Sanofi and Regeneron Pharmaceuticals have reported that a Phase III clinical trial of rheumatoid arthritis drug Kevzara (sarilumab) failed to meet its primary and key secondary endpoints in Covid-19 patients who required mechanical ventilation in the US.

The study compared 400mg dose of the drug plus best supportive care to best supportive care alone.

Minor positive trends were demonstrated in the primary pre-specified analysis group but did not achieve statistical significance. Also, these trends were countered by negative trends in a subgroup of critical patients who were not on mechanical ventilation at baseline.

In the primary analysis arm, adverse events were reported in 80% of patients treated with Kevzara and 77% of those on placebo.

Serious adverse events in at least 3% of patients, more frequent among Kevzara patients, were multi-organ dysfunction syndrome and hypotension.

Based on the data, the companies have halted this US-based trial, including a second cohort of patients who were on a higher 800mg dose of the drug.

The primary analysis involved 194 patients who were critically ill and were on mechanical ventilation at the time of enrolment.

Sanofi and Regeneron designed the Phase III trial based on findings from a small, single-arm study in China involving mostly severe, febrile, hospitalised Covid-19 patients with elevated IL-6 levels.

The study findings indicated that blocking this pathway with the IL-6 blocker tocilizumab rapidly decreased fever and improved oxygenation in severe patients.

In addition to this Kevzara trial, Sanofi is conducting a Phase III study outside of the US in hospitalised patients with severe and critical Covid-19 using a different dosing regimen.

Both the trials are overseen by the same Independent Data Monitoring Committee (IDMC), which recommended that the trial being conducted outside of the US can continue.

Data from the trial outside of the US is expected in the third quarter of this year.