FILE PHOTO: The ultrastructural morphology exhibited by the 2019 Novel Coronavirus (2019-nCoV), which was identified as the cause of an outbreak of respiratory illness first detected in Wuhan, China, is seen in an illustration released by the Centers for Disease Control and Prevention (CDC) in Atlanta, Georgia, U.S. January 29, 2020. Alissa Eckert, MS; Dan Higgins, MAM/CDC/Handout via REUTERS/File Photo

(Reuters) - Sanofi and Regeneron Pharmaceuticals Inc have expanded a clinical trial of their rheumatoid arthritis drug Kevzara as a coronavirus treatment to patients outside the United States.

The companies said enrolments for the mid-to-late stage trial of Kevzara, an immune-system modifying drug known as a monoclonal antibody, have now started in Italy, Spain, Germany, France, Canada, and Russia. The U.S. trials began last week.

The trial, expected to enroll about 300 patients, will recruit hospitalized patients from several countries who are severely or critically ill with COVID-19 infection, a disease caused by the highly contagious coronavirus.

The new coronavirus, called SARS-CoV2, has now infected more than 700,000 people worldwide, and over 30,000 people have died from it, according to a Reuters tally.

Doctors have seen that many of those who become critically ill from SARS-CoV2 are experiencing a so-called cytokine storm, which happens when the immune system overreacts and attacks the body’s organs. Some researchers think drugs that can suppress the immune system, including monoclonal antibodies, might be useful for limiting this autoimmune response.

The United States has the most reported cases of any country in the world, with more than 130,000 cases of COVID-19.

Italy and Spain have been two of the worst-hit countries in Europe, recording the highest and the second highest death toll from coronavirus of any country in the world, respectively.

Regeneron is leading the U.S. trials, while Sanofi is leading trials outside the U.S.