The World Health Organization is testing three more drugs as part of a huge global study to find effective treatments for Covid-19, the agency said on Wednesday.

The study, which will involve researchers in more than 600 hospitals in 52 countries, will evaluate whether the drugs already approved for other uses – one for malaria, one for cancer and one for autoimmune diseases – can reduce the risk of death for patients with Covid to be hospitalized.

Dr. Tedros Adhanom Ghebreyesus, WHO director general, said Wednesday he hoped “one or more of the drugs” would prove effective in treating the virus.

Although there are already some treatments out there for people with Covid-19, including steroids and monoclonal antibodies, Dr. Tedros: “We need more for patients at all ends of the clinical spectrum.”

The first phase of the WHO’s trials of new drugs, which it called Solidarity, yielded disappointing results. The researchers found that four different drugs, including hydroxychloroquine and the antiviral drug remdesivir, had little or no benefit for hospitalized Covid patients.

The three drugs in the new study, named Solidarity Plus, were selected by an independent panel of experts and are donated by their manufacturers Ipca, Novartis and Johnson & Johnson. The drugs are artesunate, an antimalarial drug that may have anti-inflammatory effects; Imatinib, a cancer drug that could reverse damage to the lungs; and infliximab, an autoimmune disease drug that may help curb an overly aggressive immune response to the virus.