen in children aged under six months.
The top-line results shared by ArkBio cover one secondary endpoint. On Day 5, participants in the ziresovir cohort had a 77% viral load reduction compared with placebo, causing the study to meet that secondary endpoint with a p-value of 0.006. According to ArkBio, statistically significant reductions in viral load were seen throughout the treatment period.
Armed with the results, which ArkBio said include “an excellent safety profile,” the biotech plans to file for approval in its home market of China around the middle of the year. With Roche working on the molecule at its Shanghai site, ArkBio is pitching ziresovir as the first pediatric drug to be discovered and developed in China before expanding to the rest of the world.
How much of an impact ziresovir makes in China and beyond will depend, in part, on the numbers that are missing from its top-line release. ArkBio is yet to post details of the effect of ziresovir on bronchiolitis scores across the full studied timeframe, which extends out to Day 14, or to share any results on several important secondary endpoints.
The study looked at the effect of ziresovir on the length of hospital stay, frequency of ICU admission and length of ICU stay. Those details will influence the value that healthcare systems place on the therapy.
ArkBio’s prospects could also be affected by the impact of RSV vaccines and long-acting antibodies that could reduce the number of infants who are hospitalized with RSV. Sanofi and AstraZeneca have already released phase 3 data on their long-acting antibody nirsevimab, showing it reduced lower respiratory tract infections by 75%, and Pfizer is closing in on data from a phase 3 study of its maternal RSV vaccine.