The search for an effective treatment that can dampen the overactive immune systems in patients with COVID-19 continues unsuccessfully. The latest return victim: Roche's (RHHBY 1.64%) Actemra, which failed a phase 3 study in hospitalized patients with severe COVID-19-associated pneumonia.

In severe COVID-19 patients, it isn't the virus that's causing most of the serious symptoms but the overreaction of the patient's immune system that results in autoimmune damage. The same is true -- to a lesser extent -- with autoimmune diseases such as rheumatoid arthritis, so Roche and others figured it was worth trying its rheumatoid arthritis drug, Actemra, in patients with COVID-19.

Unfortunately, the hypothesis didn't pan out. In the primary endpoint, Actemra didn't improve patients' seven-symptom category score by a statistically significant margin compared to placebo. And mortality, one of the key secondary endpoints, also didn't show an effect, with 19.7% of patients taking Actemra dying within four weeks compared to 19.4% of patients taking a placebo.

There was a difference in the time it took for patients to be ready to be discharged from the hospital -- 20 days for Actemra compared to 28 days for placebo -- but since the primary endpoint wasn't met, the data won't be considered statistically significant by regulators.

Doctors in personal protective equipment talking to an elderly patient in a bed

Image source: Getty Images.

The disappointing results follow a smaller study of Actemra by AIFA, Italy's drug-regulation agency, which found the drug didn't help patients with early stage COVID-19. Sanofi (SNY 1.84%) and Regeneron Pharmaceuticals' (REGN 0.37%) Kevzara, which is in the same drug class as Actemra, also failed to show an effect in patients with severe cases of COVID-19.

Nevertheless, Roche is pressing on with two additional ongoing phase 3 studies testing Actemra in COVID-19 patients: a combination study with Gilead Sciences' remdesivir and a study at sites that treat a high proportion of underserved and minority patients.