Speaking on Wednesday, Bill Anderson, the head of Roche’s pharmaceutical division, told Reuters that it was taking longer than expected to finish their trial. The company’s chairman Christoph Franz had previously indicated results might be available before the end of March.

“There’s just simply not enough patients to enrol… with the speed we were hoping for,” Anderson stated, noting that the UK’s strict lockdown and fast vaccination program had seen infection rates plummet in the country in recent months.

“That’s been one of the challenges since the beginning of the pandemic: you set up sites where there’s a lot of Covid, and then by the time you’re ready to enrol, the pandemic has moved somewhere else and you’re sort of chasing it,” he noted, but did not disclose any candidates for new trial locations.

Roche and Boston-based partner Atea Pharmaceuticals are trialing a pill which could be used as an alternative Covid-19 treatment to expensive antibody cocktails. The medication is being tested on those with mild to moderate symptoms, while there is a separate study for severe cases.

In the UK as of 20 April, the seven-day Covid-19 infection rate had fallen to 26.1 cases per 100,000 people, down from over 350 in January.