The United Kingdom medicines regulator has approved the use of remdesivir, an antiviral drug that is thought to shorten the recovery time for COVID-19 patients.

The drug, which is developed by California-based pharmaceutical company Gilead Sciences, will only be used in adults and adolescents who are hospitalized with severe symptoms of novel coronavirus infection.

Early trials of the drug suggest it can improve the recovery time for patients with severe symptoms of COVID-19 by up to four days.

"This is probably the biggest step forward in the treatment of coronavirus since the crisis began," Health Minister Matt Hancock said at a UK government news conference. "These are very early steps, but we are determined to support the science and back the projects that show promise."

The UK's Medicines and Healthcare products Regulatory Agency, or MHRA, approved the drug under its Early Access to Medicines Scheme, or EAMS.The scheme was created to provide access to promising yet unlicensed drugs for patients with life threatening conditions.

"We are committed to ensuring that patients can have fast access to promising new treatments for COVID-19," said MHRA Chief Executive June Raine. "We will continue to work closely with the Department of Health and Social Care and other healthcare partners on protecting public health in the UK by prioritizing our essential work on clinical trials, access to medicines, and the development of vaccines."

Remdesivir was created in 2009 as a drug to treat hepatitis C. The drug showed limited efficacy against hepatitis, and similarly was ineffective against Ebola virus disease and Marburg virus infections.

However, the drug later showed promising results against several other viruses including coronaviruses.

Remdesivir has been used in several COVID-19 trials since January. Patients given remdesivir had a 31 percent shorter recovery time versus placebo, according to a study in April by the National Institutes of Health, which is an agency of the United States Department of Health.

That trial involved 1,063 hospitalized patients with advanced COVID-19 infection, and the median time to recovery was 11 days for patients on remdesivir, compared with 15 days for those without it.

"This shows fantastic progress," said James Bethell, who is parliamentary Under-Secretary of State for Innovation at the UK Department of Health and Social Care. "As we navigate this unprecedented period, we must be on the front foot of the latest medical advancements, while always ensuring patient safety remains a top priority. The latest, expert scientific advice is at the heart of every decision we make, and we will continue to monitor remdesivir's success in clinical trials across the country to ensure the best results for UK patients."

The drug has also been authorized for emergency use in the US and Japan.