Two new reports have produced conflicting results on the potential effectiveness of remdesivir, an experimental antiviral drug considered to be one of the leading hopes in the fight against Covid-19.
Disappointing results emerged from the first gold-standard clinical trial for remdesivir, which found that the drug did not help patients in China with severe Covid-19. Those findings were published in The Lancet medical journal.
On the same day, drugmaker Gilead Sciences announced positive early findings from a US-designed clinical trial being conducted at 180 sites around the world.
Gilead announced that the US trial will show that Covid-19 patients treated earlier with remdesivir had better outcomes than those who received the drug later in the course of their illness.
'Not a very encouraging result'
The trial also will show that people who take remdesivir for five days do as well as patients who take a 10-day course, Gilead said.
Infectious disease experts said they are more encouraged by the US clinical trial – which is being run by the US National Institute for Allergy and Infectious Disease (NIAID) – than they are discouraged by the Chinese trial.
That's because the Chinese team "only enroled half the patients you would need to have a powerful study result" from such a clinical trial, said Dr Aaron Glatt, chairman of medicine and hospital epidemiologist with Mount Sinai South Nassau in Oceanside, New York.
"It would have been great if they had seen evidence it worked, even in the small number of patients they studied," Glatt said. "It's not a very encouraging result, but it's inadequate to say the drug doesn't work."
Dr Amesh Adalja, a senior scholar with the Johns Hopkins Center for Health Security, said the Chinese trial is an "important milestone and allows us to better assess the impact of the drug in a rigorous manner".
However, Adalja added that "the study, because it did not meet its enrolment goals, is underpowered so it is not a definitive result and will need to be supplemented with other trial data.
"For example, the primary end point of the NIAID-designed trial was met and will provide more information on the benefit of the drug," Adalja concluded.
Remdesivir is a broad-spectrum antiviral that has shown promise in fighting many different dangerous viruses, including the Covid-19 coronavirus, MERS and SARS, Gilead said. It is designed to interfere with viral replication.
In the study from China, 237 severely ill patients were randomly chosen to receive either remdesivir or a placebo between 6 February and 12 March at 10 hospitals in Hubei, the province that includes Wuhan. Researchers had aimed to recruit 453 patients, but a steep decline in Covid-19 cases prevented them from reaching that goal.
Those who received remdesivir did not receive any apparent benefit over the placebo, regardless of when treatment started, said the research team led by Dr Bin Cao from China-Japan Friendship Hospital and Capital Medical University in China.
"Our trial found that intravenous remdesivir did not significantly improve the time to clinical improvement, mortality, or time to clearance of virus in patients with serious Covid-19 compared with placebo," the report concluded.
The early results reported Wednesday by Gilead are based on an initial phase of the US-led clinical trial involving 397 patients with severe Covid-19 assigned to receive either five or 10 days of remdesivir. There was no mention of a control or placebo group.
At least half of patients treated with a five-day dose of the drug improved, and more than half were discharged from the hospital within two weeks, Gilead reported.
More than 64% of the patients who received the shorter treatment course were discharged, compared with 54% of the group treated for 10 days.
The trial also showed that people who got the drug soon after they developed symptoms did better than those who got it later.
This matches with what doctors on the front lines have learned regarding Covid-19 treatment, Glatt said – namely, delaying the use of antivirals gives the coronavirus more time to damage the body.
"If we only save antivirals for the patients who have already deteriorated so much, it may not be the virus we're treating anymore. It's the underlying damage, and I'm not sure that any viral treatment is going to make a difference if the lungs are damaged and the immune system cascade has reached a point where you're seeing toxicity," Glatt explained.
Gilead said it will share additional data from the trial in the near future, but did not provide a timeline. The company also expects data by the end of May from a second US trial evaluating the use of remdesivir in patients with moderate Covid-19.
The NIAID trials for remdesivir are expected to eventually enrol around 6 000 Covid-19 patients worldwide, Gilead said.