By Colin Kellaher 



  Roche Holding AG's Genentech unit on Friday said a Phase 3 study of its arthritis drug Actemra met its primary endpoint of reducing the likelihood of the need for mechanical ventilation in hospitalized patients with pneumonia associated with Covid-19. 


  Genentech said patients who received Actemra plus standard of care were 44% less likely to progress to mechanical ventilation or death compared to patients who received placebo plus standard of care. 


  The study showed that the cumulative proportion of patients who progressed to mechanical ventilation or death by day 28 was 12.2% in the Actemra arm, compared with 19.3% in the placebo arm, the company said, adding that there were no new safety signals for the drug. 


  In late July, Genentech said a separate Phase 3 study of Actemra missed its primary endpoint of improved clinical status in adults hospitalized with severe Covid-19 associated pneumonia. 


  Actemra works to suppress the overreaction of a person's immune system by blocking proteins called interleukin-6, which trigger the body's inflammatory response. Researchers believe that the overreaction of the immune system might be causing the most severe damage to Covid-19 patients, and that drugs that stop this response might ease some of the most severe symptoms. 


  Genentech said it plans to share the latest data with the U.S. Food and Drug Administration and other health authorities around the world. 


  --Brianna Abbott contributed to this article. 


  Write to Colin Kellaher at colin.kellaher@wsj.com