Roche's bid to repurpose its arthritis drug, Actemra, to help patients hospitalized by COVID-19 has failed in a late-stage trial.

The Swiss pharmaceutical company had started the trial, named COVACTA, in March on 330 people, but the drug didn't improve patients' health, Roche said in a statement.

"The COVACTA trial did not meet its primary end-point of improved clinical status in patients with COVID-19-associated pneumonia, or the key secondary end-point of reduced patient mortality," the company confirmed on Wednesday.

Another arthritis drug – Kevzara, produced by Regeneron Pharmaceuticals and Sanofi – had proved ineffective against COVID-19 symptoms earlier this month.

Many existing drugs are being looked at as potential COVID-19 treatments. Antiviral Remdesivir has proved successful at shortening the recovery time of COVID-19 patients, but its efficacy is erratic and the drug needs to be complemented with other treatments.

There was initial hope the anti-malarial drug hydroxychloroquine could treat COVID-19 symptoms and inhibit the virus, but a large trial conducted by Oxford University concluded it had "no beneficial effect in patients hospitalized with COVID-19."

The research for COVID-19 treatments continues as scientists around the world investigate existing drugs and work to develop new ones.

Check out our new six-part podcast series Notes on a Pandemic as CGTN Europe finds out how business, science and people have risen to the challenge of COVID-19.