In March, the UK government announced the funding of two clinical trials testing prophylactic, or disease-preventing, treatments for Covid-19, one in care homes and the other in people with compromised immune systems.
The first is trialling the tapeworm drug niclosamide in immunocompromised patients; specifically those on dialysis treatment, with a kidney transplant, or who have autoimmune conditions that require medicines to suppress the immune system. The trial, called PROTECT-V, is led by Cambridge University researchers who are looking for pre-exposure prophylactic treatments, or PrEP. PrEP works by interfering with viral replication by blocking virus particles from entering the cells, and thus prevents infection. It offers insurance against being infected – like taking blood pressure-lowering tablets to prevent strokes, even though you don’t know whether you’re actually going to get a stroke.
The trial team settled on niclosamide as it’s a drug that’s been approved for years, doesn’t interfere with any of the common medicines that these patients typically take and it can be administered easily via a nasal spray, says Rona Smith, a senior research associate at the University of Cambridge who is leading the study. The drug works by preventing the virus from replicating in the nasal epithelial cells, which are one of the earliest cell types that Sars-CoV-2 tries to take over.
Death rates in people on dialysis have been much higher than the rest throughout the pandemic; one in five dialysis patients who tested positive for the virus died within 14 days in the first wave in the UK. A preventative treatment for these people could be life-saving. These patients don’t tend to mount as good a response to vaccines as healthy people, because their immune systems may not make very many antibodies. A study in organ transplant recipients who had received one dose of a Covid-19 vaccine found only 17 per cent had produced detectable antibodies against the Sars-CoV-2 virus. Many of these patients haven’t been able to leave their house for a year now, save for hospital appointments, Smith says. “What we’re hoping for these patients is that their life could get back to some sense of normality.”
The second trial, called PROTECT-CH, on the other hand, is hunting for another type of preemptive treatment. Referred to as post-exposure prophylaxis, or PEP, it would be taken after being exposed to someone who has tested positive for the virus. While Philip Bath, its lead researcher at the University of Nottingham, can’t say exactly which drugs will be trialled, they will be ones that are already used in the NHS for other conditions.
The trial is targeting care homes, whose residents and their staff have suffered a colossal brunt of the deaths and illness throughout the pandemic; deaths in care homes have made up about a third of all fatalities involving Covid-19 in England and Wales. The biggest challenge in setting up the trial, Bath says, is getting access to care homes, which are often privatised, unlike the NHS system, and they don’t have much of a history of taking part in trials.
Considering at least a fifth of care home staff have not yet had the vaccine, combined with not knowing whether the vaccines work in the very elderly means that these facilities may not be able to afford to rely on vaccines alone. “You don’t want to put all your eggs in one basket,” says Bath. “It’s about trying to offer you another intervention so that if the virus does get into the care home, we can protect people who are particularly at high risk because they’re sitting in the middle of the virus.”