By Joseph Walker 

Regeneron Pharmaceuticals Inc. and Sanofi SA said their arthritis drug Kevzara failed to help Covid-19 patients recover in a U.S. clinical trial.

The failure clouds a class of drugs being studied as potential treatments for Covid-19 patients who experience an abnormal immune response known as "cytokine storm," which researchers and doctors suspect contributes to the deaths of some patients.

The U.S. study of Kevzara was stopped after the drug was shown to be no better than placebo in helping the recovery of critically-ill hospitalized patients, the companies said on Thursday. Patients were considered critical if they were on ventilators, high-flow oxygen or requiring treatment in an intensive care unit.

Among patients on ventilators, 80% of Kevzara patients experienced side effects, compared with 77% of patients receiving placebo, the companies said.

Detailed results from the study will be submitted for publication in a scientific journal, the companies added.

Despite the end of the U.S. study, a Sanofi-led study of Kevzara outside the U.S. will continue on the recommendation of a data monitoring committee overseeing both trials, the companies said. That study is evaluating a different dosing regimen. Results are expected in the third quarter of this year.

In April, Regeneron halted part of the U.S. Kevzara study in hospitalized patients who weren't sick enough to be put on ventilators or receive high-flow oxygen therapy, but received other oxygen support.

Kevzara blocks a cytokine protein known as interleukin-6, or IL-6, which plays a role in triggering the body's immune and inflammatory response. Regeneron and Sanofi started clinical trials of the drug earlier this year after a small Chinese study of another IL-6 blocker, Actemra, showed encouraging results.

Genentech, a unit of Roche Holding AG, is conducting multiple studies of Actemra, including in combination with Gilead Sciences Inc.'s antiviral treatment remdesivir. Unlike Kevzara, Actemra is approved by the U.S. Food and Drug Administration to treat cytokine storm in certain patients.

Write to Joseph Walker at


(END) Dow Jones Newswires

July 02, 2020 18:02 ET (22:02 GMT)

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