Remdesivir has little to no effect on Covid-19 patients’ chances of survival, a WHO study on the anti-viral drug has found.

The WHO’s Solidarity clinical trial evaluated four potential medications for Covid-19, including hydroxychloroquine and remdesivir.

Remdesivir was among the first to be used to treat Covid-19, and was recently given to President Donald Trump when he was in hospital.

The company manufacturing the anti-viral drug, Gilead Sciences Inc., rejected the findings of the trial.

In a statement, Gilead said the findings of the study were “inconsistent” with others, and that it was “concerned” that the results have yet to be reviewed.

For the Solidarity clinical trial, the WHO tested the effects four potential treatments – remdesivir, an Ebola drug, was one, but they also looked at malaria drug hydroxychloroquine, auto-immune drug interferon, and the HIV drug combination of lopinavir and ritonavir.

Dexamethasone, a low-cost steroid now widely used on Covid patients in intensive care in many countries, was not included in this study.

The four drugs were tested with 11,266 adult patients in total, across 500 hospitals in more than 30 different countries.

The results, which are yet to be peer-reviewed, suggest that none of these treatments has a substantial effect on mortality or on the length of time spent in hospital, the WHO said on October 15.

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On October 14, WHO chief scientist Soumya Swaminathan said that their trials on hydroxychloroquine and lopinavir/ritonavir were stopped in June because they had already proven ineffective. However, the other trials continued.

The study’s results appear to contradict a previous study from earlier this month, conducted by Gilead, which concluded that treatment with remdesivir cut Covid recovery time by five days compared to patients given a placebo. About 1,000 patients took part in that trial.

Gilead dismissed the findings, saying in a statement: “The emerging (WHO) data appears inconsistent, with more robust evidence from multiple randomized, controlled studies published in peer-reviewed journals validating the clinical benefit of remdesivir.

“We are concerned the data from this open-label global trial has not undergone the rigorous review required to allow for constructive scientific discussion, particularly given the limitations of the trial design.”

Remdesivir was given emergency use authorization in the US from the FDA on May 1and has since been authorized for use in several other countries.